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From oceanic crust to exhumed mantle: a 40 year (1970–2010) perspective on the nature of crust under the Santos Basin, SE Brazil

Abstract The first comprehensive geological and geophysical surveys of the Brazilian continental margin during the 1970s recognized the crust in the SE Brazilian basins as ‘anomalous’ but models for the opening of the South Atlantic proposed at that time invoked a very narrow continent–ocean transition. Nevertheless, such studies established the presence of a thick sedimentary prism, including an extensive salt layer under the São Paulo Plateau. The earliest reconstructions for the South Atlantic invoked a seaward shift of the spreading axis to account for the asymmetric widths of the salt layer between the Brazilian margin and its conjugate in offshore Africa. Although our understanding of continent–ocean transition has progressed since then, direct seismic imaging at crustal scale has only been possible recently through long offset (10 km), deep recording (18 s), pre-stack depth migrated (PSDM) to 40 km, seismic-reflection data. These data allow us to generally image the Moho from under thick continental crust (>30 km) to thin oceanic crust (c. 5 km). Although the nature of the transitional crust is still contested, these seismic data allow for constraints on various models for continent–ocean transition. Future integrated studies utilizing PSDM and refraction-seismic data will further refine these models.