2009 International Nuclear Atlantic Conference - INAC 2009 Rio de Janeiro,RJ, Brazil, September27 to October 2, 2009 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: 978-85-99141-03-8 ARCHAEOLOGICAL POTTERY FRAGMENTS ANALYSIS FROM SAMBAQUI DO BACANGA (MA-BRAZIL) WITH A PORTABLE EDXRF SYSTEM Renato A. Ikeoka 1, Carlos R. Appoloni 1, Paulo S. Parreira 1, Fábio Lopes 1, Arkley M. Bandeira 2 1 Departamento de Física/CCE Universidade Estadual de Londrina Cx.Postal 6001 CEP 86051-990 Londrina/PR Brazil renatoikeoka@yahoo.com.br 2 Museu de Arqueologia e Etnologia Universidade de São Paulo Av. Prof. Almeida Prado, 1466 CEP 05508-900 - Cidade Universitária - São Paulo/SP Brazil; arkleybandeira@hotmail.com ABSTRACT Sambaqui do Bacanga archaeological site is located in the Island of São Luis - Maranhão Brazil, in the region bathed by the Bacanga River. A stratigraphic collection of 68 pottery fragments was collected during the years 2005 and 2006 to perform a qualitative analysis of the chemical elements employing a Portable System of Energy Dispersive X-ray Fluorescence (PXRF). The elements K, Ca, Ti, Mn, Fe, Zn, Br, Rb, Sr, Y, Zr and Pb were identified in the different fragments and only Fe, Ca, Sr, Zr, Mn, Ti and Zn were common elements for all of them, indicating that these elements are present in the raw material used in the manufacture of the fragments. Only one fragment presented remains of painting. A larger concentration of Fe was observed in this region compared to other areas. This indicates that a material with iron oxide was used to make the painting. The elements Fe, Sr, Mn, Ti and Zn are present, systematically, with larger intensities on concave and convex sides in relation to the ceramic paste for 43 among the 68 analyzed fragments, indicating a different surface treatment that leads to an enrichment of those elements. Cluster analysis was performed with the pottery fragments at three levels. The fragments were grouped in three different clusters, except for two fragments from the 132 cm level, which grouped with the fragments from 10-20 cm level. This result indicates three different sources of clay for the studied pottery fragments. Keywords: PXRF, Portable X-ray Fluorescence, Archaeological Pottery, Archaeometry. 1. INTRODUCTION In the State of Maranhão - Brasil, where there is not enough archeological information available to constitute a minimal picture of the pre-colonial occupations in the territory, a research project is being developed for the first time. Its name is Sambaqui do Bacanga at Ilha de São Luís-Maranhão: a study on the ceramic occurrence in the archeological records [1]. In the archeological excavations in Sambaqui do Bacanga, several types of material vestiges have been evidenced, like fire remains, human skeletons, remains of animal bones, fish remains, shells, mollusk shells and ceramic objects. Ancient civilizations that inhabited that
territory were characterized by being fishing populations - catchers hunters and ceramists, who settled down in the region around 6,600 years ago and remained inhabiting the place till the year 900 of our era [1]. Amidst all such material culture, ceramics are highlighted as objects of highly archeological value because they are extremely resistant to weather and environment conditions [2]. The chemical characterization of such fragments may provide important information about the origin of the raw material, the quality of the coating, indexes of the occurrence of paintings, etc., which help the archeological studies about the peoples in that region. Thus, the Energy Dispersive X-Ray Fluorescence technique (EDXRF) was used in the identification of the chemical elements that constitute the ceramics. As it is a multi-elementary, simultaneous and non-destructive technique, the EDXRF has been gaining a great deal of importance in archeological studies [3-7]. The pottery fragments were analyzed by using a Portable System of Energy Dispersive X-Ray Fluorescence (PXRF) with the aims of verifying the existence of painting vestiges in the fragments, as well as if there is some kind of treatment in the concave and convex sides in relation to the ceramic paste of the fragments and finally, using grouping analysis to check the similarity among the chemical elements identified in the fragments not only with the same stratigraphic level but also with different levels. 2.1. Description of the Samples 2. MATERIALS AND METHODS The pottery fragments were collected in an archeological site in Sambaqui do Bacanga, located in the Bacanga National Park in Ilha de São Luis MA. A stratified collection of 68 pottery fragments was conducted. The provenance of such fragments are the following sectors: Exploratory Trench, Excavation Area 1, Profile 1 and Profile 2, as the following tables 1 to 4 show. Table 1. Information about fragments in sector Exploratory Trench. Sample Quantity of fragments Stratigraphic levels (cm) Sample 03 01 Surface Sample 09 02 Surface Sample 20 11 Surface Sample 15 02 125 Sample 05 01 128 Sample 12 03 128 Sample 17 03 135 Sample 18 02 138 Sample 07 08 144 Sample 01 01 150 Total 34 07
