steps towards an ecology of landscape
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University of Cambridge
Department of Archaeology
Steps towards an Ecology of Landscape:
a Geoarchaeological Approach to the Study of
Anthropogenic Dark Earths in the central Amazon region, Brazil
Manuel Arroyo-Kalin
Girton College
This dissertation is submitted for the degree of Doctor of Philosophy
2008
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DECLARATION This dissertation is the result of my own work and includes nothing which is the outcome of work done in collaboration except where specifically indicated in the text. Excluding cited references, the main text of the dissertation consists of 79,890 words. Manuel Arroyo-Kalin Cambridge, October 2008
ABSTRACT
Steps towards an ecology of landscape: a geoarchaeological approach to the study of
anthropogenic dark earths in the central Amazon region, Brazil Amazonian anthropogenic dark earths constitute an increasingly more important dimension of the archaeological record of the Amazon basin. These anthropogenic soils mark the location of large, abandoned pre-Columbian settlements that were inhabited from around 500 BC until AD 1500. The dissertation examines the archaeological record of the Amazon basin looking for clues about their proximate and ultimate causes. In order to examine proximate causes, a suite of geoarchaeological techniques is used to analyse exemplars from the central Amazon region, the research area of the Central Amazon Project. Among others, the study discusses the contribution of pre-Columbian ash, charcoal, bone and pottery to their composition. It also establishes empirically that the distinction between darker-coloured artefact-laden dark soils (terras pretas) and lighter-coloured, artefact-poor, and less nutrient-enriched brown soils (terras mulatas) reflects a contrast between areas of settlements where houses and refuse middens decomposed vis-à-vis surrounding or adjacent areas in which spatially-restricted, fire-intensive, and amendment-reliant agricultural practices took place. Finally, inter-site variability is related to overall effects of landscape evolutionary dynamics on the soil mantle. As regards the ultimate causes for the widespread appearance of Amazonian anthropogenic dark earths, the dissertation advances a series of arguments that link incipient processes of tree domestication in the early Holocene, the domestication of Manihot esculenta as a two-phase process involving preceramic and ceramic groups, and the intensification of bitter manioc by expanding horticulturists. The dissertation thus offers an archaeological understanding of the Amazonian landscape as a historical ecology modified by the enduring effects of human practices, one in which specific processes of plant domestication over trans-generational time scales have left their enduring marks.
In memoriam Jim Petersen (2005)
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TABLE OF CONTENTS
DECLARATION AND ABSTRACT i LIST OF FIGURES v LIST OF TABLES vii ACKNOWLEDGMENTS viii NOTES ON DATA SOURCES xiii CONVENTIONS xiv
CHAPTER 1: INTRODUCTION .................................................................................................1
1. ANTHROPOGENIC LANDSCAPE TRANSFORMATIONS...............................................................1
2. THE LANDSCAPE OF AMAZONIA............................................................................................3
3. ANTHROPOGENIC LANDSCAPE TRANSFORMATIONS IN AMAZONIA........................................6
4. THIS DISSERTATION ..............................................................................................................8
CHAPTER 2: THE DARK EARTHS OF THE AMAZONIAN FORMATIVE.....................11
1. DEFINITION AND MAIN CHARACTERISTICS ..........................................................................11
2. THEORIES ABOUT PROXIMATE ORIGINS ...............................................................................13
3. ANTHROPOGENIC DARK EARTHS IN PRE-COLUMBIAN HISTORY...........................................14
3.1 The Amazonian Formative: immigrant or indigenous...................................................15
3.2 Pre-Columbian sedentism, social complexity, and Amazonian dark earths..................20
4. FORMATION PROCESSES OF ANTHROPOGENIC DARK EARTHS ..............................................22
4.1 Pedological and archaeological insights ......................................................................22
4.2 Ethnographic insights ...................................................................................................26
5. SUMMARY...........................................................................................................................30
CHAPTER 3: THE ROOTS OF THE AMAZONIAN FORMATIVE....................................31
1. INTRODUCTION ...................................................................................................................31
2. THE LANDSCAPE IS DYNAMIC: A PALAEO-ENVIRONMENTAL BASELINE ...............................32
3. THE ROOTS OF THE AMAZONIAN FORMATIVE .....................................................................38
3.1 First fruits? Colonisation and arboriculture.................................................................38
3.2 Next roots? Anthrosols and the manioc question ..........................................................41
3.3 The Ceramic Archaic ....................................................................................................49
4. REVISITING THE AMAZONIAN FORMATIVE .........................................................................53
4.1 The Tropical Forest Cultures of Amazonia ...................................................................53
4.2 Interaction spheres of the early Formative ...................................................................55
4.3 The Ceramic Formative in the middle and lower Amazon ............................................62
5. SUMMARY...........................................................................................................................68
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CHAPTER 4: THE CENTRAL AMAZON REGION ..............................................................69
1. INTRODUCTION ...................................................................................................................69
2. THE LANDSCAPE OF THE CENTRAL AMAZON REGION ..........................................................69
3. THE ARCHAEOLOGICAL SEQUENCE OF THE CENTRAL AMAZON REGION ..............................73
3.1 Early research in the region..........................................................................................73
3.2 The Central Amazon Project .........................................................................................77
3.2.1 The Archaic in the central Amazon region......................................................................... 77
3.2.2 The ceramic sequence in the central Amazon region ......................................................... 79
3.2.2.1 The Açutuba site ............................................................................................................ 79
3.2.2.2 The Osvaldo site ............................................................................................................ 83
3.2.2.3 The Hatahara site ........................................................................................................... 84
3.2.2.4 The Lago Grande site..................................................................................................... 88
3.2.2.5 The Nova Cidade site..................................................................................................... 91
3.2.2.6 The Lago do Limão and Antônio Galo sites .................................................................. 91
3.2.3 The Negro-Solimões confluence area ................................................................................ 94
4. SUMMARY...........................................................................................................................97
CHAPTER 5: THE GEOARCHAEOLOGY OF AMAZONIAN DARK EARTHS..............98
1. INTRODUCTION ...................................................................................................................98
2. METHODS .........................................................................................................................100
2.1 Sampling......................................................................................................................100
2.2 Micromorphology........................................................................................................100
2.3 Analysis of bulk samples..............................................................................................102
2.4 Measurement of 13C/12C carbon isotopes ....................................................................105
2.5 Radiocarbon dating of microscopic charcoal .............................................................105
3. CASE STUDIES ..................................................................................................................105
4. UNDERSTANDING VARIABILITY: THE MAKE-UP OF ANTHROPOGENIC DARK EARTHS .........109
4.1.1 Horizonation .................................................................................................................... 109
4.1.2 Texture and soil mantle evolution .................................................................................... 111
4.1.3 Anthropogenic inputs ....................................................................................................... 113
4.1.3.1 Heat treated clay and their physico-chemical signatures.............................................. 113
4.1.3.2 Microscopic bone......................................................................................................... 115
4.1.3.3 Microscopic charcoal and soil melanisation ................................................................ 115
4.1.3.4 Plant matter, fresh and ashed ....................................................................................... 117
4.1.4 Summary .......................................................................................................................... 119
5. EXAMINING SITE FORMATION PROCESSES:
THE PEDO-STRATIGRAPHY OF ANTHROPOGENIC DARK EARTHS......................................120
5.1.1 The Hatahara site: settlement soils (Profiles HA-1, HA-3, HA-5, and HA-9) ................. 121
5.1.1.1 Profile HA-9 (background profile)............................................................................... 122
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5.1.1.2 Profile HA-5 (Urns’ unit, terra preta) ......................................................................... 123
5.1.1.3 Profiles HA-1 and HA-3 (Mounds 1 and 2, terras pretas)........................................... 126
5.1.1.3.1 The buried land surfaces under Mounds 1 and 2.................................................. 127
5.1.1.3.2 The overburden of Mounds 1 and 2 ..................................................................... 129
5.1.1.4 Discussion.................................................................................................................... 131
5.1.1.4.1 HA-5 (Urns’ unit) ................................................................................................ 131
5.1.1.4.2 HA-1 and HA-3 (Mounds 1 and 2) ...................................................................... 132
5.1.1.4.3 New radiocarbon evidence for Mound 2 .............................................................. 135
5.1.2 The Lago Grande site: settlement and hinterland soils
(Profiles LG-1, LG-2, LG3 and LG-4) ................................................................... 136
5.1.2.1 Profile LG-3 (Mound 1, terras pretas) ........................................................................ 136
5.1.2.2 Profiles LG-1, LG2 and LG-4 (terras mulatas) ........................................................... 139
5.1.2.3 Discussion.................................................................................................................... 142
5.1.3 The Osvaldo site: settlement soils (Profile OS-1, terras pretas) ...................................... 144
5.1.3.1 Discussion (OS-1)........................................................................................................ 146
5.1.4 The Açutuba site: settlement and hinterland soils (Profiles AC-1, AC-2, AC-2) ............. 148
5.1.4.1 Profile AC-2 (background profile)............................................................................... 148
5.1.4.2 Profile AC-1 (riverfront, sector IA, terra preta) .......................................................... 150
5.1.4.3 Profile AC-3 (Açutuba phase buried soil, terra mulata) .............................................. 154
5.1.4.4 Discussion.................................................................................................................... 156
5.1.4.4.1 AC-1 .................................................................................................................... 156
5.1.4.4.2 AC-3 .................................................................................................................... 157
5.1.5 The Nova Cidade site: settlement soils (Profile NC-1) .................................................... 159
5.1.5.1 Discussion (OS-1)........................................................................................................ 162
5.1.6 The Dona Stella site (Profile DS-1).................................................................................. 163
5.1.6.1 Discussion (DS-1)........................................................................................................ 165
CHAPTER 6: SYNTHESIS.......................................................................................................167
1. THE GEOARCHAEOLOGICAL STUDY...................................................................................167
2. ANTHROPOGENIC LANDSCAPE TRANSFORMATIONS AND DOMESTICATION IN
THE LANDSCAPE OF AMAZONIA.....................................................................................172
3. REFLECTIONS ON THE RESEARCH DESIGN OF THE DISSERTATION ......................................175
4. LANDSCAPE ARCHAEOLOGY, LANDSCAPES LEGACIES
AND LANDSCAPE DOMESTICATION ...............................................................................177
GLOSSARY ..................................................................................................................................180
REFERENCES .............................................................................................................................195
FIGURES, TABLES AND CHARTS 233
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LIST OF FIGURES
Figure 1. Children playing in a pit at the Hatahara site. ......................................................... 234 Figure 2. The Amazon basin................................................................................................... 235 Figure 3. The confluence of the Negro and the Solimões rivers ............................................ 235 Figure 4. A Yuhupdu family collecting forest fruits. ............................................................. 236 Figure 5. Bitter manioc growing in terra preta. ..................................................................... 236 Figure 6. Oxisol profile and monolith of dark earths at Nova Cidade.................................... 237 Figure 7. Wim Sombroek, terras pretas and terras mulatas .................................................. 238 Figure 8. Regions or sites discussed in Chapter 2, Section 3.1. ............................................. 239 Figure 9. Denevan bluff model of riverine settlement............................................................ 240 Figure 10. Models for the formation of dark earths................................................................ 241 Figure 11. Interior of longhouses in northwest Amazonia. .................................................... 242 Figure 12. Palaeo-environmental records discussed in Chapter 3, Section 2.. ....................... 243 Figure 13. Archaeological sites discussed in Chapter 3, Sections 3.1-3.3.............................. 244 Figure 14. Archaeological sites discussed in Chapter 3, Section 4.2.. ................................... 245 Figure 15. Archaeological sites and regions discussed in Chapter 3, 4.3............................... 246 Figure 16. The Negro-Solimões confluence area. .................................................................. 247 Figure 17. Selected sites from the central Amazon region ..................................................... 247 Figure 18. Archaeological sites in the Negro-Solimões confluence area. .............................. 248 Figure 19. Calibrated ages and 3D viewshed for the Dona Stella site.................................... 249 Figure 20. Projectile point from Dona Stella site. .................................................................. 250 Figure 21. The Açutuba site and its subdivisions in 3D. ........................................................ 251 Figure 22. Calibrated age ranges for the Açutuba site............................................................ 252 Figure 23. 3D viewshed of the Açutuba site........................................................................... 253 Figure 24. Calibrated age ranges for the Osvaldo site. ........................................................... 254 Figure 25. 3D viewshed of the Osvaldo site........................................................................... 255 Figure 26. 3D viewshed of the Hatahara site.......................................................................... 256 Figure 27. Calibrated age ranges for the Hatahara site........................................................... 257 Figure 28. Excavations at the Hatahara site: Mound 1 and Urns’ unit. .................................. 258 Figure 29. 3D viewshed of the Lago Grande site. .................................................................. 259 Figure 30. Excavations at the Lago Grande ditch and promontories site. .............................. 260 Figure 31. Calibrated age ranges for the Lago Grande site .................................................... 261 Figure 32. 3D viewshed for the Nova Cidade site.................................................................. 262 Figure 33. 3D viewshe for the Lago do Limão and Antônio Galo sites. ................................ 263 Figure 34. Calibrated age ranges for sites in the Lago do Limão area. .................................. 264 Figure 35. Finished excavations at the Lago do Limão site in 2005 ...................................... 264 Figure 36. Central Amazon Project Late Holocene calibrated age ranges. ............................ 265 Figure 37. Sites examined in the geoarchaeological study. .................................................... 266 Figure 38. Three different geoarchaeological sampling contexts........................................... 267 Figure 39. Three finished thin sections employed in the study .............................................. 268 Figure 40. Image analyses to measure charcoal and soil texture............................................ 269 Figure 41. The Malvern Laser Particle analyser and Molybdenum blue................................ 270 Figure 42. Exposures examined in the geoarchaeological study. ........................................... 271 Figure 43. Selected clayey soil profiles of the Negro-Solimões area . ................................... 272 Figure 44. Selected sandy soil profiles of the Negro-Solimões area ..................................... 273 Figure 45. A “modal” terra preta soil profile: Urns’ unit, Hatahara site ............................... 274 Figure 46. B horizon sediments: micromorphological characteristics.................................... 276 Figure 47. Micromorphology of clayey A horizon of background soil . ................................ 276 Figure 48. Micromorphology pf terra mulata A horizon:. ..................................................... 277 Figure 49. Micromoprhology of terra preta A horizon.......................................................... 277
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Figure 50. Micromorphology of sandy terra preta A and B horizons.................................... 278 Figure 51. Micromorphological observations of pottery. ....................................................... 280 Figure 52. MS and Fe in terras pretas, terras mulatas and background soils........................ 281 Figure 53. Micromorphological observations of bone fragments........................................... 282 Figure 54. P and Ca from A horizon samples of terras pretas. .............................................. 283 Figure 55. Micromorphology of microscopic charcoal. ......................................................... 284 Figure 56 Visual estimates of micro charcoal vis-à-vis measured Co..................................... 285 Figure 57. Selected chemical properties by depth. HA1, AC-1, OS-1, NC-1. ....................... 286 Figure 58. Micromorphology of illuvial clays in terras pretas and terras mulatas. .............. 287 Figure 59. Micromorphology of auto-fluorescent phytoliths ................................................. 287 Figure 60. Mn and MS of selected terra preta A horizon samples. ....................................... 288 Figure 61. The 2006 excavations at the Urns’ Unit, Hatahara................................................ 289 Figure 62. Location of sampling units at the Hatahara site .................................................... 290 Figure 63. Profile HA-9.......................................................................................................... 291 Figure 64. HA-9. Selected physical and chemical properties by depth.................................. 291 Figure 65. Profile HA-5.......................................................................................................... 292 Figure 66. HA-5. Desiccation cracks, illuvial clays B horizon truncation ............................. 293 Figure 67. HA-5. Selected physical and chemical properties by depth. ................................. 294 Figure 68. Profile HA-1.......................................................................................................... 295 Figure 69. Profile HA-3.......................................................................................................... 296 Figure 70. HA-1. Selected physical and chemical properties by depth.................................. 297 Figure 71. Full stratigraphic profile of Mound 1 (Profile HA-1). .......................................... 299 Figure 72. Excavations of Mound 1 in 2002.. ........................................................................ 300 Figure 73. Calibrated radiocarbon dates from Mound 1 at Hatahara. .................................... 301 Figure 74. Mound 2 showing depth of microscopic charcoal dated by 14C............................ 302 Figure 75. Comparison of calibrated ages from Mound 2 and Mound 1................................ 302 Figure 76. The Lago Grande archaeological site.................................................................... 303 Figure 77. LG-3. Selected physical and chemical properties by depth. ................................. 304 Figure 78. Unit 1, Lago Grande (Profile LG-3): photo and profile. ....................................... 305 Figure 79. Profile drawing for Profiles LG-1, LG-2 and LG-4. ............................................. 306 Figure 80. LG-1, LG-2, LG-4. Physical and chemical properties by depth ........................... 309 Figure 81. Plan of the Osvaldo site and photo of sampled profile OS-1 ................................ 310 Figure 82. Profile OS-1 .......................................................................................................... 311 Figure 83. OS-1. Physical and chemical properties by depth................................................. 311 Figure 85. The Açutuba site.................................................................................................... 312 Figure 86. Profile AC-2 .......................................................................................................... 313 Figure 87. AC-2. Physical and chemical properties by depth ................................................ 313 Figure 88. Profile AC-1 .......................................................................................................... 314 Figure 89. AC-1. Physical and chemical properties by depth ................................................ 315 Figure 90. Profile AC-2 .......................................................................................................... 316 Figure 91. AC-3. Physical and chemical properties by depth ................................................ 317 Figure 92. The sandy banks at the Açutuba site ..................................................................... 318 Figure 93. The Nova Cidade site. ........................................................................................... 319 Figure 94. Profile NC-1 .......................................................................................................... 320 Figure 95.Physical and chemical properties by depth ............................................................ 321 Figure 96. The Dona Stella archaeological site ...................................................................... 322 Figure 97. Field research at the Dona Stella Site.................................................................... 323 Figure 98. Profile DS-1 .......................................................................................................... 324 Figure 99. Micromorphology of DS-1.................................................................................... 324 Figure 100. Physical and chemical properties by depth; 13C isotopes. ................................... 325 Figure 101. A model for the development of soils at the Dona Stella site ............................. 326
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List of Tables Table 1. Radiocarbon dates from the Dona Stella site............................................................ 250 Table 2. Radiocarbon dates from the Açutuba site................................................................. 252 Table 3. Radiocarbon dates from the Osvaldo site. ................................................................ 254 Table 4. Radiocarbon dates from the Hatahara site. ............................................................... 257 Table 5. 13C isotopes on human bone, Hatahara. .................................................................. 257 Table 6. Radiocarbon dates from the Lago Grande site. ........................................................ 261 Table 7. AMS dates on shards from Lago do Limão and Antônio Galo. ............................... 264 Table 8. Soil physical and chemical parameters of selected profiles. .................................... 275 Table 9. Micromorphology of selected profiles...................................................................... 279 Table 10. Hatahara 9. Micromorphological characteristics .................................................... 291 Table 11. Hatahara 9. Soil physical and chemical parameters. .............................................. 291 Table 12. Hatahara 5. Micromorphological characteristics .................................................... 292 Table 13. Hatahara 5. Soil physical and chemical parameters. .............................................. 294 Table 14. Hatahara 1. Micromorphological characteristics .................................................... 295 Table 15. Hatahara 3. Micromorphological characteristics .................................................... 296 Table 16. Hatahara 1. Soil physical and chemical parameters. .............................................. 298 Table 17. Hatahara 3. Soil physical and chemical parameters. .............................................. 298 Table 18. New 14C dates on microscopic charcoal for Mound 2........................................... 302 Table 19. Lago Grande 3. Soil physical and chemical parameters......................................... 304 Table 20. Lago Grande 3. Summary of micromorphological characteristics ......................... 304 Table 21. Lago Grande 1. Micromorphological characteristics ............................................. 307 Table 22. Lago Grande 2. Micromorphological characteristics ............................................. 307 Table 23. Lago Grande 4. Micromorphological characteristics ............................................. 307 Table 24. Lago Grande 5. Soil physical and chemical characteristics.................................... 308 Table 25. Lago Grande 1. Soil physical and chemical parameters......................................... 308 Table 26. Lago Grande 2. Soil physical and chemical parameters......................................... 308 Table 27. Lago Grande 4. Soil physical and chemical parameters......................................... 308 Table 28. Osvaldo 1. Soil physical and chemical parameters. ............................................... 311 Table 29. Açutuba 2. Micromorphological characteristics..................................................... 313 Table 30. Açutuba 2. Soil physical and chemical parameters. ............................................... 313 Table 31. Açutuba 1. Soil physical and chemical parameters. ............................................... 314 Table 32. Açutuba 1. Micromorphological characteristics..................................................... 314 Table 33. Açutuba 3. Soil physical and chemical parameters. ............................................... 316 Table 34. Açutuba 3. Micromorphological characteristics..................................................... 316 Table 35. Nova Cidade 1. Soil physical and chemical parameters......................................... 320 Table 36. Nova Cidade 1. Micromorphological characteristics ............................................. 320 Table 37. Dona Stella-1. Micromorphological characteristics ............................................... 324 Table 38. DS- 1. Soil physical and chemical parameters ....................................................... 325
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ACKNOWLEDGEMENTS
Despite obligatory declarations to the contrary (page i) a dissertation about an enormous
landscape involves the help of many people – colleagues, family, friends and others –
dispersed in a geography that is even wider than the Amazon basin. Now finally at the end of
the long road, it is my very great pleasure to hereby greet them and offer many thanks to all of
them. At the Department of Archaeology, University of Cambridge, my gratitude goes first to
my supervisor, Preston Miracle, and my advisor, Charles French. In different ways both
constantly supported this project over the many years it took to reach its completion, offered
their good and experienced advice, patiently read over numerous drafts and hundreds of pages
of Amazonian archaeology and Dark earths, and even gave me books as presents (thank you).
My gratitude is also due to past, present, and affiliated members of the McBurney
Geoarchaeology Lab – Helen Lewis, Melissa Goodman, Karen Milek, Federica Sulas, Andrea
Balbo, Ann-Maria Hart, Miranda Semple, Heejin Lee, Mary Ownby, Clea Payne, Lawrence
Smith, and Judith Bunbury – with whom I have discussed aspects of the geoarchaeological
evidence and shared many good moments. Resident or visiting academic staff at the
Department – Liz DeMarrais, Chris Chippindale, Ezra Zubrow, Paul Sinclair, Marie-Louise
Sørensen, and Robin Boast – are also thanked for different exchanges and overall support
over the years. My gratitude also goes to Jane Woods, David Redhouse, Jessica Rippengal,
Natasha Martindale, Casey Singe, and Julie Boreham, at the Department of Archaeology, and
Steve Boreham and Chris Rolfe, of the Physical Geography Laboratory at the Department of
Geography. Julie and Steve, in particular, provided assistance and expertise crucial to conduct
some of the laboratory analyses reported in the following pages. At the Department of Social
Anthropology, I would like to thank Françoise Barbira-Friedman and Stephen Hugh-Jones,
with whom I have enjoyed good exchanges and pondered long silences about what life in the
Amazon basin must have been like in the past. Finally, with the Cambridge rite of passage still
fresh in my mind, I would like to first thank my colleague and friend Sue Hakenbeck, who
proofed much of the final draft of the dissertation before initial submission. Second, I would
like to offer a big thank you to the examiners of this thesis, Graeme Barker from Cambridge
University and Peter Stahl from Binghamton University. Despite my attempts to make pages
and pages about soil accessible to the non-geoarchaeologist, I know that what I have written is
not the easiest piece to read. I therefore truly appreciate their attention to detail as well as the
sharp and thought-provoking points offered by each at the Viva Voce exam.
My next stop is Brazil, where my first and heartfelt gratitude is extended to Eduardo Góes
Neves, at the Universidade de São Paulo. Edu was the first person to host me during my initial
trip to Brazil, a time (1999) when I knew very little about Amazonia. Apart from good times,
Edu let me rummage through his filing cabinet and copy whatever I felt like copying, an
openness to sharing knowledge that I have never forgotten. Later, in 2002, he accepted my
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offer to conduct a geoarchaeological study of anthropogenic dark earths within the Central
Amazon Project. He thus provided me with a unique opportunity to take my first step into the
vast realm of Amazonian archaeology after a false start working in the upper Negro basin in
2001. Over the years, exchanges of ideas and information with Edu have played an important
part in shaping some of the thoughts presented in this dissertation. We have also shared
complicated moments, not least the assassination of Jim Petersen in 2005. In earnest, I feel
indebted by Edu’s support, generosity, friendship and hospitality (and Dainara’s). I believe
that this PhD would not have come into being had it not been for his openness to
collaboration, and strongly hope that we will continue to work together at full speed in the
years to come. My involvement with the Central Amazon Project, on the other hand, led me to
meet, work with, and exchange ideas with a large cohort of archaeologists, researchers and
field workers, many of whom today I also count among my good friends. Among others they
include the late Jim Petersen, Bob Bartone, Helena Pinto Lima, Fernando Costa, Claide
Moraes, Carlos Augusto da Silva, Levemilson Mendonça, Anne Rapp Py-Daniel, Claudio
Cunha, Raoni Valle, Carla Carneiro, Valdilene Moraes, Tereza Parente, Marcos Brito,
Francisco ‘Pupunha’ Vilaça, Lilian Rebellato, Patrícia Donnati, Juliana Machado, Lucas
Bueno, Mauricio da Paiva, and Ricardo Chirinos. Important lessons were learned and great
moments were had with many: Jim offered many thought-sparks, many laugh-absurds, and
taught me the word Saladoid; Bob showed me the importance of being earnest, made my mind
ponder grave questions, and taught me the power of the shovel; Doutora Macuqinho taught me
about ceramics, passion and friendship, Fernando shared his white sand madness, his musical
acumen, and also his friendship; with Claide, a great archaeologist, let the show roll – lets dig
and discuss some more (same goes for Fernando Osorio); Commander Raoni was my buddy
on a mighty trip, commands all my respect as a human being and as a scholar, and we ready
ourselves for the upper Negro; Carla has offered her friendship and also shown the most
exciting way of socializing archaeology; Anne, the mother of Rafael and silent conspirator of
the skeletal revolution, has also offered her friendship and hospitality … at this rate I will not
finish these acknowledgements. Suffice it to say that over the course of four field seasons in
2002, 2003, 2005 and 2006, the Central Amazon Project provided me with an opportunity to
be part of what is, without a shadow of a doubt, the most exciting and intense archaeological
project I have ever participated in.
Still in Brazil I would like to extend my gratitude to my friend and colleague Renato
Kipnis and his family, which have hosted my stays in Brazil on numerous occasions; to
Charles Clement, with whom discussion continues and collaboration is perhaps only starting;
to Arnaldo Carneiro, who was the first earth scientist in Brazil which heard what the rationale
of my research was about; to Fatima Teles, at the Museu Paraense Emílio Goeldi, who went to
great lengths to help me find references and make my stay in Belem comfortable; to Fabiola
Silva, whose religious fervour no doubt helped the happy arrival of my first samples to the UK
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and who knows what else; to Cristiana Barreto, whom I first met in Cambridge and whose
thought-wavelengths I sometimes parallel; to Edithe Pereira, who was among the first to meet
me in Brazil, generously shared her personal library with me and, recently, invited me to the
incredible Amazonian Archaeology conference in Belém; to Vera Guapindaia, who showed
me the Maraca urns before I knew Maraca urns existed. I would also like to acknowledge the
support provided in 2001 by Instituto SocioAmbiental colleagues Aloisio Cabalazar, Flora
Cabalzar, Beto Ricardo, Geraldo Andrello, the late Jorge Pozzobon, Marta Azevedo, Pieter
van der Veld, and Carlão Souza, as well as my ex-girlfriend Ashley Lebner.
Despite the many good encounters, this dissertation was written in relative intellectual
isolation: no one in Cambridge understood one thing about Amazonian archaeology! No one I
could find understood much about tropical soils either. No one, including myself. Over the
course of the years, therefore, I was forced to cast the widest net of exchanges and it is these
that provided true intellectual lifelines and sources of knowledge. Perhaps the first was a 2002
visit to ISRIC, Wageningen, to study thin sections of antropogenic dark earths. Here I met the
very tall and affable Wim Sombroek, who was kind enough to discuss with me what these
soils where all about, allowed me to borrow those thin sections for study in Cambridge, and
also showed me his collection of orchids. The next was the meeting organised by Johannes
Lehmann, Bruno Glaser, Dirse Kern, and Bill Woods in Manaus, also in 2002. This led me to
meet other memorable students of the Amazon, including the organisers themselves and
Hedinaldo Lima, Laura German, Philip Fearnside, and Charles Mann. Courtesy of this
meeting we not only got the most spectacular views of the Negro river and an initial peek of a
storm in the Tapajós, but also an amazing opportunity to examine different archaeological
sites with anthropogenic dark earths in a variety of different contexts. I particularly cherish
discussing a terra preta profile with Wim Sombroek from a boat in the Tapajós, and getting
from Bill Woods the first of many good pieces of advice, to key my eye into the landscape.
Other settings were equally crucial to expand my horizons in Amazonian archaeology. The
meetings organised by Bill Sillar in London put me in touch with the small but bright
intellectual community of lowland South Americanist archaeologists in this city, including
here especially José Oliver, who once hosted me for a full day of lowland talk and from whom
I obtained copies of the most rare pieces of Amazonian literature; Warwick Bray, who
graciously provided me with a full set of ProCalimas; Costillita Colin McEwan, who always
offered his best wishes for my research; and Liz Graham, who was a great discussant of a
paper I presented in London. Similar remarks can be said about meetings in scholarly contexts
at Montreal (2004), Puerto Rico (2006), and Dublin (2008), at which I finally came to meet a
number of minds interested in the Neotropical lowlands and the Caribbean. Included here are
Stéphen Rostain, who has presented me with very nice surprises between book covers and also
spiked my curiosity about the Guianas; Mike Heckenberger, who told me to never give up and
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whom I hope to see in the Xingú some time soon; mad-man-from-Minessota Morgan Schmidt,
who is writing another dissertation on dark earths that I am sure will rock the boat; Betty
Meggers, who startled me by asking why sedimentation in the Central Amazon was so rapid;
Doyle McKey, who at lightning speed provided excellent comments about my manioc
domestication hypothesis, and Bill Balée, with whom I know we have much more to talk
about. Puerto Rico and Dublin also allowed me to meet others whose scholarship I greatly
respect, such as Richard Cooke, Arie Boomert, Arthur Rostoker, Cristóbal Gnecco, and John
Walker. Montreal led to a visit to Burlington with Jim, Edu and Bob, during which I met John
Crock and Jess Robinson, both good people. Some of the above have been kind enough to
send me copies of their own or others’ work to expand my personal library – many thanks.
When it comes to dark earths, meetings in Stirling (2004), Cambridge (2007), and Dublin
(2008) allowed me to examine at first hand the work that others had done on anthrosols and to
present and discuss my own. I have lasting memories of thin sections shown to me by Donald
Davidson, of conversations with Paul Adderley about particle-sizing methods and anthrosols,
of cross-comparisons and discussion of observations with Yannick Devos, and of inspiring
exchanges with Richard Macphail, Hans Huisman, Wendy Matthews and Tim Beach. This
trajectory is coronated by the session on Geoarchaeology and Dark Earths that Yannick, our
colleague Cristiano Nicosia, and myself recently co-chaired at Dublin: roll on dark anthrosols
in geoarchaeology!
For varied and altogether good reasons, all of the above encounters are unforgivable.
However, it is undoubtedly email which provided the most constant stream of provocation: I
have particularly fond memories of discussions about the Central Amazon Project and the
archaeology of the lowlands with Edu, Claide, Helena, Bob, and Jim; about soils,
anthropogenic or otherwise, with Bill Woods, Hedinaldo Lima, Johannes Lehmann, Bruno
Glaser, Hans Huisman, Richard Macphail, Yannick Devos, Wenceslau Texeira, Donald
Johnson, Peter Buurmam, Michael Thomas (the latter three which I have never met); about
domestication, languages, archaeological distributions, and plants fossils with Charles
Clement, Eduardo Neves, Michael Heckenberger, and Glen Sheppard; about slash and burn
agriculture with Charles Clement, James Fraser, Eduardo Neves, William Denevan, Robert
Carneiro (the latter two whom I have never met). The list could go on but I would just like to
acknowledge that many of these exchanges were involved in shaping some of the thoughts I
present in this dissertation and also express awe at the fact that so many good thoughts have
been formulated in emails! This brief account would be incomplete if I did not mention, first,
other scholars like Dolores Piperno, Per Stenborg, Warren DeBoer, Aad Versteeg, Mark Plew,
Omar Ortiz-Troncoso, Juan Carlos Berrío, and Clark Erickson – most of which I have never
met in person – who sent me copies of their publications and/or responded to my questions
about specific points over email. Second, the many important lessons in archaeology and true
intellectual collaboration that I have learned from collegues who do not work in the
xii
Neotropical lowlands, particularly my friends, some my old professors, Luis Borrero, Donald
Jackson, Victoria Castro, Mauricio Massone, Pedro Cárdenas, Teko Prieto, Flavia Morello,
and Manuel San Román.
The observations presented in this dissertation are the result of doctoral investigations
conducted with the support of Wenner Gren Foundation dissertation fieldwork grant no. 6972
and of the McBurney Geoarchaeology Laboratory, Department of Archaeology, University of
Cambridge. Additional support was also received from Girton College and the Centre for
Latin American Studies, both at the University of Cambridge. Investigations have taken place
within the broader framework of the FAPESP-supported Central Amazon Project (grants
02/02953-7 and 05/60604-3), which apart from providing full logistical support, also covered
the cost of some air tickets to travel to Brazil. Indeed all of the site plans and some of the
profile drawings presented in the dissertation bear the ultimate watermark of Marcos Brito and
have been adapted from project research reports. The support of the UK Natural Environment
Research Council (NERC), Tom Higham (Oxford Radiocarbon Accelerator Unit), and Preston
Miracle (University of Cambridge) to obtain AMS radiocarbon dates on ceramic shards from
two sites, Antônio Galo and Lago do Limão, is gratefully acknowledged. Wayne Rasband
from the NIH provided prompt responses to all of my questions about the ImageJ software.
Gordon Walker, from ALS Chemex, offered helpful responses to question on the ICP-AES
data.
It would not have been possible to write this dissertation without the unflinching support,
strong inspiration, and continuous confidence of both of my parents, Manuel Arroyo and Mary
Kalin. Nor would it have been possible to get this far without the love, care and humour of my
compañera Özlem Biner, who has been through a few with me and patiently awaited what is
undoubtedly a long and difficult coming-into-being. I owe to these three people more than I
can convey in words. My good friends and colleagues José Miguel Tagle, Dina Guseynova,
Sevil Serbes, Almir Koldzic, Özge Biner, Lucy Delap, Clive Lawson, Sue Hakenbeck, Andrea
Balbo, Manuel San Román I, Dave Robinson, Marta Magalhães, Umut Yıldırım, Juanita
Baeza, Lennie Charles, Marjorie Marcel, Miguel Castello, Andreas Vlachos, Stefania Merlo,
Salam Al-Kuntar, Alex Herrera, Nolwazi Mkenazi, Eisuke Tanaka, David Beresford-Jones,
Kevin Lane, Claudia Grimaldo, Daniel Rodríguez, Piotrus Kozak, Valentina Trejo, Harry
Loewenfeldt, Clea Chadmal, Sebastian Kohon and Sa’ad Al-Omari know other, different parts
of the story: hence many thanks to each and every one of them and toasts for friendship.
It is likely that I have forgotten someone that deserves my thank you. It is also possible
that I have misunderstood, misread or undeliberately misrepresented somebody’s research or
ideas. Advanced apologies in either case. As José Saramago writes in A Jangada de Pedra:
xiii
“Thinking carefully there is no beginning to things and persons, everything
that started one day had started before, in order to be true and complete
the history of this sheet of paper - let us take the example closest at hand
- would have to reach back to the beginnings of the world - plural here
being purposely used instead of singular; and even then let us doubt, for
those beginnings beginnings were not, only points of passage, sliding
platforms, poor head is our own, subject to such pulls, admirable head,
despite all, that is capable of madness for all reasons but this.”
I would like to dedicate this dissertation to the memory of Jim Petersen, so stupidly
assassinated in a random day of our lives. I would have wanted Jim to read this dissertation
and I am sure that he would have read it already. I know Jim cherished a good discussion as
much as I do: Jim, I hope we would have disagreed!
NOTES ON DATA SOURCES
Unless otherwise credited in figure captions, all photographs presented in this dissertation
are of my authorship. All excavations shown in photographs were conducted by the Central
Amazon Project. All site plans have been adapted from originals prepared by Marcos Brito for
the Central Amazon Project and are used with permission. Profile drawings for HA-3, HA-9,
AC-1, AC-2, NC-1, DS-1 prepared by me, all others adapted from originals prepared by
Marcos Brito for the Central Amazon Project and used with permission. All 14C dates from
Beta Analytic Inc. were obtained by the Central Amazon Project and are used with
permission. All 14C dates from the Oxford Radiocarbon Unit and Waikato Labs obtained by
me with the support of the Wenner Gren Foundation and NERC. All micromorphological
observations compiled by me. All ICP-AES, Co and Ct data produced by ALS Chemex under
contract with the McBurney Geoarchaeology Lab, Cambridge, and interpreted by me. All pH,
EC, LOI and MS data compiled by me at the Physical Geography Laboratory, Cambridge. The
basemap used in maps of the Amazon basin (also inset in satellite images) is based on a
USG/WWF Hydrosheds image (hydrosheds.cr.usgs.gov/images/hydrosheds_amazon_large.
jpg, accessed 10/04/2008). Vertical satellite imagery are snapshots of the NASA WorldWind
1.4 software or the Google Earth 4.0 software. Tilted viewsheds in Chapter 4 are based on
vertically-exaggerated (x10) Landsat satellite images draped onto the digital elevation model
used by the NASA WorldWind 1.4 software.
xiv
CONVENTIONS USED IN TEXT, FIGURES, TABLES, AND CHARTS
Glossary
The meaning of specialised terms used in the dissertation has been unpacked in a Glossary (page 180). For the most part these consist on earth-science related terms (including geology, geomorphology, pedology, and micromorphology), terms used in Amazonian scholarship (including a number of concepts used to describe Amazonian geoforms), and terms in Portuguese, Spanish, or Nheengatú used to refer to specific objects or substances. In the main text, the first usage of each term is marked as follows: A horizon.
Dates and ages
Unless otherwise indicated, all ages quoted in the text are calibrated radiocarbon years (Intcal 04) using a single standard deviation (66.8%). Both cal year BP and cal years BC are used depending on the age of the context under discussion. For the first half of the Holocene ages are discussed in calibrated years before present and rounded to kilo years (kyr), e.g 14C date 5240 + 40 = cal. 6180-5920 BP = 6.2-5.9 kyr BP. For the next half of the Holocene, evidence is discussed in calibrated years before the Christ era and not generally rounded, e.g. 14C date 2269 + 42 = cal. 400-220 BC. Site, profile and sample designation
Site short-hand names:
HA = Hatahara LG = Lago Grande AC = Açutuba OS = Osvaldo DS = Dona Stella NC= Nova Cidade
Examples of short-hand name usage:
NC = Nova Cidade NC-1 = Profile 1 of the Nova Cidade site NC-1.2 = Profile 1, sample 2 of the Nova Cidade site
Conventions for micromorphology tables
Porosity = % surface area of thin section. Pores: • = channels/ chambers; � = planar voids.
Texture: Based on the US Department of Agriculture standard. The following are used: C= Clay; SC= Sandy clay; LS= Loamy sand; SCL= Sandy clay loam; SL = Sandy loam.
Fine fraction, Silt quartz, Sand quartz = % surface area of solids.
Microartefacts = % of thin section view. Bone and Charcoal = % of the fine mineral fraction of bone and charcoal fragments. Size classes as described below.
Abundance of particulates expressed in relative terms: (•) = marginal; • = rare; •• = common; ••• = frequent; •••• = dominant. Fresh organics: r= roots. n/m = not measured
xv
Light sources: OIL=Oblique incident light; XPL=Cross-polarised light; PPL=Plain polarised light; XPO=XPL with OIL beam; OILx=OIL with low XPL beam; UVL=Ultra violet light. The same abbreviations are used in the text.
Organic staining: L = limpid, 1 = organic punctuations; 2 = lightly stained; 3; medium stained; 4; strongly stained. B-fabric: u=undifferentiated; s=speckled; S=striated S = strial.
Microstructure: Capitals identify the major types: M = matrix-supported fabric (porphyric c/f related distribution) where the fine mineral fraction is made of relatively continuous zones of slightly vughy clayey material; G = grain-supported fabric (enaulic and/or monic c/f related distribution) where the fine mineral fraction is reduced and quartz grains acts as the main skeleton of the soil. Small letters characterise the morphology and organisation of the fine mineral fraction: m = continuous, massive slightly vughy clayey material showing little separation; b = subangular blocks that cannot clearly be associated with faunal action; i = irregular clayey peds that cannot be conclusively interpreted as having a coalesced origin; c = irregular clayey peds that can be interpreted as having an origin in coalesced aggregates; g = granular microstructure made up of <150µm pellets; s = small incipient or relict porphyric clayey peds in a grain-supported matrix; r = grano-oriented clayey braces (<50µm) and small intergrain pellets (<50 µm).
Size classes (Texture, bone, charcoal)
µm <2 2-20 20-63 63-100 100-200
200-500
500-1000
1000-2000
>2000
Class fine
mineral fraction
fine silt
coarse silt
very fine sand
fine sand medium
sand coarse sand
very coarse sand
fine gravel
Colours: colours used in tables are approximations of digital photos to Munsell colours. Tiles were sourced from http://www.xrite.com/ (accessed 21/09/2005):
3/4
3/6
4/2
4/3
4/4
4/6
4/8
5/2
5/3
5/4
5/6
5/8
6/3
6/4
6/6
6/8
7/4
7/6
7/8
8/6
8/8
9/8
10YR
7.5 YR
2.5 YR
Measurements of soil physical and chemical characteristics
Measurements of Aluminium (Al), Barium (Ba), Calcium (Ca), Copper (Cu), Iron (Fe), Potassium (K), Magnesium (Mg), Manganese (Mn), Sodium (Na), Phosphorus (P), Strontium (Sr), and Zinc (Z) are in all cases expressed in ppm. Loss-on-Ignition (LOI), Organic Carbon (Co) and Total Carbon (Ct) are expressed as %w (percentage of weight). Electrical conductivity (EC) is expressed in µs (Microsiemens). Magnetic susceptibility (MS) is expressed in low frequency tesla SI units.
Microphotographs
Each microphotograph is labelled on the bottom right corner. This label shows profile and sample number and light source. A scale bar has been added to the label.
1
Chapter 1
INTRODUCTION
1. ANTHROPOGENIC LANDSCAPE TRANSFORMATIONS
A shift away from the perception of past environments as self-regulating and equilibrium-
seeking systems to which individuals, cultures or populations adapted is now well underway
in archaeology (McGlade 1995; Stahl 1996; Erickson 2000; van der Leeuw and Redman 2002;
Hayashida 2005; Kirch 2005). This shift can be argued to follow from two complementary
understandings. The first is that the nested hierarchies of life and matter that we call
environments are historical entities, i.e. that the dynamic relations which articulate the flux
between and among their abiotic and biotic components both express and are determined by
definitive but non-deterministic trajectories of change, paths whose effects can accumulate
over time (Butzer 1982; Delcourt and Delcourt 1988; Phillips 1999a; Thomas 2001; Balée
2006). The second is that the affordances which particular environments offer to human
communities, i.e. the way in which such environments constrain, structure and enable
particular human lifeways (Figure 1), are not ‘natural givens’ shaped exclusively by broad-
scale processes such as climate change, geomorphic evolution, vegetation cover, etc. Instead,
these affordances – contingent properties of surrounding worlds as they are interacted with –
are in many cases a veritable and enduring effect of specific practices of inhabitation that have
characterised past human livelihoods (Denevan 1966a; Denevan 1992a; Balée 1989, 1994;
Balée and Erickson 2006; Botkin 1990; Stahl 1996; Cronon 1996; Erickson 1995, 2006;
Arroyo-Kalin 2004).
The intersection between these two premises in archaeological thinking is perhaps best
epitomised by a gradual abandonment of the notion of ‘environment’ and by the increasing
popularity of the notion of ‘landscape’ (e.g. Crumley 1994; Tilley 1994; Gosden 1994; Barrett
1999; Layton and Ucko 1999; Ingold 2000; Anschuetz et al. 2001; Stahl 2000; Heckenberger
et al. 2003; Balée and Erickson 2006; Erickson 2006; see also Ashmore 2002; Redman and
Kinzig 2003; Fisher and Feinman 2005). This abandonment signals the rejection of
environment as a kind of external scaffolding for adaptation and its replacement by an
understanding of the material world as a dynamic domain that has been inhabited by human
communities and changed through human inhabitation. Beyond the step forward that this
Chapter 1 2
formulation represents, however, many would agree that the very diversity of views invoked
by the notion of ‘landscape’ makes it difficult to pin down exactly what is meant by the
category itself. Rather than attempt here a precise definition, I think it is important to outline
how landscapes can fit into archaeological accounts or, more specifically, how they fit into the
archaeological account that I attempt in the following pages.
I take the perspective that human niche-building (Laland et al. 2000) is a complex process
that has implied the continued reproduction of symbiotic relations with other species at least
since the early Holocene (Rindos 1984; Lathrap 1984; Harris 1989; Bellwood 2005; Barker
2006; Clement 2006a). In different regions of the planet, this reproduction evolved into
ongoing processes of plant and animal domestication and also instigated modifications of the
physical environment associated with husbandry practices (e.g. Denevan 1966a; Denevan
1992a, 2001; Pape 1970; Limbrey 1975; Davidson and Carter 1998; Davidson and Simpson
1984; Bray et al. 1987; Bray 1991; Sandor 1992; Woods and McCann 1999; Terrell et al.
2003; French 2003). In many cases, these modifications endured beyond years, decades, or
centuries, kick-starting what may be described as divergent – indeed emergent – trajectories of
change in the overall characteristics of the physical environment. These modified trajectories
may be understood as anthropogenic landscape transformations: a shaping of biotic and
abiotic legacies resulting from the intersection between the cumulative effects of human
action, often over trans-generational time scales, and broader processes of landscape
evolution.
Reference to anthropogenic landscape transformations brings together the perspective of
Historical Ecology, which highlights how human communities have creatively, sometimes
positively transformed the surrounding worlds into which subsequent people are born (Posey
1985; Balée 1989, 1998; Balée and Erickson 2006; Crumley 1994; López-Zent 1998; Clement
1999a), and earth-science and ecological approaches, which chart the dynamic character of
landscapes as evolving networks of biotic and abiotic components characterised by self-
organisation, spatially-divergent dynamics, and path-dependence (Phillips 1999a; Phillips
1999b; Thomas 2001). As a formulation, the notion of ‘anthropogenic landscape
transformation’ evidently adopts the anthropocentric pro-position advanced by Historical
Ecology – that the human species is “itself a principal mechanism of change in the natural
world, a mechanism qualitatively as significant as natural selection” (Balée and Erickson
2006:5). However, by focusing attention on the intersection between human action and
landscape evolution, it argues that the “palimpsest of continuous and discontinuous
inhabitation by past and present peoples” (Balée and Erickson 2006:2) has structured bio-
physical entities whose continued existence as anthropogenic legacies unfold within
Chapter 1 3
landscapes whose biotic and abiotic components are in path-dependent flux (e.g. Erickson and
Balée 2006; Mayle et al. 2007).
These remarks provide just enough background to outline the main purpose of this
dissertation: to explore how the study of anthropogenic landscape transformations can
augment our understanding of the human history of a big landscape, the Amazon basin.
2. THE LANDSCAPE OF AMAZONIA
The Amazon basin (Figure 2) comprises the largest tract of land of the tropical lowlands of
northern South America, a terrain that drops from an overall elevation just below 200 m asl at
the Andean piedmont to sea-level elevation some six thousand kilometres away, at the
Atlantic coast. At present it records temperatures that remain above 25°C on a year-round
basis, and year-round precipitation gradients that range between <1000 and 8000 mm. These
gradients reflect the shifting position of the Inter-Tropical Convergence Zone, the South
Atlantic Convergence Zone, and the Atlantic tropical easterlies; the influence of
evapotranspiration from the Amazon rainforest itself; and shifts in local air circulation in
response to relief, vegetation and differences in albedo (Salati and Marques 1984; van der
Hammen and Hooghiemstra 2000; Bush and Silman 2004).
Geological research shows that the terrain of Amazonia originated as a Palaeozoic rift-
valley that formed on an enormous inter-cratonic basin associated with the Archean age
Guiana and Central Brazilian shields. As the Andes emerged, the western half of present-day
Amazonia shifted its drainage from the Pacific to the Caribbean, in turn forming depositional
basins that became infilled with Andean and Archean sediments and even experienced some
marine incursions (Räsänen et al. 1995; Räsänen et al. 1987; Hoorn 1994, 1996; Wesselingh et
al. 2002; Roddaz et al. 2005). Depositional basins of the eastern half of Amazonia also
became infilled with eroded Archean sediments and may have experienced some estuarine
incursions (Rossetti and Netto 2006) but either all Andean sediments were eroded away from
the stratigraphic record or they only accumulated in the floodplain of rivers after a single,
equatorially-aligned, Andes-to-Atlantic drainage – the precursor of today’s Amazon river –
developed at some point between the Miocene and the late Pleistocene (Rossetti et al. 2004a;
Irion et al. 2005; Rossetti et al. 2005).
A partial sense of the size, geography and ecology of the region is gained if its drainage
network is considered. Not only is the Amazon river the biggest river in the world by all
possible measures but some of its tributaries can be considered among the five largest as well
(Latrubesse et al. 2005). Together they drain about 7.5 million km2, i.e. about 40% of South
Chapter 1 4
America, and discharge about one sixth of the fluvial freshwater that reaches the oceans on a
global basis (Irion et al. 1997). Many Amazonian rivers run in channels that appear as large
canyons with respect to the surrounding terrain. Within these channels, the amplitude between
flooding highs and lows is expressed in tens of meters and constitutes one form of
‘seasonality’. However, because flooding results from the combined effects of precipitation in
upstream regions, it is a seasonality progressively less and less synchronised, from west to
east, with dry and wet seasons determined by convective activity.
In Amazonian scholarship, rivers are usefully classified into clear, black, and whitewater
rivers (Moran 1993). Clearwater rivers are limpid streams that drain the weathered Tertiary
plateaus and follow established, often rocky beds with stable banks. Blackwater rivers drain
rainforest- or savannah-covered terrain of Tertiary age but are rich in dark-coloured humic
compounds deriving from the decomposition of organic matter. Whitewater rivers are those
that originate in the Andes, transport copious amounts of suspended sediments of Quaternary
age, and - in places - grade an extensive floodplain known, in Amazonian scholarship, as the
várzea (Figure 3). The resulting riverscapes are inhabited by a highly diverse and abundant
aquatic fauna that includes fish, reptiles and mammals. A broad relation exists between the
density and/or size of this fauna and the sediment load of rivers (a higher biomass is found in
whitewater rivers), the upstream versus downstream position of the water body (fish become
smaller and less abundant upstream), and the flooding regime (there are less fish per
volumetric unit of water during flooding highs).
The other ‘face’ of the Amazon basin is constituted by the terra firme, the terrain that is
never flooded by large rivers. Although an elevation gradient for the most part below 200 m
would suggest that this terrain is flat, the terra firme is in reality characterised by rolling hills
that have been shaped since the Tertiary by a combination of tectonics, peneplanation, and
etchplanation (Bigarella and Ferreira 1985; Clapperton 1993; Thomas 1994). Soils of the terra
firme are therefore ancient and characteristically determined by the effects of tropical
precipitation and temperature conditions on highly- and deeply-weathered Tertiary rocks. The
most common soil types, Oxisols (Sombroek 1966; Richter and Babbar 1991), provide an
illustrative case: they show a deep saprolite at many meters below the surface above which
develops a kaolinitic horizon with gibbsite and hematite nodules; a thick and permeable B
horizon; and a shallow A horizon with low retention of organic matter, acid soil pH, and low
soil nutrient status. The collapse of the argillo-ferric structure of these soils as a consequence
of lateral subsurface flushing, the latter induced by the very dissection of the terrain effected
by rain-fed streamlets or igarapés, shapes a toposequence from clayey Oxisols to sandy
Spodosols that contributes to the concave morphology of hillsides and releases humic
compounds into the drainage network (Chauvel et al. 1987; Tardy and Roquin 1993; Lucas et
Chapter 1 5
al. 1996; Horbe et al. 2004; do Nascimento et al. 2004). Extensive areas of the basin that are
characterised by sandy soils and drained by blackwater rivers are believed to represent an
advanced stage of this process (Dubroeucq and Volkoff 1998).
The vegetation of the terra firme greatly depends on climatic factors – especially total
rainfall, length of the dry season, and temperature (Walsh 1998; Bush et al. 2004a) – as well
as edaphic conditions – soil nutrient status, soil texture, and drainage (Rankin-de-Merona et al.
1990; Laurance et al. 1999). Tropical rainforests cover some 4 to 6 million km2 of the basin.
They occur mostly in regions exposed to climate regimes that include relatively short dry
seasons. It is possible to distinguish between dense aseasonal rainforests, which are associated
with high precipitation and well drained clayey soils; open rainforests, which are associated
with low water tables, poor drainage and/or drier conditions; semi-deciduous or seasonally dry
tropical forests, which are transitional to savannah vegetation; the Amazonian caatinga, an
open forest type characteristic of sandy soils; and gallery forests, linear arboreal expanses that
flank the rivers running though savannah regions. Savannah covers about 3-4% of the Amazon
basin and varies from sedge- and/or grass-dominated treeless landscapes to open parkland
vegetation characterised by patches of woodlands with grass-dominated understories. In
addition to rainforest and savannahs, flooded vegetation is important throughout the region. It
includes flooded forests or igapós, which are highly endemic arboreal formations associated
with abandoned channels and inland water bodies of alluvial origin; swamp vegetation, which
is often characterised by specific palm taxa that grow well on poorly-drained soils; and
mangroves, which occur mostly in tide-sensitive rivers near the mouth of the Amazon. The
abundance and diversity of terrestrial fauna in the Amazon basin – insects, birds, mammals,
reptiles, and amphibians too numerous to be mentioned – vary according to soils, the standing
biomass, and the gradient between open and rainforest vegetation (Prance 1982; Eisenberg
1990; Malcolm 1990).
The landscape of the Amazon basin has been anything but static during the late
Quaternary. As will be discussed in further detail in this dissertation, palaeoecologists argue
that decreases in temperature, atmospheric CO2, and/or precipitation permitted a contraction of
the rainforest around its western core towards the Late Glacial Maximum or LGM (Bush et al.
2004b; Anhuf et al. 2006). Thereafter, the rainforest began to expand and continued to do so at
least until the early millennia of the Holocene. The picture is more complicated after that,
partly because more arid conditions in regions peripheral to the basin during the Holocene
accompany a steadfast resilience of the Amazon rainforest (Mayle et al. 2004; Bush et al.
2007), and partly because sea-level rise and potential anthropogenic influence complicate
interpretations of many palaeo-ecological records (Behling 2002).
Chapter 1 6
3. ANTHROPOGENIC LANDSCAPE TRANSFORMATIONS IN AMAZONIA
The extent to which human communities acted as a significant factor in the evolution of
the biotic and abiotic constituents of the Amazonian landscape has been made increasingly
clear by scientific research over the last few decades. The archaeological record of the basin
evidences a very broad array of forms of pre-Columbian engineering of the landscape.
Included here is the construction of different types of earthworks – ditches, shell mounds,
earth mounds, roads, raised fields, artificial forest islands – which served to colonise, intensify
or develop flooding landscapes rich in aquatic resources; to intensify crop cultivation; and to
implant transportation networks and defensive infrastructures that are associated with
settlements that range in scale from small villages to proto-urban aggregations (Nimuendajú
1952, 2004; Meggers and Evans 1957; Hilbert 1959; Hilbert 1968; Denevan 1963; Denevan
1966a, 1970a; Denevan 2001; Erickson 1980, 2000, 2006; Simões 1981; Roosevelt 1991;
Roosevelt et al. 1991; Perota 1992; Rostain 1994, 1999b; Heckenberger 1998; Heckenberger
et al. 1999; Heckenberger et al. 2003; Heckenberger 2005; Heckenberger et al. 2008; Neves
2000, 2003; Neves 2005, 2008; Pärssinen and Siiriänen 2003; Donatti 2003; Schaan 2004;
Schaan et al. 2008; Walker 2004; Machado 2005; Moraes 2006). Their size, scale and ubiquity
leave little room for doubt that past human communities had an enormous impact on the
morphology of the Amazonian landscape (Denevan 1992a; Cleary 2001; Erickson 2006;
Mann 2008; see Meggers 2003 for a sceptical view).
Different researchers have also identified a very significant number of plant domesticates
that most likely originate in the Amazon basin (Lathrap 1977; Piperno and Pearsall 1998;
Clement 1999b; Pickersgill 2007) and documented, through studies of the plant fossil record,
the time-deep presence of these and others originating beyond the region (Mora 1991; Herrera
et al. 1992b; Piperno and Pearsall 1998; Morcote and Bernal 2001; Bush et al. 2007; Bozarth
et al. 2008; see also Roosevelt 1989b). In addition, a number of studies of resource
management by Amazonian peoples have highlighted practices associated with the
manipulation of plant biodiversity (Balée 1989; Politis 1996; Politis 1999; Clement 2006b;
Clement et al. 2008) that double as subtle yet effective forms of environmental alteration or
disturbance, especially in terms of the spatial distribution of plant stuffs employed by human
communities (Balée 2006). Perhaps the most evident is shifting cultivation (Harris 1971;
Beckerman 1987), not only the basis of most small scale farming in the Amazon basin today
but also a practice entangled with forms of agroforestry and fallow management (Denevan and
Paddoch 1987; van der Hammen 1992; Oliver 2001). These practices have a significant
impact on the heterogeneity of plant and animal species composition over decadal to
centennial scales (Linares 1976; Denevan and Paddoch 1987; Saldarriaga 1994; van der
Hammen and Rodríguez 1996; Denevan 2001). Other practices have been elucidated by
studies of human groups ranging from tropical rainforest foragers to small-scale
Chapter 1 7
agriculturalists; they include the clearance of vegetation for settlements, the emplacement of
doorstep orchards or ‘house gardens,’ the deliberate plantation and transplantation of
foodstuffs in natural and human-made forest gaps and old settlements, and the promotion,
tending and/or harvesting of clumps of edible and useful plant species (Figure 4),
domesticated or otherwise (e.g. Lathrap 1977; Posey 1985; Balée 1989; Anderson and Posey
1989; Denevan and Paddoch 1987; Hecht and Posey 1989; van der Hammen 1992; Balée
1994; Rival 1998; Politis 1999).
From an archaeological point of view, perhaps most significant is the fact that forms of
landscape transformation associated with the manipulation of plant biodiversity have resulted
in enduring or resilient changes to the distribution of biotic constituents of the Amazonian
landscape. Balée proposes that well over fifteen percent of the region’s rainforests include
plant species that reflect past human disturbance. He offers provocative remarks about their
historical significance: “If we consider disturbance indicator trees and liana forests to be
archaeological resources, the infrastructures of [ethnographic] Arawete and Asurini societies
thrive (…) on the living artefacts of long-extinct cultures” (1989:13). These thoughts not only
underscore that part of the vegetation of the Amazon basin is an anthropogenic legacy but also
query the extent to which particular locales within the Amazonian landscape were employed
for the intensification of yields derived from specific biotic components (Lathrap 1977;
Clement 1989, 2006a; Piperno and Pearsall 1998; Morcote and Bernal 2001; Pickersgill
2007), that is, were crucially transformed in ways which enabled the reproduction of
symbiotic relations with domesticated plants in the landscape (Balée 1994; Rival 1998;
Clement 1999a; Erickson 2000, 2006).
This brings us to consider a form of anthropogenic landscape transformation that is at the
core of this dissertation: anthropogenic soils or anthrosols. By definition, these are soils whose
formation and characteristics have been enduringly influenced by the material effects of
human action (Limbrey 1975; Eidt 1984; Woods 2003). In the Amazon basin the best known
cases are soils known as terras pretas and terras mulatas. Terras pretas are circumscribed
expanses of dark-coloured and chemically-enhanced soils that signal the location of densely-
occupied pre-Columbian settlements. They are believed to have formed as a consequence of
the concentration of organic inputs – excrements, bone, organic matter, and combustion
residues – related to kitchen middens, house gardens, dwelling structures, and pre-Columbian
settlements. Decomposed or broken down in the soil, these inputs altered the pedogenetic
pathways of parts of the soil mantle by increasing the ubiquity of sorption sites for metals,
raising soil pH, and fomenting the formation of stable organo-mineral complexes rich in
desirable agricultural nutrients (Sombroek 1966; Smith 1980; Glaser et al. 2000; Lima et al.
2002). Terras mulatas are less chemically-enhanced soils that in some cases surround patches
Chapter 1 8
of terras pretas. They have been interpreted as former outfields associated with the
settlements signalled by terras pretas. Collectively, terras pretas and terras mulatas are
known as Amazonian anthropogenic dark earths.
Amazonian anthropogenic dark earths are prized to this day by farmers (Figure 5) because
they achieve higher yields of staple lowlands cultivars such as manioc (Fraser et al. 2008;
Fraser and Clement 2008), permit the growth of acid-intolerant crops such as maize (Balée
1989; Miller 1992a; Heckenberger 1998), and concentrate a high diversity of edible/useful
fruit trees (Balée 1989; Miller 1992a; Clement et al. 2003). They have also acquired singular
importance in Amazonian historical, archaeological and anthropological scholarship because
their presence alongside the main waterways of the basin seems to corroborate 16th century
AD accounts of sedentary, demographically-dense and organizationally-complex societies
(Smith 1980; Denevan 1996; Heckenberger et al. 1999; Myers et al. 2003). As I discuss in
further detail in the following chapter, their study also intersects with long-standing
discussions about the capacity of Amazonia to sustain large populations (Denevan 1966b;
Carneiro 1970; Lathrap 1970b; Meggers 1971; Myers 1973; Gross 1975; Smith 1980; Herrera
et al. 1992c; Myers 1992; see Stahl 2002 for a comprehensive review).
4. THIS DISSERTATION
The preceding paragraphs touch upon some of the topics that are examined in this
dissertation and provide a background to introduce its two main goals. The first is to ascertain
the character and time-depth of human practices that have resulted in anthropogenic landscape
transformations in the Amazon basin. The second is to examine the formation processes and
variability of anthropogenic dark earths in the Negro-Solimões confluence area. Fulfilment of
the first goal demonstrates the importance of anthropogenic landscape transformations during
the pre-Columbian history of the Amazon basin, especially as they relate to different processes
of plant domestication and the formation of anthropogenic dark earths. Fulfilment of the
second goal supplements understandings of the archaeological record of the Negro-Solimões
region and draws insights that are applicable to a more detailed comprehension of the role and
characteristics of these soils in the Amazon basin. Whilst these goals are for the most part
pursued independently, they are actually deeply intertwined: the dissertation aims to establish
the ultimate and proximate causes for the emergence of anthropogenic dark earths in the
Amazon basin.
A brief overview of the dissertation is in order: Chapter 2 introduces and defines the object
of study: it summarises present knowledge about the variability of anthropogenic dark earths,
discusses the changing role which these soils have had in archaeological discussions, and
Chapter 1 9
examines archaeological and ethnographic insights – including here my own ethnographic
observations – that elucidate aspects and offer hypotheses about the formation processes of
terras pretas and terras mulatas.
Chapter 3 offers interpretative reviews of the palaeo-ecological and archaeological
literature of the Amazon basin. These reviews examine the antiquity and character of
anthropogenic landscape transformations in the region, assess their importance in the context
of the Amazonian Formative, and frame a discussion of specific processes of crop
domestication and intensification. This review distils how I understand patterns of landscape
change and the cultural history of the Amazon basin, provides an essential background for
discussions presented in Chapters 4 and 5, and offers a series of arguments that I revisit in
Chapter 6.
Chapter 4 examines the archaeological record of the central Amazon region. This is the
study area of the Central Amazon Project, a research initiative within which I have developed
the investigations presented in this dissertation. The Central Amazon Project has produced the
most detailed and best studied archaeological sequence for the whole of the Amazon region
(Heckenberger et al. 1999; Petersen et al. 2001; Petersen et al. 2004; Neves 2001, 2003; Neves
2005; Neves and Petersen 2006; Costa 2002; Lima 2003; Lima et al. 2006; Donatti 2003;
Moraes 2006; Machado 2005; Arroyo-Kalin 2006; Rebellato 2007; Chirinos 2007). Like any
archaeological sequence, however, this one deserves to be examined in some detail: the
chapter first discusses archaeological understandings of the region as a whole and next
examines in some depth present knowledge about specific sites located in the confluence area
of the Negro and Solimões rivers. This site-by-site focus reconstructs the inferential routes
involved in the interpretation of the regional archaeological sequence and contextualises each
of the specific expanses of anthropogenic soils analysed in Chapter 5.
Chapter 5 presents the premises, questions, methods, data and interpretations of the
geoarchaeological study of archaeological sites from the Negro-Solimões confluence area. The
results are divided into two sections. A first section introduces the reader to the primary
dataset by discussing the relationship between microscopic remains observed in thin sections
and physical and chemical measurements on correlative soil samples. This discussion
specifically angles on the modal variability of anthropogenic dark earths, provides a detailed
account of their effective makeup, discusses their formation processes, and highlights the
effects which broader processes of landscape evolution have had on their measurable
characteristics. With this background in place, the second section combines understandings of
sedimentary and pedological processes – what I call a pedo-stratigraphic perspective – to
discuss field stratigraphic observations, soil physical and chemical data, and existing site
Chapter 1 10
evidence (phases, radiocarbon dates, and broader regional understandings) at each of the soil
exposures sampled in the study. The collection of analyses leads to novel archaeological
interpretations of specific sites, identifies further insights about the formation processes of
these soils, and poses new questions which can be examined by future research.
Chapter 6 synthesises the main observations and findings of the dissertation. The chapter
is divided into four parts. A first section summarises the main lessons of the geoarchaeological
study presented in Chapter 5. A second section retraces steps to some of the arguments
developed in Chapter 3 in order to postulate that the historical emergence of anthropogenic
dark earths tracks the onset of specific process of plant domestication and intensification in the
Amazon basin. A third section briefly discusses how the research design of this dissertation
could be improved by considering other types of environmental data and, hence, outlines the
need for a broader archaeological approach to the landscape. A fourth section offers a few
remarks about wider issues related to landscapes, historical ecology, and domestication.
Some readers might miss a separate treatment of the theoretical considerations that
underpin the research presented in the following chapters. Not only do I consider that a single
chapter or section so devoted would become a laborious transcription of formulations more
competently articulated in recent overviews (e.g. Stahl 1996; Balée 2006; Balée and Erickson
2006; Erickson 2006) but the fact that many attractive theoretical propositions are ‘home-
grown’, i.e. are endemic to Amazonian scholarship, means that they are important both for
their supporting data and theoretical acumen in the context of the dissertation. For this reason I
discuss these propositions as necessary, i.e. where and when the dissertation draws upon them
as building blocks for specific arguments.
11
Chapter 2
THE DARK EARTHS OF THE AMAZONIAN FORMATIVE
1. DEFINITION AND MAIN CHARACTERISTICS
Amazonian anthropogenic dark earths collectively refer to circumscribed expanses of
organically-enriched mineral soils found mostly within the non-flooding terrain of the
Amazon basin. They were first described in Brazil as ‘Terra Preta de Índio’ (Indian Black
Earth) or simply as ‘Terras pretas’ (Black Earths), the reference to ‘Indians’ reflecting the
presence of abundant pottery shards of evident pre-Columbian age on the surface of most
known exemplars. Although these remains signal that expanses of anthropogenic dark earths
are archaeological sites, many of these patches have been used for cultivation at least since the
19th century (Myers et al. 2003). To this day farmers recognise their enhanced fertility and
report both higher yields and longer cropping periods than soils located in the immediate
vicinity (Sombroek 1966; Smith 1980; Woods and McCann 1999; McCann et al. 2001;
German 2001, 2003; Hiraoka et al. 2003; Fraser et al. 2008).
Expanses of dark earths vary in size, shape and location (Smith 1980; Kern et al. 2003;
Neves 2005): linear expanses have been reported as patches extending over hundreds to
thousands of metres along terra firme bluffs that overlook the major waterways of the basin
(e.g. Nimuendajú 1952; Sombroek 1966; Hilbert 1968; Hilbert and Hilbert 1980; Smith 1980;
Eden et al. 1984; Mora 1991; Miller 1992a; Miller 1999; Denevan 1996; Heckenberger et al.
1999; Kern et al. 2003; Myers 2004; Heckenberger 2005; Neves and Petersen 2006).
However, smaller patches, either oval in shape or draping the horizontal surface of the
landform on which they are located, also exist on relict floodplain locations, on terra firme
areas adjacent to alluvial lakes and flooding forest, and on terra firme interfluvial terrain away
from large rivers (Smith 1980; Simões and Araujo-Costa 1987; Simões and Machado 1987;
Miller 1992a; Woods 1995; Kern 1996; Neves and Bartone 1998; Sternberg 1998; Vacher et
al. 1998; Woods and McCann 1999; Donatti 2003; Coomes 2004; Zimmerman and Oyuela-
Caycedo 2006; Moraes 2006). Soil horizons with at least incipiently similar characteristics are
reported to have formed on both shell middens and artificially constructed mounds at flooding
landscapes of the Amazon basin and beyond (Hartt 1885; Meggers and Evans 1957; Evans
and Meggers 1960; Versteeg 1985; Versteeg 2003b; Roosevelt 1991; Rostain 1994; Schaan
2004; Walker 2004).
