Crustal thickness map of Brazil: Data compilation and main features

Abstract

We present a crustal thickness map of Brazil and adjacent areas based on a compilation of data published in the literature as well as new measurements. We used crustal thicknesses mainly derived from seismic datasets such as deep seismic refraction experiments, receiver function analyses, and surface-wave dispersion velocities. Crustal thicknesses derived from modelling gravity anomalies commonly depend on assumptions, such as constant density contrast across the Moho interface, which are not always easily verifiable and were considered only along the continental shelf to fill large gaps in the seismic data. Our compilation shows that the crust in the stable continental area onshore has an average thickness of 39 ± 5 km (1-σ deviation) and that no clear difference can be observed between low altitude, intracratonic sedimentary basins, NeoProterozoic foldbelts (except for the Borborema Province), and cratonic areas. The thinnest crust is found in the Borborema Province of NE Brazil (30–35 km) and along a narrow belt within Tocantins Province (∼35 km), roughly parallel to the Eastern border of the Amazon craton, while the thickest crust is found in the Amazon and São Francisco cratons (41 ± 4 km), and the Paraná Basin (42 ± 4 km). Both the Ponta Grossa and the Rio Grande Arches are areas of thinned crust, and the western border of the Brazilian platform, near the sub-Andean region, seems to be characterized by a crustal thickness of less than 40 km. Although sparse in data coverage, we expect the resulting crustal thickness map to be useful for future studies of isostasy, dynamic topography, and crustal evolution of the country.