Middle Guadiana River Basin (Badajoz, Spain and Alentejo, Portugal) Network Interactions: Insights from the Chemical Analysis of Bell Beaker Pottery and the Lead Isotope Analysis of Copper Items from the Third Millennium BC

C.P. Odriozola, M.A. Hunt-Ortiz, M.I. Dias, and V. Hurtado

1 Introduction

Several settlement networks from the Iberian Copper Age period are located alongside the Guadiana River (Iberian Peninsula) – i.e. Perdigo˜es, Reguengos de Monsaraz, Portugal (Dias et al. 2005; Valera 2006), or Tierra de Barros, Badajoz, Spain (Hurtado 1995, 1999). In this context, a clear relation has been found between the sites in terms of spatial organization (hierarchical, where La Pijotilla could be considered as a central place in a core-periphery system), a restricted stylistic distribution of the so-called Guadiana ‘eyed idol’ figurines (Hurtado 2008), or the distribution of bone based inlayed Bell Beaker pottery (Hurtado and Odriozola 2008; Odriozola in press). Since the 1970s, the Beaker Network paradigm (Clarke 1976) has been system- atically used to explain the broad and fast expansion of the so-called “Beaker phenomenon” all over Europe and the north of Africa, linked to the long distance trade of prestige items (copper items, ivory, amber, etc). However, little if any evidence of exchanged Bell Beaker (BB) pottery or copper items has been found after years of research, except for stylistic inferences. It is known that a style can be easily copied just by visual examination of the finished product; this is likely the easiest way to explain style dispersion, but does not justify hypotheses regarding vessel or copper artefact exchanges or transactions.

Research carried out within the I þ D Project (MAT2005-00790) and within the GRICES-CSIC Project (2005-PT0030). C.P. Odriozola (*) Instituto de Ciencia de Materiales de Sevilla, Centro Mixto Universidad de Sevilla-CSIC, Avd. Ame´rico Vespucio 49, 41092 Sevilla, Spain e-mail: [email protected] M.A. Hunt-Ortiz and V. Hurtado Departamento de Prehistoria y Arqueologı´a, Universidad de Sevilla, C/Marı´a de Padilla S/N, 41004 Sevilla, Spain M.I. Dias Instituto Tecnolo´gico e Nuclear, Estrada Nacional 10, 2686-953 Sacave´m, Portugal

I. Turbanti-Memmi (ed.), Proceedings of the 37th International Symposium on Archaeometry, 119 DOI 10.1007/978-3-642-14678-7_17, # Springer-Verlag Berlin Heidelberg 2011 120 C.P. Odriozola et al.

Our goal is to examine elite interactions and exchanges of BB pottery and copper production related items among the main sites of the Guadiana River Middle Basin (GRMB), in order to obtain a broad picture of prestige items’ consumption and distribution patterns within GRMB. This will be accomplished by chemical com- position analyses of Bell Beaker pottery and lead isotope analyses of items related to metallic production.

2 Materials and Methods

For this research study, X-ray Fluorescence (collected on a pellet – 50 mm particles size, diluted with powdered wax (0.1:0.061 ratio), and pressed at 40 Tm – using a Pananalytical Axios analyzer) was used to determine the elemental composition of 103 sherds from four sites (La Pijotilla, San Blas, Porto Torra˜o and Perdigo˜es), belonging to two differentiated settlement networks. This was done in order to determine compositional groups. The pottery selected for this study consisted of a homogeneous group of domestic household bowls (not expected to be exchanged) and a series of so-called “prestige pottery”, comprised mainly of Bell Beaker pots of Corded Zone Maritime (CZM), Maritime and Regional incised types, combed wares and what are referred to as “symbolic wares” in the Portuguese archaeolog- ical literature, mainly characterized by a decoration consisting of inverted triangles, and, in most of the cases, filled with impressed dots. Compositional data for major and minor elements were log-transformed (to base 10) in order to normalize data prior to the statistical analysis. Hierarchical Cluster (HC) on Ward’s method and Principal Component Analysis (PCA) were developed on the normalized compositional data, in order to determine the number of compo- sitional clusters in the data set, following well-established procedures (Baxter 1994; Glascock 1992). No outlier detection or variable selection method was used to perform this analysis. For the lead isotopic analyses, six copper metallurgy related samples from the site of San Blas were submitted to Thermal Induced Mass Spectrometry, following well-established procedures (Hunt Ortiz 2003). These analyses were complemented by the characterization of samples obtained from mineral deposits exploited in modern times and containing copper minerals, located in the proximity of San Blas: the Novillero Viejo mine, close to the site, and the Norte Alconchel mine. The lead isotopic results obtained were compared with those previously carried out on metallic items from the site of La Pijotilla (Hunt Ortiz 2003).