Chapter 2. The Dark Earths 12
Anthropogenic dark earths are characterised by a generally darker (grey, brown, or ink
black in colour) and deeper (not infrequently reaching down to 60 cm) A horizon that stands
in sharp contrast to the more shallow ones observed in neighbouring soils (compare the left
and right photographs shown in Figure 6) (Sombroek 1966; Smith 1980; Woods 1995; Kämpf
et al. 2003). As pointed out in Chapter 1, studies distinguish between terras pretas, i.e.
pottery-rich black soils with a deep A horizon, and terras mulatas, larger surrounding or
adjacent expanses of darkened soils whose surface horizon lacks archaeological artefacts but
whose nutrient status is intermediate between terras pretas and the broader soilscape
(Sombroek 1966). Most scholars consider this contrast to reflect a distinction between
sedentary pre-Columbian settlements and associated outfields (Andrade 1986, 1988; Woods
and McCann 1999; McCann et al. 2001; Hecht 2003; Denevan 2004)
The vast majority of studies of anthropogenic dark earths – in most cases of terras pretas
– demonstrate that A horizon sediments show a higher cation exchange capacity, more basic
pH, and higher concentrations of organic carbon, calcium, phosphorus, manganese, potassium,
barium, copper, manganese, strontium, and zinc than both the sediments that make up the
underlying B horizon and comparable adjacent soils (Klinge 1962; Sombroek 1966; Smith
1980; Herrera et al. 1980-1; Eden et al. 1984; Andrade 1986; Mora 1991; Kern and Kämpf
1989; Kern 1996; Kern et al. 2004; Pabst 1985; Pabst 1991; Pabst 1993; Heckenberger 1998;
Heckenberger et al. 1999; Glaser 1999; Woods and McCann 1999; McCann et al. 2001; Lima
et al. 2002; Schaefer et al. 2004; Ruivo et al. 2003; Lehmann et al. 2004; Liang et al. 2006).
Research shows that these soils occlude between four and thirty-five times more pyrogenic
carbon than adjacent Oxisols, an observation marshalled to suggest that black carbon is key to
high organic matter retention (Glaser et al. 2003). Micromorphological studies also ascertain
the ubiquitous presence of microscopic charcoal (i.e. pyrogenic carbon, the most common
form of black carbon), bone, and pottery fragments as common particulate inputs in these soils
(Lima 2001; Lima et al. 2002; Texeira and Martins 2003; Schaefer et al. 2004; Arroyo-Kalin
et al. 2004; Costa et al. 2004b,2004a).
Whilst much recent literature has emphasised the unique Amazonian character of these
soils (Lehmann et al. 2003; Glaser and Woods 2004), archaeological investigations show that
similar anthropogenic modifications are found beyond the Amazon basin, for instance in the
north of Colombia (Angulo Valdés; Aceituno and Castillo; Oyuela-Caycedo and Bonzani;
Castillo and Aceituno 2006), in the Orinoco basin (Cruxent and Rouse 1958; Barse 1989;
Roosevelt 1997b; Zucchi 1999; Oliver 2008), in the Guianas (Vacher et al. 1998), and in
subtropical areas south of the Amazon basin proper (Prous 1991a). This has led some to
propose the need to reconsider the distribution of anthropically-enriched dark soils of pre-
Chapter 2. The Dark Earths 13
Columbian origin within the broader geographical context of the Neotropics (Graham 2006).
Even casual perusal of studies from further afield (e.g. Pape 1970; Macphail 1981; Macphail
1994; Macphail et al. 2003; Davidson and Simpson 1984; Yule 1990; Simpson 1997; Simpson
et al. 1998; Blume and Leinweber 2004; Cammas 2004; Galinié 2004; Loveluck 2004;
Heimdahl 2005; Nicosia 2006), highlights that darkened anthropogenic horizons have been
linked to a very broad variety of situations, i.e. underscores the need to examine dark earth
formation processes with attention to historical regional specificities.
2. THEORIES ABOUT PROXIMATE ORIGINS
An anthropic origin for Amazonian dark earths was advocated in the first descriptions of
these soils by scientific observers of the 19th century: pioneering geologists like Smith (1879)
and Hartt (1871; 1885) unhesitatingly related cultivation patches along the lower reaches of
the Amazon river (hereinafter referred to as the lower Amazon) to villages of former
indigenous peoples (see also Woods 1995; Myers et al. 2003). The results of the first soil
chemistry analyses conducted on them allowed Katzer (1903) to argue that their high fertility
was the result of unusual concentrations of charcoal and decomposed organics in the fine earth
fraction, properties which he argued had also made them attractive to farmers in the past.
Based on an archaeological survey of the Santarém area conducted in the early 1920s,
ethnologist/archaeologist Nimuendajú (1952; 2004; Palmatary 1960; Neves 2004) suggested
that both their geographical distribution and associated archaeological remains, earthworks
and roads indicated they had originated in densely-populated, sedentary pre-Columbian
settlements.
For the first part of the 20th century, however, these opinions remained isolated. The size
of farmed expanses in the Brazilian Amazon, the fact that many local farmers did not
recognise their human-made origin, a lack of evidence for their contemporary formation, and
the scant attention accorded to them by important Amazonian archaeologists (e.g. Meggers
and Evans 1957; Evans et al. 1959; Evans and Meggers 1960; Evans and Meggers 1968, see
below), led some researchers to advocate a variety of ‘geogenic’ models about their origin. In
broad outline these models argue that Amazonian dark earths are patches of fertile soils that
have formed as a result of localised, non-anthropogenic accumulations of organic and/or
mineral materials. These patches would have attracted people for inhabitation and/or farming
purposes during pre-Columbian times, in turn prompting the formation of archaeological sites.
Among the main proponents of such views were Camargo (1941), who argued dark earths
resulted from the in situ accumulation of volcanic ash; archaeologist Barbosa de Faria (1944),
who pointed to the weathering of volcanic rocks as the main source of nutrients; Cunha
Franco (1962), who proposed that organic material and habitation debris had accumulated in
Chapter 2. The Dark Earths 14
water-filled depressions that had later dried out; and Falesi (1974), who argued that deep
profiles and high phosphorus concentrations were the result of the accumulation of Tertiary
alluvial/lacustrian sediments and animal fossil remains.
Although Nimuendajú’s archaeological research remained unpublished and, more
significantly, beyond the intellectual web of earth scientists until the mid 1960s, Katzer’s
(1903; 1944) early suggestion of anthropic inputs prompted further research by Klinge (1962),
who argued that the incomparably higher total and soluble phosphoric acid concentrations of
dark earths clearly evidenced an anthropogenic origin. In parallel, Hilbert’s (1955; 1968)
archaeological research documented the co-occurrence of dark earths and ceramic
archaeological remains along the main rivers of the western half of the Brazilian Amazon,
noted their formation on both haematite and goethite-rich Oxisols (Red and Yellow Latosols
in the Brazilian soil classification), and followed the steps of Nimuendajú in suggesting an
origin in long-lasting settlements. However, it was undoubtedly Sombroek’s (1966)
interpretation of the physico-chemical characteristics measured in artefact-rich dark earths
located on the Belterra plateau, near Santarém, that convincingly refuted geogenic models for
their origin. Sombroek pointed out that the overall topography and drainage of the plateau
were incompatible with suggestions of that organic material had accumulated in small water
bodies. He next noted that instead of the random distribution which would be expected from a
natural phenomenon, the position of dark earth expanses in the landscape suggested deliberate
selection of areas suitable for the invigilation of navigable waterways. He then reported
particle size and x-ray diffraction data which evidenced the same overall texture and kaolinitic
parent material in terras pretas and neighbouring soils, effectively overruling a source in
volcanic debris. Finally, he enunciated the distinction between terras pretas and terras
mulatas and presented distributional evidence that expanses of the former were often
associated with much larger surrounding or adjacent areas of the latter (Figure 7). Most
scholars who have read Sombroek’s confident arguments would agree that he settled the
matter of anthropogenic origins vis-à-vis geogenic origins for good. His research also became
a key intellectual referent for the first systematic survey of anthropogenic dark earths in the
Brazilian Amazon (Smith 1980) and for pioneering pedo-archaeological investigations in the
Colombian Amazon (Herrera et al. 1980-1; Herrera 1981; Eden et al. 1984; Andrade 1986)
during the 1970s.
3. ANTHROPOGENIC DARK EARTHS IN PRE-COLUMBIAN HISTORY
Whilst Sombroek’s (1966) work inaugurated the modern era of studies about Amazonian
anthropogenic dark earths, and even though some archaeological investigations had recorded
the presence of these soils in excavations and surveys (see Palmatary 1960; Neves 2004 on
Chapter 2. The Dark Earths 15
Nimuendajú; also Barbosa de Faria 1944; Hilbert 1955; Hilbert 1968), discussions about
Amazonian pre-Columbian history did not initially take stock of their presence or ultimate
significance. This lack of attention was not trivial: although some researchers argued that the
agricultural aptitude of Amazonian terra firme soils was not per se low (Carneiro 1961;
Denevan 1966b) nor necessarily unchanging (Carneiro 1983; cf. Roosevelt 1980), the main
arguments about the emergence of sedentism in the region were formulated in relative
ignorance of (Lathrap 1970a) or militant disregard about (Meggers 1954; Meggers 1971) the
possibility that the terra firme soilscape had been transformed during pre-Columbian times.
Below I review this intricate intellectual history in order to examine how models of pre-
Columbian history were misshaped; I then outline how the recognition of Amazonian
anthropogenic dark earths has impacted discussions about sedentary and socially-complex
societies in the region.
3.1 The Amazonian Formative: immigrant or indigenous
Modern scholarship about pre-Columbian sedentism in Amazonia begins with the
publication of the ‘Handbook of South American Indians’ in the late 1940s. Convinced about
the hostility of the environment for the development of large and stratified societies, Steward
(1948a), the main editor of the Handbook, dismissed a number of 16th century ethnohistorical
sources which reported the presence of large indigenous settlements along the Amazon river.
Instead Tropical Forest Cultures of the ethnographic record of eastern Amazonia and the
Guianas – groups characterised by a laundry list that includes small populations, canoes,
shifting cultivation of root-crops, village-based political authority, and hammocks (Lowie
1948) – were considered to be accurate reflections of societies that had existed prior to the
European colonisation of the region. These societies contrasted with smaller and more mobile
hunter-gatherer groups of the western half of the region, which Metraux (1948) underplayed
(Myers 1974) and Steward (1948a) christened as the Marginal groups. The fact that the latter
were mostly represented by linguistic isolates of western Amazonia whilst Tropical Forest
Cultures generally spoke languages that could be classified into some of its largest linguistic
families encouraged an account about their co-existence that emphasised different origins.
Steward proposed that the spatial distribution of Tropical Forest Cultures and Marginals
was an outcome of the pre-Columbian immigration of horticulturists into a region inhabited by
hunter-gatherers since earlier times. This immigration had its place in a broader model for the
appearance of sedentary lifestyles in the Americas that contrasted Formative centres at which
sedentism, agriculture, and civilisation had emerged with peripheral areas into which budding
migrant groups from Formative centres had expanded. When it came to the lowlands of
northern South America, his account argued that ‘Formative-level’ groups had expanded from
the western half of the continent (the Andes) into the Colombian lowlands and Venezuela,
Chapter 2. The Dark Earths 16
encountering progressively more difficult environmental limitations. These limitations had
whittled away techno-economic and socio-political elaboration from the immigrants’ cultures
which then had come to resemble the Circum-Caribbean chiefdoms reported in 16th century
sources (which, unlike the Amazonian ones, he obviously did credit). As these groups
continued to expand into the more hostile conditions of the Guianas and Amazonia, they had
simplified further to small village-based societies that relied principally on slash and burn
agriculture of root crops, the Tropical Forest Culture. Their distribution within the Amazon
basin, therefore, suggested an upstream movement of horticulturists from east to west, one that
had successfully colonised riparian areas adjacent to the main waterways, but whose
expansion beyond the riverscape had been checked as much by the resistance of ‘Marginal’
hunter-gatherers as by inherent limitations of the environment.
Although some aspects of Steward’s account were criticised very early on (Rouse 1953;
see also Lévi-Strauss 1952), pioneering Amazonian archaeologists Meggers and Evans
staunchly defended and expanded many of its principal arguments. Strongly influenced by
Steward, they similarly doubted the veracity of contact-time ethnohistorical accounts for the
Amazon basin, regarded the region as a generally hostile environment for human inhabitation,
and considered groups who relied on shifting agriculture – the mainstay of Tropical Forest
Cultures – as destined to shift residence after a generation or two due to soil exhaustion. These
premises were variously formalised as first principles (Meggers 1954); applied to interpret
archaeological evidence from Amapá, Marajó Island and what was then British Guiana
(Meggers and Evans 1957; Meggers and Evans 1958; Evans and Meggers 1960); and also
used to classify into four horizons the ceramic complexes of the Amazon basin that were then
known (Meggers and Evans 1961). Three of them, the Zone-Hachured, Incised-Rim, and
Incised-and-Punctuate horizons, were interpreted as evidence of root crop horticulturists
expanding into the region through the river network; the fourth, the Polychrome horizon, to
which were associated lavishly-decorated Marajoara phase pottery and artificial mounds at
Marajó Island, was interpreted as evidence for a socially-complex Andean offshoot that had
rapidly reached the mouth of the Amazon and then experienced simplification due to harsh
environmental conditions (Figure 8 shows the location of sites and regions mentioned in this
and the following section). The most evident corollary of these interpretations was that
sedentism in the Amazon basin had been strongly arrested by the hostile characteristics of the
physical environment, not least its soils, for agricultural production (Meggers 1954).
Many shortcomings of the four-horizon model were flagged up by archaeological research
over the next 20 years. Evidence for the antiquity of Incised-Rim pottery at the Saladero and
Barrancas sites of the lower Orinoco, and the Malambo site of the Colombian Caribbean
littoral suggested that the time-depth of root crop horticulture in the Amazon basin needed to
Chapter 2. The Dark Earths 17
be decoupled from agricultural innovations in the Andean highlands (Cruxent and Rouse
1958; Rouse and Cruxent 1963; Angulo Valdés 1962, 1981; Reichel-Dolmatoff 1965;
Reichel-Dolmatoff and Reichel-Dolmatoff 1974). Unexpectedly early ages for the first of the
four ceramic complexes recorded in Marajó Island (Simões 1969), the Ananatuba phase,
questioned the extent to which the archaeological record could be interpreted as a set of rapid
and short-lived migrations. Younger dates for exemplars of the Polychrome horizon near
Coari and lower Napo river compared with those recorded at the mouth of the Amazon (Evans
and Meggers 1968; Hilbert 1968) contradicted early suggestions that these were groups that
had rapidly expanded from west to east through the river network. Lastly, the discovery of
mid Holocene pottery in shell middens of the Salgado littoral, just south of the mouth of the
Amazon river (Simões 1981), signalled a time-depth for pottery making that contradicted an
introduction by immigrant horticulturist groups. Meggers and Evans (1978; 1983) took stock
of these developments by reformulating their ‘four-horizon’ model into a model of four
traditions or ‘time-sloping horizons’. This new account recognised an early presence of non-
horticulturalist ceramic shell-fishers, proposed more precise extra-Amazonian source regions
for ceramic complexes of each subsequent horizon/tradition, and argued that each of the latter
represented population expansions rather than rapid immigrations.
Surprisingly so given their own very early attempts to understand rates of ceramic
accumulation at archaeological sites, Meggers and Evans' (1957) appear to have dismissed or
paid no attention to Hilbert’s (1968) first published archaeological discussion of
anthropogenic dark earths. They also rejected Carneiro’s (1961; 1983) suggestion that shifting
agriculture could underpin sedentary lifestyles and population growth in the region, and
ignored Denevan’s (1966b; 1966a; 1970a) discussions about terra firme agricultural
possibilities and raised-field agriculture in the Neotropical lowlands. However, few doubts can
exist that their begrudging acceptance of ethnohistorical accounts pointing to large
populations, rejection of the possibility of floodplain agriculture due to the unpredictable
flooding regime, and interpretation of large riparian sites as ‘cross-roads’ in which cultural
patterns of root-crop horticulturists had amalgamated (Evans and Meggers 1968; Meggers
1971) were a response to the antipodal account of Amazonian pre-Columbian history
propounded by Lathrap (1968b; 1970b; 1970a; 1971; 1973; 1977) and his students (notably
Myers 1973, 1974; Brochado 1980; Brochado and Lathrap 1982; Brochado 1984).
Lathrap and his student’s account, as well as Denevan’s and Carneiro’s, rejected
Steward’s mistrust of the ethnohistorical sources and instead argued that ethnographic
indigenous inhabitants of the basin were descendants of larger, complex and sedentary
societies that had been decimated by illnesses and violence ensuing from European
colonisation (Lathrap 1968b, 1970b; Carneiro 1970; Denevan 1970b; Myers 1973, 1974;
Chapter 2. The Dark Earths 18
Sweet 1974). These accounts espoused an outlook on the environment of the region as
offering important opportunities for past human communities: root crops were Amazonian
domesticates (Lathrap 1977; see also Sauer 1950); indigenous management techniques
permitted a high yielding terra firme agriculture (Carneiro 1961, 1983), and cultivation of
seasonally flooded savannas (Denevan 1970a; Brochado 1980) and várzea floodplain
agriculture were theoretically capable of sustaining large populations (Lathrap 1970b;
Carneiro 1970; Myers 1973).
Beyond these common strands, Lathrap’s view of Amazonian pre-Columbian history
undoubtedly stands as the most provocative advocacy of the indigenous emergence of
sedentary lifestyles in the Neotropical lowlands. His understanding of Tropical Forest Culture
was that it had developed from small scale preceramic communities – shell-fishers of the
lower reaches of the Amazon basin – who had innovated pottery, domesticated root crops, and
slowly colonised much of the Amazon basin (Lathrap 1967, 1970b, 1977; Brochado and
Lathrap 1982). The fundamental plant staple of these communities, manioc, could be inferred
from the presence of ceramic vats, griddles and flint grater teeth (cf. DeBoer 1975a). The
widespread expansion of these groups had started early on as a result of the cultivation of
nutrient-rich soils of the várzea floodplains of large whitewater rivers, particularly those of the
central Amazon region, resulting in the inception of sedentary lifestyles and a significant rise
in population density. Competition for várzea floodplain soils among swelling populations had
prompted the successive budding off of floodplain agriculturists looking for new cultivable
land along the main waterways of the basin, a process tracked by similarities in material
culture and the distribution of languages from different linguistic families: the Tutishcainyo
and Shakimu at the eponymous sites of the Ucayali basin and elements of the lower Orinoco
basin Saladoid pottery were argued to represent an expansion of proto-Arawak speakers; the
modelled-incised pottery described at Hupa-iya, Hilbert’s (1955) Estilo Globular from
Oriximinã, and the Barrancas style of the lower Orinoco (Rouse and Cruxent 1963), which
Lathrap grouped under the Amazonian Barrancoid (≈ Meggers and Evans’ Incised-Rim
horizon or tradition), represented the expansion of proto-Maipurean speakers; Polychrome
tradition Marajoara pottery from Marajó Island and Napo phase from the Napo river
represented the expansion of proto-Tupi-Guarani speakers. Sites characterised by ceramic
complexes of the latter two traditions were not only large and dense but, in the case of the
Barrancoid tradition, also included the presence of flat ceramic platters similar to manioc
griddles. Lathrap argued that the impact of these emigrating waves had been felt well beyond
the confines of the Amazon basin, in effect kick-starting other Formative sequences in
northern South America (Lathrap 1971; Lathrap et al. 1977).
Chapter 2. The Dark Earths 19
Although the geographical core of Lathrap’s model was the Central Amazon region,
access to conduct research in this area remained beyond Lathrap’s reach (see Roosevelt 1991):
the cardiac model, as Carneiro baptised it, was instead based on interpretations of the
Amazonian record filtered through the first-hand knowledge of the archaeological sequence of
the Ucayali basin, Peru. This geographical focus goes some way towards explaining Lathrap’s
lack of attention to anthropogenic dark earths: whilst his somewhat scathing review (1970a) of
Hilbert’s (1968) research in the central Amazon region acknowledged their presence in more
substantive terms than Meggers and Evans’ writings ever did, his own investigations did not
record soils analogous to those reported in the Brazilian Amazon (Myers 2004). Thus, despite
the earlier and interesting report of the PAC-14 site by his student Allen (1968) in the Pachitea
basin, Lathrap’s sharper focus on anthropogenic dark earths only evolved through the
influence of his student Brochado: together they came to argue that these soils represented
refuse accumulations associated with successive or continuous occupations at archaeological
sites (Brochado and Lathrap 1982; see also Lathrap and Oliver 1987).
The contrasting positions embodied in these two narratives are at the base of what have
been characterised as the Standard and Revised accounts of Amazonian prehistory (Viveiros
de Castro 1996; Neves 1998b; Neves 1999; Stahl 2002). Although Lathrap has passed away,
Meggers has continued to advocate a number of arguments that question the possibility of
sedentary lifestyles and population growth in the Amazon basin. Among these arguments are,
first, that ENSO-related spells of arid conditions could force a reduction in population size and
a shift in lifeways from root-crop horticulture to savannah foraging that would explain the
mosaic-like distribution of Amazonian languages (Meggers 1975, 1977; Meggers 1979), the
presence of apparent gaps in the chronology of the ceramic sequence of Marajó Island
(Meggers and Danon 1988), and – at a broader level – the synchronic disruption and/or onset
of ceramic complexes throughout the lowlands of northern South America (Meggers 1994;
Schimmelmann et al. 2003; cf. Walker 2004). Second, that the late Holocene appearance of
pottery in the Amazon basin is a result of the resistance of local inhabitants to the advance of
horticulturist ceramists originating north of the region (Meggers 1997). And, third, that large
archaeological sites in which abundant pottery remains can be found – specifically expanses of
anthropogenic dark earths from the central Amazon region – constitute aggregation sites
which average numerous short-lived occupations by relatively mobile groups (Meggers 1990,
1991, 1995; cf. DeBoer et al. 1996; DeBoer et al. 2001; Heckenberger et al. 1999, 2001).
Chapter 2. The Dark Earths 20
3.2 Pre-Columbian sedentism, social complexity, and
Amazonian dark earths
Researchers who have conducted fieldwork in the Amazon basin since the 1980s have
started to outline a very different image of pre-Columbian Amazonia. Together with more
solid knowledge of preceramic occupations in the region (Mora 1991, 2003b,2003a;
Magalhães 1993, 1995; Roosevelt et al. 1996; Roosevelt 1998a; Roosevelt et al. 2002),
findings of early Holocene pottery (Roosevelt et al. 1991; Roosevelt 1995; Roosevelt 1999b),
and fossil and isotopic evidence for the use of plant cultivars in both preceramic and ceramic
assemblages (ibid., Roosevelt 1989b; Piperno and Pearsall 1998), for good measure the broad
geographical ubiquity, chronological position, and chemical composition of anthropogenic
dark earths have become a significant dimension of the archaeological record of the region
(Simões 1974, 1987; Simões and Corrêa 1987; Simões and Kalmann 1987; Simões and
Machado 1987; Herrera et al. 1980-1; Hilbert and Hilbert 1980; Eden et al. 1984; Andrade
1986; Mora 1991; Herrera et al. 1992b; Miller 1992a,1992b; Miller 1999; Heckenberger et al.
1999; Heckenberger 2005; Petersen et al. 2001; Neves 2005; Neves and Petersen 2006; Neves
2008). For most researchers, the characteristics of these soils question Meggers and Evans’
premise that past inhabitants could not have modified edaphic parameters to the extent of
permitting an increase in productivity of terra firme horticulture.
The recent wave of Amazonian dark earth studies undoubtedly begins with Smith’s (1980)
extensive survey of the location and physico-chemical characteristics of expanses of
anthropogenic soils in the Brazilian Amazon. Smith demonstrated that these anthrosols could
be found beyond large rivers (interfluvial dark earth patches), extended Sombroek’s and
Hilbert’s observations about their occurrence on different soil types, correctly surmised the
importance of charcoal in their make-up, and, echoing Myers (1973) survey of pre-Columbian
community patterns, argued that these soils could be regarded as tangible evidence for the
presence of large pre-Columbian settlements mentioned in 16th century ethnohistorical
sources. At about the same time, following the identification of similar anthrosols in 1st-2nd
millennium AD archaeological sites in the Araracuara region (von Hildebrand 1975; Herrera
et al. 1980-1; Herrera 1981), Eden et al. (1984) articulated previous reports by Hilbert (1968)
to offer the first basin-wide assessment of their archaeological significance. This assessment
discusses their association with late Holocene ceramic remains and underlines that their
present use by farmers does not imply an origin in, or use as, agricultural soils in the past. This
research was followed by Andrade’s (1986; 1988), who documented black and brown earths
in the Araracuara region and hypothesised that the former tracked the position of former
gardens near houses and the latter resulted from intensive or semi-intensive gardening
strategies in which organic mulches had probably been employed. Her research was followed
in this region by that of Mora, Herrera and colleagues (Mora et al. 1988; Mora et al. 1990;
Chapter 2. The Dark Earths 21
Mora 1991; Herrera et al. 1992c), who suggested that agricultural intensification in late
prehistory, including here a stronger emphasis on the cultivation of maize, was made possible
through the transformation of terra firme soils into higher-yielding dark earths via, among
others, additions of alluvial sediments.
Roosevelt’s (1980; 1989b; 1989a; 1990; 1991; 1993; 1996; 1997b; 1999a; 1999b; 2000;
2002) evolving account of the pre-Columbian history of the eastern Neotropical lowlands has
also paid attention to the presence of anthropogenic dark earths. Following the work of
Nimuendajú and echoing Smith’s synthesis, she has argued that exemplars near Santarém
represent evidence of sedentary settlements; marshalled their presence to suggest that
hierarchical chiefdoms existed in pre-Columbian Amazonia; and – echoing her arguments
about late Holocene population growth in the Orinoco basin (Roosevelt 1980; Roosevelt
1997b) – suggested that their presence could track sedentary settlements associated to
floodplain maize cultivation. Along somewhat similar lines, Denevan (1996) has pointed out
that the patchy distribution of dark earth expanses alongside rivers suggest a predilection for
bluffs overlooking cultivable várzea floodplains and argued that cultivation of the latter was
complemented by that of terra firme soils (Figure 9). Whilst the latter account is probably an
accurate depiction of many pre-Columbian cases, geographers and archaeologists have also
identified expanses of dark earths of variable size and shape alongside rivers whose sediment
load is unlikely to have furnished cultivable floodplains (Sombroek 1966; Simões and Corrêa
1987; Simões and Kalmann 1987; Simões and Machado 1987; Woods 1995; Woods and
McCann 1999; McCann et al. 2001; Woods 2002; Heckenberger 1998; Heckenberger et al.
1999; Lima 2003; Donatti 2003; Neves 2003; Moraes 2006). The latter research strongly
suggests that many dark earth expanses track sedentary settlements that would have relied on
terra firme agriculture (see Miller 1999; Woods et al. 2000; Roosevelt 2000; Petersen et al.
2001) and implicitly de-emphasises várzea cultivation as the main hypothetical form of
intensive pre-Columbian agriculture (cf. Myers 1992, 2004).
Further support for this terra firme emphasis has come from research into terras mulatas.
Beyond Andrade’s (1988) prescient remarks, Woods and McCann (Woods and McCann 1999;
Woods et al. 2000; McCann et al. 2001; Woods 2002) have extended Sombroek’s initial
survey of the Santarém region by documenting extensive areas with enriched anthropogenic
soils, discriminating macroscopically and chemically between terras mulatas and terras
pretas, and arguing that slightly higher total carbon yet lower phosphorus and calcium values
suggest intensive burning of deliberately-added mulch in agricultural fields. Denevan has
expanded his influential argument that ethnographically-recorded, spatially-extensive long
fallow shifting cultivation is an artefact of the introduction of metal tools (1992b) by
suggesting that pre-Columbian agriculture relied on a combination between spatially-
Chapter 2. The Dark Earths 22
intensive, short fallow cultivation of areas employing organic amendments and fire, and the
tending of house gardens. Soil modification associated with the former would result in the
development of terra mulata soils (see also Denevan 1998; Denevan 2001, 2004; see also
Hecht 2003). Myers (2004), on the other hand, has recently expressed the opinion that terras
pretas do not constitute settlement soils but instead represent a technology of soil
enhancement associated with the river-borne expansion of Barrancoid ceramists in the first
millennium AD. Whilst other archaeologists doing fieldwork in the Amazon region treat this
opinion with caution, not least because the layout of earthworks and geochemical data at some
expanses of terras pretas is strongly reminiscent of settlement structure (Kern 1996; Costa
and Kern 1999; Kern et al. 2004; Heckenberger et al. 1999; Neves 2003; Machado 2005;
Moraes 2006; Rebellato 2007), many follow Lathrap’s (1977) house garden model to suggest
that cultivation of specific plant taxa also took place within settlements.
To conclude this section, it can be stated that most archaeological accounts about
anthropogenic dark earths vary between considering them as outcomes of relatively short-
lived sedentary villages tracking the adoption of year-round agricultural subsistence (Neves et
al. 2003; Neves 2005; Neves and Petersen 2006; Lima et al. 2006) to suggestions that proto-
urban settlements developed uninterruptedly over the course of several centuries (Roosevelt
1999a; Heckenberger et al. 1999; Heckenberger 2003; Heckenberger 2005; Heckenberger et
al. 2008). However contrastable these opinions appear, they share the consensus view that
these forms of anthropogenic landscape transformation are archaeological signatures for the
presence of sedentary lifestyles in the Amazon basin. Notwithstanding, it is worth reiterating
that the archaeological record of Amazonian ceramists is by no means composed exclusively
of dark earth sites (e.g. Evans and Meggers 1968; Lathrap 1968a, 1970b; Raymond et al.
1975; DeBoer 1975a; Lathrap et al. 1985; DeBoer 1987; Simões and Araujo-Costa 1987;
Morales 1992, 1995; Neves 1998a). Moreover, whilst the vast majority of studied exemplars
appear to be associated with archaeological materials dated to the last two millennia (Eden et
al. 1984; Myers 2004; Neves 2005; Heckenberger 2005), reports do exist about expanses of
anthropogenic dark earths associated with much older occupations (Allen 1968; Miller
1992b). I will discuss the importance of the latter in Chapter 3. Before this, it is useful to
examine present arguments and hypotheses about the processes that lead to their formation
and development.
4. FORMATION PROCESSES OF ANTHROPOGENIC DARK EARTHS
4.1 Pedological and archaeological insights
In the preceding pages it has been mentioned that some researchers consider
anthropogenic dark earths as house gardens produced by the deliberate composting of
Chapter 2. The Dark Earths 23
settlement residues (Andrade 1986; Myers 2004), others perceive them as an outcome of the
accumulation, perhaps also management, of waste associated with settlements (see review in
Erickson 2003), yet others postulate alluvial inputs to make these soils more productive
(Herrera et al. 1992b; Woods 1995), and still others emphasise the role that pottery production
may play in understanding their makeup (Lima et al. 2002; Schaefer et al. 2004; Sergio et al.
2006). It is evident that these opinions do not necessarily exclude each other, especially
because a single, basin-wide account of these soils’ formation processes is unlikely to exist.
This explains in part the appeal of the ‘kitchen midden’ model (Sombroek et al. 2002), which
suggests that a combination between the decomposition of excrements, household garbage,
bone, and organic constructions (Sombroek 1966; Kern et al. 2004) and the concentration of
ash and charcoal derived from ground-level fires (Smith 1980; Glaser 1999), are the most
important inputs resulting in the formation of anthropogenic dark earths. A rise in soil pH
associated with organic waste is argued to permit the formation of resistant organo-mineral
complexes and thus augment the retention of a more stable pool of organic matter (Sombroek
1966); larger quantities of pyrogenic carbon are considered to provide more ubiquitous
sorption sites for metals (Glaser et al. 2003; Steiner et al. 2004; Liang et al. 2006; Solomon et
al. 2007); and a combination of illuviation and faunal mixing of comminuted and/or
decomposed constituents is considered to homogenise these inputs and contribute to the dark
colour of these soils (Vacher et al. 1998; Lima et al. 2002; Kern et al. 2004; Topoliantz and
Ponge 2005; Topoliantz et al. 2006).
In his review of pre-Columbian community patterns, Myers (1973) argued that the larger
and more complex settlement layouts that could be derived from ethnographic and
ethnohistorical sources – single-family house communities, multi-family rounded or circular
houses, plaza-centred groups of houses (including cases of multiple malocas around a plaza),
and linear groups of houses strung alongside rivers and lakes – were all characterised by
scrupulous maintenance of the patios, plazas, or circular plazas within, behind or around
which dwellings were located. These maintenance practices resulted in debris accumulating as
secondary refuse in either linear middens behind rectilinear rows of houses or in ring-shaped
middens around other types of settlements (from single and multi-family house-based
settlements to plaza-centred groups of houses). Erickson’s (2003) recent survey of the dark
earth formation literature re-examines Myers’s (1973) classic survey and supplements the
typology of community patterns with two new types: ethnographically-observed multi-family
roundhouses and settlements analogous to dense Mesoamerican house lots. He suggests that
anthropogenic dark earth expanses can be classified into three types – concentric, linear, and
centre-type – each of which may result from a combination between specifically-shaped refuse
accumulations, remobilisation of enriched soils once they have formed, and overlapping
occupations characterised by different settlement layouts.
Chapter 2. The Dark Earths 24
Whilst a bird’s eye view is an important archaeological perspective, important insights
about the formation of these soils come from studies of profile development. Two main
conceptual models for dark earth horizonation have been discussed in the literature (Figure
10). First, given a modal O-A-B soil profile, Vacher et al. (1998) suggest that vegetation
clearance associated with the implantation of settlements would lead to destruction of organic
litter, after which inhabitation-related production of organic and mineral inputs and the
modification of mineral surfaces through trampling, soil removal and other activities, would
lead to sub-differentiation of the original A horizon into eluvial and illuvial subhorizons, the
upper one being directly affected by settlement activities and the lower one accumulating
inputs from the settlement surface. Visible differences between these subhorizons would then
be obliterated as the lower subhorizon become saturated with pigmenting soil constituents,
effectively resulting in melanisation. Upon site abandonment, a new mineral surface (A
horizon) would be developed through upwards translocation of sediments by soil fauna,
obliterating settlement-related sedimentary structures (e.g. compaction) and interring artefacts
in the organically-enriched sediment matrix. Woods (1995), in contrast, highlights that the
accumulation of organic and mineral material would tend to bury the original surface,
resulting in a raising of habitation surfaces as inhabitation takes place. Given a modal O-A-E-
B soil profile, he argues that organic inputs would result in an enhancement in the activity of
soil fauna as well as strong melanisation of the new A horizon, transforming the sediments of
the original A-E-B sequence into a transitional AB horizon. Further sedimentation associated
with continued habitation would tend to result in repetition of the same process, i.e. build-up
at the surface and down mixing as a result of increased activity of soil fauna.
These models are useful to contextualise some of the inferences about formation processes
that can be drawn from archaeological studies of expanses of anthropogenic dark earths. At
the Manduquinha site, a relatively small dark earth expanse occupied over a period of
approximately 300 years prior to European contact, horizontal variability in elemental
concentrations of A horizon soil samples is interpreted as evidence for areas of transit,
middens, dwellings and shells heaps, effectively suggesting a relatively stable settlement
layout persisted during occupation (Kern and Kämpf 1989; Kern 1996; Costa and Kern 1999;
Kern et al. 2004; Ruivo et al. 2004). Heckenberger (2005), who illustrates how archaeological
settlements in the Upper Xingú region are up to 10 times larger than present-day ethnographic
villages, argues that circular plazas have remained fixed in space over centennial time scales,
in turn highlighting the potential role of site refuse management by past populations and
outlining important expectations about chemical variability within sites. Studies of multi-
component sites (e.g. Heckenberger et al. 1999; Neves 2003; Mora 2003b; Machado 2005;
Moraes 2006) tend to show good stratigraphic order in the sequencing of archaeological
Chapter 2. The Dark Earths 25
remains and broad stratigraphic continuity at the scale of the locale, in turn supporting Woods’
contention that dark earth expanses can be considered as accreting deposits. Recent discussion
of geochemical data by Rebellato (2007) suggests that horizontal variability in the chemical
signatures associated with former activity areas may be preserved at multicomponent sites if
net sedimentary build-up is sufficiently rapid.
In parallel to these contexts, other investigations have documented variation in settlement
function or layout over extended occupations: based on the changing floristic composition of
sediments, Mora, Herrera, and colleagues (Mora et al. 1988; Mora et al. 1990; Herrera et al.
1992b; Herrera et al. 1992c; Mora 2003a) have suggested that the specific black earths
interpreted by Andrade as house gardens are best seen as the result of events of habitation
(incorporating domestic waste produced in loco) alternated with events of cultivation
(incorporating organic agricultural amendments), followed by higher organic and mineral
inputs associated with denser populations, and subsequent additions of alluvial silt to amend
soil fertility. This interpretation not only points to the potential for shifting cultivation of terra
preta sites (see also Fraser et al. 2008; Fraser and Clement 2008) but also the superposition of
activity areas in complex and specific trajectories for particular locales (Erickson 2003). A
similar statement can be offered about forms of landscape engineering within dark earth sites.
These include earthworks that can be interpreted as deliberately-constructed or incidentally-
accumulated mounds, the presence of large circular bank-and-ditch and road complexes,
defensive ditches, and others (Nimuendajú 1952; Roosevelt 1999a; Heckenberger et al. 1999;
Heckenberger 2005; Neves 2003; Donatti 2003; Machado 2005; Moraes 2006). The
importance of these anthropogenic landforms should not be underestimated: they provide clear
indication that the sediments which make up anthropogenic dark earth sites were indeed
redistributed in the past and spell out forms of spatial circumscription associated with specific
settlement layouts that may prove important to understand high concentrations of organic and
mineral remains at specific sites.
A final set of observation pertains to the temporality of formation of anthropogenic dark
earths. Neves and colleagues (2003; 2004; Neves and Petersen 2006) have argued that the
narrow and overlapping radiocarbon dates on charcoal from the A horizon of specific terra
preta expanses of the central Amazon region indicate that these anthrosols formed in rapid
episodes characterised by short, intense and demographically-dense occupations rather than
long, sparse and continuous inhabitation events. Compelling as this argument appears when
regarded from the perspective of dated charcoal, the possibility does exist that downward
mixing redistributes a small volume of macroscopic charcoal – produced for instance in the
raking of a large hearth or the burning of a house structure – to different depths in the soil
profile. As will be discussed in Chapter 5, all sites used to illustrate this model demonstrably
Chapter 2. The Dark Earths 26
record multi-component occupations, a point that does not invalidate the suggestion of short
and demographically-dense occupations but does imply that successive re-occupations would
encounter vegetation physiognomies and soil characteristics modified by prior events or
moments of inhabitation.
4.2 Ethnographic insights
Separate studies of different indigenous communities in the upper Xingú region, an area
characterised by a mosaic of cerrado (savannah) and parkland vegetation, illustrate the
potential of circular plaza-centred villages surrounded by rings of dwellings as contexts for the
formation of anthropogenic dark earths. At Ipatse, Heckenberger (1998; 1999; 2003; 2005)
reports a ring-like string of elevated rubbish middens behind house structures and provides
chemical and physical analyses of soils from a plaza - house - midden transect that show the
lowest values of pH, organic matter, phosphorus, calcium, potassium, manganese, magnesium,
and sodium in plaza areas; mid values within abandoned houses; and high values within
middens. Analogous data are presented by Hecht (2003) at the Kayapó settlement of Gorotire.
Her study identifies different types of middens beyond plazas and houses and shows that soil
samples from them have comparatively much higher concentrations of key elements. Silva’s
(2003) study of an Asuriní village similarly shows a plaza/patio area surrounded by a ring of
households: although activity areas and garbage pits near houses exist, regular maintenance of
public spaces produces large middens behind houses, some being deliberate pilings of large
amounts of debris (in one case up to 1m in height and 40 sq. m in surface area) and others
more incidental accumulations.
The formation of peripheral middens is not limited to the upper Xingú. In the northwest
Amazon I had the opportunity to live for some weeks in Nova Fundação, a 30 year old Hupdu
village implanted by missionaries about an hour away from the Tiquié river. Nova Fundação
conforms to the plaza-centred community type1, being composed of over 30 wattle-and-daub
houses located around an oval empty space that is kept relatively clean by some sweeping and,
significantly, the action of surface run-off. Surrounding the settlement is a clear ring-shaped
midden ranging between 4 and 12 m in width in which manioc peelings, fish bones, raked-up
charcoal, ash, broken artefacts of various kinds continuously accumulate. These middens are
often covered with weedy vegetation and banana trees are planted on them (Arroyo-Kalin,
field notes, 2001). Similarly, Deboer and Lathrap’s (1979) ethnoarchaeological study of San
Francisco de Yarinacocha, in the Peruvian Amazon, argues that secondary refuse resulting
1 Nova Fundação is a modern analogue for the kind of site aggregation envisioned by Carneiro (1970). Its 200
or so inhabitants can be traced to five different Hupdu clans that 30 years ago lived dispersed in the nearby interfluvial rainforest. They were attracted into sedentary habitation by the provision of metal tools and mediation of interethnic relations with Desana communities conducted by Salesian missionaries (see also Reid 1979; Pozzobon 1991; Athias 1995).
Chapter 2. The Dark Earths 27
from constant sweeping and raking of household and plazas/patios should, under ideal
conditions, accumulate in settlement-peripheral middens. However, examination of the
settlement plan provided by these authors shows the presence of specific activity areas
detached from dwelling structures, for instance food preparation areas that are characterised
by packed-earth floors, areas where the pottery is fired (see also Silva 2003), and trampled
areas that tend to size-sort pottery fragments. Moreover, Siegel and Roe’s (1986) re-study of
the same village intimates that secondary refuse accumulation is not nearly as neat as
presupposed by their argument.
A number of different researchers (Balée 1994; WinklerPrins 2002; WinklerPrins 2006;
Neves et al. 2003; Neves et al. 2004) point to various forms of localised ‘dooryard’ burning of
organic debris that could result in localised, within-settlement concentrations of charcoal and
other debris. Further to these, my own ethnographic data in the Tiquié river region identify
three activity areas of special interest for the formation of dark earths: first, behind almost
every other house at the Nova Fundação village a food-processing and manioc-toasting area
accumulates large amounts of charcoal and ash; second, male-segregated, roofed spaces for
the daily preparation and consumption of powdered coca (ipadú) accumulate large amounts of
ash; third, smouldering fires under racks used for fish smoking, in all cases placed outside
houses, tend to produce large amounts of charcoal and soot. Whilst it is probably safe to
retrodict that some of these activities (dooryard burning, fish smoking?) frequently took place
outside roofed structures, others (e.g. ipadú and food preparation) may have taken place more
frequently inside communal dwelling structures in the past. The latter are a context which
studies of anthropogenic dark earths have paid insufficient attention to until now (see however
Erickson 2003).
Even the most cursory review of the Amazonian ethnographic literature highlights that the
kinds of enrichment that characterise anthropogenic dark earths may have taken place inside
dwelling structures leading to their build-up within them. Zeidler (1983) describes a 3-year old
Achuar dwelling as a thatch-roofed oval area of some 160 m2 enclosed by walls formed by
upstanding peach palm logs. He observes that the position of debris within the house reflects,
first, gender-ordained, communal and personal activity areas and, second, maintenance of
clean spaces through sweeping. However, he also notes that the periodicity of sweeping opens
up opportunities for artefacts to become interred as a result of trampling, a process that is
assisted by sedimentation of ash, charcoal, and burnt soil produced by and accumulated
adjacent to combustion features. Application of these observations to the study of
archaeological dwellings at the Real Alto site in Ecuador (Stahl and Zeidler 1988; 1990)
corroborates that larger debris accumulates in areas associated with higher sedimentation
(food preparation loci, wall trenches and interior floor space adjacent to walls) and small
Chapter 2. The Dark Earths 28
debris characterises what are interpreted as transit areas. These observations, well grounded by
cross-cultural actualistic studies (e.g. Villa and Courtin 1983; Hayden and Cannon 1983;
Gifford-Gonzalez 1985; Stein and Teltser 1989; Sherwood et al. 1995), can be extended to
consider other ethnographic observations of houses with earth floors in the Amazon basin (cf.
Myers 2004).
In the northwest Amazon, ethnographic descriptions of thatched-roofed longhouses
describe enclosed spaces internally divided into communal areas used for meals and transit,
compartments for nuclear families, and areas in which manioc processing takes place (Figure
11). Fireplaces of different kinds and purposes are frequently used in different parts of the
longhouse, resulting in the production of charcoal and ash. Many accounts suggest that the
interiors were or are swept regularly, sometimes accompanied by wetting of the otherwise dry
floors (Wallace 1892; Koch-Grünberg 1995 (1909):100-102; Rice 1910:695; Goldman 1963;
Hugh-Jones 1979; van der Hammen 1992). To my knowledge the largest longhouses reported
ethnographically are about 100 m in length (Steward 1948b). Whilst these types of dwellings
are less common today, ethnographic accounts often record memories of communities formed
by larger and more numerous longhouses (Hugh-Jones 1995). Some of the observations
reported in Zeidler’s ethnoarchaeological study also apply to smaller houses of the northwest
Amazon. For instance, each of the smaller thatched roofed structures used for habitation by an
extended Yuhupdu family that I observed in the São Martins de Cunurí village, Tiquié river
basin, in 2001, was characterised by a decimetric build-up of floors in which significant
amounts of organic debris, ash and charcoal were clearly accumulating. Communal meals
resulting in the deposition of abundant fish bones on floors were followed by events of
sweeping that most likely size-sorted rather than removed all bone fragments from the interior
of houses. Roofed precincts restricted the transportation of air-borne sediments permitting,
among other things, the accumulation of soot particles on the underside of roof thatching, the
latter encouraged in new houses to increase water-proofing. Finally wooden house walls not
only contributed to the trapping of debris and build-up of floor deposits but also acted as
obstacles for the free flow of surface run-off during rainfall.
A consideration of sedimentation inside dwellings would be incomplete without paying
attention to the fate of houses themselves. Zeidler (1983) mentions the case of an abandoned
Achuar house that had preserved a considerably thick floor deposit. Siegel and Roe (1986)
point to the recycling of material in abandoned houses in San Francisco de Yarinacocha.
Hecht (2003) reports the re-deposition of decaying house roofing in middens located in the
vicinity of houses (see below). Other situations include the collapse or burning of houses, their
abandonment for social reasons such as the death of household heads, and the deliberate burial
of houses with soil. The many possibilities that can be envisioned suggest that different
Chapter 2. The Dark Earths 29
pathways exist for the preservation of organic and mineral debris accumulated on floors.
Moreover, if the duration of a longhouse is as short as reported in some ethnographic accounts
(up to ten years, see Hugh-Jones 1979), building of new dwellings should render complex
palimpsests of floor deposits. This resonates with Erickson’s (2003) suggestion that on-site
shifts in house location over time, and multiple re-occupations expressing different settlement
layouts, may have enabled people to ‘live on their garbage.’ Indeed, it is possible that the
preferential formation of centre-type dark earths expanses is related to the spatial
circumscription by dense rainforest vegetation.
Beyond houses, activity areas and incidentally-formed refuse middens, it is worthwhile to
remember Lathrap’s (1977) argument that an ubiquitous aspect of Tropical Forest Culture is
the house garden or doorstep orchard, which he saw as the cradle for the domestication of
many of the basin’s cultivars. In her research in Araracuara, Andrade (1986) interpreted the
lack of compaction and specific ratios between phosphate fractions in pottery-rich black earths
as evidence for doorstep orchards that had been composted with household refuse. Whilst her
claim has been refuted (Mora 1991) and Eidt’s (1984) phosphate ratios are no longer
considered a reliable means to assess past land use, Andrade’s doorstep gardens sit
comfortably beside Sombroek’s kitchen midden model and the preceding discussion of house
floors as loci for the formation of dark earths. Bracketing arguments that suggest that ‘centre’
type terras pretas reflect horticultural use of the land inside villages for gardening (Sombroek
et al. 2003), there can be little doubt that areas within larger patches of dark earths must have
been used for cultivation.
Hecht’s (2003) work in the Upper Xingú provides the most important assessment of the
relationship between house gardens and middens in the formation of dark earths. This research
documents a transect that starts at a circular plaza surrounded by kin group houses and reaches
back to the disposal areas behind house patios. These patios include cooking areas and door
yard gardens in which specific edible and useful plants are grown, sometimes ash being used
to enhance their growth. Within these dooryard gardens she distinguishes three zones: garbage
disposal middens in which composting takes place; toss middens in which discarded objects,
residues from food preparation, and organic artefacts are dumped (sometimes being covered
with ash or swept earth); and burning middens where fire is used to reduce debris. Beyond the
patio itself, middens known as atykma accumulate animal waste, discarded roofing materials,
and charcoal resulting from the raking of hearths, all of which are periodically burned. Hecht
reports variability in the elemental concentrations of soils at each of these areas, the plaza
showing the lowest pH, carbon, phosphorus, nitrogen, calcium, manganese and potassium
values; gardens and toss middens showing the highest total carbon and phosphate values; toss
and burn middens showing the highest pH and potassium values; and the atykma and toss
Chapter 2. The Dark Earths 30
middens showing the highest concentration of total carbon and calcium. Hecht’s study,
therefore, not only provides compelling evidence for practices that may be variously described
as the composting of middens and the middening of compost, but also illuminates potential
sources of variability in the chemical make-up of settlement soils that can be directly related to
their agricultural use.
5. SUMMARY
This chapter has summarised the present of knowledge about Amazonian anthropogenic
dark earths: it has highlighted their anthropogenic origin, pointed out the basis for their
enhanced agricultural properties, and reviewed ethnographic and archaeological evidence for
inhabitation practices and pedo-stratigraphic dynamics involved in their formation. It has
suggested that a lack of recognition about their ubiquity and properties placed cornerstone
discussions about the emergence of sedentary lifestyles in the wrong footing, and summarised
the arguments that lead most archaeologists to interpret them as direct or indirect outcomes of
sedentary lifestyles. By placing the object of study of this dissertation in sharper focus, these
pages set the stage to tackle, in Chapter 3, the first of the two goals enunciated in Chapter 1: to
establish the character, time-depth, and significance of human practices that have resulted in
anthropogenic landscape transformations in the Amazon basin.
31
Chapter 3
THE ROOTS OF THE AMAZONIAN FORMATIVE
1. INTRODUCTION
The Formative – the emergence of sedentary lifestyles in the Americas – has been linked
to the historical process by which foragers dependent on a resource base composed of widely-
dispersed, wild resources came to rely increasingly on spatially-fixed food stuffs that were
storable and/or available for a substantial part of the annual cycle (Willey and Phillips 1965).
Although arguments have been advanced that natural concentrations of aquatic resources may
have played this role in some regional sequences (Mosley 1975; Roosevelt et al. 1991; Schaan
2004; see also Williams 2003), in areas where such concentrations did not exist or were less
predictable on a year-round basis, the appearance of sedentism is more generally linked to the
ennoblement of edible plants, their selection and phenotypic modification to achieve cultivar
status, their intensification to increase production, and consequent effects on the foodways of
past populations. In the Neotropics, however, archaeological evidence shows that the use of
plant domesticates on its own was not sufficient to spawn the emergence of sedentary
lifestyles (Piperno and Pearsall 1998; Stothert et al. 2002; Mora 2003a; Oyuela-Caycedo and
Bonzani 2005; Castillo and Aceituno 2006). The modification of the landscape to cultivate
specific plant taxa; the innovation of technical means to process and transform the latter into
edible and storable foodstuffs; and the intensification of cultivation to expand productive
capacity, were among the processes which led to the adoption of redundant and eventually
sedentary habitation patterns. By concentrating people in space and underwriting population
growth, these processes spawned novel social arrangements associated with new foods,
peoples and places.
In the preceding chapter I argued that Amazonian dark earths constitute a dramatic
example of anthropogenic transformation of the landscape and pointed out that most
documented cases appear to be associated with sedentary, pottery-making societies that
flourished during the last 1500 years before European colonisation (Lima et al. 2006). I also
pointed out that the archaeological record of Amazonian ceramists is by no means composed
exclusively of dark earth sites (e.g. Evans and Meggers 1968; Lathrap 1968a, 1970b;
Raymond et al. 1975; DeBoer 1975a; Lathrap et al. 1985; DeBoer 1987; Simões and Araujo-
Costa 1987; Morales 1992, 1995; Neves 1998a). This prompts me to suggest that a discussion
Chapter 3. The Roots 32
about the emergence of sedentary lifestyles based on the presence of dark earths and pots
comes close to affirming the consequent: where pottery is present, sedentism is; if no pottery
is present, sedentism is not; if dark earths lack pottery, reports can be questioned or dismissed
(e.g. Hornborg 2005). The point I wish to emphasise here is not whether instances of
preceramic sedentism or ceramic mobility exist in the Neotropical lowlands – they evidently
do (Neves 1998a; Zucchi and Tarble 1984; Oyuela-Caycedo 1995; Stothert et al. 2003;
Castillo and Aceituno 2006). Instead, I wish to argue that the formation of anthropogenic dark
earths constitutes the tail end of a multi-threaded and time-deep historical process, one in
which fruits, roots, soils and pots became part of the specific conditions which define the
Amazonian Formative.
2. THE LANDSCAPE IS DYNAMIC: A PALAEO-ENVIRONMENTAL BASELINE
Palaeo-ecological research over the last twenty years (see Berrío et al. 2002; Mayle et al.
2004; Anhuf et al. 2006; Bush et al. 2007 for recent summaries) has shown that the vegetation
physiognomy, geomorphology, and fire regimes of the Amazon basin have by no means
remained unchanged during the late Quaternary (see Figure 12 for the location of records
discussed in this section). A scenario of full rainforest fragmentation during the Late Glacial
(e.g. Prance 1982; Prance and Lovejoy 1985; Haffer 1982; Haffer and Prance 2001; Colinvaux
and De Oliveira 2000; Colinvaux et al. 2000) has been contradicted by pollen data from the L.
Pata2 core in the northwest/central Amazon, a region in which high precipitation is observed
today (Colinvaux et al. 1996; Bush et al. 2004a). However, records from savannah areas in the
northern periphery of the basin, for instance L. El Pinal (Behling and Hooghiemstra 1999) and
L. Moreiru (Wijmstra and van der Hammen, 1966, cited in Teeuw and Rhodes 2004), as well
as pollen cores from rainforest-covered areas in the southern periphery of the basin, for
instance the Katira creek core in Rondônia, Brazil, and the L. Chaplin core in the Bolivian
Amazon (van der Hammen and Absy 1994; Mayle et al. 2000; Burbridge et al. 2004), argue in
favour of a contraction of the northern and southern borders of the rainforest by about 200 to
300 km (van der Hammen and Hooghiemstra 2000; Cowling et al. 2001; Anhuf et al. 2006,
especially Figure 3; see also Burn and Mayle 2007). Climatic conditions of the Late Glacial
would have been characterised by 5-6°C lower temperatures (Stute et al. 1995), a more
restricted CO2 budget (Mayle et al. 2004), and overall less precipitation (van der Hammen
2001).
2 In the following pages I abbreviate the names of water bodies such as Lago Pata as L. Pata lake. This
convention provides a useful way to distinguish between geographical features and eponymous archaeological sites in subsequent chapters. For instance, the Lago Grande archaeological site overlooks the L. Grande lake (see Chapter 4).
Chapter 3. The Roots 33
Late Glacial conditions would have also had very significant impacts on the alluvial
geomorphology of the region. The LGM marine regression, regarded to have produced
coastlines some 130 m below the present-day mean sea level (Fairbanks 1989; Peltier and
Fairbanks 2006), would have exposed some 200 km of marine shelf on the equatorial Atlantic.
The Amazon river would have incised its channel through this exposed landmass, discharging
via a large delta that today is submerged under Atlantic waters (Irion 1984b). Lower sea levels
would have resulted in a more inclined gradient of the whole drainage network, encouraging
much more active alluvial incision and forming the deep, canyon-like troughs through which
many of the larger rivers of the basin flow today (cf. Thomas 2008). Although recent research
also argues that tectonics is a factor that determines the formation of these channels
(Latrubesse and Rancy 2000; Latrubesse and Franzinelli 2002; Costa et al. 2001), consensus
does exist that the Solimões-Amazon and Madeira rivers only began to infill them with
sediments as the sea-level started to rise after the Late Glacial. Today’s extensive várzea
floodplains only started to form after the mid Holocene (Irion et al. 1997; Latrubesse and
Franzinelli 2002; Franzinelli and Igreja 2002; Latrubesse and Franzinelli 2005).
The millennial transition from Late Glacial to Holocene conditions brought about warmer
temperatures in Amazonia. In addition, as the displaced Inter-Tropical Convergence Zone
regained its equatorial alignment (see discussion in Bush and Silman 2004), it would have
resulted in an overall increase in humidity. These shifts brought about the gradual re-
expansion of arboreal vegetation to areas which, during the late Pleistocene, had been
occupied by grassland (van der Hammen and Absy 1994) and/or parkland vegetation
(MacFadden 2005). However, the exact timing of this recolonisation is difficult to pinpoint
because it varied regionally and was affected by dramatic fluctuations between LGM-like cold
to mid Holocene-like warm conditions during the Younger Dryas (Thompson et al. 1998;
Thompson 2000).
Regional variation is best appraised through a comparison of data from different records.
For instance, the L. Chaplin and L. Bella Vista records in the Bolivian Amazon and 13C SOM
data from the Porto Velho-Humaitá transect, Rondônia, both suggest increasingly more arid
conditions during the Younger Dryas and early Holocene (Freitas et al. 2001; Burbridge et al.
2004). However, further to the northeast, in the middle Tapajós quarry of Itaituba, 13C isotopes
of megafauna dated as late as 13.3-13.2 cal kyr BP suggest these large herbivores had a
folivore diet characteristic of parkland vegetation (Rossetti et al. 2004b; see also MacFadden
2005). Finally, the TAP 02 core, which provides a record of conditions in the lower Tapajós
river from the early Holocene onwards, points to the presence of rainforest vegetation from at
least ca. 9.3 cal kyr BP (Irion et al. 2006). These palaeo-ecological data underscore the true
extent of regional variability and highlight that peoples expanding into Amazonia during the
Chapter 3. The Roots 34
Pleistocene-to-Holocene transition would have been confronted by a regionally-heterogeneous
landscape.
On the other hand, the shift towards milder climatic conditions that marked the onset of
the Holocene appears to have been accompanied by the presence of different, non-analogous
vegetation compared to the present-day baseline. Significant in this regard is the presence of
Podocarpus pollen – a taxa characteristic of cloud forests in high and cooler elevation belts
(Wille et al. 2001; Hooghiemestra and van der Hammen 2004) – in a number of early
Holocene lowland records. Included here are the L. Pata core from the Hill of Six lakes
(present from the LGM to >9 cal kyr BP, cf. Bush et al. 2000; De Oliveira 2005); the Pantano
de Mónica I core in the Colombian Amazon (present from the start of the record at 11 cal kyr
BP until ca. 8.5 cal kyr BP, Behling et al. 1999); the L. Chaplin and L. Bella Vista cores in the
Bolivian Amazon (respectively from the LGM and 13 cal kyr BP until 10 cal kyr BP, Mayle et
al. 2000; Burbridge et al. 2004); the L. Carajás core from the eponymous plateau (from around
15 cal kyr BP until the 9th cal millennium BP, Absy et al. 1991; Sifeddine et al. 1994); the L.
Curuça core in easternmost Amazonia (up to the 11th cal. millennia BP, Behling 2001), and,
beyond the limits of the Amazon basin, the L. Caço core in Maranhão (from around the 16th
and 13th cal. millennia BP to the early Holocene, see Behling 2001; Ledru et al. 2001; Ledru et
al. 2002). If a southbound shift of the ITCZ resulting from the short term expansion of
northern hemisphere glacial masses during the Younger Dryas can be presupposed (Bush and
Silman 2004), it is possible that these conditions – significant enough that they are recorded in
the ODP32 deep sea core (Haberle and Maslin 1999) – were characterised by slightly lower
temperatures, more reduced precipitation and more open arboreal vegetation than the present
baseline (see also Bush et al. 1990; Bush et al. 2001; Pennington et al. 2000; Pennington et al.
2004). The progressive drop-off in Podocarpus influx in the various records, in turn, would
attest to warmer climates during the first half of the Holocene.
Like climatic regimes of the Pleistocene-Holocene transition, warmer conditions during
the first half of the Holocene appear to have had different regional effects across the Amazon
basin. Cores from the northwest (Behling et al. 1999) and central Amazon (Behling et al.
2001b; Bush et al. 2004a) evidence continued rainforest cover and a total lack of signals for
landscape-level burning, a phenomenon that is most likely underwritten by the overall higher
precipitation regimes of these regions. In contrast, early Holocene pollen records from the
Ecuadorian Amazon such as L. Ayauchi and the Maxus 4 core (Piperno 1990; Athens and
Ward 1999; Weng et al. 2002), as well as cores from lakes in the lower Amazon such as L.
Geral, L. Santa Maria and L. Saracuri (Bush et al. 2000; Bush et al. 2007), all of which show a
clear maintenance of dense rainforest vegetation, record surprisingly strong fire signals, some
perhaps associated with anthropic influence. Records from areas peripheral to the humid
Chapter 3. The Roots 35
Amazon generally accentuate this trend: aside from pollen cores from the Colombian Llanos
(L. El Pinal, L. Loma Linda), which appear to show more humid conditions after ca. 7.0 cal
kyr BP (Behling and Hooghiemstra 1998, 1999, 2000; see also Behling and Hooghiemstra
2001), soil charcoal from the FSB site, in the forest-savannah ecotone of Roraima (Desjardins
et al. 1996; see also Sanaiotti et al. 2002), indicates that significant burning took place
between 8.5 and 6 cal kyr BP; soil charcoal dated at Petit Saut, French Guyana, shows an
overlapping signal between 7.2 and 4.7 cal kyr BP (Vacher et al. 1998); pollen records and
SOM carbon isotope data from southwest Amazonia show low sedimentation, an on-going fire
regime, and a marked shift towards savannah vegetation (Freitas et al. 2001; Burbridge et al.
2004; Mayle et al. 2007); and soil charcoal from the vicinity of the Jamaxim river, south of
Itaituba, suggests more pronounced landscape-level burning at c.7.5-7.0 cal kyr BP (Soubies
1979-80). Along similar lines, the easternmost Amazonian records, for instance L. Curuça and
L. Caço (Behling 1996, 2001; Ledru et al. 1998; Ledru et al. 2001), show a rise in charcoal
influx and indications of a slightly more deciduous or open rainforest vegetation; the L.
Carajás core, in parallel, shows a dry signal that includes significant charcoal influx during the
8th cal millennium BP, in hand with a sharp decrease in arboreal vegetation (Absy et al. 1991;
Sifeddine et al. 1994).
Warmer conditions peaked during the mid Holocene and were accompanied by a rising
sea-level. It is estimated that it would have reached its present elevation by ca. 7.7-6.9 cal kyr
BP and risen to its maximal Holocene transgression level towards 5.7-5.1 cal kyr BP (Martin
et al. 1993; Behling and da Costa 1997; Irion et al. 1997; Behling 2002; Angulo et al. 2006;
see also Milne et al. 2005). Because the river base level of the eastern half of the Amazon
basin is so low, sea-level rise would have resulted in a deeper inland penetration of the
Atlantic tidal zone, in part damming the flow of large rivers draining into the lower reaches of
Amazon. Throughout much of the Amazon basin, this would have produce a slower infilling
of LGM channels as well as the appearance of fluvial rias – the now-ubiquitous alluvial lakes
formed when small terra firme streamlets are drowned by the rising base level of the larger
rivers they discharge into (Tricart 1977). This highlights that pollen cores obtained from such
water bodies, for instance the L. Calado core in the central Amazon region (Behling et al.
2001b) and perhaps the TAP-02 core in the lower Tapajós (Irion et al. 2006), record a mix
between terrestrial and hydrarch succession (Behling 2002; Irion et al. 2006; see also Weng et
al. 2002).
Whilst pollen, soil charcoal and SOM 13C isotopic data from Rondônia, the Bolivian
Amazon, and the Jamaxim river suggest a mid Holocene expansion of open vegetation that
was only re-colonised by rainforest during the last three or two millennia (Soubies 1979-80;
Freitas et al. 2001; Burbridge et al. 2004; Mayle et al. 2007), no clear evidence exists that
Chapter 3. The Roots 36
warm mid Holocene conditions prompted anything as severe as savannah vegetation in the
humid core of the Amazon basin (Behling et al. 2001b; Bush et al. 2007; cf. Meggers 1975;
Meggers 1977; Meggers 1979). Instead it is possible that rainforest vegetation became
somewhat more open towards the mid Holocene and increasingly more dense thereafter.
Regional variability needs to be kept in mind in order to understand the overall patterns
observed in the data (van der Hammen and Hooghiemstra 2000; cf. Meggers 1994). In the
northwest and central Amazon, records from the Hill of Six Lakes (Bush et al. 2004a) show
consistent humidity indicators throughout the mid Holocene; phytolith and soil charcoal data
from the same overall region suggest the continued existence of closed and unfired rainforest
at least from 5.4-5.0 cal kyr BP to 2.0 cal kyr BP, a time after which burning is most likely
anthropogenic (Sanford et al. 1985; Saldarriaga 1994; Piperno and Becker 1996; Santos et al.
2000). Upstream from Manaus, the L. Calado record shows hydrarch-related wetter conditions
from 4.6-4.5 to 2.1-2.0 cal kyr BP, and arguably still wetter ones after 2.1-2.0 cal kyr BP. In
the same vein, data from the Maxus cores in the Ecuadorian Amazon suggest a decrease in
seasonality by the mid 5th millennium BP, with an increase in wet conditions recorded from
3.7 cal kyr BP (Weng et al. 2002) to at least 1.4 cal kyr BP (Athens and Ward 1999). In this
time frame, data from the L. Parker core in the Peruvian Amazon (Bush et al. 2007) show high
charcoal counts yet dominant presence of arboreal taxa. In the eastern half of the basin,
continued cover with rainforest taxa is also evident at L. Geral, at least until a Mauritia swamp
expands after ca. 3.5 cal kyr BP. A marked stability in the overall diversity of rainforest taxa is
also recorded from as early as 6.9 cal kyr BP to until ca. 3.4-3.3 cal kyr BP at the nearby L.
Comprida. As in the case of the central Amazon region, but perhaps starting at an earlier time,
charcoal influx in these records suggests anthropic disturbance associated with pre-Columbian
agriculture (Bush et al. 2000; Bush et al. 2007).
A better understanding of these overall patterns emerges when their timing is compared to
other signals of landscape change. Studies of sea-level transgression in the Brazilian littoral
identify significant sea-level rise events during three periods: 5.8-5.0 cal kyr BP, 4.2–3.7 cal
kyr BP, and 2.7–2.1 cal kyr BP (Suguio et al. 1985; Angulo et al. 2006; see also Absy 1985;
Perota and Botelho 1992; Behling and da Costa 2001; Behling et al. 2001a). The first of these
moments is evidently associated with warmer mid Holocene conditions and, to judge from
evidence for a lowering of lakes in the Brazilian and Peruvian Amazon (Bush et al. 1989;
Bush et al. 2007), appears to have been more severe than previous and subsequent Holocene
warm spells. The second and third moments appear as short 300-600 year reversals towards
warmer conditions (Angulo et al. 2006) in what is otherwise a clear pattern towards cooler and
more humid conditions that leads towards increasingly denser rainforest vegetation (Mayle
and Beerling 2004; Bush et al. 2007). It will be observed that shifts in overall pollen and
charcoal influx in many of the preceding records appear to coincide approximately with sea-
Chapter 3. The Roots 37
level rise events. This applies equally well to data from the northern periphery of the basin:
the Las Margaritas record, in the open savannah of the Colombian Llanos Orientales, shows
that forest expanded from around 5.4 cal kyr BP and then co-existed with savannah vegetation
under a high precipitation regime between 4.3 cal and 2.5-2.0 cal kyr BP (Wille et al. 2003);
the Pantano de Monica 2 core, in the northwest Amazon, shows rainforest with a changing
composition from 4.5-4.4 cal kyr BP, and thereafter more humid conditions from the mid third
millennium BP onwards (Behling et al. 1999); the Loma Linda record (Behling and
Hooghiemstra 2000) evidences an increase in rainforest taxa from 6.9-6.8 to 4.0-3.9 cal kyr
BP, and still wetter conditions until 2.4-2.3 cal kyr BP; in the same time range, the L. Angel,
L. Sardinas, L. Carimagua, and L. Chenevo pollen cores, which record the presence of
Mauritia and Mauritella (Behling and Hooghiemstra 1998; Berrío et al. 2002), point to the
formation of gallery forest. That this tempo extends to those records out of the reach of
expected hydrarch effects suggests that spells of warmer climatic conditions were basin-wide
phenomena.
The preceding review shows that the landscape of the Amazon basin has not remained
static since the beginning of the Holocene and highlights the need to take into account
geographical variability and alluvial evolution in the interpretation of environmental and
archaeological proxies. Palaeo-ecological data for the terminal Pleistocene and early Holocene
suggest a markedly different Amazonian landscape in terms of vegetation assemblages,
geomorphology, and overall seasonality, with a marked trend towards warmer conditions. The
mid Holocene sea-level rise evidently had cascading effects: at least in eastern Amazonia,
archaeological remains deposited in locales within reach of higher river levels would stand a
much lower chance of overall preservation. Palaeo-ecological data for the second half of the
Holocene suggest periods of warmer, in some places drier, conditions within an overall trend
towards more humid and cooler climates. These data highlight the continued presence of
rainforest in much of the Amazon basin but clearly more open vegetation in the south western
periphery of the basin, supporting a scenario in which the southern border of the rainforest
shifted north during the mid Holocene. Palaeo-environmental data also suggest that the more
humid core defined by the northwest and central Amazon regions remained largely unfired
until ca. 2.0 cal kyr BP, in striking contrast to other rainforest-covered areas – the
Ecuadorian/Peruvian Amazon and the lower Amazon – where fire signals of likely anthropic
significance begin perhaps as early as the 5th millennium BP.
Chapter 3. The Roots 38
3. THE ROOTS OF THE AMAZONIAN FORMATIVE
3.1 First fruits? Colonisation and arboriculture
The ascendants of the human communities that colonised the Amazon basin during the
terminal Pleistocene and early Holocene (Miller 1987; Magalhães 1995; Roosevelt et al. 1996;
Costa 2002; Mora 2003b; Meggers and Miller 2003) were undoubtedly foragers that radiated
into northern South America via the isthmus of Panama and/or the Caribbean littoral (Cooke
1998; Pearson 2004). During this expansion, these groups learned how to inhabit the wide and
temporally-changing range of biomes that characterises the northern half of the sub-continent
(Ranere 1980; Dillehay 1999; Dillehay 2000; Gnecco 2003a,2003b): in the Neotropics east of
the Andes some groups targeted complementary animal and plant resources of the midlands
and lowlands (López 1995, 1999; Gnecco and Mora 1997; Gnecco and Aceituno 2004;
Aceituno and Castillo 2005; Castillo and Aceituno 2006); others expanded onto dry savannas
of Colombia, Venezuela and the Guianas (Cruxent and Rouse 1956; Rouse and Cruxent 1963;
Bryan et al. 1978; Ochsenius and Gruhn 1979; Boomert 1980; Jaimes 1998; Oliver and
Alexander 2003); yet others became established in the open parklands and savannas of Mato
Grosso (Vilhena-Vialou and Vialou 1994; Vilhena-Vialou 2003) and Central Brazil (Prous
1986, 1991b; Kipnis 1998; Prous and Fogaça 1999; Araújo et al. 2005). The earliest
occupations recorded at each of these regions vary in antiquity: some – notably the Colombian
intermontane valleys and the savannas located to the north and southwest of the Amazon basin
– may have served as source areas for populations radiating into the eastern lowlands.
In the preceding section I summarised some of the main characteristics of Amazonia
during the terminal Pleistocene and early Holocene. Human communities expanding into the
basin at around this time would have encountered slightly lower temperatures and more
reduced precipitation than at present. These conditions would have prompted a gradient from
open arboreal vegetation to mosaics of parkland/savannah to savannah in regions which today
are characterised by dense rainforest, open rainforest, parkland and parkland-savannah
mosaics. The contrast between these vegetation physiognomies is suggestive when examined
from the vantage point of palaeontological and palaeontological evidence (see Figure 13 for
the location of all archaeological sites mentioned in this and the following two sections). Just
outside the Amazon basin proper, bones of giant ground sloth have been found in stratigraphic
association with a unifacial lithic industry and hearths with charcoal dating to 12-11.6 cal kyr
BP at the Santa Elina rockshelter, in Mato Grosso do Norte (Vilhena-Vialou and Vialou 1994;
Vilhena-Vialou 2003). At Itaituba (Figure 12) , I have already mentioned the presence of
bones of extinct megafauna showing a parkland isotopic signature and dated to ca. 18.8-18.6
and 13.3-13.2 cal kyr BP (Rossetti et al. 2004b). Whilst it is necessary to emphasise that these
remains are not associated with human artefacts, it is significant that the younger findings
Chapter 3. The Roots 39
appear to be co-eval or slightly earlier than the oldest well-documented human occupations of
the rainforest-covered parts of the basin – broad-spectrum foragers who occupied Caverna da
Pedra Pintada, a rockshelter north of Santarém, between 13.4-12.9 and 11.6-11.3 cal kyr BP
(Roosevelt et al. 1996; Roosevelt et al. 1997; Roosevelt 1998b; Michab et al. 1998; Roosevelt
et al. 2002).3
Archaeological remains from Caverna da Pedra Pintada include shallow hearths, lumps of
red paint related to stylized cave wall paintings, and large quantities of lithic artefacts (plano-
convex scrapers, blades, and crude bifacially-produced stemmed triangular projectile points,
among others). These remains suggest broad relations with terminal Pleistocene and early
Holocene occupations in Venezuela, the Guianas and Central Brazil (Oliver and Alexander
2003; Plew 2005; Kipnis 1998; Dias 2004; Araújo et al. 2005). Faunal remains include fish,
freshwater invertebrates, chelonians, and possible large ungulates. Botanical remains consist
mainly of carbonized fruits and wood fragments of Jutaí (Hymenaea parvifolia and H.
oblongifolia), Achuá (Sacoglottis guianensis), Pitomba (Talisia esculenta), Brazil nut
(Bertholetia excelsa), Muricí (Byrsonyma crispa), Apiranga (Moururi apiranga), Sacurí
(Attalea macrocarpa), Tucumã (Astrocaryum vulgare), and Curuã (Attalea spectabilis). These
remains highlight an ‘Archaic’ or ‘generalised’ pattern (Roosevelt et al. 1997; Roosevelt
1998b; Roosevelt et al. 2002; Michab et al. 1998) that can be related to other early
occupations in the region.
Among these is Peña Roja, a 350 m2 open-air site located on a non-flooding, low alluvial
terrace of the Caquetá river, in the Colombian Amazon (Mora 2003b). The preceramic
component of the site is dated by numerous radiocarbon dates between 10.7-9.9 and 9.1-8.8
cal kyr BP and includes macro and micro-fossils of edible and useful palms from the genera
Astrocaryum, Oenocarpus, Mauritia, Maximiliana and Dieffenbachia. Complete and broken
charred seeds are found in volumes that are an order-of-magnitude higher than in the
overlying, late Holocene ceramic component recorded at the site (Cavelier et al. 1995; Mora
2003a). The early Holocene lithic assemblage lacks bifacial or finely retouched pieces but
comprises flaked, ground and polished tools among which are wood-working instruments
(notches, wedges, and concave scrapers) as well as plant-processing or cultivation-related
implements (mortars, milling stones, hoes, and axes). The latter appear towards the later
moments of the preceramic occupation, associated with microfossils of three allochtonous
3 Early dates for Caverna da Pedra Pintada have been mired in some controversy (Fiedel et al. 1996; Haynes
1997; Reanier 1997; response in Roosevelt et al. 1997). Beyond ‘Clovis First’ discussions (Roosevelt et al. 2002), the original Science article defines an ‘Initial A’ period on the basis of four 14C dates on seeds (Roosevelt et al. 1996:380). However, the oldest ‘Initial Period’ 14C date on a single seed is 10,560±60 (� -76953). An additional early 14C date from a carbonised single seed is 10,683±80 BP (lab code unreported, discussed as ‘Late’, see Roosevelt 2000:481, Table 15.1). These 14C dates calibrate to 12.7-12.4 cal kyr BP and 12.8-12.7 cal kyr BP, i.e. are younger than the age of megafauna at Itaituba.
Chapter 3. The Roots 40
cultivars :Calathea allouia (leren, a root crop), Cucurbita sp. (squash), and Lagenaria
siceraria (bottle gourd) (Piperno and Pearsall 1998). More attention will be devoted to the
latter evidence in the next section.
The presence of an ‘Archaic’ pattern in the earliest occupations of northwest Amazonia
and the lower Amazon region evidences that the abundance and predictability of aquatic fauna
near riverine areas was probably an extremely important aspect of the human colonisation of
Amazonia. Following this reasoning, early colonisers would have remained tethered to
watercourses and – most likely assisted by watercraft – moved through the drainage network
from one to another area rich in fish resources. Harvesting of widely-dispersed plant
resources, the conventional story goes, would have merely supplemented the diet of these
groups. Actualistic research among Amazonian foragers (Balée 1994; Politis 1999; Morcote et
al. 1996; Morcote et al. 1998; Clement et al. 2008), however, provides exciting insights that
clearly orients this story towards a different direction. These studies suggest that the recurrent
discard of seeds/nuts of fruits at frequently-revisited locales would have been enough to kick-
start the formation of anthropogenically-induced patches of desirable fruit-bearing trees.
Germination of seeds concentrated at particular locales would have encouraged cross-
fertilisation among plant individuals whose fruits had proven attractive to human
consumption. The deliberate or incidental removal of seeds from these clumps to other locales
would have increased the extent to which the germplasm of specific taxa was shaped by
cultural selection (Clement 2006a; see also Zohary 2004). In other words, the dynamic
interaction between human communities and trees bearing edible fruits, an agrilocality in the
terms of Rindos (1984), would have led to processes of semi- or incipient domestication that
created patches of edible resources in the landscape (Clement 1999a; 2006b). These patches
would have supplemented areas rich in aquatic fauna to configure an attractive resource pool
available to – and indeed made available by – early foragers (cf. Bailey et al. 1989).
Evidence for an arboricultural emphasis is not limited to Caverna da Pedra Pintada or Peña
Roja. The preceramic component of the Gruta do Gavião rockshelter, located on the Carajás
plateau (Magalhães 1995, 1993; Hilbert 2005; Kipnis et al. 2005), includes a large combustion
feature with seeds, endocarps, bones of small terrestrial animals and fish, and shells of turtles
and mussels. These remains are associated with lithic nut breakers, end-scrapers, side-
scrapers, hammers and flakes knapped using the bipolar technique. Radiocarbon dates point to
occupations between 9.5 and 8.5 cal kyr BP and also around 7.8-7.7 cal kyr BP, evidencing
the early presence of arboricultural practices in southeast Amazonia at a time range which
overlaps occupations at Peña Roja. Similarly, at Abrigo do Sol, a rockshelter located along the
Guaporé river, upper Madeira basin, taxonomically-unspecified carbonised endocarps are
reported in association with cobble hammer stones, expediently used flakes, unifacial scrapers,
Chapter 3. The Roots 41
flakes with occasional pressure retouch, and a bifacially worked blades with bilateral
notching. These remains, capped by an early Holocene palaeosol variously dated to 12.8-12.4
and the 10.2-10.0 cal kyr BP, indicate that an arboricultural emphasis was also characteristic
of occupations in southwest Amazonia4. Further indications of an arboricultural emphasis is
recorded beyond the Amazon basin, including here early Holocene evidence of tree harvesting
from the Orinoco basin (Barse 1995, 2003), the Colombian intermontane valleys (see Gnecco
and Mora 1997; Aceituno and Castillo 2005; Castillo and Aceituno 2006), and the Colombian
Llanos (Correal et al. 1990).
In my view, the broad areal extent of this pattern strengthens the case for considering
anthropogenically-induced concentrations of edible fruits as an important dimension of the
human colonisation of the Neotropical lowlands. Given that flowering patterns in humid
tropical climates are species-specific and some fruits are present year-round (Lovejoy and
Bierregaard 1990; Clement 2006b), taxonomically-distinct anthropogenic groves would have
supplemented the drainage-dependent flooding seasonality of aquatic resources and perhaps
also attracted a higher density of terrestrial fauna (Linares 1976; Beckerman 1987; Stahl
2000). As regards the density of these concentrations: initially they would have appeared as
spaced-out nodes that punctuated the expansion of small kinship groups into unoccupied
areas; later, as human communities increased demographically and set out their mobility
ranges and social encounter regimes, concentrations of fruit trees probably became common
biotic features of the landscape. Their increase as the colonisation of the lowlands advanced
most likely contributed to the establishment of spatially-redundant patterns of mobility
(Beaton 1991; Borrero 1999; Meltzer 2004). Put another way, it seems reasonable to echo the
gist of Gnecco’s remarks (2003a; 2003b; see also Mora 2003b; Piperno and Pearsall 1998):
the human colonisation of the Neotropical lowlands did not wait for plant domestication but
actually relied on it.
3.2 Next roots? Anthrosols and the manioc question
The distribution of artefact remains reported at the Peña Roja site shows no less than two
distinct moments during the early Holocene preceramic occupation (Piperno and Pearsall
1998; Mora 2003b). A first one, discussed in the previous section, is represented by large
numbers of complete and broken charred seeds of edible tree taxa and a tool kit that arguably
has already abandoned bifaciality ‘off-site’ in favour of wood-working and plant processing.
A second moment retains these characteristics but also sees the adoption of stone tools
4 Miller (1987; 1999:333; see also Meggers and Miller 2003) has argued that a pre-Younger Dryas occupation
dated as early as 18.2-16.7 cal kyr BP is recorded at the site. However, his chronology is based on inconsistent pairs of dates on the same materials produced by different laboratories. Beyond laboratory errors, these dates could very well be documenting events of landscape-level burning similar to those recorded in terminal Pleistocene pollen records of the overall region (Burbridge et al. 2004).
Chapter 3. The Roots 42
associated with plant-processing and/or cultivation – grinding stones, axes and hoes – as well
as the appearance of microfossils of allochtonous cultivars – Calathea allouia (leren, a root
crop), Cucurbita sp. (squash), and Lagenaria siceraria (bottle gourd). Lithic hoes post-date
similar implements from El Pital, on the middle Cauca valley (Herrera et al. 1992a), and
reinforce the suggestion of an immediate source for these cultivars in the Colombian
intermontane area, where a similar pattern of burning of seeds is recorded (Cardale Schrimpff
2005a). This inference finds support in the presence of root crop fossils of leren (Calathea
allouia) and/or arrowroot (Maranta arundinacea), as well as squash and gourds, in sediments
and on tools associated with the earliest moments of occupation in preceramic sites of the
Porce and middle Cauca valleys (Aceituno and Castillo 2005; Castillo and Aceituno 2006)5.
The presence of plant domesticates in the preceramic component of Peña Roja has
prompted different interpretations (Cavelier et al. 1995; Piperno and Pearsall 1998; Oliver
2001; Mora 2003b; Aceituno 2006; Roosevelt 2006; see also Cardale Schrimpff 2005a). At
stake are different opinions about how mobile the occupants of Peña Roja really were and to
what extent they relied on plant domesticates. Beyond this discussion, however, little attention
has been paid to the implicit historical ecology that these overlapping preceramic moments
signal: a set of redundant and spatially-congruent occupations in which the mixing of perhaps
deliberately-burnt seed endocarps and occupation debris resulted in a slightly higher pH,
higher organic matter retention, and higher soil phosphorus (Cavelier et al. 1995; Gnecco and
Mora 1997: 688). These localised changes to the soil mantle do not only have an
archaeological dimension but are also likely to have fulfilled the incidental agronomic
function of enhancing the nutrient status of local soils, in turn improving their aptitude for the
growth of edible plant stuffs. Amazonian contexts identified by prior research (the Abeja site,
see Mora 1991) as well as research in regions beyond the Amazon basin (Castillo and
Aceituno 2006; Cardale Schrimpff 2005a), clearly highlight similar edaphic dimensions of
arboricultural practices for the location of all archaeological sites mentioned in this and the
previous section). It can therefore be argued that the success in cultivating allochtonous
cultivars in the acid soils of the Amazon basin most likely relied on the positive feedback loop
signalled by the embryonic formation of Amazonian anthropogenic soils.
Concentrations of aquatic resources, anthropogenic clumps of fruit trees, and anthrosols
attractive for plant husbandry would have played a significant role in developing redundant
mobility and residential patterns throughout the Amazonian lowlands. However, current
evidence falls short of suggesting that these occupations supported fully sedentary lifestyles.
5 In the early Holocene, grinding tools have also been reported at San Isidro (Gnecco and Mora 1997; Gnecco
2003a), the Pacific Ecuadorian lowlands (Stothert et al. 2003), and Panama (Piperno 2007). As will be discussed in Chapter 4, they are also prominent in the lithic assemblage of the Dona Stella site (Costa 2002; Lima 2003; Neves 2003).
Chapter 3. The Roots 43
On the one hand, it may be significant that the Peach palm (Bactris gasipaes), the only palm
tree whose fruits constitute a dependable, albeit seasonal source of starch (Clement 1995), is
conspicuously lacking from early Holocene assemblages of the Amazon basin (see Morcote
and Bernal 2001); on the other, it is unknown whether cultivation of species such as Calathea
allouia (leren), arrowroot (Maranta arundinacea), Cucurbita sp. (squash) and Lagenaria
siceraria (bottle gourd) would have together constituted a sufficiently productive and reliable
carbohydrate package in the absence of specific high starch-yielders (see Gragson 1997).
Whilst opportunities for seasonal complementarity between fruit and root crops clearly exist
(Clement 2006b), exploring the onset of early sedentary life in the region warrants attention to
cultivars that may have been introduced to, or were domesticated within, contexts dominated
by early anthrosols and which, upon continued cultivation, could serve as year-round sources
of energy. As I understand published evidence, the best candidates are two crops prominent in
most ethnographic accounts of Amazonian horticulture, Zea mays and Manihot esculenta.
Zea mays is a crop rich in calories and protein, under particular conditions grows
sufficiently rapidly that more than a few yields per year can be achieved, and can be processed
in ways such that it becomes a dependable source of starch. Consensus so far is that Z. mays
was domesticated in Central America (Pope et al. 2001; Piperno and Flannery 2001). One of
the striking realisations that research based on plant microfossils brought about was how early
on Z. mays had been used in northern South America (Piperno and Holst 1998). Z. mays
pollen is found in a sediment core taken near the Sauzalito archaeological site, in the middle
Cauca valley, towards 7.6-7.5 cal kyr BP (Bray et al. 1987); pollen is also recorded in the
Hacienda Lusitania core, El Dorado valley, Colombia, towards 6.2-5.7 cal kyr BP (Monsalve
1985); Z. mays starch grains and phytoliths are reported embedded in sediments and tools
dated to 6.5-6.0 to 5.5-5.0 cal kyr BP in the Porce river basin, Colombia (Castillo and
Aceituno 2006); and Z. mays remains may yet be confirmed with the very ancient pottery
reported at San Jacinto 1 during the 7th millennium BP (Oyuela-Caycedo in Smalley and Blake
2003:693; see also Iltis 2000). Z. mays phytoliths are also present in early and mid Holocene
occupation at Las Vegas and Real Alto in the Ecuadorian Pacific lowlands, and in the
Aguadulce rockshelter, Panama, by the 8th millennium BP (Piperno and Pearsall 1998;
Pearsall 2003; Piperno 2006).
The earliest evidence for the presence of Zea mays in Amazonia comes from the lowland
Ecuadorian pollen core at L. Ayauchi and dates back to at least 5.3-5.0 cal kyr BP (Piperno
1990). It is complemented by pollen and phytolith evidence from the Abeja site, located some
50 km upstream from Peña Roja, in the Araracuara region (Mora 1991; Herrera et al. 1992b).
At Abeja, diagnostic microfossils are found in sediments that are older than the Tubabonipa
component, which is dated between 5.5-5.3 and 5.0-4.9 cal kyr BP. The latter also includes
Chapter 3. The Roots 44
Zea mays phytoliths and pollen, Manihot pollen, veritable quantities of charcoal, and records
slight enrichment with phosphate. When the dates of these finds are compared to other north
and east of the basin, they appear to show the type of predictable geographical fall-off that one
might expect to see in a crop diffusing from neighbour to neighbour over space and time.
However, cultivation of Zea mays in the Amazon basin may have been extremely difficult: L.
Ayauchi is a maar, a lake formed on an ancient volcanic crater, suggesting nearby cultivation
of Zea mays was possible on more fertile soils formed on a weathering volcanic substrate.
Findings of Zea mays at the Abeja site are not reflected in pollen records from the Araracuara
region (van der Hammen et al. 1992; Berrío et al. 2003), suggesting soils beyond habitation
sites acted as limiting factors for cultivation.
The scant carbon isotope data available for Amazonian human bones – even if it is for a
later period – indicate that Zea mays only became a true dietary staple towards the very end of
the pre-Columbian archaeological sequence, and then only in specific regions (Roosevelt
1989b; Roosevelt 2000, see chapter 4). The use of this crop over millennia, therefore, may
have been associated with the production of alcoholic beverages and feasting (Raymond 1993;
Piperno and Pearsall 1998; Iltis 2000; Tykot and Staller 2002; Smalley and Blake 2003).
Hence, even if palaeobotanical evidence provides impressively early indications of interaction
and down-the-line borrowing between populations of northern South America, it seems
unlikely that Zea mays was a key dietary staple during much of Amazonian pre-Columbian
history; consequently, it is unlikely to have been a key resource for the emergence of
sedentary lifestyles.
More relevant are inferences that can be drawn from a consideration of the quintessential
crop described in ethnographically-recorded practices of shifting cultivation: manioc (Manihot
esculenta ssp. esculenta Crantz). Many scholars highlight manioc as a key crop in the
Amazonian formative because of its high starch yield, well-documented ability to grow on
acid soils, and capability of keeping its tubers unharvested for over 12 months – a trait which
has been described as ‘underground storage’ (Carneiro 1983; Piperno and Pearsall 1998;
Heckenberger 1998). In the Amazon basin, early palaeobotanical evidence for the presence of
Manihot sp. is limited to veritable amounts of pollen found in the 5.5-5.3 to 5.0-4.9 cal kyr BP
Tubabonipa component of the Abeja site. Evidence of Manihot sp. in approximately the same
time range is also recorded beyond the Amazon basin. These include 5th millennium BP
Manihot starch grain and phytoliths associated to Valdivia occupations at the Real Alto site
(Chandler-Ezell et al. 2006), 4th millennium BP Manihot starch grains from sites south of the
the Peruvian Casma valley (Perry 2002; Ugent et al. 1986), and also a sharp rise in Manihot
starch grains and pollen in sites of the Porce valley around the mid Holocene (Castillo and
Aceituno 2006).
Chapter 3. The Roots 45
The timing of these findings is worthy of particular attention because genetic studies have
ascertained that the wild Manihot species genetically-closest to all studied accessions of
cultivated manioc is Manihot esculenta spp. flabellifolia, a shrub from the savannah-forest
ecotone of the southern periphery of the Amazon basin (Olsen 2002; Olsen and Schaal 2006)
that reportedly shows ‘intermediate’ concentrations of cyanogenic glucosides. Whilst research
documenting the presence of plant macro and microfossils in this ‘domestication hearth’ is
lacking, it is noteworthy that archaeological research in the Jamari river, a tributary of the
upper Madeira river, has identified the earliest evidence of anthropogenic dark earth sites in
the Amazon basin: Massangana phase sites RO-PV-27 and RO-PV-48 are characterised by the
presence of 45 to 80 cm thick dark anthropogenic horizons extending over areas of up to
90x180 m. These enriched soils and the presence of anvil stones, mortars, pestles, grinding
stones, and rubified clay fragments suggest that these preceramic communities had a dedicated
emphasis on plant processing and were most likely sedentary occupations. Dates for
Massangana occupations start around 5.6-5.3 cal kyr BP, a time frame which is characterised
by drier conditions and more open, fire-prone vegetation in the southern periphery of the basin
(Freitas et al. 2001; Burbridge et al. 2004; Mayle et al. 2007). It will be evident that this
timing is co-eval with Manihot pollen evidence from the Abeja site in northwest Amazonia.
It can be argued that preceramic dump heaps would have constituted useful ‘cradles’ to
select Manihot tubers at a time when climatic conditions made the harvesting of underground
storage organs an attractive option (Clement, com. pers. 2008). However, this would imply a
domestication event in the mid Holocene that is apparently contradicted by additional
evidence for Manihot microfossils from regions outside the Amazon basin: the latter includes
Manihot starch grains on grinding tools embedded within sediments dating to 7.8-7.7 to 7.2-
7.0 cal kyr BP at the Aguadulce rockshelter, Panama (Piperno and Holst 1998; Piperno et al.
2000); Manihot-type starches on milling stone bases and edge-ground tools within sediments
dated to between 10.3-9.9 and 8.5-8.3 cal kyr BP at the El Jazmín site, middle Cauca valley
(Aceituno and Castillo 2005; however, cf. Gnecco and Aceituno 2004, Tabla 3); Manihot
starch grains on stone tools found within sediments dating between 8.2-8.0 and 7.5-7.4 cal kyr
BP at the 021 site of the middle Porce river, Colombia (Castillo and Aceituno 2006); Manihot
macro and microfossils associated to charcoal dates as early as 9th millennium BP in the Zaña
valley, Peru (Rossen et al. 1996; Dillehay et al. 2005; Dillehay et al. 2007); and a single pollen
grain of Manihot sp., deemed to represent an undomesticated variety, in sediments older than
6.9-6.8 cal kyr BP at the L. Sardinas core, in the Colombian Llanos Orientales (Behling and
Hooghiemstra 1998). These data might cast some doubt on the suggestion that Manioc was
domesticated during the mid-Holocene and would suggest that a founder effect would have
taken place before 10.3-9.9 to 8.5-8.3 cal kyr BP, the age of microfossils at the El Jazmín site.
Chapter 3. The Roots 46
If the research of geneticists is to be credited, this would have taken place somewhere in the
southern periphery of the Amazon basin.
I believe there is another way of interpreting this evidence: early Holocene Manihot sp.
microfossils could also signal evolutionary ‘dead-ends’, i.e. indicate consumption, perhaps
even initial domestication, of other morphologically-convergent Manihot species that did not
contribute to the lineage of domesticated manioc. In this respect, numerous wild species close
in morphology, ecology and geography to M. esculenta ssp. flabellifolia are described in the
literature: M. carthaginensis, M. aesculifolia, M. saxicola, M. pruinosa, M. peruviana, and M.
grahami (Allem 2002). The harvesting of tubers of any of these would suffice to produce
these early Holocene microfossil signals. If this interpretation is correct, it is possible that
early use of Manihot species in different regions of the lowlands was followed by the
domestication and subsequent expansion from southwest Amazonia of Manioc of the Manihot
esculenta spp. flabellifolia lineage. This would have resulted in the erosion of other Manihot
varieties and given birth to the single lineage to which all present-day cultivated Manioc
varieties belong to. The presence of alleles of M. brachyloba, M. carthaginensis, M.
peruviana, M. tristis and others in different accessions of Manihot esculenta ssp. esculenta
(Elias et al. 2004; Pujol et al. 2005a) has been interpreted as evidence for (recent)
hybridisation between domesticated and wild manioc species (Pujol et al. 2007; Duputié et al.
2007). However, these data could well support the hypothesis advanced here if one envisions
that, as domesticated manioc use expanded, it hybridised with different Manihot species which
had been by preceramic peoples of the early Holocene.
The argument I am developing here is that Manioc was crucial to the emergence of
sedentism in the Amazon basin. However, if a mid Holocene ‘founder effect’ is postulated, it
might be asked why the archaeological record of the Amazon basin lacks widespread evidence
of mid Holocene sedentary occupations. Whilst insufficient archaeological sampling is part of
the reason, further attention is warranted to aspects of Manioc as a potential dietary staple:
even though thousands of different landraces of this crop are known, two broad varieties can
be recognised – bitter and sweet manioc. Bitter varieties show high concentrations of
cyanogenic glucosides, are pest resistant, grow well in acid soils, and provide high starch
yields. However, they have a major drawback: they need to be detoxified before consumption.
In contrast, sweet varieties can be consumed without detoxification yet are less resistant to
pests, require better soils, and provide lower starch yields. Because both varieties are part of
the same species and no absolute threshold for toxicity seems to exist (Nye 1991; Dufour
1994), it has traditionally been thought that intermediate varieties exist. However, I have not
been able to find any solid evidence for intermediate varieties and the few cases of present-day
hybridization that have been observed produce ‘bitter’ offspring (Fraser, comm.. pers, 2008).
Chapter 3. The Roots 47
More importantly, bitter varieties are common throughout much of the eastern half of
Amazonia, Orinoquia and the Guianas, whilst sweet varieties are more common in the Andean
piedmont and western half of the basin (Denevan 1971; Carneiro 1983; Boster 1984; Chernela
1987; Beckerman 1987; Dufour 1989; Dufour 1995; Wilson and Dufour 2002). The relevance
of this observation will be developed in this and the following sections.
Recent genetic research confirms both sweet and bitter manioc are part of the Manihot
esculenta spp. flabellifolia lineage yet also suggests that each evolved separately after
domestication (Elias et al. 2004). If correct, this research sheds some light on the hypotheses
advanced by McKey and Beckerman (1993) to account for these two varieties: Hypothesis 3,
the suggestion that sweet and bitter varieties constitute two independent domestications, can
be rejected on the basis of published evidence – at best the data suggests ancient divergence
from a common ancestor. As regards the other three, none of them – that the cultural selection
of a non-bitter variety resulted in a toxic variety better suited to withstand pests (Hyp. 1); that
a bitter variety was ennobled to a non-toxic variety to increase edibility (Hyp. 2); and that
sweet and bitter varieties both evolved from a wild ancestor of intermediate cyanide content
(Hyp. 4) – explains the geographical distribution of sweet and bitter varieties. The latter point
is emphasized by McKey and Beckerman (McKey and Beckerman 1993; see also Beckerman
1991) who suggest that sweet varieties may be more appropriate for relatively mobile
communities and that bitter manioc may be linked to larger pre-Columbian sedentary
societies.
In broad outline and considered with some time depth, the suggestion that sweet and bitter
manioc varieties can be associated with different lifestyles has doubtless merit. As I
understand the data, it seems extremely unlikely that a bitter variety of Manihot esculenta spp.
flabellifolia would have been selected for by preceramic populations of the southern periphery
of the basin. This is because key to the detoxification process of bitter manioc are two
complementary actions (Hugh-Jones 1979; Dufour 1988; McKey and Beckerman 1993; Oliver
2001): the shredding and comminution of tubers in order to ensure hydrolysis of glucosides,
and the elimination of HCN as a gas or dissolved in water. The second step can be achieved
using two distinct procedures: boiling and/or long soaking, resulting in different outcomes,
farinha seca and farinha d’água (Fernandes and B. 1962). De-toxifying before fire-resistant
pots became widely used by Amazonian populations would have limited detoxification
techniques to the production of some early Holocene equivalent of farinha d’agua and, of
necessity, would have had to rely on wooden containers, holes in the ground, or small stream
ponds (pers. obs. Tiquié river, 2001). If groups were relatively mobile, the chances of tapping
into the ‘sedentary’ potential of Manihot would have been extremely limited.
Chapter 3. The Roots 48
Pujol et al. argue that manioc evolved from a fire-adapted species that was initially
restricted to fire-prone seasonal habitats. Replanting using stalk cuttings, the brittle
morphology of which is not present in the wild ancestor (McKey, pers. comm.. 2008), would
have initially fulfilled the aim of increasing seedling density in newly burned areas, especially
in wetter habitats where natural fires were rare. Pujol et al. thus argue that manioc was
“eminently pre-adapted to slash-and-burn agriculture, which enabled spread of this plant into
habitats much wetter than those occupied by its wild ancestors” (2002:377). Whilst I have few
doubts that this account is overall correct, I would argue it is missing some intermediate steps.
Studies of tuber utilisation by Neotropical foragers (Gragson 1997) suggest that it is far more
likely that the domestication of Manihot took place as tubers collected in open areas where
transported to dump heaps/house gardens characterised by enhanced soil parameters. Tubers
would have not been sought for higher concentrations of cyanogenic glucosides, especially if
the order of the day was to eat them raw or to roast them. Instead, tubers would have been
selected for low concentrations of cyanogenic glucosides, a trait which depends on a single
genetic mutation (B. Schaal, pers. com. 2006). The localised higher-fertility soils of dump
heaps would have been employed to maintain a germplasm characterised by tubers with low
concentrations of cyanogenic glucosides, a phenotypic trait which could be readily
perpetuated through vegetative propagation. The selection for brittle stalks that could be
replanted therefore seems like a reasonable outcome of the need to prevent planted stocks
from lapsing back towards individual of high toxicity.
To summarise, initial conditions for manioc domestication are likely to have been similar
to those which permit the cultivation of present-day sweet manioc. Because the latter does not
yield well in very acid soils, in many parts of the Amazon basin its cultivation is restricted to
doorstep gardens. What about ‘bitter’ manioc? The obvious corollary of the preceding remarks
is that a more toxic manioc would evolve if selective pressures on low toxicity could be
relaxed. I can see no way in which this could happen other than the adoption of detoxification
and processing techniques which permitted, in return for hard labour, achieving higher energy
returns. I believe it is reasonable to suggest that this only took place after the widespread
adoption of fire-worthy ceramic vessels and argue further that these enabled the production of
a host of ‘secondary’ products with true storage potential (Hugh-Jones 1979; Nye 1991). This
would mean that a wild ancestor of intermediate toxicity would be selected first for low
toxicity and, subsequently, would be selected further for higher starch yield, relaxing selective
pressures on low toxicity (see Pujol et al. 2005b for a similar phenotypic ‘return’ to
characteristics of wild ancestors). If sweet Manihot esculenta spp. esculenta, a domesticated
variant of the Manihot esculenta spp. flabellifolia lineage, expanded during the mid Holocene
to the more humid northwest of the basin (Abeja site) and beyond (Porce river, Valdivia
Chapter 3. The Roots 49
occupations at Real Alto, mid Holocene fossils of the Zaña valley)6, this relaxation of
selective pressures could have taken place wherever ceramists encountered the manioc root
crop. Included here are the Colombian lowlands north of the Amazon basin, which both
Reichel-Dolmatoff (1997 (1986)) and Piperno and Pearsall (1998) have argued was a likely
domestication hearth for this crop. In my view, and as regards the use of bitter manioc, their
intuitions are correct, especially if one presupposes a preceramic expansion of sweet manioc
that eroded other edible Manihot taxa from the genetic pool that came to characterise modern
varieties.
3.3 The Ceramic Archaic
Before discussion about soils, roots and pots can be taken any further it is necessary to
examine the ‘thorny oyster’ of Amazonian archaeology: the question of pottery use among
shell-fisher groups of the Amazon basin (Hilbert 1968; Simões 1981; Roosevelt et al. 1991).
Some context is in order: the location and age of pottery-bearing Amazonian shell-middens –
the lower Amazon and Salgado littoral – are no doubt linked to Holocene sea-level changes
that peaked in the mid Holocene. Similar sites, some also showing not quite as early evidence
of pottery, are reported in northern South America and parts of Central America (Willey and
McGimsey 1954; McGimsey 1956; Evans and Meggers 1960; Rouse and Cruxent 1963;
Gallagher 1976; Reichel-Dolmatoff 1986; Stothert 1985; Rodríguez 1995; Cooke 1995;
Oyuela-Caycedo 1996; Sandweiss et al. 1998; Gaspar 1998; Dias Jr. 1999; Boomert 2000;
Williams 2003; Lima et al. 2004). Roosevelt (1991) has suggested that groups which occupied
the fluvial reaches of the lower Amazon were relatively sedentary and relied year-round on the
exploitation of shell fish. This seems unlikely in the face of comparative evidence (e.g. Cooke
1995; Oyuela-Caycedo 1996) although so-called shell-fishers appear to have been capable of
relying on complementary use of terrestrial and aquatic resources.
Leaving these considerations aside, undoubtedly the most remarkable and controversial
dimension of this archaeological evidence (e.g. Hoopes 1994; Meggers 1997; Roosevelt
1997a; Lima et al. 2006) is the presence of pottery dated to the early Holocene. The oldest
evidence is recorded in a thin midden at the Caverna da Pedra Pintada site, the Paituna
occupation. Shells from this midden – which includes freshwater mussels, snails, fish, turtle
shell, charcoal, and charred seeds – have been dated to a reservoir-corrected (Stuiver and
Braziunas 1993) age between 7.7-7.5 and 7.4-7.3 cal kyr BP, overlapping the pre-ceramic
range of the Gruta do Gavião site. Embedded with these remains are small quantities of
ceramic shards of two types: undecorated, shell-tempered wares and incised-decorated, sand-
6 Perry (2002) and Chandler-Ezell (2006) have both argued that starch grains of the Pacific coast display
morphologically distinct characteristics compared to other accessions. Their observation is consistent with the suggestion that different Manihot species were ennobled by different groups at different times. The fine detail of these observation remain to be pursued by future research..
Chapter 3. The Roots 50
tempered shards. The former are recorded to be highly fragmented, the latter are reported to
show soot staining. A shell-tempered shard is dated to a reservoir-corrected 7.4-7.3 cal kyr
BP: if the dated carbon pool, presumably originating from the organic temper, correctly
identifies the moment of manufacture (i.e. if scavenging of older shell-midden materials for
use as pottery temper can be overruled), this shard stands as the oldest known example of
pottery in the Americas. A sand-tempered shard, on the other hand, is dated by TL to a range
between 5.4-4.3 cal kyr BP, suggesting it is intrusive from an overlying ceramic occupation.
This interpretation is supported by the fact that the latter, the Aroxí occupation, consists of
sand-tempered pottery, human burials, and carbonised seeds dated between 4.2-4.0 and 3.8-
3.5 cal kyr BP (Roosevelt 1995; Roosevelt et al. 1996).
The remarkable ceramic component at Caverna da Pedra Pintada is echoed by evidence
from excavations at Taperinha, a 6.5 m high fluvial shell midden made of freshwater
invertebrates and located alongside an abandoned channel of the lower reaches of the Amazon
river (Roosevelt 1991, 1995, 1997a). Reservoir-corrected radiocarbon dates on shells suggest
the site accreted between 7.6-7.5 and 6.9-6.7 cal kyr BP, possibly extending to 6.2-6.0 cal kyr
BP. A total of 48 shell strata include charcoal, rocks, lithics, faunal bones, human bones, and
pottery shards. Lithic remains include hammer stones, flake tools, grinding stones, and boiling
stones, the latter made of an iron-rich raw material. Bone tools include awls, shell- and turtle
shell-scrapers, as well as a bone plug made of aquatic mammal bone. Taperinha pottery, found
throughout the shell midden at very low densities, is described as red-brown grit-tempered
shards of hemispherical bowls with tapered or rounded rims and rounded, thickened bases.
Incised rim decoration is present on 3% of this assemblage whilst surface decoration,
consisting of broad and thin line incision forming parallel lines or complex curvilinear motifs,
is rarer. Carbon in a grit-tempered, undecorated shard from the lower levels has been dated to
7.5-7.6 cal kyr BP; the same shard is dated by TL to 7110 + 1422 (8.5-5.7 cal kyr BP). If the
midpoint of the TL determination is considered likely to approximate the true age of resetting
of the luminescence signal, and possible contamination by older carbon can be disregarded,
both determinations support and cross-check dates from Paituna shell-tempered shards at
Caverna da Pedra Pintada.
In order to contextualise these early Holocene finds, it is necessary to consider two
additional sources of archaeological evidence, the Salgado littoral Mina phase and the Guiana
littoral Alaka phase. The Mina phase consists of coastal shell-middens (Simões 1981), which
are mound-like accumulations of aquatic remains – principally brackish water shell fish, fish
bones, and crab pincers – located along the Salgado littoral, on the Atlantic coast immediately
south of the mouth of the Amazon river. Radiocarbon dates on charcoal locate occupations
between 6.2-5.6 and 4.1-3.5 cal kyr BP, tending a bridge to the youngest age range of
Chapter 3. The Roots 51
Taperinha (Roosevelt 1995). These dates suggest inhabitation events took place as the mid
Holocene sea-level regression was on its way. Primary human burials, lithic and bone tools,
and pottery are reported from these sites. Lithic tools are highly distinctive: they include semi-
polished trapezoidal axes, ground stone metates, manos, nut-breakers, choppers, and unifacial
flake tools. Bone tools include punches or awls, strongly resonating with the Taperinha
evidence. Mina phase pottery is described as an undecorated coarse ware tempered mostly
with shell- or shell-and-sand, and in which coils employed for its manufacture can still be
observed. Shell-tempered shards have been dated to a reservoir-corrected age between 5.6-5.3
and 4.6-4.4 cal kyr BP. Sand-tempered pottery has not been dated and, moreover, may be
refuse from subsequent occupations (Corrêa 1987).
The Guiana littoral Alaka phase shell middens constitute a parallel sequence to the lower
Amazon and Salgado littoral archaeological remains. These occupations are best known from
shell middens associated with shifting mangrove environments in Guiana (Evans and Meggers
1960), but include over 35 shell middens which begin just east of the Orinoco delta and extend
all the way to Guiana (Williams 1992). The sequence begins during the early Holocene with
occupation at shell middens such as Barabina Hill, Koriabo Point, and Piraka, reported as pre-
ceramic by the excavators (see Williams 1997) but argued to include pottery by Roosevelt
(Roosevelt 1995, 1997a). Lithic and bone artefacts found in these middens are in broad terms
comparable to those reported from Roosevelt’s excavation at Taperinha. Early Holocene shell-
middens are followed in time by the presence of sites of the mid Holocene, such as
Kabakaburi Hill, dated to 6.3-6.0 cal kyr BP, as well as others such as Warapana Hill and
Siriki Hill (Williams 1992). No pottery is recorded at these sites, but lithic implements such as
trapezoidal axes, large adzes and chisels are clearly analogous in function and style to those
found in co-eval sites of the Salgado littoral. Williams (1992; 2003) argued that these
represented specialised tools for the manufacture of canoes and that the latter would have
enabled both an extension of the foraging ranges of site occupants to interior regions and a
more dedicated emphasis on the exploitation of mangrove palm trees to produce sago-like
starch. In the Guiana sequence, he argued further that pottery was first present as early as 4.5-
4.3 cal kyr BP at sites such as Hosohoro Creek and Seba Creek or, less clearly, as early as
5.5.-5.0 cal kyr BP at Wahana Island. The latter age range, it will be observed, is in good
agreement with dates for Mina phase occupations and shell-tempered pottery at the Salgado
littoral middens.
Beyond the acrimonious debate about the presence of early Holocene pottery in Alaka
phase shell middens (Roosevelt 1997a; Williams 1997), the parallel early to mid Holocene
shell-fisher sequences of the lower Amazon/Salgado littoral and Guiana mangrove swamps
provide an important context for discussing putative early Holocene use of pottery in the
Chapter 3. The Roots 52
Amazon basin. Although some researchers dismiss the early Holocene dates reported for
ceramic remains (e.g. Meggers 1997; Lima et al. 2006), this review of the published evidence
agrees with Roosevelt’s (1995) conclusion that radiocarbon dates on shells and grit-tempered
pottery from Taperinha, as well as shell-tempered pottery from Caverna da Pedra Pintada,
strongly support the presence of pottery use within early Holocene shell-fisher occupations.
However, it also queries potential shortcomings in Roosevelt’s (1995) account: the fact that a
TL date for a sand-tempered shard in the Paituna component is congruent with mid Holocene
or younger occupations in Caverna da Pedra Pintada may indicate that soot-stained sand-
tempered wares at the site are related to mid Holocene shell-fisher occupations or, even more
plausibly, are intrusive from the overlying Aroxí occupation. In addition, the fact that the
surface decoration of Taperinha shards is similar to the Colombian Barlovento period pottery
(Meggers 1997), which dates no earlier than the beginning of the 4th millennium BP (Oyuela-
Caycedo and Bonzani 2005), may indicate that some shards, specifically decorated ones, are
intrusive from later occupations. If these interpretations and precisions are correct, they may
have important implications for understanding the extent to which early Holocene ceramic
shell-fishers represent the earliest sedentary occupations in the Amazon basin.
In his post-humously published synthesis, Williams (2003) offered a provoking model for
the adoption of pottery and agriculture in Guiana. He suggested that pottery from ceramic
shell-fisher occupations, dated as early as 4.5-4.3 cal kyr BP, made use of coarse tempers –
shell and sifted rock – that limited the efficacy of ceramic vessels as fire-worthy utensils. He
argued that only as Barrancoid ceramists had expanded into a region inhabited by incipiently
ceramic Alaka phase shell-fishers, theoretically introducing the cultivation of root crops, these
coarse tempers had been abandoned in favour of finer-grained quartz sand, in turn permitting
the manufacture of vessels that were appropriate to meet the processing needs of manioc
preparation. There is a compelling logic to this argument that potentially helps to place the
early Holocene ceramic remains from the lower Amazon into a broader perspective. As argued
previously, at Caverna da Pedra Pintada only shell-tempered pottery appears to truly date to
the early Holocene whilst soot-stained sand-tempered shards might well be intrusive. At
Taperinha (Roosevelt et al. 1991), early Holocene pottery is characterised by the use of grit
and shell as temper. These technological features relate these finds to the older Mina tradition
pottery of the Salgado littoral. It can be suggested that the presence of coarse-tempered pottery
and the use of boiling stones (Roosevelt et al. 1991), therefore, hint at important technological
limitations for the processing of foodstuffs, including here consistent use of vessels for
processing edible plant parts showing high levels of toxicity (cf. Oliver 2001). The implication
I cautiously advance here echoes Roosevelt’s (1999b) suggestion that shell-fisher pottery
constitutes a Ceramic Archaic: the sheer presence of pottery in shell middens and cave sites
Chapter 3. The Roots 53
may not be the best indicator for the presence of sedentary lifestyles based on a horticultural
subsistence.
A shell-fisher lifestyle survived in the Amazon basin after the onset 4th millennium BP
terra firme ceramic occupations (see Section 4.2 below). For instance, in the lower Xingú
river, Mina tradition pottery is found in the PA-AL-18 shell midden, dated as early as 3.7-3.3.
cal kyr BP, i.e. towards 1610-1300 BC. These occupations are followed, possibly with an
important gap in the first millennium BC, by indications of a continued shell-fisher
subsistence emphasis in the first centuries of the 1st millennium AD (Perota 1992; Perota and
Botelho 1992). Shell-tempered pottery is also found in old components of specific regional
sequences throughout the Amazon basin (Brochado and Lathrap 1982; see also Lathrap 1970a;
Lathrap et al. 1985): the shell-tempered minority ware dated as early as 4.0-3.7 cal kyr BP in
the Cobichaniqui midden, PAC-14 site, upper Pachitea basin (Allen 1968); the 4.1-3.7 cal kyr
BP shell-tempered Bacabal phase pottery found in the hitherto preceramic RO-PN-08 shell
midden of the Pantanal do Guaporé (Miller 1999); the undated shell-tempered wares
underlying Early Tutishcainyo pottery in the middle Ucayali (Lathrap 1970b; Brochado and
Lathrap 1982; Lathrap et al. 1985); the undated Castalia phase shell-tempered pottery from
Ponta do Jauarí (Hilbert 1968); and, perhaps, undated shell-tempered pottery – the Kamihun
style – of the Huasaga basin (DeBoer et al. 1977b).
It is difficult to establish whether these findings constitute evidence for a ceramic shell-
fisher horizon. If they really do, a number of questions should be asked: Did pottery-making
techniques expand among pre-existing shell-fisher communities and/or did groups which
made shell-tempered pottery expand through the river network after the mid Holocene sea-
level transgression? Or is it the case that pottery associated to shell-fisher occupations is
unrelated to the latter appearance of terra firme ceramic complexes? Opinions vary and have
varied (Lathrap 1977; Brochado and Lathrap 1982; Meggers and Evans 1983; Meggers 1997;
Roosevelt et al. 1991; Roosevelt 1999b; Lima et al. 2006; Neves 2008). One way or another,
shell-fishers of the Ceramic Archaic do not appear to signal the onset of sedentary lifeways
based on the cultivation of edible plant stuffs.
4. REVISITING THE AMAZONIAN FORMATIVE
4.1 The Tropical Forest Cultures of Amazonia
Literature reviewed in Chapter 2 of the dissertation shows that discussions have moved on
a great deal since the days in which the expression ‘Tropical Forest Culture’ identified small,
semi-sedentary to sedentary, autonomous human communities reliant on hunting and shifting
cultivation. The location of most ceramic archaeological sites near sources of aquatic fauna
Chapter 3. The Roots 54
strongly suggests that much of the discussion about protein limitation (Gross 1975; cf.
Beckerman 1979) assumes a non-riparian subsistence focus that pays insufficient attention to
riverscapes as the most attractive locales for inhabitation (see also Denevan 1966b; Denevan
1996; Carneiro 1970; Chernela 1989; Gragson 1992). The mono-cultural, spatially-extensive,
and long fallow character of contemporary shifting cultivation (Beckerman 1987) is argued to
be a recent phenomenon (Andrade 1988; Denevan 1992b): at least on the eve of European
contact, terra firme gardening would have focused on a much wider repertoire of cultivars,
employed a short fallow and spatially-intensive strategy, and relied on organic amendments,
in-field burning, and burning of fringe vegetation to enhance crop productivity (Denevan
1998, 2004; see also Piperno and Pearsall 1998; Hecht 2003; Oliver 2008). Moreover,
Lathrap’s (1977) insightful discussion of the house garden emphasises the relationship
between the management of domestic refuse and small-scale cultivation of a diverse set of
edible or useful plant stuffs (see also Anderson 1952; Rindos 1984; Peters 2000; Oliver 2001),
a dynamic that I have argued is incipiently documented in some of the better studied early
Holocene preceramic sites. Finally, research highlights several important indigenous practices
and bio-social dynamics that can be considered part of the ceramic horticulturalist complex of
Amazonia: the gathering of forest foods (Rival 1998; Clement et al. 2008); forms of itinerant
cultivation associated with forest gardens (Posey 1984); management of forests at different
stages of succession (Denevan and Paddoch 1987; van der Hammen 1992; Peters 2000); and
the use of landscape legacies such as anthropogenic soils (Smith 1980; Andrade 1988;
German 2001, 2003; Fraser et al. 2008), anthropogenic concentrations of fruit trees (Balée
1989, 1994) and soil seed banks (Pujol et al. 2007).
If we cautiously employ these insights to envision human communities of the Amazonian
Formative, we will forcefully conclude that such groups may have ranged from mixes of
foragers and itinerant horticulturists, perhaps resembling specific ethnographic exemplars
(Denevan 1971; Harner 1972; Johnson 1983; Descola 1994; Cipolletti 1997; Rival 2002; see
Meggers 1971; 1996), to larger groups whose settlements controlled significant concentrations
of aquatic resources and/or were in good command of agriculturally-apt terra firme or
floodplain soils (Denevan 1966b; Denevan 1996; Lathrap 1970b; Carneiro 1970; Myers
1973). To ascertain that a range of situations must have existed in the pre-Columbian past
neither denies that some ethnographic foragers or trekkers may descend from large pre-
Columbian societies (Lathrap 1968b; Balée 1994), nor suggests that the appearance of
sedentary lifestyles in the region should be understood as invasions or migrations of
agricultural ceramists into a landscape peopled by non-agricultural hunter-gatherers (cf.
Steward 1948a; Meggers 1997). Instead, it argues that hierarchical social systems which
permitted the maintenance of different lifestyles may have characterised some regions of
Amazonia (Carneiro 1970; Ramos 1980; Betendorf, cited in Porro 1996b:30), and that
Chapter 3. The Roots 55
switching between different lifestyles as circumstances required (Lathrap et al. 1987; Meggers
and Danon 1988; see Reid 1979; Fausto 2001 for ethnographic discussion) was certainly an
alternative also during the pre-Columbian past.
In my view, a model of interest to think about the Amazonian Formative is Nimuendajú’s
(1950) account of the peopling of the Upper Negro basin. This model suggests that the
expansion along the drainage network of strong, territorially-expansive groups resulted in the
encapsulation of weaker parties in interfluvial areas, thereafter followed by a shaping of inter-
ethnic relations that ranged from the maintenance of patron-client bonds to the co-option of
original inhabitants into the ethnically-defined spheres of sociality of newcomers (Koch-
Grünberg 1906; Goldman 1963; Silverwood-Cope 1975; Reid 1979; Jackson 1983). If we
employ this model to think about the past with due attention to the likely horticultural
character of many preceramic and ceramic groups, it can be envisioned that subsistence
complexes based on the use of pottery and horticulture expanded through the landscape and
gained the upper hand in terms of social and territorial control compared with preceramic
horticulturists, ceramic shell-fishers, mobile foragers and, eventually, other ethnically-distinct
groups of ceramic horticulturists. The widespread adoption of sedentary lifestyles in the basin,
therefore, probably came about as a result of both immigration of communities and cultural
transmission of crops, pots and agricultural know-how, the latter establishing conditions for
demographic growth among ‘receiving’ groups that increased both the size of radiating
populations and their overall impact on the landscape.
4.2 Interaction spheres of the early Formative
As discussed in Section 2 of this chapter, different palaeo-environmental records show that
the Amazon basin experienced increasingly more humid conditions after the mid Holocene.
This trend, however, is punctuated by dry spells of 300-600 years associated with significant
sea-level rise events. The latter are dated to around 4.2–3.7 cal kyr BP and 2.7–2.1 cal kyr BP,
that is, around 2200-1700 BC and 700-100 BC (Suguio et al. 1985; Angulo et al. 2006)7. It is
within this time frame that the earliest archaeological evidence for ceramic terra firme
occupations – the early Amazonian Formative – is recorded in the region. This evidence can
be grouped into two sets of archaeological occurrences – one from the western and one from
eastern half of the basin – that are separated by archaeologically-uncharted territory (see
Figure 14, for the location of sites discussed in this section). Archaeological evidence suggests
that these two regions represent broad interaction spheres whose reach extended to areas
located, respectively, to the west and north of the Amazon basin proper.
7 Although to some it may appear inconsistent, I have deliberately opted to present all calibrated age ranges in
years BC in this and the following sections.
Chapter 3. The Roots 56
In broad outline, these two spheres can be summarised as follows. The western sphere is
present in the lowlands east of the Andes from as early as the 3rd to 2nd millennium BC and
lasts until the final centuries of the 1st millennium BC. It tracks relations between peoples of
the Pacific coastal lowlands, the Andean highlands of Ecuador and Peru, and groups
inhabiting the Ecuadorian and Peruvian tributaries of the Marañón river (Allen 1968; Lathrap
1970b; Morales 1992, 1995; Rostain 1999a,1999b; Salazar 1999; DeBoer 2003; Valdez et al.
2005). Some of its ceramic complexes share an emphasis on inflected vessel shapes and
folded rims that typologically recalls Valdivia pottery of the Pacific lowlands (Meggers et al.
1965; Hill 1975). The eastern sphere, in contrast, tracks the appearance of ceramic complexes
in the northern and eastern half of the Amazon basin. These complexes emphasise globular
vessel shapes and the use of fine line incision for surface decoration, formal characteristics
which can be traced back to the Hormigoid tradition in Colombia (Meggers, 1997 #4334, see
also Roosevelt 1989a, cited in Rouse 1992:37). Like the western sphere, its appearance in the
landscape dates to around 2000 BC. However, its overall duration does not extend beyond c.
1000 BC, apparently due to warmer conditions (Meggers and Danon 1988) and/or higher sea-
level effects (Angulo et al. 2006). These two spheres are each examined in further detail
below. 8
The western sphere is one of trans-Andean interaction (Lathrap 1970b; Myers 1981,
1988b; DeBoer 2003; Valdez et al. 2005). It can be traced from techno-stylistic similarities
between ceramic complexes dated perhaps as early as c. 2850 BC across different regions of
the western Amazon. A mandatory starting point is archaeological evidence from Santa Ana-
La Florida, a site located along a fluvial terrace of the upper Mayo-Chinchipe river (a tributary
of the Marañón), at about 1000 m asl in the Ecuadorian Montaña. Valdez et al. (2005) report
ceramic vessels decorated with punctuations and parallel incisions associated with mounds
structures dated between 2840-2340 BC and 2350-2190 BC. Stylistically, these remains are
described as similar to the middle and later Valdivia phases (i.e. theoretically starting around
2800-2400 BC, see Zeidler 2003) and to 1800-1300 BC Catamayo A phase ceramics from the
Loja province in the highlands. At Santa Ana-La Florida, human burials associated with
charcoal dating to 2140-2020 BC are accompanied by turquoise/malaquite ornaments,
Strombus sp. remains, delicately decorated stone bowls, ceramic bottles, and an anthro-
zoomorphic ceramic vessel, pointing to contacts with the Pacific coast. The presence of stone
bowls and Strombus shells, however, also brings to mind finds by Rojas Ponce in the Peruvian
Marañón (Lathrap 1970b:107-108, plates 26, 27) and stone bowls of the Cotocollao site near
Quito. Valdez et al. suggest that these ceramic remains stylistically resemble Machalilla phase
pottery from the Pacific lowlands (Meggers and Evans 1962; Meggers et al. 1965; Meggers
8 A third region, the upper Madeira basin (Miller 1992a,1992b; Miller 1999), records ceramic occupations as
early as 980-800 BC, overlapping the youngest age range assigned to preceramic dark earths of the Massangana phase, ca. 900-770 BC. Aspects of the upper Madeira sequence will be discussed in Section 4.3.
Chapter 3. The Roots 57
1966), presently accepted to date between 1430-830 BC (Zeidler 2003), as well as IIb phase
pottery of the highland Cotocollao site, dated to 800-500 BC (Villalba 1988). Considered from
the vantage point of Manihot microfossils dated to the mid Holocene and later (e.g. Chandler-
Ezell et al. 2006), Valdez et al. (2005) are no doubt right to suggest that the Ecuadorian
Montaña played an important role in the development of agrarian societies of the Andes and
Pacific lowlands.
To the south, a series of similarly early Formative complexes are reported in the
Ecuadorian Amazonian lowlands by Porras (1975; 1987b). Among these is the Pastaza phase,
a complex defined from sites in the Huasaga basin. It consists of an array of vessels – globular
bowls, open bowls with slightly concave walls, and large ollas with a constricted neck – which
are notorious for a lack of any evidence of inflected or carinated shapes. Pottery apparently
bearing some resemblance to the Pastaza phase, a style described as Kamihum, is described by
DeBoer (1977a) on the Peruvian side of the Huasaga basin. It would appear that these
complexes indicate a parallel and slightly earlier ceramic tradition that, like the earliest
Peruvian highland pottery and some complexes of eastern Amazonia (see below), does not
emphasise the use of inflected vessel shapes. Notwithstanding, the stratigraphic position of
Pastaza materials is uncertain (Myers 1988a:50) and most commentators consider Porras’
early dates controversial (see Rostoker 2003).
Better documented evidence of Formative lifestyles comes from the Sangay basin, also in
the Ecuadorian Montaña. Recent research has re-examined Porras’ (1987a) report of large
Early Formative mound complexes, especially the Sangay site. Whilst it has not been possible
to re-evidence Porras’ pre-Upano phase, a ceramic complex putatively dated to 2750-2520 BC
(Rostain 1999b:58-59; Salazar 1999:186-187), the site of Huapula (as it is now known), has
produced evidence of an extensive and well-structured settlement in which dark anthropogenic
soils developed (R. Bartone, com. pers.), dense ceramic middens accumulated, and series of
rectangular or oval mounds arranged around public squares were built between 700 BC to AD
400. The earliest phase of occupation is characterised by the Upano ceramic complex, which
includes carinated vessel shapes with reinforced rims and the use of red banded incised
decoration, the latter better known at sites from higher elevations (Bruhns et al. 1990; Bruhns
2003). Huapula is interpreted as evidence for the development of social complexity and
ceremonialism in the Ecuadorian Montaña before the start of the Christian era (Rostain
1999a,1999b; Salazar 1999; Roosevelt 1999a).
To the south, an important region still in close proximity to the Andes is the upper
Pachitea valley, in the Peruvian Amazon. At the PAC-14 site, Allen (1968) reports what
commentators (e.g. Myers 2004) have suggested may be the oldest description of an
Chapter 3. The Roots 58
anthropogenic dark earth expanse with ceramic remains in the Amazon basin. At PAC-14, a
minority of inflected vessels shapes in shell-tempered Cobichaniqui wares that date towards
2270-1770 BC show sharp contrasts with the earliest pottery from coastal and highland Peru
(see e.g. Burger 1992:58-9) and most likely find their ultimate antecedents in deep bowls with
thickened inflected rims recorded in 2870-2360 BC Valdivia III pottery (see Hill 1975: Plate
V, Figs. 36,7). It is noteworthy that Cobichaniqui pottery appears as an intersection between
trans-Andean stylistic features and shell-fisher tempering modes, and it is indeed plausible
that it represents contact between highland and lowland groups. This point is underscored by
pottery of the Pangotsi complex, which follows Cobichaniqui and dates between 1750-1420
BC. Pangotsi pottery shows decoration modes – closely-spaced parallel lines made of small
punctuations, zoned decoration inscribing punctuations, concentric rectangular motifs
executed by incision and excision, and the use of four-colour slip – that can be compared with
complexes of the Ucayali basin (Lathrap 1970b), the La Peca phase at the Bagua site (Shady
1992:349), and Valdivia III-IV pottery (Hill 1975, Plate V, Fig. 28), the latter dating
minimally to the third millennium BC (Zeidler 2003). Pangotsi pottery is found at PAC-14
and a number of nearby sites, an increase in occupation density that Allen (1968:342-348)
interpreted as a sign of population growth in the region.
Early ceramic complexes of the upper and middle Ucayali basin begin to document the
extent to which the western interaction sphere is present in the lowlands proper. The earliest
tradition in the sequence is the Tutishcainyo tradition, found at small sites located along rivers
and on the margins of oxbow lakes. The tradition comprises two ceramic complexes,
Tutishcainyo and Shakimu, each divided into an early and a late phase (Lathrap 1970b;
DeBoer 1975b). Early Tutishcainyo pottery shows zoned decoration circumscribing finely-
incised, parallel or cross-hatched lines, often with post-fire red pigment adorning the body or
labial and mesial flanges of sharply inflected vessels. It also includes double-spouted bottles, a
Formative vessel shape found in Andean coastal contexts (Burger 1992; Bruhns 2003), in the
Colombian Formative (Cardale Schrimpff 2005b) and in the Venezuelan Barrancoid (Rouse
and Cruxent 1963). The onset of the Tutishcainyo tradition has to my knowledge never been
dated radiometrically but can be argued to be approximately co-eval to, or slightly younger
than, the 2460-2040 BC Waira-jirca phase at Kotosh and the onset of zoned hachured
decoration in Valdivia VII pottery (Hill 1975), which is younger than 2580-2140 BC and older
than 1950-1800 BC (Zeidler 2003). Based on the presence of Ayangue Incised ‘tradeware’
(Lathrap 1970b:91; Myers 1988b:55), it may be argued to be co-eval with or slightly earlier
than the Ecuadorian Machalilla phase (Meggers and Evans 1962; Meggers et al. 1965;
Meggers 1966), which as noted previously is dated to 1430-830 BC (Zeidler 2003:494). Both
zoned decoration and the use of labial and mesial flanges disappear in Late Tutishcainyo,
being replaced by the consistent use of often nicked carinations in the inflected angle of vessel
Chapter 3. The Roots 59
bodies – characteristics also present in Machalilla. Early Shakimu times dates to 950-540 BC
(Lathrap 1968a, 1970b) in the middle Ucayali and 1120-880 BC in the upper Ucayali
(DeBoer 1975b). According to Lathrap (1970b) Shakimu is characterised by the disappearance
of nicked carinations, the appearance of excision and incised parallel lines, the adoption of
bell-shaped vessels that are reminiscent of Saladoid exemplars, a ‘return’ to the use of mesial
flanges, and the incorporation of decorative motifs and extraneous vessel shapes that suggest
relations with the Chavín horizon of the highlands. The undated Late Shakimu complex shows
a simplification of vessel shapes, the abandonment of Chavín-like motifs, the disappearance of
double-spouted bottles, and the adoption of rare examples of widely-spaced zoned
punctuations. Tutishcainyo tradition sites are generally regarded as small occupations not
outlasting 100 or so years9.
The eastward extent of the western interaction sphere is tracked by the widespread
distribution of spouted bottles similar to those found in the Tutishcainyo tradition and with
correlates in the Andean highlands and Pacific lowlands. DeBoer (2003) has recently
summarised known occurrences in the Amazon basin, noting their distribution in a wide area
located between the Sangay/Huapula site and the Curanja river, the latter a tributary of the
upper Purús. Among the most interesting examples are double-spouted exemplars found at
two undated archaeological sites of the Chambira river basin, a tributary of the Marañón, in
association with sand-tempered pottery decorated with thin incised hachure of the Chambira
phase and anthropomorphic ceramic figurines that recall Valdivia precedents (Morales 1992,
1995). Morales compares these materials to Porras’ (1987a) Upano phase material from the
Sangay/Huapula site, which – given the recent dates produced at this site – would place the
Chambira phase around 710-200 BC and align it with the Shakimu complexes of the Ucayali
basin. It is noteworthy, however, that unlike other ceramic complexes of the western sphere,
Chambira phase pottery emphasises globular rather than inflected vessel shapes. This might
suggest that ceramists from the eastern half of the basin had expanded to the western half of
the basin very early in time.
The second interaction sphere – the eastern one – signals the appearance of sedentary
ceramic horticulturists in the northern and eastern half of the Amazon basin. These early
Formative complexes include: the Aroxí pottery of the Caverna da Pedra Pintada rockshelter,
dated between 2200-2000 and 1640-1490 BC (Roosevelt 1995; Roosevelt et al. 1996;
Roosevelt 1999b; Roosevelt 2000); the older pottery from Parauá, on the Tapajós river, dated
between 2410-2130 BC and 940-810 BC (Gomes 2008); the earliest two complexes of Marajó
9 It is worth pointing out that Lathrap (1970b) saw the succession between these complexes as evidence for a
shift in the boundary between potters of different ceramic lineages. For instance, the suggestion that mesial flanges ‘return’ can be understood as a re-occupation of the same locales of groups whose pottery complex show an evolutionary link with displaced older ones. A strinkingly similar example, the relationship between Açutuba and Guarita phase pottery (Lima et al. 2006; see also Lathrap 1970a), will be discussed in Chapter 4.
Chapter 3. The Roots 60
Island, the Ananatuba and Mangueiras phases, both from low, oval-shaped refuse mounds
dated to around 1500 to 1000 BC (Castanheira site) (Simões 1969; Meggers and Danon 1988);
and pottery from stratified levels dating as early as 2200-1740 BC (Magalhães 1993, 1995)
and 1260-970BC (Hilbert 2005) at the Gruta do Gavião rockshelter. All of these share an
emphasis on tecomate-shaped globular vessels, in some cases with simple linear incisions
along the rim. Roosevelt also reports flat platters similar to manioc budares or maize comales
as part of the Aroxí assemblage.
Less clear or more distant exemplars of the northern interaction sphere include decorated
shards of sand-tempered Taperinha pottery (Roosevelt et al. 1991; see Meggers 1997 and
Section 3.3 of this chapter); undated but typologically-related ceramic wares from the Ponta
de Jauarí shell midden (Hilbert 1968); possible remains at the Açutuba site dating to 1220-
1000 BC (Petersen et al. 2004); ‘pre-Pocó’ wares dated around 1610-1500 BC and 1380-840
BC (Hilbert and Hilbert 1980) in the Nhamundá-Trombetas area; fibre-tempered wares dated
to 1510-1380 BC at the Fortaleza site in the Uaupés region (Neves 1998a); and reports of
early Formative fibre-tempered globular bowls with reinforced rims, flat platters, and fire dogs
reportedly immediatedly above the preceramic 3010-2890 BC Tubabonipa component of the
Abeja site (Mora et al. 1988:ff3,4). Remains that might be grouped into this interaction sphere
are not limited to the Amazon basin: Cedeñoid pottery of the Agüerito site on the middle
Orinoco (Zucchi et al. 1984; Zucchi and Tarble 1984) and the 1450-850 BC Galipero complex
discussed by Barse (1999), can most likely also be included.
Both Amazonian and Orinocan complexes appear to relate to the Hormigoid tradition of
the Colombian Caribbean littoral (Roosevelt 1989a, cited in Rouse 1992:37; Meggers 1997).
