Mössbauer Study of Ceramic Finds from the Galería de las Ofrendas, Chavín de Huántar

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<ul><li><p>Hyperfine Interactions 150: 5172, 2003. 2003 Kluwer Academic Publishers. Printed in the Netherlands. 51</p><p>Mssbauer Study of Ceramic Finds from theGalera de las Ofrendas, Chavn de Huntar</p><p>L. G. LUMBRERAS1, R. GEBHARD2, W. HUSLER3,F. KAUFFMANN-DOIG4, J. RIEDERER5, G. SIEBEN3 and U. WAGNER31Museo Nacional de Antropologa, Pueblo Libre, Lima 21, Peru2Archologische Staatssammlung Mnchen, Lerchenfeldstrae 2, 80538 Mnchen, Germany3Physik-Department E15, Technische Universitt Mnchen, 85747 Garching, Germany4Universidad Peruana de Cincias Aplicadas (UPC), Lima, Peru5Rathgen-Forschungslabor, Schloss-Str. 1a, 14059 Berlin, Germany</p><p>Abstract. Ceramic finds from the Galera de las Ofrendas at Chavn de Huntar and surface findsfrom the settlement of Chavn were characterised by combining the results of archaeological typol-ogy with archaeometric studies using neutron activation analysis, Mssbauer spectroscopy, X-raydiffraction and thin-section microscopy. Sherds from the pyramid Tello are included in the study asrepresentative of local material. The analyses show that the vessels were made from different rawmaterials and that different firing procedures were used in their production. Sherds of certain styleslargely exhibit similar types of Mssbauer patterns and in many instances also have similar elementcompositions. This supports the archaeological notion that the vessels were brought to Chavn fromthe provinces, perhaps on the occasion of a festivity.</p><p>Key words: Formative ceramics, Galera de las Ofrendas, Chavn de Huntar, Mssbauer spec-troscopy, thin section microscopy, X-ray diffraction.</p><p>1. Introduction</p><p>Chavn de Huntar is a Pre-Columbian ceremonial site in the Andes of northernPeru, at an altitude of 3180 m above sea level at the foot of the Cordillera Blanca.In the precinct of the main temple at Chavn de Huntar, a number of undergroundgalleries were found. During the years 1966 and 1967, when one of these wasexcavated by Lumbreras, about eighteen thousand ceramic sherds were recovered,which could be shown to stem from nearly 700 vessels [1, 2]. Since these wereconsidered as offerings brought to the sanctuary by pilgrims, the gallery was calledthe Galera de las Ofrendas. Although the Galera de las Ofrendas represents aclosed archaeological context, the styles of the ceramics found there differ widelyfrom each other and from those of local ware, which seems to support the notionof offerings brought to Chavn from the surrounding provinces, perhaps on theoccasion of a single festivity. We have studied 70 specimens of ceramic finds fromthe Galera de las Ofrendas by Mssbauer spectroscopy, X-ray diffraction, thin</p></li><li><p>52 L. G. LUMBRERAS ET AL.</p><p>section microscopy and neutron activation analysis. Data from previous studies ofsherds from the Pyramid Tello at Chavn de Huntar [3] and from the settlementof Chavn [46] are referred to for comparison. The rationale behind this inves-tigation is to learn if vessels of different archaeological styles also have differentmaterial properties. This would confirm the notion that they were made of clayfrom different locations and brought from there to Chavn, rather than being madelocally.</p><p>The archaeological classification divides the samples from the Galera de lasOfrendas into different styles with names such as Wacheqsa, Floral or Puksha [1].In order to uniquely describe the individual sherds studied in this work, they wereadditionally given numbers in the database we maintain at our Garching laboratory(GarNum, e.g., 13/73). In the following, the sherds will be designated by theseGarNums and, in addition, by the archaeological style name.</p><p>2. Neutron activation analysis</p><p>Neutron activation analysis (NAA) [7] was used to determine the concentrationsof 18 trace and 3 major elements in 64 finds from the Galera de las Ofrendas.Previously 53 surface finds from the settlement of Chavn and 61 sherds from thePyramid Tello were studied [46] and can be used together with the present data.The dendrogram obtained by a cluster analysis of the element concentrations forthe finds from the Galera using the average weighted linkage method (Figure 1,left) has been interpreted in terms of eight groups, though any such subdivision isto some extent arbitrary. However, notwithstanding the chosen partition, ceramicsof certain archaeological styles should be found close together in the dendrogramif they came from the same place or even workshop.</p><p>The archaeological classification distinguishes [1] between local Chavn ceram-ics and other styles, namely Mosna, Puca Orqo, Puksha, Raku and Wacheqsa. Thelarge class of Chavn ceramics is subdivided into the styles Ofrendas, Dragoniano,Qotopukyo and Floral, which themselves are again subdivided. The non-Chavnstyles are supposed to form close groups, which should be near together in thedendrogram. Indeed the Mosna style sherds form a well-separated, compact cluster(NAA-group 5) containing all studied Mosna specimens but no others. The sixstudied Wacheqsa specimens are all in NAA-group 1 and the 4 studied Pukshaspecimens are all in NAA-group 7, albeit together with a number of other styles.Thus, for Mosna, Wacheqsa and Puksha, there is a high degree of similarity inthe NAA data. This is not the case for the Raku ceramics, where the 5 studiedspecimens are divided between NAA-groups 1 and 3, nor for Puca Orqo, where the8 studied specimens are scattered over NAA-groups 1, 3, and 7.