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Basement Control on Structural Styles and Sediment Pathways of Southeast Brazil Atlantic Margin Basins (Brazil Deep Seds—Deep-Water Sedimentation in the Southeast Brazilian Margin Project)


Milani, E.J., J.A.B. Oliveira, J. L. Dias, P. Szatmari, J.A. Cupertino, Petrobras, Rio de Janeiro, Brazil


SE-Brazil marginal basins (Santos, Campos, and Espírito Santo) hold most of the Country’s petroleum reserves known to date. These Neocomian to Recent basins developed over a Precambrian framework of cratonic nuclei that were welded along fold-and-thrust belts during the Brasiliano Cycle (0.93-0.50 Ga). Santos, Campos, and Espírito Santos basin complex evolved within a Proterozoic embayment surrounded by the continuous Congo-São Francisco craton, defining most of the basins regional structural features. The Precambrian domains crop out along the SE Brazilian coastal region and are interpreted as part of a trans­form plate margin where dextral transpressive motion was dominant during Late Proterozoic. Santos basin’s structural framework took advantage of preexisting weakness zones and its general SW-NE trend reflects this inheritance. Towards the north, the SW-NE Precambrian fabric deflects and assumes a N-S trend. The Campos basin developed in the corner, over the sintaxial domain of the Brasiliano belt. Basement heterogeneities formed structural highs and depocenters during rifting. NW-SE-trending transversal zones repre­sent first order tectonic elements in the basin. The Espírito Santo basin was accommodat­ed in a general N-S direction that runs towards NE-Brazil. Sediment pathways responsible for transferring large amount of sand to deepwater settings were strongly influenced by pre­existing structural features. Such view of basement tectonics that takes into account

Proterozoic and Mesozoic-Cenozoic evolution, provided by grav-mag data interpretation coupled with outcrop studies integrated with a large regional stratigraphic assessment via seismic interpretation allows for a more straightforward tectonic interpretation and a better control in forecasting hydrocarbon-bearing structures.