The Hormigoid tradition is better known for the type site of Puerto Hormiga (Reichel-
Dolmatoff 1965; Oyuela-Caycedo 1995) and, more recently, San Jacinto 1 (Oyuela-Caycedo
and Bonzani 2005), but also includes important latter developments such as Barlovento,
Canapote and Monsú (Reichel-Dolmatoff 1985, 1997 (1986)). Amazonian early Formative
assemblages show some very broad but potentially meaningful typological similarities. For
instance the Caverna da Pedra Pintada Aroxí wares, including here Paituna sand-tempered
wares that I have argued are Aroxí intrusives (see Section 3.3), show globular and flat platters,
the use of u-shaped curvilinear incision, single and parallel lines below vessel rims, and deep
medium-sized round-to-oval punctuations. These features are also observed in the ‘Coarse
Punctuate’ and ‘Smooth Grooved’ types of the Macaví period at the Colombian site of Monsú
site. The Macaví period is cross-dated to around 2500-2000 BC (e.g. Reichel-Dolmatoff
1985:90). Along similar lines, Meggers’ (1997:27-8) has suggested that decorated shards of
sand-tempered Taperinha pottery are similar to Barlovento period pottery, the latter a younger
representative of the Hormigoid tradition which can be cross-dated at Canapote to between
Chapter 3. The Roots 61
1970-1690 and 1380-1040 BC (Oyuela-Caycedo and Bonzani 2005). Indeed the Ananatuba
phase, which dates to 1500-1000 BC (Simões 1969; Meggers and Danon 1988), shares with
Macaví period and Paituna (Aroxí) pottery the use of punctuate decoration (e.g. Meggers and
Evans 1957: Plates 42, b-c and 47-h), the style and design of hachured decoration (cf. Reichel-
Dolmatoff 1985:97-8; Meggers and Evans 1957: Plate 39, c-e), and the stamping of outlined
circles (cf. Reichel-Dolmatoff 1985:85-6; Meggers and Evans 1957: Plate 41, e; Meggers
1997:26).10
The preceding summary demonstrates that consistent evidence exists for the presence of
ceramists in the Amazon basin from around 2000 BC onwards. The majority of the
archaeological contexts reviewed are described as small sites that lack the well-developed
anthropogenic dark earths characteristic of late pre-Columbian history (Chapter 2).11 The
lifestyles of these communities have generally been considered to be similar to
ethnographically-recorded Tropical Forest Cultures (e.g. Meggers and Evans 1957; Lathrap
1970b; Roosevelt 1999b) but the fine detail of these reconstructions vary. Recently DeBoer
(2003) has suggested that the overall volume and vessel type distribution of lowland
complexes of the western sphere does not resemble the kind of large feasting vats that are
observed ethnographically and which Lathrap (1970b) argued represented clear evidence for
manioc consumption and the use of fermented drinks. Deboer points out that early Formative
vessel were either not used for such occasions and/or represent domestic or even transportable
containers. Along similar lines, Gomes’ (2008) analysis of the Parauá pottery argues that
small vessel volumes and the use of paste tempers that result in lighter vessels are features
consistent with relatively mobile horticulturist groups. Her point is reinforced by reports of
plant macrofossils identified as inajá (Maximiliana maripa), murumuru (Astrocaryum
murumuru), buriti (Mauritia flexuosa) and ubim (Geonoma macrostachys). These plant fossil
remains contrast with Manihot phytoliths reported from 1st millennium AD anthropogenic
dark expanses of the same region.
Whilst data to affirm, supplement or contradict these accounts are lacking, it is in my view
useful to remember that problems of preservation and taxonomic resolution do affect the
identification of Manihot microfossils and, to a lesser extent, the survival of Zea mays starches
(Chandler-Ezell et al. 2006). If a Manihot ‘founder effect’ took place in southwest Amazonia
towards the mid Holocene (see Section 3.2 of this chapter) and Manihot microfossil are
10 Shared vessel shapes and surface decoration between the Ananatuba and Mangueiras phases at Marajó Island
suggest both are evolutionarily related (Brochado 1980; see also Schaan 2001). This permits a cautious cross-dating of the zoned-hachured decorated clay pipes and globular vessels reported by Hilbert (1968:291, Tafel 7, 296, Tafel 12) at the Ponta do Jauarí shell-midden. It can thus be argued that the latter site records the interaction between Hormigoid-affiliated ceramists and perhaps late Mina tradition ceramic shell-fishers; this in addition to the presence of later-day Barrancoid ceramists (Lathrap 1970b; Lathrap 1970a).
11 In some cases, stratigraphic descriptions do suggest various forms of soil enrichment (Meggers and Evans 1957; Allen 1968; Simões 1969; Lathrap and Oliver 1987).
Chapter 3. The Roots 62
present in Valdivia occupations and at the Abeja site around this time, it seems unlikely that a
mere millennia later people in western and eastern Amazonia did not use manioc tubers.
Consistent use of Zea mays, on the other hand, is recorded in pollen signals of both western
and eastern Amazonia: the early occupation of the Ecuadorian Montaña is chronologically
consistent with Zea mays pollen recorded around 3300 BP at the L. Ayauchi core (Piperno
1990; Bush et al. 1990); slightly more recent occupations of the Ucayali basin resonates well
with Z. mays pollen dated to around 1750 BC at the L. Gentry core (Bush et al. 2007), which
is located near the border with the Bolivian Amazon (see Figure 12); and the age of Formative
occupations in the lower Amazon is congruent with Z. mays phytoliths and pollen dating to
2080 BC and 1650 BC at the L. Geral core (Piperno and Holst 1998; Bush et al. 2000; Bush et
al. 2007). Based on these observations I would argue that early Formative communities of the
eastern and western halves of the Amazon basin probably resembled more the ethnographic
pattern of the western Amazonian Montaña (Denevan 1971; Meggers 1971; Harner 1972;
Descola 1994; Santos-Granero and Barclay 1994; Salick 1997): small, autonomous, relatively
isolated corporate groups that traditionally relied on fishing, hunting, the collection of fruits,
the consumption of maize beer, and – among others – the cultivation of sweet manioc.
4.3 The Ceramic Formative in the middle and lower Amazon
An event of sea-level rise and warmer conditions during the first half of the 1st millennium
BC (Suguio et al. 1985; Angulo et al. 2006) sets the stage for the complex mosaic of
archaeological manifestations that characterise the best-known part of the cultural sequence of
eastern Amazonia. These centuries of climatically-induced stress, perhaps coupled with higher
river base levels and dry conditions related to changing precipitation patterns, map on to a
sub-millennial gap in the archaeological record. This gap posits significant questions about
demic continuity between early Formative occupations and those populations that are
increasingly more conspicuous in the archaeological record starting in the final centuries of
the 1st millennium BC (Meggers and Danon 1988; Neves 2008). However, the gap is more
clear and/or pronounced in the broader region of the Amazon floodplain than it is in the
Western Amazon (Lathrap 1970b; Morales 1992, 1995; Rostain 1999b) and the upper Madeira
region (Miller 1992a,1992b; Miller 1999), a contrast whose significance will resurface below.
Starting in the final centuries of the 1st millennium BC, the landscape of eastern Amazonia
sees a steady increase in riparian or lake-side sites that are characterised by large expanses of
anthropogenic dark earths and stratified pottery remains of recognisably different styles. These
sites mark the onset of evident and widespread modifications to the landscape, attest to
increasing populations, suggest far-flung interaction among groups in the overall region, and
may yet highlight patterns of territorial contestation between larger social units (Lathrap
1970b, 1973; Myers 1981; Eden et al. 1984; Heckenberger et al. 1999; Petersen et al. 2001;
Chapter 3. The Roots 63
Neves 2008). Indeed, as discussed in Chapter 2, sites from this period, especially from the
second half of the 1st millennium AD, are considered evidence for growing populations and
increasing social complexity in the Amazon floodplain (Roosevelt 1999a; Lima et al. 2006).12
Interesting as these developments are, my aim in this section is to offer a set of broad
remarks about the spatial and temporal distribution of the ceramic complexes of the middle
and lower reaches of the Amazon basin (see Figure 15 for the location of archaeological sites
and regions discussed in this section). My purpose is to highlight spatially-extensive relations
of past populations, identify broad patterns in dynamics of anthropogenic landscape
transformation, point to sources of specific techno-stylistic lineages, and – in some cases –
hint at relations between ceramic traditions and language families. An outline of the broader
picture can be offered: towards the final centuries of the 1st millennium BC, the lower and
middle Amazon witness the appearance of groups whose pottery shows clear affinities with
the Orinocan Barrancoid series and which can be variously classified into the incised-rim or
modeled-incised traditions. In the lower Amazon, sites record the subsequent expansion of
groups whose pottery can be classified into the incised-punctuate horizon, in this case with
clear affinities to the Venezuelan Arauquinoid series. The middle Amazon, which also
witnesses the appearance of groups whose pottery can be classified into the incised-punctuate
horizon, eventually sees a widespread takeover by groups whose pottery can be affiliated to
the Amazonian Polychrome tradition.
In more detail, the earliest ceramic complexes dated from the last centuries of the 1st
millennium BC to the first half of the 1st millennium AD share a number of techno-stylistic
features: compared to early Formative pottery, these complexes share an expanded array of
vessel shapes (including ceramic platters interpreted as manioc griddles, see Lathrap 1970b;
Reichel-Dolmatoff 1986; cf. DeBoer 1975a; Perry 2005), use of reinforced rims and/or
flanges, and a characteristic use modeling, incision, excision, and polychrome painting
(Hilbert 1968; Hilbert and Hilbert 1980; Zucchi 2002; Lima et al. 2006). The widespread
distribution of these features along the middle and lower Amazon during this time range attest
to intense social interaction: instances include the late 1st millennium BC and early 1st
millennium AD Pocó phase of the Nhamundá-Trombetas basin (Hilbert and Hilbert 1980),
early 1st millennium AD modelled-incised wares characterised as the Uatumã and Silves
phases between the mouth of the latter and Manaus (Simões and Machado 1987, 1984),
modelled-incised wares from the undated Ponta do Jauarí shell midden (Hilbert 1968), and the
late 1st millennium BC to late 1st millennium AD Açutuba and Manacapuru phases in the
Negro-Solimões confluence area (Hilbert 1968; Heckenberger et al. 1999; Petersen et al.
12 Some data suggests that the political organisation of these societies was characterised by asynchronous peak
moments throughout the region, resulting in cyclical developments of complex organisation and/or heterarchical arrangements of social power (Roosevelt 1999a; Schaan 2004; Neves and Petersen 2006; Neves 2008).
Chapter 3. The Roots 64
2004; Lima et al. 2006). Other complexes that include modeled-incised characteristics are
found along the main reaches of the Amazon from the mouth of the Madeira to Parauá, on the
lower Tapajós (Lathrap 1970b; Hilbert and Hilbert 1980; Roosevelt 1990; Roosevelt 1999b;
Gomes 2008). The north-westernmost extent appears to be the mid 1st millennium AD Japurá
phase pottery, which is found at the Japurá-Caquetá border (La Pedrera, Mangueiras), between
Brazil and Colombia (Hilbert 1968; von Hildebrand 1975; Myers 2004).
Most of the preceding ceramic complexes show indisputable affinities with ceramic
complexes of the Barrancoid series (Rouse and Cruxent 1963), the latter encompassing
Barrancoid complexes from the lower and middle Orinoco (e.g. Rouse and Cruxent 1963;
Rouse 1978; Sanoja and Vargas 1978; Sanoja 1979; Roosevelt 1980; Roosevelt 1997b; Barse
1989, 1999), the Mabaruma and sibling complexes in the Guianas (Evans and Meggers 1960;
Boomert 1993; Versteeg 1985, 2003a; Williams 1992, 2003), and – more distantly – the
Malambo complex in the Colombian Caribbean (Angulo Valdés 1962, 1981, 1992). Lathrap,
who noted affinities between some of these, Amazonian occurrences, and Hupa-iya pottery
overlying a small late Shakimu midden in the Ucayali basin,13 argued that all could be
classified into the Amazonian Barrancoid tradition and hypothesised that older prototypes for
both the Ucayali and Orinocan exemplars would be found in the middle and lower reaches of
the Amazon river (Lathrap 1964; 1966; 1970b). Decades of research in the latter regions
(Hilbert 1968; Hilbert and Hilbert 1980; Heckenberger et al. 1999; Neves 2003; Lima et al.
2006) have failed to detect older exemplars. Therefore, many scholars accept Meggers and
Evans (1983) classification of these complexes as part of the incised-rim horizon or tradition,
most accord chronological pre-eminence to the early 1st millennium BC lower Orinoco
complexes with respect to Amazonian exemplars (cf. Myers 2004), most derive Orinocan
wares from the Hormigoid tradition of the Colombian Caribbean (see Sanoja and Vargas
1978; Rouse 1992; Meggers 1997; Neves 2008), and some see the widespread distribution of
these complexes in the Guianas, Orinoco and eastern Amazon, as well as the Caribbean
islands, as evidence for an expansion of Arawakan speaking populations into the Amazon
basin and the Caribbean (Rouse 1983, 1992; Zucchi 1991, 1992, 1993, 2002; Heckenberger
2002).
In the lower Amazon region, modeled-incised complexes are followed by the appearance
of denser sites with pottery that can be classified into Meggers’ and Evans’ (1983) incised-
punctuate tradition. Most prominent are pre-contact Konduri wares overlying Pocó pottery in
the Nhamundá-Trombetas area (Hilbert and Hilbert 1980), and early 2nd millennium AD
Santarém pottery at large expanses of dark earths near Santarém city; the latter appear as
archaeological correlates of the ethnohistorically-reported Tapajós chiefdom (Nimuendajú
13 Morales (1992; 1995) has documented a similar occurrence in the Peruvian Chambira river basin: a much
larger and denser midden of modeled-incised, Siamba phase pottery overlies early Formative wares briefly mentioned in Section 4.2 of this chapter.
Chapter 3. The Roots 65
1952, 2004; Palmatary 1960; Roosevelt 1990; Roosevelt 1999a). To the west, a ceramic
complex of the central Amazon region, the Paredão phase (Hilbert 1968), is considered by
some as part of the incised-punctuate tradition (cf. Hilbert 1968; Lathrap 1970b). According to
Neves (2008) this tradition does not represent a rupture with modeled-incised pottery and can
be derived from the same ancient Colombian antecedents. However, most scholars see
immediate similarities between incised-punctuate complexes and pottery of the Arauquinoid
series in Venezuela: Arauquinoid potters have traditionally been associated with the expansion
of maize-cultivating Carib-speaking populations from the central Venezuelan Llanos after
around AD 500 (Rouse 1978; Zucchi 1985; Navarrete 1999). By AD 700, these groups have
expanded to the Guianas at the expense of previous Barrancoid groups (Rostain 2008).
In the central Amazon region, Paredão occupations are followed by pottery of the Guarita
phase, first dated at Coarí, which is classified as part of the Amazonian Polychrome tradition
(Hilbert 1968; Meggers and Evans 1983). According to Neves (2008) by the 12-13th centuries
AD most of the floodplains of the Amazon/Solimões were occupied by villages from different
sizes and in which pottery of the Amazonian Polychrome tradition was produced. Complexes
associated with tradition share the use of grooving and excision, red or white slip, red or
black over white painting, and anthropomorphic urns. It has been traditionally linked to a
radiation of Tupi-Guarani speaking groups (Lathrap 1970b; Lathrap 1972; Myers 1974; Porro
1996 (1981)) although Meggers and Evans (1983) have proposed an ultimate origin in the
Quibor valley Tocuyanoid series of Venezuela. Be that as it may, they consider the AD 400-
1000 Marajoara phase of Marajo Island as the oldest representative of the tradition; other
complexes – Miracanguera at the mouth of the Madeira, Guarita in the middle reaches of the
Amazon, Napo in the Ecuadorian Amazon and Caimito in the Ucayali basin (Meggers and
Evans 1957; Evans and Meggers 1968; Hilbert 1968; Lathrap 1970b; Simões and Corrêa
1987; Simões and Kalmann 1987; see Myers 2004 for a recent review) are dated, or are
presumed to date, to the early 2nd millennium AD and would track an ‘expansion’ of the
tradition upstream. Missing in this ‘transect’ is any evidence for Amazonian Polychrome
tradition pottery in the lower Amazon: even if incised-punctuate pottery from Santarém does
not shy away from polychrome painting (Gomes 2002), both this region and the Nhamundá-
Trombetas area – midway between Guarita and Marajoara phases – lack pottery that can be
affiliated to the tradition (Hilbert and Hilbert 1980; Neves 2008).
As noted, Lathrap argued that modeled-incised pottery originated in the central Amazon
region; he also argued that the Amazonian Polychrome tradition originated in this region and
suggested it had expanded downstream and eventually upstream with speakers of Tupi-
Guarani languages. As will be discussed in Chapter 4, from an archaeological point of view
Lathrap (1970a) had paid attention to Hilbert’s description of Manacapuru pottery and noted
Chapter 3. The Roots 66
the presence of polychrome painting and features that resembled Guarita type wares. This
early use of polychrome painting, most clearly observed in the Pocó (Hilbert and Hilbert
1980) and Açutuba phases (Lima et al. 2006), has been interpreted as an outcome of processes
similar to the amalgamation between Barrancoid and Saladoid influences (ibid.). Polychrome
painting that cannot be readily classified in the Amazonian Polychrome Tradition includes
Koriabo in the Guianas (Rostain 1994; Boomert 2004), the Camani style of Araracuara
(Herrera et al. 1980-1; Eden et al. 1984; see also Myers 2004) and Tivacundo of the Napo
basin (Evans and Meggers 1968).
Guarita-like features in the lower and middle reaches of the Madeira (Simões 1987) and
their potential relation with the archaeological sequence of the upper Madeira basin (Miller
1992a,1992b; Miller 1999), hold interesting clues about polychrome painting. In the latter
case, the ceramic sequence starts around 980-800 BC and reportedly continues uninterrupted
until European contact time. Pottery at sites described as expanses of anthropogenic dark
earths, such as Santo Antônio and Teotônio near Porto Velho are initially dominated by plastic
decoration techniques such as excision, incision and grooving, and later by a more frequent
use of painting that accompanies more common evidence for anthropomorphic urns over time.
Whilst the work of Miller as published is difficult to rely upon, it is not insignificant that a
region considered to be the centre of diversification of Tupian languages (Rodrigues 1986)
shows ceramic features that link early Formative complexes of the Ucayali basin (see Section
4.2 of this chapter) with early 1st millennium AD (Lima et al. 2006) and early 2nd millennium
AD (Hilbert 1968) complexes of the central Amazon region (see Chapter 4): it could suggest
that a radiation of Tupian speakers from south to north inaugurated some of the features that
already Hilbert (1968) noted Guarita pottery displayed and which Napo and Marajoara pottery
lack, especially mesial flanges14. The overall importance of the region for understanding the
broader picture of Amazonia pre-Columbian history is also highlighted by Neves’ (2008)
recent suggestion that the coincidence between a hearth for the Tupian language family, an
early polychrome ceramic sequence in dark earths expanses, and a region where botanical and
genetic evidence suggest the domestication of manioc and peach palm took place, might be
construed to support a correlation between an early expansion of polychrome painting,
agriculture, and Tupi-Guarani languages from the region.
Whilst I have few doubts that the Upper Madeira basin constitutes an early ‘domestication
hearth’ and have argued that Massangana phase sites are important to understand the overall
sequence, I think attention is warranted to the broader picture emerging from the lowlands. It
may be significant to highlight that the earliest accepted dates for ceramic occupations in this
14 In other words that later-day Amazonian Polychrome Tupi-Guarani speakers may have encountered Tupian
speakers that had migrated via the Madeira to the central Amazon region. This model is based on Rodrigues’ (1986) discussion of Tupi, Guarani and Tupi-Guarani languages.
Chapter 3. The Roots 67
region are approximately co-eval with Saladoid pottery for the lower Orinoco, which
traditionally was considered to predate Barrancoid pottery in the Orinoco, the Caribbean, and
the Guianas by a short time span (Cruxent and Rouse 1958; Rouse and Cruxent 1963; Rouse
1992; Boomert 1983; Versteeg 1985). Although controversially early dates in excavations of
the middle Orinoco (Rouse 1978, 1992; Roosevelt 1980; Roosevelt 1997b), a competing
account suggesting the Saladoid must post-date Barrancoid wares (Sanoja and Vargas 1978;
Sanoja 1979; Vargas 1979; Vargas 1981), and Barse’s (2000) recent dating of Howard’s
assemblage to the 1st millennium AD complicates matters greatly, data in the Guianas
(Boomert 1983; Versteeg 2003b), the prior expansion of Saladoid ceramists into the
Caribbean (Rouse 1992), and possible contact between insular (Cedrosan) Saladoid groups
and mainland groups (Versteeg 2003b), leave few doubts that the Saladoid is a valid and
separate ceramic taxon that predates the expansion of Barrancoid pottery to the lower Orinoco
(see Boomert 2000; Gassón 2002 for recent reviews). It is useful to remember that Lathrap
argued that elements of the lower Orinoco Saladoid pottery were shared with the Ucayali
basin Shakimu pottery. Without attempting to revalidate a cardiac model, the evidence from
the Upper Madeira may well end-up supporting an early horizon characterised by zoned
hachured/zoned incised cross-hatched and Saladoid-type polychromy pottery (see e.g. Cardale
Schrimpff 2005b; Castillo and Aceituno 2006, Figura 7), that precedes the expansion of
modeled-incised pottery of the Barrancoid tradition.
Be that as it may, recently Myers (2004) has attempted to link a Lathrapian account of the
expansion of the Barrancoid and Polychrome pottery from the central Amazon to the
distribution of anthropogenic dark earths within the Amazon basin. He has suggested that the
latter represent the introduction of a particular technique of soil management which permitted
the intensification of cultivation in terra firme reaches. Whilst disagreement with some of
Myers’ premises (a central Amazonian hearth for Barrancoid/Polychrome pottery, dark earths
being deliberately-made agricultural soils) may lead some to dismiss his observations
wholesale, it is indeed the case that a relation between 1st millennium AD anthropogenic dark
earths and Barrancoid modeled-incised / Amazonian polychrome tradition ceramic styles
appears to obtain. It is equally relevant, as he points out, that dark earths are for the most part
unreported in the western half of the basin. At the risk of adding a red herring, it is hard not to
highlight that the spatial distribution of anthropogenic dark earths in much of eastern
Amazonia, the Orinoco basin and Guianas overlaps the overall region where bitter manioc is
presently cultivated. One interpretation for this patterning is that bitter varieties of manioc
came into widespread use with the expansion and evident population growth that is recorded
in sites associated with modeled-incised pottery of the Barrancoid tradition, as well as in sites
with neighbouring groups that were in contact with the latter. In this regard, larger sites
characterised by anthropogenic dark earths and ceramic griddles – the latter a reasonable
Chapter 3. The Roots 68
correlate for the processing of manioc for secondary products (Nye 1991) – appear to follow a
trajectory from Hormigoid to Barrancoid assemblages, and from Barrancoid to Amazonian
modeled-incised wares. This might suggest that bitter manioc horticulturists from the
savannah regions north of the basin expanded onto a landscape populated by smaller groups
who employed a wider resource range, inclusive of sweet manioc. If immigrants groups were
able to replicate in rainforest areas the savannah conditions to which bitter manioc cultivation
is well adapted to, i.e. if they were capable of opening and intensively cultivating gardens
(Denevan 1992b, 2004), it is possible that they may have kick-started the definitive onset of
sedentism in regions around the Amazon floodplain.15
5. SUMMARY
This chapter has reviewed lowland palaeo-ecological and archaeological evidence to
provide an account of the roots – in both literal and figurative sense – of Formative lifestyles
in the Amazon basin. In so doing, it has outlined present knowledge about the antiquity of
forms of anthropogenic landscape transformation, established their significance and character,
and weaved their ultimate importance into an account of the emergence of anthropogenic dark
earths during the second half of the Holocene. This seemingly straightforward task has
encountered questions, and hopefully provides passable answers and productive hypotheses,
that sharpen the focus on the Amazonian Formative. It has also summarised aspects of the
broader geographical scope of ceramic traditions and complexes in the middle and lower
Amazon region, in turn providing a general context to examine, in Chapter 4, the
archaeological sequence of the Negro-Solimões confluence area.
15 Ongoing research in the upper Madeira region may confirm Miller’s (1992a; 1992b; 1999) report of mid 1st
millennium BC anthropogenic dark earths with polychrome Jatuarana pottery. If it does, it will be crucial to understand whether Jatuarana and cognate complexes can be shown to be ancestral to, or at least to significantly influence, complexes such as Açutuba (Lima et al. 2006) and Pocó (Hilbert and Hilbert 1980). If that is the case, then the Madeira axis might well become extremely important to understand the expansion of manioc horticulturists (see also Neves 2008).
.
69
Chapter 4
THE CENTRAL AMAZON REGION
1. INTRODUCTION
Archaeological investigations over the last four decades provide a rich context for the
understanding of pre-Columbian history in the Central Amazon region. The backbone for
these understandings was laid out by Hilbert’s (1968; see also Evans and Meggers 1968)
extensive survey and test excavations along the middle reaches of the Solimões-Amazon and
the Japurá rivers, and Simões’ (e.g. 1974; Simões and Kalmann 1987) surveys of adjacent
regions. However, knowledge of the area has been greatly augmented by over a decade of
research in the confluence area of the Negro and Solimões rivers (Figure 16) by the Central
Amazon Project (Heckenberger et al. 1999; Petersen et al. 2001; Petersen et al. 2004; Neves
2001, 2003; Neves 2005; Neves and Petersen 2006; Costa 2002; Lima 2003; Lima et al. 2006;
Donatti 2003; Moraes 2006; Machado 2005; Arroyo-Kalin 2006; Rebellato 2007; Chirinos
2007). This research not only supplements significantly knowledge about ceramic age
occupations in overall region but has also started to show the characteristics of preceramic
lifestyles in the region. This human history is contextualised by a growing database of palaeo-
environmental knowledge of the rivers (Sioli 1984; Irion et al. 1997; Latrubesse and
Franzinelli 2002, 2005), soils (Lucas et al. 1996; Chauvel et al. 1987; Chauvel et al. 1996;
Horbe et al. 2004; do Nascimento et al. 2004), fire history (Piperno and Becker 1996; Santos
et al. 2000) and vegetation (Piperno and Becker 1996; Behling et al. 2001b; Bush et al. 2004a)
that is based on an extensive tradition of research into the region’s physical and biological
characteristics (e.g. Sioli 1984; Irion 1984b,1984a; Radambrasil 1976-8; Rossetti et al. 2004a;
Prance 1990; Sternberg 1998; Vicentini 2001). In what follows, this evidence is summarised
in order to introduce and contextualise the geoarchaeological study presented in Chapter 5.
2. THE LANDSCAPE OF THE CENTRAL AMAZON REGION
The middle reaches of the Amazon river loosely comprise approximately 1500 linear km
of water that starts at the mouth of the Putumayo-Iça river, east of the border between Peru
and Brazil, and reaches downstream to the city of Santarém, in the Brazilian state of Pará
(Hilbert 1968). This is a region in which the Solimões-Amazon receives the discharge from a
number of large rivers, including the Purús, the Japurá-Caquetá, the Negro, the Madeira, and
Chapter 4 The Central Amazon region 70
the Nhamundá-Trombetas. Within this broad area, the terra firme terrain located at the
confluence of the Solimões and Negro rivers is customarily called the central Amazon region
in the archaeological literature (Lathrap 1970b; Heckenberger et al. 1999; Neves 2003). This
interfluvial terrain consists of wide plateaus of the Cretaceous age Alter do Chão Formation
that are characterised by gently rolling hills alternating with tabular interfluves. These show
relatively shallow degrees of dissection by a reticulate network of small rain-fed streams that
wind their way through an undulating terrain. The overall morphology is modulated by neo-
tectonics and shaped by regressive erosion processes associated with the evolution of the soil
mantle, in the latter case shaping a toposequence in which clayey Oxisols in upland positions
grade into Ultisols and sandy Spodosols in mid and toe slope positions (da Costa et al. 1976-8;
Franzinelli and Latrubesse 1993; Lucas et al. 1996; Horbe et al. 2004). A regionally
homogenous, warm, humid tropical climate with month-long dry periods results in a mean
annual precipitation of around 2200 mm and average temperature of around 27° C. Rare
southerly cold fronts (friagens) with temperatures dropping to 17° C are also recorded. The
more pronounced dry season is between July and September with recorded rainfall being less
than 100 mm per month. During the wet season, especially March and April, precipitation is
about 300 mm per month (Salati and Marques 1984; Lovejoy and Bierregaard 1990; Irion et
al. 1997).
The vegetation of the region has been severely altered by urban expansion, industrial
farming and cattle herding over the last century. However, being part of the tropical rainforest
phytocoriae (Prance 1989; Daly and Mitchell 2000), vegetation formations can be
reconstructed on the basis of analogies to areas with similar soil substrate and drainage. In the
Ducke reserve, a 100 km2 region located some 26 km north of the Manaus-Itacoatiara
highway, tall aseasonal rainforest growing on free-draining clayey Oxisols includes
widespread Amazonian species, taxa that are found all the way up to the Guianas but not south
of the Amazon-Solimões river, species at both their extreme eastern and western ranges, and
regionally-endemic taxa. Biodiversity in these forests is tallied at about 2,200 plant species
from approximately 150 families, of which 1,300 are tree taxa, 300 are climbers, 250 are
terrestrial herbs, 170 are epiphytes and 60 are hemiepiphytes. Most plant taxa are adapted to
short-range seed dispersal and many represent poor-soil specialist species. Forest stand
turnover does not exceed 140 years and may be as short as 60 years. Present in the region are
pockets of sandy soils with characteristic Amazonian caatinga–like vegetation and swamps
dominated by palm trees. It is hard to estimate how rich in fauna these forests may have been
in the past although they have been regarded as relatively species-poor in comparison to others
in the Neotropics (Rankin-de-Merona et al. 1990; Prance 1990; Malcolm 1990; Eisenberg
1990; Gentry 1990; Vicentini 2001).
Chapter 4 The Central Amazon region 71
Examined from the riverscape, the Negro-Solimões confluence area has been considered
as a microcosm of the Amazon basin as whole (Neves 2001). The terra firme terrain is
characterised by discontinuous cliffs (falésias) or high bluffs that overlook the two large
waterways of the region. Immediately upstream from its confluence with the Negro, the
Solimões river discharges between 70,000 and 130,000 m3/s and shows a flooding amplitude
of about 10 m that reaches as high as 30 m below the mean elevation of the terra firme during
the flooding season. The river adopts meander, braided and anastomosed river morphologies
within an extensive várzea floodplain formed on tectonically-controlled lineaments and
varying in width between several kilometres and a few hundred meters. The floodplain is
characterised by active alluvial features such as chutes, sand bars, levees, and channel islands,
including here a levee complex 22 km long and up to 4 km wide in the vicinity of Iranduba.
Upstream from this, the left bank of the Solimões is characterised by a large cut-off meander
in which a network of levees, fluvial rias16, and alluvial lakes suggest older alluvial dynamics.
Among the latter, noteworthy is the L. Grande lake, a large oxbow which dries out completely
during the Solimões flooding lows and whose waters are replenished during the Solimões
flooding highs. At this time, the internal alluvial riverscape between L. Grande and a series of
water bodies located upstream, notably the L. Limão lake, forms a labyrinthic riverscape that
teems with aquatic fauna – including here large fish, dolphins, alligators and manatees – and
which can be navigated from one end to the other. The L. Limão lake is a fluvial ria that drains
into the Ariau river, a navigable channel that runs on a geological fault line and which
connects the Solimões to the Negro some 40 km upstream from its confluence (Irion et al.
1997; Latrubesse and Franzinelli 2002; Neves 2003; Donatti 2003).
The lower Negro river, with its characteristic low pH, mostly dissolved sediment load, and
water chemistry strongly imprinted by the decomposition of humic substances, is considered a
low energy drainage that shows a lake-like behaviour, especially during the rainy season,
when the base level rise of the Solimões dams its water flow in the vicinity of Manaus. It
reaches widths of up to 20 km near Manaus and its flooding amplitude is about 14 m, attaining
an elevation of 28 m asl during maximal annual floods. Floodplains are very poorly developed
because the river is confined to its channel but relatively extensive sand bars can form beaches
made of very pure quartz sand that are seasonally exposed during flooding lows. Although its
flooding cycle is a function of high precipitation in its extensive catchment area, it is also
coordinated with the lower Solimões as far upstream as 300 km from their confluence. The
Ariau river, whose direction of flow and water chemistry depend on the timing of the
Solimões or Negro river floods, discharges sediments from the former into the Negro, forming
an elongated delta (Irion et al. 1997; Franzinelli and Igreja 2002; Latrubesse and Franzinelli
2005).
16 Rias are small terra firme streams turned into alluvial lakes as a result of sediment accumulation at their now sunken discharge points. See discussion about their formation in Chapter 3, Section 2.
Chapter 4 The Central Amazon region 72
As highlighted in Chapter 3, preciously little is known about the palaeo-ecological
conditions that have characterised this area throughout the Holocene. At the risk of repetition
it will be remembered that pollen records from the Hill of Six lakes (Bush et al. 2004a; Bush
et al. 2007) suggest that the region was covered by rainforest vegetation throughout the
Holocene. This pollen record, however, is located a few hundreds of kilometres north of
Manaus, in a region that climatically resembles more the northwest Amazon than the Negro-
Solimões confluence. The only other pollen record available is the L. Calado core, located in
close proximity to the town of Manacapuru, on the left bank of the Solimões. The vegetation
that can be reconstructed from this record, however, appears to better identify fluctuations in
the river level associated with sea level transgression and regression than climate fluctuations
per se (Behling et al. 2001b). Despite these limitations, it is clear that the region has been
covered with non-fire-adapted vegetation throughout much of the Holocene: soil charcoal
from forest soils north of Manaus only suggest sustained burning from around the beginning
of the 1st millennium AD (Piperno and Becker 1996; Santos et al. 2000), a timing that most
likely reflects the onset of effective colonisation by sedentary Formative societies (cf.
Meggers 1994).
The evolution of the main rivers of the region is of particular interest. The morphology of
the Solimões’ floodplain is believed to record a late, two-stage, response to variations in the
hydrological conditions provoked by mid Holocene climate change: a first stage, at present
undated but theoretically related to the onset of sea-level regression, is characterised by
significant vertical accretion associated with a channel that would have been less laterally-
active than at present, resulting both in a flat alluvial surface that today rarely sees flooding
and in some of the tributaries of the Solimões grading deltas which form round lakes like the
L. Grande lake and fluvial rias like the L. Limão lake. A second stage, considered an
autogenic adjustment not triggered by climatic influence, is estimated to begin somewhere
between 3000 and 1000 BP. It is marked by more lateral migration of the main channel,
resulting in lateral reworking and smoothing of the older floodplain and a more developed
scroll-dominated morphology (Irion et al. 1997; Latrubesse and Franzinelli 2002). The
Holocene evolution of the Negro is equally interesting. The river is believed to have behaved
as a progradational system until some point in the late Holocene, receiving a more or less
continuous sediment input from the Guyana shields and the Branco river. This sedimentation
infilled its channel in stepwise fashion from the upper to the middle reaches, in turn leading to
the formation of alluvial archipelagos such as Mariuá and Anavillanas during the mid
Holocene. From the mid Holocene onwards, the sediment load is considered to have decreased
consistently, perhaps ceasing almost completely by the beginning of the 2nd millennium AD
(Franzinelli and Igreja 2002; Latrubesse and Franzinelli 2005).
Chapter 4 The Central Amazon region 73
3. THE ARCHAEOLOGICAL SEQUENCE OF THE CENTRAL AMAZON REGION
3.1 Early research in the region
It was pointed out earlier that the backbone for understandings of ceramic age occupations
in the region was laid out by Hilbert’s (1968) research in the 1950s and 60s. These pioneering
investigations established the presence of numerous ceramic age archaeological sites
alongside the main drainages and connected alluvial water bodies, the majority described as
dense, often bi-component ceramic middens embedded in expanses of terras pretas. With a
few exceptions, radiometric dates at these sites show relatively late occupations, most starting
towards the end of the beginning of the 1st millennium AD. Within this broad region Hilbert
described four ceramic phases in the Negro-Solimões confluence area: Manacapuru, Paredão,
Guarita, and Itacoatiara. In order to understand discussions about the ceramic sequence in the
region, it is necessary to briefly outline the main characteristics of these phases.
• Manacapuru phase pottery is described as mostly cauxí17-tempered, sometimes
red-slipped wares in which open vessel shapes with parallel or out-sloping walls,
less commonly inflected vessel shapes, and also low ceramic platters are common.
Many vessel shapes include sub-labial flanges or extended rims, some of which
are ‘cut’ and most of which are used for the application of parallel and diagonal
lines, crosses, comma-like incisions, curvilinear, and rectilinear spirals executed
using fine and wide line incision. Flanges and extended rims are also used to
support nubbins, zoomorphic and anthropomorphic adornos that are sculpted with
modelling. Also recorded are fragments of round-shaped burial urns with short
necks.
• Paredão phase pottery is also described as a mostly cauxí-tempered, sometimes
red-slipped ware that, in contrast to Manacapuru phase materials, emphasises open
and restricted vessels with inflected shapes, relatively small ceramic platters,
bottles, basket-shaped vessels, and characteristic funerary urns. Surface
decorations include fine line incision expressing simple geometric patterns such as
single-oriented and juxtaposed-oriented sets of parallel lines, spirals, and enclosed
rectangles; inside slipping and delicate use of paint that partially replicates finely-
incised motifs; and the use of nubbins and anthropomorphic adornos, particularly
on the shoulders of burial urns.
17 Cauxí is the Brazilian Portuguese name for the silica bodies of aquatic sponge spicules that are commonly
used as temper for pre-Columbian pottery in much but certainly not all of the basin (Linne 1925, 1957; Nordenskiold 1929).
Chapter 4 The Central Amazon region 74
• Guarita phase pottery is characterised as caraipé18-tempered, often thick wares
which include open bowls with sometimes everted or folded rims, restricted
vessels with inflected shapes and mesial flanges, and characteristic burial urns
with anthropomorphic traits in which the modelled ‘head’ functions as vessel lid.
Surface treatment includes red slip; characteristic excision and grooving to outline
rectilinear but rounded spiral, meander, zig-zag, T-shaped, and cross motifs; and
the use of polychrome painting (red and black on a white or red slip) to outline
abstract biomorphic motifs, double lines, punctuations, spirals, meanders, and
circles.
• Itacoatiara phase pottery is described as cauxí-tempered open vessels with straight
walls and slightly overturned or reinforced rims, vessels with low inflected shapes,
globular bowls with constricted necks and everted rims, and small flat platters
with extended flat rims. Surface treatment includes bowls painted white on the
interior and red slipped on the exterior; the use of fine and wide line incision to
form comb-like groups of parallel lines, spirals, and circles; the use of thin line
incisions combined with excision to form circles, half-circles, u-shaped units,
triangles, squares, and commas; and the combined use of modelling and incision
to produce anthropomorphic or zoomorphic massive or hollow appliqués of
different sizes.
Hilbert observed that Manacapuru or Paredão phase middens were overlain by Guarita
phase pottery at two sites, Manacapuru and Paredão (see Figure 17 for the location of sites
mentioned in this section). The Manacapuru site, where the type assemblage for the
Manacapuru phase was described, is located alongside the Solimões, some 80 km upstream
from its confluence with the Negro, in the vicinity of the modern town of Manacapuru. It is
described as a linear expanse of anthropogenic dark earths of ca. 40 ha in extent that shows a
deep (80 cm) and strongly melanised A horizon. Although it constitutes the only Manacapuru
phase site in Hilbert’s survey, he describes a related complex – the Japurá phase – at the
Mangueiras site, near the border between Brazil and Colombia. The Paredão site, where the
type assemblage for the Paredão phase was described, is an expanse of anthropogenic dark
earths of ca. 2 ha in extent that is located some 10 km downstream from the city of Manaus.
Hilbert also recorded Paredão phase burials underlying Guarita phase pottery at Refinaria, a
disturbed dark earth expanse located some 10 km downstream from Manaus. At this site,
however, he observed a third component overlying the Paredão-Guarita sequence, one he
would eventually recognise as part of the the Itacoatiara phase, described at the eponymously-
named site. The latter were described as two adjacent dark earth expanses, of about 15 ha in
18 Caraipé is an organic temper made by burning the bark of the Licania octandra tree (see Hartt 1879:81 for a detailed description).
Chapter 4 The Central Amazon region 75
extent, located some 200 km downstream from Manaus alongside the Amazon river. At this
site, Hilbert observed that pottery of the Itacoatiara phase was underlain by Guarita phase
pottery, which seemed to confirm his interpretation at Refinaria. Surprisingly, Hilbert appears
never to have encountered sites with both Manacapuru and Paredão phase pottery.
Hilbert classified the Manacapuru and Paredão, Guarita, and Itacoatiara phases into,
respectively, the Incised-Rim, Polychrome, Incised-and-Punctuate horizons defined by
Meggers’ and Evans’ (1961) and presented radiometric evidence to support his stratigraphic
sequence: a direct 14C date on the temper of a Manacapuru shard from the eponymous site was
dated to around AD 430-60019. Charcoal associated with Paredão phase pottery at Coarí-2, a
mono-component small dark earth patch located some 200 km upstream from Manacapuru,
was dated to AD 770-940. Charcoal associated with Paredão phase pottery from the
eponymous site was dated to AD 880-1030. Charcoal associated with a rim-incised ceramic
complex from the Mangueiras site, near the border between Brazil and Colombia, was dated to
AD 650-770. Charcoal associated with Guarita phase pottery from the Coari-1 site, a mono-
component small dark earth expanse near Coari-2, was dated to AD 1205-1275. Finally,
Itacoatiara phase remains were not radiometrically dated but inferred to be proto-historic both
on the basis of their stratigraphic position and affiliation to the incised-and-punctuate horizon.
Hilbert marshalled this evidence to suggest that a fully-developed slash-and-burn
agriculture based on manioc and maize, most likely complemented by fishing and hunting,
had characterised communities whose pottery could be classified as part of the incised-rim
horizon, i.e. Manacapuru and Paredão, and that more intensive agricultural practices would
have underwritten the lifestyles of Guarita and Itacoatiara phase potters. These interpretations
in part followed from Steward’s and Meggers and Evans’ ideas about the Amazonian
Formative (incised-rim horizon peoples were tropical forest cultures whilst polychrome
horizon people were at the same level as the circum-Caribbean or sub-Andean cultures) and
echoed interpretations of other ceramic complexes in the overall region (both the Marajoara
and Napo complexes (Meggers and Evans 1957; Evans and Meggers 1968) and the lavish
Santarém pottery (Palmatary 1939; Palmatary 1960) were considered to represent more
complex societies). They also reflected the contrast Hilbert perceived between single burials
of small, seemingly standardised funerary urns within Manacapuru and Paredão settlements
vis-à-vis reports of Guarita phase mound cemeteries that were separated from settlements and
included urns whose decorative distinctions suggested status-related differences. Hilbert’s
research in the area was supplemented in the late 1960s by Simões (1974), who recorded new
sites characterised by deep horizons of anthropogenic dark earths; described new sites with
Paredão, Guarita, and Itacoatiara phase pottery at the Negro-Solimões confluence area;
19 Hereinafter all reference to age ranges reflect calibrated ranges
Chapter 4 The Central Amazon region 76
recorded possible Guarita and Paredão variants along the Apuaú river, upstream from Manaus;
and observed possible evidence of a proto-historic expansion from the upper Essequibo area to
Rio Preto da Eva, a drainage discharging into the Amazon half way between Manaus and the
town of Itacoatiara.
Hilbert’s and Simões’ research was the subject of sharp criticism by Lathrap and Brochado
(Lathrap 1970b; Lathrap 1970a; Brochado and Lathrap 1982). At a general level, they decried
Hilbert’s and Simões’ attempt to slot the region’s ceramic sequence into Meggers and Evans’
four-horizon model, rejecting especially the use of specific tempering material (cauxí,
caraipé) and lack of attention to vessel shapes as the basis for establishing different ceramic
phases. They also complained that evaluation of this research was made impossible by the fact
that pottery from arguably sequential phases was consistently found mixed in most levels of
published stratigraphic cuts. At a more specific level, Lathrap (1970b) pointed out that the
markedly different set of vessel shapes observed in Paredão phase materials rejected a sibling
position with respect to Manacapuru phase pottery within the incised-rim horizon and instead
suggested an intrusion of potters from a different tradition into the region. He also suggested
that the Itacoatiara phase, as defined by Hilbert, most likely represented a mechanical
admixture between, on the one hand, an early Barrancoid-affiliated component characterised
by the use of closely-spaced fine line incision and modelling, and, on the other, remains more
clearly associated with 2nd millennium AD polychrome complexes. Lathrap argued that an AD
80-220 age range obtained by Hilbert at the Paredão site could be considered as a minimal age
for the Barrancoid-affiliated component, which could be legitimately called the Itacoatiara
phase.
Hilbert had argued that Guarita phase pottery was a legitimate complex within the
polychrome horizon but, peculiarly, showed a use of grooving and addition of mesial and sub-
labial flanges that were absent in sibling complexes from upstream and downstream, e.g. Napo
and Marajoara, and present in the Tutishcainyo pottery of the Ucayali basin. Following the
lead of Meggers and Evans (1961), he argued that this contrast could be explained by
suggesting a common Andean origin followed by two distinct population expansions, one
resulting in the Guarita phase and the other resulting in the Napo/Marajoara phases. In
contrast, Lathrap (1970b; 1970a) argued that both an older and younger moment could be
recognised in the Guarita phase material published by Hilbert. The earlier one was recorded at
the Manacapuru and Refinária sites and was characterised by a Manacapuru-like use of sub-
labial flanges, an emphasis on polychrome painting in everted rims, and Barrancoid painted
decoration that suggested in situ evolution from the Manacapuru phase. A later one, recorded
in Guarita phase remains from the Paredão site, showed more clear relations to the 2nd
millennium Napo and Marajoara polychrome complexes. This interpretation, evidently a
Chapter 4 The Central Amazon region 77
corollary of his suggestion that evolutionary linkages should characterise the relation between
complexes of the Central Amazon, led him to also suggest that caraipé-tempered pottery
found with the modelled-incised Itacoatiara shards represented an incipient use of this temper
by Barrancoid potters. Subsequently Brochado and Lathrap (1982) argued that the presence of
flanges, everted rims, and polychrome painting in a Barrancoid complex dating back to the
final millennium BC, coupled with a lack of true mono-component Guarita phase sites in the
region, strongly suggested that a time-deep Amazonian polychrome tradition originated in the
central Amazon region.
3.2 The Central Amazon Project
With Amazonian archaeology strongly divided into the two camps discussed in chapters 2
and 3, it remained possible to uphold contrasting accounts that did not seriously re-examine
some of the premises which supported these interpretations. After these seminal discussions,
Hilbert’s and Simões’ archaeological efforts expanded to other areas of the middle and lower
Amazon basin whilst Lathrap’s and his student’s requests for permits to conduct research in
the area were systematically rejected. Thus little attention was paid to the Negro-Solimões
confluence area until the 1990s, when the Central Amazon Project (PAC) was started. The
explicit aim of this on-going project was to test Lathrap’s hypothesis about the time-deep
antecedents for the Polychrome and Barrancoid traditions in the central Amazon region. This
research initiative has focused its efforts on the identification and excavation of a number of
important sites and also pioneered the use of geo-archaeological methods to study
anthropogenically-modified soils that characterise many of them. The present state of
knowledge of this research (Figure 18) not only enhances greatly our understandings of the
appearance of sedentary lifestyles in this part of the Amazon basin but also constitutes a
context for many specific questions about anthropogenic soils in the region. Given that the
case studies examined in this dissertation consist of several of the most important
archaeological sites investigated under the umbrella of the project, it is both economical and
instructive to summarise existing knowledge about the Negro-Solimões archaeological record
on a site by site basis.20
3.2.1 The Archaic in the central Amazon region
The Dona Stella site (Costa 2002; Lima 2003; Neves 2003) presently constitutes the only
firm evidence for preceramic occupations in the Central Amazon region (Figure 95). The site
20 To be able to present a summary of such wide ranging and important research, much of it only available in
project reports and master’s dissertations, is a privilege for which I can only express gratitude to my colleagues from the Central Amazon Project, especially its leader E. G. Neves. The following section is based on knowledge current up to approximately 2007. I have done my very best to reference project sources where appropriate and claim responsibility for any errors that have slipped into their interpretation, which it must emphasised, is preliminary.
Chapter 4 The Central Amazon region 78
consists of a dense lithic scatter observed in a 1 ha expanse of sandy soils located in the
Negro-Solimões interfluvial region (Figure 19). Six radiocarbon dates on charcoal and soil
organic matter identify death events at 10.8-10.6, 8.5-8.4, 6.4-6.3, 6.2-5.9 and 5.3-5.1 cal kyr
BP (Table 1). A preliminary study of 600 lithic pieces from initial excavations and surface
collections evidences a wide range of artefacts, including ground, polished and flaked pieces
on cobbles, cores, plaques, and flakes. Pecked instruments consist of large manos on
sandstone, a large angular mortar made on a flaked cobble, two rounded pestles, as well as
hammer stones, nut-breakers, anvils, grooved polishers and mortars made from cobbles.
Polished stone tools include two axe fragments. The flaked-stone industry includes cortical,
reduction and bipolar flakes, retouched flakes, blades, a concave-edged knife fragment, and
plano-convex scrapers. In addition, a complete bifacially-retouched triangular projectile point
with contracting stem, serrated convex edges, and a slight invasive basal flake on one side is
reported (Figure 20).
A complex aspect of archaeological interpretations of Dona Stella is the fact that the
assignation of particular remains to specific ages is notoriously difficult: the sandy expanse
where these artefacts are found has been mined as a source of white sands and the resulting
quarry subsequently employed as a dumping ground for farm waste. In addition, as is
discussed in more detail in the geoarchaeological study, the sediment matrix of the site is
podzolised, leading to significant problems of stratigraphic interpretation. Notwithstanding,
pending the results of more detailed analyses by F. Costa, some broad typological
generalisations about the lithic assemblage at the site can be offered. First, the stemmed
morphology and basal fluting of the projectile point found at Dona Stella immediately recall
other finds from the Amazon basin, Colombia, and Venezuela (Ardila 1991; Oliver and
Alexander 2003; Meggers and Miller 2003; Hilbert 2005), including here Restrepo and Las
Casitas points, most likely suggesting an early Holocene age. Second, the basin-wide review
of archaeological literature presented in the previous chapter highlighted that plano-convex
scrapers and bifacially-knapped instruments are observed at the Caverna da Pedra Pintada and
early Holocene occupations in the upper Madeira sequence but not in subsequent occupations
after the 8th millennium BP. This might suggest that at Dona Stella these remains can be
linked to early Holocene occupation events, in turn lending support to earliest age ranges
obtained radiometrically at the site. It was also highlighted that axes and nut breakers are
variously reported at Peña Roja in the northwest Amazon and Gruta do Gavião in the lower
Amazon, lending further support to the suggestion that 9th cal millennium BP ages at Dona
Stella reflect human occupations. Ground stone tools are evident in some of these earlier
contexts but become an important dimension of assemblages in the Amazon basin around the
mid Holocene, with Massangana phase sites in the southwest Amazon and implements
associated with ceramic middens of the Mina tradition. This not only supports the suggestion
Chapter 4 The Central Amazon region 79
that the 7-6th cal millennium BP dates record an occupation at the site but, in addition, hints
that future research in the region may yet identify mid Holocene preceramic occupations. The
latter point is particularly emphasised by the fact the youngest age range recorded at the site is
co-eval with preceramic occupations at the Abeja site in the Colombian Amazon.
The suggestion that all dated events at Dona Stella record human occupation events is
buttressed by the fact that no clear evidence for landscape-level burning has been reported for
this time range in the central Amazon region. Additional but less certain evidence for
preceramic occupations in the region should at least be mentioned. First, excavations at sector
II of the Açutuba site – a large ceramic age dark earth expanse alongside the lower reaches of
the Negro river (Heckenberger et al. 1999, discussed in further detail below) – record 7.8-7.6
cal kyr BP charcoal and soil enrichment in deep sediments that show no clear association with
artefacts (Heckenberger et al. 1999:376ff). Ongoing survey of other sandy patches within the
Negro-Solimões interfluve area also evidences the presence of preceramic occupations (F.
Costa, com. pers., 2005). Finally, a brief inspection of one expanse of anthropogenic dark
earths near Cacau Pireira (Arroyo-Kalin, field notes, 2003) revealed a complete lack of
ceramic remains. Future research should establish whether the latter can be confirmed as a
central Amazon region correlate of the Massangana phase.
3.2.2 The ceramic sequence in the central Amazon region
3.2.2.1 The Açutuba site
In order to understand the ceramic Formative sequence of the central Amazon region a
mandatory starting point is the archaeological record of the Açutuba archaeological site
(Heckenberger et al. 1998, 1999; Petersen et al. 2001; Petersen et al. 2003; Petersen et al.
2004; Lima et al. 2006). The latter is a 3 km long and 400 m wide expanse of sandy
anthropogenic dark earths located on a high, relatively flat linear bluff on the right bank of the
Negro river. The site, which has been investigated by the Central Amazon Project since 1995,
is located approximately 45 km upstream from the confluence of the Negro and Solimões
rivers. Açutuba has been subdivided into three sectors (I, II, and III), each of which is
delimited by flanking streamlets that drain the terra firme and discharge into the Negro river
(Figure 21; see also Figure 84). The terrain towards the riverfront is characterised by a thick,
dark terra preta anthropogenic horizon in which abundant ceramic remains can be observed.
Towards the ‘back’ of sectors I and II, the site is characterised by a gradual shift to sandy
terra mulata-like soils, the latter generally showing a decrease in the density of ceramic
remains (Neves 2003; Lima 2005). Açutuba is an important site for broader discussions about
Amazonian prehistory because its large size, abundant archaeological remains, and position
along a drainage that lacks true cultivable floodplains decisively contradicts the thesis that
Chapter 4 The Central Amazon region 80
sedentary settlements during pre-Columbian times were restricted to the vicinity of whitewater
rivers with várzea floodplains (Heckenberger et al. 1999; Petersen et al. 2001; Neves 2005;
Lima et al. 2006; cf. Meggers 2001a).
Occupations associated with all ceramic phases known in the region are reported at the
site. However, the distribution of these remains is not homogenous: auger surveys,
excavations, and inspection of surface materials identify site ‘cores’ at each of the three
sectors previously mentioned). Among these are groups of mounds circumscribing a plaza-like
area with low concentrations of ceramic remains in sector IIB (Heckenberger et al. 1999;
Petersen et al. 2004); an extensive urn cemetery buried under a meter-thick anthropogenic
horizon in sector IA (Neves 2003); and the presence of ceramic remains not associated with
strongly melanised soils under about a meter of archaeologically-sterile sediments at the back
of the site (Lima 2005; Lima et al. 2006). Also recorded is the presence of an artificial trench
located some 600 m from the river front. The lack of homogeneity in archaeological remains
is also reflected in the physical and chemical characteristics of sediments embedding these
artefacts: separate excavations at sectors I and II and III show soils with high but variable
carbon, phosphorous, calcium, potassium, manganese, zinc and copper concentrations
(Heckenberger et al. 1999:361, Table 2), suggesting differential deposition of settlement
debris associated with overlapping occupations by different ceramist groups. On the other
hand, the horizontal and vertical distribution of archaeological remains at the scale of each
sector shows broad stratigraphic contiguity, implying a long and spatially-diverse process of
pre-Columbian human occupations (see also Lima et al. 2006).
Understandings of the archaeological sequence reconstructed from investigations at the
site have changed over time. Research in the late 1990s (Heckenberger et al. 1998, 1999;
Petersen et al. 2003; Petersen et al. 2004) subdivided pottery remains collected in stratigraphic
excavations (sectors IIB and IA) into two broad ceramic complexes. Complex I was affiliated
to the Barrancoid, Modelled-incised (M-I) or Incised-Rim traditions (after Lathrap 1970b; and
Meggers and Evans 1961; Meggers and Evans 1983) and consisted of ceramic remains that
showed strong similarities to Hilbert’s (1968) Manacapuru phase yet also included an earlier
component in which polychrome red-on-white painting, cut rims, modelled incision, mesial
flanges and zone incised decoration could be observed. These two sub-complexes were
labelled as IB and IA by Petersen et al. (2003; 2004) and observed to occur mainly in the
deeper part of excavated sequences or in areas of the site with low levels of sediment
melanisation and chemical enrichment. Based on radiocarbon dates on charcoal, Complex I
was considered to date to between 750-150 BC (�-97528) and AD 890-1160 (�-97527) (Table
2). Complex II was affiliated to the Amazonian Polychrome tradition. It consisted mainly of
wares that showed strong similarities to Hilbert’s (1968) Guarita phase pottery and also
Chapter 4 The Central Amazon region 81
integrated remains that could be classified into his Paredão phase. Guarita-like remains were
observed to be ubiquitously scattered along the surface of the site whilst both Guarita and
Paredão were found in the upper part of deposits with strongly-melanised, chemically-
enriched sediments. Complex II was considered to date to between AD 990-1160 (�-90009)
and AD 1310-1450 (�-109183) on the basis of charcoal from stratigraphic excavations and
AMS dated shards from surface collections.
Petersen et al. (2003; 2004) discussed an evolutionary continuum between sub-complexes
IA and IB, hypothesised that peoples affiliated to either had coexisted briefly around AD 0
(after which time only IB or Manacapuru-phase groups had existed), and suggested that
occupations had been characterised by egalitarian and non-stratified small-scale villages in
which no site hierarchy existed. In their reconstruction, this state of affairs would have
persisted until the emergence of Complex II towards the end of the first millennium AD. The
latter was considered a distinct tradition which, however, showed clear evolutionary linkages
with prior developments in the study area, especially as far as Guarita-like remains were
concerned. Paredão materials were variously discussed as reflecting a short intrusive phase
(after Lathrap 1970a) or constituting a special purpose mortuary/ceremonial ware (Petersen et
al. 2003; Petersen et al. 2004). The fact that remains from Complex II were found associated
with earth mounds around the putative plaza-like space in sector II of the site was marshalled
as evidence for the presence of a hierarchically-organised polity characterised by a long-
lasting, sedentary occupation that relied on terra firme agriculture. In other words, Complex II
was associated with the definitive onset of sedentary occupations and development of terras
pretas at the site (Heckenberger et al. 1999, 2001).
Continued research by the Central Amazon Project has led to a reformulation of this
scenario. New excavations at sector II of Açutuba have permitted the isolation of an early
ceramic complex characterised by fibre-tempering and zoned incised motifs which might be
associated with Meggers’ and Evans’ (1961; 1983) Zoned Hachured (ZH) tradition (Lima
2005). Radiocarbon dates on charcoal (see Table 2) associated stratigraphically with these
remains (�-90722, 202677) indicate a timing for occupations in the first millennium BC. The
ZH wares are overlain by remains that can be associated with the Açutuba phase, the next in
the ceramic sequence currently employed within the project research area. The Açutuba phase
is an important redefinition of sub-complex IA based on excavations of the single-component
occupation (T9/T10) located at the back of sector IIA at the site, the re-analysis of some of the
sub-complex IA material from the lowermost occupation recorded in Unit II, sector IA (see
Heckenberger et al. 1999), and re-examination of ‘early’ Manacapuru remains (reported by
Machado 2005l; Donatti 2003, see below) at other sites within the project’s research area
(Lima 2005; Tamura 2005; Lima et al. 2006).
Chapter 4 The Central Amazon region 82
Açutuba phase pottery is characterised by cauxí or caraipé tempered wares that emphasise
open, often inflected vessel shapes with labial and mesial flanges. These can be profusely
decorated with curvilinear modelled-incised motifs, biomorphic adornos, white slip,
polychrome painting, grooving, and excision, among others. Lima et al. (2006) argue that the
presence of caraipé temper, labial and mesial flanges, curvilinear incision, polychrome
painting, and characteristic modelled-incised rounded lugs on rims suggests that Açutuba
phase pottery is stylistically related to the slightly younger Japurá phase pottery from the
Caquetá-Japurá border area (Hilbert 1968) and to Pocó phase wares described by Hilbert and
Hilbert (1980) in the lower reaches of the Nhamundá and Trombetas rivers. Açutuba phase
material has been associated with charcoal fragments dated to between 410-170 BC and AD
430-550 (see �-90724, 178908-10 in Table 2) and is generally found embedded in soils
lacking strong indications of melanisation. As will be evident, some of these characteristics
strongly recall Lathrap’s (1970a) inference of a Barrancoid-affiliated component within the
Itacoatiara phase and his suggestion that an early 1st millennium AD age at the Paredão site
dated their appearance in the region (see Section 3.1).
In the ceramic sequence presently employed in the Negro-Solimões confluence area, the
Açutuba phase is followed by remains of the Manacapuru phase, originally defined by Hilbert
(1968) but re-examined by the Central Amazon Project on the basis of more detailed
stratigraphic excavations at the Açutuba site and elsewhere in the project research area. Wares
classified as Manacapuru phase map onto Petersen’s et al.’s (2003) modelled-incised complex
IB, are frequently found associated with strongly melanised anthropogenic soils (see Lima et
al. 2006), and – at the Açutuba site – are associated with charcoal dated between AD 410-550
and AD 690-880 (see �-90723, 106437 and 8 in Table 2). Although wares from the Açutuba
and Manacapuru phases are considered to be evolutionarily related, Lima et al. (2006)
highlight the fact that a number of techno-stylistic aspects of the Açutuba phase are absent in
Manacapuru phase wares and ‘reappear’ with the advent of early second millennium AD
Guarita pottery, contradicting a linear evolution scenario. This account to some extent also
echoes Lathrap’s (1970a) suggestion that an ‘early’ Guarita component at the Manacapuru and
Refinaria sites could be distinguished from a ‘late’ Guarita component at the Paredão site and,
as noted in Chapter 3 (see footnote 9), recalls some of Lathrap’s observations of Tutishcainyo
tradition pottery in the Ucayali basin. More importantly, it buttresses Lima’s et al.’s (2006)
suggestion that the onset of formation of anthropogenic dark earths can be linked to
Manacapuru and Paredão phase potters, indicating a shift in lifestyles as the former succeeds
groups of Açutuba phase potters.
Chapter 4 The Central Amazon region 83
As discussed below, excavations at other sites in the project research area provide clear
pointers for the separation of the Paredão from the Manacapuru phase and, with some
amendments to Hilbert’s original definition, to consider Paredão as a separate and valid
ceramic taxon representing occupations by a distinct population (Neves 2003; Donatti 2003;
Machado 2005; Lima et al. 2006; Moraes 2006). At the Açutuba site, Paredão phase material
includes the large urn cemetery previously mentioned in sector IA and is recorded in strongly
melanised sediments at Unit 2, sector IA, where radiocarbon dates on charcoal date it to
around AD 890-1160 (�-97527, in Table 2). In the ceramic sequence, Paredão phase remains
are followed by the Guarita phase, which is considered to date from AD 990-1160 to AD
1270-1390 at the site (�-90009, �-97529, 30 in Table 2). It will be observed that of the latter
three dates, the earliest (�-90009) clearly overlaps those assigned to the Paredão phase
occupation, a point to which I will return to below. As noted previously, Guarita phase
remains are found on the upper surface of most of the site and co-exist with Paredão phase
material in the majority of exposures that have been excavated.
3.2.2.2 The Osvaldo site
The Osvaldo site identifies an expanse of anthropogenic dark earths of 2-4 ha in extent
that is located on a peninsula-shaped terra firme ridge that overlooks the southern margin of
the L. Limão lake (Figure 25). Intensive investigations by the Central Amazon Project
between 1999 and 2000 delimited the site with the help of auger surveys and conducted
stratigraphic excavations at a number of different exposures (a site plan is presented in Figure
81). The majority of diagnostic ceramic remains so recovered was originally classified as
Manacapuru phase wares (Heckenberger et al. 1999; Petersen et al. 2001; Petersen et al.
2004). However, a recent re-examination of the ceramic assemblage (Lima 2005; Chirinos
2007: Tabela 4.31) has also identified small quantities (<20%) of Paredão phase wares at all
depths in the excavated deposits. The internal organisation and degree of anthropogenic
modification of the soil have been compared to area II of the Açutuba site. Spatial variation in
the density of remains, coupled with different overall depths of the dark anthropogenic
horizon, has been marshalled as evidence for a circular ring village during the height of
occupation (Heckenberger et al. 1999; Neves 2000; Petersen et al. 2001; Neves 2003; Petersen
et al. 2004; Chirinos 2007).
Radiocarbon dates obtained during excavations of the Osvaldo site (Table 3) have
provided a basis to support a number of interpretations about the process of human occupation
of the Lago do Limão area (Neves 2000; Petersen et al. 2001; Neves 2003). Some radiocarbon
dates (* in Table 3) have been marshalled to suggest a post 8th century AD chronology for the
Manacapuru occupation of the site (Lima et al. 2006). Given that Paredão minority wares have
been interpreted as evidence of exchange between resident Manacapuru phase potters and
Chapter 4 The Central Amazon region 84
contemporaneous Paredão phase groups living in the vicinity (Lima 2005; Chirinos 2007), this
interpretation implies that the onset of Paredão occupations in the sub-region took place as
early as the 7th century AD. In addition, some radiocarbon dates from Unit S710 E1966 (^ in
Table 3) have been used to support a scenario in which about 70 cm of the deposit would have
formed within a century or so. This implies the rejection of a number of dates († in Table 3)
because they are out of stratigraphic order or show standard deviations that are too large
(Neves 2003; Neves et al. 2004).
The Osvaldo site occupies a special place in the overall understanding of the process of
human occupation in the central Amazon region. Like the type Manacapuru site excavated by
Hilbert (1968), Osvaldo is characterised by the presence of anthropogenic dark earths.
However, aside from sector II of the Açutuba site, it is the only single-component Manacapuru
age site that has been excavated by the Central Amazon Project. Anthropogenic soils at the
site are thus key to Lima’s et al.’s (2006) suggestion that the onset of lifeways which resulted
in the formation of these soils can be connected to Manacapuru phase potters. Unlike the
Manacapuru site excavated by Hilbert (1968), which has a direct 5-6th century AD date on
pottery, the Osvaldo site shows a series of radiocarbon dates that extend the Manacapuru
occupation past the 8th century AD. Lima et al. (2006) discuss this chronological contrast and
evidently suspect the 5-6th century AD date reported by Hilbert.
3.2.2.3 The Hatahara site
The Hatahara site is a 16 hectare expanse of anthropogenic dark earths located on a high
riparian bluff that overlooks the left margin of the Solimões river, in the vicinity of the town
of Iranduba (Figure 26). The bluff is flanked by relatively abrupt drops on either side, the
result of the dissection of the terra firme by nearby streamlets that drain into the Solimões.
The bank of the latter river, which is within walking distance of the site, forms a narrow (<100
m) alluvial belt that is presently used for cultivation in the low flooding season. Hatahara is
one of the best studied sites in the research area of the Central Amazon Project (a plan of the
site is presented in Figure 62) due to its excellent preservation and high overall visibility, the
latter a consequence of its current status as papaya, banana and lemon tree plantation (Neves
2003; Machado 2005; Rebellato 2007).
A unique aspect of Hatahara is that it has attracted the important attention of pedological
studies of anthropogenic dark earths. Lima et al. (Lima 2001; Lima et al. 2002; Schaefer et al.
2004) describe a toposequence between floodplain and terra firme soils, the latter including
the dark anthropogenic horizon which characterises the site. They established that dark earths
are essentially strongly modified terra firme Oxisols which show higher concentrations of
organic carbon, phosphorus, calcium, manganese, and zinc in the A horizon but otherwise
Chapter 4 The Central Amazon region 85
have developed on the same kaolinitic parent material. Charcoal fragments are described as a
fairly ubiquitous pool of black carbon and microscopic bones are highlighted as the main
source of phosphorus and calcium. Manganese and zinc concentrations are hypothesised to
originate in sediments transported from the Solimões floodplain. Lima et al. attribute the
presence of mica flakes and silica sponge spicules in the soils to the decomposition of pottery
fragments made with non-local clays; characterise the organisation of dark earth A horizon
sediments as a strongly reworked crumb microstructure that contrasts markedly with the relict
granular microstructure of underlying B horizon sediments; and relate a reduction in
phosphorus and calcium, higher extractable aluminium, acidification, and loss of nutrients in
some of the examples they study to the effects of recent cultivation.
From an archaeological perspective, among the most noteworthy archaeological features at
the site is the presence of over a dozen meter-tall earth mounds circumscribing an oval area
(Figure 62) littered with variable but high quantities of ceramic remains (Machado 2005;
Rebellato 2007). Fairly extensive excavations at one of these mounds (Mound 1, Figure 28,
top) reveal over fifteen burials of different types (single and multiple, primary and secondary,
straight and in urns) and provide a basic stratigraphic sequence for the site: the bulk of
recovered ceramic remains is made up of Paredão phase shards embedded in the dark soil
matrix, with small densities of Manacapuru phase pottery in the lower part of the deposit and
even smaller densities of Guarita phase pottery in the upper 20 cm of the site. Excavations at
Mound 2 do not show the presence of human remains but reveal an overall distribution of
ceramic remains similar to that observed in Mound 1: Manacapuru pottery is mostly found in
the lower part of the deposits, Paredão pottery dominates the assemblage, and Guarita phase
pottery is mostly found towards the surface of the mound.
Four human bone specimens from different burials at Mound 1 have been radiocarbon
dated (Table 4): one of them provides a surprisingly old calibrated age range of 850-790 BC
(�-145485), whilst the other three document death events at AD 430-540, AD 610-670 and
AD 880-990 (�-145483, 145483, 145486). In addition, a large number of charcoal fragments
from Mound 1 have been dated: one very old charcoal fragment provides an age range of 750-
150 BC (�-143597, the large span is the result of a 120 year standard deviation), and the rest
evidence death events spanning a more or less uninterrupted occupation from AD 660-770 to
AD 1040-1220. Finally, two younger charcoal fragments from the upper part of the mound
calibrate to AD 1310-1420 and AD 1470-1640 (�-143587 and 143582). A complex aspect of
this evidence is that charcoal fragments that date from the 9th to the 12th centuries AD do not
show good stratigraphic order (Neves et al. 2003; Machado 2005).
