A COMBINED APPROACH TO LITHIC SOURCE IDENTIFICATION BASED ON GEOSTATISTICAL MODELS OF ARTIFACT DISTRIBUTIONS AND PETROGRAPHIC ANALYSIS: AN EXAMPLE FROM EAST-CENTRAL ARGENTINA

LUCIANA CATELLA, GUSTAVO BARRIENTOS, MARCELO MANASSERO AND FERNANDO OLIVA

Barcelona

Simposio; 10 International Symposium on Knappable material on the rocks; 2015

Universidad de Barcelona

Auxilliary sciences: Session 6 Characterising lithic sources A COMBINED APPROACH TO LITHIC SOURCE IDENTIFICATION BASED ON GEOSTATISTICAL MODELS OF ARTIFACT DISTRIBUTIONS AND PETROGRAPHIC ANALYSIS: AN EXAMPLE FROM EAST-CENTRAL ARGENTINA Luciana Catella, Gustavo Barrientos, Marcelo Manassero and Fernando Oliva Our study area, the Chasicó river basin (Buenos Aires province), is located in the eastern portion of east-central Argentina (35.5°-41.5° S; 56.5°-67.5° W) (Figure 1). This ample region includes a significant section of the Pampas and the northeast of Patagonia. The former is a flat to slightly undulating surface landscape interrupted by two major orographic systems, Tandilia and Ventania, smaller hilly ranges, and a number of isolated hills and scattered rocky outcrops. The latter is a semiarid region located south of the Colorado River, in which rocky outcrops are scarce and isolated, being the most relevant geologic feature the Patagonian Shingle Formation, composed of gravel deposits of extraregional (i.e. Andean) provenance. In east-central Argentina, there were two main kinds of raw materials used by prehistoric hunter-gatherers for tool-making: quartzites (orthoquartzites and methaquartzites) and cryptocrystalline quartz (e.g., chalcedonies, jaspers, cherts, silicified dolomite). Other rocks like basalts, rhyolites, limestones, silicified tuffs, granites, or sandstones were also available, but they seem to have been of second order importance for subsistence activities. Among the siliceous rocks, one widely used was a silicified oolitic limestone informally called ?siliceous chert?. The main sources of this rock are located at Meseta del Fresco, a basaltic plateau placed in the southwestern extreme of La Pampa province, about 400 km northwest from our study area. A number of some minor outcrops (e.g. El Carancho) have also been described in the literature, which are located about 200 km northwest from our study area. This toolstone is represented in the artifact assemblages of the lower Chasicó basin with frequencies between 10% and 20%, higher than expected considering the distance from the main sources, as well as the relative frequency values in the surrounding areas. With the aim of evaluating the presence of closer, alternative sources of siliceous chert which could explain the high observed frequency values of this rock in the artifact assemblages from our study area, we are currently performing a set of studies based on a combination of spatial modeling and of petrographic analyses of geological and archaeological samples. Geostatistical models of relative frequency data (i.e. percentage representation of toolstone classes in georeferenced artifact assemblages) constructed using kriging interpolation, provide relevant clues about source location, to the extent that significant peaks of frequency in continuous surfaces are expected to occur at or near the sources. Peaks of frequency that not coincide with the location of some previously described source alert about the presence of an undetected supply area (Barrientos et al. 2014). This help to plan problem-oriented surveys and to implement more analytical sourcing activities, like those based on petrographic analysis. It is expected that the data and analyses presented in this exploratory study will illustrate well both the strengths and limitations of the advocated approach, thus encouraging future theoretical, methodological, and empirical research on the subject. Acknowledgements: This research was supported by grants from CONICET (PIP-11220120100622CO) and Universidad Nacional de La Plata (N740). References Barrientos, G., L. Catella and F. Oliva. 2014. The spatial structure of lithic landscapes: The Late Holocene record of east-central Argentina as a case study. Journal of Archaeological Method and Theory. Online First. DOI 10.1007/s10816-014-9220-0.