Deconstructing a complex obsidian “source‐scape”: A geoarchaeological and geochemical approach in northwestern Patagonia

Abstract

Northwestern Patagonia is located in a tectonically active part of the southern Andes (Argentina), which has facilitated the formation of obsidian, including pyroclastic deposits that have been affected by geomorphic processes, resulting in a complex obsidian landscape. To date, the geomorphic relocation of obsidian in the landscape has not been a focus of systematic research, and this hampers our understanding of prehistoric human mobility. We present an updated assessment of the regional availability of different obsidian types based on results from our research program, which combines geoarchaeological survey and geochemical characterization to understand the properties and distribution of obsidian. This robust “source‐scape” provides the foundation for reconstructing patterns of lithic provisioning and discard. Our results suggest that interpretations of obsidian availability across the landscape should be more nuanced than is typically acknowledged. Based on our improved “source‐scape,” we discuss the patterns observed in an archaeological X‐ray fluorescence database. When compared with the geoarchaeological reconstruction of obsidian availability, the archaeological record conforms to a distance‐decay pattern. Contrary to previous interpretations, we suggest that the distribution of obsidian types is not isomorphic with human home ranges. This geoarchaeological research program provides a basis for integrating the archaeological record of different Andean regions.

Procurement and circulation of obsidian in the province of La Pampa, Argentina

“…This is reflected also in a variety of archaeological evidence including human bone's isotopic values, ceramic types and body ornaments among other diagnostic elements (Berón 2004;Berón et al 2017). In agreement with Barberena et al (2019), we consider that not all obsidian was obtained within the framework of such networks. In the upper section of the Colorado River small obsidian nodules from Cerro Huenul and Laguna del Maule 2 -Barrancas were identified (Fernández et al 2017).…”

“…This is because it is a raw material with a very low regional availability. Barberena et al (2019) indicate the presence of nodules from Cerro Huenul and Laguna Maule 2-Barrancas sources in the upper Colorado River basin. It is considered that the presence of small-sized rocks in the vicinity of the Tapera Moreira archaeological site could extend the availability of these obsidians to the middle basin of this river and imply a closer and, therefore, less expensive access by the hunter-gatherer groups that inhabited the south Pampas.…”

“…Maule 1 was located at Laguna Negra and along the upper Barrancas river, some 3-6 km from Laguna Negra, where it was brought by fluvial erosion. Barberena et al (2019) estimate that this subsource corresponds to the Group I Las Coloradas (Seelenfreund et al 1996). Maule 2 was located at the locality of Barrancas, in the mid to low Barrancas river and upper Colorado river basin.…”

“…Recently Barberena et al (2019) located new primary and secondary locations where obsidians match the Laguna del Maule 1 and 2 subgroups. Maule 1 was located at Laguna Negra and along the upper Barrancas river, some 3-6 km from Laguna Negra, where it was brought by fluvial erosion.…”

“…These materials are of part of ash-fall volcaniclastic deposits, and not the product of fluvial transport as those of Laguna Negra. Barberena et al (2019) use the terms Laguna del Maule 1-Laguna Negra and Laguna del Maule 2-Barrancas for these new locations (Figure 3). Three samples (12%) were characterized as Maule 1-Laguna Negra type.…”