Chapter 4 The Central Amazon region 86
Machado (2005) associates Layer II of the Mound 1 (Figure 28, top; Figure 71) with a low
intensity Manacapuru phase occupation in which the kind of soil enrichment represented by
dark earths had not yet begun and suggests that this occupation is dated by charcoal remains
that calibrate between the 4th and 7th centuries AD. She interprets Layer III as Paredão phase
habitation soils dated between the 9th and 12th centuries AD that became strongly melanised as
a by-product of an intense occupation (see also Neves et al. 2004) and were also modified by
settlement activities like the establishment of combustion and pit features, possible digging of
post holes, and the interment of burials. She interprets Layers IV and V as a result of the
deliberate placement of recycled shards and Layer III-type soils from the immediate vicinity
on top of Layer III for the building of a funerary mound. The fact that shards in the mound
overburden (Layers IV and V) show an almost complete lack of conjoins and that some
Guarita phase pottery is found in the upper part of the deposit, leads her to suggest that this
process took place during the time of the Guarita rather than the Paredão phase occupation.
Machado (2005) extends her interpretation of Mound 1 to Mound 2 with some caution,
including here the suggestion that the mound was actually built during Guarita times.
It is important to highlight that this interpretation is based on an additional observation.
One of the burial urns deep in the Mound 1 deposits shows stylistic features that were
recognised as Guarita phase remains when Machado analysed these materials. Since Machado
considered Mound 1 as a funerary structure, the presence of a putatively-Guarita phase urn
was congruent with mound construction during the last centuries before European contact.
However, examined from the perspective of HP Lima’s et al.’s (2006) recognition that similar
stylistic features identify the Açutuba phase (and indeed the critical analysis of Itacoatiara
offered by Lathrap 1970a), it seems plausible that this burial urn reflects occupations
associated with this much earlier modelled-incised complex. Machado (2005) might have
interpreted mound construction differently had she considered that this burial urn, containing
human bones dating between AD 430-540 and AD 610-670 (Table 4), was not part of the
Guarita phase.
The sequence identified through excavations at both mounds is extended and to some
extent clarified by excavations at another portion of the site, considered a flat area without
mounds (Urns’ Unit, Figure 28). The stratigraphic position of diagnostic ceramic artefacts at
this exposure reveals a complex scenario that is still undergoing study21: rare fragments of
Guarita phase pottery are observed in the upper 20 cm of the deposit; very abundant, Paredão-
and Manacapuru-phase pottery shards are recorded in the upper 60 cm of the deposit, the latter
preferentially found below 60 cm or so; nine large, upright-standing in situ Manacapuru
21 This summary is based on first-hand observations conducted at the time of excavations in 2002 and 2006 and
on Rebellato’s (2007) analysis of 381 diagnostic shards out of a total 3000 pieces collected in 2002.
Chapter 4 The Central Amazon region 87
and/or Açutuba22 burial urns are observed between 70 and 110 cm; some urns cut underlying
Açutuba phase (Lima, com. pers., 2006) pottery-lined pits reaching down to approximately
125 cm below the surface; unstructured concentrations of Manacapuru shards reach down
from an uncertain depth to approximately 135 cm; the latter concentrations cut through or are
cut by well-structured pits in which Açutuba phase pottery is observed23; and two deep
cylindrical pit features infilled with loose A horizon sediments and shards of the Paredão
phase are observed starting at some point above 80 cm and reaching down to 160 and 240 cm,
respectively (a photo of finished excavations is shown in Figure 61). This suggests that a set
of closely-spaced Açutuba and/or Manacapuru burial urns were deposited in a non-melanised
soil matrix that is overlain by some Manacapuru, abundant Paredão, and sparse Guarita phase
remains, the latter embedded in the dark anthropogenic horizon that characterises the topsoil
of the site. Deep unstructured concentrations of shards resembling Manacapuru phase wares
(HP Lima, pers. comm., 2006) could represent undetected pits that penetrate into the lower
part of the deposit or indicate a prior moment of occupation by groups whose ceramic
assemblage resembles later-day Manacapuru phase pottery.
More recently, auger surveys have produced a detailed map of variation in the colour and
chemical properties of soils at the site (Grosch 2005; Rebellato 2007). Rebellato (2007)
highlights variation in soil colour, texture, and phosphorus and calcium concentrations by
depth at the site. She observes that strong topsoil melanisation is more characteristic of an oval
area circumscribed by mounds; that surface soils beyond this core appear as brown terra
mulata soils; and that sampling points near or at mounds show high phosphorus and calcium
concentrations. Based on the presence of Manacapuru pottery in the upper 60 cm of the Urns’
Unit and the depth of anthropic enrightment detected through auger surveys, she argues that
the formation of anthropogenic dark earths may have started during the Manacapuru phase
occupation of the site. Based on peak phosphorous concentrations forming a ring-shaped
pattern, she argues that intensive occupations would have resulted in a circular ring village
during the Paredão phase times. Finally, based on linear patterns with medium phosphorus
values towards the upper part of the soil mantle, she suggests that a linear settlement not
unlike those reported in ethnohistorical sources (e.g. Myers 1973) would have existed during
the Guarita phase occupation of the locale.
A final set of insights about the process of human occupation of the region can be drawn
from plant microfossil evidence and bone isotopic signatures. Bozarth (2005) has identified
22 Techno-stylistic features of these vessels appear to record the evolution from Açutuba to Manacapuru phase
pottery (Neves, com. pers. 2007).
23 Rebellato (2007) identifies pottery in Feature 3 (70-120 cm below the surface) as Açutuba phase material. However, Feature 3 is clearly a composite feature in which at least two distinct depositional events are recorded (Arroyo-Kalin, field notes, 2002).
Chapter 4 The Central Amazon region 88
phytoliths of maize cobs, Cucurbita fruit rinds, and Bactris-type phytoliths in a sediment
column from the Hatahara site. Maize phytoliths peak in abundance in samples above 40 cm
and also between 90-120 cm below the surface. Bactris-type phytoliths, in contrast, tend to
increase with decreasing depth. Bozarth interprets these finds as evidence that the source
sediment samples a kitchen garden where refuse was discarded. He also records indications of
arboreal phytoliths and grass phytoliths which he interprets as events of abandonment and
resettlement at the site. The implications of this important evidence are best appreciated when
compared with 13C from bone collagen for the site (Table 5). The latter show a progressive
trend towards more positive values with time, with an isotopic signature that is comparable to
that recorded (Roosevelt 1989b:54, Table 2; Roosevelt 2000:482-485, Table 15.3) in early
human skeletons from the middle Ucayali and Marajó Island (an inferred diet of fish, game,
and manioc) and falls short of values obtained from 2nd millennium AD skeletons from the
upper Ucayali (inferred to indicate the progressive adoption of maize in the diet). Whilst the
isotopic evidence suggests a diet that does not use C4 plants like maize as the main dietary
staple throughout the whole sequence (perhaps purposes such as feasting can be envisioned,
see Raymond 1993), it is striking that slightly higher values are recorded in mid 1st
millennium AD bones. As noted above, these remains come from an urn whose use of
polychrome pottery and overall shape, as Lima et al. (2006) argue, show characteristics that
re-appear in Guarita phase pottery. Isotopic evidence for human bones in the temporal range
of the latter phase (Roosevelt 1989b; Roosevelt 2000) does point more consistently to a diet in
which maize may have been important. This may highlight the changing importance of maize
as a crop among specific populations whose occupation is not continuous in the Negro-
Solimões confluence area.
3.2.2.4 The Lago Grande site
The L. Grande lake is an extensive (40 km2) water body circumscribed by abandoned
levees on its southern and western margins and by the terra firme of the Negro-Solimões
interfluve on its northern and eastern margins. Archaeological surveys between 1999 and 2001
identified no less than five terra preta expanses along the terra firme bank of the lake, many
of which are presently or have been until recently under cultivation. Among these,
investigations by the Central Amazon Project centred on the Lago Grande site (Figure 29), a
~3.1 ha expanse of anthropogenic dark earths with abundant pottery remains on a peninsula-
shaped ridge overlooking the eponymous lake (Donatti 2003). This peninsula is connected to
the rest of the terra firme by a 3 m wide land bridge flanked by abrupt gullies falling to the
northwest and northeast.
The peninsula part of the site is characterised as a horseshoe-shaped complex of earth
mounds which circumscribe a low-lying round area with a low density of archaeological
Chapter 4 The Central Amazon region 89
artefacts (a site plan is presented in Figure 76). Auger transects and excavations through two
mounds and the low-lying area evidence that the thickness of the dark anthropogenic horizon
co-varies with this microtopography and demonstrate that by far the most abundant ceramic
remains observed at the site can be assigned to the Paredão phase. However, also recorded in
excavations are low quantities of Manacapuru phase pottery, generally in the lower part of
deposits, and small quantities of Guarita phase shards, mostly in the upper centimetres of the
soil mantle. Excavations through one mound (Unit 3, N508 E596) also identified a
combustion structure made with large blocks of rubified clay well below the Paredão
occupation, at 100 cm below the surface (Neves 2003; Donatti 2003). Pottery associated with
this feature has been subsequently classified as an Açutuba phase assemblage (Tamura 2005;
Lima et al. 2006).
Archaeological survey of the isthmus connecting the peninsula to the terra firme area
identified an unusual pair of 10x5 m linear promontories located on either side of the
northwest gully, a few meters away from the land bridge itself. Excavations of this feature in
2001 evidenced that a wide, flat and abrupt-walled ditch-like feature had been cut into the
gully. These investigations also showed that the promontories on either side had been
constructed by deliberate piling up of soil with little in-mixed organic matter, pointing to a
source in B horizon sediments underlying the A horizon. Construction of the promontories led
to the burial of a dark brown, relatively shallow, organic horizon with low quantities of
ceramic remains, rubified clay aggregates, and charcoal. This arrangement has been
interpreted as evidence for the excavation of a trench – either from a flat surface at the level of
the settlement or through deepening and widening of the existing gully – to construct the
flanking promontories for defensive purposes (Donatti 2003; Neves 2003; Neves and Petersen
2006). Between these two alternative, stratigraphic contiguity in the buried horizon under the
promontories and the organic horizon in the excavated ditch located between them suggest the
trench was a widening of the natural profile of the gully and that sediments used to build up
the promontories must come from a different source, perhaps the hollow that exists between
the passageway uniting the Lago Grande peninsula and the trench sampled by the excavation
unit. The fact that pit features through the buried horizon under the flanking promontories do
not extend through the overburden of the sediments used to build the promontories suggests
that the construction of the promontories is most likely not contemporaneous with the cutting
of the trench: if they represent the placement of upstanding logs immediately around the gully,
an interpretation that supports a defensive function, enough time passed that logs decomposed
Chapter 4 The Central Amazon region 90
and their negatives were infilled before they were buried by the artificially-constructed
promontories24.
Beyond the isthmus, on the terra firme part of the site, the soil mantle is made up of a dark
brown organic horizon that on the surface appears to resemble a typical A horizon of a clayey
Oxisol under forest vegetation. However, an auger survey across an area approximately 2.5 ha
in extent hinted that this horizon was much thicker than would be expected and also evidenced
low concentrations of pottery throughout. An excavation unit at an auger point with a high
density of pottery revealed only very low quantities of Paredão phase remains yet also
confirmed that the soil mantle was an unusually deep A horizon comparable to brown
anthropogenic soils described in the Colombian Amazon (Andrade 1986; Mora 1991).
A set of 16 radiocarbon dates on charred plant fragments (Table 6), mostly from the
peninsula side of the site, provides a chronological basis for a number of archaeological
interpretations about the process of human occupation of the L. Grande lake. Initial
occupations of the Açutuba phase at the site are recorded in the deeper part of Unit 3, which
have been dated to the 1-2nd centuries AD (�-178920) by a charred seed found within the
combustion structure. Subsequently, a Paredão phase occupation starting around the 8th
century AD (�-143606) is considered to have resulted in the rapid development of over 40 cm
of dark earths below 100 cm in Unit 1 (Mound 1, dates marked with * in Table 6), peaking as
late as the 9-10th centuries AD (�-143603, 4 and 5) in the form of a Paredão ring village with
fairly intense occupations (�-143601, 2 and 7 from Mound 1; �-178919 and 21 from Mound 2)
prior to abandonment (Neves 2003). The ditch-and-promontories complex revealed by
excavations at the isthmus has been interpreted as a defensive feature and discussed as
evidence of political conflict and/or a surge in defensive needs at some point after the 10th
century AD (�-178927) (Neves and Petersen 2006). Small quantities of Manacapuru phase
shards in-mixed with a majority of Paredão phase remains below about 100 cm in Unit 1 have
been interpreted as ‘tradeware’ from unidentified nearby Manacapuru sites, in turn suggesting
the presence of Manacapuru phase potters in the region until Paredão times (Lima et al. 2006;
Neves 2003; Donatti 2003; Chirinos 2007). Finally, Guarita phase pottery, mostly found on
the surface of the site, has been interpreted as evidence of sparse later-day occupations (Neves
2000, 2003; Donatti 2003; Neves et al. 2004; Lima et al. 2006; Neves and Petersen 2006).
24 Recent excavations at the Lago do Limão archaeological site (see below) identified an artificial trench with
profile that is similar to that observed at Lago Grande (Moraes 2006). Moraes has marshalled ethnohistorical and ethnographic evidence to argue that this feature, which is not in a position that could be construed as defensive yet also faces water resources (the Lago do Limão lake), can be interpreted as a turtle corral. Leaving aside for now the question of whether the suggested function is accurate or not, the remarkable similarities in size and shape between both trenches can be construed as indirect support for a widening and deepening of the gully following an equifinal technical recipe and may thus point to pursuit of a similar purpose.
Chapter 4 The Central Amazon region 91
3.2.2.5 The Nova Cidade site
The Nova Cidade site is a large (80 ha) sandy terra preta site located on the terra firme
north of Manaus, some 15 km from the left bank of the Negro river (Figure 32), in the vicinity
of a small affluent streamlet, the Cuieras igarapé. The region is dominated by a combination
of tall tropical forest and caatinga vegetation characteristic of sandy substrates and is adjacent
to southeast corner of the reserve Ducke (see Section 2 of this chapter). This geographical
position underscores the overall importance of the site as evidence of a large settlement that
formed dark, anthropogenically modified soils at a considerable distance from large rivers.
Knowledge of the site, however, is severely limited by the fact that the better part of it was
destroyed by the construction of a housing compound at the outskirts of Manaus in recent
years (Figure 6, right). Reports from salvage operations (Neves and Costa 2001, 2004)
identified a 6 ha portion of the site in which large concentrations of ceramic remains and an
important array of lithic pieces were identified. Among these remains were in excess of 240
burial urns, many of which contained human bone remains, over 250 concentrations of shards,
and flaked, ground, and polished stone tools. The majority of the ceramic assemblage is
associated with the Paredão phase but remains of the Manacapuru and Guarita phase wares are
also recorded.
3.2.2.6 The Lago do Limão and Antônio Galo sites
The Lago do Limão site (Moraes 2006) is an approximately 28 ha expanse of
anthropogenic dark earths located within walking distance of the Colonia Lago do Limão
village, on the margins of the L. Limão lake (Figure 33). Excavations at the site record pottery
of the Manacapuru, Paredão and Guarita phases and also a number of additional noteworthy
features. These include a small circular mound complex in the southern portion of the site
which Moraes interprets as deliberately-built platforms on which residential structures have
decayed; a large number of platforms made with redeposited soils that include abundant
laterite fragments intentionally deposited in semi-circular features that are similar to those
recorded in the upper part of S710 E1966 at Osvaldo; an abrupt-walled ditch feature lined
with closely-spaced posthole negatives that Moraes interprets as a turtle corral25; and an area
of high density of ceramic remains in which Guarita phase pottery in the upper 20 cm is
underlain by Paredão phase shards resting on a floor deliberately made of lateritic concretions.
These remains are clearly embedded in a strongly melanised dark anthropogenic horizon.
Below these, a set of ‘inverted top hat’ pit features reach below the dark anthropogenic
horizon and contain Manacapuru phase pottery.
25 See footnote 24.
Chapter 4 The Central Amazon region 92
The Antônio Galo site is a 28 ha expanse of anthropogenic dark earths located opposite the
Colonia Lago do Limão village, overlooking the L. Limão lake (Figure 33). Pottery of the
Paredão and Guarita phases and a total of 25 mound structures have been detected during
survey and excavations of the site. Moraes (2006) remarks that Guarita phase pottery is only
found in the upper 20 cm of the central portion of the site, whilst Paredão phase pottery occurs
over its entire extent and down to a depth of 60 cm. Based on excavations and observations of
large depressions indicating soil removal, he suggests that mound structures were built by
removing soil from the surrounding areas and adding ceramic shards to the surface layers,
with the evident intent of building platforms for residential structures. He also notes that the
deepest strata in the excavation of the north-east part of the site did not show large
concentrations of shards or a strongly melanised horizon, a fact that he interprets as evidence
that mounds were built in this area during the earlier moments of the Paredão occupation.
Of all the sites mentioned in this summary, the Lago do Limão and Antônio Galo sites are
the only two whose soils are not part of the dataset analysed in the geoarchaeological study
presented in Chapter 5. However, their mention in the context of this chapter is not only
warranted by the important insights about Paredão phase occupations that Moraes’ research
has produced but also made worthy by the fact that a series of 4 AMS radiocarbon dates on
diagnostic shards from these two sites (Table 7) provides a chronological basis to discuss a
number of archaeological interpretations about the process of human occupation in the Negro-
Solimões confluence area.26 Of these dates, attention is first due to the OxA-15502 date from
the Lago do Limão site. This date on a modelled-incised shard classified as Manacapuru phase
provides important evidence that the onset of Manacapuru occupations in the Lago do Limão
area minimally started around the 4-5th centuries AD. The OxA-15502 date is important
because it lends credence to the previously rejected AD 430-560 date (�-143608) from Layer
IIIb of the Osvaldo site and upholds the AD 430-660 (P-409) calibrated range for a
Manacapuru shard at the Manacapuru site (Hilbert 1968). It is also congruent with a AD 410-
550 calibrated age range (�-106438) on charcoal from Unit 1, sector IIb of the Açutuba site
(Heckenberger et al. 1999; Lima et al. 2006) and with an age range of AD 430-540 (�-
145484) on human bone from the urn burial at Mound 1, Hatahara site (Neves 2000; Machado
2005). The provenience of the dated shard, an ‘inverted top hat’ pit (Figure 35) identical to
those observed in excavations of Mound 1 at the Hatahara site, strongly supports the
suggestion that the onset of Manacapuru occupations towards the mid 1st millennium AD is a
part of a broader regional process and, as will be discussed in Section 3.2.3, raises questions
about the exact chronology of the Açutuba phase. Another significant aspect of this evidence
is that the provenience unit of this shard would have been cut from soils that are not strongly
26 The support of the UK Natural Environment Research Council (NERC), Tom Higham (Oxford Radiocarbon
Accelerator Unit), and Preston Miracle (University of Cambridge) to obtain these dates is gratefully acknowledged.
Chapter 4 The Central Amazon region 93
melanised but instead underlie the thick and dark anthropogenic dark earth deposit that
characterised the Paredão and Guarita phase occupation at the site (Arroyo-Kalin, field notes,
2005; Moraes, pers. com. 2007).
The OxA-15505 date provides an age range of AD 770-870 for the Paredão phase
occupation at the Antônio Galo site. This age range is highly significant when the collection of
radiocarbon dates from the nearby Osvaldo site is examined: despite the fact that the majority
of the accepted dates at the latter site (Table 3) point to death events in the 7-8th centuries AD
and even though some of these cannot be statistically distinguished from OxA-15505 when
calibrated, it is evident that only one charcoal fragment from Osvaldo (�-143626) post-dates
the inception of the Paredão occupation at Antônio Galo. Significantly, the unit at Osvaldo
where this date comes from shows a ratio between Manacapuru and Paredão phase rim shards
of 23:18 (Chirinos 2007:102, Gráfico 4.1) that departs from the 8:2 ratio that constitutes the
main trend at other units of the site. This suggests that the AD 890-990 date at Osvaldo may
be associated with a Paredão occupation of the site and questions the implication that the
presence of Paredão pottery represents ‘tradeware’. This in turn cautions against considering
Manacapuru phase pottery at the slightly more distant Lago Grande site as ‘tradeware.’ It is
possible that an as yet unrecognised Manacapuru phase occupation, possibly dating to AD
670-780 (�-143606, Table 6), i.e. the timing of the Manacapuru phase occupation at Osvaldo,
took place at the Lago Grande site.
The OxA-15503 date for a Paredão age shard from the Lago do Limão site indicates that
occupations associated with this ceramic phase extended in the Lago do Limão area until AD
1160-1230. Two interesting implications of this age range are, first, that it documents a
duration for the Paredão phase which spans – going by the calibrated mid points – minimally
just under four centuries and, second, that compared to OxA-15504, AD 1290-1400, from a
Guarita phase burial urn, it suggests both phases abut temporally, with the Guarita occupation
taking place most likely during the 14th century AD. The nature of this overlap remains to be
studied in further detail but it is clear from Moraes’ (2006) work at Antônio Galo that a
relatively small Guarita phase occupation takes place after the locale has been strongly
modified during the preceding Paredão phase occupation. The fact that exemplars of crude
Guarita-type excision can be found on a typically Paredão paste under mounded platforms of
the Lago do Limão site (pers. obs. 2005) suggests that the last moments of the Paredão phase
in this area co-existed with the appearance of Guarita phase stylistic modes, in turn suggesting
that these platforms could be associated with the latter moments of the Paredão phase
occupation at the site.
Chapter 4 The Central Amazon region 94
The OxA-15504 date bears significantly on understandings of the Guarita phase
occupation in the Negro-Solimões confluence area. This age range shows strong agreement
with two of the three shards identified as Guarita phase pottery that have been directly dated at
the Açutuba site (�-97529 and �-97530, Table 2); with charcoal dated to about this time range
in excavations of sector IIB at the Açutuba site (e.g. �-109183, 4, �-109180, 1, �-109178,
Table 2); with some of the younger charcoal fragments from the upper 65 cm of mound 1 at
the Hatahara site (�-143582, �-143587, Table 4); with Hilbert’s (1968) dates from the Coari-2
site; and with a series of ‘Guarita subtradition’ complexes identified by Simões and
collaborators in the middle and lower Negro river, in the Uatumã-Japtapú area near
Itacoatiara, and in the lower reaches of the Madeira river (Simões 1974; Simões and Corrêa
1987; Simões and Kalmann 1987; Simões 1987). At the same time it isolates the oldest of the
directly-dated Guarita shards at Açutuba (�-90009, Table 2) and suggests that 11th century AD
dates from mound 1 of the Lago Grande site (�-178921, �-178919, Table 6), as well as co-eval
charcoal from the other sites of the region, are most likely related to the later moments of the
Paredão phase occupation of the Negro-Solimões confluence area.
3.2.3 The Negro-Solimões confluence area
The preceding pages highlight the constantly evolving character of understandings of the
archaeological sequence in the central Amazon region as a result of research over a period of
60 years. Present knowledge conclusively demonstrates the presence of a most likely long-
lasting preceramic occupation in the region. Like other sequences in the basin reviewed in
Chapter 3, the latter may span from the early millennia of the Holocene to the mid Holocene
and tracks shifts in the technological repertoire of human colonisers through perhaps three
distinct moments: an early emphasis on bifacial reduction; the adoption of a unifacial industry
characteristic of wood working; and the use of ground stone implements for the likely purpose
of processing edible plant stuffs, perhaps with an arboricultural emphasis. Possible indications
of high redundancy of locale reuse and/or incipient forms of sedentism associated with plant
husbandry cannot be dismissed, especially because the locale at present does not appear to be
closeby to any significantly important sources of animal protein. F. Costa’s doctoral research
will no doubt provide a far richer set of interpretations than the fragmentary remarks offered in
this synthesis.
Like other sequences in the region, an important gap in the record is observed from the
latest moments of preceramic occupations and the presence of archaeological remains of
Formative age ceramic complexes. The latter (Figure 36) appear as unquestionable yet unclear
evidence for ceramic groups which can be associated with 1st millennium BC initial
complexes of eastern Amazonia. Very negative 13C isotope ratios in bones dated to this time
range (�-145486, Table 5) strongly suggest a diet focused on the consumption of C3 plants.
Chapter 4 The Central Amazon region 95
These occupations are clearly followed after a temporal gap by the appearance of groups that
employed modelled-incised pottery of the Barrancoid tradition, perhaps as early as the final
centuries of the 1st millennium BC and certainly by the end of the first half of the 1st
millennium AD. Ceramic remains associated with these latter groups, the Açutuba phase, are
generally not found embedded in anthropogenic dark earths (Lima et al. 2006) and suggest
initial moments in the re-colonisation of the region by small communities. A marked contrast
in 13C bone isotopic data at Hatahara (�-145483, Table 5) strongly suggests that these were
horticulturists which, among other, may have used maize to supplement their diet.
It has been suggested above that the three parallel accounts of Lathrap (1970a), Petersen et
al. (2003; 2004) and Lima et al. (2006) show significant similarities as regards the
identification of an early modelled-incised or Barrancoid ceramic complex which incorporated
such distinctive techno-stylistic characteristics as flanges, polychrome painting, and the use of
fibre temper. Whilst the suggestion that this ceramic taxon should be called Açutuba is
indisputably advanced by researchers that have examined thousands of ceramic shards and is
clearly less confusing than Lathrap’s suggestion that it be called Itacoatiara, questions need to
be asked about the chronology of the Açutuba phase as presented by Lima et al. (2006): if the
radiocarbon dates associated with this phase are examined, two clusters can be identified. A
first one is given by the 410-170 BC date (�-178908) from T9 at the Açutuba site and by the
750-150 BC (�-143597) from Hatahara. This cluster is unlikely to represent old-wood
problems during initial clearance of the site and more likely points to the older occupations
discussed previously. These dates need to be disassociated from the Açutuba phase as
currently described, which appears bracketed by a younger cluster of dates that includes a
calibrated age range of AD 120-340 (�-90724) from a buried horizon with Açutuba shards in
Unit 2, Açutuba IA (Heckenberger et al. 1999; Lima 2005), a 40 BC - AD 130 age (�-178920)
on a charred seed from the N508 E596 oven feature at the Lago Grande site, and by the AD
340-550 and AD 410-600 dates (�-17809 and 178910) from Unit T10 at the Açutuba site, the
latter being an essential aspect of the definition of the Açutuba phase.
Evidence for groups that made Manacapuru phase pottery, recorded at the Manacapuru,
Açutuba, Osvaldo, and Lago do Limão sites, suggests different population densities in the
region starting from before the mid 1st millennium AD and extending to as late as the 8th
century AD. Although no evidence of a settlement hierarchy can be surmised, an inhabitation
strategy that focuses on site permanence can be interpreted from the presence of funerary urns
that, in techno-stylistic terms, appear to straddle the gap between Açutuba and Manacapuru
phase occupations. Dated Manacapuru shards from excavations at Lago do Limão that show
overlap or continuity with mid 1st millennium AD Açutuba phase remains highlight the need
to clarify the relationship between these phases. Whether this implies that linear evolutionary
Chapter 4 The Central Amazon region 96
relations exist between Açutuba and Manacapuru (Petersen et al. 2003; Petersen et al. 2004;
cf. Lima et al. 2006), or indicates that ‘Açutuba’ is a special purpose (funerary / ceremonial)
ware that falls into disuse towards the second half of the 1st millennium AD, deserves further
investigation, especially because Hilbert’s (1968) mid 1st millennium AD for the Manacapuru
occupation at the eponymous dark earth expanse seems correct when cross-checked by the
direct AMS date on a Manacapuru phase shard from the Lago do Limão archaeological site.
HP Lima’s doctoral research will no doubt elucidate the challenging cultural history that can
be derived from these data.
Manacapuru phase occupations continue to subsist in the landscape at least until the
appearance of the Paredão phase, which in every respect seems like an intrusion in the region
of groups with different ceramic traditions. Human communities tracked by Paredão phase
pottery appear to be larger; develop circular villages consisting of earth mounds centred on
plaza-like areas; are characterised by settlement practices that significantly enhance the
formation of anthropogenic dark earths; and are present in a much larger part of the region.
Lima’s et al.’s (2006) argument about the co-existence of Manacapuru and Paredão phase
potters rests on the suggestion that minority Manacapuru phase pottery within Paredão
occupations, and minority Paredão phase shards within Manacapuru occupations, represent
tradeware. A comparison between dates for early Paredão phase occupations at the Antônio
Galo site and dates for late Manacapuru phase occupations at the nearby Osvaldo site would
indicate the co-existence in the same riverscape of peoples who employed pottery of
significantly different ceramic traditions. This co-existence remains to be clearly demonstrated
through the analysis of ceramic assemblages. Other possibilities could be entertained. One
could envision a takeover of riparian positions by Paredão phase potters that pushes
Manacapuru groups towards interfluvial positions (after Nimuendajú 1950), perhaps spawning
patron-client relationships similar to those reported in the ethnography of the upper river
Negro region (Goldman 1963; Reid 1979; Ramos et al. 1980). This alternative would require
demonstrating the presence of co-eval Manacapuru phase sites in interfluvial regions that are
co-eval to the more ubiquitous Paredão phase occupations in riparian locations. In my view, a
wholesale replacement of Manacapuru communities by Paredão phase potters also cannot be
rejected on the basis of present evidence. This prompts me to advance a simple suggestion: to
directly date of Manacapuru and Paredão shards found within the same deposit (e.g. Osvaldo,
Lago Grande) in order to ascertain whether they are truly contemporaneous or not.
Available radiocarbon dates show that Paredão phase occupations extend over at least four
centuries in the central Amazon region. During this time large expanses of anthropogenic soils
develop, earthworks including ditches and earth mounds are constructed, and population
density appears to increase significantly. Towards the early 2nd millennium AD, ceramic
Chapter 4 The Central Amazon region 97
remains with Paredão pastes but Guarita decoration patterns, including here temper modes and
the presence of burial urns, suggest intermittent contact with Guarita groups (Moraes 2006).
The latter appear to expand over the area in an unusual way: no large single-component sites
are in evidence. However, Paredão phase occupations do not seem to continue into the time
range most clearly associated with Guarita phase occupations, i.e. towards and beyond the 12-
13th century AD. This may indicate that the onset of the Guarita phase in the region is
characterised by smaller population densities than during the preceding centuries. In this
connection, Lima (2003) shows that a number of Guarita phase archaeological sites are
located in upstream reaches of small igarapés, whilst Donatti (2003), Machado (2005),
Moraes (2006), and Rebellato (2007) highlight that ceramic remains associated with these
groups are generally located on the surface of sites. Like many questions in the research
project, whether the extensive cover of Guarita shards on the surface of the Açutuba site
conforms to this pattern, whether it signals agglutination of people at this locale, and whether
the inferred shift in population density can be associated with suggestive patterns in the
palaeo-botanical and alluvial geomorphology records, remain to be examined by future
research. What cannot be dismissed as a possibility, perhaps recalling Balée’s (1989) remarks
on the Arawete and Asurini societies, is that later Guarita-phase occupations took advantage
of biotic and edaphic landscape legacies that had developed at some of the sites they came to
inhabit (see also Neves and Petersen 2006).
4. SUMMARY
This chapter has reviewed archaeological evidence from the Negro-Solimões confluence
area in order to characterise the sites whose soils will be analysed in Chapter 5. The review
outlines the inferential routes employed in the interpretation of different archaeological sites
that are undergoing investigations by the Central Amazon Project and draws attention to
several dimensions of the area’s archaeological record. Through discussion of recent dates on
shards from the Lago do Limão and Antônio Galo sites (Moraes 2006), the preceding pages
offer a few questions about the chronology of some of the most salient ceramic phases in the
research area. The geoarchaeological study presented in Chapter 5 constitutes an attempt to
tackle these and other questions by focusing on the variability of the anthropically-modified
soil mantle of the Negro-Solimões confluence area.
98
Chapter 5
THE GEOARCHAEOLOGY OF AMAZONIAN DARK EARTHS
‘[A robin‘s nest in a museum display is an] epiphytic pedological feature, whose fate is to be translocated by free fall to the soil surface, where it will eventually be
incorporated into the soil, except that part which decomposes first’ (attributed to Francis Hole, in
Schaetzl and Anderson 2005:358).
1. INTRODUCTION
Soils are complex but patterned assortments of organic and mineral materials that result
from the effects of the interaction between climatic, geomorphological and biotic processes on
the physical and chemical properties of the earth’s surface. They constitute a complex and
open system; a material continuum that drapes the entire planet and whose variability is rooted
in specific landscape evolutionary trajectories (Duchaufour 1982; Johnson 1998; Birkeland
1999; Schaetzl and Anderson 2005; Johnson et al. 2005b). Soils are layered minimally
through a combination between build-up associated with the decomposition of the earth’s
surface (colluviation) and depth-wise differentiation of sediments from the atmosphere to the
regolith (horizonation), as well as by net depositional and erosive processes. Surface horizons
are more influenced by soil fauna than deeper horizons. They are therefore essential and
fragile components of terrestrial ecosystems that shape the array of human activities that
manipulate terrestrial biotic resources. In fact most surfaces that are and have been inhabited
by human communities throughout history – what in archaeology we perceive as open-air sites
– have at least initially been soil surface horizons. Thus soils constitute a complex aspect of
the archaeological record: they ‘encase’ archaeological remains, their properties have no small
bearing on the vegetation that grows on them and, as discussed throughout the dissertation,
they constitute archaeological entities in their own right.
Anthrosols are soils whose formation and characteristics have been enduringly influenced
by the material effects of human action (Limbrey 1975; Eidt 1984; Woods 2003). Among
others they include those whose surface horizon has been modified by topsoil disturbance
and/or irrigation associated with different types of agriculture; those which have formed on
human-transported, -manufactured or -mobilised sediments, including here landforms created
Chapter 5. The geoarchaeology of dark earths 99
or altered by humans; and soils whose surface horizons have become significantly transformed
as a result of human-induced inputs (see also Dudal 2005). Anthrosols are ubiquitous on a
planetary scale (FAO 1998): they vary in spatial extent from compost heaps that concentrate
organic matter in the backyard of households to entire landscapes modified over millennia by
agricultural or industrial activity. Archaeological studies of anthrosols constitute an
increasingly more important line of research in geoarchaeology. These investigations not only
attempt to elucidate formation processes of specific archaeological contexts but also offer a
palaeo-pedological account of land use and landscape change through a consideration of the
information recorded in the soils themselves (Limbrey 1975; Eidt 1984; Macphail 1987;
Courty et al. 1989; Holliday 1989; Kemp et al. 1994; Woods 1995, 2003; French 2003;
Davidson and Simpson 2005).
Anthrosols known as anthropogenic dark earths constitute the main focus of the
geoarchaeological study that I present in the following pages. As discussed in Chapter 2, near
consensus exists that these soils result from the decomposition into the soil of debris
associated with inhabitation practices (whether they be middens, kitchens, house, infields,
etc.) and are thus solid proxies for sedentary occupations. As discussed in Chapter 3, it is
possible to argue that they constitute the tail end of a continuum of practices of soil
modification, a historical ecology which most likely originates with the earliest practices of
plant semi-domestication taking place in the basin. However, as problematised in Chapter 3
and exemplified in Chapter 4, in the specific archaeological sequences that make up the record
of the central Amazon region, their appearance is a late development, one that would seem to
post-date the beginning of the 1st millennium AD. The summary of archaeological findings
presented in Chapter 4, lastly, highlights, first, that in the Negro-Solimões confluence area
these soils can be related to presence of pottery from different ceramic phases and, next, that
important inter- and intra-site contrasts can be ascertained. This increasingly more focused
consideration elicits different research questions of archaeological relevance: What practices
led to the formation of anthropogenic soils? What kind of variability exists when soils from
different sites are compared? What inferences about land-use practices can be drawn from this
variability?
These and similar questions collude to shape a single, more general question: What
archaeological information is recorded in the soils and sediments of archaeological sites of the
Negro-Solimões confluence area? In order to address this question below I present
geoarchaeological data from different soil exposures at the Hatahara, Lago Grande, Osvaldo,
Açutuba and Nova Cidade, and Dona Stella archaeological sites (Figure 37). Of these all but
the last constitute classic examples of anthropogenic dark earths. Aside from temporal
variability, it is worthy of note that these locales sample a range of landscape positions –
interfluvial vis-à-vis riparian locales; places overlooking small streams, lakes, blackwater
Chapter 5. The geoarchaeology of dark earths 100
rivers and whitewater rivers – that cover many of the paradigmatic environmental contexts
articulated in discussions of Amazonian pre-Columbian history (Lathrap 1970b; Carneiro
1970; Meggers 1971; Roosevelt 1989b; Miller 1992a; Miller 1999; Roosevelt 2000; Neves
1998b; Heckenberger 2005). For this reason, while the observations and inferences that will
be presented below are specific to each locale or, at first glance, are only pertinent to advance
understandings of the archaeological record of the study area, I argue that they are also
significant to address long-standing dimensions of scholarly argument about the
archaeological record of the Amazon basin as a whole – a point I revisit in Chapter 6 of the
dissertation.
2. METHODS
2.1 Sampling
The main sampling and analytical unit employed in this study is the soil column, which
approximates conceptually but falls short of the three-dimensional body of soil that pedology
calls a pedon (Soil Survey Staff 1996). In the study, soil columns were sampled from exposed
profiles of archaeological excavations or exposed cuts resulting from other activities.
Sampling intensity was in part dictated by the nature of the analytical techniques and in part
constrained by practical limitations. Two types of samples were collected: 1. Block samples to
make thin sections for micromorphological analyses; and 2. Bulk samples to characterise the
physical and chemical properties of the soil profile. Blocks were collected from exposed
archaeological profiles by sculpting oriented 12x18x10 cm samples with the help of different
tools – pallet knifes, trowels and even machetes. The number and type depended on the
characteristics of the context sampled (see Section 3, below). Bulk samples from columns
were collected as 2 cm wide (h) 10x10 cm (w x l) slabs of sediment bagged every 5 cm; sub-
sampled from 1 litre Constant Volume Samples (CVS) collected in stratigraphic excavations;
or obtained in the field using a Dutch auger (Figure 38). The total dataset for the project
consisted of 83 block samples and 357 bulk samples.
2.2 Micromorphology
Micromorphological analysis is a technique of microscopic observation that is used to
describe and interpret features and fabric of soils and sediments in their original spatial
arrangement. Soil micromorphology had become increasingly more important in
geoarchaeological investigations because it permits answering key questions about site
formation and identifying archaeological evidence that would not otherwise be apparent. The
necessary procedures to convert block samples collected in the field into thin sections for
analysis is a laborious, costly and time consuming process:
Chapter 5. The geoarchaeology of dark earths 101
Block samples were transported to the University of Cambridge with the purpose of
manufacturing thin sections, which I conducted personally under the guidance of Mrs Julie
Boreham. Each block was opened and left to air dry for 3 weeks before being placed in an
oven at around 60°C in order to evaporate all humidity. Blocks were then impregnated using a
mixture of 1200 ml Analar grade Acetone, 800 ml epoxy resin, 10 ml of MEKP catalyzer and
5 ml of purple catalyzer. The samples were left to sit for some time before adding a further
amount of this resin mix and then placed in a vacuum chamber in order to force the release of
trapped air bubbles in the soil. Where necessary, a further top-up of resin was added in order
to ensure that the block was fully immersed in the resin mix. Once immersion was achieved
the samples were placed in an oven at 40 °C overnight in order to activate the MEKP catalyser
and achieve hardening of the resin mix. This procedure in effect transforms the sample into a
hardened resin block without disturbing the soil structure. Hardened blocks were then cut to
obtain thin (<1 cm thick) slabs using a circular power saw with a diamond coated blade. Each
slab was notched on the ‘up’ side to ensure that the orientation of the thin section remained
recorded. For each block one slab was employed for the preparation of thin sections.
For each thin section a specially-made window glass slide was polished down to a set
thickness (varying between 23 and 27 mm) using a Brot grinder equipped with
interchangeable coarse and fine grinding wheels. Each slab from each block was lightly glued
with superglue to a temporal glass mount and subjected to an initial grinding to obtain a
polished surface on which to affix the permanent glass slide. Given that the Brot machine
relies on machine oil for lubrication, it became necessary to clean each slab with acetone and
to dry it with a hair drier. Each clean slab was then coated with a resin mix as previously
described but with a higher quantity of MEKP catalyser and a polished glass slide was placed
on top of it. The slab thus mounted was placed overnight under a press to aid affixing and to
ensure that the resin film between slab and slide was as thin as possible. Once slabs were
mounted in this fashion, each was processed using the coarse wheel of the Brot grinder until a
thickness of approximately 1 mm was reached. At this point the coarse grinding wheel was
replaced by the fine grinding wheel and the slab was then slowly ground down to
approximately 50-80 �m. Each thin section was then removed from the machine, thoroughly
cleaned of machine oil, and hand polished using #400 and #800 sand paper and thin oil until a
uniform thickness of 30 �m was achieved, the latter signalled by the uniformity in the white-
gray first order interference colours of quartz grains as observed under polarised light. Each
resulting thin section was then thoroughly cleaned with acetone yet again before affixing a
permanent glass cover onto the exposed surface. Each thin section was labelled with
provenience information and orientation. In total, sixty thin sections were successfully
manufactured.
Chapter 5. The geoarchaeology of dark earths 102
Thin sections were first scanned using a table top scanner in order to produce a meso-scale
set of images for the whole dataset (Figure 39). Each thin section was then studied at
magnifications between x5 and x400 using a Leica Wild M420 macroscope, a Leitz Laborlux
12 Pol S microscope, and a Nikon Optiphot microscope variously equipped with transmitted
plain (PPL), polarised (XPL), oblique (OIL) and ultraviolet (UVL) light sources. Thin sections
were described qualitatively following the recommendations and adapting the terminology of
Kemp (1985), Bullock et al. (1986), FitzPatrick (1993), and Stoops (2003). Interpretations of
some features are based on the broader literature on soil micromorphological analysis in soil
science and archaeology (Babel 1975; Eswaran and Stoops 1979; Stoops and Buol 1985;
Courty et al. 1989; Valentin and Bresson 1992; Davidson and Carter 1998; French 2003, and
other referenced below). In addition, comparison with the reference collection of the
McBurney Geoarchaeology lab and discussion of observations with McBurney researchers
and other specialists in soil micromorphology were important to achieve identifications of
specific features. Some attempt was made to identify minerals but after consultation with earth
scientists it was concluded that they were generally too weathered to enable comparison with
known published references or comparative thin sections. Of those most easily recognised,
feldspars were found to be present in most samples whilst mica was observed in most thin
sections sampling clayey soils.
Measurements and quantification of specific features in thin section (surface area
represented by porosity, quartz grains, and the fine mineral fraction) relied on the analysis of
high resolution digital images using thresholding techniques available in the NIH ImageJ ver.
1.33q software, at times coupled with manual masking of features using Adobe Photoshop 5.0.
Different light sources were employed to increase visual contrasts where necessary, e.g. OIL
with a low PPL upwards beam permitted resolving microscopic charcoal fragments; UVL
light was useful to detect silica phytoliths; images taken at 0°, 45° and 135° degrees of
rotation under XPL were superimposed to contrast porosity, quartz grains and – by exclusion
– the fine mineral fraction (Figure 40). Size classification of the surface area of quartz grains
and pores using ImageJ provided a sui generis but ultimately useful estimate of sediment
particle size classes (see below) that complemented visual estimates conducted with the aid of
percentage charts.
2.3 Analysis of bulk samples
Bulk samples were air dried and a 50 g aliquot was set aside for analyses. The latter was
ground lightly with a ceramic pestle and mortar; rid of visible archaeological artefacts,
charcoal and plant fragments; and sieved to obtain the <2 mm fraction. This fraction was then
employed to obtain a number of parameters, as follows: the colour of samples was
characterised by comparison of dry samples with a Munsell colour chart; pH and electrical
Chapter 5. The geoarchaeology of dark earths 103
conductivity (EC) were measured using three replicates with a well-calibrated hand-held meter
on a paste made of 1 part soil, 2 parts de-ionised water; bulk density for each sample was
determined by dry (105°C) weight on 10 ml of sediment; low frequency magnetic
susceptibility (MS) was measured using a Bartington MS2/MS2B dual frequency sensor on 10
cc of sample. MS measurements are expressed in tesla SI units (hereinafter SI units), also
known as magnetic flux density.
Total carbon was initially measured using a muffle furnace (Loss-on-Ignition (LOI) after
12 hours of combustion at 550 °C), a convenient and inexpensive technique. However, doubts
about the accuracy of the results surfaced when B horizon samples from soils which had not
seen anthropogenic modification (e.g. HA-9) were found to show higher concentrations of
LOI-derived total carbon than the differential between these measurements and A horizon
samples. Other inconsistencies in the dataset suggested these were not procedural errors but
instead reflected the inadequacy of the technique for measurements of total C in Fe-rich
kaolinitic sediments, most likely due to interferences resulting from dehydration of hydrated
iron oxides (Vogel 1997). An attempt was made to assess this source of error by out-
contracting total (Ct) and organic carbon (Co) measurements from ALS Chemex Inc. Both Ct
and Co were measured in a Leco induction furnace (1350 °C, released CO2 measured by
infrared absorption spectroscopy, Co samples are pre-treated with dilute HCl to remove
inorganic carbon and residual carbonates). Data obtained using these independent techniques
produced very different results. Whilst a decrease in LOI 550C weight loss from 7.76% in the
A horizon to 6.87% in the BE horizon of profile HA-9 implied a differential (inferred Co) of
<1%, a result that resonated with Leco furnace data showing that 50% of total carbon (1.75%)
was organic carbon (a net 0.88% of the solid phase), in profile HA-1, LOI 550C weight loss
ranged from 6.76% (196 cm, B horizon) to 8.69% (16 cm A horizon), a net 1.9% whilst Ct
(Leco 1350C) for the same depth intervals showed a rise from 0.61 to 4.33%, a net 3.72%, a
figure that compares well with the measured Co (Leco 1350C) for the A horizon of 3.76%.27
Unfortunately, due to the costs of out-contracting, Leco furnace data could only be employed
in a handful of selected cases. For this reason LOI data are used in the analyses that follow as
a rough proxy of variation for total carbon and supplemented, where possible, by Ct and Co
measured by Leco induction furnace.
Particle size analysis was initially measured using a Malvern 2000 Laser Particle size
analyser. Sieved samples (<2mm) were pre-treated with either 4.4% sodium pyrophosphate or
4.4% Calgon in a 6-hour hot water bath to destroy all organic matter, centrifuged at 3500 rpm
for 13 minutes, decanted and hydrated by adding deionised water, and homogenised using a
27 Preference for the Leco data also found some support in the results of other studies: a sample from a 43-69
depth interval from the Hatahara site was found to have 2.2% organic carbon by the Cornell group (Liang et al. 2006; Solomon et al. 2007), a value comparable to the 2.55% Co (Leco) obtained in this study at 30-40 cm.
Chapter 5. The geoarchaeology of dark earths 104
whirl-mixer. Despite the apparent simplicity of the procedure, measurements on clayey
samples showed problems even after using alternative deflocculants and attempting
sonication: the Malvern results detected mostly silt or sand-sized particles, contradicting the
essentially bimodal particle size distribution observed in thin sections. Measurements on the
same sample spaced by-10 minutes intervals (Figure 41, left) highlighted low replicability
and, moreover, suggested that very fine clay particles and inclusions of organic or
archaeological origin (see below) were becoming deflocculated and re-flocculated into
pseudo-silt sized particles as they spun in the Malvern’s water bath. This led me to prefer
estimating texture on the basis of measurements conducted on thin sections.
The use of soil chemistry in the original research design was originally limited to Calcium
(Ca) and Phosphorus (P) measurements. For the latter the laboratory protocol of phosphate
fractionation described by Tiessen and Moir (1993), essentially a modified version of the
protocol employed by Eidt (1977; 1984) and Woods (1977) in pioneering studies to assess
land use through P concentrations, was implemented. The procedure involves fractionation of
phosphorus using NaOH, H2SO4, NaHCO3, HCl, followed by addition of Molybdenum blue
to extracts and measurement of absorvence in a spectrophotometer after colour development.
P concentrations are obtained by comparison of these measurements to a set of known
standards prepared for the purpose. It was observed, however, that maintaining a constant pH
in extracts was next to impossible due to the interaction between the original pH of different
samples and the buffering capacity of extractants. This difficulty became crucial when the
relationship between the development of colour and pH of the solution was investigated
(Figure 41, right): if the pH of extracts could not be maintained between 5.3 and 6.0,
something particularly problematic in more acid off-site soil samples, measurements of
absorvence tended to produce widely divergent estimates of the different P fractions.
Given low P concentration in the parent material of the region (Costa and Moraes 1998), it
was decided not to analyse total and extracted P (Kämpf et al. 2003:85), and instead use
Inductively Coupled Argon Plasma Atomic Emission Spectroscopy (ICP/AES) to measure
total P and Ca, as well as a host of additional elements: Silver (Ag), Aluminium (Al), Arsenic
(As), Boron (B), Barium (Ba), beryllium (Be), Bismuth (Bi), Cadmium (Cd), Cobalt (Co),
Chromium (Cr), Copper (Cu), Iron (Fe), Gallium (Ga), Mercury (Hg), Potassium (K),
Lanthanum (La), Magnesium (Mg), Manganese (Mn), Molybdenum (Mo), Sodium (Na),
Nickel (Ni), Lead (Pb), Sulphur (S), Antimony (Sb), Scandium (Sc), Strontium (Sr), Titanium
(Ti), Thallium (Tl), Uranium (U), Vanadium (V), Tungsten (W), Zinc (Zn). For this purpose
samples were initially dried, ground and sieved (<180 �m), and then contracted out to ALS
Chemex for measurements using their method ME-ICP41. The latter employs an aqua regia
digestion and then measures the wave lengths of light emissions at 8000°C inside an
inductively coupled argon plasma (ICP) core. Emissions are then collected by wavelength by a
Chapter 5. The geoarchaeology of dark earths 105
spectrometer and amplified to yield an intensity measurement that can be converted to an
elemental concentration by comparison with calibration standards employed by ALS Chemex.
Of the 34 elements measured, significant differences were observed, both depth-wise and
compared to background soils, in the following elements: Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe,
K, Mg, Mn, Ni, P, Pb, Sr, V, Zn. Visual inspection of the data showed that among the latter,
Al, Ba, Ca, Cu, Fe, K, Mg, Mn, P, Na, Sr and Zn showed important variability and were thus
selected for the study.
2.4 Measurement of 13C/12C carbon isotopes
A subset of nine sediment samples was submitted for 13C/12C isotope analyses to the
Godwin Lab, University of Cambridge. This work was exploratory and most samples all
produced the kind of very negative values that is expected from a rainforest environment.
Patterning observed in 13C/12C isotope measurements from Dona Stella are discussed in
Section 5.1.6 of this chapter. The results provided are hereby gratefully acknowledged.
2.5 Radiocarbon dating of microscopic charcoal
The <2 mm charcoal fraction of three bulk soil samples from a single profile, HA-3, was
extracted for radiocarbon dating. For this purpose 100 g samples of sediment were left to air
dry, ground lightly using mortar and pestle, and then the <2 mm fraction collected after
sieving. Each sample was subdivided into three 30 g aliquots and placed in beakers. Each
beaker was treated first with H2O2 for 9 hours in a hot bath and then centrifuged at 3500 rpm
for 13 min prior to decanting. Next, each beaker was treated 4 times with 100 ml of
Hydrofluoric acid (HF) over a 24 hour period. Next, each sample was treated with 7.0%
Hydrochloric acid (HCl) in beakers to remove silicate residues and fluorosilicates, decanted as
necessary, and washed with more HCl until all HF had been diluted to safety. The resulting
samples were placed in Petri dishes and dried at 105°C until only the dry fraction remained.
The dry fraction was placed in glass vials and submitted to the Waikato Radiocarbon lab for
AMS 14C dating. At the lab, sand or smaller charcoal particles were hand picked and
employed for dating. Because of the dangers involved, the charcoal concentration procedure
was carried out by Dr Steve Boreham of the Physical Geography Laboratory, University of
Cambridge, to whom gratitude and recognition for devising the technique are hereby
expressed.
3. CASE STUDIES
The study presented in this chapter is based on samples taken from a number of different
exposures (Figure 42), all of which were described using a combination of archaeological
stratigraphic criteria and pedological criteria (Schoeneberger et al. 1998). Profiles share a
Chapter 5. The geoarchaeology of dark earths 106
number of common features. First, macroscopically, all sediments encountered are massive
and show either a clayey (Figure 43) or sandy texture (Figure 44) in the A horizon. Second,
leaving aside Dona Stella, most profiles show an A to B horizon sequence with transitional
horizons that range from a depth-wise degrade in melanisation (described as an AB horizon)
to a faunally-induced down-mixing of A horizon material into a B horizon. The latter is often
described as a B/A horizon given the fact that volumes of sediment from both horizons are
visible. In the latter case, <2 cm wide krotovinas are often observed (Figure 45). Third,
exposed cuts through all settlement-related profiles include charcoal fragments in A, AB and
often Bt horizon sediments, as well as pottery fragments in A and AB horizons. Fourth, all
topsoil horizons show rootlets. Fifth, unless marked by a pottery line or otherwise indicated,
the transition between the great majority of soil horizons and subhorizons is diffuse and
gradual. Sixth, as is discussed in further detail below, in some cases it can be ascertained that
the current A horizon has formed on sediments that bury settlement-related terras pretas (e.g.
NC-1), in other cases, buried horizons are readily apparent (e.g. LG-2, AC-3) and in yet
others, buried horizons are not apparent to the naked eye.
A brief description of each exposure follows. Additional information about each
archaeological site has been presented in Chapter 4:
HA-1: samples Mound 1 of the Hatahara site. Eight micromorphological samples were
employed to characterise this exposure. Three samples (HA-1.2, 4 and 6) were taken
side by side with the soil column employed for physical and chemical analyses, in the
west-facing profile of Unit N1154 W 1360; another two (HA-1.1, 3) come from the
east-facing profile of Unit N1159 W1360; another two (HA-1.5 and 7) come from the
east-facing profile of Unit N1160 W1360; a last sample (HA-1.8) comes from the
west face of Unit N1157 W1359,5. It should be recalled that the Hatahara site is
presently used as an orchard for papaya, lemon and banana trees.
HA-3: samples Mound 2, which is located in the far east of the Hatahara site, some 200 m
from Mound 1. Another eight micromorphological samples and an adjacent sediment
column, both collected from the east facing wall of Unit N1308-W1204, were used to
study this profile.
HA-5: samples the east wall of Hatahara Unit N1216 W1415, an excavation unit through the
portion of the site which in Chapter 4 was described as an urn ‘cemetery’. Three thin
sections, two from the A2 horizon and one from the AB horizon, as well as a sediment
column that reaches down to a depth of 136 cm, were used to characterise the profile.
Chapter 5. The geoarchaeology of dark earths 107
HA-9: samples a ‘background’ soil profile at the edge of the Hatahara site. From a
pedological point of view this constitutes an Oxisol (Soil Survey Staff 1998) or
Yellow Latosol in the Brazilian soil nomenclature. The profile is located at the point
where the terra firme terrain falls towards one of the deep ravines that flank the site.
HA-9 is sampled by 5 thin sections and a sediment column.
LG-1: samples the north wall of the 16 x 1.5 x 1.5 m archaeological trench parallel to the land
bridge connecting the Lago Grande peninsula, that is, the soil profile beyond the terra
firme-side promontory and away from the ditch. LG-1 is considered a terra mulata on
the basis of comparisons with profile LG-4. It should be pointed out that at the time of
sampling the Lago Grande site was covered by young successional vegetation
(capoeira) associated with sub-recent slash and burn agriculture.
LG-2: samples the east wall of the 16 x 1.5 x 1.5 m archaeological trench that cuts through the
ditch-and-promontory complex, intercepting the peninsula-side promontory. A
complete vertical exposure includes near surface sediments, sediments that makes up
the promontory (Layer IA), the buried organic horizon (Layer II) , the contact of the
latter with underlying Layer I sediments, and Layer I sediments some 50 cm below the
organic horizon.
LG-3: samples the east profile of Unit 1 (N500 E500), a test pit through Mound 1 of the Lago
Grande site. Although excavations had been concluded and backfilled at the time of
sampling for the geoarchaeological project, it was possible to obtain two undisturbed
blocks from the upper 45 cm of the unit because the excavation backfill had deflated
to about half a meter (the profile so exposed was cut back by about 30 cm in order to
reduce disturbance). These block samples, subsequently made into thin sections for
micromorphological study, complement the analysis of physical and chemical data
from the set of Constant Volume Samples collected on a 10 cm basis during the 2001
excavations of the mound.
LG-4: samples the west profile of Unit N772 E415, the test pit on the terra firme terrain used
to ascertain the thick terra mulata-like A horizon described at the Lago Grande site.
Two thin sections and a sediment column reaching down to 56 cm from the surface,
with a further bulk sample from 90-100 cm, were employed to study LG-4.
LG-5: is a background soil column. It consists of three samples collected with a Dutch auger
some 3 km north of the site, in an area lacking archaeological remains. The vegetation
Chapter 5. The geoarchaeology of dark earths 108
of the sampling location is an ecotone between cleared grazing land and tall rainforest
that has not been cleared during sub-recent times.
OS-1: samples the soils from Unit S710 E1966 at Osvaldo. Access restrictions imposed by
land owners at the time of sampling for this study prevented the collection of material
for a detailed pedo-stratigraphic characterisation. The analysis presented below
therefore relies primarily on physical and chemical data obtained from Constant
Volume Samples collected during the 1999 excavations. From excavation records it
appears that the site was being used for cultivation at the time of sampling.
AC-1: samples a ~1.5 m deep profile excavated by pedologists in the I-A area of the Açutuba
site, some 250 m away from the Unit 2 test pit reported by Heckenberger et al (1999),
120 m away from the exposed Paredão urn cemetery reported by Neves (2003), and
40 m away from the edge of the bluff that overlooks the Negro river. The surface
horizon of the area can be considered a classic sandy terra preta marked by a high
density of ceramic shards and charcoal. Based on field observation and topographic
maps, it can be stated that the actual sampling location has not been modified by
wholesale interventions of the soil, such as roads, ditches, mounds or other types of
sediment displacement. However, the area has apparently been mechanically-
ploughed in the past and, like Hatahara, was planted with papaya trees at the time of
sampling.
AC-2: samples a soil profile located some 250 m from the edge of the Açutuba I-A bluff, at a
locale with grey-brown soils covered by successional vegetation that suggests recent
clearance and/or slash and burn agriculture. The main purpose of studying the AC-2
profile was to gain insights into modal pedogenetic conditions operating in the sandy
soils that are characteristic at the site. The sampling locale was thus chosen as a
compromise between the occurrence of sub-recent agricultural activities and the fact
that soils located farther from the riverfront appeared increasingly more clayey in
texture. Four thin sections and a sediment column are employed in the analysis.
AC-3: samples the north-facing profile of T10, a 1x1 m unit excavated in 2003 that is located
in the southern portion of sector II of the Açutuba site. A defining characteristic of the
area is that no visible indications of dark anthropogenic soils are recorded. Instead, the
sandy soil mantle appears as grey coloured terras mulatas. Unit T10 is adjacent to
Unit T9, which was excavated in 1999. During the T9-T10 excavations, a large
concentration of ceramic remains, charred lithic pieces, and laterite fragments were
identified between 40 to 70 cm. These remains are the holotype assemblage for the
Açutuba phase.
Chapter 5. The geoarchaeology of dark earths 109
NC-1: samples a single intact surviving soil monolith at the Nova Cidade site using 8 thin
sections. Bulk samples taken from soil horizons identified macroscopically were
employed for physical and chemical analyses.
DS-1: samples an exposed vertical profile originally produced by mining activities but cleaned
using shovels and trowels in 2002 and recut in 2003 for the purpose of obtaining
undisturbed samples for soil micromorphological analysis.
4. UNDERSTANDING VARIABILITY: THE MAKE-UP OF ANTHROPOGENIC
DARK EARTHS
Samples from the pottery-rich A horizon of anthropogenic dark earths at the Hatahara,
Lago Grande, Osvaldo, Açutuba and Nova Cidade sites are characterised by higher pH values,
much higher concentrations of Ct, Co, P, Ca, Mn, Ba, Cu, K, Mg, Na, Sr and Zn, and, in most
cases, higher levels of magnetic susceptibility (MS) compared to background soils developed
on the same landforms (a sample is presented in Table 8). The magnitude of these
enrichments/enhancements is so overwhelming that it is straightforward to affirm that these
soils have been dramatically modified by past human activities. However, considerable
variability can be observed among samples from different sites, samples from the same site,
and samples from different depths in the same exposure. In order to understand this variability
and relate it to archaeological remains, it is necessary to discuss more closely different aspects
of these soils.
4.1.1 Horizonation
Figures 42-44 show that unmistakable contrasts can be observed among different studied
profiles in the patterns of depth-wise differentiation of sediments that define soil horizonation.
Whilst these contrasts can appear overemphasised by the fact that some of the profiles sample
the sediments that make up the earth mounds described in Chapter 4 (e.g. HA-1, HA-3, LG-3,
in Figure 42) it is evident that all profiles through pottery-rich anthropogenic dark earths
(hereinafter terras pretas) show a much deeper A horizon than those cut through
anthropogenic dark earths located beyond areas in which dense pottery concentrations are
observed (hereinafter terras mulatas). Both, in turn, are deeper than the A horizon of profiles
that cut through soils that do not appear to have been modified by past pre-Columbian
activities (hereinafter the background soils). While more precise interpretations of these
contrasts will be proposed in Section 5, for now a broad overview of the differences that
characterise these horizons is a useful entry point to understand the variability of composition
of these soils.
Chapter 5. The geoarchaeology of dark earths 110
From a macroscopic point of view, B horizon sediments of terras pretas, terras mulatas
and background soils are generally very similar: in all cases they are organically-depleted,
massive, clayey yellow sediments. In thin section (Figure 46), they appear mostly as poorly-
separated, matrix-supported, slightly vughy, massive continuous clayey zones (irregularly-
shaped clayey microscopic peds) that embed a variable density of sand-sized quartz grains. In
some cases, relict evidence of a composite granular microstructure, generally formed by
rounded to subangular, often coalescing faecal pellets (<150 µm), can be observed. The clayey
material shows a light brownish to yellow colour (PPL/OIL) that can be recognised as
characteristic of organically-depleted Fe-rich sediments; a speckled to striated b-fabric (XPL),
which suggests lack of recent faunal reworking; and low interference colours (XPL) that are
consistent with a kaolinitic composition (Costa and Moraes 1998; see also Lima et al. 2002).
From a macroscopic point of view, A horizon sediments of background soils are generally
brown to light grey; A horizon sediments of terras mulatas range from dark brown to light
grey, and A horizon sediments of terras pretas vary in colour from dark brown to ink black.
From a microscopic perspective A horizon sediments range from clayey matrix-supported to
sandy grain-supported sediments (see Section 4.1.2, below) in which extensively
faunally-reworked clayey material shows different optical properties and different microscopic
inclusions. As regards the former, the fine mineral fraction of both background soil profiles
and terras mulatas show brown hues under PPL/OIL and an undifferentiated to marginally-
speckled b-fabric under XPL that suggests a not-insignificant degree of organic matter
retention (Figure 47 and Figure 48). In contrast, the fine mineral fraction of the A horizon of
terras pretas shows generally darker brown hues under PPL, a generally undifferentiated b-
fabric under XPL, and very dark grey colours under OIL (Figure 49). As discussed in further
detail in Section 4.1.3.3, the darker macroscopic colours in terras mulatas and terras pretas
are enhanced by the ubiquitous presence of generally silt to fine sand-sized microscopic
charcoal fragments reworked into the fine mineral fraction by soil fauna (see also Topoliantz
and Ponge 2005) and possibly some impregnation with manganese sesquioxides.
The boundary between the A and B horizon in these three broad categories deserves to be
briefly commented upon. In background soils profiles, the shallow organic-rich A horizon
records a gradual shift towards the B horizon that appears microscopically as an increasingly
less organically-stained, brownish yellow clay (PPL/OIL) with a marginally speckled b-fabric
(XPL). These features suggest a gradual decrease in the reach of soil chelates and a
progressively less deep reach of faunal down-mixing. In contrast, sediments that can be
described as the AB horizon of terras pretas and, to a lesser extent, also those that appear as
the AB horizon of terras mulatas, are characterised by the presence of very large (1-2 cm
wide) infilled root casts and/or animal burrows (krotovinas, see Figure 39, middle) that are
Chapter 5. The geoarchaeology of dark earths 111
generally not observed in the AB horizon of background soils. The latter features have
‘negatives’: just as there are volumes of A horizon sediments faunally down-mixed into B
horizon sediments, often defining an A/B horizon, there are also volumes of organically-
depleted B horizon sediments that are in-mixed into the upper part of the AB horizon (Figure
45). In thin section, AB horizon sediments of terra pretas appear as mixes between
microscopic clayey peds whose optical characteristics are analogous to those observed in
overlying sediments, peds whose optical properties resemble A horizon sediments of
background soils, and peds whose optical properties resemble the optical properties of B
horizon sediments. Soil material that defines krotovinas has often been reworked further by
soil microfauna.
The contrasts between soil horizons is readily indicated in the measurements of pH, Ct,
Co, P, Ca, Mn, Ba, Cu, K, Mg, Na, Sr, Zn, and MS (Table 8). It is noteworthy that B horizon
sediments of terras pretas show levels of enrichment/enhancement that are an order of
magnitude higher than background soil measurements, highlighting the importance of some
down-mixing from enriched A horizon sediments.
4.1.2 Texture and soil mantle evolution
Chemical and physical parameters of samples from sites at which the soil mantle is
texturally clayey show much higher levels of enrichment than samples from locales at which
soils are texturally sandy. To understand the importance of these contrasts a number of
additional micromorphological observations about the organisation of these sediments need to
be summarised:
As shown in Figure 49, A horizon sediments of texturally-clayey terras pretas (Hatahara
and Lago Grande) are constituted by a high quantity of clayey material within which silt-and
sand-sized particles – quartz grains, particulates of organic or archaeological origin (see
Section 4.1.3) and very small quantities of other weathered minerals – are found embedded in
a matrix-supported or porphyric coarse-to-fine related distribution. Clayey material is
kaolinitic and is generally organised as a composite arrangement of irregularly-shaped
microscopic peds. The morphology of the majority of these peds suggests that they have
formed as a result of the coalescence of smaller aggregates whose size ranges (50-200 µm;
500-1500 µm; 2-7 mm) and shape (rounded to oval) can be related to the reworking of the soil
by ants, termites and earthworms (Eschenbrenner 1986; Barois et al. 1993; FitzPatrick 1993;
Barros et al. 2001; Barros et al. 2003; Topoliantz and Ponge 2005). A minority of them is
organised as irregular, slightly vughy, massive continuous clayey zones that lack clear
indications of faunal reworking.
Chapter 5. The geoarchaeology of dark earths 112
In contrast, thin sections sampling the A horizon of sandy terras pretas (Açutuba and
Nova Cidade) show a grain-supported (enaulic) microstructure that is primarily composed of
silt to sand-sized quartz grains and only secondarily of a much smaller proportion of clayey
material (Figure 50, top). The latter is organised as thin, grano-oriented braces (<50µm in
width), small porphyric peds (generally <150 µm in diameter), and rare intergrain rounded
pellets (generally smaller than <60 µm). Compared to clayey terras pretas, particulates of
organic or archaeological origin are generally very rare. However, B horizon sediments of
sandy terras pretas are more clayey than their topsoils (Figure 50, bottom). At Açutuba, the
organisation of B horizon is analogous to that observed at Hatahara and Lago Grande: these
are matrix-supported sediments composed of poorly-separated, slightly vughy, massive
continuous clayey zones which embed especially sand-sized quartz grains. The trend towards
more clayey B horizons at Açutuba and Nova Cidade is also evidenced by high concentrations
of Al deeper in the profile (the chemical formula for kaolinite is Al2Si2O5(OH)4), see also
Costa and Moraes 1998).
A thin section from the A horizon at Açutuba provides essential clues about this apparent
contradiction: it shows the presence of a 2 cm long matrix-supported clayey ped in which i)
the size class distribution of quartz grains mimics that observed in the surrounding grain-
supported matrix, ii) illuvial clay coatings can be observed, an altogether unusual feature in
sandy soils (Figure 50, middle), and iii) there is a higher density of particulates of organic and
archaeological origin than the rest of the thin section (see below). A plausible interpretation
for this ped is that it constitutes relict evidence for the past presence of a more clayey fabric,
i.e. that the soil mantle at the site has suffered some degree of deferralitization (Lucas et al.
1984; Chauvel et al. 1987; Righi et al. 1990; Dubroeucq and Volkoff 1998; Horbe et al. 2003;
do Nascimento et al. 2004). In other words, soils at Açutuba may have undergone processes of
regressive erosion in geologically-recent times, leading to localised depletion of the clay
fraction and attendant shifts from a matrix- to a grain-supported microstructure.
These observations highlight that the texture of settlement-related anthropogenic dark
earths is an outcome of different factors and have important consequences for assessing the
chemical variability of these soils. Focusing first on sources of textural variability, the actual
volume of quartz grains observed in different thin sections appears to be inherited from the
parent material, suggesting it is variable across the region. The angularity and fracture patterns
of quartz grains, the presence of clayey streaks in the cracks of quartz grains, and the broadly
similar appearance of quartz grains in samples from different sites suggest that the particle
size distribution of quartz grains is governed by the break-up of larger grains into smaller ones
as a result of weathering of silica (Eswaran and Stoops 1979; Schnutgen and Spath 1983).
