PETROGRAPHIC AND STRUCTURAL CHARACTERIZATION OF THE LAVA FLOWS AT VOLTA GRANDE IN THE UPPER URUGUAY RIVER, SOUTHERN OF BRAZIL

Abstract

The Volta Grande in the Upper Uruguai River is an important area for understanding precolonial human occupations in the context of southern Brazil. In this area, archaeological sites are excavated by the POPARU project, where the material culture (lithic and ceramic materials) present in the occupations of the last 12,000 years BP was identified and described. In the lithic industry, raw materials are still an open question and, initially, hypotheses were raised that they are raw materials obtained in a local context. In this work, the lava flows were investigated and characterized, in order to recognize the local lithology and eventual sources of raw materials. The following lithofacies were identified: facies with segregation structures (Bv), aphanitic volcanic facies with sparse vesicles (Bam, Bvc), columnar aphanitic to hypocrystalline volcanic facies (Bac), Basaltic Autobreccia facies (Br) and Mafic Volcanoclastic Deposits (MVD). The MVD stand out for constituting a wide variability of volcano-sedimentary interaction features that may have been used as a source of raw material, although they are relatively different from those found in the lithic collections of the archaeological sites of the VGUR.

Keywords: Archaeology. Raw materials. Serra Geral.