Slope 4: Karoo Synthesis Project

Karoo Basin. Slope 4 study area.
Map of southern Africa showing the outline of the Karoo Basin. Slope 4 study area is highlighted in red.

Geological context of the slope projects

The Karoo Basin is one of a series of retroarc basins that formed in response to subduction of the Panthalassan Ocean beneath the southern margin of the Gondwanan continent. Slow subsidence is attributed to long wavelength dynamic loads driven by the subducting plate (Tankard et al. 2009).  Permian Ecca Group fill of the western Karoo Basin details a gradually shallowing environment from the deepwater basin floor deposits of the Laingsburg Formation to the Terrestrial fluvial deposits of the Beaufort Group. Deposition took place on a NW-SE trending clastic margin that prograded eastwards into deeper water. Paleocurrent was maintained in a NE to E direction throughout.  Present day exposure of the Ecca Group within the Laingsburg depocentre occurs along the limbs of a series of E-W trending open folds attributed to latest Permian / Triassic formation of the Cape Fold Belt. The distribution of outcrop facilitates both downdip and strike investigation of the depositional systems. 

Slope phase 1, 2 and 3

Field work in the Tanqua and Laingsburg depocentres (Karoo Basin, South Africa) has generated a dataset covering some 7500 km2, comparable in extent to exploration datasets used in the hydrocarbon industry. The 1800 m thick basin plain to earliest fluvial succession has been mapped over this area through a combination of stratigraphic correlation within more that 1000 logged sections and the 'walking out' of stratigraphic surfaces. The dataset provides unprecedented detail on the distribution of depositional environments and associated sedimentary facies from shelf edge to the distal fringes of submarine fan systems.  

For more detail on the formation and subsequent fill of the Karoo Basin see the Karoo Geology section.

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