3 Results

Although the number of samples analysed with lead isotopes is still limited, some interpretations on possible exchange networks can be pointed out from the available results. Regarding the site of San Blas, the copper production was not based on a Middle Guadiana River Basin Network Interactions 121 single mineral deposit. The mineral deposit isotopically characterised in the vicinity of San Blas, Novillero Viejo (the closest mine), had a different isotopic composition from the archaeometallurgical samples from San Blas, although the Alconchel Norte mine showed isotopic consistency with one of the slag samples (nº 9) from San Blas. At a regional level, the comparison of the lead isotopic compositions between San Blas and La Pijotilla samples showed a clear isotopic consistency among archaeometallurgical samples from the two sites (Fig. 1). With regard to the pottery samples, six significant tendencies in compositional variation can be observed on the Ward’s method HC output (Fig. 2a), where sherds recovered at each specific site generally cluster together. However, a small number of

San Blas Metals 2.1 San Blas Mineral San Blas Slags La Pijotilla Metals 2.08

2.06

2.04

2.02

2

1.98

1.96

0.78 0.8 0.82 0.84 0.86 207Pb/206Pb

21 San Blas Metals San Blas Minerals 20.5 San Blas Slags La Pijotilla Metals 20

19.5

19 206Pb/204Pb 208Pb/206Pb

18.5

18

17.5 0.76 0.78 0.8 0.82 0.84 0.86 0.88 207Pb/206Pb

Fig. 1 Lead Isotope plots: San Blas versus La Pijotilla 122 C.P. Odriozola et al. samples clusters into these groups; thus, it can be assumed that producers/consumers were exchanging some pots between sites, possibly as part of a trade/exchange network, since it seems unlikely that potters from different sites could have used raw materials that were geochemically similar, and/or prepare the paste in a similar way. The varimax rotated PCA scores of the normalised data of the first two compo- nents (Fig. 2b) corroborate the tendencies observed in the HC, clustering together in the HC, as well as in the PCA. These groupings appear to reflect differences in geographical location and geology of clay sources, along with potters’ behaviour. Thus, the pottery found at the site of San Blas possesses distinct geochemical signatures from that found at La Pijotilla, Porto Torrao or Perdigo˜es, as can be seen in the mean concentrations and standard deviation of each cluster group (as summarized in Table 1).

Fig. 2 (a) Ward’s method HC, (b) PCA score and loading plots ideGain ie ai ewr neatos123 Interactions Network Basin River Guadiana Middle

Table 1 Mean major element concentrations for each of the cluster groups, expressed in oxide wt% (shadowed data are expressed in ppm) Porto Torra˜o 1 Perdigo˜es La Pijotilla 1 Porto Torra˜o 2 La Pijotilla 2 San Blas X SD X SD X SD X SD X SD X SD

