Print this pageA Sequence Stratigraphic Correlation Across the Conjugate Margins of South America and Sub-Saharan Africa and Its Implications for Petroleum Exploration
A sequence stratigraphic correlation across the conjugate margins of South America and Sub-Saharan Africa has been undertaken based on the eustatic model developed in the Middle East and adjacent areas by Sharland et al. (2001) and Simmons et al. (2007).
We present an analysis of public domain data from across the conjugate margins of South America and Sub-Saharan Africa which demonstrates the occurrence of contemporaneous Maximum Flooding Surfaces and Sequence Boundaries, biostratigraphically constrained and expressed in wireline log responses and other well data. Some surfaces are clearly of eustatic origin, such as the widespread base Eocene flooding surface (the Palaeocene-Eocene thermal maximum, Pg20 MFS of Simmons et al., 2007) attributable to polar glacial melt. On the contrary, the post Miocene eustatic cycle is more cryptic, as uplift on the rift margins drastically increased the rate of sediment supply into the basins, creating an overall progradational parasequence stacking pattern. However, a eustatic signature is still discernable on account of the varying timescales over which tectonism and eustacy operate. As such tectonism is interpreted to either accentuate or reduce the eustatic signal, but not obscure it entirely.
The application of the sequence stratigraphic model enables the prediction of Lowstand reservoirs as well as source rock and seal deposition, often coinciding with (but not restricted to) periods of elevated global sea level, the Cenomanian-Turonian boundary (K140MFS of Simmons et al., 2007) being the clearest example. Additional factors on a regional scale, such as tectonism, palaeoclimate, provenance of the sediment supply and palaeodrainage patterns determine the characteristics of petroleum systems in individual basins and exert an influence on reservoir and source rock properties. In some instances eustatic lowstand is enhanced by uplift in the hinterland, giving rise to thick turbidite successions, for example during the Santonian compressional event (corresponding to K160SB of Simmons et al. 2007) in Ghana and Gabon.
These data clearly show that sequence stratigraphy, combined with a comprehensive set of regional geologic data taken from public domain literature provides a precise and reliable framework for correlation and mapping of the stratigrapic elements that constitute a petroleum system. This in turn allows the prediction and detailed characterisation of new plays on the Atlantic margin.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil