Approaches to Ancient Metallurgy in the Atacama: Scientific Analyses of Metal
Artefacts from Oasis Sites in Northern Chile
B. Maldonado
1, Th. Rehren
2, E. Pernicka
3, L. Núñez
4, and A. Leibbrandt
51. Center for Archaeological Studies, El Colegio de Michoacán, A.C., Ext. La Piedad, México, bem171@gmail.com
2. UCL Qatar, Hamad bin Khalifa University, Doha, Qatar, th.rehren@ucl.ac.uk
3. Curt-Engelhorn-Zentrum Archäometrie, Mannheim, Germany, ernst.pernicka@cez-archaeometrie.de
4. Universidad Católica del Norte, Antofagasta, Chile, lautaro.nunez@hotmail.com
5. Codelco Casa Matriz, Santiago de Chile, Chile, ALeibbra@codelco.cl
ABSTRACT
The San Pedro de Atacama region is home to some of the most important archaeological sites in northern Chile, having experienced continuous human occupation for more than 4000 years.
Most investigations of these settlements have built on information from over 3000 burials in 47 cemeteries, excavated by the Belgian priest Gustavo Le Paige over the course of nearly three decades in the mid 20th century. Numerous metal objects have been recovered from some of the above mentioned funerary contexts, most of them associated with thirteen small agricultural oases of San Pedro. Our research involved documentation and sampling of previously excavated artefacts from the Archaeological Museum in San Pedro de Atacama, as well as a collection of copper-rich mineral samples from different mining locations in the Atacama region.
This work presents the general results of a systematic study of the archaeometallurgy of copper in the Atacama region initiated in 2010 as part of a joint international scientific project, including the Curt-Engelhorn-Zentrum Archäometrie (CEZA) in Germany, the UCL Institute of Archaeology, University College London (IoA), and the R. P. Gustavo Le Paige Archaeological Museum in San Pedro de Atacama in Chile.
KEYWORDS
Archaeometallurgy, Chile, copper, pre-Columbian, scientific analyses.
Archaeological Background
The Andes is a rich metallic ore-bearing region, which, to this day, provides a variety of minerals for the production of gold, silver, copper, and tin. From the standpoint of the
pre-Columbian peoples, however, copper was the most important metal and played a prominent role in the early metallurgy of the area. Copper was not only the predominant metal, but the most extensively used base material. Andean metalworkers produced an assortment of copper-based alloys, including copper-arsenic and tin bronze, which were fashioned mainly as ornaments used in religious ceremonies and for the enhancement of elite cultural status. Numerous metal artefacts, most of them from mortuary contexts, have been recovered in the Atacama Desert of northern Chile. Nevertheless, the technological, social and economic processes involved in the production and distribution of these objects remains virtually unknown.
Mineral resources from the Atacama area and surrounding vicinity (Fig. 1) might have been of importance to pre-Columbian cultures. The earliest dated evidence of metalworking in the area comes from the south-eastern margin of the Atacama basin, where items from hammered copper foil and gilded copper have been recovered from archaeological contexts dating to the Tilocalar phase of the Early Formative period (1500-400 B.C.) (Nuñez et al. 2006). The tradition of sheet-metal working (hammering, gilding, annealing, and repoussé) was common throughout the Andes and remained pervasive during the Early Intermediate Period and the Middle Horizon (Lechtman 1979).
The earliest evidence to date for smelting activity in northern Chile comes from in the Guatacondo Valley. Excavations at the Ramaditas site have revealed evidence of early copper smelting activities dating to 500 B.C. (Graffam et al. 1994, 1996). These finds suggest that extractive metallurgy was carried out on a small scale and smelting was performed on a periodic basis. Nevertheless, metalworkers had achieved an efficient smelting technology, which might be attributable in part to the high quality of copper ore in the dry Atacama Desert. The research confirmed that not only does metallurgy date back in excess of 2,000 years in northern Chile, but that this activity was often carried out independent of the presence of a large formalised state or Empire (Cooke et al. 2008).
Fig. 1. The Atacama area in the context of the South Central Andes (Modified from Llagostera 1995:10).
