handheld xrf - neff voorhies paredes umana-def-1

Handheld XRF for Art and Archaeology

Isotopes_SIAS_19-11-2012.indd 1 29/11/12 14:38

Studies in Archaeological Sciences 3

The series Studies in Archaeological Sciences presents state-of-the-art methodological,

technical or material science contributions to Archaeological Sciences. The series aims to

reconstruct the integrated story of human and material culture through time and testifies

to the necessity of inter- and multidisciplinary research in cultural heritage studies.

Editor-in-Chief

Prof. Patrick Degryse, Centre for Archaeological Sciences, KU Leuven, Belgium

Editorial Board

Prof. Ian Freestone, Cardi! Department of Archaeology, Cardi! University, United Kingdom

Prof. Carl Knappett, Department of Art, University of Toronto, Canada

Dr. Andrew Shortland, Centre for Archaeological and Forensic Analysis, Cranfield University, United Kingdom

Prof. Manuel Sintubin, Department of Earth & Environmental Sciences, KU Leuven, Belgium

Prof. Marc Waelkens, Centre for Archaeological Sciences, KU Leuven, Belgium


Handheld XRF for Art and Archaeology

Edited by

Aaron N. ShugarJennifer L. Mass

Leuven University Press


© 2012 by Leuven University Press / Presses Universitaires de Louvain / Universitaire Pers Leuven. Minderbroedersstraat 4, B-3000 Leuven (Belgium).

All rights reserved. Except in those cases expressly determined by law, no part of this publication may be multiplied, saved in an automated datafile or made public in any way whatsoever without the express prior written consent of the publishers.

ISBN hardcover 978 90 5867 907 9ISBN paperback 978 90 5867 934 5

D / 2012 / 1869 / 54NUR: 682/950

Lay-out: Friedemann BVBA (Hasselt)Cover: Jurgen Leemans


7

List of illustrations 9

List of tables 15

Chapter 1IntroductionAaron N. Shugar and Jennifer L. Mass 17

Chapter 2

Dylan Smith 37

Chapter 3

Dusan C. Stulik and Art Kaplan 75

Chapter 4

Chris McGlinchey 131

Chapter 5

K. Trentelman, C. Schmidt Patterson and N. Turner 159

Chapter 6

Tim Barrett, Robert Shannon, Jennifer Wade and Joseph Lang 191

Chapter 7

Jennifer Mass and Catherine Matsen 215

Chapter 8

Anikó Bezur and Francesca Casadio 249

Chapter 9

Aaron N. Shugar and P. Jane Sirois 313

Table of Contents


8

Chapter 10

Mary Kate Donais and David George 349

Chapter 11

Hector Ne!, Barbara Voorhies and Federico Paredes Umaña 379

Chapter 12

Je!rey R. Ferguson 401

Chapter 13

Jim J. Aimers, Dori J. Farthing and Aaron N. Shugar 423

Chapter 14

Bruce Kaiser and Aaron Shugar 449

List of contributors 471

The editors 473


Handheld XRF elemental analysis of archaeological sediments:

some examples from Mesoamerica Hector Ne! , Barbara Voorhies and Federico Paredes Umaña

Introduction

The highly portable, durable handheld XRF instruments that have appeared on the market over the past few years hold tremendous potential for archaeology.

sediments in situ. The present paper focuses on sediment analysis, which is useful et al.

Wells et al.Traditionally, archaeologists have described sediments according to color,

texture, moisture content, and other visual clues, usually in qualitative terms, and

objectivity is introduced by keys, such as the Munsell soil color chart, which is as

such as color, however, vary depending on composition, sediment history, organic content, moisture content, and other conditions, not to mention the eyesight and expertise of the observer. The advent not only of handheld XRF but of other kinds

much of the subjectivity and guesswork out of archaeologists’ interpretations of ancient sediments, as the examples to be discussed here illustrate.

The two examples to be discussed here are from excavations in southern

The goal in this case is to test hypotheses about what activities might have been

Handheld XRF elemental analysis of archaeological sediments:

some examples from Mesoamerica Hector Ne! , Barbara Voorhies and Federico Paredes Umaña

Chapter 11

Hector Ne!, Barbara Voorhies and Federico Paredes Umaña380

the XRF analysis.

In this case, the goal is to identify the source of a volcanic ash layer found at approximately two meters depth at most locations across the site and to understand the depositional processes that mixed the volcanic ash up or down within the

could have been conducted in situ, with the handheld XRF instrument either mounted on a tripod or held by hand, but it turned out in

Methods

prior to every analysis, The second study thus quite closely approximates what would be obtained by handheld XRF of in situ sediments.

Handheld XRF elemental analysis of archaeological sediments 381

and thorium were measured on the second analysis.