</p><p>The various styles of Chavn-type ceramics are widely scattered over the den-drogram, though not completely devoid of some systematic behaviour. Thus, Drag-</p></li><li><p>CERAMIC FINDS FROM THE GALERIA DE LAS OFRENDAS 53</p><p>Figure 1. Cluster analysis of the element concentrations determined by neutron activation analysisin 65 finds from the Galera de las Ofrendas (left). The dendrogram yields 8 groups. Surface finds(labelled with an ) and 61 sherds from the Pyramid Tello (represented by a single bar) are includedin the dendrogram on the right. There is no similarity between the finds from the Galera de lasOfrendas and from the Pyramid Tello. Some of the surface finds, however, cluster together withsherds from the Galera.</p></li><li><p>54 L. G. LUMBRERAS ET AL.</p><p>oniano is only in NAA-group 3, while the Ofrendas rojo sherds form two distinctbut compact NAA-groups, 4 and 6. Floral is in the widely different NAA-groups 1and 7, and Ofrendas gray is widely spread over NAA-group 1, 2, 3, and 7.</p><p>When the NAA data for the Galera de las Ofrendas are clustered together withthose for sherds from the Pyramid Tello and the surface finds from the settlementof Chavn (Figure 1, right), the material from the Pyramid Tello, which has beenconsidered as locally made [46], definitely forms an independent group. This canbe considered as evidence in favour of the notion that the vessels from the Galerade las Ofrendas were not made locally at Chavn. Part of the surface finds blend intothe groups formed by the sherds from the Galera (Figure 1, right). This may, insome cases, be incidental, but there is at least one case where mere coincidence canvirtually be ruled out: Ten of the surface finds form a very compact cluster togetherwith a sherd from the Galera de las Ofrendas (NAA-group 8) stemming from avessel of the style called Floral black, of which only this one vessel was found inthe Galera. These 11 specimens also have practically identical Mssbauer spectra(see Section 4.1), which confirms their common origin.</p><p>3. Thin-section microscopy</p><p>Thin sections were made of 65 sherds and analysed by optical microscopy [8]for texture and mineral content. The dominant minerals are varying amounts ofquartz, plagioclase, hornblende and biotite. Occasionally rock particles, clay nod-ules, hematite and magnetite as well as pores and plant inclusions are observed.Samples of the same archaeological style generally show similar thin sections,although a certain variation is observed in the detail. One sherd of each NAA groupis shown together with the respective thin section in Figures 2 and 3.</p><p>The sherds of the Wacheqsa type (NAA-group 1) form a rather homogeneousgroup with inclusions of medium size corresponding to texture C3 and D3 accord-ing to Riederer [8]. Sherds of the type Puca Orqo red (NAA-group 3) contain rockparticles and hematite and are somewhat coarse grained. Sherds of the Qotopukyotype (also NAA-group 3) have rock and plant inclusions as prominent properties.NAA-group 4 contains only two Ofrendas rojo sherds which are, however, strik-ingly different from all the others, containing large amounts of coarse inclusions.Samples of the Mosna type (NAA-group 5) are relatively uniform, with mediumgrain sizes and many plagioclase inclusions. NAA-group 6 contains six similarsherds of the type Ofrendas rojo with coarse-grained inclusions and additionalhematite. In NAA-group 7 four uniform and coarse grained sherds containing rockparticles are found, the other members of this group being rather inhomogeneous.NAA-group 8 consists only of one sherd of Floral black, containing large amountsof hornblende.</p><p>The obvious differences in the mineral content of the individual NAA groupsindicates a different provenance of the different groups. In many cases the resultsof the thin section study yield decisive clues for the classification of the sherds.</p></li><li><p>CERAMIC FINDS FROM THE GALERIA DE LAS OFRENDAS 55</p><p>Figure 2. Characteristic thin-section micrographs (right) of sherds (left) from the Galera de lasOfrendas belonging (from top to bottom) to NAA-groups 1 to 4. The dominant minerals are plagio-clase (P), quartz (Q), hornblende (H), biotite (B), rocks with different inclusions (R*), opaque ore(O*) and hematite (He). The scale bar on the left is 1 cm long, on the right it is 1 mm.</p></li><li><p>56 L. G. LUMBRERAS ET AL.</p><p>Figure 3. Characteristic thin section micrographs (right) of sherds (left) from the Galera de lasOfrendas belonging (from top to bottom) to NAA-groups 5 to 8. The dominant minerals are plagio-clase (P), quartz (Q), hornblende (H), opaque ore (O*) and serecite (S). The scale bar on the left is1 cm long, on the right it is 1 mm.