Thus, texture estimates for both Açutuba and Nova Cidade (in Table 9) – the former near the
Negro river, the latter located in the terra firme far from any seasonally-exposed sand banks –
Chapter 5. The geoarchaeology of dark earths 113
cannot be used in piece meal fashion to suggest that texturally-sandy terras pretas are an
outcome of alluvial or wind-blown inputs (e.g. Heckenberger et al. 1999). On the other hand,
it is noteworthy that he abundance and size of rounded clayey aggregates and faecal pellets
that slake to ‘pseudo-sands’ or ‘pseudo-silts’ (see also Jungerius et al. 1999; Schaefer 2001),
coupled with the presence of silt to sand sized archaeological or organic particulates
(discussed below) contribute to making clayey dark earths more ‘silty ‘ or ‘sandy’.
Focusing next on their impact on the chemical variability of these soils, the fact that sandy
soils show a much lower total volume of particulates of archaeological origin highlights that
depletion of the clay fraction results in less efficient preservation of microscopic remains,
most likely because a larger part of the surface of these inclusions comes into contact with
aerobic conditions. It has been stated previously that C, P, Ca, Mn, Ba, Cu, K, Mg, Na, Sr and
Zn are much lower in sandy soils (Table 9). Given that some of the likely forms these
elements will concentrate theoretically implies sorption onto clay lattices, the fact that the
volume of clayey material in texturally-sandy soils is much lower than in texturally-clayey
soils explains why chemical data from bulk samples are skewed systematically and in inverse
proportion to the total volume of quartz that constitutes each bulk sample. Both factors inhibit
inter-site comparisons and caution against interpreting lower chemical enrichment at Açutuba
and Nova Cidade as indicative of less ‘intensive’ occupations.
4.1.3 Anthropogenic inputs
As discussed in Chapter 2, scholarly consensus exists that the heightened chemical and
physical properties of anthropogenic dark earths are the result of inputs associated with a
variety of practices that can be surmised to have taken place at pre-Columbian settlements.
Beyond unpublished micromorphological studies of Belterra terra pretas (Chapter 2),
micromorphological studies of anthropogenic dark earths from the Central Amazon region by
Lima and colleagues (Lima 2001; Lima et al. 2002; Schaefer et al. 2004) have shown that
significant quantities of microscopic debris are preserved in soils of the Hatahara site. This
provides a background to examine the variability of these soils through a consideration of the
presence and abundance of microscopic debris preserved within them and of the bearing they
have on the high physical and chemical values recorded in measurements of bulk samples of
these soils.
4.1.3.1 Heat treated clay and their physico-chemical signatures
Soil micromorphological data shows that thin sections from the A horizon of terras pretas
at Hatahara, Lago Grande, and to a lesser extent Açutuba, embed important quantities of
microscopic pottery fragments (Table 9; Figure 51). These subangular to rounded inclusions
are primarily tempered with aquatic sponge spicules, and much less frequently with charcoal
Chapter 5. The geoarchaeology of dark earths 114
fragments, grog, and, silt to fine sand-sized quartz grains (see also Lima et al. 2002; Schaefer
et al. 2004). It can be expected that microscopic pottery fragments will contribute to higher
concentrations of particular elements on account of different clay sources, tempering material,
and residues associated with their past use. In this regard, Lima et al. (2002; Schaefer et al.
2004) report that shard fragments observed in thin sections from the Hatahara site are made of
illite, which implies inputs of K, Al, Ca, Mg, Fe and Si into the soil. Other studies, in this case
of the actual chemical composition of pottery shards from the lower Amazon basin, identify
additional chemical inputs, notably Mn, Zn, Si, Al, Fe and P (Costa et al. 2004a).
Archaeological evidence from the Negro-Solimões confluence area (Hilbert 1968; Machado
2005; Donatti 2003; Moraes 2006; Lima et al. 2006) highlights that shards which can be
classified into different ceramic phases include distinct but overlapping tempers, whilst trace
element research on shards from the Hatahara and Açutuba sites (Neves 2003) underlines the
likelihood that a combination of different clay sources, each with potentially different
chemical signatures, was used in the past.
Thin sections examined in the present study highlight that a surprisingly low quantity of
microscopic pottery fragments tempered with organic fibres is found embedded in soils from
the Hatahara, Lago Grande and Açutuba sites. Since microscopic shards tempered with
caraipé are an expected input in soils associated with occupations of all ceramic phases in the
Negro-Solimões confluence area, it is possible that small fragments of particular ceramic
types have decomposed more readily than others into these soils. The latter point is
underscored by the different potential sources for high magnetic susceptibility measured in
most samples of the dataset discussed in this chapter. Magnetic susceptibility measures the
abundance of ferromagnetic minerals in soils and the latter most like comes from two distinct
sources. First no reason comes to mind to disregard the possibility that rubified clay
aggregates and pottery fragments are co-responsible for the high MS values measured at
Hatahara, Lago Grande, Osvaldo and Açutuba: heat treatment of Fe-rich clayey material (e.g.
pottery, brick) has been shown to result in high magnetic susceptibility (Jordanova et al.
2001). Second, however, contrasting MS values measured in a transect from soils located far
from archaeological sites, through artefact-devoid ‘background’ soils near sites, to terras
mulatas and terras pretas (Figure 52) highlight levels of enhancement that overlap the lower
end recorded in soils with abundant microscopic fragments of pottery and rubified clay. Given
that ferromagnetic minerals are considered to form rapidly as a result of near surface burning
at relatively low temperatures of 150° C (Le Borgne 1960; Tite and Mullins 1971; Mullins
1977; Allen and Macphail 1987), it is evident that near-surface burning of the soils at and near
the site has taken place. Thus near-surface burning and the presence of smaller than sand-sized
heat-treated particulates contribute to the MS signal in ways that are difficult to disentangle
(see also Sergio et al. 2006).
Chapter 5. The geoarchaeology of dark earths 115
4.1.3.2 Microscopic bone
Microscopic bone fragments are virtually absent in samples from sandy terras pretas but
are extraordinarily ubiquitous in texturally-clayey A horizon sediments from the Hatahara and
Lago Grande sites (Figure 53). Confirming the findings of previous studies (Lima et al. 2002;
Schaefer et al. 2004), some of these fragments can be taxonomically identified as fish bone
based on the lamellar structure of fossil apatite. In thin section, moreover, the overwhelming
majority are characterised by very low interference colours under XPL, pointing to overall
loss of collagen (Jans 2005). However, most fragments also show strong auto-fluorescence
under UVL, pointing to high retention of phosphorus. Data reported by Schaefer et al. (2004)
suggest that individual microscopic bone fragments at Hatahara are significant sources of Ca
and P, an inference that finds support in the high concentrations of these elements measured in
bulk samples from clayey terras pretas at the site (Table 9). However, the inference that
microscopic bone fragments constitute the most important contributors to measured
concentrations of Ca and P is not straightforward: even if ratios between Ca and P in some
bulk samples (Figure 54) resonate with the Ca to P ratio of 2.16 to 1 of pristine bone apatite
(Ca5(PO4, CO3)3(OH)), Lima (2001) demonstrates that an important part of P in bulk soils
samples at Hatahara is Al-extractable, an observation that can be construed as evidence that a
significant proportion of P is adsorbed onto clayey material (see also Lehmann et al. 2004). In
other words, although high P and Ca in these soils are most likely related to the abundance of
surprisingly well-preserved microscopic bone fragments and/or their decomposition over time
(see lower concentrations of P and Ca in faunal channels reported by Schaefer et al. 2004), it
is difficult to ascertain conclusively that the latter constitute the most significant pool of P and
Ca in these soils. A comparison of elemental concentrations and bone density at sites
progressively more distant from sources of aquatic animal protein may be a productive way to
assess their relative importance in the future.
4.1.3.3 Microscopic charcoal and soil melanisation
Micromorphological observations show that microscopic charcoal fragments constitute by
far the most significant non-inherited particulate input observed in terras pretas (Figure 55).
Because charcoal is recalcitrant and generally decays very slowly it is even observed at very
high densities in the small volume of clayey material that adheres to quartz grains in sandy
anthropogenic dark earths (17.5% of the surface area of the fine mineral fraction, thin section
NC-1.4, Table 9). Although this assessment relies on the quantification of visual estimates
from thin sections, an intrinsically subjective procedure, it provides some sense of contrasts in
overall abundance that bear on other parameters of these soils: at Hatahara, the total surface
area of microscopic charcoal fragments is 2-3 times higher in terras pretas (max 12.7 % of the
fine mineral fraction, thin section HA-3.2) than background soils (max 4.5 %FMF, thin
section HA-9.1). The density of microscopic charcoal in the A horizon of the Lago Grande
Chapter 5. The geoarchaeology of dark earths 116
terra mulata, however, is also substantial (max 12.5% FMF in thin section LG-4.2, see also
Section 5.1.2.2). High concentrations of microscopic charcoal embedded in the fine mineral
fraction (Figures 48-50, Figure 55) clearly resonate with measured Co (Leco) but comparisons
are hindered by the fact that Leco furnace data are only available for a small subset of samples
(Figure 56). Despite well-known problems in the use of Loss on Ignition to estimate the
carbon pool of clayey, Fe-rich soils (Vogel 1997), it can be asserted that the rising trend with
decreasing depth recorded in estimates of the surface area of charcoal in thin section is in most
cases consistent with that observed in available Leco furnace Co and LOI data (Table 8).
The presence and ubiquity of microscopic charcoal are of special relevance because a
number of studies (Glaser et al. 2000; Lima et al. 2002; Glaser et al. 2003; Liang et al. 2006;
Solomon et al. 2007) suggest that black carbon increases the cation exchange capacity of these
soils and also contributes to higher retention of organic matter. As noted in Section 4.1.1,
increased retention of organic matter and high inputs of pre-Columbian charcoal are partly co-
responsible for the dark colours of terras pretas (Smith 1980; Glaser et al. 2004; Topoliantz
and Ponge 2005). Micromorphological observations conducted in the context of this study
suggest that microscopic charcoal fragments in thin sections sampling the A horizon of terras
pretas generally represent poorly size classes between gravel and fine sand. Thin sections
from terra preta AB horizon samples, terras mulatas, and background soils, in contrast, show
a more balanced representation of the different size classes between silt and gravel. Different
hypotheses can be invoked to explain this contrast. First, it is possible that smaller size classes
in A horizon samples point to very efficient mechanical comminution as a result of more
intense faunal reworking. Second, it is possible that particles which become deposited in these
soils are smaller at the time they become incorporated into the soil. Whilst it is likely that the
size classes of charcoal are determined by both factors, it is worthy of note that the size of the
great majority of charcoal particles observed in these soils is consistent with the reported size
of soot particles (Masiello 2004) and pertinent to reiterate that very few microscopic pottery
fragments tempered with organic fibres are observed in thin sections. The latter observation is
surprising given that shards of the Açutuba, Paredão and Guarita phases are reported to use
caraipé as a tempering agent (Hilbert 1968; Neves 2003; Lima et al. 2006; Moraes 2006).
The observations presented above evidently support the suggestion that black carbon
enhances organic matter retention: as pointed out in Section 4.1.1, all samples with abundant
microscopic charcoal – terras pretas, terras mulatas and even the A horizon of the Hatahara
background soil (Table 9) – show the brown colours that soil micromorphologists generally
gloss as organic staining. Some sense of a grading towards lighter colours with decreasing
density of charcoal fragments can be ascertained after repeated comparative observations.
However, it was earlier mentioned that the fine mineral fraction of the A horizon of terras
pretas shows generally darker brown hues under PPL, a generally undifferentiated b-fabric
Chapter 5. The geoarchaeology of dark earths 117
under XPL, and – in some cases – very dark grey colours under OIL. Indeed, it can be stated
that A horizon samples from terras pretas vary between two poles: very dark brown colours
(PPL/OIL) and a dark undifferentiated to marginally speckled b-fabric (XPL), and very dark
brown (PPL), dark ‘opaque’ grey (OIL) colours with an undifferentiated b-fabric (XPL). It is
important to emphasise that these contrasting optical characteristics do not necessarily reveal a
higher density of microscopic charcoal fragments: even considering wedge effects of thin
sections, it is likely that these more ‘opaque’ grey colours reveal some impregnation of the
fine mineral fraction with sesquioxides, an assessment discussed in further detail below.
4.1.3.4 Plant matter, fresh and ashed
A noteworthy aspect of the chemical composition of soil samples from settlement-related
anthropogenic dark earths is that total concentrations of Ba, Cu, K, Mg, Mn, Sr and Zn, and to
a lesser extent, P and Ca, show strong co-patterning, especially when examined by depth
(Figure 57). This depth-wise patterning is extremely interesting and provides important clues
about the formation of anthropogenic dark earths (see Section 5). Based on existing
knowledge (Chapter 2), and aside from the microscopic particulates I have discussed
previously, sources for these high elemental concentrations can be expected to reflect a variety
of additional inputs, including ash, plant matter, shell remains, urine and excrement (Kern et
al. 2004; Woods and Glaser 2004) at middens, food-processing areas, and gardens (Andrade
1986; Kern 1996; Kern et al. 2004; Schmidt and Heckenberger 2006). Of these, the possibility
that ash constitutes a significant input in settlement-related anthropogenic dark earths has been
underemphasised in recent investigations. Aside from generic mention in the kitchen-midden
model (Chapter 2, Section 4) and highly significant research presented by Hecht (2003; Hecht
and Posey 1989), ‘ash’ is not even an entry in the index of the two most recent books on
anthropogenic dark earths (Lehmann et al. 2003; Glaser and Woods 2004).
This lack of attention is somewhat surprising because ash is produced in copious quantities
in most kinds of burning activities, including cultivation practices that range from house
gardens to slash and burn agriculture (Carneiro 1961; Harris 1971; Carneiro 1983; Beckerman
1987; Hecht and Posey 1989; Texeira and Martins 2003; Denevan 2004); combustion of
middens of various kinds (Hecht 2003), domestic and cooking fires (Zeidler 1983), including
the processing of bitter manioc and the preparation of ipadú (pers. obs., Tiquié river, 2001, see
also Hugh-Jones 1979); combustion associated with the firing of pottery (e.g. DeBoer and
Lathrap 1979); and – of particular relevance from an archaeological point of view –
combustion associated with the preparation of specific ceramic tempers (“On the Amazons the
clay intended for the manufacture of pottery is mixed with the ash of the Caraipé tree”: caraipé
is made by burning the bark of Licania octandra, see Hartt 1879:81 for a detailed description).
Chapter 5. The geoarchaeology of dark earths 118
Ash, in short, must have been one of the most common by-products of settlement-related
activities during occupations by pre-Columbian ceramic communities.
Ash is generally an alkaline sediment (pH=9-13.5) that applied as an amendment can raise
the pH of the upper centimetres of the soil at least temporarily (Ludwig et al. 1999). Studies of
the chemical composition of plant ash in a variety of contexts show that it is rich in Ca, K,
Mg, Si yet also includes significant but varying concentrations of Al, Na, Mn, P and Fe, and
trace quantities of Zn, Na, Ba, Cu and Sr (Etiégni and Campbell 1991; Pierce et al. 1998).
Hecht’s (2003) research shows that different concentrations of Ca, K, Mg, N, and P are found
in ashes from taxonomically-specific plant matter. These specific signatures reflect the
different nutrient up-taking capacity of different species, and undoubtedly reflect nutrient
solubility and availability in soils, which in turn depend on the latter’s parent material.
Research by Durand et al. (1999) highlights that specific anatomical parts of particular plant
taxa concentrate metals more efficiently than others: in what undoubtedly resonates
significantly with the preparation of caraipé for the tempering of pottery, they show that
concentrations of specific metals are 10 times higher in bark compared to those measured in
the sapwood and heartwood of the same tree species at Chaco Canyon, New Mexico.
Microscopic studies of archaeological sediments show that, given appropriate preservation
conditions, pseudomorphs of plant calcium oxalate crystals (CaC2O4.H2O or 2H2O) can be
readily recognised through soil micromorphological analysis (Courty et al. 1989; Schiegl et al.
1996; Arroyo-Kalin 1999; Arroyo-Kalin et al. 2007; Canti 2003; Araújo et al. 2008).
Notwithstanding, as is highlighted by other studies of strongly melanised anthropogenic soils
(Courty et al. 1989:111; Cammas 2004) there exists a low preservation potential in
sedimentary contexts without strong stratification (Brochier 2002), intense faunal reworking,
and – at least initially – low pH. Unsurprisingly, therefore, neither ash crystals nor other forms
of calcium carbonate have been identified in any of the thin sections discussed in this chapter
despite very high concentrations of Ca measured in bulk samples. Notwithstanding, a number
of arguments indirectly supports the suggestion that ash may have been a highly significant
input in settlement-related dark earths.
First, some anthropogenic A horizon samples contain unexpected concentrations of illuvial
clay coatings (Figure 58): a number of studies suggest that potassium derived from weathered
ash can encourage clay illuviation under moderately acid conditions (Slager and van der
Wetering 1977; Courty et al. 1989:113; Macphail 2003) and hence it is not infrequent that soil
micromorphologists interpret these illuvial features as evidence of ash. Second, anthropogenic
A horizon samples contain common phytoliths that show weak to moderate auto-fluorescence
under UVL (Figure 59). Auto-fluorescence of silica under UVL has been related to the
formation of an Al coating when silica is exposed to high temperatures (Y. Devos, R.
Chapter 5. The geoarchaeology of dark earths 119
Macphail, pers. comm. 2007) and, indeed, is also observed in pottery- and soil-embedded
sponge spicules. Given that both phytoliths and sponge spicules are made of silica, the
obvious implication is that phytoliths have been burned at high temperatures. Third, higher Al
concentrations than background sediments are measured in all studied exposures of terras
pretas, with particularly significant increases in earthworks at Hatahara and Lago Grande
(Table 8). The dissolution of Al minerals and their complexation with organic matter (Ritchie
1994; Wong and Swift 1995; Haynes and Mokolobate 2001) is an insufficient explanation for
these values given that ICP-AES measurements approximates total Al concentrations. Pierce
et al. (1998) report that plant ash shows an average ratio of Ca:Al of around 11:1. If most Ca
in soils comes from ash, the proportional ‘gain’ in Al concentrations recorded in clayey dark
earth at Hatahara and Lago Grande would be commensurate with this ratio, perhaps providing
some of the raw material for the neoformation of soil.
If ash was consistently deposited on cleared and inhabited soil surfaces in pre-Columbian
times, one would minimally expect a systematic rise in soil pH and an in loco concentration of
plant-borne nutrients and others (e.g. phytoliths). As soil pH increased, one would expect that
some of these metals would adopt insoluble forms (Vitousek and Sanford Jr 1986; Burnham
1989; Schaetzl and Anderson 2005), in turn permitting their concentration in the soil. This
model obviates the need to suggest a geological origin for high elemental concentrations in
anthropogenic dark and explains why strong co-patterning by depth is observed (see also
Ruivo et al. 2004). Among these elements, the fact that Mn shows a relatively linear relation
to MS values at different terra preta expanses (Figure 60) could indicate that Mn substitutions
in otherwise anti-ferromagnetic iron forms, such as haematite (Wells et al. 1999), contribute to
overall higher MS values in settlement related dark earths. In this context, the two poles in
colour exhibited by the fine mineral fraction of terras pretas (Figure 49 and Figure 55) – very
dark brown colours (PPL/OIL) + dark undifferentiated to marginally speckled b-fabric (XPL)
vis-à-vis very dark brown (PPL) + dark ‘opaque’ grey (OIL) colours with an undifferentiated
b-fabric (XPL) – could indicate impregnation with Mn sesquioxides. Put another way, the
consistent deposition of ash may not only be co-responsible for high pH but also induce the
mineralization of plant-borne Mn into the soil. The transformation of Mn(II) into Mn(IV) by
bacteria and fungi would lead to the formation of oxides that interact with organic matter and
microscopic charcoal to produce melanisation. In this connection, the well-established ability
of Mn oxides to adsorb a wide range of metals (Tebo et al. 2004) deserves to be mentioned.
4.1.4 Summary
The preceding observations and comparisons have shown that chemical and physical
parameters of anthropogenic dark earths vary with depth at any given exposure, showing
much lower measurements in sediments of the B horizon. These parameters also show
Chapter 5. The geoarchaeology of dark earths 120
significant differences in sandy versus clayey exemplars, a result of the fact that sandy soils do
not assist preservation of small particulate materials and that depletion of the fine fraction, an
outcome of processes of regressive erosion, skews the volume of sediment onto which
elemental concentrations of various elements can be adsorbed. Small particulates that include
pottery, rubified clay aggregates, sponge spicules, bone, and charcoal are observed in large
quantities in most A horizon samples of clayey terras pretas but relating their composition to
actual chemical and physical measurements and/or identifying the activities that resulted in
such inputs is not straightforward. Thus P and Ca could originate in bone apatite but are
equally expectable elements with mineralised plant matter; magnetic susceptibility might track
the ubiquity of shard and rubified clay fragments but equally must reflect near-surface burning
on the soil. Microscopic charcoal is mostly comminuted to silt size in terras pretas but it
cannot be easily ascertained whether this reflects mechanical comminution in the soils or is a
result of inputs of small-sized charcoal, such as caraipé, or even fine silt-sized black carbon
particles, such as soot. However, the smallest microscopic charcoal particles can be resolved
using the optical microscope such that it can be stated that charcoal inputs are not the only
factor contributing to melanisation of A horizon sediments. An hypothetical scenario that
explains some colour contrasts may relate to high concentrations of Mn, Ba, Cu, K, Mg, Sr
and Zn derived from organic matter. If organic matter is consistently ashed, the resulting
higher pH might lead to the concentration of Mn in the form of oxides, contributing to the
dark colour of the fine mineral fraction observed in thin section and explaining why some of
these soils appear to be darker than others.
5. EXAMINING SITE FORMATION PROCESSES: THE PEDO-STRATIGRAPHY
OF ANTHROPOGENIC DARK EARTHS
The majority of terra preta expanses in the central Amazon region are open air
archaeological sites that track the location of pre-Columbian settlements on relatively flat,
mostly non-flooding landforms in the immediate vicinity of rivers, lakes and streamlets
(Chapter 4). As noted previously, vertical exposures through ‘flat’ areas within these expanses
reveal a deeper A horizon than the surrounding soil mantle. Within the A horizon it is
generally possible to distinguish one or more subhorizons – A1, A2, A3 and so forth – based
on subtle contrasts in soil structure, texture, colour and inclusions (Figure 61). The transition
from A to underlying B horizon sediments, in turn, often appears as an AB, A/B and/or B/A
sequence that shows down-mixing of enriched A horizon material into deeper B horizon
sediments (Figures 42-45). These characteristics appear to be shared by many exemplars of
anthropogenic dark earths in the tropical lowlands of northern South America (e.g. Mora
1991; Kern 1996; Vacher et al. 1998; see Kämpf et al. 2003 for an overview).
Chapter 5. The geoarchaeology of dark earths 121
Research in the central Amazon region for the most part shows that ceramic shards
embedded in expanses of terras pretas can be classified into phases whose associated
radiocarbon dates are constrained to a few hundred years (Chapter 4). Moreover,
archaeological remains deposited within thicker and darker A horizon sediments are generally
in ‘good’ stratigraphic order, i.e. older artefacts are generally found underlying younger ones.
It is important to highlight that the stratigraphic integrity of these remains cannot be explained
by invoking their concerted sinking as a result of faunally-induced gravitational displacement
(Darwin 1881; Johnson 1990): not only do vertical exposures of anthropogenic dark earths
lack horizontally transgressive alignments of ceramic shards that could be interpreted as
analogues of biotically-produced stone lines, but carefully-controlled excavations also
frequently record archaeological features – pits, post hole negatives, and the like – whose very
presence and edge definition contradict the suggestion that these deposits have been reworked
by soil fauna to the point of obliterating stratigraphic distinctions. Thus, whilst it cannot be
doubted that the A horizon of terras pretas is a result of the deposition and/or decomposition
of debris associated with pre-Columbian settlement dynamics (Section 4.1.3), to characterise
the dark and organic-rich sediments of these soils as thick A horizons that have expanded
downwards understates the exact nature of the processes that resulted in their formation
(Woods 1995).
Over 35 years ago, Lathrap (1970a) vehemently defended the suggestion that stratigraphic
distinctions were visible or inferable in vertical sections of Amazonian open air sites and
advocated their study as an integral part of reconstructions of pre-Columbian history. The
approach rehearsed in the following analysis is a first attempt to operationalise the general
thrust of his remarks from the vantage point of geoarchaeological data. A pedo-stratigraphic
approach, it is offered, attempts to reconstruct the role of both horizonation and sedimentation
processes in the formation of these deposits by postulating land surfaces and examining their
burial over time (Kemp et al. 1994; Woods 1995; Vacher et al. 1998). Of necessity this
requires that micromorphological characteristics of specific profiles and depth-wise patterning
in physical and chemical measurements be explored in much more detail than heretofore. It
also necessitates that the actual characteristics of background soils be specified much more
comprehensively.
5.1.1 The Hatahara site: settlement soils (Profiles HA-1, HA-3,
HA-5, and HA-9)
Archaeological understandings of the Hatahara site have been presented in Chapter 4 (see
Section 3.2.2.3) and the main macroscopic characteristics of the four studied profiles have
been briefly summarised in Section 3 of this chapter. The four sampling exposures consist of
profile HA-9, which represents a background soil profile; profile HA-5, the excavation profile
Chapter 5. The geoarchaeology of dark earths 122
of the Urns’ Unit, i.e. a ‘flat’ area of the site in which no earthworks are visible; and profiles
HA-1 and HA-3, each of which samples the sediments that make the overburden and buried
terrain under, respectively, Mounds 1 and 2 (Figure 62).
5.1.1.1 Profile HA-9 (background profile)
The modal characteristics of ‘background’ clayey Oxisols at Hatahara have been studied
by sampling an exposure located at the point where the terra firme bluff falls towards one of
the deep ravines that flank the landform. This exposure, located a few hundred meters from
the core of the archaeological site, lacks any evidence of archaeological artefacts but, as
discussed below, records evidence of burning during sub-recent times. In the field, the soil
profile shows a relatively thin A horizon that grades into a thinner AB horizon, below which a
BE horizon is observed overlying the upper part of a B horizon (Figure 63).
From a micromorphological perspective (Table 10), the organisation of A and AB horizon
sediments can be characterised as a composite, decreasingly faunally-reworked, granular to
massive microstructure formed by irregularly-shaped peds resulting from the coalescence of
subangular to rounded aggregates of different sizes (50-200 µm; 500-1500 µm; 2-7 mm).
Larger, more organically-stained (PPL) aggregates are more common in the A than the AB
horizon. In the A horizon, the clayey material that makes up aggregates expresses an
undifferentiated b-fabric (XPL), and include remains of ‘fresh’ plant matter such as rootlets
and tissue (Figure 47), common gravel to silt sized charcoal fragments, common phytoliths
showing weak auto-fluorescence under ultra violet light (UVL), and rare silt-sized burnt soil
fragments, best observed as bright orange (OIL) clay fragments. AB horizon sediments show
only light organic staining, about half the microscopic charcoal, and lack all but very rare
plant fragments. BE and B horizon sediments are organised as poorly separated continuous
zones of slightly vughy, massive, limpid yellow clay (PPL), the BE showing depletion of iron
(OIL) and a speckled b-fabric (XPL), the Bt showing more intense impregnation with iron
sesquioxides (OIL) and a striated b-fabric (XPL). Both the BE and the B show zones with fine
sand-sized faecal pellets whose optical features are identical to the surrounding matrix, i.e. can
be considered as relict evidence for a granular fabric (Schaefer 2001; Lima et al. 2002). Both
horizons also show isolated particulate material of organic origin – mainly charcoal – that is
either embedded in intrapedal position or within small faunally-produced clayey aggregates
whose degree of organic staining suggests an origin higher in the profile. Generally fine sand-
sized typic iron nodules increase in frequency from the AB to the B horizon. Common illuvial
clay coatings identify a Bt horizon.
Table 11 summarises available physical and chemical parameters for the HA-9 profile and
Figure 64 plots some of the most salient by depth. These data show that sediments from the A
Chapter 5. The geoarchaeology of dark earths 123
horizon are characterised by higher MS, Ct, Co, LOI, P, Mn and Cu as well as slightly higher
pH values compared to sediments lower in the profile. The presence of phosphatised plant
fragments, organic punctuations and organic staining of the fine mineral fraction suggests that
the most likely source of higher Co, P, Mn and Cu is the decomposition or mineralization of
plant matter. A sharp rise in MS values from 50 to approximately 130 SI units towards the
surface, coupled with observations of charcoal fragments, auto-fluorescent phytoliths and
burnt soil fragments suggest this locale has experienced near surface burning, most likely
associated with sub-recent clearance and agricultural activities. Although a shallow fall-off
pattern characterises most variables, LOI shows higher values down to the bottom of the AB
horizon, pointing to a combination of the contribution of not infrequent gravel-sized charcoal
down to 35 or so cm and interferences in the technique expected in Fe-rich clayey soils (Vogel
1997).
5.1.1.2 Profile HA-5 (Urns’ unit, terras pretas)
The preceding observations and previous research (Lima et al. 2002; Schaefer et al. 2004)
provide a comparative basis to examine a vertical exposure through anthropogenic dark earths
developed on the same landform. A summary of the stratigraphy observed during
archaeological excavations has been provided in Section 3.2.2.3 of Chapter 4.
From a micromorphological perspective (Table 12) the microstructure of the A horizon of
Profile HA-5 varies from a complex assortment of irregularly-shaped microscopic peds
resulting from the coalescence of faunally-produced aggregates (thin section 1) to irregular,
massive, slightly vughy continuous clayey zones with little evidence of faunal reworking (thin
section 2). The fine mineral fraction of this clayey material shows very dark brown colours
(PPL), a dark ‘opaque’ grey colour (OIL), and a completely undifferentiated b-fabric (XPL).
Aside from channel/chambers deriving from rootlets and perhaps faunal action, peds are
fractured post-depositionally by thin planar voids (especially thin section 2), pointing to
compaction and desiccation (also noted during excavations, see Rebellato 2007:107).
Unusually for A horizon sediments, dusty illuvial clay coatings with low interference colours
are observed (Figure 66, top) on planar voids and vughs, suggesting the deposition of ash
(Slager and van der Wetering 1977; Courty et al. 1989; Macphail 2003). Embedded
intrapedally are silt to sand-sized quartz grains; abundant fine sand to silt-sized charcoal
fragments; common microscopic pottery fragments; common fine sand to coarse silt-sized
rubified clay aggregates; common auto-fluorescent sponge spicules; common, generally
medium to fine sand sized, phosphatic (UVL) fragments of microscopic bone; common auto-
fluorescent silica phytoliths; and rare burnt soil fragments (Table 12; see Figure 55, centre left,
for charcoal).
Chapter 5. The geoarchaeology of dark earths 124
AB horizon sediments show some remarkable differences. Noteworthy is the fact that the
density of microscopic charcoal is not only lower than overlying, strongly melanised
sediments but also includes a better representation of size classes between silt and gravel,
including more frequent charred plant organs and tissue (Table 12). Thin section 3 (90-100
cm), in addition, evidences two contrasting fabrics in terms of texture, abundance of
microartefacts and microscopic charcoal fragments (Figure 66, bottom). Whilst both fabrics
include in-mixed peds from each other (as well as from higher in the profile and the lower B
horizon), they are separated by a clear microscopic unconformity that evidences a sharp pre-
Columbian age truncation of the deposit. A long planar void in which dusty illuvial clay
coatings accumulate runs slightly above this unconformity. This arrangement can be
interpreted as evidence that a re-organised, better sorted, artefact- and charcoal-rich clayey
sediment resembling the A horizon of the background Oxisol has been re-deposited on a
truncated but relatively in situ, faunally reworked, AB-like sediment in which low densities of
microscopic charcoal fragments, sponge spicules, pottery fragments and bone are present. It
most likely represents the bottom of a pit-like feature that is no longer visible to the naked eye
but has survived reworking by soil fauna.
The full import of these observations emerges when data from physical and chemical
analyses are examined (Table 13, Figure 67). Al concentrations of 30000 ppm below about
35-7 cm are markedly higher than the background soil profile, showing a decrease to about
25000 ppm towards the surface. Fe concentrations show important fluctuations with depth,
shifting from ~44000 ppm at 125-7 cm to ~52000 ppm at 105-7 cm, decreasing above this in a
similar fashion to the background soil profile up to 35-7 cm, and above this decreasing further
to lower levels of ~32000 ppm. But it is the trends in pH, LOI, P, Ca, Mn, Ba, Cu, K, Mg, Na,
Sr, Zn, and MS values, in all cases much higher than those recorded at the background soil
profile, that require special attention. Depth-wise trends in these variables do not show the
pattern of consistent decrease from the present surface that might be expected from a ‘down-
mixing model’, but instead evidence a series of distinctive inflections, especially in MS and
LOI values (no Leco furnace data are available for profile HA-5), below which fall-off
patterns can be readily observed.
The lowermost of these inflections, at 115-7 cm, not only shows levels of
enrichment/enhancement that are higher than under and overlying sediments but the fall-off
pattern of most measured variables with increasing depth immediately recalls the transition
from an A to an AB horizon observed in the background profile HA-9. Importantly, MS
values at 115-7 cm in Profile HA-5 exceed those construed as a benchmark of near-surface
burning at HA-9, suggesting that recorded at this depth in the deposit is a buried land surface
which was minimally cleared through burning. The depth of the reconstructed land surface is
consistent with that of archaeological remains found in stratigraphic excavations: pits with
Chapter 5. The geoarchaeology of dark earths 125
pottery classified as Açutuba phase, as well as other wares that can be classed as model-
incised or Barrancoid, reach down maximally to 135 cm but are not found higher than 120 cm
except in higher pit features. As noted in Section 3.2.2.3 of Chapter 4, unstructured
concentrations of remains that at first glance appear to be Manacapuru phase are found at
about this depth. Thus the reconstructed land surface recorded at 115-7 cm should maximially
date date to the first half of the 1st millennium AD (Machado 2005; Lima et al. 2006) and may
well represent an older and as yet insufficiently described occupation at the site (see Section
5.1.1.4.3, below).
Above 115-7 cm, a shift towards higher MS and LOI only takes place between 97 and 85
cm. As noted previously, however, micromorphological data (thin section 3, 90-100 cm)
suggests that sediments at this depth constitute an AB horizon which has been truncated prior
to deposition of non-strongly melanised, organic-rich A-like horizon material. An obvious
corollary is that somewhere above 85-7 cm a surface with a developed A horizon existed in
the past. MS values, which are relatively stable between 85-7 and 75-7 cm, suggest this A
horizon might be recorded at 75-7 cm, where substantial enrichment with P, Ca, Mn, Ba, Cu,
K, Mg, Na, Sr, Zn and a slightly higher pH are observed, in effect identifying a second surface
of accumulation in the deposit. The land surface recorded at 75-7 cm seems congruent with
the depth of some of the burial urns unearthed during excavations, which as noted previously
have been suggested to reflect the transition between Açutuba and Manacapuru phases (Neves,
pers. comm., 2007).
Above this, a dramatic increase is observed in all measured variables prior to a new
inflection in MS at 55-7 cm, the approximate depth of thin section 2 (50-60 cm). Like the 115-
7 cm land surface, the shape of the MS and LOI curves from 55-7 cm to 75-7 cm recalls the
transition from an A to an AB horizon, i.e. suggests down-mixing of anthropogenically-
enriched sediments from a higher land surface recorded at about 60 or cm. Rebellato
(2007:132-133) reports that only Manacapuru phase pottery is recorded below 60 cm whilst
both Manacapuru and Paredão phase material occur above this depth. Considered from a
pedo-stratigraphic perspective, this implies that the surface recorded at 55-7 cm in the profile
is a significantly enriched/enhanced A horizon that most likely dates, going by the radiocarbon
chronology produced during excavations of Mound 1, to Manacapuru occupations of the 5th to
7th centuries AD (Chapter 4, see also Machado 2005). A significant rise in Mn concentrations
above this depth is noteworthy in light of discussions about factors that impinge on
melanisation of these soils (see Sections 4.1.3.3 and 4.1.3.4).
Although no ICP-AES data exist for 45-7 cm, an inflection in MS between 55-7 and 45-7
cm and a shift in LOI values suggest a brief ‘hiatus’, most likely pointing to burial of a surface
by the conveyor up-mixing activity of soil fauna (Vacher et al. 1998; Johnson et al. 2005a)
Chapter 5. The geoarchaeology of dark earths 126
followed by intense accumulation of debris associated with settlement activities. The latter is
indicated by a sharp rise in the density and weight of ceramic shards (Rebellato 2007:118-
119), previously mentioned micromorphological observations (abundance of microartefacts
and charcoal fragments), and a consistent rise in concentrations of P, Ca, Mn and others from
55-7 cm and upwards. A peak at 35-7 cm, which approximately maps onto the boundary
between the A2 and A3 horizon, should not detract attention from the fact that measured
concentrations above and below are equivalent. The presence of Paredão phase pottery above
60 cm and up to 16 cm suggests that strongly melanised dark earths can be associated with
this context and occupation of the locale. Chronological evidence from Mounds 1 and 2
(Chapter 4 and see below) suggests Paredão phase occupations take place between the 9-12th
century AD. On the other hand, it cannot be overruled – especially in view of low EC and high
pH values – that recorded above 35-7 cm is yet another surface of accumulation. The presence
of grooving and incised decoration towards the upper part of the deposit (Rebellato 2007:115,
Gráfico 5.1.4.) may indicate that this surface is related to Guarita phase occupations at the site,
which takes place after the Paredão occupation and reach approximately to the 15th century
AD (Neves 2003; Machado 2005). Be that as it may, depth-wise trends in physical and
chemical data for sediments between 55-7 and 15-7 cm suggest that this sediment zone needs
to be understood as an outcome of build-up of the deposit (Woods 1995; cf. Vacher et al.
1998).
Above 15-7 cm, finally, near surface sediments record sharp increases in LOI, EC and pH
coupled with a drop in MS, the latter most likely tracking a decrease in sustained burning over
time. In general, these values reflect the compounded effects of more intense faunal activity,
plant nutrient uptake, incorporation of organic matter, and sub-recent agriculture. It needs to
be emphasised, however, that these trends overrule the suggestion that the proximity of near
surface processes affects the properties of sediments below 15-7 cm. For instance LOI weight
loss values, which should theoretically record down mixing of organic matter and charcoal
from the present surface, are actually lower at 15-7 cm than between 25-7 and 65-7 cm. Whilst
this could point to a thin, near surface eluvial horizon, the consistency between archaeological
artefacts and the sediment zones previously discussed is sufficiently overwhelming to question
this interpretation.
5.1.1.3 Profiles HA-1 and HA-3(Mounds 1 and 2, terras pretas)
Striking similarities and some significant contrasts are observed in micromorphological,
physical and chemical data from HA-1 and HA-3 (Tables 14-17, Figure 70). At both
exposures it is possible to reconstruct with reasonable accuracy the processes that shape the
build-up of the buried land surface and also assess the main characteristics of the overburden
of either mound.
Chapter 5. The geoarchaeology of dark earths 127
5.1.1.3.1 The buried land surfaces under Mounds 1 and 2
176 cm and below (Layer I horizon in both mounds): Sediments of Layer I at both
mounds resemble the Bt horizon of HA-9 in terms of microstructure, texture, optical
characteristics of the fine mineral fraction, and presence of illuvial clay coatings. Leco furnace
data, available for Mound 1 at 196 cm, suggest organic carbon is 0.38%, constituting 62% of
total carbon (0.61%). Physical and chemical data at 176 cm at both mounds show rising pH
values which, in overlying sediments, drop (Mound 1) or remain high (Mound 2). At both
mounds, a sharp rise in LOI weight loss is accompanied by sharp inflections towards lower
EC values and a slight rise in MS values, the latter to magnitudes that are below the near-
surface burning benchmark at HA-9.
136-176 cm (Layer II/AB horizon in Mound 1, Layer III/AB horizon in Mound 2): Thin
sections from both mounds show significant quantities of microscopic charcoal and
microartefacts embedded in the fine mineral fraction of sediments. At Mound 2, thin section
HA-3.6 shows peds from two sources: one, characterised by lighter organic staining, fewer
microartefacts, and some microscopic charcoal, suggests a non-strongly melanised A horizon
with settlement debris; another, characterised by strongly organically-stained material with
microartefacts and microscopic charcoal, suggests an origin higher in the profile. Subangular
blocky peds of limpid yellow clay fabric that cannot be easily associated with faunal action are
also observed. At Mound 1, thin section HA-1.6 (165 cm) shows subangular blocky peds like
HA-3.6 and thin section HA-1.5 (140 cm) shows a long (1.7 x 0.5 cm) unbroken irregular ped
and intrusive clayey aggregates with a low degree of organic staining and some silt-sized
charcoal. These features suggest a non-strongly melanised A horizon.
At both profiles this evidence can be related to physical and chemical data as follows:
below ~136 cm. pH values drop (Mound 1) or are constant (Mound 2) between 176 and 156
cm, then rise at 146 cm and drop off slightly at 136 cm (both mounds). This pattern is
accompanied by a shift to low EC values (at Mound 1, where data are available, it also goes in
hand with a sharp inflection in Na concentrations) and a sharp rise in MS between 146-136 cm
to values comparable to the present land surface of profile HA-9. Leco furnace data for
Mound 1 suggest Co is 1.22%, representing 75.31% of Ct, much higher than the Ap horizon of
the background HA-9. At both mounds, P, Ca, Mn and related variables at this depth are
comparable to those observed between the 76 cm land surface and the A2 horizon at HA-5
(the urn cemetery unit). This evidence supports the existence of a land surface with evidence
of near-surface burning at around 150 to 130 cm at both of the profiles under discussion.
105/110-136 cm (Layer III/Ab in Mound 1, Layer IVa.1/Ab horizon in Mound 12): a
thoroughly faunally-reworked microstructure formed by irregularly-shaped peds resulting
Chapter 5. The geoarchaeology of dark earths 128
from the coalescence of aggregates of different size (50-200 µm; 500-1500 µm; 2-7 mm) is
recorded as the dominant fabric of thin sections HA-1.4 (Mound 1: 115-125 cm) and HA-3.5
(Mound 2: 105-115 cm). In both samples abundant microscopic charcoal, auto-fluorescent
phytoliths, and microartefacts are observed embedded in the fine mineral fraction, which is
strongly organically-stained, expresses an undifferentiated b-fabric, and shows dark brown
colours under OIL. In contrast with thin sections immediately higher in the profile (Mound 1:
HA-1.3, 100-110 cm; Mound 2: HA-3.4, 80-90 cm), thin sections HA-1.4 and HA-3.5 show
intrusive aggregates indicating mixing with a less-organically-stained fabric. Both samples
also show marginal illuvial clay coatings in fine planar voids fracturing larger peds. At Mound
2, thin section HA-3.5 shows strong indications of a subangular blocky structure, pointing to
near surface processes.
Physical and chemical data reflect these characteristics as follows:
At Mound 1 (HA-1) a zone of relatively constant pH below 106 cm, MS values that rise
sharply from 116 to 106 cm and a small but significant increase in LOI weight loss between
116 to 106 cm highlight that the land surface under the mound was strongly modified prior to
the formation of the earthwork. However, the relatively similar Al concentrations at 116 cm
compared to sediments lower in the profile and the fact that optical characteristics of the fine
mineral fraction of thin section HA-1.3 (100-110 cm, immediately below Layer IVa, the lower
pottery line) are more similar to those observed in HA-1.2 (50-60 cm), which samples
sediments in Layer IVb (above the pottery line), suggest that the mound overburden starts at
around 110 cm. Consequently, observations and measurements on sediments immediately
below 110 cm (HA-1.4) can be considered to represent a reworked portion of a land surface
buried by Mound 1. P, Ca, Ba, Cu, K and Mg all far exceed measured concentrations in the
A2 of HA-5 (the urns unit). However, Mn, Sr and Zn, as well as Na, MS and LOI weight loss
are lower than measured in the A2 horizon at HA-5.
At Mound 2 (HA-3) a very sharp rise is observed between 116 and 106 cm in MS. It is
accompanied by a shift from low EC values at 116 cm to relatively higher EC values at 106
cm. A pH of 6.3 at 116 cm is lower than a peak at 126 cm, and is accompanied by a decrease
in Na concentrations compared to sediments below and above in the profile. A sharp rise is
also observed in LOI weight loss from fairly constant values in the 136-116 cm depth interval
to higher values at 106 cm. At this depth in the profile concentrations of P, Ca, Mn and other
variables (not Na) also rise sharply with respect to measurements at 146 cm, effectively
becoming comparable to values in the A2 horizon in HA-5. Somewhere above 116 cm,
finally, a shift in Al concentrations towards much higher values takes place.
Chapter 5. The geoarchaeology of dark earths 129
To summarise the evidence for the land surface buried by both mounds, it can be stated
that consistent patterns in the micromorphological, physical and chemical data are observed
between both exposures. Al and Fe concentrations show trends that in broad terms compare
well with those observed in profile HA-9 and in sediments below 56 cm in profile HA-5.
These patterns suggest that at around 136 cm in both profiles – sediments that presently
constitute the AB horizon – an old land surface was exposed to fire use at levels sufficiently
intense to produce a signal in magnetic susceptibility values. Above this, the actual land-
surface that was buried by each of the mounds – noted as an Ab during field description – can
be ascertained using micromorphological and chemical parameters around 105-110 cm at both
mounds.
5.1.1.3.2 The overburden of Mounds 1 and 2
From a micromorphological point of view, thin sections HA-1.3, 1.2 and 1.1 from Mound
1 and HA-3.4, 3.3 and HA-3.2 from Mound 2 share: a) strong organic staining (PPL), high
impregnation with manganese sesquioxides (OIL) and undifferentiated b-fabric (XPL) in the
fine mineral fraction; b) more microscopic bone fragments that the buried surface (peaks occur
at around 50 cm in Mound 1 and between 55 to 80 cm in Mound 2); c) more abundant
microartefacts than the buried surface (peaks occur at a similar depth than bone fragments); d)
very high, upwards increasing abundance of microscopic charcoal fragments (in general fine
silt-sized charcoal is more important just above the buried land surface, i.e. Layer IVa in
Mound 1, Layer IVa.2 in Mound 2); e) ubiquitous auto-fluorescent phytoliths. These
observations evidence that sediments making up the overburden at both mounds (Mound 1:
Layers IV and V; Mound 2: Layer IVa.2 to Layer V) are much more enriched with
microscopic debris – bone, microartefacts, charcoal, ash - compared to those that form the
underlying land surface.
Salient aspects of the physical and chemical data include: a) P and Ca concentrations
increase well in excess of those measured in the buried land surface but peak at 56 cm in
Mound 1 and at 86 cm in Mound 2. These peaks show good correspondence with abundance
of bone in thin section but could also reflect higher incorporation of plant ash. b) Higher
magnetic susceptibility in the overburden of both mounds with respect to the buried land
surface: as discussed previously this reflects a higher density of near surface burning and more
inclusions of heat treated Fe-rich particulates. Mound 1 evidences a continuous increase in MS
up to 36 cm, pottery Line IVc. In contrast, Mound 2 shows relatively constant MS values
above the peak in P and Ca, with an inflection associated with the higher pottery line in Layer
IVb (at 40-55 cm). Both mounds record sharp rises between 26 and 16 cm. c) Mound 1, for
which Leco furnace data are available, shows levels of Co that rise from 2.14% at 86 cm, to
2.55% at 46 cm to 3.76% at 16 cm, representing over 81% of total carbon. LOI weight loss for
Chapter 5. The geoarchaeology of dark earths 130
both earthworks reveals a ‘stepped’ pattern that is co-ordinated between both mounds. d)
Finally, both mounds record a shift towards higher Al and lower Fe values compared to the
underlying buried land surface. A shift in Fe values toward much lower concentrations is
particularly noticeable above 56 cm and 46 cm in either mound. A shift towards higher Al
values, as problematised in the discussion about composition, can be related to the deposition
of ash-borne Al.
These trends identify four separate sediment zones at both mounds, minimally bracketed
as follows:
110-86 cm: In Mound 1 the top bracket is given by layer IVa (80-100 cm), the lowermost
pottery line. Sediments in this zone show a marked increase in Al and an important decrease
in Fe concentrations with respect to the buried land surface. A pH peak of 6.7 at 96 cm
followed by low EC values at 86 cm suggest an exposed surface prior to deposition of Layer
IVa. In Mound 2 the top bracket is given by peak Ca, P, Mn, K, Mg concentrations at 86 cm
as well as by distinctive Al and Fe concentrations with respect to those above and below.
86 to 56 cm: In Mound 1 the top bracket is given by changing Fe concentrations at 56 to
46 cm, a marked rise in LOI weight loss, and peak P and Ca concentrations. These trends can
be interpreted as analogous to the 110-86 zone in Mound 2 but, as discussed below, rather
than burial of an accreting deposit the upper bracket appears to signal a truncation. In Mound
2, MS rises up to 46, the same sharp increase in LOI weight loss is observed, and a slight
inflection can be observed in P and Ca concentrations. A dense pottery concentration (middle
of Layer IVb) between 40-56 cm brackets the sediment zone in a fashion somewhat analogous
to the 110-86 zone in Mound 1.
56-26 cm: In both mounds Fe concentrations decrease sharply, a shift not accompanied by
a drop in Al concentrations of correlative magnitude. P and Ca also decrease to values lower
than 86-56 cm in both cases. At both mounds, LOI weight loss duplicates with respect to
underlying sediments, showing some agreement with measured Leco Co. At Mound 1, peak
pH values of 6.7, higher than sediments above and below in the profile, are recorded.
26-0 cm: Fe values drop very sharply at both mounds. Sharp increases are recorded in EC
and pH accompanied by a drop in P, Ca. In Mound 1 Mn and MS decrease but in Mound 2 Mn
and MS rise. LOI weight loss duplicates with respect to underlying sediments, showing some
agreement with the magnitude of increase of Leco measured Co.
To summarise, both overburdens show broad similarities among themselves and marked
differences when compared to the land surface buried by each earthwork. The presence of
Chapter 5. The geoarchaeology of dark earths 131
pottery lines and variation in Al and Fe concentrations provide a sense that different ‘facies’
are recorded at both deposits. These permit delimitation of four sediment zones in which
different peaks in pH, P, Ca, Mn and other metals are observed. Their archaeological
interpretation is discussed below from the vantage point of ceramic and radiocarbon evidence.
5.1.1.4 Discussion
5.1.1.4.1 HA-5 (Urns’ unit)
The preceding analyses shows that even if specific vertical exposures of anthropogenic
dark earths appear to show a thick A horizon that has expanded downwards, the latter can be
argued to have developed as a result of net positive sedimentation, in effect raising the overall
elevation of surfaces at which pedogenetic processes took place (Woods 1995). Aside from
the pedo-stratigraphic characteristics discussed in Section 5.1.1.2, micromorphological
observations of profile HA-5 provide a number of additional and important insights about this
build-up. First, the presence of a more diverse range of charcoal size classes and, especially,
clear evidence for non-strongly melanised peds in AB horizon sediments together suggest that
in addition to sediments down-mixed from the overlying, strongly melanised, chemically-
enhanced and magnetically-enriched anthropogenic A horizon (Kämpf et al. 2003), the AB
horizon of the studied exposure records relict evidence of a significantly-enriched, now buried
and partially reworked Oxisol A horizon. Second, aside from ash-related dusty illuvial clay
coatings and common microscopic pottery fragments, rubified clayey aggregates, and bone
fragments, all of which are volumetrically important, it has already been mentioned that the
soil microstructure around 55-76 cm points to compaction and desiccation of sediments. These
characteristics could resonate with a specific ethnographic analogue: the interior of longhouses
with earthen floors.
As reviewed in Chapter 2, houses constitute important sediment traps at which what are
otherwise relatively lightweight particles, soot and ash, can easily concentrate – the former
especially on the underside of roof thatching. Earthen floors at longhouses are swept regularly,
which can induce size-sorting of small constituents, sometimes preceded by wetting, which
can induce compaction of sediments. It is thus not only possible that the density and size class
distribution of microscopic charcoal observed in thin section can be linked to accumulation
inside roof structures, but also that net sediment build-up takes place through a combination of
ash deposition (Zeidler 1983), faunally-induced burrowing, wriggling, mixing and/or churning
of soil material (Johnson et al. 2005b); the upwards or ‘conveyor’ translocation of sediments
from lower in the deposit (Vacher et al. 1998); and perhaps neoformation or re-precipitation of
dissolved kaolinite (Lucas et al. 1996) at a higher pH. The specific relevance of each of these
factors remains to be investigated.
Chapter 5. The geoarchaeology of dark earths 132
5.1.1.4.2 HA-1 and HA-3 (Mounds 1 and 2)
Analysis of profiles HA-1 and HA-3 has shown that broadly similar reconstructions are
possible at both earthworks despite the fact that they are located at a distance of around 200 m.
These similarities not only pertain to the ‘overburden’ of both mounds but also include the
land surfaces buried under each mound, pointing to broad stratigraphic contiguity at the level
of the landform (Heckenberger et al. 1999; Machado 2005; Rebellato 2007). Focusing on
Mound 1 (Figure 71, Figure 72), Machado (2005) argues that a Manacapuru occupation is
recorded underneath layer III in Mound 1 and suggests that a similar process may be in
evidence in Mound 2. Geoarchaeological evidence for a land surface at 136 cm below both
mounds provides strong support for this suggestion, pointing to occupations between the 5-6th
and the 7-8th century AD. The geoarchaeological study also supports Machado’s interpretation
that Layer III at Mound 1 represents the onset of dark earth formation, an inference that can be
extended to the lower portion of Layer IVa at Mound 2.
Machado also argues that Layers IV and V represented layer III-type soils remobilised
from the vicinity of the mound, and that Layer IV and V would have been remobilised by
Guarita phase peoples to construct Mound 1. The results of the geoarchaeological study
contradict this interpretation. Compared to layer III sediments, Layer IV and V show: a) much
higher Al, P, Ca, Mn and other metals than generally measured in Layer III soils; b) upwards
rising magnetic susceptibility values that accompany a reciprocal decrease in Fe
concentrations; c) much more abundant microscopic bone fragments that show a relatively
good agreement with P and Ca concentrations; d) much more abundant charcoal fragments
that show good agreement with high Co (Leco) values at Mound 1 and LOI weight loss values
at Mound 2 (which show a striking resemblance to those in Mound 1); e) abundant auto-
fluorescent phytoliths; e) Al concentrations that are different from buried land surfaces,
sediments from profile HA-5, and sediments from background profile HA-9. Some of these
contrasts extend to the overburden of Mound 2 (Profile HA-3, see Figure 70), which similarly
shows higher values compared to the characteristics of its own buried land surface and to
values measured in profiles HA-5 and HA-9.
One scenario that might be indicated by these data is that both mounds represent a ‘toss-
and-burn’ midden: refuse heaps located in the vicinity of residential structures, for instance,
would accumulate large amounts of food remains (bone, plant matter), ceramic artefacts and
charcoal. Burning would take place at these heaps such that magnetic susceptibility became
enhanced and charcoal concentrations increased. However, two points need to be considered
carefully. First, a large number of additional burials, some clearly in primary context, were
unearthed from Layer IV of Mound 1 during the 2006 excavations of this earthwork. It seems
counter-intuitive to think that people would bury their dead inside rubbish heaps. Second, if
Chapter 5. The geoarchaeology of dark earths 133
physical and chemical parameters represent decomposed midden material, how is that ever
increasing magnetic susceptibility values and carbon concentrations are achieved at both
mounds?
There is no easy answer to the latter question but it does pave the way to examine the
overburden at both mounds not simply as middens but as accreting deposit in which abundant
ash has been incorporated. The suggestion advanced here is that what we perceive today as
‘mound overburden’ records the combined effects of deliberate deposition of sediments (e.g.
pottery line in layer IVa in Mound 1), the accretion of house floors (e.g. sediments under
Layer IVa, lower half of layer IVb in Mound 1, sediments below 86 cm in Mound 2), the
collapse and/or deliberate burial of abandoned residential structures (e.g. sediments above 86
cm and below the topmost pottery concentration in Mound 2), and the reuse of sediments from
earthworks themselves to create raised platforms (e.g. sediments above 56 cm and 46 cm in
Mounds 1 and 2, including here pottery lines, see below). The material for this build-up
incorporates some soil and artefacts but also includes important volumes of ash produced in
situ in a manner similar to that discussed by Zeidler (1983). This reconstruction does not reject
that ‘midden’ material may be incorporated into the overburden of the earthworks but suggests
that analogous dynamics of concentration of microartefacts, bone, ash, soot and charcoal
particles inside houses and the decay of organic construction material, i.e. beams, roof
thatching impregnated with soot, etc. are the most important factors in the build-up of these
sediments. One can envision residential structures being built and lived in; house floors
building-up; burials being placed underneath house floors; structures being torn down,
abandoned, burnt, or closed down (perhaps as a result of the death of prominent individuals).
Machado’s next suggestion is that the mounds were built during the Guarita occupation of
the site. This suggestion rests on a) disregarding mid 1st millennium AD dates for what later
research shows is most likely an Açutuba to Manacapuru age burial urn; b) the fact that low
frequencies of Guarita phase pottery are recorded in the upper half of layer IVb, layer IVc and
layer V, always mixed with Paredão phase remains; c) the fact that so many charcoal
fragments from layer IV point to the age of the buried surface under the mound overburden
(Figure 71; Table 4); d) the fact that one charcoal fragment just below Layer IVc calibrates to
the 14-15th century AD while charcoal fragments dating to the 8-9th, 11-12th and 15-16th
century AD are found above Layer IVc. As discussed above, the fact that the chemical
signature of Layer IV is distinct from Layer III most likely overrules the suggestion that it is a
re-worked Layer II soil. However, the suggestion of reworking the sediments that make up the
mound after it is in place is one way to interpret patterning in the geoarchaeological data
(Figure 70) and apparent lack of patterning in the radiocarbon evidence.
Chapter 5. The geoarchaeology of dark earths 134
It was suggested that at Mound 1, at around 56 cm, that is at the middle of layer IVb, a
sharp discontinuity could be observed in Al, Fe, P, and Ca concentrations, as well as in pH,
Co, and LOI values. Above this discontinuity, both Co and LOI weight loss increase
dramatically. One interpretation for these trends is that the upper part of Layer IVb (above 56
cm) and pottery Line IVc are remobilised sediments from the lower part of Layer IVb and
pottery line IVa, in other words, that they have been overturned, leading to a higher
‘earthwork’. This implies that the Mound 1 may have been initially a more extensive
‘platform’ that was mounded at some point after build-up from the buried land surface to the
middle of Layer IVb took place. The sharp rise in carbon contents and magnetic susceptibility
would be understood as additions of charcoal and the decomposition of pottery into soils with
inherited concentrations as new near-surface burning and ash deposition – tracked by rising
Al, Mn, Ba, K, Mg, Cu, Sr and Zn – increases.
Whilst it is difficult to argue persuasively in favour of this interpretation some support is
provided by radiocarbon evidence. Or, it is fair to admit, it prompts a re-reading of the
radiocarbon evidence from this vantage point (Figure 73): an 8-9th century AD outlier located
above layer IVa can be interpreted as charcoal unearthed from underlying deposits as a result
of excavation activities associated with burials taking place once IVa and the lower part of
Layer IVb were in place; explain why two 11-12th century AD dates in pottery Layer IVc are
identical in age to three charcoal dates in pottery Layer IVa; and even explain a 1st millennium
BC outlier at a corrected 45 cm as charcoal unearthed from underlying deposits when these
sediments were at the same overall depth than the lower part of Layer IVb prior to
overturning. After the mound was built up by producing the upper part of IVb and IVc – either
during the final stages of the Paredão occupation or in Guarita phase time, excavation of
postholes/pits through Layers V and IV (arrows in Figure 71) during the 14th century AD date
(�-143587) could easily explain both the few Guarita charcoal fragments and shards found in
IVc and the Paredão phase shards and charcoal fragments from Layer IV found above Layer
IVc.
Chapter 5. The geoarchaeology of dark earths 135
5.1.1.4.3 New radiocarbon evidence for Mound 2
The overall gist of this reconstruction finds support in radiocarbon evidence produced in
the context of this study for Mound 2 of the Hatahara site. As discussed in Section 2.5, AMS
radiocarbon dates were run on concentrated microscopic charcoal fragments from three depth
intervals. The results are slightly counterintuitive (Figure 75): the uppermost sample, from 60-
65 cm below the surface, calibrates to 400-220 BC (WK-16222, 2269 + 42 BP), suggesting a
death event in the 4th to 2nd century BC, an old age range which is not without precedent in the
chronology of the project (Chapter 4) and which overlaps a layer II date at Mound 1. Taken at
face value, it suggests an inherited charcoal pool – arguably old wood from clearance in the
early part of the 1st millennium AD – in sediments employed as part of the mound overburden.
The two lowermost samples, respectively from 105-110 and 165-170 cm below the surface,
calibrate to age ranges of AD 890-990 and AD 770-890 (WK-16223, 1105 + 37 BP and WK-
16224, 1191 + 38 BP), slightly earlier than the bulk of the evidence for the Paredão
occupation at Mound 1, but clearly not pointing to a Guarita phase occupation.
Given the reconstruction of land surfaces discussed in the previous section, the
‘stratigraphic order’ of the lower two dates would have to be understood as a reflection of the
efficiency of down mixing of microscopic charcoal from the top of the buried land surface
located immediately below the mound ‘overburden’, whilst the older age of the topmost
sample would indicate a ‘stratigraphic reversal’ for sediments at Mound 2. At the risk of
weakening the overall credibility of the three dates, it needs to be stated that
micromorphological, physical and chemical characteristics of samples from 60-65 cm do not
in any way suggest the incorporation of sediments that were originally much lower in the
profile: the rare illuvial clay coatings at this depth are unlikely to reflect a B horizon and Al
concentrations appear more in line with those recorded in the uppermost part of the buried
land surface. Reported ceramic remains at this depth also do not appear to signal the
incorporation of an older component to the mound overburden. This discrepancy invites
critical examination of potential errors: a small chance exists that samples were reshuffled at
one or another step in the process between charcoal extraction and measurement of 14C (see
Section 2.5). This doesn’t make the age ranges invalid – as noted above they are on the whole
consistent with time ranges recorded in Mound 1 – but does question their stratigraphic
position. If the dates were in correct ‘stratigraphic order’ – admittedly a speculation – an older
age (WK-16222) lower in the profile would be congruent with the reconstruction of an old
land surface below around 150 cm; the AD 770-890 date at 105-110 cm (WK-16224)- the
land surface buried by the mound ‘overburden’ - would point to the initial moments of the
Paredão occupation of the site, and the youngest date of AD 890-990 (WK-16223) would
Chapter 5. The geoarchaeology of dark earths 136
indicate the moment at which mound build-up has advanced substantially. Either way, the
dates importantly demonstrate that both earthworks constitute part of a single arrangement of
mounds that can be associated with the Paredão phase occupation of the site, in turn
supporting that the Hatahara site records a Paredão phase ring village at which houses were
emplaced on platforms.
5.1.2 The Lago Grande site: settlement and hinterland soils
(Profiles LG-1, LG-2, LG3 and LG-4)
Archaeological understandings of the Lago Grande site have been presented in Chapter 4
(see Section 3.2.2.4 in Chapter 4) and the main macroscopic characteristics of the four studied
profiles have been briefly summarised in Section 2.2 of this chapter. The five sampling
exposures consist of profile LG-3, an excavation through mound 1 of the site; Profile LG-1,
the exposed terra firme-side of the trench that cuts through the ditch and promontories
complex; Profile LG-2, the exposed peninsula side of the same complex but sampling the
promontory, a buried horizon and underlying sediments; Profile LG-4, a cut through the terra
firme side of the site that shows a thick terra mulata A horizon; and Profile LG-5, a set of
three topsoil samples used as background. Figure 76 shows the location of the first four
exposures. In what follows the results of the analysis will be discussed in two parts. Attention
will first be focused on the soil mantle of the settlement-side of the site by examining data
from profile LG-3. Attention will then be shifted to examine the terra firme side of the site,
focusing more specifically on Profiles LG-1, LG-2, LG-4
5.1.2.1 Profile LG-3 (Mound 1, terras pretas)
As noted in Chapter 4 many of the terra preta expanses with Paredão phase pottery in the
central Amazon region are characterised by one or more circular arrangements of often meter-
tall earth mounds. At the Lago Grande archaeological site, excavations of Unit 1 samples one
such feature, Mound 1 of the peninsula side of the site (Figure 76). The darker coloured
sediments within Unit 1 occur below about 100 cm, an observation that has been interpreted as
evidence for an old land surface characterised by a terra preta A horizon that was buried by
construction or accumulation of the mound ‘overburden’ (Donatti 2003; Neves et al. 2004).
Radiocarbon evidence from this part of the deposit has been marshalled to suggest a scenario
for rapid formation of terra preta soils (Neves et al. 2003; Neves et al. 2004). The fact that
these sediments include a minority of Manacapuru phase together with a majority of Paredão
phase pottery has been considered as evidence for Manacapuru ‘tradeware’ at the site (Neves
et al. 2003; Donatti 2003; see chronological implication in Lima et al. 2006:46).
Sediment samples collected during excavations of Unit 1 (Profile LG-3, see Figure 78,
right) and analysed in the same fashion as those from Hatahara, provide support for some of
Chapter 5. The geoarchaeology of dark earths 137
the preceding inferences and a basis to offer a number of supplementary interpretations (Table
19; Figure 77). Layer II (170-180 cm) shows pH values higher than immediately overlying
sediments, low but important levels of enrichment in especially P and Ca, and levels of MS
comparable to near surface burning at HA-9, suggesting that the stratigraphic boundary
between it and the overlying Layer III identifies the burial of an old land surface characterised
by some soil enrichment but no clear soil melanisation. If broad stratigraphic contiguity exists
at the scale of the landform, it is likely that this record can be related to the Açutuba phase
occupation identified some 100 cm below the surface in Unit 3 (see Figure 76), which dates to
the beginning of the first millennium AD (see Section 3.2.2.4 in Chapter 4). These
characteristics support Lima’s et al.’s (2006) suggestion that Açutuba phase occupations did
not result in strongly melanised terra preta soils (cf. Myers 2004).
Layer III shows a peak in pH and a marked rise in MS values at around 130-140 cm,
suggesting the convenience of distinguishing two ‘facies’ within this part of the deposit. The
lower IIIa is characterised by constant Ba and Na, a decrease in Fe, and rising concentrations
of Mn, P and Ca. The higher IIIb is characterised by stable Fe concentrations but sharply
rising P, Ca, Mn, Ba, Cu, Na, Sr, Zn, K and Mg. Concentrations of these elements peak
towards the upper part of layer III (IIIb). Inflections in pH delimiting both facies suggest
acidification of sediments as a result of up-mixing from lower in the deposit. Contrasts
between IIIa and IIIb, which can be observed in profile drawings (Figure 78, right: note much
smaller shards in the lower part of Layer III), extend to the ceramic assemblage and
radiocarbon evidence. As regards pottery, the popularity of Manacapuru with respect to
Paredão phase rim fragments is much higher in the proposed Layer IIIa (10:31 fragments)
compared to IIIb (10:104 fragments, shard counts based on Donatti 2003:94). As regards
radiocarbon evidence (see Table 6, for radiocarbon evidence for Lago Grande site), a charcoal
fragment from Layer IIIa (�-143606) provides an age range of AD 670-780, which is
consistent with the chronology for the later part of the Manacapuru phase at the Osvaldo site
(Neves 2000; Lima et al. 2006; Chirinos 2007) and also congruent with the Manacapuru
occupation at the Hatahara site (Table 4). In contrast, three dates from the proposed Layer IIIb
(�-143603, 4 and 5 in Table 6) calibrate to the 9-10th century AD, consistent with Paredão
phase dates at Hatahara (Table 4) and Antônio Galo (Table 7). These observations suggest that
some in-mixed Manacapuru phase pottery represents a Paredão phase reworking of a prior
(Manacapuru phase) occupation (cf. Lima et al. 2006:46), i.e. highlights an occupational
hiatus that cannot be readily ascertained by comparison of radiocarbon dates (the oldest
Paredão Layer IIIb dates are barely statistically indistinguishable from the Manacapuru date in
Layer IIIa (X2-Test on �-143603 and 143606: df=1 T=3.8(5% 3.8), see Table 6), but which
resonates with the pedo-stratigraphic interpretations presented in the analysis at Hatahara.
Chapter 5. The geoarchaeology of dark earths 138
Patterns in MS data identify a relatively sharp inflection located at around 110 cm in the
deposit (Figure 77). This inflection is subtly echoed in other variables such as Co, Ct, LOI, pH
and EC, and underscores that very high values of P, Ca and especially Mn, Ba, K, Sr and Zn at
100-110 cm (top of Layer III) and 70-80 cm (top of Layer V), cannot be assumed in the
intervening sediments (Layer IV and lower part of layer V). In other words, physical and
chemical data support the suggestion that the upper part of Layer III constitutes a buried
anthropogenic dark earth A horizon with significant levels of enrichment as suggested by
Neves et al (2004). In addition, physical and chemical data, including here inflections in pH,
MS, LOI and EC values, provide some sense that a distinction between layers IV and V is
reflected in sediment composition, and highlight potential stratigraphic discontinuity
suggested by available radiocarbon evidence: three radiocarbon dates (�-143607, 2, and 1, see
Table 6 and Figure 78) from Layer V and the contact with overlying layer VI indicate that
these sediments begin to accumulate towards the 11-12th century AD. These dates can be
distinguished statistically from Layer IIIb dates (X2-Test on �-143605 and 143602: df=1
T=12.5(5% 3.8)) although not construed as evidence of site abandonment.28 The shift to high
EC, lower pH, relatively low Mn, and low LOI recorded in the upper part of the more brown-
coloured sediments of Layer V is noteworthy and will be discussed in more detail in the
following section.