Food processing at Tlacuachero, Chiapas, Mexico

of bedded remains dominated by a single species of marsh clam, Polymesoda radiata

In an effort to understand what activities might have been carried out on the

off before new deposits of shell began to accumulate above it. The excavation


Figure 11.1: Map of features on the excavated portion of the Tlacuachero "oor. Small circles are #nger molds; larger #lled circles are post molds; irregular shapes are rock depressions.

varied in relation to the visible features. In particular, the hypothesis that plants

mapping variability in the concentrations of biologically important elements, such

and other trace elements are involved in a variety of metabolic pathways and

et al.seven greater speed of analysis and the ability simultaneously to determine a range of biologically important elements in addition to phosphorus.

In order to evaluate the impact that particular biological tissues might have on

included as a background reference sample.


phosphorus, both of which are far higher than the surrounding mangrove mud

is far higher than expected in shell, which provides a preliminary indication that

collected on this project, resembles the bulk chemistry of bone, which is mostly

interpretation is that it represents in situ formation of hydroxyapatite from the

their phosphates.

Figure 11.2: XRF spectrum from bone overlain on one of the Tlacuachero "oor samples. Spectrum was taken with accelerating voltage of 15 kV and 15 $A beam current, with no #lter and with the detector chamber evacuated.

In many traditional analytical methods of soil analysis one would expect to

calibration to be undertaken, but in many cases, the question being asked can be altered slightly so that raw data can be used and calibration is not necessary.


elements using a series of clay reference materials mixed with bone ash in varying proportions.

Figure 11.3: Biplot derived from principal components analysis of the correlation matrix of net intensities data for Tlacuachero "oor samples. Analytical data for samples of #sh, shrimp, pozol, shell, and mangrove mud are projected into the PCA space. Vectors connect the origin with coordinates of the variables in order to illustrate patterns of elemental correlation and determinants of the object point scatter (Ne! 1994).


contributes to lower scores. The mangrove mud, being much higher in silicon and

Figure 11.4: Bivariate plot of phosphorus and calcium net intensities in Tlacuachero "oor samples and samples of #sh, shrimp, shell, pozol, and mangrove mud also analyzed by XRF.

samples are in both phosphorus and calcium.


Figure 11.5: Bivariate plot of phosphorus and zinc net intensities in Tlacuachero "oor samples and samples of #sh, shrimp, shell, pozol, and mangrove mud also analyzed by XRF.

variation is plausibly attributed to processing of food, especially seafood tissue.

hydroxyapatite formed in situ from the reaction of shell with organic materials contributed by food processing or other activities. While the possibility that plants,

light on what plants might have been in the environment during the period that the


Figure 11.6: Map of scores on Principal Component 1 across the Tlacuachero "oor. Whites are high values; blacks are low values. Plusses indicate sampling locations.

Figure 11.7: Map of phosphorus/calcium ratios across the Tlacuachero "oor. Whites are high values; blacks are low values. Plusses indicate sampling locations.


elemental indicators of food processing with the distribution of plant microfossil

elemental concentrations that could not be derived from any conceivable mixture of shell, local mud, or plant residues. Thus, the geochemical data accord with the

from marine and estuarine organisms.

Figure 11.8: Map of zinc/calcium ratios across the Tlacuachero "oor. Whites are high values; blacks are low values. Plusses indicate sampling locations.

Geochemical evidence for sedimentary processes at Ataco, El Salvador

et al.

Tierra Blanca Joven


natural or cultural processes account for the different states of preservation of the ash layer?

samples from underneath and above the tephra layer. Two series of samples were from short, bamboo cores driven through the ash layer and into the underlying sediments within excavation units. Two longer stratigraphic sequences from the

proved particularly useful for stratigraphic interpretation.

Figure 11.9: Spectum from a sample of TBJ ash from a road cut near San Salvador overlain on spectrum of ash from tephra layer at Ataco. Spectra were taken with 40 kV accelerating voltage and 15 microamps beam current, with beam #ltered by thin foils of copper (150 $m), aluminum (50 $m) and titanium (300 $m), and no vacuum.


silicon, characteristics that are indicative of incipient formation of clay within the ash layer. In sum, however, there is little doubt that the ash layer encountered in

Figure 11.10: Bivariate plot of rubidium and titanium log concentrations in all sediment samples from Ataco together with TBJ volcanic ash samples from near San Salvador. The ellipse represents 90% con#dence level for membership in the TBJ ash group. Labeled samples are those identi#ed in the #eld relatively unweathered samples of the Ataco ash layer.

longest axis in the data, and so on. The principal components may be more readily interpretable than the raw elemental data, since the redundancy in raw


fairly clear interpretations, as discussed in the following paragraphs.

