Influence of basement structures on the evolution of the major sedimentary basins of Brazil: A case of tectonic heritage

Abstract The present study deals with the correlation between the geotectonic features of the basement and the internal structure, shape, geologic evolution, etc. of the major sedimentary basins of the South American platform. The Parana, Parnaiba and Amazonas basins occupy an area of the order of 3.6 × 10 6 km 2 , and their sedimentary cratonic sequences were deposited from Silurian to Triassic times. Subsidence rates are estimated around 15 m/Ma in the main depocenters. A geologic study was carried out along the basement features in the surroundings of such basins in order to identify the major structural, geotectonic and geochronological discontinuities. The extension of these basement characteristics towards the interior of the basins are examined. Basement core samples from deep wells were investigated through petrological and geochronological analyses, and pre-existing geophysical and structural maps of those basins were taken again into consideration. It can be concluded that many of the identified basement discontinuities display a direct influence on the depositional history of the basins as well as on their internal subdivisions and external outlines. Basement structures generated during the late Precambrian Brasiliano Cycle turned out to be particularly important. The Parana and Parnaiba basins are considered to represent cratonic basins, located on rigid lithosphere, tectonically stabilized in the latest Precambrian/early Palaeozoic, and their subsidence is attributed to the establishement of some initial rifted grabens. The Amazonas basin is more complex and includes three large sub-basins with distinct evolutions, each located on a different tectonic segment of the basement.