Physical, chemical and micromorphological data (Table 19 and Table 20) for Layers VI
and VII show that sediments which constitute the mound ‘overburden’ are significantly
enriched by settlement-related activities. Thin sections from the upper part of Layer VI and
Layer VII show very abundant microscopic bone, pottery, rubified clay, and charcoal
embedded intrapedally in dark brown (layer VI, see Figure 55, middle, right) to opaque grey
(layer VII) texturally ‘clayey’ sediments, the latter contrast mapping onto macroscopic colour
differences. High MS values and concentrations of P, Ca, Mn and other elements which can be
associated with the deposition and/or decomposition of debris associated with pre-Columbian
settlement dynamics, with lower concentrations of P, Ca, Mn and other elements in Layer VII
with respect to Layer VI, on the one hand, and higher Al and Fe in Layer VI with respect to
layer VII, on the other, possibly indicating different sources for the sediments that make-up
the mound ‘overburden’. In this regard, similarities in chemical data and recorded colour
between Layer IIIb and VII, coupled with the fact that charcoal at 35 cm (�-143600, Table 6)
is older than that collected from underlying Layer V/VI sediments, suggest remobilisation of
anthropogenically-enriched soils from the immediate vicinity of the site. The uninterrupted
28 Dates from the upper part of layer III, Mound 1 (� -143603, 4 and 5) cannot be distinguished statistically from
dates from the upper 60 cm of Unit 4 (� -178922 and 5, see Table 3), especially if the most proximate are considered (X2-Test on � -178922 and � -143605: df=1 T=1.0(5% 3.8)). The dates from the upper part of Unit 4, recorded by excavators as dark terra preta soils with abundant Paredão remains (Donatti 2003) (Neves 2003), cannot be distinguished statistically from dates from Layer V and the lower part of Layer VI at Mound 1 (X2-Test on � -178925 and 143601, 2, or 7: df=1 T=1.0(5% 3.8)).
Chapter 5. The geoarchaeology of dark earths 139
increase in MS values in Layer VI up to approximately 30-40 cm, at the same time, strongly
resonates with the suggestion that build-up of the deposit up to this depth is characterised by
intensive in situ burning at progressively higher surfaces.
5.1.2.2 Profiles LG-1, LG2 and LG-4 (terras mulatas)
The study of four separate profiles located outside the core area of the Lago Grande site
offers a glimpse into differences between clayey Oxisols developed under forest vegetation,
thick brown terras mulatas on the terra firme side of the site, and the settlement-related terras
pretas discussed in the preceding section.
Profile LG-5 samples an Oxisol A horizon under forest vegetation located some 3 km
north of the Lago Grande archaeological site. A horizon samples show physical and chemical
data comparable to the Hatahara background (Profile HA-9) except as regards Fe and MS
values (Table 24). Higher Fe concentrations reflect the fact that the soil mantle of this sub-
region has formed much closer to laterite exposures (see also Donatti 2003; Moraes 2006,
Arroyo-Kalin, pers. obs. 2002-2006). Lower MS values, on the other hand, can be considered
as levels of magnetic enhancement in Oxisols which have not seen recent burning. These two
observations bear on some of the interpretations of anthropogenic soils offered below.
Profile LG-2 samples the buried organic horizon (Layer II), overlying B horizon sediments
(Layer I), and underlying redeposited B horizon sediments (Layers IA and III, the latter being
a new A horizon forming on redeposited Layer I sediments) of the peninsula-side promontory
at the isthmus portion of the Lago Grande site (Figure 79, left; Figure 76). Important contrasts
are observed in micromorphological, chemical and physical data between Layers I, II, IA and
III (Table 22, Table 26). From a micromorphological perspective, Layer IA and layer I
sediments are organized as continuous, massive vughy zones, varying from a limpid yellow
(PPL/OIL) clay with a striated b-fabric (Layer I) to a slightly organically-stained dark
yellowish brown clay with a marginally speckled b-fabric (layer IA). Layer II sediments, on
the other hand, are organised as matrix-supported clayey irregular peds resulting from the
coalescence of different-size aggregates, showing a strongly organically-stained dark
yellowish brown (PPL) and gray (OIL) fine mineral fraction, and expressing a marginally
speckled b-fabric (XPL). The latter sediments have low but significant frequencies of
microartefacts (1%), including small quantities of mostly coarse silt-sized bone, as well as a
very high density (max 12.5% FMF) of mostly fine-silt sized charcoal fragments (Table 22).
The contact between Layers II and I (thin section LG-2.4) appears as a sharp unconformity
describing a more or less irregular contour. Sectioned illuvial clay coatings on Layer I
sediments at this unconformity (Figure 58, bottom), coupled with an almost complete lack of
indications for down-mixing of Layer II sediments into the upper part of Layer I (thin section
Chapter 5. The geoarchaeology of dark earths 140
7), strongly suggest that the latter is not an in situ buried A horizon but instead a redeposited
organic- and charcoal-rich sediment placed on a truncated B horizon. This observation accords
well with the recording of a sharp boundary between Layers I and II by site excavators in
2001 (Figure 79) and is also congruent with descriptions of the profile at the time of
geoarchaeological sampling in 2002.
Data from physical and chemical analyses for Profile LG-2 (Table 26) show much higher
values in virtually all measured variables in Layer II compared to samples from the
background profile (LG-5, Table 24) but levels of enrichment/enhancement that are much
lower than peninsula-side terras pretas (LG-3, Table 19), including here a much smaller pool
of organic carbon. At the level of the profile (Table 26; Figure 80, middle), Layer II values
also depart significantly from under and overlying sediments (Layers I and IA). Differences
include much lower Al and Fe concentrations, higher P, Mn, K, Mg, Na, and MS, yet lower
LOI values, suggesting moderate anthropogenic enrichment/enhancement and/or inputs from
other sources. As regards MS measurements, it is noteworthy that Layer II shows values
between 145 and 165 si units, higher than the benchmark for near surface burning derived
from the HA-9 background profile at Hatahara (compare Table 11). As regards LOI, whilst it
is surprising to record an inflection towards lower values given the abundance of microscopic
charcoal and strong organic staining observed in thin section, it supports the interpretation of a
truncated layer I and a redeposited layer II, followed by burial with Layer I-like sediments.
Inflections in the values of other properties, including pH and EC, also underline sharp shifts
between Layers I, II and IA.
Profile LG-1 samples a soil profile whose A horizon is stratigraphically contiguous with
Layer II (the buried organic horizon) in LG-2 but which is located on the terra firme side of
the artificially-constructed ditch feature, immediately behind the promontory (Figure 76;
Figure 79, left). Macroscopically, the A horizon of LG-1 can be clearly subdivided into three
sub-horizons (A1, A2 and A3) followed by a thin AB horizon that is underlain by a B/A
horizon. Micromorphological observations reflect these contrasts as follows: A-horizon
sediments are similar in texture and optical features of the fine mineral fraction but show more
granular peds, increasingly more abundant illuvial clay features, and different overall
proportions of intrusive clayey aggregates in A2 and A3 sediments compared to A1. All A
horizon sediments show marginal to rare microartefacts and microscopic charcoal in small
size classes, with peak concentrations in A2 (Table 21). More common gravel-sized limpid
yellow clayey aggregates towards the bottom of A3 indicate ‘up-mixing’ (tree throws,
digging?) of B horizon sediments. B/A horizon sediments appear as a massive vughy limpid
brownish yellow clay with a striated b-fabric (XPL) within which are embedded isolated
charcoal fragments, as well as intrusive and faunally-reworked peds of A2 or A3-like material.
Most noteworthy is the presence of a clear unconformity of undisturbed B horizon material
Chapter 5. The geoarchaeology of dark earths 141
upon which well-mixed A horizon-like material embedding illuvial clay coatings, small
charcoal fragments, and very rare sponge spicules, is observed. This linear ‘lens’ is overlain
by seemingly non-faunally reworked B horizon material suggesting it has been buried.
Data from physical and chemical analyses for LG-1 (Table 25) show much higher values
in virtually all measured variables than the A horizon of the LG-5 background profile (Table
24). Particularly noteworthy (Figure 80, top) is a rise in MS from low levels at 46 cm to values
that are equivalent to near surface burning at the HA-9 background profile at around 36 cm.
Above this MS remains constant at around 138 si units between 16-26 cm before rising
towards the surface. pH values, significantly higher than measured in background soils, show
an inflection at 36 cm that is echoed by LOI and EC, together recalling the transition between
Layers I and II in Profile LG-2. These trends are accompanied by lower Al and Fe and a sharp
rise in Ca and Mn from at least 36 cm.
Profile LG-4 samples the west profile of Unit 5, a test pit on the terra firme portion of the
Lago Grande site (Figure 76; Figure 79, right). Macroscopically, the profile shows a dark
brown and deep reaching A horizon that is underlain by an AB and a B/A horizon sequence.
The A horizon can be subdivided into two sub-horizons (A1 and A2) that map onto layers IV
and III recognised by excavators. Micromorphological data (Table 23) reveal that the A
horizon is a porous matrix-supported ‘clay’ organised as massive, irregular, peds formed from
the coalescence of different size aggregates of faunal origin. The fine mineral fraction appears
as a strongly organically-stained, dark yellowish brown (PPL) and brown (OIL) clay with an
undifferentiated b-fabric (XPL). Peds include small quantities of microartefacts in densities
comparable to A2 and A3 horizon sediments at LG-1 (<1% of the fine fraction), including
marginal fine sand-sized or smaller pottery fragments, marginal to rare sponge spicules,
marginal to rare silt-sized burnt soil fragments, and marginal fragments of fine sand-sized
bone. Microscopic charcoal is very abundant (10.5% in LG-4.1 and 12.5% in LG-4.2, see
Figure 48) but more common in gravel to coarse sand size in A1 (layer IV, i.e. LG-4.1) and in
fine sand to silt size in A2 (layer III, LG-4.2), in effect peaking in density in the A2 horizon.
The lower 1 cm of thin section LG-4.2 appears as a zone of lightly organically stained yellow
clayey (PPL/OIL) with a marginally speckled b-fabric (XPL) well above the AB or B horizon,
an observation that resonates with gravel-sized limpid yellow clayey aggregates in the A3 of
Profile LG-1. Within this secondary fabric, charcoal in the same size classes as LG-4.2 is
present (3.5% FMF).
Data from physical and chemical analyses for the LG-4 profile (Table 27) reveal that A
horizon sediments show much higher values in virtually all measured variables compared to
the LG-5 background soil (Table 24). Most noteworthy is the fact that, like LG-1, a sharp rise
in MS above the near surface burning benchmark (HA-9) is recorded as deep as 56 cm, in
Chapter 5. The geoarchaeology of dark earths 142
parallel with a consistent trend towards higher pH (Figure 80, bottom). An inflection in EC
values at this depth suggests discontinuity in profile build-up from 46 cm. Like LG-1, Al and
Fe values are much lower towards the surface. Mn, K, Mg, and Na are higher at the surface
but P, Ba, Cu, Sr and Zn are higher at 36 cm, co-patterning with high MS values,
microartefacts and silt-sized charcoal.
5.1.2.3 Discussion
It is clear that – much like Profiles HA-5, HA-1 and HA-3 – settlement-related terra preta
soils from the peninsula-side of the Lago Grande site i) record net positive sedimentation, and
ii) show evidence of buried land surfaces. Layer IIIa of Unit 1 may record an occupation that
results in some modification of the soil mantle that is subsequently reworked during a more
intense occupation that builds-up Layer IIIb, triggering the development of strong
melanisation and much more significant soil enrichment/enhancement. Both occupations are
preceded by the imprint of less intense inhabitation events starting in the first half of the 1st
millennium AD. The mound ‘overburden’ records evidence of deliberate events of sediment
deposition as well as possible profile build-up as a consequence of habitation. Clearly further
research and comparative examination of earth mounds from other sites (Machado 2005;
Moraes 2006) is needed to elucidate the matter more fully. However, it is interesting to note
that the stratigraphic position of Layers IV and V suggests that the topsoil at the Lago Grande
peninsula was not a uniformly dark earth about 1000 years ago because dark terra preta soils
(Layer III) were buried by deposition of brown coloured sediments (Layer V) before the
construction or build-up of the earthworks we presently recognise as mounds.
Analysis of the soil mantle beyond the peninsula side of the site offers some intriguing
clues about the processes responsible for these characteristics of the soil mantle. The analysis
of profile LG-2 shows that the main characteristics of the buried organic horizon (Layer II) at
the ditch-and-promontory complex differ markedly from settlement-related dark earths.
Micromorphological evidence shows that the transition from Layer II to Layer I is not
equivalent to an in situ A+B sequence but instead resembles a redeposited, organic-rich
sediment placed on a deliberately truncated surface (Figure 58, bottom). Similarities between
Layer II sediments from LG-2 and A2-A3 sediments from LG-1, including here overall
concentrations of Al and Fe, small but significant quantities of microartefacts, dense silt-sized
charcoal peaking with microartefacts, indications of a similar truncation in the deposit, and
slightly lower pH underlined by inflections in EC and LOI values (at about the same elevation
as the contact between Layers II and I in LG-2), extend the inference of a redeposited
sediment to the terra firme side of the gully immediately behind the promontories. Similarities
between Layer II and the A horizon of LG-4, including here markedly different Al and Fe
concentrations, a high density of silt-sized charcoal, marginal quantities of microartefacts, and
Chapter 5. The geoarchaeology of dark earths 143
an inflection in LOI values, extend this interpretation to the deep-reaching A horizon of LG-4.
In the latter, rising trends in MS values from 56 cm and upwards suggest that the thick A
horizon at this part of the site is an accreting deposit that has been enriched by incorporation
of sediments which produce physical and chemical signatures analogous to those observed in
LG-2 and LG-1.
An economical explanation for these observations is that some form of compost or mulch
constituted by large amounts of microscopic charcoal, abundant organic matter, and marginal
quantities of settlement debris has been redistributed over the surface of at least the terra firme
portion of the Lago Grande site prior to consistent near surface burning as the soil mantle
builds up from 46 cm (LG-1) and 56 cm (LG-4). This interpretation not only resonates with
previous suggestions that terras mulatas reflect semi-intensive or even intensive pre-
Columbian cultivation practices (Sombroek 1966; Andrade 1988; Denevan 1992b) but is also
in line with suggestions that organic amendments and consistent in-field burning characterised
past land use of these soils (Hecht and Posey 1989; Hecht 2003; Denevan 2004). The fact that
these sediments show inflections towards lower LOI values, an evident paradox given high
quantities of microscopic charcoal in thin section, suggests that the recipe for these
amendments may include sediments with a lower inherited pool of mineral carbon, for
instance clayey material from the nearby, seasonally drying lake bed.
Chronological data for these modifications are sparse but significant. Whilst a radiocarbon
date on charcoal from LG-4 returned a ‘modern’ age (�-178926, Table 6), the scant ceramic
remains at the exposure include an adorno fragment of a Paredão burial urn (Donatti 2003),
minimally suggesting that inhabitants related to this or later occupations were responsible for
the practices of soil management reconstructed on the terra firme portion of Lago Grande. The
suggested timing is confirmed by the calibrated age of a charcoal fragment from the buried
horizon (Layer II) in LG-2, which points to a death event around AD 890-1020 (�-178927,
Table 6). This age range is not only congruent with the Paredão occupation of the peninsula
side of the site but, interestingly, closes the chronological gap left by radiocarbon dates from
Layer IIIb and Layer V/VI at Mound 1 on the peninsula side of the mound. This provides a
tentative basis to suggest that shifts in LOI, MS, pH and EC values in Layer V at Mound 1
may be related to deposition of the same type of material on the substantially-enriched terras
pretas that make up the core of the site. Since, as discussed previously, co-eval radiocarbon
dates from strongly melanised terras pretas from the immediate vicinity (Unit 4) weaken any
suggestion that site abandonment has taken place in this time range, if Layer V represents
deposition of organic amendments as submitted herein, it can be construed as evidence for an
occupational episode characterised by the implantation of a house garden (Lathrap 1977;
Oliver 2001; Hecht 2003) on the peninsula side of the site.
Chapter 5. The geoarchaeology of dark earths 144
5.1.3 The Osvaldo site: settlement soils (Profile OS-1)
In Chapter 4, the Osvaldo site (Figure 81, top) was described as the best example of a
terra preta expanse in which mostly Manacapuru phase remains have been unearthed. Spatial
patterns in the density of ceramic remains at the site have been interpreted as evidence for a
ring village, albeit lacking in the mounds that characterise Paredão phase occupations in the
region (Neves 2000; Petersen et al. 2001; Heckenberger et al. 2001). Recent re-examination of
the ceramic assemblage has identified small but consistent quantities of Paredão phase
‘tradeware’ in-mixed with a majority Manacapuru assemblage (Chirinos 2007), an
interpretation that I have questioned on the basis of early Paredão phase data from the nearby
Antônio Galo site (Chapter 4, Moraes 2006). Although these points cannot be addressed
directly from the geoarchaeological analysis, inclusion of this site in the dataset minimally
enables me to supplement previous remarks about composition with pedo-stratigraphic
inferences.
As noted in Section 4 of this chapter, profile OS-1 shows very high Co, high MS, P, Ca,
Mn, Ba, Cu, K, Mg, Na, Sr, Zn, and intermediate pH values, especially above 66 cm or so.
The overall magnitude of enrichment is comparable to some of the previously examined
clayey dark earth sites, an observation that corroborates that strong enrichment of these soils
shows no clear relation to the presence of whitewater river alluvial floodplains. However,
some differences are also noteworthy: maximal Leco furnace values at OS-1 indicate that 5.17
of 5.4% total carbon is constituted by organic carbon, effectively the highest levels recorded in
the dataset of the study. These values are observed between 46 and 66 cm (Layer IIIa), above
which (Layer IIIb) show slightly lower Co values, 4.94 of 6.14% total carbon. Below 46-66
cm, lower but significantly high Co values, 1.67 of 2.04% total carbon, are recorded at about
86 cm (Layer II). It is worth pointing out that despite a markedly higher total carbon pool in
Layer IIIb with respect to Layer II, the contribution of organic carbon in both strata is in broad
terms comparable (81.86% in Layer II vis-à-vis 80.50% in Layer IIIb), and in both cases is
much lower than in Layer IIIa (95.7%). The latter is more similar to that measured in the
overburden of the Mound 1 at Lago Grande (LG-3), and analogous to values recorded at the
buried Paredão land surface under Mound 1 at Hatahara (HA-1).
In contrast to the depth-wise trend in Leco data, LOI weight loss values (Figure 83) show
a net increase from 96 to 56 cm (Layers II and IIIa), followed by a sharp rise towards higher
values between 46 and 26 cm (Layer IIIb). Whilst the disagreement between Leco and LOI
data once again highlights the fact that the latter technique does not measure well total carbon
in these Fe-rich soils, the higher weight loss that LOI records in Layer IIIb is worthy of note
because it suggests that these sediments incorporate a higher proportion of constituents that
are volatile at 550 C, in turn highlighting the need to stave off layer IIIa from layer IIIb.
Chapter 5. The geoarchaeology of dark earths 145
Depth-wise trends in pH values accompany the peak in Co and LOI weight loss, rising from
5.3 at 96 cm to 5.8 at 66 cm (Layer II- lower part of Layer IIIA), decreasing slightly to 5.7 at
56 cm (top part of Layer IIIa), and showing a sharp decrease to 5.4 between 46 to 26 cm (layer
IIIb). Similarly, Al concentrations rise steadily from the bottom to the top of the profile,
reaching peak values at 46 cm (limit between IIIa and IIIb) and thereafter decreasing in IIIb.
Similarly, MS values rise from levels analogous to profile LG-5 (no near surface burning) at
96 cm to levels signalling near surface burning at 86 cm (bottom of Layer II); they then rise
more or less consistently until an inflection at 56 cm (limit between Layer IIIa and IIIb);
above this, they continue to rise consistently to levels comparable to Mounds 1 and 2 at
Hatahara and Layer IIIb at Mound 1 of the Lago Grande site. P, Ca, Sr and Zn concentrations
are high in Layer II compared to background profiles, reach peak values at 46 cm (just above
the limit between Layers IIIa and IIIb), and decrease (P and Ca sharply, others slightly)
towards 26 cm (layer IIIb)29. Mn, Ba, K, and Na, in contrast, all show a rising trend with
decreasing depth. EC values decrease consistently from the bottom to the top of the profile,
with measurements above 56 cm signalling different conductivity in Layer IIIb.
On the whole, the upwards rising trends of parameters at OS-1 are familiar when
examined from the vantage point of the analyses at Hatahara and Lago Grande. Both
excavators’ descriptions and physical and chemical data for Layer I suggest an AB horizon
just underlying a buried land surface in the lower part of layer II. Above this,
geoarchaeological data can be construed to suggest that net profile accretion with intense near
ground burning took place at the locale up to the limit between Layers IIIa and IIIb. The lower
EC and pH values at or immediately above this contact hint at a slight discontinuity. This can
be interpreted in number of ways: i) it could represent an exposed surface which has been
subsequently buried by conveyor up-mixing and perhaps acidified slightly due to the regrowth
of vegetation; ii) it could record plough damage beyond the topsoil (Layer IV, 0-20 cm); iii) it
could concentrate different inputs and/or include sediments originating from elsewhere on site.
Of these three alternatives, (ii) is the easiest to discard: the fragmentation of the ceramic
assemblage (total shard weight divided by number of fragments) is very similar in layers IIIa
and IIIb (Chirinos 2007: Annex 6, Table 3.2); none of the clayey dark earths examined so far
in the study, moreover, shows a consistent trend towards lower pH that spans 50 or so cm
towards the surface; in addition, markedly similar MS values at 36-46 cm are difficult to
reconcile with a scenario in which sediments have been reworked by ploughing.
This leaves (i) and (iii). Photos from excavations (Figure 81) support alternative (iii):
sediments in the upper part of the profile are of a much darker colour and appear to be
deposited above an extended concave unconformity. A darker colour is consistent with higher
29 A lack of micromorphological evidence for this site is unfortunate because it prevents answering some questions
developed in the study, for instance, the degree of bone preservation in a low pH context.
Chapter 5. The geoarchaeology of dark earths 146
recorded concentrations of Co and, interestingly, different Mn concentrations between IIIa and
IIIb: expressed as a proportion of Al concentrations (in order to reflect impregnation of the
clayey mineral fraction), Mn:Al in Layer IIIa is comparable to the Manacapuru age surface at
Hatahara; Mn:Al in layer IIIb is similar to that recorded in the A2 horizon at HA-5, sediments
at 86 cm in Mound 2 (Profile HA-3) and the strongly melanised 136 cm land surface under
Mound 1 (Profile HA-1), all of which are dominated by Paredão remains. As regards the
concave unconformity, excavations by the Central Amazon Project in 2005 evidenced very
similar features associated with later moments of the Paredão phase occupations at the Lago
do Limão site. The latter ones were clearly features infilled with sediments of different texture
(Arroyo-Kalin, pers. notes, 2005, Moraes 2006:07, Figura 101).
5.1.3.1 Discussion (OS-1)
The preceding analysis cautions against regarding the OS-1 profile as an example of
single-event build-up associated with an intense and short lived occupation. A lack of
stratigraphic consistency in dated charcoal fragments (Neves et al. 2003) only invalidates their
use in a direct age model for the whole profile but does not diminish their chronological
significance. This statement implies first that death events dated from the last centuries of the
1st millennium BC to the mid 1st millennium AD should not be disregarded : even if these
events are considered not to be associated with human activities – a suggestion that seems
implausible given i) the increasing ubiquity of Açutuba phase remains in the research area
(Lima et al. 2006) and ii) the validation of abutting chronologies for the Açutuba and
Manacapuru phases (Chapter 4) – the maximal separation between death events after the 3rd to
4th centuries AD barely surpasses the 200 or so years required for rainforest vegetation to
reach climax conditions (see Saldarriaga et al. 1988), i.e. if anything they record forest fires
and a disturbance regime.
Geoarchaeological data show that Layer II sediments record not insignificant levels of
enrichment with Co, P, Ca, Mn and other metals, as well as MS values that suggest ‘near
surface’ burning and an initial rise in the pH of the soil. Al concentrations already appear to be
higher than sediments immediately below. A radiocarbon date from layer II calibrates to 90
BC – AD 130 (�-143621), supporting the inference of an as yet unreported Açutuba phase
occupation. Geoarchaeological data also suggest that the upper part of Layer II – where
pottery is more concentrated (Neves 2000; Chirinos 2007) - and Layer IIIa represent one or
more occupation events that record net profile build-up. This build-up appears to extend up to
66-56 cm, where lower EC, peak pH values, and an inflection in MS measurements indicate a
discontinuity. Five dates on charcoal between 76 and 50 cm (�-143616 to 20), all of which are
statistically indistinguishable when calibrated, suggest that the build-up of Layer IIIa takes
place in the 7th-8th century AD. A further date from 54 cm (�-143615), which points to a 6-7th
Chapter 5. The geoarchaeology of dark earths 147
century AD timing, has been regarded as roughly contemporaneous given overlapping
standard deviations (Neves et al. 2004:128ff) but, as suggested below, probably points to an
older occupation.
Geoarchaeological data suggest that Layer IIIb is most likely redeposited and most likely
incorporates different inputs. This reading supports a re-examination of available radiocarbon
evidence: four dates (�-143609, 10, 12 and 13) from this layer point to death events in the 7-
8th century AD, showing that these sediments have received charcoal inputs contemporaneous
to those lodged in Layer IIIa. Three other dates (�-143608, 11 and 22), which have either been
rejected due their aberrant stratigraphic position or too large standard deviation († in Table 3),
or considered to represent older occupations or disturbance (§ in Table 3), can be understood
in much the same way as the older dates in Layers II and IIIa: the oldest (2120±40, �-143622,
Table 3) points to either an undetected Açutuba phase occupation and/or old wood burned
during the initial clearance of the locale after this timing; the next oldest (1730±90 BP, �-
143611, Table 3), with its fairly large standard deviation, is statistically indistinguishable from
another charcoal fragment from Unit S845 E1921 (1740±30 BP, �-143624, Table 3), which
calibrates to AD 240-340. The last outlier (1550±40 BP, �-143608, Table 3), rejected by
Neves et al.(2004), is consistent with directly dated Manacapuru shards from the eponymous
site (Hilbert 1968) and from Lago do Limão site (Table 7) and cannot be distinguished
statistically from the 6-7th century AD (�-143615, Table 3) age in layer IIIa.
To summarise, whilst numerous dates pointing to the 7th to 8th centuries AD show very
high levels of charcoal production at this time, and although it cannot be doubted that this
chronological evidence points to Manacapuru phase inhabitants (Petersen et al. 2004; Lima et
al. 2006; Chirinos 2007), soil modification and the age of charcoal fragments suggest a
trajectory of soil enrichment and vegetation disturbance that conservatively begins in the 3rd to
4th centuries AD, i.e. a moment at which the Açutuba and Manacapuru ceramic phases
chronologically overlap (Chapter 4), in turn contradicting a model of dark earth formation
characterised by brief and intense occupations (Neves et al. 2003). Evidently the nature of the
processes leading to deposition of Layer IIIb over Layer IIIa is difficult to reconstruct only on
the basis of geoarchaeological data. However, it is noteworthy that of 19 radiocarbon dates
available for the Osvaldo site as a whole, only one (�-143626) provides an age range beyond
the 8th century AD, pointing to a death event in the 9-10th century AD. As noted in Chapter 4,
this date comes from Unit S845 E2046, where the ratio between Manacapuru and Paredão
phase rim shards is 23:18 (Chirinos 2007:102, Gráfico 4.1), i.e. clearly departs from the 8:2
ratio that constitutes the main trend in other units of the site. Examined from the vantage point
of the geoarchaeological analysis, and recalling the pedo-stratigraphic interpretation of the
LG-3 profile, rather than Paredão ‘tradeware’ and/or a transitional Manacapuru-Paredão
occupation, an immediately posterior, arguably-colonising Paredão phase occupation might
Chapter 5. The geoarchaeology of dark earths 148
explain why soils of Layer IIIb show Mn concentrations that are similar to those recorded in
soils with Paredão occupations in the region.
5.1.4 The Açutuba site: settlement and hinterland soils (Profiles
AC-1, AC-2, AC-2)
In Chapter 4, the Açutuba site was described as a 3 km long and 400 m wide expanse of
sandy terras pretas located on a bluff overlooking the Negro river (Figure 84). It was
highlighted that its position along a drainage that seasonally exposes its sandy bed suggested
wind blown sand contributed to overall sedimentary build-up It was mentioned that a
substantially enriched and thick terra preta horizon with abundant archaeological remains was
more evident at the riverfront yet a gradual shift towards lighter coloured terra mulata-like
soils, generally accompanied by a decrease in the density of ceramic remains, was recorded
towards the ‘back’ of the site. It was also highlighted that the site, which is subdivided into
three sectors (I, II and III), is considered the outcome of a long and spatially-diverse process
of human occupation that begins with possible preceramic occupations during the mid
Holocene, records a long gap until around 1000 BC, and is followed in sequential order by
evidence for ceramists of the zone hachured tradition and Açutuba, Manacapuru, Paredão and
Guarita phases until European contact time. Among these complexes, only Manacapuru,
Paredão and Guarita phase occupations are associated with dark earth deposits. It was
emphasised that broad stratigraphic contiguity at the scale of each site sector was suggested by
multi- and single-component occupations that included, among others, superimposed Açutuba
and Paredão assemblages at the front of sector IA, overlapping Manacapuru, Paredão and
Guarita assemblages at the front of sector II, and a single-component, buried Açutuba phase
assemblage at the back of sector IIA (Heckenberger et al. 1999; Petersen et al. 2001; Neves et
al. 2003; Neves 2005; Lima 2005; Lima et al. 2006).
5.1.4.1 Profile AC-2 (background profile)
The modal characteristics of ‘background’ sandy Oxisols at Açutuba have been examined
by sampling an exposure located 250 m inland from the edge of the Açutuba I-A bluff. This
locale shows grey-brown sandy soils covered by successional vegetation that suggests recent
clearance and/or slash and burn agriculture. As with the case of the HA-9 profile, the main
purpose of studying the AC-2 profile was to gain insights into modal pedogenetic conditions
operating in the sandy soils.
As will be discussed in further detail in Section 5.1.6 and in sharp contrast to the
background HA-9 profile, the microscopic organisation of sediments from the Ap and A2
horizon at AC-2 can be characterised as grain-supported (enaulic) texturally ‘sandy clay’
sediments. Microscopically they appear as grano-oriented clayey braces (<50µm width) with
Chapter 5. The geoarchaeology of dark earths 149
common intergrain rounded pellets (<50 µm diameter) and rare small porphyric clayey peds
(<150 µm), especially in the A2. Towards the AB and especially in the upper part of the Bt,
sediments are at first glance texturally similar but evidently grade towards a matrix-supported
organisation in which slightly larger clayey peds (<150 µm diameters) are more common,
grano-oriented clayey braces are less prevalent (especially in the upper part of the Bt), and
slightly vughy massive clay zones locally reworked into a granular fabric made of <150 µm
rounded to subangular faecal pellets are more frequent. The optical properties of the fine
mineral fraction vary from a light to medium organically-stained, yellowish brown clay
(PPL/OIL) with an undifferentiated b-fabric (XPL) in the Ap to a more strongly organically-
stained, dark brown clay (PPL/OIL) with a marginally speckled b-fabric (XPL) in the A2, to a
lightly organically-stained, light yellowish brown clay (PPL/OIL) with a speckled b-fabric
(XPL) in the AB, to a limpid to lightly-stained yellow clay with organic punctuations
(PPL/OIL) with a speckled to striated b-fabric (XPL) in the Bt horizon. Other
micromorphological characteristics are summarised in Table 29. Noteworthy are the presence
of relatively abundant microscopic charcoal fragments, very rare to marginal burnt soil
aggregates, and relatively abundant microscopic charcoal fragments in the Ap and A2
horizons. No microartefacts or fragments thereof (e.g. sponge spicules) are observed.
As will be discussed below, the grain-supported microstructure of these soils highlights
that loci for the preservation of chemically-enriched clay and particulate constituents are much
rarer – volumetrically lower – in sandy soils compared to clayey soils. Physical and chemical
data support this very clearly: Al concentrations in the Bt horizon are about 50% of those
observed in the HA-9 profile whilst Fe values do not exceed 8000 ppm, much lower than
clayey soils. Al, a constituent of kaolinite, increases with depth tracking a more clayey B
horizon, especially below 56 cm. Fe concentrations increase slightly from the bottom of the
profile towards the A2 horizon but are markedly lower in the Ap. LOI data – theoretically
more trustworthy with sandy soils (Houba et al. 1995) – suggest a marked increase in total
carbon between 46 and 36 cm. MS data, which show very low readings compared to clayey
soils (a partial reflection of low Fe concentrations), rise gradually to a notorious sub-surface
peak at 26 cm. The latter is overlain, at 16 cm, by an inflection and, above this, by a further
rise towards the surface. pH values are surprisingly high, rising from 5.8 at 76 cm to a peak of
6.4 at 26 cm, above which a decrease towards the surface is recorded.
Low EC values are also observed above 46 cm, highlighting a more porous soil medium in
the A horizon as a whole. Aside from P, which rises from very low values of 60 ppm in the Bt
to 90 ppm in the Ap, measurements of all other elements considered in the study (Ca, Ba, Cu,
K, Mg, Mn, Sr, Zn) are near or below ICP-AES detection limits. Peaks in MS, LOI and pH
values in the A2 horizon and markedly different Al and Fe concentrations in the Ap suggest
the latter horizon may constitute sheet-washed sediments from the immediate vicinity of the
Chapter 5. The geoarchaeology of dark earths 150
sampling locale, whilst the A2 is best interpreted as a now buried land surface characterised
by a sandy topsoil in which evidence for near surface burning is recorded. Subtle textural
variation in the size classes of quartz grains points to a lack of phytostabilisation that can be
associated with past land use, in turn creating conditions for the remobilisation of the topsoil
by water and wind.
5.1.4.2 Profile AC-1 (riverfront, Sector IA, terras pretas)
Compared to both terra preta profiles from Hatahara and profile AC-2 at the site, samples
from profile AC-1 show a number of important contrasts (Table 32). First, most obvious is the
fact that A horizon sediments are very porous, texturally ‘sandy clay’ sediments organised as
grano-oriented clayey braces (<50µm), incipient porphyric clayey peds (<150 µm) and
common intergrain rounded pellets (<50 µm), whereas the B/A and Bt horizons are texturally
‘clay’ matrix-supported sediments analogous to B horizon material observed at the Hatahara
site, i.e. organised as continuous, slightly vughy massive zones which are locally and
marginally reworked into a granular fabric formed by <150 µm rounded to subangular faecal
pellets. Second, variation is observed in the optical characteristics of the fine mineral fraction,
which shifts from an organically-stained, yellowish brown (PPL) and brown (OIL) with a
mostly undifferentiated b-fabric (XPL) in the Ap horizon to a strongly organically-stained,
dark yellowish brown (PPL) and dark grey (OIL) clay with an undifferentiated to marginally
speckled b-fabric (XPL) in the A2 horizon. A-like sediments of the AB horizon material
appear as strongly organically-stained, dark yellowish brown clay (PPL) with a marginally
speckled b-fabric and brown colour under incident light (OIL), whilst B-like material is a
lightly organically-stained yellow clay (PPL) with a speckled b-fabric (XPL) that in many
ways resembles AB horizon samples from profiles HA-9 and HA-5. In the Bt horizon, the
dominant fine mineral fraction appears as a limpid yellow clay (PPL) with a speckled b-fabric
(XPL). Channels/chambers are marginally present throughout, and very rare intrusive
aggregates (showing different optical properties in the fine mineral fraction) suggest minimal
up- and down-mixing by soil fauna. Noteworthy is the presence of marginal illuvial clays in A
and AB horizon. These are also observed in B/A and especially Bt horizon sediments as might
be expected.
Microartefacts of the same types as observed in the Hatahara and Lago Grande dark earths
are present in very low quantities and generally concentrated in A2 horizon sediments and the
A-like fabric in the AB horizon, with marginal occurrences of sponge spicules observed in B-
like fabric of the AB horizon and in the B/A horizon. Microscopic bone is extremely rare, in
virtually all cases being embedded in clayey material. Microscopic charcoal, on the other
hand, is extremely abundant in the fine mineral fraction of A2 (Figure 55, bottom right), and
common in the Ap A-like material of the AB horizon. It varies from marginal to isolated in the
Chapter 5. The geoarchaeology of dark earths 151
B-like material in AB, B/A and Bt horizon sediments. In general, organically-stained intrusive
aggregates embed fine sand-sized or smaller charcoal fragments and very rare
microartefacts.(Table 31)
Some of the micromorphological observations can be related to depth-wise trends in
physical and chemical data for AC-1 (Figure 88). Al and Fe concentrations in the B/A and Bt
horizon are on the whole very similar to those measured in the background profile HA-9 at the
Hatahara site. However, above 86 cm, approximately the limit between the AB and B/A
horizon, Al concentrations decrease sharply, to about 50% of values measured in the B
horizon. Above this a stepped pattern of decrease and increase is recorded towards the surface,
reaching concentrations slightly lower than the Bt horizon at 26 cm before dropping again at
16 cm. These measurements show a good agreement with the generally more reduced surface
area of the fine mineral fraction observed in thin sections from the AB, Ap and A2 horizons,
although some disagreement is observed between estimates of the fine mineral fraction in thin
Section 2, suggesting the upper part of this horizon is slightly more clayey than implied by
ICP-AES data. Fe concentrations in the AB and A horizon follow the general trend observed
in Al values, appearing slightly more important in the AB horizon, showing low values in the
A2 horizon, and increasing slightly towards the transition between the A2 and Ap horizons.
pH values show a reduction in acidity comparable to other anthropogenic dark earths and
are clearly much higher that the background HA-9, LG-5, AC-2 profiles. A high pH of 6.0 at
166 cm is overlain by a value of 5.7 at 116 cm, the B/A horizon. Above this, a sharp increase
is recorded towards the surface with a clear peak of 6.5 at 56-66 cm and markedly higher
values at 16 cm and above. The fact that an intervening zone with low pH overlies the high pH
at 166 cm makes it unlikely that this is the result of faunal down-mixing or of illuviation (see
below). EC values are relatively higher in B and B/A horizon sediments and become more
reduced in the grain-supported AB and A horizon material, with a particularly noteworthy
inflection at around 56 cm, the boundary between the A2 and A3 horizons. Leco furnace data
show B horizon sediments are composed of 0.34% Co, representing 56.7% of total carbon. In
the AB horizon at 76 cm, Co is 1.08% of 1.13, representing over 95% of total carbon. In the
A2 horizon, Co values are 1.83-1.84% representing between 80 and 73% of total carbon. MS
data show values comparable to the LG-5 background profile at 116 cm, the contact between
the B/A and Bt horizon, a rise to values in rough terms comparable to the near surface burning
signature (HA-9) between 76-86 cm, and a rise to clear evidence of near surface burning at 66
cm. However, in the depth interval immediately above, MS decreases progressively, reaching
lower values of 144.4 si units at 36 cm. Above this, a sharp rise is recorded at 26 cm, followed
by a similar magnitude decrease towards the 16-6 cm depth interval. It needs to be pointed out
that a relatively linear relation between MS and Fe concentrations in the A and AB horizon
can be observed.
Chapter 5. The geoarchaeology of dark earths 152
Compared to the texturally clayey dark earths examined at Hatahara, Lago Grande and
Osvaldo, soils at AC-1 show much lower concentrations of P, Ca, Mn, Cu, Mg, Sr, Zn, Ba, K
and Na, with measurements of the latter two (K, Na) being very close to detection limits.
Patterns of variation by depth evidence slight enrichment with P, Ca, Mn, Ba, Cu, Sr and Zn at
96 cm (the boundary between the AB and B/A horizons). P and Sr concentrations decrease
sharply and Ca and Zn concentrations drop slightly at 76 cm (the top of the AB horizon) but
Mn, Ba, Cu, K, and Mg rise. At 56 cm, where high pH, Fe, low EC and a trend towards lower
MS values are recorded (the boundary between the A3 and A2 horizons), P, Ca, Mn, Ba, Cu,
Sr and Zn all rise to relatively high values, before decreasing towards 36 cm, approximately
the middle of the A2 horizon. Above this, at 26 cm, they all rise, P, Sr and Zn more sharply
than Ca, Mn and Ba. Towards the surface, P, Ba, Cu and Zn concentrations decrease towards
values similar to those which could be interpolated immediately below 56 cm depth, whilst
Ca, Mg, and Sr rise sharply, most likely reflecting sub-recent inputs into the soil.
A number of micromorphological observations (Table 32) help to bring into sharper focus
some of these depth-wise trends. A starting point is to focus on the A/B like admixture
observed in AB horizon sediments (thin section 3). From about 80 cm downwards,
micromorphological observations evidence the presence of rare but significant subangular
blocks whose b-fabric is striated, pointing to relatively in situ sediments. As far as it can be
ascertained from ICP-AES data, it is from about this depth and above that a strong decrease in
Al and Fe concentrations is observed in the profile. As noted previously, however, at a depth
most likely intermediate between 96 and 76 cm, a shift in MS identifies a degree of magnetic
enhancement analogous to that observed in HA-9. Taking this depth as a potential anchor, and
employing values corrected to Al and Fe concentrations to ‘smooth’ the variability observed
in the profile, one observes remarkably similar trends with increasing depth in Ca:Al, Mn:Al
and MS:Fe, a fall-off patterns in P:Al, a drop in pH values from 6.4-6.3 (at 86-96 cm) to 5.7
(at 116 cm), and an overall increase in EC values signalling less porous sediments towards the
lower part of the profile. One interpretation for these trends is that the depth interval
represents a buried A + AB + Bt horizon sequence in which some down-mixing is effected by
soil fauna. Given a rise in MS, P, Ca, Mn and other metals, no great leap of faith is required to
conclude that the absence of bone or burnt soil fragments is a combination of actual density of
particulates and the more sandy texture of sediments compared to those studied at the
Hatahara site.
Sediments above 70 cm or so, in contrast, leave little room for doubt that upwards to 36
cm the profile records the kinds of build-up associated with pre-Columbian settlement
activities that have already been observed in texturally clayey terras pretas (Figure 88). At the
risk of some repetition it can be re-iterated that variation in MS values appears to be somewhat
Chapter 5. The geoarchaeology of dark earths 153
Fe dependent and added that overall patterns in P, Ca, Mn and other metals appear to be
somewhat Al dependent. P, Ca, Mn and other normalised to Al peak at 56 cm and then drop in
relatively steady fashion towards 36 cm whilst MS normalised to Fe first rises to 56 cm and
then remains constant up to 36 cm, where a clear decrease is recorded. Low EC values at 56
cm, where pH peaks and the boundary between the A3 and A2 horizons are observed, suggest
a further subdivision that can be construed as evidence for a higher land surface. Whilst no
thin sections exist for A3 material, observations of microartefacts in the lower part of the A2
horizon (thin section 2) - including here pottery fragments, sponge spicules, burnt soil
fragments, bone fragments, and rubified clay aggregates – show some agreement with
elemental concentrations and can most likely be partially extended to sediments of the A3
horizon.
A3 horizon sediments (56 cm) show slightly higher Al and Fe contents that the lower part
of the A2 horizon (36 cm) with EC values suggesting an overall less porous sediment. The
higher net proportion of quartz particles observed in thin section 2 with respect to A-like
sediments in thin section 3 (which theoretically should resemble the A3 horizon) suggests
prima facie that substantial deposition of quartz sand is responsible for profile build up in the
A2 horizon. Considering the proximity of the sampling locale to the Negro river, aeolian
transportation of sand does not seem far fetched as a potential sedimentary input. However,
aside from a lack of indications of quartz grain rounding due to water action (if they are
alluvial sediments) or damage by saltation (if they have been rolled around after wind
transport), this model does not explain satisfactorily why a very unique sediment budget
existed only at a time when the 40 or so cm of settlement soils accreted. As discussed in
Section 4.1.2, the exact nature of these textural changes most likely reflects regressive erosion.
In this respect, the matrix-supported ped mimicking the characteristics of a clayey terra preta
(Figure 50) almost lacks porosity, suggesting it has survived intact most likely due to extreme,
clearly anthropogenic, compaction.
The preceding discussion highlights the preservation biases of grain-supported sediments,
already mentioned in the analysis of AC-2 and to be examined further in Section 5.1.6, in turn
explaining the very low concentrations of Co, P, Ca, Mn, and other elements at Açutuba
compared to clayey anthropogenic dark earths. This insight also complicates pedo-
stratigraphic inferences about profile build-up. For instance, without examining a thin section
for the A3 horizon, it cannot be conclusively overruled whether slight illuviation of A2
material is an important process at this depth interval. It will be offered here that only a slight
increase in Al and Fe and higher pH at 56-66, coupled with no clear evidence for high
concentrations of materials in thin section 3 (75-80 cm), makes this interpretation unlikely,
suggesting in turn that dissolved clayey material is being flushed out laterally along the
toposequence.
Chapter 5. The geoarchaeology of dark earths 154
Higher up the profile, an inflected rise in Al and Fe has been noted between 26 to 16 cm.
Correct to Al concentrations, P:Al decreases slightly whilst Mn:Al and especially Ca:Al rise
sharply. MS:Fe, which drops from A2 horizon values, remains constantly high at around
0.006. pH values reach neutral values. Implied here is a more clayey zone at around 26 cm,
which the micromorphological study samples only partially. Microscopic evidence for 16 cm
(lower part of AC-1.1), on the other hand, suggests a decrease but still significant volume in
microscopic charcoal, slightly lower concentrations of microartefacts, and proportions of clay
and quartz grains that are analogous to those observed at 35-40 cm. However, as discussed
previously, the optical characteristics of the fine mineral fraction just above 16 cm or so lack
the conspicuous opaque grey colours in OIL that have been discussed as evidence for
impregnation of by Mn oxides. This suggests that at this depth evidence for a different
pedogenetic regime is recorded. Although the impact of near surface processes is difficult to
disentangle, without speculating unnecessarily it can be suggested that sediments at 26 cm
suggest some form of discontinuity in dynamics that specify the characteristics of the depth
interval. It is possible that recolonisation by vegetation of the build-up of prior settlement
sediments is reworked by roots, leading to formation of a non-strongly melanised soil above
16 or so cm. On the other hand, much higher Ca and Mg concentrations near the surface
clearly likely record vegetation subsequently cleared through burning, resulting in higher pH
and a slight rise in MS values when corrected to Fe contents. The fall-off with depth observed
in this hypothetically sub-recent ash-derived Ca, with concentrations reducing 3 times in a 20
cm (from 16 to 36 cm), highlights that the premise that illuviation/down mixing in these soils
is shallow applies even in the case of the highly porous, grain-supported sandy dark earths of
the Açutuba site.
5.1.4.3 Profile AC-3 (Açutuba phase buried soil, terras mulatas)
Micromorphological observations (Table 34) reveal that the AC-3 profile is characterised
by grain-supported, texturally ‘sandy clay’ sediments that differ markedly from dark
anthropogenic soils observed at profile AC-1 and bear a strong resemblance to the A horizon
of profile AC-2 in terms of microstructure and organic staining of the fine mineral fraction.
However, optical properties of the fine mineral fraction of AC-3 show more reddish colours
under PPL, evidencing – in strict agreement with twice as high Fe concentrations – more
intense impregnation of clayey material with iron oxides. Thin sections for layers IIa and I,
immediately below the concentration of Açutuba phase pottery, show a drop in organic
staining and a decrease in always very infrequent microscopic charcoal fragments that suggest
an A + AB horizon sequence not unlike the A2 + AB transition at AC-2 but lacking in the
texturally more clay substrate of the latter exposure. This inference is consistent with a fall-off
pattern from peak Mn and MS values and a very low EC at 56 cm, pointing to a buried land
Chapter 5. The geoarchaeology of dark earths 155
surface (Figure 90). pH values, which are as high as profile AC-2, reach peak levels at 56 cm
but also remain high up to 36-46 cm. P concentrations rise to high values at 56 cm, the buried
land surface, but their slight decrease towards the upper part of the profile is misleading: P:Al
actually rises between 56 and 46 cm and is higher at 16 cm. This impression is corroborated
by very rare microartefacts in thin section (Table 34), including pottery, rubified clay
aggregates and burnt soil, as well as slightly higher silt-sized charcoal fragments, in Layer IIb,
pointing to reduced but significant enrichment of these soils with settlement debris at this
depth interval, most likely a partial result of the decomposition of artefacts and some in situ
burning.
Layer III sediments were not sampled for micromorphology and ICP-AES data bracket
this depth interval. However the boundary between Layers III and IV was recorded in the field
as a possible unconformity, suggesting hypothetical truncation of Layer III sediments prior to
re-deposition of sheet washed material. Strong agreement between particle size class
distribution in thin sections from Layer IV and Layer IIb, coupled with subtle textural
contrasts with respect to underlying sediments (Layer IIa, I), suggest this dynamic may
account for profile build above the Açutuba phase surface. In addition, it has a number of
noteworthy characteristics First, LOI weight loss data, arguably a measure of total carbon in
sandy soils, shows a double fall-off pattern, at 56 and at 26 cm below the surface, suggesting
the formation of an organic horizon at the hypothetically truncated Layer III-IV limit. Thin
section 1 (Layer IV), which lacks microartefacts and shows very low quantities of microscopic
charcoal in assorted size classes, reveals stronger organic staining than underlying sediments
and an undifferentiated b-fabric (XPL), pointing to an active A horizon at this depth and
towards the present surface. Second, continuously high P and MS values and relatively high
pH up to at least 16 cm either suggest Layer III and IV have been remobilised from locales in
which small quantities of settlement debris accumulate or are soils that have been lastingly
enhanced, most likely as a result of agricultural land use. This latter point is underscored
especially by MS values in Layers III and IV which, even if lower than Layers IIa and IIb and
decreasing with proximity to the current land surface, are consistent with near surface burning,
with Layer IV showing MS:Fe values comparable to the surface of HA-9 and Layer III
showing higher values, arguably comparable to A horizon measurement at the terra mulata
LG-4 profile. Thus, accepting the likelihood of some redeposited sediments, it is very
probable that these enhancements track decreasing intensity of in situ burning over time.
Chapter 5. The geoarchaeology of dark earths 156
5.1.4.4 Discussion
5.1.4.4.1 AC-1
A paucity of archaeological evidence from stratigraphic excavations in the immediate
vicinity of profile AC-1 limits the range of inferences that can be drawn from the
geoarchaeological analysis presented in the preceding section. However, some hopefully
meaningful extrapolations of the data can be attempted considering excavations of Unit 2 in
sector IA and the proximity of the Paredão urn cemetery located to the west of the sampled
profile. As regards excavations in Unit 2, it is important to reiterate that re-examination of the
ceramic assemblage has identified an Açutuba phase occupation located at approximately 80
cm below the surface. It is striking that at AC-1 the depth interval 86-96 cm – which identifies
the transition between the AB and B/A horizon – shows a high pH; slight levels of enrichment
with P, Ca, Mn, K, Sr, and Zn; low EC values consistent with an exposed surface; and MS
susceptibility values that approach near surface burning at profile HA-9. At Unit 2, despite
using different techniques, data reported by excavators similarly show levels of enrichment in
Ca and K that are higher than immediately overlying sediments (Heckenberger et al.
1999:361, Table 2). If this comparison is considered valid, it can be taken as a supporting
argument against the suggestion that enrichment at this depth is a simple outcome of down-
mixing or illuviation. It can also be suggested that a calibrated radiocarbon age of AD 120-340
(�-90724) from charcoal at 70-80 cm in Unit 2D provides an approximation to the age of the
initial land surface recorded at AC-1, lending support to Heckenberger et al.’s contention that
the modification of the soilscape at the site began as early as the beginning of the first
millennium AD.
At Unit 2, a Paredão phase occupation is recorded in melanised sediments about 50 cm
below the present surface, with chemical data showing substantial enrichment of sediments
compared to under- and overlying depth intervals. Above this (layer III in Heckenberger et al.
1999:360, Figure 5), sediments are considered to postdate pre-Columbian occupations and
show plough disturbance. If these observations are extrapolated to AC-1, there is a remarkable
agreement between the depth of the Paredão occupation and evidence for a land surface above
56 cm in AC-1. If this second comparison is also considered valid, it can be suggested that the
anthropic imprint in the A2 horizon at the AC-1 profile may date to approximately AD 890-
1160 (�-97527). A further comparison can be made by extrapolating the approximate depth of
the Paredão burial urns evidenced by a road cut to the immediate west of the AC-1 profile.
These vessels are located below the dark anthropogenic horizon, i.e. reach into the organically
depleted B/A or B horizon of the terra firme bluff at Açutuba sector I. On the basis of the
Chapter 5. The geoarchaeology of dark earths 157
geoarchaeological data presented for AC-1, it is possible to suggest that the land surface from
which these urns were buried could be represented by the sediment zone located below 56 cm,
that is the A3 horizon, which is marked by peak concentrations of various elements, relatively
high MS, and a higher pH than immediately overlying sediments.
On the other hand, micromorphological, physical and chemical data at the AC-1 column
highlight that at this exposure sediments located above the Paredão phase occupation show
significant levels of enrichment. It has been argued previously that depth-wise trends in these
concentrations do not necessarily evince that the depth of overall disturbance due to sub-recent
agriculture is as intense as discussed by excavators in Unit 2 (Heckenberger et al. 1999).
Moreover, clear indications exist that enrichment with inputs associated with settlement
activities is recorded at the relatively shallow depth of, going by chemical data, 26 cm and,
going by micromorphological data, as high as 18 cm, below the present surface. Based on the
geoarchaeological analyses, the likelihood that this represents a later Paredão or Guarita phase
occupation is high, and attention is drawn to the fact that archaeological topography maps
(Figure 84) for the site indicate the presence of a low lying mound some 40 m away from the
sampling locale of AC-1. These observations provide strong support for Heckenberger et al.’s
(1999; 2001) suggestion that, despite multiple occupations, broad stratigraphic contiguity
exists at the scale of the site sector.
As discussed in Section 4.1.2, the presence of a matrix-supported clayey ped in thin
section suggests that the onset of the latter process in the toposequence under consideration
may be relatively recent. Thus, the implicit lesson of high net rates of profile development that
can be drawn from the analyses of clayey dark earth sites like Hatahara, Lago do Limão and
Osvaldo, apply even more evidently to a landform in which the net build-up of perhaps some
wind transported sand is clearly offset by overall deflation induced by regressive erosion. On
the other hand, the development of a texturally more clayey soil towards the surface of AC-1
can be suggested to relate to re-vegetation resulting from human depopulation, which most
likely dates to, or just before, European colonisation of this part of the Amazon. Before this
time, geoarchaeological evidence from AC-1 clearly supports a continued occupation of the
locale from the latter part of the first millennium AD onwards.
5.1.4.4.2 AC-3
The study detects clear evidence of a buried land surface immediately underlying the
concentration of Açutuba phase pottery that enabled Lima et al. (2006) to segregate this early
Barrancoid-affiliated complex from the subsequent Manacapuru ceramic phase. This land
surface is a sandy Oxisol/Ultisol A+AB+B horizon sequence showing evidence of chemical
enrichment and magnetic enhancement that, on the one hand, can be unequivocally associated
Chapter 5. The geoarchaeology of dark earths 158
with human occupations yet, on the other, differs markedly from properties of sandy terras
pretas on the river front of the site (profile AC-1). Above the buried land surface, the study
records consistently high levels of magnetic enhancement and phosphorus – much higher than
the background AC-2 profile. Extrapolating from the analysis of terras mulatas at Lago
Grande, it can be surmised that this points to intensive use of fire on site, most likely
associated with an agricultural land use. A lack of possible truncations until 20 cm suggests
relatively continuous modification, in turn supporting the conclusion that these sandy terras
mulatas record more intensive agricultural land use which includes dedicated use of fire
(Denevan 1998, 2004).
Three radiocarbon dates – all of which have been assigned to the Açutuba phase (Lima et
al. 2006) – come from the 2 cubic meters of sediments sampled by profile AC-3. The first
comes from 90-100 cm below the surface in unit T9 and produces a calibrated age range of
410-170 BC (�-178910, the wide spread resulting from a 100 14C year standard deviation).
The next two come from sediments in Layer IIa of unit T10 and result in younger age ranges
of AD 430-550 and AD 410-600 (�-178908 and 9). Whilst sediments at 90-100 cm in T10 do
not show evidence of anthropogenically-induced enrichment, MS values at about 76 cm – the
approximate depth of the lowest of the younger charcoal fragments - are comparable to the
present land surface of the deposit and to values indicating near surface burning at the
background profile HA-9. Thus, the T9 date either represents down-mixed charcoal with a
large in-built age associated with site clearance and/or can be related to first millennium BC
dates from the 2004 reservatório excavations (e.g. �-202675, �-202677) and thus to emerging
evidence for an occupation associated with the Zone Hachured tradition (Lima 2005) or
Modelled incised complex IA (Petersen et al. 2003; Petersen et al. 2004). In contrast, the
younger and statistically indistinguishable dates at T10 provide a minimal age for the land
surface (layer IIa), the Açutuba assemblage at T9/T10, and the onset of sandy terras mulatas
recorded in Layers IIb and III.
Lima et al. (2006) have suggested that the Açutuba phase can be distinguished from the
Manacapuru phase in terms of contrasting features of the ceramic assemblage, overall
chronology, and the fact that occupations of the former did not result in the formation of
anthropogenic dark earths. The development of these soils in later occupations (Manacapuru,
Paredão, Guarita) would therefore signal differences in lifestyles, sedentarism, and population
densities. With some remarks about the older and younger brackets of the chronology of
Açutuba phase already in place (Chapter 4), the study finds evidence of soil enrichment but
lack of strong melanisation in: sediments embedding Açutuba phase remains at Profile HA-5;
sediments with valid dates in the Açutuba time range at Profile OS-1; sediments
hypothetically associated with Açutuba phase-occupations at Profile AC-1; and sediments
with Açutuba phase pottery at profile AC-3. Soils from the Lago do Limão site from which
Chapter 5. The geoarchaeology of dark earths 159
the Manacapuru phase shard dated to the 4-5th century AD was collected no doubt are partially
enriched yet, like all of the preceding Açutuba exemplars, show low levels of melanisation.
On the other hand, the study shows that thick or ‘well developed’ anthropogenic dark earth
horizons often result from overlapping Manacapuru and Paredão phase occupations, the
former setting the grounds by altering soil pH and kick starting some soil enrichment, the
latter resulting in profile development with, among others, more abundant ash, pottery and
bone. There can be little doubt that this signals a change in lifestyle, one in which such
landscape legacies as patches of vegetation disturbance, enriched soils, and standing
edible/useful domesticates of pioneer occupations are intensified and modified by later
occupations. Hence, continuous indications of near surface burning above mid 1st millennium
AD charcoal at AC-3 suggest that older histories of soilscape and vegetation modification
became accentuated at about this time, perhaps as a correlate to the emergence of dark earths
associated with the Manacapuru phase at sector II of the Açutuba site towards AD 410-550 (�-
106438).
5.1.5 The Nova Cidade site: settlement soils (Profile NC-1)
In Chapter 4, the Nova Cidade site was described as a large (80 ha) expanse of sandy terra
preta located some 15 km away from the Negro river, in the vicinity of a small tributary
streamlet, the Cuieras igarapé. It was mentioned that salvage operations (Neves and Costa
2001, 2004) had identified a 6 ha portion of the site with a large concentration of Paredão,
Manacapuru and Guarita phase remains, an important array of lithic pieces, as well as over
240 burial urns, some still preserving human bone inside them. Given that Nova Cidade was
almost completely destroyed by urban expansion, any inferences that can be drawn from an
examination of its soils is severely limited by a lack of precise contextual information.
However, the site is included in this study because its geographical location underscores the
fact that large expanses of dark earth can be found away from the main rivers and because the
sandy texture of its soils can be usefully compared to the analysis at the Açutuba site. A site
plan is presented in Figure 92.
Micromorphological observations show that the A1 horizon (Table 36) is characterised by
a grain-supported ‘sandy clay loam’ organised as grano-oriented clayey braces and small
inter-grain peds that show an organically-stained brown (PPL/OIL) fine mineral fraction with
a marginally speckled b-fabric. These clayey domains embed a moderately high concentration
of mostly silt-sized charcoal, including common gravel-sized charcoal, as well as rare
intrusive aggregates characterised by a limpid yellow fabric that evidence an origin lower in
the profile. A1 sediments bury overall less porous Ab sediments, which texturally change
from a sandy clay loam to sandy loam (Ab1) to a loamy sand (Ab2). However, far more
important are contrasts in the optical properties of the fine mineral fraction and embedded
Chapter 5. The geoarchaeology of dark earths 160
particulates: Ab sediments show a more organically-stained (PPL), ‘opaque’ grey (OIL) fine
mineral fraction with an undifferentiated (thin sections 2 to 4) to marginally speckled (thin
section 5) b-fabric. Embedded within the rare peds and mostly grano-oriented clayey braces
are very abundant mostly fine silt-sized charcoal (Figure 55, bottom right) and rare to
marginal microartefacts. Whilst intrusive clayey aggregates are in all cases marginal, Ab1
horizon sediments evidence some incorporation of sediments from the Ap and also aggregates
with limpid yellow clay fabric, indicating conveyor up mixing from much lower in the profile.
Ab2 horizon sediments instead evidence intrusive aggregates from Ab1 and also aggregates
with a less organically stained fabric that originate lower in the profile. It should be pointed
out that the volumetric contribution of these aggregates is negligible compared to the surface
area of the fine mineral fraction.
The buried AB horizon (thin sections 6 and 7, Table 36) is texturally even more sandy,
reveals a similar organisation than overlying sediments, shows a light organic staining (PPL),
brown colours under OIL, a marginally speckled b-fabric, and evidences a decreasing
abundance of silt-sized charcoal and organically-stained intrusive aggregates from higher and
lower in the profile. The Bt horizon (thin section 8) appears as a texturally more clayey ‘sandy
loam’ with a fine mineral fraction characterised by a limpid yellow clay with a striated b-
fabric, and only marginal isolated microscopic charcoal. Throughout the profile, illuvial clay
coatings are only observed embedded in a small ped in the Ab1 horizon. Unlike AC-1, the
shape and size of this ped do not allow the inference that it reflects formerly more clay soil
material; inferences that support this interpretation will nonetheless be presented below.
Whilst even the lowest thin section in profile NC-1 records a remarkably sandy sediment,
estimates of the fine mineral fraction suggest a rising trend towards the lower part of the
profile (not sampled for soil micromorphology). For instance, Al concentrations at 176 cm
(Table 35) approach values analogous to those measured in the HA-9 background profile at
Hatahara. Considering, however, that much lower Fe concentrations are recorded for this
depth and higher in the profile, the latter on a par with those measured in the sandy
background profile AC-2, it seems evident that NC-1 is at an advanced stage of
deferralitization that renders a more sandy texture in sediments overlying the AB horizon.
This inference in effect illuminates and supports some of the arguments about regressive
erosion that have been offered in the interpretation of profiles AC-1, 2, and 3 and qualifies the
appraisal of what appear to be comparatively extraordinarily low levels of
enrichment/enhancement given the highly melanised Ab horizon. The differential impact of
these dynamics, moreover, is emphasised by the contrast between very dense concentrations
of microscopic charcoal vis-à-vis very low concentrations of microartefacts.
Chapter 5. The geoarchaeology of dark earths 161
Regarded from the vantage point of physical and chemical data (Figure 94), AB and Bt
horizon sediments are highly distinctive in terms of most of the studied variables. pH values
for the Bt and AB horizon show relatively low values of 5.2-5.3, rising with decreasing depth.
These values are lower than most clayey dark earths studied but clearly higher than clayey
background profiles (LG-5, HA-9). The argument that higher soil pH is more easily achieved
in soils with a smaller volume of clay has already been advanced (see Section 5.1.4.1) and
may well explain these low but overall higher than background values, in turn suggesting that
they record buffering of the soil pH as a result of past anthropogenic inputs when the land
surface was lower in the profile. In this regard, the presence at 176 cm of Ca concentrations at
least three times higher than profile HA-9 suggests, on the hand, percolation of dissolved Ca
towards the bottom of the profile and, on the other hand, that the clear loss of the clay fraction
hinted by lower Al values higher in the profile is responsible for lower Ca retention.
Turning to other variables (Figure 94), Leco furnace data show that at around 105 cm
organic carbon constitutes 0.35 of 0.79 total carbon, representing 44.3% of the carbon pool.
This value compares well with the 50.3% total carbon recorded in the Ap horizon of profile
HA-9 which, it will be remembered, embeds small quantities of microscopic charcoal that are
comparable to the AB horizon in NC-1. P, Ca, Mn values are very low in the Bt and in the
lower part of the AB horizon but increase in overlying sediments. Al and Fe concentrations in
Ab2 horizon are very similar to those observed in the upper part of the AB horizon,
correlating reasonably well with the higher surface area of the fine mineral fraction observed
in thin section. In the Ab2, pH values are slightly lower than the AB horizon, a shift that
accompanies a slight inflection towards lower EC as MS values rise sharply despite an overall
decrease in Fe. P, Ca, and Mn concentrations also increase sharply compared to the AB
horizon. This increase is far more dramatic if corrected to Al concentrations, in turn
highlighting a fall off pattern that is characteristic of A+AB horizon sequence. These patterns
and the relatively important contribution of organic carbon to total carbon can be construed as
evidence that that the upper part of the macroscopically-described AB horizon represents an
old buried A horizon.
No physical and chemical data exist for the upper part of the Ab2 horizon but, given
constant Al and Fe concentrations at 61 cm with respect to 80 cm, a sharp increase in P, Ca,
Mn, a further increase in MS values and organic carbon values of 1.92 out of 2.15% total
carbon, i.e. about 89.3%, indicate that the lower part of the Ab1 horizon is a zone of
considerable enrichment. %Co data, in particular, are analogous to values observed in clayey
anthropogenic dark earths. The distribution of size classes of microscopic charcoal fragments
recalls samples from HA-5. Minute quantities of silt-sized bone fragments can be observed in
two of the thin sections studied from the profile but it is difficult to relate their presence with
any certainty to measured P and Ca. At a depth of 27 cm, the upper part of the Ab1, P, Ca and
Chapter 5. The geoarchaeology of dark earths 162
Mn values are lower than underlying sediments but organic carbon, which is lower than at 61
cm, still constitutes over 88% of the total carbon pool, its lower raw quantities showing a good
overall agreement with a decrease in microscopic charcoal recorded in thin section.
Above this, a reduction in the intensity of anthropogenic impact, the upward conveyor
action of soil fauna and the establishment of new vegetation above settlement-related
sediments is clearly indicated. Remembering that little can be said about the original
topography of the site and that the study samples the only surviving monolith of intact
sediments, it can at least be suggested that the very sharp drop in MS and pH towards the
surface hints at the mobilisation of sediments, perhaps through slope wash, that bury
settlement soils. A useful comparator in this regard is profile AC-1, where a more clayey zone
near the surface shares more characteristics with buried settlement soils. At NC-1, in contrast,
these characteristics – especially markedly optical characteristics of the fine mineral fraction -
appear to reflect a forest soil. It cannot be ascertained whether the microscopic charcoal
observed in the surface horizon represents sub-recent burning or indicates that upon
abandonment the locale was subject to clearance and burning associated with slash and burn
agriculture.
5.1.5.1 Discussion (OS-1)
If a lack of stratigraphic excavations at Nova Cidade, the result of the destruction of this
archaeological site by the expansion of the urban grid of Manaus, already limits the range
inferences that can be drawn from the analysis of profile NC-1, the low preservation of
microartefacts in thin section, no doubt an outcome of the sandy texture of the soil,
complicates pedo-stratigraphic inferences further. An observation that helps reflect back on
the soils at the Açutuba site is the fact profile NC-1 “starts off” as a clayey sediment yet shifts
to a far more sandy texture, more so that any of the samples from AC-1. This more
pronounced trend should be highlighted because Nova Cidade lacks a source of sandy
sediments that is comparable to the river bed of the Negro river, in turn suggesting that the
textural contrasts in these sediments result from the impact of processes of regressive erosion.
There are, however, no evident ‘relict’ peds such as observed at AC-1, making it on the whole
more difficult to ascertain whether the large pre-Columbian settlement that evidently existed
at the Nova Cidade locale was established on a more sandy substrate. One observation that
indirectly bears on the matter is the fact that the density of microscopic charcoal observed in
the fine mineral fraction is much higher than all other studied profiles. It is difficult to imagine
that these organic remains would have become embedded in clayey material if the texture of
these soils had not been more clayey in the past: clearly the smaller-sized particles would be
easily flushed though the soil system by rainwater.
Chapter 5. The geoarchaeology of dark earths 163
Even cursory examination of the depth-wise trends in chemical and physical data (Figure
94) leaves little doubts that a former land surface located between the lower part of the Ab2
horizon and the AB horizon was cleared and received substantial amounts of settlement
debris, in turn helping build up the profile considerably. Put another way, given that
micromorphological evidence shows no evidence for an illuvial zone at the depth in which
high values are recorded, it seems clear yet again that depth-wise variation of the studied
variables can be legitimately interpreted as averages of processes and inputs as the profile
accretes. This observation, which constitutes a cornerstone to the pedo-stratigraphic approach
adopted in this geoarchaeological study, thus not only obtains in the most sandy and porous of
the ceramic age anthropogenic dark earths examined in the study but also endorses the
suggestion that AB horizons in these soils most likely represent original A horizons that have
thereafter been strongly reworked as the profile accretes through the deposition of very large
amounts of settlement debris.