Figure 11.11: Biplot derived from a principal components analysis of the correlation matrix of logged XRF data for TBJ ash samples and sediments from Ataco. Labeled samples are relatively intact ash samples from Ataco. Ellipse represents 90% con#dence level for the TBJ volcanic ash group.

of phosphorus and vanadium and dilution of several elements, including calcium,


Figure 11.12: Biplot of PC1 and PC3 derived from a principal components analysis of the correlation matrix of logged XRF data for TBJ ash samples and sediments from Ataco. Labeled samples are relatively intact ash samples from Ataco. Ellipse represents 90% con#dence level for the TBJ volcanic ash group.

to the unweathered ash. This observation suggests that barium concentrations in

two sequences taken at regular intervals within excavation units. These sequences provide a means to examine stratigraphic patterning in the XRF elemental data.


Figure 11.13: PC1 scores of sediment samples from Units 4 and 30 plotted against depth from the ground surface.

Figure 11.14: PC2 scores of sediment samples from Units 4 and 30 plotted against depth from the ground surface.


sediments could be a result of erosion of ash from upslope, human disturbance, or other processes that would have mixed ash into soil and sediment layers that were

these observations is that phosphorus, an important plant nutrient, is being taken

Figure 11.15: Phosphorus concentrations in sediment samples from Units 4 and 30 plotted against depth from the ground surface.


Figure 11.16: Phosphorus concentration vs depth below top of core in TBJ-Ref-1. Uppermost 10 cm are relatively intact TBJ ash.

up by the coffee trees and other plants at the surface, but that this impact on soil chemistry declines with depth, so that phosphorus concentration increases. The

where large incensario fragments were found, and it is possible that the enriched phosphorus at this location originates in organic remains discarded along with the

Interestingly the sequence of samples from one of the bamboo cores driven through the volcanic ash layer shows a similar increase in phosphorus content with

detection. This may indicate the extent to which plant growth had depleted soil

from below the ash at this location are highly enriched in aluminum and iron,

surfacing of a public space.


Figure 11.17: PC3 scores in sediment samples from Units 4 and 30 plotted against depth from the ground surface.

Figure 11.18: Barium concentrations in Units 4 and 30 plotted against depth below the ground surface.


Figure 11.19: Barium concentrations in samples from bamboo core #2 (TBJ-Ref-2) plotted against depth from the top of the core.


almost certainly a remnant layer produced originally by the eruption of Ilopango

supported growing plants that were depleting soil phosphorus near the surface,

little phosphorus as to suggest that it may have been an imported construction

such as erosion of ash from mounds and animal and human disturbance, mixed

layer in some locations.

Conclusion

Many characteristics of the archaeological record, often the most informative ones, are invisible to the naked eye and can only be perceived or measured with

laboratory settings, where the requisite analytical instrumentation could be kept in

by a variety of techniques, pollen and phytolith analysis, residue analysis, and

aside after a few cursory observations of color and texture. Only when specialists have been brought in to sample for later laboratory analysis have archaeological

et al. et al. et al.

the cost of analysis by eliminating most sample preparation, eliminating the need for packaging, cataloguing, and transporting samples, and in principle even eliminating the need to take in situanalytical costs, it becomes feasible to subject the sedimentary matrix to the kinds


of analyses usually reserved for fancy pottery, obsidian, metals, and other artifacts encountered during excavation. The examples discussed here are intended to

powdered and packed hydroxyapatite formed by the interaction of calcite from shell and phosphates liberated from food residues and other waste products deposited on the surface. Mapping of biologically important elements across the

deposition activities.

suggested new interpretations of the surfaces on which the ash fell as well as some

of the ash and elemental components of the ash.

been faster and would have generated many more analyses, but at the cost of

portable analytical instruments are deployed on site or near the site, the spread of analytical technology out of the laboratory certainly represents an exciting trend in archaeology, one that promises to have profound effects both on archaeological methods and on understanding of the past over the coming decades.

References

Journal of Archaeological Science

Latin American Antiquity

realm. Latin American AntiquityQuaternary International



Ceramic Production and Circulation in the Greater Southwest: Source Determination by INAA and Complementary Mineralogical Investigations

Journal of Archaeological ScienceJournal of Field Archaeology

The Chantuto People: An Archaic Period Society of the Chiapas Littoral, Mexico

Coastal Collectors in the Holocene: The Chantuto People of Southwest Mexico

Microarchaeology: Beyond the Visible Archaeological Record

data from inductively coupled plasma—optical emission spectroscopy reveals Archaeological

Chemistry: Analytical Techniques and Archaeological Interpretation, edited by M.

Geoarchaeology: An International Journal

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