ARCABOUÇO ESTRUTURAL E ASPECTOS DO TECTONISMO GERADOR E DEFORMADOR DA BACIA BAURU NO ESTADO DE SÃO PAULO

Abstract

The Late Cretaceous Bauru Basin, a tectonic unit developed in the central-southern part of the South American Platform, encompasses the sedimentary cover (with asssociated volcanic rocks) that overlies the Neocomian Paraná Flood Volcanics. The depocenter of the basin coincides with the thickest part of the volcanic pile, and this coincidence is interpreted as due to thermal subsidence. With approximately 370,000 km2 in área, the Bauru Basin is roughly elliptical with its major axis oriented NE-SW, and maximum preserved sedimentary fïll reaching up to 300 m in thickness. It is bounded by major tectonic features, namely the Rondonópolis Anteclise to the northwest, the Alto Paranaíba Uplift to the northeast, the Rio Moji-Guaçu, São Carlos-Leme and Ibitinga-Botucatu Lineaments to the east, the Paranapanema Lineament to the southeast, and the Rio Piquiri Lineament to the south. Basin development was continuous between the Santonian and Maastrichtian, and its essentially sandy sedimentary fílling represents a single sequence deposited under semi-arid conditions at the border of the basin and desertic conditions within its interior. New tectonic input started in the Maastrichtian, as evidenced in the State of São Paulo by the increasing supply of rudaceous sediments mainly associated with the Paranapanema and Ibitinga-Botucatu Lineaments and by alkaline volcanism along the Rio Moji-Guaçu Lineament, the main tectonic features along the eastern and southeastern borders of the basin, and this volcano-sedimentary episode remains compatible with syn-depositional extension tectonics. Post-sedimentary deformation is marked by two superimposed tectonic regimes of transcurrence, the later probably neotectonic, both related to the geologic megastructure of the State of São Paulo.