Difficulties and results in the assessment of lithic raw material availability: two cases from South Patagonia (Argentina).

FRANCO, NORA VIVIANA; VETRISANO, LUCAS

Barcelona

Congreso; 10th International Symposium on Knappable Materials; 2015

Universidad de Barcelona

In order to understand how raw materials are obtained, used and exchanged, a goodknowledge of the regional lithic resource base is needed. The degree of difficulty in obtaining the necessary information would vary in relationship to geological processes affecting different regions. It should be pointed out that studies about the resource base have centered on primary sources. However, humans have frequently used secondary sources.Here we will analyse two cases from south Patagonia in which the understanding of thelithic resource base presents different difficulties: the southern Santa Cruz River and north of the Chico River. While both areas were affected by glacial processes and present a vast majority of siliceous secondary sources, the second one is much more heterogeneous, which different availability of rocks in areas located at less than 1 km apart. This poses a problem because geochemical analysis is of limited utility and a high amount of sampling is required.Studies carried out along the Santa Cruz River have shown that dacites are the most frequentrocks of good quality, both in the upper and the lower courses of the river. In the upper course, the way in which they were utilized changed between the Middle and Late Holocene, something that may be the result of changes in the way the area was used or the movement of different populations with different technological choices. The introduction of different varieties of obsidian has been recorded in the area, as well as changes in the way they were used. Exotic black obsidian was at first a part of the transported individual tool-kit, and afterwards it was incorporated into ensembles probably by exchange. Grey-green banded obsidian was circulated in the area since the early Holocene but was only part of mortuary contexts during the late Holocene.The situation north of the Chico River is more complex. Not only have the studiesbegun only a short time ago but there is a high and punctuated availability of siliceous rocks. Efforts have been carried out in order to register this variability and first tendencies in the utilization of immediately available and non-local rocks have been recorded. Studies carried out in the area have also shown the existence of a new secondary source of black obsidian, extending the distribution of this raw material well to the east. Lithic characteristics,however, have allowed for the recognition of the utilization of the primary lithic source by ca. 8000 years B.P.