Inverse Flexural Basin and Forward Stratigraphic Modeling of the Brazilian Continental Margin (Campos, Santos, and Pelotas Basins)

The Campos, Santos and Pelotas segments of the Brazil continental margin show significant variations in basin architecture and infill during passive margin development, in spite of their closely related syn-rift record. Based on 2D seismic and well data, the Barremian-Holocene basin fill has been analysed by high-resolution sequence stratigraphy and inverse flexural basin modeling. The results provide key input parameters and bounding conditions for forward stratigraphic modeling. Iterative batch modeling and sensitivity analyses provide a best-fit numerical model for the current basin configuration. Forward modeling results confirm the individual crustal evolution and subsidence trends in each of the three margin segments. Late Barremian to Late Aptian depth-dependent continental stretching generated sag basins with evaporite deposition on the Santos and Campos margin segments. The thermal effect of heat advection beneath the thinned continental crust delayed crustal subsidence and generated sag-salt depocenters with largely constant subsidence rates. In contrast, the Pelotas Basin features thickened high-density volcanic crust, controlled by long-term post-rift thermal contraction and differential sediment accommodation. For the Albian post-rift to Holocene drift development, the most important controls on basin architecture and infill include: (i) increasing flexural subsidence superimposed on decreasing thermo-tectonic subsidence; (ii) episodic rejuvenation of sediment source areas affected sediment input and flexural loading, triggering coastal progradation and turbidites; (iii) basinward tilting and landward flexural rebound was associated to shelfal erosion, sediment bypass and downslope mass transport; (iv) salt remobilization triggered shelf instability, basin-floor topography and lithofacies distribution; (v) bottom-currents strongly redistributed the Deepwater deposits. The integration of offshore seismic and well data with onshore data in stratigraphic modeling improves the understanding of source-to-sink processes, shelf-to-basin depositional systems, lithofacies heterogeneities and reservoir distribution on the Brazilian continental margin. Integrated numerical modeling provides a coherent model for the evolution of the Early Cretaceous rift-, sag-, and salt basins. It also improves the understanding of the strong lateral heterogeneities on the Late Cretaceous to Neogene passive margin.  

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California