Table 2. Information about fragments in the sector Excavation Area 1. Sample Quantity of fragments Stratigraphic level (cm) Sample 02 01 Surface Sample 10 03 Surface Sample 11 02 Surface Total 06 01 Table 3. Information about fragments in sector Profile 1. Sample Quantity of fragments Stratigraphic levels (cm) Sample 04 01 0 8 Sample 14 02 10 20 Sample 06 01 80 Sample 22 04 113 Sample 21 07 125 Sample 19 06 132 Sample 08 03 140 Total 24 07 Table 4. Information about fragments in sector Profile 2. Sample Quantity of fragments Stratigraphic levels (cm) Sample 13 02 30 35 Sample 16 02 40 Total 04 02 Table 5 shows the description of the sectors excavated in Sambaqui do Bacanga. Table 5. Sectors excavated in Sambaqui do Bacanga. Excavation sector Elevation variation (m) Excavation area (m 2 ) Excavation area 1 74 20 Exploratory Trench 72 16 Profile 1 72 4,45 Profile 2 70 3
2.2. EDXRF Portable System The EDXRF (PXRF-LFNA-02) portable system utilized for irradiation/detection of the fragments consists of a 4W X-ray mini-tube with Ag anode and 50 µm Ag filter (Moxtek, Inc.); a Si-PIN detector with pre-amplifier XR-100CR (AMPTEK Inc.), 221 ev FWHM for the 5.9 kev Mn line, 25 μm Be window and thermoelectric cooling system by Peltier Effect; PX2CR conjugated high tension source module and amplifier (AMPTEK Inc.); multichannel analyzer model MCA8000A (AMPTEK Inc.); an excitation-detection system positioning module with freedom degrees XYZ and rotation in relation to the analyzed sample; and a notebook for data acquisition and storage. Fig. 1 shows the system used to carry out the measurements. Measurement conditions were 28 kv and 5 μa in the X-ray mini-tube and acquisition time was 500 seconds. Figure 1. X-ray Fluorescence Portable System: (1) Sample carrier, (2) X-ray Mini-tube, (3) X-ray non-cryogenic detector, (4) Standard electronic equipment and (5) Notebook. In average, nine measurements were made for each fragment, three of which in the concave face, three in the convex face and three in the ceramic paste. The analysis of the spectra was conducted by using the software Quantitative X-Ray Analysis (WinQXAS), distributed by the International Atomic Energy Agency (IAEA). For the analyses of the data obtained with WinQXAS, only the intensities of the chemical elements whose net areas were threefold higher their standard deviation were considered. 3. RESULTS AND DISCUSSION It was possible to observe the elements K, Ca, Ti, Mn, Fe, Zn, Br, Rb, Sr, Y, Zr and Pb in the different fragments analyzed. The statistical deviations of those determinations were, in
general, 1% for Fe, 5% for Ca, from 5 to 10% for Sr, Zr, Mn, Ti and Zn, and from 20 to 25% for K, Br, Rb, Y and Pb. The elements Ca, Ti, Mn, Fe, Zn, Sr and Zr appeared in the ceramic paste of all the 68 analyzed fragments, indicating that such elements are present in the constitution of the clay used in the manufacture of these ceramics. The elements Fe, Sr, Mn, Ti, and Zn presented systematically higher intensities in the faces in relation to the ceramic paste in 43 out of the 68 analyzed fragments, indicating that there is a treatment in the faces, with enriching for those elements, which is the engobe. This behavior is shown in Figures 2 to 5, which refer to element Fe in the Exploratory Trench, with exception of sample 20; Ti in Excavation area 1, with exception of sample 10.1; Zn of Profile 1, with exception of samples 21 and 22; and Sr of Profile 2, respectively. By analyzing sample 3, which is the only fragment where painting vestiges can be visualized in both sides, it is possible to notice that the concave and convex faces have more Fe concentration in these regions with painting vestiges in comparison with the regions of the same faces without painting. This behavior is shown in Figure 2, in which, on the left, there is a rectangle separating sample 3 from the other samples in this sector. The measurements carried out in the region without painting are in the spots on the left, and the measurements carried out in the region with painting are in the spots on the right. 900 800 Sam.3 Sam.20 Fe Sam.7 Convex Paste Concave Intensity (cps) 700 600 500 400 Sam.9 Sam.15 Sam.12 Sam.17 Sam.5 Sam.18 Sam.1 300 200 100 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52 Sample Figure 2. Graph of Fe intensity for the samples in the Exploratory Trench, in which the samples are separated in different stratigraphies and the number of fragments is in brackets: surface {samples 3(1), 9(2) e 20(11)}, 125 cm {sample 15(2)}, 128 cm {samples 5(1) and 12(3)},135cm {sample 17(3)}, 138 cm {sample 18(2)}, 144 cm {sample 7(8)} and 150 cm {sample 1(1)}.
