Print this pageRift Evolution and Paleogeography of the Greater Campos Basin
The extension between West Africa and Brazil occurred during the Early Cretaceous as a series of rift pulses with varying duration that culminated with the South Atlantic sea floor spreading. It has been suggested that the West African margin rifting occurred in three discrete phases, each phase having its own particular deformation style ranging from Barremian to early Aptian. Each rift phase is recorded by an onlap surface followed by an overall regressive package representing the subsequent infilling of the basin. The rift phases in the Greater Campos Basin, especially in the Santos Basin, have not been characterized in the literature and they are not so distinct. Synrift structures are characterized clearly by half-grabens but the infilling strata geometry is often made up by parallel seismic reflectors over large areas indicating the influence of thermal like subsidence during the expected rift phase. One objective of this work is to describe basic aspects of the rift phases in the Greater Campos and to define its paleogeography at the end of the rifting period. Each rift pulse resulted in the formation of deep lows and structural highs. The most prominent intra-basinal high is a regional basement structure in deep water Santos Basin that forms >10,000 km2 closed structure at the Aptian level, encompassing the most recent giant hydrocarbon discoveries made in Brazil. As observed in this prominent high, many basinward highs were often away from the siliciclastic input derived from the basin margins, becoming clastic-starved environments that favored the development of broad shallow water carbonate platform during the Aptian. The restricted sea water input and water level variations due to climatic fluctuations played important role on reservoir facies deposition and diagenetic processes. The compartmentalization of the basin into intra-basinal highs and lows favored also the development of anoxic conditions in the lacustrine system, hence affecting source rock thickness, distribution and quality. Therefore, the restoration of the paleogeography during the Barremian to Aptian times has strong implications for lake connectivity, water chemistry, and source rock and reservoir distribution and quality. Regarding the Greater Campos Basin, basic aspects of its evolution and paleogeography at time of rifting and sag are still poorly understood.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil