Abstract
In the Pilauco site (40°34′11″ S, 73°06′17″ W; 13,570 ± 70–12,540 ± 90 14C year BP), a previous geochemical trace analysis suggested that the Puyehue-Cordón Caulle Volcanic Complex is the most likely source for obsidian and dacitic glass artifacts at Pilauco. It was hypothesized that the glassy rocks were probably collected from a pebble beach deposit, as deduced by the presence of crescentic percussion marks on the artefact cortexes. An experimental study was designed using pebble obsidian clasts. Bidirectional transport produced by the waves on a beach was imitated by an oscillating table, using time lapses equivalent to a transport of 0.7 to 20 km. One hundred clasts were randomly selected and marked. The morphological changes were registered, measured and photographed after seven sequential runs. At the end of the experiment at 20 km, the mass loss of rounded and fractured clasts was 5% and 11%, respectively. Crescent, circular, pseudo-circular and irregular percussion marks occurred in both types of clasts. In all cases, the crescent marks developed a pseudo-frosted surface appearance, giving a whiter tone that masks the black color of the obsidian, exactly as observed in the cortex of the artifacts knapped in dacitic glass at the Pilauco site. Thus, it is highly probable that the vitreous material was obtained from a beach sourced by the Puyehue-Cordón Caulle Volcanic Complex.
Highlights
The Pilauco paleontological and archaeological site is located in the Central Depression of northwestern Chilean Patagonia, west of the Andes Mountains, in the city of Osorno, Región de los Lagos (40◦ 340 S–73◦ 070 W; Figure 1)
The the volcanic glasses used in this experiment correspond to obsidian [44] and the archaevolcanic glasses used in this experiment correspond to obsidian [44] and the archaeologiological materials are dacitic glasses [9], it is very unlikely that the small differences in cal materials are dacitic glasses [9], it is very unlikely that the small differences in chemical chemical composition (e.g., Ba and Zr concentrations [9]) between the two types of glasses composition (e.g., Ba and Zr concentrations [9]) between the two types of glasses originate originate any difference in the production of impact marks, regardless of the sedimentary any difference in the production of impact marks, regardless of the sedimentary environenvironment
The other marks, clustered and isolated crescentic marks (Figure 6C,D), and and the more frequent bladed shape of the obsidian clasts suggests that they acquired the bladed shape obsidian suggests that they acquired their theirmore shapefrequent and impact marks dueof tothe transport on clasts the shores of a paleolake, recording shape and impact marks due to transport on the shores of a paleolake, recording ancient higher levels of the present Laguna Blanca [43]
Summary
The Pilauco paleontological and archaeological site is located in the Central Depression of northwestern Chilean Patagonia, west of the Andes Mountains, in the city of Osorno, Región de los Lagos (40◦ 340 S–73◦ 070 W; Figure 1). It is one of the most important and oldest Late Pleistocene sites in Chile [1–6]. The research conducted at the Pilauco site has been approached from several disciplines, i.e., geology, paleontology, paleobotany, archaeology and astrophysics, with a transdisciplinary strategy [8–12]. During the Late Pleistocene, the human settlement of South America through the Bering Strait became one of the most inspiring research issues for archaeology ([1,2] and references therein). South American archaeology has strongly focused on understanding the relationship between early Americans and their natural environment [3–6,9,13–15]
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