20 18 16 Sam. 2 Ti Sam. 10.3 Sam. 10.2 Sam. 11.1 Convex Paste Concave Sam. 11.2 14 Intensity (cps) 12 10 8 Sam. 10.1 6 4 2 0 0 1 2 3 4 5 6 7 8 9 10 11 Sample Figure 3. Graph of Ti intensity for the samples in the sector Excavation area 1, in which all the pottery fragments are from the surface. 12 Sam. 22 Zn Convex Paste Concave 10 Sam. 21 Sam. 19 8 Sam. 14 Intensity (cps) 6 4 Sam. 4 Sam. 6 Sam. 8 2 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 Sample Figure 4. Graph of Zn intensity for samples from Profile 1, in which the samples are separated in different stratigraphies and the number of fragments is in brackets: sample 4(1) 0 to 8 cm, sample 14(2) 10 to 20 cm, sample 6(1) 80 cm, sample 22(4) 113 cm, sample 21(7) 125 cm, sample 19(6) 132 cm and sample 8(3) 140 cm.
55 50 Sr Sam. 16.1 Convex Paste Concave 45 40 Intensity (cps) 35 30 25 20 15 Sam. 13.1 Sam. 13.2 Sam. 16.2 10 5 0 1 2 3 4 5 6 Sample Figure 5. Graph of Sr intensity for samples in Profile 2, in which the samples are separated in different stratigraphies and the number of fragments is in brackets: sample 13(2) 30 to 35 cm and sample 16(2) 40 cm. By applying cluster analysis in the study of the pottery fragments of stratigraphies 10 to 20 cm, 132 cm to 144 cm, it was possible to observe the formation of three distinct groups for the fragments of the three stratigraphies, apart from two fragments of the 132 cm stratigraphy, which stayed in the same group of the fragments of stratigraphy 10 to 20 cm, as seen in Figure 6. This result indicates that the analyzed fragments were manufactured with clay from three different origins. Figure 6. Dendogram with pottery fragments excavated in three stratigraphies, 10 to 20 cm (represented as 20 cm), 132 cm and 144 cm, the last algarism from left to right in the sample code represents the sample number.
4. CONCLUSIONS Utilizing an EDXRF portable system to analyze pottery fragments collected in an archeological site in Sambaqui do Bacanga, it was possible to observe that the basic elements in the constitution of the clay used to manufacture these fragments were Fe, Ca, Sr, Zr, Mn, Ti and Zn. It could also be noticed that a material with high iron concentration was possibly used in the painting to give the red colour, which was found only in one of the samples. Out of the 68 pottery fragments analyzed, 43 presented a different treatment on the faces in relation to the ceramic paste. It means that on these 43 fragments it was applied engobe, which is a kind of clay enriched with the elements Fe, Sr, Mn, Ti, and Zn. This more refined material is characterized by forming a concentration increase of such elements in the faces when the ceramics are burnt in the manufacturing process. From the cluster analysis of the pottery fragments of three stratigraphies, the formation of three groups was observed. This result indicates that the fragments analyzed were manufactured with clay from three different origins. ACKNOWLEDGMENTS To Fábio Luiz Melquiades and Wislley Dueli da Silva for their collaboration in the sample measurements, and to CNPq for the scholarship awarded during the MA Course. REFERENCES 1. Bandeira, A.M., Ocupações humanas pré-históricas no litoral Maranhense: um estudo arqueológico sobre o sambaqui do Bacanga na Ilha de São Luís- Maranhão, Masters Dissertation of Archaeology, Universidade de São Paulo, São Paulo Brazil (2008). 2. Latini, R.M.; Bellido, A.V.; Vasconcellos, M.B.A.; Dias, O.F., Classificação de cerâmicas arqueológicas da Bacia Amazônica, Quim. Nova, 24, pp. 724-729 (2001). 3. Appoloni, C.R.; Quiñones, F.R.E.; Aragão P.H.A.; Santos, A.O.; Silva, L.M.; Barbieri, P.F.; Nascimento Filho, V.F.; Coimbra M.M., "EDXRF study of Tupi-Guarani archaeological ceramics, Radiation Physics and Chemistry, 61, pp. 711-712 (2001). 4. Appoloni, C.R.; Parreira, P.S.; Souza, E.; Quacchia, J.C.A.; Nascimento Filho, V.F.; Gigante, G.E.; Cesareo, R.; Cunha e Silva, R.M., Estudo de cerâmicas arqueológicas do Paraná por técnicas nucleares não destrutivas, Rev. Do Museu de Arqueologia de Etnologia, São Paulo, 2, pp. 135-149 (1997). 5. Parreira, P.S., Metodologia de ED-XRF e aplicações com um sistema portátil, Technical Publication PT 01/07, Universidade Estadual de Londrina, Londrina Brazil (2007). 6. Silva, F.A.; Appoloni, C.R.; Quiñones, F.R.E.; Santos, A.O.; Silva, L.M.; Barbieri, P.F.; Nascimento Filho, V.F., A Arqueometria e a Análise de Artefatos Cerâmicos: um estudo de fragmentos cerâmicos etnográficos e arqueológicos por fluorescência de Raios X (EDXRF) e transmissão Gama, Revista de Arqueologia, 17, pp.41-61 (2004). 7. Silva, F.A.; Nascimento Filho, V.F.; Appoloni, C.R.; Perez, C.A., Fluorescência de Raios X aplicada a amostras arqueológicas, Revista do Museu de Arqueologia e Etnologia MAE, USP, 15/16, pp. 371-382 (2005/2006).