Geoarchaeology in a Pampean alluvial sequence: evaluating natural formation processes in guanaco bone assemblages from Paso Otero 1 site (Pampean region, Argentina).

FAVIER DUBOIS, C.; KAUFMANN, C. A; GUTIÉRREZ, M. A.

Saint John, NB, Canada.

Congreso; DIG - Developing International Geoarchaeology; 2005

Paso Otero 1 is a stratified riverine site in the middle valley of the Quequén Grande river (Buenos Aires Province, Argentina). This site contained four guanaco (Lama guanicoe) bone concentrations (piles) located in two different stratigraphic levels, interpreted as a result of kill/butchering activities in previous works. The containing units, buried A horizons, were dated in ca. 4800 and ca. 3000 14C yr BP indicating middle and late Holocene events recording very similar assemblages. Geoarchaeological and taphonomic research was carried out to evaluate formation processes at the site emphasizing the stratigraphic and paleoenvironmental context of bone concentrations. The stratigraphic analysis demonstrated that both, lower and upper piles, are linked with two major erosive discordances recorded at the site, produced by turbulent floods. The deposit containing the lower piles correspond to lacustrine facies that actually overlies, through the discordance, a poorly-drained soil which was originally interpreted as the matrix of the ssemblage. In a similar way the upper discordance erode the soil horizon formerly interpreted as the stable surface where the bones were placed. Taphonomic analysis was carried out in the lower deposit considering different lines of evidence. The results suggest that the majority of bone elements were articulated at the time of the initial deposition and that the bones were accumulated by hydrologic processes. Although the causes of guanaco´s deaths are unknown, it is inferred that the bone assemblage represents several events of natural mortality induced by processes not yet fully understood (i.e. unusual flooding or drought). The scarcity of cultural modifications recorded suggests that some of the guanaco bones belonged to carcasses processed by hunter-gatherers nearby the site. As a consequence, Paso Otero 1 represents a mix of materials of natural and cultural origins.