The San Pedro de Atacama region (Fig. 2) is home to some of the most important archaeological sites in northern Chile, having experienced continuous human occupation for more than four thousand years (Agüero 2005; Llagostera and Costa 1999; Nuñez 1995). Most investigations of these settlements have built on information from over 3000 burials, excavated in 47 cemeteries by Father Gustavo Le Paige over the course of nearly three decades (Le Paige, 1957-58, 1963a, 1963b, 1964a, 1964b, 1970, 1974), and subsequent mortuary archaeology. Different categories of artefacts, including implements such as axes, maces, chisels, and tweezers as well as adornments which include pins and metal discs, have been recovered from funerary contexts of thirteen small agricultural oases of San Pedro. However, because of the prevalent nature of the research in the area, archaeological data for either mining or extractive metallurgy are sparse and unclear.
Archaeometallurgical Research
The present work is part of an international collaboration programme which investigates metallurgical activities in
northern Chile using scientific analysis as a first step towards a large-scale map of prehistoric copper production and exchange across the South Central Andes. A first systematic study of the archaeometallurgy of copper in the Atacama region was initiated in 2010, as part of a joint international scientific project including the Curt-Engelhorn-Zentrum Archäometrie (CEZA) in Germany, the Institute of Archaeology, University College London (IoA, UCL), and the R. P. Gustavo Le Paige Archaeological Museum in San Pedro de Atacama in Chile. The project was possible due to a fellowship from the Alexander von Humboldt Foundation, and funding provided by the National Copper Corporation of Chile (Codelco). This research involved documentation and sampling of previously excavated artefacts from the Archaeological Museum in San Pedro de Atacama, as well as the collection of copper-rich mineral samples from different mining locations in the Atacama region.
Sampling and measurements
Over a thousand metal artefacts from the Le Paige collection have been recorded in the course of two research seasons of the present project. Saw-cut samples and drill shavings were obtained from 175 of these objects, considering not only their category and provenience, but also their state of preservation. The examined samples correspond to different categories of artefacts including implements such as axes, maces, chisels, and tweezers as well as adornments, which include pins and metal discs (Fig. 3).
A total of 80 samples were collected during a first sampling period in 2010, all of which were analysed by XRF (energy-dispersive X-ray fluorescence spectrometry). A second sampling effort was conducted in 2011 and 95 more samples were analysed by the same method. The saw-cut samples were further examined by metallography and scanning electron microscopy using energy dispersive analysis (SEM-EDS) and characterised chemically by electron microprobe. Twenty samples, including both shavings and fragments, have been further selected for lead isotope analysis and are still being processed.
Results and Discussion
The results obtained so far have been extremely valuable. XRF analysis has enabled us to characterise the different elements present in the metal objects. These results provide information on the nature of the raw materials used in different chronological and spatial contexts. The chronological span best represented in our sample group is the Middle/Intermediate Period (approximately A.D
700-1470), which is presumed to be characterised by an outstanding influence from Tiwanaku. About 55% of the samples correspond to artefacts recovered from sites dated to this time; a high percentage of them consist of a ternary Cu-As-Ni alloy, which has been regarded as a cultural and technological marker of the Middle Period in the Bolivian Altiplano and in northern Chile.
This alloy appears to have co-existed with tin bronze and other copper-based alloys (see Table 1). Optical metallography has been used to reveal the microstructural
features of the analysed samples and the identification of very specific manufacturing techniques such as gilding. SEM-EDS analyses were performed to allow a safer confirmation of the nature of the phases (Figure 4). Electron probe microanalysis proved a highly effective technique for the generation of compositional data, providing a chemical characterisation of the samples. Finally, lead isotope analyses will be used to characterise potential ore sources in northern Chile. Lead isotope analysis has been one of the most important methods developed for the research of the movement of metal ores, ingots and finished metal products in ancient economic systems (see Rehren and Pernicka, 2008; Gale and Stos-Gale 1982).
Summary and Conclusions
Archaeometallurgical research is well established in the Old World and particularly the Middle East, but very much lacking in the New World, despite the rich and complex metallurgical heritage of South America. Few archaeological investigations of metallurgy have been Fig. 2. Archaeological oases in the Atacama. The location of San Pedro de Atacama is marked as a red dot. (After Acosta and Llagostera 1994: Fig. 1).
Fig. 3. Different categories of artefacts from the collection of the Archaeological Museum in San Pedro de Atacama.
!
Fig. 4. Fragment of gilded metal foil fabricated from Au-Ag-Cu. SEM image and analysis of the surface.
carried out in the Central Andes in general and, in particular, in current Chilean territory.
