Estrategias de aprovisionamiento y utilización de las materias primas líticas en el campo volcánico Pali Aike (Pcia. Santa Cruz, Argentina)

JUDITH CHARLIN

Archaeopress, British Archaeological Reports, International Series 1901

Lugar: Oxford; Año: 2009 p. 240

9781407303833

The main goal of our research is the study of the strategies of provisioning and utilization of lithic raw materials within the Pali Aike volcanic field (PAVF), Santa Cruz Province, Argentina (South America). On this basis, we analyze the land-use patterns and home ranges of the human populations that inhabited this region during the Late Holocene (ca. last 4000 years BP). In order to do this, it is necessary to know if the different types of rocks used for manufacturing lithic artifacts were obtained by direct or indirect procurement (Renfrew 1977, Torrence 1984, Meltzer 1989, Ingbar 1994). Along with this, it is important to evaluate if there are diachronic changes in the provisioning and use strategies of lithic raw materials. Previous archaeological research in this region suggests that basalt is the rock most usually used for artifact manufacture (Sanguinetti de Bórmida 1976, 1982, 1984; Gómez Otero & Fontanella 1980; Massone & Hidalgo 1981; Nami 1984a, 1984b, 1986; Gómez Otero 1986-87, 1989-90; Prieto 1989-90, 1997, among others). Geological information indicates that the volcanic outcrops of Pali Aike correspond to an alkaline basalt (Skewes 1978, Corbella 2002, D’Orazio et al. 2000 y 2004, Agostini et al. 1999). However, the geochemical analysis of archaeological artifacts macroscopically similar to basalt shows that none of the analyzed samples corresponds to the Pali Aike’s outcrops (D’Orazio pers. com. 2003). Therefore, these outcrops were not used as sources of lithic raw material, and this is possibly due to the their low quality. The thin-section analyses made on lithic artifacts manufactured on macroscopically similar black rocks show that, in fact, they represent different petrographic types of fine grain rocks that includ basalt, dacite, ftanite, and shale, among others. These rocks are difficult to differentiate without a microscope, and were called  “fine-grained dark rocks”. In order to study the distribution and abundance of these different rock types on the landscape we follow the methodology outlined by Franco & Borrero (1999). This sampling strategy was designed to deal with secondary lithic deposits (sensu Nami 1985), which were the main prehistoric procurement source of rocks within the study area. This survey methodology consists in a number of people collecting appropriate rocks available at a selected location for a controlled amount of time. This strategy allows us to assess the return of different potential lithic sources, analyzing their diversity in terms of petrography, nodule sizes, and quality for the manufacture of artifacts, among other factors. The regional sampling of the available lithic sources indicates that the fine-grained dark rocks are actually scarce and come from spatially restricted places. They are available on the Gallegos river basin, in the margins of some lagoons between the Gallegos and Chico rivers, on the northern coast of the Magellan Strait, and in some places in the southern Atlantic coast of the Santa Cruz Province.The availability of lithic resources in the Pali Aike volcanic field provides the frame of reference to evaluate the intensity of lithic artifacts reduction. At a regional scale, it helps to understand the provisioning and technological strategies. We follow a materialist and non-typological perspective for the analysis of lithic artifacts (Hiscock 2007). The degree of exploitation of different lithic raw materials is evaluated according to several reduction variables. The rock-type by class of artifact (debris, unifacial tools, bifacial tool, and cores) is the unit of comparison. We applied several reduction indexes, including: flake-scar density in debris (Ingbar et al. 1989) and cores; tools residual length (Kuhn 2004); unifacial tools geometric index of reduction (Kuhn 1990) and estimated wear angle measured on retouched edges; reactivation index in bifacial tools (Iriarte 1995), and rate of retouched edges and points by artifact.The spatial patterns of explotaiton of lithic raw materials show an increase in the reduction intensity of artifacts in relation with the distance from the main permanent potential sources: the Gallegos river, to the north of the PAVF, and the Strait of Magellan, to the south. The central area of the PAVF is located at the largest distances from the main potential lithic sources. Accordingly, the artifacts recovered in this area show the highest levels of utility consumption recorded regionally. The variability recorded in the degree of reduction at this place suggests that some rocks were obtained nearby, so probably the lagoons located between the Gallegos and Chico rivers also functioned as potential sources. The lithic analyses conducted indicate that there are spatial differences in the density of artifacts, provisioning strategies, and use of lithic raw materials between the sites located to the north and south of the Chico river, like Las Buitreras 1 and Cóndor 1 caves respectively. If we consider the distribution of maritime resources in the hinterland of the PAVF, the values of stable isotopes in human bones, and the archaeofaunistic evidences, it is possible to segment the PAVF in terms of differences in the human occupational intensity at a regional scale. The case-study presented here contributes with a methodology of lithic analysis that is regional and non-typological, which has the pontential to be implemented in other areas of the world and with other specific research goals.