Site formation processes and paleoenvironmental evolution of Formative archaeological sites from northwest Argentina

SAMPIETRO VATTUONE, M. M.; J. M. SAYAGO

Arica - Chile

Conferencia; 2nd Southern Deserts Conference “Human - Environment Interactions in Southern Hemisphere Deserts: Past, Present and Future”; 2005

The purpose of this paper is to relate the archaeological formation processes from a high altitude valley with the paleoenvironmental sequence representative of the semi arid environmental conditions from Formative to Regional Developments periods. The archaeological sites considered belongs to Formative period, and were dated between 360 BC and 800 AC. They are characterized by the presence of circular residential units and agricultural constructions.                 Over the bases of previous mapped and prospected areas we selected 20 locations from different archaeological and geomorphological contexts to made excavations. All profiles were described from a pedological and archaeological point of view, and all sampled materials were analyzed on laboratory taking into account texture, organic matter, structure, and pH. Two of them were sampled for micromorphological studies. In all profiles we found two depositional cycles, the older, at 60 to 80 cm deepness, was dated on 2480 ± 110 BP (GRN 21783). Pedological characteristics suggest that it was a more humid period, and the archaeological materials showed that it was the original occupational surface. These environmental conditions probably regionally favored the settlement of most of the Formative cultures at northwest Argentina. The transition between the paleosol and the actual soil is represented by an erosion surface coincident with a regional arid period that was suggestively contemporaneous with the transition between the Formative and the Regional Developments period with the corresponding change in the sociopolitical organization. Micromophological analysis showed that in both profiles, sediment deposition seems to have been slow with the permanent development of vegetation at the surface, even at the contact between soil and paleosol.