This pioneer research has aimed to establish a first systematic investigation of production and distribution of copper and copper-based alloys in pre-Hispanic South America, centred on a case study in northern Chile. The project is predominantly archaeological science based, involving the sampling and scientific investigation of metallurgical materials from a number of archaeological sites in the Chilean Atacama Desert. The reported data form the basis for a reference collection and possibly will enable the first tentative allocations of artefacts to specific regions of provenance. Beyond the immediate archaeometric and archaeometallurgical significance of this project, it will also make a major contribution to a more balanced understanding of pre-Hispanic metallurgy in the Americas in general, by shifting the focus onto the much under-explored primary production and its likely cultural diversity, and on the intercultural effects of long-distance trade in commodities among equal and dependent societies, respectively.
Acknowledgements
Funds for this project were generously provided by the Alexander von Humboldt Foundation and the Corporación Nacional del Cobre, Chile (Codelco). Special thanks are also due the R. P. Gustavo Le Paige Archaeological Museum, in San Pedro de Atacama.
References
Agüero, C., 2005. Aproximación al asentamiento humano temprano en los oasis de San Pedro de Atacama. Estudios Atacameños 30, 29-60.
Cooke, C.A., Abbott, M.B., and Wolfe A.P. 2008. Metallurgy in Southern South America. In: Seline, H (Ed) Encyclopedia of the History of Science, Technology, and Medicine in Non-Western Cultures Vol. 2. Kluwer Science, Dordrecht, 1658-1662.
Costa, M.A. and Llagostera A. 1994. Coyo 3: Momentos Finales del Periodo Medio en san Pedro de Atacama. Estudios Atacameños 11, 73-107.
Graffam, G.J., Rivera, M. and Carevic A. 1994. Copper Smelting in the Atacama: Ancient Metallurgy at the Ramaditas Site, Northern Chile. In: Craig A.K. and West R.C. Quest of Mineral Wealth. Geosciences Publications, Baton Rouge, 75-92. Graffam, G.J., Rivera, M. and Carevic A. 1996. Ancient
Metallurgy in the Atacama: Evidence for Copper Smelting During Chile’s Early Ceramic Period. Latin American Antiquity 7(2), 101-13.
Llagostera M.A. 1995. El Componente cultural Aguada en San Pedro de Atacama. Boletín del Museo Chileno de Arte Precolombino 6, 9-34.
Llagostera, A. and Costa A., 1999. Patrones de asentamiento en la época agroalfarera de San Pedro de Atacama (norte de Chile). Estudios Atacameños 17, 175-206.
Núñez, L., 1995. Evolución de la ocupación y organización del espacio atacameño. In: L. Pourrut and L. Núñez (Eds.) Agua, ocupación del espacio y economía campesina en la región atacameña. Aspectos dinámicos. Universidad Católica del Norte, Antofagasta, 18-60.
Núñez, L., 2006. El Templete Tulán de la Puna de Atacama: Emergencia de Complejidad Ritual Durante el Formativo Temprano (Norte de Chile). Latin American Antiquity 17(4), 445-473.
Lechtman, H.N. 1979. Issues in Andean Metallurgy. In: Benson, E.P (Ed.) Pre-Columbian Metallurgy of South America. Dumbarton Oaks, Washington, 1-40.
Le Paige, G., 1957-58. Antiguas culturas atacameñas en la cordillera chilena. Anales de la Universidad Católica de Valparaíso 4-5, 15-144.
—— 1963a. La antigüedad de una tumba comprobada por C14 y el ambiente que lo rodea. Revista de la Universidad Católica XLVIII, 167 176.
——1963b. Continuidad y discontinuidad de la cultura atacameña. Congreso Internacional de Arqueología en San Pedro de Atacama. Anales de la Universidad del Norte 2, 7 25. ——1964a. Los cementerios de la época agroalfarera en San Pedro
de Atacama. Anales de la Universidad del Norte 3, 51 91. ——1964b. El precerámico en la cordillera atacameña y los
cementerios del Período Agroalfarero de San Pedro de Atacama. Anales de la Universidad del Norte 3, 49-93. ——1970. Industrias líticas de San Pedro de Atacama. Ediciones
Orbe y Universidad del Norte, Santiago. 478 pp.
——1974. Informes de trabajo. Estudios Atacameños 2, 101-104. Rehren, Th. and Pernicka, E., 2008. Coins, Artefacts and Isotopes:
Archaeometallurgy and Archaeometry. Archaeometry 50, 232-248.
Gale, N.H. and Stos-Gale, Z.A., 1982. Bronze Age copper sources in the Mediterranean: A new Approach. Science 216, 11-19.
