Stratigraphic analysis of the Camaquã group facies, provenance and paleocurrents (Proterozoic-Fanerozoic tectonic-sedimentary evolution of the Camaquã Basin, RS

Abstract

The open pit of the Uruguai Mine, in the Minas do Camaquã region, presents the best exposures of the Camaquã Group. Stratigraphic analysis of facies, paleocurrents and provenance show that the Camaquã Group deposits are organized in two lithostratigraphic units: Rhythmites and Sandstones at the base of the exposure and Conglomerates and Sandstones at the top. The top unit was divided by the CBC (Companhia Brasileira do Cobre) team into three sub-units: Lower Conglomerate, Intermediate Sandstone and Upper Conglomerate. The Rhythmites and Sandstones unit is represented by marine turbidites and sandstones of shallow water and transitional environments. The Lower Conglomerate unit is composed mainly by pebbly conglomerates and sandstones formed in subaqueous fans. Provenance and paleocurrents analysis of these two units indicate source áreas composed of volcanic acid rocks, granites and metamorphic rocks located S and SW. The Upper Conglomerate is composed by cobble and boulder conglomerates of alluvial fan environment, derived from mylonites and granites located SE and reworked sedimentary rocks of the lower units of the Camaquâ Group.