Obsidian in the Dásovich rock-shelter, Chubut, Argentina: Implications for long-distance acquisition behavoirs

Abstract

In the Dásovich rock-shelter, southwest Chubut, Argentina, obsidian artifacts make up >50% of all the artifacts encountered. Although absent from the earliest Late Pleistocene (≥11,800 cal yrs BP) occupational level in the site, they do begin to occur in the Early Holocene (≥10,500 cal yrs BP). Obsidian is again absent from a younger Early Holocene (~8500 cal yrs BP) level, but reappears in high abundance (≥36% of all artifacts in each level and ~56% overall) in Middle and Late Holocene layers just below and overlying a 4–14 cm thick tephra layer produced by the H2 eruption of Hudson volcano at ~3870 cal yrs BP. We analyzed 19 of the 146 obsidian artifacts found in the site, including all 7 artifacts from the Early Holocene. Obsidian artifacts in the Early Holocene are derived from both a relatively local source (CIS-type from the Cisnes river valley ~120 to the northwest) and from a more remote source (PDA-types from Pampa del Asador ~270 km to the south). Only obsidian derived from remote sources (11 from PDA and 1 S-type from Sacanana ~400 km to the northeast) are found in the younger Middle and Late Holocene levels. The high abundance in the Middle and Late Holocene of obsidian derived from sources beyond the normal range for direct procurement by Patagonian hunter-gatherers (<150 km) suggests that this site may have been the locus of significant trade activity, consistent with its location close to the intersection of both historic trade routes and those previously proposed for the northward transport of PDA-type obsidian and southwestward transport of S-type obsidian. This activity began before the deposition of the tephra from the explosive H2 eruption of the Hudson volcano, which apparently did not produce any discontinuity in access to or use of obsidian in the area.