Resolving Tectonic Subsidence from Quantitative Basin Modeling: Karoo Basin, South Africa

Matthew McKay
West Virginia University, Department of Geology and Geography Morgantown, WV, USA
[email protected]

The Karoo basin records Carboniferous-Jurassic sedimentation that was likely controlled by subduction along the Gondwanan margin. Subsidence of the Karoo basin has historically been attributed to lithospheric flexure during crustal loading of the Cape Fold Belt to the south. Recent geophysical studies, however, propose that subsidence is controlled by basement block displacement driven by mantle-flow. This new model suggests that deformation of the Cape Fold belt is not required to generate ~5 km of Permian accommodation within the Karoo; therefore, the morphology of the basin may be such that petroleum generation potential may exist in areas previously thought to be supermature.

To resolve the tectonic and thermal history of the Karoo basin, I propose to integrate stratigraphic surveys, geochemistry, geochronology, thermochronology, and peak-burial temperature estimates to create quantitative 1-D basin models for locations across the basin, focusing on marine and terrestrial sections that include turbidite, deltaic, and fluvial sequences. Deposition and cooling ages from different heights throughout measured stratigraphic sections can be chronologically correlated, then extrapolated across the basin to produce geospatial models of paleo-geothermal gradient, heat flow, burial/exhumation rates, and thermal maturation throughout the history of the basin. These results will provide insight into the degree of basement control on basin development by investigating the temporal and spatial relationships between basement architecture and the development of the basin. Additionally, the timing of subsidence in the basin will be compared to the timing of deformation in the adjacent Cape Fold Belt to assess the relationship between deformation and subsidence.

AAPG Search and Discovery Article #90157©2012 AAPG Foundation 2012 Grants-in-Aid Projects