5.1.6 The Dona Stella site (Profile DS-1)
The Dona Stella site (Figure 95) has been described as a 1 ha lithic scatter in an area of
sandy soils located in the Negro-Solimões interfluvial terra firme, in the immediate vicinity of
a small stream. A cursory field examination of the DS-1 profile (Figure 96, right) reveals a
thin root layer (A1) underlain by successive white-to grey sandy sediments (E1-E3) which
overlie a dark, indurated spodic horizon (Bh1). The transition between E3 and Bh1 takes place
as an intermediately coloured grey sandy horizon that shows clear evidence of vertical
channels (E/B) penetrating into the Bh1. The Bh1 is underlain by lighter-coloured sediments
that track a progressive down-profile decrease in melanising constituents.
Since the early days of study at Dona Stella debate has existed within the Central Amazon
Project about the correct interpretation of this site stratigraphy, particularly because the
stemmed projectile point mentioned in Chapter 4 was found in dark-coloured sediments
contiguous with those recorded in the Bh1 horizon but laid bare by mining activities about 6
meters away from the excavations shown in Figure 96 (centre bottom). It would seem
straightforward to recognise this horizon as a buried soil but lithic remains and features are not
restricted to the dark sediments: isolated pieces or pockets of artefacts occur below the dark
horizon (pers. obs., 2006). In addition, at least one well-structured cuvette-shaped hearth was
observed by Costa (pers. comm., 2006) in the overlying white sands (E3) at the exposure
shown in Figure 96 (centre top). On the other hand, the profile shows many of the features that
are described as the toe-slope of the regional soil toposequence, i.e., it bears all the hallmarks
of a sandy podzol such as described by numerous studies of the evolution of the soil mantle
(Chauvel et al. 1987; Tardy and Roquin 1993; Lucas et al. 1996; Horbe et al. 2004; do
Chapter 5. The geoarchaeology of dark earths 164
Nascimento et al. 2004). In order to resolve this long-running dispute thin sections from the
profile shown in Figure 96 (right) were studied.
As might be expected, the micromorphological study reveals that sediments at different
depths in the profile are organised as a grain-supported microstructure (fine enaulic to coarse
monic c/f related distribution) composed of >95% silt to sand sized quartz grains (Table 37;
Figure 98, top left). Quartz grains generally cluster between >100 and <500 �m, are poorly
sorted, and are sub-angular to sub-rounded in shape. As in the case of Açutuba and Nova
Cidade, their characteristics do not suggest transport from elsewhere, confirming that the
small rain-fed stream that dissects the terra firme by the site is an unlikely candidate for the
kinds of high energy water flow that would result in over a meter of sand overburden. The fine
mineral fraction is sparse (<2% of solids) and composed mostly of grain-oriented irregular,
discontinuous braces (<80 �m wide) of organic- and Fe-rich clayey material which in places
(Figure 98, top middle) approximates the ‘welded’ and ‘flowed’ aggregate morphologies
described by Buurman et al. (2005). These morphologies are generally regarded as an outcome
of the decomposition of roots and seen to characterise the spodic horizon of podzols (Buurman
and Jongmans 2005). Their presence in samples 4, 5, 6 and 7 settles one aspect of the
discussion: the dark horizon is a spodic horizon, as noted in the macroscopic description.
However, when the fine mineral fraction that is characterised by these morphologies is
examined under oblique incident light, it becomes evident that at different densities in samples
1, 2, 4, and especially at much higher densities in samples 5, 6, and 7, the fine mineral fraction
embeds substantial amounts of silt to fine sand-sized microscopic charcoal fragments (Figure
98, top right, bottom, left, middle). Much more rarely, small quantities of Fe-replaced organic
matter are also observed, for instance an almost intact Fe-replaced root fragment in sample 6,
and an intact Fe-replaced faecal pellet composed of plant tissue in sample 7 (Figure 99, Table
38). These characteristics suggest that charcoal plays no small role in the strongly melanised
aspect of the Bh1 horizon. In addition, burnt soil, isolated sponge spicules and, significantly,
single fine sand-sized rounded aggregates of rubified clay are recorded in samples 5 and 6
(Figure 98, bottom, right). These aggregates differ in aspect when compared to the rubified
clay aggregates observed in thin sections from ceramic age sites in that they show more
birefringent domains, suggesting a clay source distinct from the B horizon of the region. If
these aggregates embedded any of the temper types observed in ceramic age soils (e.g. Figure
51), it would be straightforward to classify them as fragments of ceramic shards.
Physical and chemical data for this profile (Table 38, Figure 99) highlight that the Bh1
horizon is rich in sesquioxides and organic carbon, show slightly higher MS than near surface
sediments (but this may co-vary with total Fe), and, surprisingly, show high P and an unusual
inflection in pH values. From the standpoint of the preceding analyses, it is difficult to avoid
Chapter 5. The geoarchaeology of dark earths 165
the suggestion that these peaks reflect a former A horizon enriched by inputs associated with
redundant human occupations.
5.1.6.1 Discussion (DS-1)
The preceding observations evidence that samples from the EB (thin section 4) and Bh1
(thin sections 5, 6, and 7) horizons are not composed exclusively of illuviated amorphous
organic matter as predicted by the classic theory of podzolisation (see Buurman and Jongmans
2005) but also show quantities of microscopic charcoal that immediately recalls
micromorphological characteristics of ceramic age, texturally-sandy anthropogenic dark earths
(cf. Figure 98, bottom, middle, and Figure 55, bottom right, from Nova Cidade), let alone
other preceramic contexts (Chapter 3, sections 3 and 3.2). Thus, whilst the Bh1 horizon shows
the classic characteristics of a sandy, well-drained podzol, higher concentrations of charcoal,
rubified clay, possible magnetic enhancement and possible P enrichment cannot be explained
away as a result of illuviation: in some cases particles are too big to have been mobilised
through the pore system; in others the grano-oriented distribution of the fine mineral fraction
points to relict features of a formerly more clayey soil mantle. Considering the presence of
archaeological artefacts and physical and chemical data, therefore, it seems possible that the
EB + Bh1 +Bh2 sequence represents a former A+AB + B horizon sequence that has suffered
the impact of regressive erosion or even approximates the Ap+A2+AB sequence discussed in
profile AC-2. Preservation of the fine mineral fraction in sample 4 is too sparse to make
definitive statements but it should be noted that the E horizon could form by accretion as
deferralitization produces a shift from a more clayey, rainforest-bearing soil (see root casts in
Figure 96, left and centre bottom) to a more sandy low caatinga forest-bearing soil like
observed at present: podzolisation of a texturally more clayey A+AB horizon sequence would
result in decreased phytostabilisation and, thus, mobilisation of less consolidated sands from
the top and mid slope prior to subsequent events of podzolisation (Figure 100).
A key question is the timing of these dynamics. The answer to this can only be
approximated: as noted earlier radiocarbon dating of charcoal at the site has produced a wide
range of ages covering the first half of the Holocene. However, 13C measurements from
charcoal fragments are worthy of note: values range between -24.6 and -30 °/oo with
decreasing age, at face value evidencing more dense rainforest vegetation related to
increasingly warmer condition as the mid Holocene is approached. 13C measurements from
sediment samples for the Bh1 horizon range between -27.05 and -26.74 °/oo. We now know
that the organic matter in these sediments is likely to be substantially in situ: it is thus possible
that a mid 7th millennium BP age can be assigned to the organic matter + charcoal deposited in
them (Figure 99, bottom, right: green area represents range of SOM 13C). If this interpretation
is correct, human inhabitants of the earlier part of the Holocene may have occupied a locale
Chapter 5. The geoarchaeology of dark earths 166
with a vegetation physiognomy less open than we observe in the present prior to the
chemically erosion and burial of the original A+AB horizon sequence at some point after the
mid Holocene.
It is worthy of note that caatinga forests are considered less prone to tree throws compared
to tall rainforest growing on clayey Oxisols (Rankin-de-Merona et al. 1990). This may imply
that mixing of habitation debris at the site may have been more active when the locale was
characterised by clayey soils and taller rainforest vegetation, in turn supporting the suggestion
that a bifacially-reduced stemmed projectile point found in the Bh1 was in situ, that deep
artefacts most likely have penetrated into the lower sediment beds through the action of roots
that today appear as decomposed root casts, and that redundant occupations at the same locale
led to significant enrichment of the soil mantle and relict anthrosol features in sediments of the
EB+Bh1 horizon sequence.
167
Chapter 6
SYNTHESIS
The main findings of this dissertation map onto the broad goals set out in Chapter 1: first,
to ascertain the character and time-depth of human practices that resulted in anthropogenic
landscape transformations in the Amazon basin; second, to establish the formation processes
and variability of Amazonian dark earths in the Negro-Solimões confluence area. As I noted
in Chapter 1, these two goals are equivalent to examining the ultimate and proximate causes
for the emergence of anthropogenic dark earths. It is useful to outline how they have been
fulfilled in reverse order, that is, to first summarise some of the most salient results of the
geoarchaeological study presented in Chapter 5 and, next, to employ the archaeological
account offered in Chapter 3 and Chapter 4 to discuss some of the broader implications of the
dissertation. Some of the limitations of this research can then be briefly scrutinised with a
view to identifying how it might be continued in the future. Finally, I conclude the dissertation
by offering some thoughts on how this research contributes to the broader perspective of
Historical Ecology.
1. THE GEOARCHAEOLOGICAL STUDY
Attention to the micromorphological and physico-chemical characteristics of soils at Dona
Stella, coupled with an interpretation of 13C isotopes of soil organic matter and dated charcoal
fragments, highlight that a fundamental background to examine the formation processes of
archaeological sites in the Negro-Solimões confluence area is to take stock of landscape
evolutionary dynamics that shape the regional soil toposequence. In their most extreme form,
the latter are marked by dynamics of regressive erosion that prompt the transformation of
clayey Oxisols characterised by an A+AB+B horizon sequence into giant sandy Spodosols
that are characterised by one or more deep spodic horizons (Bh or Bs) overlain by eluvial
horizons (E). At Dona Stella, microscopic observations show that the dark horizon in which
archaeological artefacts are found constitutes a former A+AB horizon sequence. This
sequence signals a former land surface whose topsoil first became podzolised and then was
gradually buried by upslope sandy sediments released by the effects of the same overall
processes. This reconstruction suggests that at the time of occupation, the locale may have
supported an arboreal vegetation typical of more clayey soils.
Chapter 6. Synthesis 168
The study shows that the spodic horizon at Dona Stella is characterised by slightly higher
pH, some magnetic enhancement, concentrations of phosphorus, and veritable quantities of
microscopic charcoal. Whilst a lack of comparative baselines (i.e. similar podzols with no
evidence of archaeological remains) prevents me from strongly asserting that all of the latter
reflect anthropogenic inputs, it is relevant to note that these conditions mimic those recorded
in other preceramic occupations in the northwest Amazon (Mora 1991; 2003b, see Chapter 3).
In addition, microscopic observations at the Dona Stella site record the presence of fragments
of rubified clay of non-local origin buried in the Spodic horizon. These fragments obviously
cannot be interpreted as evidence for the use of pottery during the first half of the Holocene.
However, they do echo reports of fragments of rubified clay at other preceramic sites, notably
those of the Massangana phase in the upper Madeira basin (Miller 1992a, see Chapter 3). One
can envision that further commonalities between these sites can be ascertained by future
research.
An emphasis on the evolutionary pathways of the regional soil mantle is also useful to
understand the variability and characterise formation processes of late Holocene
anthropogenic dark earths. Micromorphological evidence shows that textural variability of
these soils is partially inherited from the parent material and partially the result of processes of
regressive erosion that are similar to, yet less severe than, those recorded at the Dona Stella
site. This implies that sandy-textured anthropogenic dark earths, namely the Açutuba and
Nova Cidade sites, can best be understood as ‘clay-depleted’ soils. One corollary of these
observations is that these soils show an inferior potential for the preservation of anthropic
inputs and, consequently, exhibit much lower values in all measured physical and chemical
parameters. Aside from evident archaeological consequences, this suggests that soil chemistry
cannot be used to argue for less ‘intense’ occupations: soils at the Açutuba site, for instance,
are likely to have been more clayey about a thousand years ago. Another corollary is that
anthropogenic dark earths also need to be understood as outcomes of anthropogenic
transformations which took and take place within a landscape that is in flux.
The study next substantiates that physical and chemical parameters of pottery-rich
anthropogenic dark earths (terras pretas) show clear differences compared with lighter
coloured but evidently enriched soils occurring on the hinterland of these sites (terras
mulatas). Focusing first on terras pretas, the magnitude of soil enrichment gauged through
bulk sample measurements is impressive and bears absolutely no relation to the location of
sites near white- or black-water alluvial bodies. Confirming previous observations (Lima et al.
2002), the study highlights the ubiquity of microscopic bone, charcoal, pottery and rubified
clay within these soils, and also provides a much richer dataset to discuss their role in shaping
high pools of soil nutrients. In this specific regard, the gap between the microscopic scale of
Chapter 6. Synthesis 169
soil micromorphological observations and the macro scale of soil chemical measurements on
bulk samples reveals its limitations. The ubiquitous bone fragments observed in these soils
cannot be conclusively regarded as the main source of phosphorus or calcium because their
relative contribution to the bulk chemical signature compared to the enriched clay matrix
remains to be ascertained. Taking steps to conduct this comparison may be highly significant
to evaluate whether particular pre-Columbian inhabitation practices develop a positive
feedback loop between the concentration of faunal remains – particularly aquatic fauna – and
the development of nutrient pools of agronomic significance. This is a relationship that has
wider implications for understandings the actual impact that pre-Columbian settlement
practices may have had on the ‘full breadth’ of the landscape of Amazonia.
The study documents very significant levels of magnetic enhancement and relates these
measurements to the deposition of fired clay (pottery and rubified clay) and near-surface
burning of plant matter. It also ascertains that very large amounts of microscopic charcoal are
the most likely sources of high carbon concentrations recorded in these soils, establishes that
they contribute significantly to soil melanisation, and offers that potentially significant sources
include soot accumulating on the underside of thatch roofing and organic pottery temper such
as caraipé. Whilst research by soil scientists repeteadly affirms the importance of black
carbon for high nutrient retention in these soils (Glaser et al. 2003; Steiner et al. 2004; Liang
et al. 2006; Solomon et al. 2007), the study also offers that inputs of large quantities of ash –
inferred indirectly from the presence of illuvial clay coatings and auto-fluorescent silica
phytoliths, among others – may have been crucial to concentrate plant-borne metals at several
orders of magnitude above quantities measured in background soils or present in the regional
parent material (Costa and Moraes 1998).30 Ash may also be key to achieve the enduring
increase of soil pH recorded in dark earths, and, most significantly, important for up-building
sedimentary deposits at these sites.
The volumetric importance of microscopic constituents such as pottery, bone, charcoal,
rubified clay, and ash is highly significant because most of studied sites are located in ‘flat’
landforms which lack sedimentary sources in the immediate vicinity. In some ways, this may
tempt archaeologists into considering the stratigraphic characteristics of anthropogenic dark
earths as radically different from other types of open-air sites. The study examines excavation
profiles using a pedo-stratigraphic approach and demonstrates that this is far from being the
case, i.e. anthropogenic dark earths cannot be understood exclusively as thick A horizons that
have expanded downwards. Instead, and very much in contrast, these soils constitute accreting
deposits that record the development of progressively higher occupation surfaces over time
30 Plant-borne concentrations of Mn deserve further attention because manganese oxides are known to adsorb a
wide range of metals. I believe that as pH is raised Mn becomes less plant-available, tends to form oxides, and this contributes significantly to overall soil melanisation.
Chapter 6. Synthesis 170
(Woods 1995). From a microscopic perspective, the up-build of these deposits appears as an
outcome of the accumulation of settlement debris; faunally-induced burrowing, mixing, and/or
churning of soil material (Johnson et al. 2005b); the upwards or ‘conveyor’ translocation of
sediments from lower in the deposit (Vacher et al. 1998); a higher overall deposition of
organic matter; and perhaps the neoformation or re-precipitation of dissolved kaolinite (Lucas
et al. 1996).
From a macroscopic point of view, comparisons between more than one exposure and the
results of previous excavations at Açutuba, Hatahara, and Lago Grande, both confirm and
expand the suggestion (Vacher et al. 1998; Heckenberger et al. 1999; Rebellato 2007) that
expanses of anthropogenic dark earths can show broad pedo-stratigraphic integrity at the scale
of the landform. At Lago Grande, Hatahara, and Osvaldo, both the pedo-stratigraphic analyses
and archaeological evidence suggest that occupations of different groups had a cumulative
effect on the soils and, no doubt, on the vegetation characteristics of specific locales. At both
Hatahara and Lago Grande, I argue, Paredão-age anthropogenic dark earths formed on an
already anthropogenically-modified soilscape resulting from apparently less intense
Manacapuru occupations, the latter preceded by events of clearance, even less intense Açutuba
phase occupations, and most likely events of re-vegetation that minimally span moments of
the first millennium AD31.
These observations re-examine the model of rapid formation of anthropogenic dark earths
advanced by Neves et al. (2003; 2004). Paradoxically this model offers partial support to a
modified version of Meggers’ (1991; 1995; 2001a) suggestion that large Amazonian sites are
the result of reiterated and overlapping short-lived occupations (e.g. Neves and Petersen
2006). Whilst I have few doubts that short, one or two century-long occupations can have a
significant impact on the physical and chemical characteristics of the soil mantle (Chapter 3),
the contemporary ages of radiocarbon dates from the 200 m distant Mounds 1 and 2 at
Hatahara strongly suggest that possibly during the late 1st millennium BC, and certainly by the
late 1st millennium AD, this locale harboured a relatively large settlement. Examined
carefully, the radiocarbon evidence from Lago Grande also documents what is most likely a
continued occupation over the entire peninsular area of the site starting from late Manacapuru
times and reaching to early Guarita times. It is evident that these locales record many centuries
of soil modification and thus reasonable to suggest that thick deposits of anthropogenic dark
earths formed as the remains of overlapping, stratigraphically-distinct occupations accreted on
top of each other. From a pedo-stratigraphic perspective, the matter can be stated as follows:
31 With less evident precision, I advance a similar argument about the Osvaldo site, where I suspect a Paredão
phase occupation distinct from the preceding Manacapuru occupation remains insufficiently documented. Both, in my opinion, are preceded by an occupation in the time range of the Açutuba phase (cf. Chirinos 2007).
Chapter 6. Synthesis 171
What in the field is often described as an AB horizon is in reality a transformed and buried A
horizon, frequently associated to Manacapuru age occupations. What appear in stratigraphic
cuts as subhorizons of a “deep” anthropogenic A horizon are in reality different occupation
surfaces associated to the Manacapuru, Paredão and Guarita phases.32
The study also offers a series of specific interpretations about the formation processes of
these soils. Complementing inferences about the importance of soot and ash within roofed and
walled structures, evidence for compaction in at least one thin section suggests that, aside
from middens and gardens (Andrade 1986; Mora 1991; Hecht 2003), houses with earthen
floors could constitute important loci for the formation of settlement-related anthropogenic
dark earths (see also Kern 1996; Kern et al. 2004; Erickson 2003). At Hatahara a comparison
of micromorphological, physical and chemical characteristics of sediments making up the
‘overburden’ of ‘earthmounds’ contradicts the hypothesis that these were built simply by
mobilising sediments from the immediate vicinity of each feature. Instead, a more complex
scenario that includes ‘facies’ of midden refuse, accreting house floor deposits, and their
reworking as platforms can be argued. An analysis of depth-wise variability in the chemical
makeup of soils that constitute Mound 1 of the Lago Grande site suggests a similarly complex
scenario, in this case including a partial change in land-use prior to mound build-up, build-up
of house floors, and deliberate piling of sediments from the vicinity of the earthmound.
Although I have previously stated that inter-site comparison is complicated by an inability to
control inherited parent material variability, it is important to mention that texturally-similar
‘overburden’ sediments of Mound 1 at Lago Grande and Mound 2 at Hatahara show important
similarities that could reveal analogous formation processes.
Finally, the geoarchaeological study angles on the distinction between terras pretas and
terras mulatas. Whilst I do not think that this distinction is absolute and would be the first to
admit that the two exemplars I have studied most likely constitute the ‘tip of the iceberg’, I
argue that the presence of markedly different concentrations of microscopic debris in terras
pretas and terras mulatas validates the heuristic utility of the distinction. In this respect,
evidence presented in the geoarchaeological study documents intriguing forms of pre-
Columbian soil modification. At the Lago Grande site, pedo-stratigraphic analyses of the
Paredão phase terra mulata horizon detect evidence for intensive burning and the use of
deliberate soil amendments techniques. At the Açutuba site, pedo-stratigraphic analyses of
sediments overlying the Açutuba phase assemblage suggest that continued near-surface
burning has taken place as these soils accrete. These observations endorse different opinions
that terras mulatas are most likely a result of different forms of pre-Columbian land use
32 It is unfortunate that none of the micromorphological observations I have compiled permit advancing strong
suggestions that soils at a given depth were subject to cultivation. As I argue in the following section, I believe that this was the case during the final centuries before European contact.
Chapter 6. Synthesis 172
(Sombroek 1966; Andrade 1986, 1988; Woods and McCann 1999; McCann et al. 2001;
Heckenberger et al. 2003; Heckenberger et al. 2007; Denevan 2004) and support Lima’s et
al.’s (2006) hypothesis that a change in lifestyles is recorded in the central Amazon region
after the mid 1st millennium AD. This model strongly resonates with archaeological
interpretations offered by Colombian researchers for approximately the same time range in the
Araracuara plateau: the latter research highlights the presence of brown anthropogenic soils in
site-peripheral position; postulates shifts in land-use patterns of specific locales; and
highlights pollen evidence for a diversification in the crop repertoire, more open conditions,
and possible intensification of palm trees (Andrade 1986; Mora 1991; Herrera et al. 1992b;
Herrera et al. 1992c).33
2. ANTHROPOGENIC LANDSCAPE TRANSFORMATIONS AND
DOMESTICATION IN THE LANDSCAPE OF AMAZONIA
The findings summarised previously provide a prism through which some of the main
points raised throughout the dissertation can be examined. In Chapter 3 I marshalled published
palaeo-ecological and archaeological data to provide an account of the origins of sedentary
lifestyles in the Amazon basin. I argued that the human colonisation of the Amazon basin took
place when climatic and vegetation characteristics of the region were significantly different
from what we observe at present; was both enabled by and resulted in the rapid onset of
processes of plant semi-domestication which led to the formation of anthropogenic clumps of
edible fruit trees; and kick-started dynamics of modification of biotic and abiotic components
of the Amazonian landscape – plant biodiversity and soil nutrient status – in locales which
were frequently revisited by preceramic communities. I argued further that the reiteration of
these agrilocalities early on permitted the successful introduction of allochtonous domesticates
and their cultivation in itinerantly-visited gardens near natural concentrations of aquatic
resources.
Evidence was surveyed for the presence of a mosaic of different lifestyles in the region as
ameliorating climatic conditions led towards the mid Holocene climatic optimum. The effects
of the latter, which are recorded globally as a rise in sea-level, were felt as far upstream as the
middle reaches of the Amazon river. With this framework in place, I reviewed published
evidence for shell-fisher groups of the lower Amazon in order to assess Lathrap’s (1977)
suggestion that root crop horticulture and pottery making had originated during the early
Holocene in this part of the basin. Although I find that consistent chronological evidence
33 As discussed in Chapter 4, emerging plant fossil evidence from the Hatahara site (Bozarth et al. 2008)– which
like the Araracuara research shows more open conditions (abundant grass phytoliths), a wider range of cultivars (including maize), and evidence for the use of peach palm (Bactris gasipaes) – appears to point in the same overall direction.
Chapter 6. Synthesis 173
strengthens Roosevelt’s claim that she has identified early Holocene pottery, I surmise that
some of the shards claimed to be this old are intrusive from later Formative occupations which
are unlikely to date before ca. 4.0 cal kyr BP (2000 BC). Once intrusive wares are extricated
from consideration, the Ceramic Archaic evidence from the lower Amazon falls into a pattern
that is not without precedent in other early cases of pottery use among foragers (e.g. Williams
2003; Oyuela-Caycedo and Bonzani 2005): these groups may have not invested in the
production of ceramic vessels that were technically apt or primarily used for cooking or
prolonged boiling.
I next focused attention on the scant but highly suggestive evidence for the coming into
use of crops recorded as important starch-yielders among later-day Amazonian communities,
Zea mays and Manihot sp.. I highlighted evidence for the preceramic cultivation of Zea mays
before the mid Holocene in the westernmost Amazon and the northwest Amazon (L. Ayauchi
and Abeja site); pointed out that groups in the latter region were consuming Manihot sp. at
least by the mid Holocene (Abeja site); and highlighted that groups in southwest Amazonia
(the Massangana phase) adopted lifestyles that permitted the formation of anthropogenic dark
earths well before the widespread adoption of pottery in western Amazonia. Given that
southwest Amazonia falls within the broad area where the wild ancestor of modern
domesticated manioc grows, I argued that these early forms of sedentism were associated with
the founder effect of Manihot cultivars of the lineage of M. esculenta spp. flabellifolia, at
present regarded as the ancestor of all known cultivated manioc landraces.
The inference that mid Holocene preceramic dark earths of the Massangana phase are
associated with the coming into use of manioc as a dietary staple has some important
implications for understanding the true significance of anthropogenic dark earths in the
Amazon basin and beyond. If the palaeo-biogeography that can be reconstructed from genetic
studies of Manihot is correct, i.e. if all manioc landraces do derive from the lineage of M.
esculenta spp. flabellifolia, the only reasonable way to explain the presence of early Manihot
sp. microfossils in assemblages north and west of the Amazon basin is to argue that they
represent selection of Manihot species that are not M. esculenta spp. flabellifolia, and to
suggest that a more widespread domesticated germplasm became eroded by specific landraces
of Manihot esculenta later in time. In Chapter 3, I advanced the argument that domestication
of sweet Manihot esculenta by preceramic populations may have achieved as much at around
the mid Holocene, and suggested that subsequent cultivation and processing of Manihot by
ceramic groups employing fire-worthy vessels to detoxify tubers and usufruct from their
secondary products, would have relaxed selective pressures on low contents of cyanogenic
glucosides. I argued that this would have led to the evolution of the toxic yet pest-resistant and
high starch-yielding varieties of Manihot esculenta known as bitter manioc.
Chapter 6. Synthesis 174
This hypothetical historical ecology of manioc is important to the argument advanced in
this dissertation because the broad geographic distribution of sweet and bitter manioc varieties
would appear to co-pattern with ceramic complexes recorded in the basin during the late
Holocene. In Chapter 3 I argued that the emergence of sedentary lifestyles in the region took
place around the 4th millennium BP, i.e. towards 2000 BC, as two interaction spheres – one
that can be linked to trans-Andean interaction and another that can be related to populations
from beyond the northern rim of the Amazon basin – expanded into the region. Whilst
relatively enduring occupations appear to have taken place at locales belonging to one or the
other interaction sphere – recall sites from the upper Pachitea, Marajó Island, Sangay/Huapula,
the Ucayali, the Santarém region, and so forth – only ceramic assemblages of the northern half
of the basin (Mora et al. 1988; Roosevelt et al. 1996; Roosevelt 2000) initially record the
presence of flat platters that point to the preparation of manioc farinha, perhaps also of maize
tortillas. The outcome of these early moments of colonisation is not straightforward to follow:
an interruption between them and later ceramists of the late 1st millennium BC and early 1st
millennium AD may yet strengthen Meggers’ and Danon’s (1988) case for a climatically-
induced hiatus in the archaeological record of the middle and lower Amazon.
Ceramic complexes of the Barrancoid and Polychrome traditions make their appearance in
the landscape of the middle and lower reaches of the Amazon basin towards the later centuries
of the 1st millennium BC and early centuries of the 1st millennium AD. As discussed in
Chapter 3, this is the moment when Formative societies ‘take root’ in the eastern half of the
Amazon basin and initiate a trend that culminates in the development of demographically-
dense societies recorded at the time of European contact (Lathrap 1970b; Eden et al. 1984;
Herrera et al. 1992b; Roosevelt 1999a; Heckenberger et al. 1999; Petersen et al. 2001; Schaan
2004; Neves 2005, 2008). As discussed by Lathrap, within the Amazon basin, Barrancoid
tradition pottery appears to ‘expand’ all the way to the middle Ucayali and is recorded as far
east as the Santarém region. Literature reviewed in Chapter 3 suggests that the Barrancoid
tradition most likely originates in the lower Orinoco, where researchers have for a long time
suggested that the horticultural repertoire of Barrancoid communities relied on the cultivation
of manioc (Rouse and Cruxent 1963; Sanoja 1979). Barrancoid pottery would seem to expand
into the Amazon region primarily via the Guianas and secondarily via the upper Orinoco-
Casiquiare-Negro river passage, regions in which anthropogenic dark earth exemplars are
found and in which today bitter manioc constitutes by far the most important starch-yielding
crop. If the broader historical ecology of Manihot summarised above has any merit, it might
indicate that the key factor that kick-starts the widespread development of anthropogenic dark
earths in the Central Amazon region is none other than the introduction of bitter manioc by
Chapter 6. Synthesis 175
Barrancoid groups, followed by population growth and agricultural intensification that is
respectively tracked by the formation of terras pretas and terras mulatas.34.
Floodplain soils – the varzea - have figured prominently in accounts of Amazonian
population growth (Lathrap 1970b; Carneiro 1970; Denevan 1996; Roosevelt 1991, 1999a).
The várzea is good for cultivating rapid-growth species that include maize and specific
manioc varieties (Hiraoka 1989; Hiraoka et al. 2003; Shorr 2000; Fraser and Clement 2008).
Early ethnohistorical accounts clearly record its use in the first centuries of European
colonisation (Porro 1994). However, a somewhat unpredictable flooding seasonality (Meggers
1971; cf. Irion et al. 1997) and limited overall extent at a regional level makes it unlikely that
várzea cultivation sustained large regional populations. In contrast, the distribution of
anthropogenic dark earths evidences a regionality that extends well beyond areas in which
floodplain soils are available (Heckenberger et al. 1999; Petersen et al. 2001; Neves 2003).
How, then, should population growth towards the latter part of the Amazonian archaeological
sequence be understood? Perhaps an important clue lies in the landscape legacy character of
anthropogenic dark earths: data on the the isotopic composition of human bones from different
parts of the Amazon basin shows that a progressively more maize-based diet only became a
reality during the last centuries before European contact (Chapter 3, Roosevelt 1989b;
Roosevelt 2000), i.e. a few centuries after anthropogenic dark earths have formed (Chapters 4
and 5). It is possible that this shift in the diet is associated with the reutilisation of
anthropogenic dark earths for cultivation, i.e. that gardening in settlements and the re-use of
former settlements as gardens permitted an increasing reliance on the terra firme cultivation of
acid-intolerant Zea mays. Thus, in some parts of the Amazon basin, a shift in the use of maize
from festive ingredient (Raymond 1993) to dietary staple may have been determined by the
overall effects which proceses of population growth associated to the intensification of bitter
manioc left as a landscape legacy on the soil mantle.
3. REFLECTIONS ON THE RESEARCH DESIGN OF THE DISSERTATION
Taking inspiration from other investigations (French 2003), the geoarchaeological study
adopted a methodological approach close to palaeo-pedology. Without the benefit of
actualistic observations (Schmidt and Heckenberger 2006; Fraser et al. 2008), it was
conceived as an archaeological investigation of anthropogenic dark earths focused on soil
toposequences and land use. The dissertation shows that this approach has substantial merits:
by examining the interaction between anthropogenic remains and the actual variability of soils
it has been possible to learn a great deal about what anthropogenic dark earths are, how they
34 The data from the upper Madeira basin are as yet too coarse to permit extending this inference but, with Neves
(2008), I have little doubt that this region holds important clues for understanding multiple aspects of Amazonian pre-Columbian history .
Chapter 6. Synthesis 176
formed, and what evidence for past land use they record. However, with the benefit of this
much better understanding – in my mind dark earths are now certainly less of a black box – I
can envision different ways to tackle similar and novel questions in the future.
My sense is that a more balanced and coordinated combination between soil
micromorphological studies, geochemical sub-surface prospection, and palaeobotanical
approaches is in order. The latter two approaches have been rehearsed at the Hatahara site
(Bozarth and Woods 2005; Bozarth et al. 2008; Grosch 2005; Rebellato 2007). It is, therefore,
the gap evident between these studies and the research presented in this dissertation that
deserves our attention. For instance, whilst the geoarchaeological study in Chapter 5 controls
the formation process of each studied soil column, the data cannot be extrapolated horizontally
and, at best, we catch only the first glimpses of what could be achieved through an intensive
on- and off-site landscape archaeology focused on the soil mantle. Visually compelling maps
of geochemical variability presented by Rebellato (2007) interpolate from a wide sampling
grid (25 m) and are interpreted principally on the basis of inferences about macroscopic
remains. Plant microfossil data presented by Bozarth et al. (2005; 2008) show the presence of
maize and peach palm but lack adequate control of the ‘biography’ of the sampled soil
column, in turn limiting inferences about what the changing frequency of phytoliths imply.
These remarks are not meant as criticism of the good work of my colleagues, nor as self-
deprecation. Instead my remarks argue that to approach these kinds of open-air sites and
hinterlands, systematic and coordinated integration between approaches is necessary. Off-site
and on-site grids – the former relatively widely spaced (every 25-50-100-250-500 m with
distance from site), the latter requiring relatively tight horizontal spacing (every 5-10 m) are
crucial. Good control of soil texture trends and horizonation patterns using macroscopic
descriptions, micromorphological observations, soil geochemistry, and magnetic susceptibility
every 10 cm by depth is necessary. Systematic sampling, extraction and analysis of macro and
microfossils – including here not only charcoal, phytoliths, pollen, and starch grains but also
the extraction and quantification of other microscopic remains such as bone fragments (see
Coil et al. 2003), is evidently essential to draw a number of important inferences. Always
coupled with an understanding of conventional archaeological evidence, the study of these
kinds of environmental evidence, perhaps also pollen cores (Piperno and Pearsall 1998),
present-day botanical inventories (Balée 1994; Erickson 2006), and actualistic data, are the
ingredients to build a regional account about inhabitation practices and land use patterns
recorded at sites with anthropogenic dark earths.
It might be asked to what extent this level of intensive and hence, expensive research is
necessary to address broader archaeological questions. My answer to this question is
Chapter 6. Synthesis 177
straightforward: much as I believe that the development of solid regional sequences based on
typing of artefacts and radiocarbon dating will most likely remain at the forefront of
Amazonian research for some time to come, it is evident that many questions about past
lifestyles cannot be addressed by conventional archaeological methods. Not only are there
limits to the inferences than can be drawn exclusively from site size, pottery styles and
quantities, number of ring-ditches and roads, but arguments about anthropogenic landscape
transformations beyond the more striking evidence of landscape engineering will remain as
informed speculation if it is not cross-checked through landscape archaeology and focused
palaeo-ecological research. Once again, my aim here is not to unfairly criticise the work of my
colleagues or diminish my own; instead, it is to suggest that the task of undertaking a
landscape archaeology of the Amazon basin is really only beginning and will require fully
contextualising archaeological sites in their local landscape histories (Heckenberger 2005;
Erickson 2006).
4. LANDSCAPE ARCHAEOLOGY, LANDSCAPES LEGACIES AND LANDSCAPE
DOMESTICATION
Landscape archaeology is in fact a very broad perspective in the discipline of archaeology.
This perspective conceives landscapes as archaeological entities, a formulation that first
implies that landscapes are material entities in which a palimpsest of recognisable features –
monuments, settlements, pathways, field, forests, waterways, etc. – attest to the effects of past
human activities. Since the laste decade (e.g. Gosden 1994; Tilley 1994), however, an
archaeology of the landscape has taken on a different and exciting dimension: modifications to
landscapes resulting from human activities have been understood as part of the ‘moving
target’, i.e. human-induced changes to inhabited worlds have been recognised as shaping the
trajectories of subsequent human communities. In many ways, this has raised awareness about
the research of other archaeologists developing landscape histories (Butzer 1982; Bray et al.
1987; Bell and Walker 1992; Waters 1992; Rapp and Hill 1998) and rendered entities such as
anthropogenic soils (Sandor 1992; French 2003; Davidson and Simpson 2005) into important
aspects of the archaeological record.
In the archaeology of the Americas, a similar set of propositions are most clearly
associated with the perspective of Historical Ecology (Posey 1984; Balée 1989; Crumley
1994; Stahl 1996; Balée 1998, 2006; Balée and Erickson 2006). This perspective advances the
argument that not only conspicuous human-built landscape features such as monuments,
fields, terraces, roads, and the like played a similar dual role – as ‘accreting’ palimpsests and
as ‘constraining’ frameworks – in the development of pre-Columbian societies, but also that
the make-up and interrelations between biotic components in the landscape were both
Chapter 6. Synthesis 178
modified by the effects of human livelihoods and helped to shape broader historical
trajectories of human inhabitation (Stahl 1996; Balée and Erickson 2006; Erickson 2006).
Following these insights, this dissertation has focused on a dramatic example of past human
modification of the landscape, anthropogenic soils of the Amazon basin. It has clearly
recognised the archaeological dimension of these soils and elaborated the argument that as
entities they are ancient, have been key to the cultivation of allochtonous domesticates,
evidence forms of sedentism, and have been important for the intensification of crops.
Knowledge about the enhanced carbon, nutrient status and low pH of anthropogenic dark
earths, coupled with evidence for their widespread use for cultivation in the last two centuries,
highlights the important legacy value of these soils in the Amazonian landscape. Whilst the
systematic archaeological interrogation of this legacy character is still in its infancy, it can
already point to intriguing insights. On the one hand, patterns of aggregation and locale
reutilisation along the middle and lower Amazon most likely are not only related to strategic
control of waterways and access to fish concentrations but also embody the kind of attractor
dynamic that Carneiro (1970) discussed now almost 40 years ago: landscape legacies such as
anthropogenic dark earths must have constituted contested areas around which hierarchical
social relations formed and took shape (Arroyo-Kalin 2006). On the other, the fact that the
geographical distribution of high-yielding varieties of peach palm (Bactris gasipaes), the best
example of a domesticated palm tree in the Amazon basin (Clement 1995), is centred on
regions along the Amazon river where ethnohistorical and archaeological research suggest the
existence of large settlements with anthropogenic dark earths (Hemming 1978; Porro 1996a;
Heckenberger et al. 1999; Neves 2008), i.e. far from a potential domestication hearth (Clement
et al. 2002; Rodrigues et al. 2004), suggests that Bactris sp. varietal differences may well be
an outcome of higher population densities in the late Holocene.
These observations are not only intriguing but also conclusively undermine a basic
premise of Meggers’ (1954) influential understanding of Amazonia as a Counterfeit Paradise
(Meggers 1971; 1995; 2001b; 2001a): that the specific affordances of particular environments
in the Amazon basin could not be enduringly modified by past livelihoods. At the same time,
they emphasise that the human shaping of environmental affordances cannot be understood
simply as a cultural imprint onto the materiality of landscapes (Balée and Erickson 2006):
human niche-building (Laland et al. 2000) has implied the continued reproduction of
symbiotic relations with other species in spatially-heterogeneous and path-dependant ways:
crops have been domesticated in one place and intensified at others; modifications resulting
from inhabitation in one place have become the highly-sought cultivation grounds for later
day agriculture; and yesterday’s abandoned settlements have become loci for higher
concentrations of edible plant taxa. In other words, whilst the effects of ‘culture’ and ‘power’
Chapter 6. Synthesis 179
cannot be denied and must instead be affirmed, it must be concluded that human modifications
of the landscape take place in trans-generational and discontinuous fashion, i.e. over time
scales which need to be examined within broader and ongoing processes of landscape
evolution.
What we commonly gloss as plant and animal domestication – the localization and
intensification of symbiotic relations with other species leading to morpho-genetic changes –
is one of the most important factors inducing emergent trajectories of landscape evolution
during the Holocene. Reciprocally, domestication processes and other mutualistic relations are
recurrent inter-specific dynamics that take place within, indeed depend on, the affordances of
specific yet changing environs – landscapes that were inhabited and modified by human
communities in particular ways. Recent scholarship has placed an increasing emphasis on the
notion of domesticated landscapes and/or landscape domestication. Positions vary from
expanding the domus to encompass the landscape (Terrell et al. 2003; Erickson 2006) to
pinpointing events of conscious and directed human intervention aimed at intensifying yields
from plant or animal taxa, domesticated or not (Clement 1999a; Erickson 2000). These views
differ in the importance accorded to irreversible morpho-genetic change as evidence for
domestication yet share a common understanding that the reproduction of symbiotic
relationships between human and other species did not occur in a vacuum and instead relied
on the modification of the landscape by human communities (see also Piperno and Pearsall
1998; Pearsall 2007). Taking my cue from these premises and thinking about the Neotropical
lowlands, I will argue in closing that documenting historical relationships between
domesticates and enduring landscape transformations will enrich our discussions about the
when-and-where of domestication processes in Amazonia by showing how long ago the
domestication of Amazonia as a landscape truly began.
180
GLOSSARY
A horizon: a soil horizon formed immediately below the soil surface or under an O
horizon. By definition, the better part of organic matter in an A horizon has undergone
humification.
AB horizon: a soil horizon whose characteristics reflect mixing of sediments from the
overlying A horizon and underlying B horizon, but which is more like an A than a B (a BA
horizon is the opposite). See also B/A horizon.
Ab: a buried A horizon.
Acrisol: an FAO soil group describing strongly-leached, iron-rich red and yellow soils
that are formed on weathered clays derived from acid parent material. Acrisols are
characterised by an accumulation of low activity clays in an illuvial horizon, low cation
exchange capacity, and low base saturation. They are related taxonomically to the order of
Ultisols in US Soil Taxonomy.
Adsorption: the process by which atoms, molecules, or ions are taken up from the soil
solution or soil atmosphere and retained on the surfaces of solids by chemical or physical
binding.
Aeolian: windblown.
Aerobic: conditions in which oxygen is present, among others permitting oxidation.
Aggregate: a group of primary soil particles that cohere to each other more strongly than
to other surrounding particles.
Albedo: the proportion of the solar light incident on the Earth (clouds, seas, vegetations,
denuded terrain, etc) that is reflected back from it without heating the receiving surface.
Alluvium: sediments deposited by running water of streams and rivers.
Amorphous organic matter: organic matter with no recognizable vegetal or fungal
structures. See Monomorphic and Polymorphic amorphous organic matter.
Anthropogenic landscape transformations: the shaping of biotic and abiotic legacies
that takes place at the intersection between the cumulative effects of human action, often over
trans-generational time scales, and broader processes of landscape evolution.
Anthropogenic soils: soils whose formation and characteristics have been enduringly
influenced by the material effects of human action. Used synonymously with anthrosols.
Anthrosols: see Anthropogenic soils.
Glossary 181
Ap horizon: an A horizon which shows tillage or another disturbance of agricultural
origin.
Archean: a subdivision of the Precambrian lasting from 4000 to 2500 million years ago.
Autogenic: change in a system caused by endogenous factors.
B horizon: mineral horizon formed below an A, E, or O horizon.
B/A horizon: a horizon comprising distinct volumes of B horizon and A horizon
sediments in which the former are dominant. A B/A horizon is the opposite. See also AB
horizon.
Base saturation: the ratio of the quantity of exchangeable bases to the cation exchange
capacity.
b-fabric or Birefringence fabric: the numerical difference between the highest and
lowest refractive index of a mineral. In thin sections observed under cross-polarised light,
birefringent clay will exhibit characteristic patterns of orientation and distribution of
interference colours.
Bh horizon: a B horizon showing illuvial accumulations of organic matter.
Biomass: the total mass of living organisms in a given medium (water, a volume of soil,
etc).
Black carbon: principally pyrogenic carbon, i.e. charcoal.
Blocky peds: subangular peds approximately shaped as blocks, often with accommodating
faces
Bt horizon: a B horizon characterised by the accumulation of silicate clay.
Budares: flat platters used to make manioc farinha. See comales.
C/f related distribution: a description of the spatial arrangement of coarse and fine
particles in thin section. In the case of soils with grain-supported sediments, c/f related
distributions provide useful concepts to describe microstructure.
Caatinga: an open forest type that is characteristic of Amazonian sandy soils.
Capoeira: successional vegetation. Young capoeira is usually successional regrowth
during fallows or following abandonment of gardens. Older capoeira is successional growth at
locales which have been abandoned for a longer time.
Caraipé: organic temper made by burning the bark of the Licania octandra tree.
Catena: see toposequence.
Glossary 182
Cation exchange capacity (CEC): the sum of exchangeable bases plus total soil acidity at
a specific pH values, usually 7.0 or 8.0.
Cauxí: silica bodies of aquatic sponge spicules that are used as temper in some
Amazonian pre-Columbian pottery.
Cenozoic: geological era starting 65 million years before the present. It comprises the
Tertiary and Quaternary.
Chambers: smooth-walled pores interconnected by channels. Sometimes they can be
interpreted as non-infilled root paths.
Channels: in geomorphology, used to refer to the course along which a river runs through
the landscape. In micromorphology, tubular smooth voids with a cylindrical or arched cross
section which are uniform over much of the length. Sometimes they can be interpreted as non-
infilled worm burrows.
Chelates: organic chemicals with two or more functional groups bound with metals to
form a ring structure. Soil organic mater can form chelate structures with some metals,
especially transition metals.
Chelation: A reversible binding process between a metal ion (chelate) and another
substance know as the ligand. The ligand is often an organic molecule.
Cheluviation: down profile movement of soluble complexes (chelates) of metals such as
Fe, Al and Mg and organic acids.
Chemical weathering: atomic- and/or molecular-level break-down and re-forming of
rocks and mineral that often results in smaller particle sizes. Among others it includes
solution, hydration, oxidation and reduction.
Clay coatings: films of typically laminated oriented clays on the surfaces of peds, mineral
grains and lining pores. Characteristic of illuvial horizons.
Clay fraction: is the fraction of sediments <2 µm. Statements about the clay fraction in
the geoarchaeological study are based on micromorphological observations of the fine mineral
fraction.
Clay: particles <2 µm, irrespective of origin or presumed mode of transport.
Coalescence, of aggregates: conjoining of individual faecal pellets to form aggregates.
Coarse monic c/f related distribution: a grain-supported microstructure in which hardly
any evidence for clay aggregates can be observed.
Colluviation: build-up associated with the decomposition of the earth’s surface.
Comales: flat platters used to make maize tortillas, see also budares.
Glossary 183
Compaction: the process by which soil constituents are rearranged to decrease void space
and bring them into closer contact with one another, thereby increasing the bulk density.
Craton: an area of the Earth’s crust no longer affected by orogeny.
Crumb microstructure: a soil microstructure dominated by the presence of crumbs.
Crumbs: spherical microscopic peds that are porous at the microscopic level.
Deferralitization, of soils: selective dissolution of iron chelates as a result of
cheluviation, leading to a collapse of the argillo-ferric structure of the clay fraction of the soil.
Deflation: sorting, remobilisation and/or removal of loose, dry, fine-grained soil particles
by wind.
Deflocculant: a solution that helps deflocculation.
Deflocculation: Dispersal of soil colloidal particles. The inverse of flocculation.
Dehydration: Loss of adsorbed water molecules on heating.
Desiccation, of soils: an excessive loss of moisture; the process of drying up. Desiccation
can result in shrinkage due to water loss.
Dissection: fluvial erosion of a land surface or landform.
Disturbance: events altering the structure of populations, communities and/or ecosystems.
Down-mixing: observations of faunal and root mixing in which sediments from higher in
the profile can be ascertained to mix with sediments lower in the profile. See up-mixing.
Dusty illuvial clay coatings: illuvial clay coatings in which very small 1-3 µm
particulates can be resolved.
E horizon: mineral horizon with eluvial loss of silicate, clay, iron, and/or aluminium.
Electrical conductivity, of soil: measurement of total solute contents in a soil solution.
Eluviation: the removal of soil material in suspension, e.g. clay particles, from one
horizon to another.
Enaulic c/f related distribution: one type of grain-supported microstructure
characterized by the presence of intergrain aggregates of clayey material.
Erosion pavement: surface of coarse materials and lacking fine materials resulting from
the removal of fines by running water on land surfaces.
Etchplanation: a cycle of chemical erosion resulting in a continuous lowering of the land
surface that exposes the saprolite upon which soils are formed.
Glossary 184
Evapotranspiration: the combined loss of water from a given area, and during a specified
period of time, by evaporation from the soil surface and by transpiration from plants.
Fabric, of soil: soil constituents and their spatial organisation.
Faecal pellets: rounded and subrounded aggregates of faecal material produced by the soil
fauna.
Falésias: discontinuous and abrupt cliffs resulting from lateral erosion of the terra firme
by large rivers.
FAO soil group: one of 30 reference soil groups used as the second highest taxonomic
level in the FAO system. The 30 groups are aggregated into 10 soil group sets that first
distinguish organic soils from mineral soils and then sort all mineral soils into nine broad
categories. Examples of FAO soil groups are Acrisol, Ferralsol, and Spodosols.
Farinha: flour made from bitter manioc tubers.
Ferralic horizon: strongly weathered horizon in which the clay fraction is dominated by
low activity clays and the sand fraction by resistant materials such as iron-, aluminium-,
manganese- and titanium oxides. This type of horizon is similar to the US Soil Taxonomy
Oxic horizon.
Ferralsol: an FAO soil group describing deeply weathered red or yellow soils with diffuse
horizon boundaries, low activity clays (mainly kaolinite), high contents of sesquioxides, and a
ferralic horizon within 170 m of the soil surface. The soil group is similar to the Oxisol order
of the US Soil Taxonomy.
Fine mineral fraction: is the fraction of sediments <2 µm observed in thin section. It is
used with exactly the same sense as the concept of micromass.
Fines: clay and fine silt component of a sediment or soil.
Flocculation: the coagulation of colloidal soil particles due to the ions in solution. In most
soils, the clays and humic substances remain flocculated due to the presence of doubly and
triply charged cations.
Floodplain: the nearly level plain aggraded by rivers when flood-stage conditions lead to
deposition of water borne sediments. See várzea.
Fragipan: a relatively impermeable subsurface horizon with very low organic matter and
redoximorphic features showing hard, seemingly cemented consistence.
Friagens: annually rare, 1-2 day-long spells of cold conditions in the Amazon basin
resulting from the northward advance of southerly cold fronts. Temperatures drop to about 17°
C.
Glossary 185
Gallery forests: linear arboreal expanses that flank rivers running though savannah
regions.
Geogenic: originating in earth-surface processes; not anthropogenic.
Goethite: a yellow-brown iron oxide mineral. Goethite occurs in almost every soil type
and climatic region and is responsible for the yellowish-brown colour of many soils and
weathered materials.
Grain-supported: sediments in which the mineral particulates constitute the skeleton and
clayey material forms smaller aggregates attached to particulates.
Grano-oriented braces: small zones of clayey material around grains.
Granular microstructure: arrangement of granules separated by non-accommodating
packing voids. Synonymous with granular fabric.
Granules: spherical microscopic peds that are not porous at the microscopic level.
Hematite: a red iron oxide mineral that contributes to the red colour of many soils. See
also rubification.
Holocene: the second of two epochs of the Quaternary, starting around 10,000 years ago.
Horizon, of soil: a layer of soil or soil material approximately parallel to the land surface
and differing from adjacent, genetically-related layers in physical, chemical, and biological
properties and characteristics such as colour, structure, texture consistency, kinds and number
of organisms present, degree of acidity or alkalinity, etc. See also horizonation.
Horizonation: depth-wise differentiation of sediments from the atmosphere to the
regolith.
Humic compounds: dark-coloured organic material that can be extracted from soil with
dilute alkali and other reagents and that is precipitated by acidification to pH 1 to 2.
Humification: the process whereby the carbon of organic residues is transformed and
converted to humic substances through biochemical and abiotic processes.
Humus: stable, well-decomposed, organic matter in mineral soils.
Hydrarch succession: ecological succession resulting from hydrological changes in a wet
habitat.
Hydration: combination of water and another substance that often results in expansion
and produces clays and minerals.
Igapó: endemic forests that are flooded during a substantial part of the year.
Igarapé: the small rain-fed streams that dissect the terra firme in Amazonia.
Glossary 186
Illuvial horizon: a horizon formed by illuviation.
Illuviation: the deposition of soil material from an overlying horizon, especially removed
through eluviation.
Inclusions: particulates not inherited from the parent material.
Infrared absorption spectroscopy: a technique that compares the intensity of an infrared
beam of light before and after interaction with a sample.
Interference colours: optical phenomenon resulting from different wave lengths of
polychromatic light passing through an analyser; it depends on mineral orientation, thickness
and birefringence (see b-fabric).
Interfluve: in Amazonian scholarship it refers to the terra firme between major
waterways, away from the river front.
Intergrain: located in the interstitial pore space between grains.
Interpedal: located in the interstitial space between peds.
Intra-cratonic basin: ancient basin developed when rifting between two faults ceased.
Intrapedal: within a ped.
Ipadú: a mild stimulant made out of powdered leaves of Erythroxylum coca var. ipadu
mixed with an alkaline substance such as ash.
Kaolinite: group of clay mineral belonging to the 1:1 groups of phyllosilicates. Kaolinite
represents the final product from the chemical weathering of feldspars to clay.
Krotovinas: infilled burrows of soil fauna.
Landform: physical, recognizable form or feature on the earth’s surface.
Landscape: evolving networks of biotic and abiotic components characterised by self-
organisation, spatially-divergent dynamics, and complex path-dependence. Biotic components
include human communities in their social and ecological matrix; these communities play a
pivotal role in shaping particular landscapes by acting as focal points for symbiotic relations
with other species in spatially-heterogeneous and path-dependant ways.
Landscape evolution: path-dependant landscape change.
Late Glacial Maximum (LGM): coldest moment of the last glacial period dated around
22,000 to 18,000 years ago.
Laterite: weathering product of rock composed mainly of hydrated iron and aluminium
oxides and hydroxides, and clay minerals, but also containing some silica. It can form as result
Glossary 187
of the weathering of basalts. In the Negro-Solimões confluence area it is known as Pedra
Jacaré.
Latosol: a Brazilian soil type that includes soils formed under forested, tropical, humid
conditions. Latosols are equivalent to Oxisols or Ferralsols.
Lattice: a regular three-dimensional geometric arrangement used to represent the
distribution of repeating atoms or groups of atoms in a crystalline substance.
Leaching: the removal of soil material in solution, e.g. dissolved Ca, from one horizon to
another.
Limpid clay: uniform fine clay lacking fine particulate inclusions and unstained by
amorphous organic matter.
Loss-on-Ignition: a procedure to infer total carbon and organic carbon by measuring
weight loss of sediments subjected to high temperatures in a muffle furnace.
Maar: crater produced by an explosive volcanic eruption.
Maghemite: a dark reddish-brown, magnetic iron oxide mineral chemically similar to
hematite, but structurally similar to magnetite. It can form rapidly though burning or slowly as
a result of transformations by reduction-oxidation cycles.
Magnetic susceptibility: degree of magnetization of a material in response to an applied
magnetic field.
Magnetite: a black, magnetic iron oxide mineral usually inherited from igneous rocks. It
can form rapidly though burning or slowly as a result of transformations by reduction-
oxidation cycles
Malocas: ethnographic longhouses.
Manganese oxides: a group term for oxides of manganese. They are typically black and
frequently occur in soils as nodules and coatings on ped surfaces, usually in association with
iron oxides.
Manos: grinding stones.
Massive: lacking internal structure or stratification and homogeneous in composition. In
micromorphology often used to refer to homogenous fabrics lacking porosity.
Matrix-supported: sediments in which mineral particulates are embedded within the
clayey fraction.
Melanisation: The darkening of a topsoil by incorporation of humus or other pigmenting
substances such as sesquioxides and charcoal.
Glossary 188
Metal: an element that readily loses electrons to form positive ions (cations) and forms
metallic bonds between other metal atoms.
Micromass: a term in soil micromorphology used to describe generally crystalline and/or
amorphous clay minerals, often combined with Fe (hydr)oxides and amorphous organic
matter, whose constituent units cannot be resolved with the optical microscope.
Microstructure: a concept used to describe the size, shape, and arrangement of inherited
particles, aggregates and voids in soils.
Miocene: an epoch of the Tertiary period extending from the end of the Oligocene (23.3
million years ago) to the beginning of the Pliocene (5.2 million years ago). Mammals with a
modern appearance evolved during this period.
Monomorphic amorphous organic matter: amorphous organic matter with no
recognizable vegetal or fungal structures but showing uniform colloidal texture.
Montaña: name given to the eastern piedmont of the Andes as it dips into the Amazonian
lowlands.Also used to describe the westernmost lowlands of Amazonia.
Munsell colour system: a colour designation system that specifies the relative degrees of
hue, value, and chroma.
Neotectonics: geologically-recent tectonics.
Nodule: a cemented concentration of a chemical compound, for instance an iron oxide,
that can be removed from the soil intact.
O horizon: topmost horizon dominated by organic material.
Oligotrophic: environments in which the concentration of nutrients available for growth
is limited. Nutrient-poor habitats.
Organ residues: fragments of plant matter in which at least five interconnected cells of
more than one type of tissue can be observed.
Organics: short-hand for microscopic particles of organic matter.
Organic carbon (Co): the pool of carbon inferred to originate from organic matter, i.e.
not derived from the mineral fraction of the soil. See Total carbon.
Organic punctuations : small dark or opaque generally <1 µm grains made of organic
fine material.
Organic staining: pigmenting of the clay fraction with amorphous organic matter.
Orogeny: mountain building, especially by compressive tectonism.
Glossary 189
Oxbow lake: crescent-shaped body of standing water formed in a river’s abandoned
channel (oxbow).
Oxic horizon: a mineral soil horizon at least 30 cm thick that is characterized by a lack of
weatherable primary minerals or 2:1 layer silicate clays. Instead it is manly composed of 1:1
layer silicate clays, such as kaolinite, and highly insoluble minerals, such as quartz sand. It
constitutes the diagnostic B horizon of an Oxisol. It is similar to an FAO ferralic horizon.
Oxidation: reaction in which an atom loses an electron, e.g. where oxygen combines with,
or hydrogen is removed from, a substance.
Oxisol: US Soil Taxonomy soil order describing mineral soils that show an Oxic horizon
within 200 cm of the soil surface. The order is analogous to the FAO Ferralsol group.
Packing voids: in micromorphological analysis, voids resulting from the loose packing of
soil components, the faces of which do not accommodate. Packing voids often show a high
degree of connectivity.
Palaeo-pedology: the study of ancient soils, including paleosols and exposed soils with
relict features.
Palaeozoic: the first geological era following the Precambrian, lasting from 570 to 248
million years ago. Palaeozoic fauna was characterized by invertebrates such as trilobites and
corals; by the end of the era, tree-ferns and palm-like cycads formed forests while amphibians
and reptiles were major components of different biotic communities.
Paleosol: conceptually, ancient soils; in practice, buried soils. See also Ab horizon.
Parent material: the original material, usually weathered rock, from which a particular
soil profile has formed.
Parkland: savannah in which woody species are observed, often with grassy understories.
Particulates: discrete particles >2 µm that can be resolved microscopically. In the
geoarchaeological study, microscopically-observed particulates include quartz grains,
weathered minerals, charcoal fragments, bone fragments, and aquatic sponge spicules, among
others.
Ped: a unit of soil structure such as a block, column, plate, or prism, formed by natural
processes. In soil micromorphology, spherical peds are also recognised. These are subdivided
into crumbs and granules.
Pedon: a three-dimensional body of soil with lateral dimensions large enough to permit
the study of horizon shapes and relations.
Glossary 190
Peneplain: an extensive area of low relief formed by peneplanation. They are dominated
by convex hill slopes, mantled by contiguous regolith, and dissected by wide, shallow river
valleys.
Peneplanation: a cycle of physical erosion resulting in a peneplain.
Phyllosilicates: group of silicate minerals characterized by layers of [SiO4]4- that share
three oxygens. They form a flat sheet with the composition [Si4O10]n.
Phytostabilisation: terrain in which erosion is prevented as a result of arboreal vegetation.
Planar voids: a type of elongated microscopic void that is often interpreted as evidence of
shrinkage or slipping and, under certain circumstances, may be used to infer trampling.
Plant tissue: fragments of plant matter in which at least five interconnected cells of a
single type of tissue can be observed.
Pleistocene: the first of the two epochs of the Quaternary, starting around 1.8 million
years ago and lasting until the beginning of the Holocene about 10,000 years ago.
Pliocene: the last epoch of the Tertiary, lasting from 5.2 to 1.64 million years ago.
Podzol: an FAO soil group which describes soils with an ash-grey subsurface horizon,
bleached by organic acids, on top of a dark Spodic horizon with brown, black or reddish
illuviated humus and/or iron compounds.
Podzolization: a process of soil formation resulting in the genesis of Podzols.
Polymorphic amorphous organic matter: amorphous organic matter forming a
discontinuous mass of polymorphic elements of different colour and density, without
recognizable vegetal or fungal structures.
Porosity: the proportion of a known volume of soil occupied by soil pores. In soil
micromorphology it represents the surface area of a soil micromorphological thin section not
occupied by solid soil material.
Porphyric c/f related distribution: used synonymously with matrix-supported.
Precambrian: the geological period spanning from the consolidation of the Earth’s crust
to 570 million years ago.
Pseudo-sand: strongly bound sand-sized aggregate particles composed of silt- and clay-
sized constituents.
Pseudo-silt: strongly bound silt-sized aggregate particles composed of clay-sized
constituents.
Pyrogenic carbon: charcoal; see also black carbon.
Glossary 191
Quartz: a framework silicate composed exclusively of silica tetrahedra. It is the most
common type of mineral silt- to sand-sized particle observed in Oxisols of the central Amazon
region.
Quaternary: the sub-era of the Cenozoic era that covers the last 1.8 million years. It
comprises the Pleistocene and Holocene epochs.
Reduction: reaction in which an atom gains an electron, e.g. where oxygen is removed
from, or hydrogen combines with, a substance.
Regolith: layer of unconsolidated weathered material that rests on unaltered, solid
bedrock.
Regressive erosion: etchplanation as a result of chemical weathering.
Rias: small terra firme streams turned into alluvial lakes as a result of sediment
accumulation at their now sunken discharge points.
Rift-Valley: elongated trough of regional extent bounded by two or more faults. When
infilled with sediments it is known as a graben (German for ditch).
Rubification: the process of heating to redness, transforming goethite/ hematite into
maghemite.
Sand: particles >60 µm and smaller than 2000 µm, irrespective of origin or presumed
mode of transport..
Saprolite: in situ chemically-rotten rock, often the lower part of the vertical section from
the surface to unaltered bedrock.
Savannah: flat grasslands in tropical regions, also known as cerrado.
Seed bank: dormant but viable seeds in the soil that will germinate if specific conditions
ensue.
Sediment: any particulate matter derived from pre-existing rock, from biogenic sources,
or precipitated by chemical processes, that has been deposited by some process at or near
Earth’s surface.
Separation, degree of: the extent to which soil material observed in thin section is
divided into units tending towards microscopic peds.
Sesquioxides: oxides containing three oxygen atoms for every two metal atoms of another
substance. Typically used for iron oxides and hydroxides but also applicable to manganese
oxides.
Silica phytoliths: silica bodies formed in plant matter as a result of the uptake of silica.
Glossary 192
Silicate minerals: rock minerals characterized by different structural arrangements of
SiO4.
Silt: particles between 2 and 60 µm, irrespective of origin or presumed mode of transport.
Soil fauna: includes mesofauna (nematodes, oligochaete worms, smaller insect larvae, and
micro arthropods) and microfauna (protozoa, nematodes, and arthropods of microscopic size).
Soil nutrient status: concentrations of soil nutrient in chemical forms accessible to plant
roots or in compounds likely to be convertible to such forms.
Soil nutrients: elements absorbed by plants that are necessary for completion of the
normal life cycle. They include macronutrients (found in relatively large amounts in plants,
typically N, P, K, as well as Ca, Mg and S) and micronutrients (found in relatively small
amounts in plants, typically B, Cl, Cu, Fe, Mn, Mo, Ni, Co, and Zn).
Soil order: the highest taxonomic level employed by US Soil Taxonomy.
Soil organic matter: The organic fraction of the soil exclusive of undecayed plant and
animal residues.
Soil pH: the pH of a solution in equilibrium with soil.
Soil pores: the part of the bulk volume of soil not occupied by soil particles. In
micromorphology porosity is the surface area of void space observed in thin section.
Soil profile: a vertical section through all the constituent horizons of a soil, from the
surface to relatively unaltered parent material. In the geoarchaeological study, the depth of soil
profiles is limited by archaeological excavations and thus rarely reaches below the upper
decimetres of the B horizon.
Soil texture: relative proportions in a soil of the various soil separates categorized by size.
Typical size classes include clay (<2 µm), silt (2-60 µm), sand (60 – 2000 µm). Subclasses are
defined in the Conventions section (page xiv).
Soil: organic or lithic material at the surface of planets and similar bodies altered by
biological, chemical, and/or physical agents. Soil is weathered regolith that contains organic
material and can support rooted plants.
Solution: detachment of weakly bonded ionic components of minerals through the
attraction of water molecules.
Sonication: application of ultrasound energy to agitate particles in a sample in order to
assist deflocculation prior to measurements, especially of particle size distribution.
Sorption: the removal of an ion or molecule from solution by adsorption and absorption.
It is often used when the exact nature of the mechanism of removal is not known.
Glossary 193
Speckled b-fabric: randomly arranged, equidimensional domains of oriented clay smaller
than the fabric units.
Spodic horizon: diagnostic horizon of a Spodosol/Podzol in which organic matter,
aluminium and often iron compounds are understood to have accumulated in amorphous form.
Spodosol: A US Soil Taxonomy order describing mineral soils with a spodic horizon.
Spodosols are equivalent to Podzols.
Stone line: a sheet-like concentration of coarse fragments under the soil surface. It can be
formed by gravitational sinking of material as a result of soil faunal activity or by burial of an
erosion pavement.
Strial b-fabric: under XPL the fine mineral fraction as a whole exhibits a preferred
parallel orientation. Characteristic of B horizon sediments.
Striated b-fabric: under XPL elongated zones or streaks of oriented clay with more or
less simultaneous extinction are observed. Common in soils subject to shrink and swell.
Succession: replacement of one ecological community by another over time.
Tecomate: a Mesoamerican term used to describe globular-shaped ceramic vessels.
Tectonism: deformation within the Earth’s crust and its consequent structural effects.
Terra firme: terrain in the Amazon basin that is not affected by flooding.
Terras mulatas: anthrosols less chemically-enhanced than terras pretas which are
interpreted as former agricultural outfields.
Terras pretas: circumscribed expanses of dark-coloured and chemically-enhanced soils
that signal the location of densely-occupied late pre-Columbian settlements in the Amazon
basin.
Tertiary: first sub-era of the Cenozoic era which began 65 million years ago and lasted
until 1.64 million years ago.
Toposequence: a sequence of related soils that differ, one from the other, primarily
because of topography as a soil-formation factor. Also know as Catena.
Total carbon (Ct): the total pool of carbon in a sediment or soil. See also Organic carbon.
Translocation: the transport of material within a soil, in suspension, solution, or as a
result of burrowing or digging.
Truncation: a boundary between sedimentary units that cuts across bedding planes; often
indicates erosion.
Glossary 194
Ultisol: a soil order in US Soil Taxonomy describing soils with an argillic horizon with
less than 35% base saturation. Ultisols can form as a result of regressive erosion of Oxisols.
They are related taxonomically to the FAO World Reference Base Acrisols soil group.
Unaccommodated: applied to peds. Virtually none of the faces of adjoining peds are
moulds of each other.
Unconformity: A substantial break or gap in sedimentary build-up, often overlain by
sediments showing different composition, texture, or sorting. See also Truncation.
Undifferentiated b-fabric: absence of interference colours of the clayey fraction when
observed under XPL, sometimes due to masking by oxides and/or organic matter.
Up-mixing: observations of faunal or root mixing in which sediments from lower in the
profile can be ascertained to mix with sediments higher in the profile. See faunal down-
mixing.
Várzea: the extensive floodplain graded by rivers carrying Andean sediments in the
Amazon basin.
Vesicles: relatively large voids whose wall consist of smooth, simple curves. Often
interpreted as air bubbles in near-surface horizons and under puddles.
Voids: discrete pores observed in thin section. They are classified according to their
morphology into packing voids, vesicles, channels, chambers, vughs and planes.
Vughs: relatively large voids, usually irregular and not normally interconnected with other
voids of comparable size. In matrix-supported sediments, vughs sometimes represent
interstitial porosity remaining from the coalescence of aggregates.
Vughy: possessing vughs.
Younger Dryas: post LGM period of sharp climatic change that marks the final millennia
of the Pleistocene.
Sources: Allaby and Allaby 1999; Courty et al. 1989; Daly and Mitchell 2000; Driessen et
al. 2001; French 2003; Soil Survey Staff 2003; Moran 1993; Tricart 1985; Stoops 2003;
Johnson 1998; Thomas 1994; Linne 1957, 1925; Hartt 1879; Singer et al. 1996.
195
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