</p></li><li><p>CERAMIC FINDS FROM THE GALERIA DE LAS OFRENDAS 57</p><p>4. Mssbauer spectroscopy and X-ray diffraction</p><p>4.1. THE TYPES OF MSSBAUER SPECTRA FOUND IN CERAMICS FROMCHAVN</p><p>The Mssbauer spectra of ceramics reflect the chemical and physical state of theiron after firing. X-ray diffraction, on the other hand, yields a status of all minerals,but the iron-containing ones often have too small concentrations to be seen. Thetwo methods therefore complement each other. The mineral content of ceramicsdepends on both the raw materials and the firing procedure. The raw materials maybear information on the provenance. The firing techniques are often characteristicfor certain workshops and therefore also bear implicit information on the prove-nance of ceramics. What we call the firing technique involves many parameters,like the firing temperature, the duration of the firing and the kiln atmosphere. Mat-ters are further complicated by variations of the temperature and kiln atmospherein the course of the firing process. All firing parameters may have been adapted bythe ancient potters to achieve the desired properties and looks of the vessels. Oftenthe surfaces of the vessels were polished or decorated by the application of a slip.Such surface treatments can be studied to depths of several hundred nanometres byconversion electron Mssbauer spectroscopy (CEMS) and to depths of several tensof m by Mssbauer spectroscopy with backscattered gamma rays or X-rays [9].Such experiments were performed in a few cases on ceramics from the Galera delas Ofrendas, though most of the work was done by standard absorption Mssbauerspectroscopy.</p><p>Adsorption Mssbauer spectra were measured at room temperature (RT) and inselected cases also at the temperature of liquid helium (4.2 K) with a source of 57Coin a rhodium matrix kept at the same temperature as the absorber. A surface layerof about a millimetre thickness of the sherds is often visibly different from the coreof the sherd. In such cases the interior is usually gray, while the surface is red orbrown, which already indicates that the iron in the surface layer is mainly trivalent,while it is mainly divalent in the cores. In such cases material from the surfaceand the core of the sherds was studied separately. Despite a certain variability ofthe Mssbauer spectra, dominant features could be established, which allowed thesamples to be classified according to the type of their Mssbauer patterns. Thedifferent types of Mssbauer spectra (Mos-types) were defined on account of thepresence and intensity or the absence of certain components, mainly in the RTMssbauer spectra. The use of eight different Mos-types, named A through H, is tosome extent arbitrary but appeared to be a viable compromise between a detailedcharacterisation and a limited number of different types. Only material from thecores was used for the characterisation of the Mos-types in order to avoid anyinfluence of surface treatments. Typical Mssbauer spectra of the eight differentMos-types are shown in Figures 4 and 5. Typical Mssbauer parameters for theindividual Mos-types are compiled in Table I. X-ray diffraction patterns of the</p></li><li><p>58 L. G. LUMBRERAS ET AL.</p><p>Figure 4. Characteristic Mssbauer spectra of Mos-types A through D for the cores of sherds foundin the Galera de las Ofrendas, Chavn. Measurements at RT (left) and 4.2 K (right) are shown.</p><p>samples whose Mssbauer spectra are shown in Figures 4 and 5 are reproduced inFigures 6 and 7.</p><p>For Mos-types A through D the RT spectra are dominated by an Fe3+ quadru-pole doublet, while in the 4.2 K spectra the sextet of hematite and a broad magnet-ically split background (fitted with a distribution of hyperfine fields) prevail. This</p></li><li><p>CERAMIC FINDS FROM THE GALERIA DE LAS OFRENDAS 59</p><p>Figure 5. Characteristic Mssbauer spectra of Mos-types E through H for the cores of sherds foundin the Galera de las Ofrendas, Chavn. Measurements at RT (left) and 4.2 K (right) are shown. Notethe different velocity scales.</p></li><li><p>60 L. G. LUMBRERAS ET AL.Table I. Characteristic Mssbauer parameters for the cores of 8 selected sherds measured at RTand 4.2 K. The Mos-types A through H were defined mainly on the basis of the Mssbauer spectra(see text). B is the magnetic hyperfine field, Q the quadrupole splitting and IS the isomer shiftwith respect to the source of 57Co in Rhodium [9]. A-mag is the fractional area of the magneticallysplit component(s), A that of the quadrupole doublets. The magnetic components are hematite (hem,magnetite (magn), a distribution of magnetic fields (dis) and an octet for magnetically split Fe2+(oct)</p><p>Mos Sample &amp; Mag B A-mag Species Q IS Atype temp. species Tesla % mm/s mm/s %</p><p>A 13/12 hem. 51.3 4.2 Fe3+(1) 0.79 0.28 57.9Wacheqsa magn. 45.4 6.7 Fe3+(2) 1.63 0.39 16.5</p><p>RT magn. 48.5 4.6 Fe2+(1) 2.93 0.75 10.1A 13/12 hem 52.6 32.0 Fe3+(1) 1.06 0.24 22.8</p><p>Wacheqsa dis 1049 34.9 Fe2+(1) 2.39 1.22 10.34.2 K</p><p>B 13/20 hem 51.0 6.4 Fe3+(1) 0.88 0.28 56.7Puksha magn. 45.8 13.4 Fe2+(1) 2.20 0.94 11.5...</p></li></ul>