SiO2 50.99 3.39 52.00 1.95 54.66 3.07 48.99 1.44 67.22 9.21 55.97 6.78 Al2O3 18.48 1.16 16.89 1.11 17.49 1.13 18.59 1.32 13.79 2.18 18.55 1.91 Fe2O3 8.38 1.08 8.53 1.57 10.95 1.30 11.38 1.73 5.33 2.65 8.38 2.70 MnO 0.11 0.02 0.10 0.03 0.12 0.02 0.13 0.02 0.07 0.05 0.10 0.06 MgO 2.20 0.55 2.72 0.76 0.12 0.04 2.40 0.63 0.07 0.05 0.19 0.39 CaO 2.20 0.55 2.72 0.76 2.61 0.79 2.40 0.63 1.61 0.91 1.72 0.73 Na2O 5.97 0.76 4.10 0.45 3.09 0.82 5.93 0.64 2.86 2.45 2.61 0.80 K2O 1.64 0.24 1.08 0.28 1.49 0.31 1.94 0.35 0.81 0.46 1.34 0.76 TiO2 0.67 0.27 1.68 0.21 2.05 0.52 0.56 0.15 1.99 0.46 2.08 0.73 P2O5 0.83 0.21 0.82 0.16 1.29 0.37 1.76 0.48 0.81 0.59 0.93 0.21 As 0.18 0.09 1.51 1.37 0.46 0.24 0.15 0.09 0.66 1.06 2.58 1.80 Ba 2.92 0.97 4.43 0.53 8.17 4.26 3.00 1.32 6.27 1.49 10.94 4.75 Co 888.83 168.66 1,419.00 408.16 1,526.33 854.01 621.67 212.36 1,242.73 345.36 1,499.26 710.69 Cr 30.46 4.49 22.29 2.81 35.17 8.06 42.67 8.67 18.33 8.85 26.34 12.53 Cu 110.54 36.00 120.00 40.52 91.17 26.23 95.11 48.26 114.40 100.54 284.17 161.57 Ni 58.04 17.68 20.29 13.76 50.83 45.29 81.89 28.48 55.13 36.95 187.63 164.22 Rb 65.17 11.92 46.43 10.21 67.33 24.88 53.00 9.19 51.93 10.15 75.31 25.19 Sr 42.63 7.74 73.14 8.84 86.17 19.84 37.00 3.39 80.67 20.24 97.89 52.59 V 206.63 25.02 134.71 33.87 182.50 82.06 238.22 35.78 122.00 100.46 199.49 81.90 Zn 208.00 66.41 154.86 28.42 200.00 54.09 467.89 159.56 105.87 80.09 158.06 62.07 Zr 35.38 8.38 61.86 11.47 104.67 13.11 58.78 45.16 69.07 19.35 91.86 34.16 124 C.P. Odriozola et al.

4 Discussion

The six clusters found on the data set are believed to reflect local clay deposits and/ or manufacturing traditions. However, the multiple compositional groups appearing in a ceramic assemblage of a single site (La Pijotilla or Porto Torrao) may represent either differences due to exchange, or differences in technical behaviour, which is more likely. If we look at the statistical analysis, it is clear that none of these compositional groups correspond to exchanged vessels. Nevertheless, there is an interesting 14% of pottery samples that does not cluster with the rest of the samples recovered at one site. Thus, this percentage of pottery may have been exchanged from its production site to other locations within social or trade networks. The pottery exchange follows a main east-west axis, while the west-east axis is only present between La Pijotilla and San Blas. Regarding the isotopic composition of the mineral deposits and copper metal- lurgy related samples (metal objects and by-products), the diversity of sources for copper mineral procurement, involving different geological areas (not necessarily the closest mines were exploited), can be clearly observed. The lead isotope analysis of samples from the sites of San Blas and La Pijotilla also shows that exchange networks were in place.

5 Conclusions

The detection of a significant 14% of exchanged pottery seems to constitute reliable evidence of local network exchange flows or inter village alliances. Thus, pottery was probably being exchanged within and between settlement networks, but we cannot say at the moment if these exchanges were made directly between settle- ments, within an inter-settlement network exchange framework, i.e. between La Pijotilla and Porto Torrao, or if San Blas, Perdigo˜es, and/or other settlements were acting as intermediary agents between both of them in a nodal exchange system. The consistence in isotopic composition between the metal related archaeolog- ical samples from San Blas and La Pijotilla (with no evidence of copper smelting at this last site) points to San Blas as a production site, with a complex mineral procurement network, supplying metallic artefacts to La Pijotilla. This evidence provides a closer insight into the settlement network scale exchange systems, supporting the hypothesis of La Pijotilla as a central redistributive place, as previously argued by V. Hurtado (1995). The interactions between San Blas and La Pijotilla could involve the exchange of copper items processed at San Blas, and the distribution of BB pottery from La Pijotilla to San Blas at an early stage of this network. The picture of GRMB is complex: we have direct evidence of the exchange of metal objects from San Blas to La Pijotilla, and also evidence of La Pijotilla producing and distributing BB pottery to San Blas, Perdigo˜es and Porto Torrao. Middle Guadiana River Basin Network Interactions 125

Although it was thought that copper resources were mined, processed and exchanged within local settlement networks, it appears that, like BB pottery, metal was also involved in broader exchange networks that included further settlement networks.

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