The hunter-gatherer site BES II (Jacaré-Gua?u River low terraces, central Sao Paulo state, Brazil): Interface with geomorphical and environmental fluctuations of the Pleistocene-Holocene transition

摘要

The lithic site Boa Esperan?a II (BES II), in the S?o Paulo segment of the Brazilian Plateau, next to the boundary between the cities of Araraquara (SP) and Boa Esperan?a do Sul (SP), presents a collection of almost 2,000 lithic artifacts (predominantly chert and sandstone), being interpreted as a settlement of diversified functions with possibly continuous or successive occupation. In this work, we approach the site based on interface of its insertion in the regional physical-environmental context - with emphasis on the interface with relief frames, surface structure study and estimated geomorphic sequences of the alluvial plain of Jacaré-Gua?u river - and techno-typological analysis. It was verified that the BES II artifacts are distributed along vertical profiles and relief pictures lined by records that mark the transition from semi-arid conditions to others of increasing humidity, successive oscillations of base levels and modifications of fluvial regimes (ephemeral channels passing to perennial channels of different hydrological meandrings patterns), indicating that human occupation has dealt with conditions of quite distinct landscapes between the Late Pleistocene and the Holocene. Local lithic industry would have taken advantage of attributes derived from these modifications in the landscape over time - in particular the exposure of gravels of large river pebbles deposited by torrential ephemeral channels. The past  abundance of raw material of fluvial origin would have contributed to the location of the site in the regional geomorphological context, as well as for a lithic assemblage based on the production of large unipolar flakes. We observed in the correlations between the position of artifacts, geomorphical and pedological data, OSL and Carbone-14 dates at archaeological levels, elements that allow us to discuss considering BES II as an archaeological site to integrate the interval of the Pleistocene-Holocene transition and to had interfaces with the geomorphological and environmental changes of such time. The archaeological implications of the issue and the fact that only one dating of photoluminescence has been reported from the deepest level of the site (basal gravel layer) emphasize the need for new, denser and more diversified studies.