TECTONIC EVOLUTION OF THE SANTOS BASIN ANO ADJACENT CONTINENTAL AREAS

Abstract

The Santos Basin constitutes one of the Brazilian coas tal basement's largest marginal depressions, along the states of Santa Catarina, Paraná,São Paulo, and Rio de Janeiro. lts adjacent continental areais composed of a series of anastomosing crustal blocks ( Ribeira Belt - intensely re mobilized during the Brazilian cycle), which were tectonically active during the basin's evolution. The position of the Santos Basin in relation to the pole of opening led sediment deposition during the rift phase to display distinctive characteristics in comparison with the margin as a whole. An anomalous thermal uplifting in Brazil's southeastern region prior to the rupture is thought to have been responsible for changes in the rheology of the crust and upper mantle. lt is believed that during the distensive phase a large volume of continental crust was involved in the rupturing process, favoring formation of the marine feature known as the São Paulo Plateau. Potential detachment planes must have taken form during the rupture, taking advantage of the Ribeira Fold Belt discontinuities. As a consequence, the continental area adjacent to the basin underwent a good deal of tectonic movement, resulting in the formation of a broad topographically-elevated (through flexural effects) region which may be called "prato-Serra do Mar". During the MesolNeo-Cretaceous and Tertiary, thisregion presented strong tectonic pulsations which resulted in the formation of the Taubaté, Resende, etc. basins and accumulations of the thick Santos Formation sedimentary packages in the San tos Basin. Numerous turbidictic pulses in this basin are also a result of tectonic movements in the adjacent continental area.