Valerie Nxumalo1, Eric M. Roberts2, and Johann Neveling3
1Central Regions, Council for Geoscience, Pretoria, South Africa
2Geology, University of the Witwatersrand, Johannesburg, South Africa
3Central Regions, Council for Geoscience, Pretoria, South Africa
The Kalahari-Karoo Basin in southwest Botswana, southeast Namibia and northern Cape Province of South Africa, including the poorly understood Gemsbok Sub-basin, preserves a laterally heterogeneous sequence of late Palaeozoic to mid Mesozoic sedimentary and volcanic rocks of the Karoo Supergroup. A new project aimed at correlating existing cores across the Kalahari-Karoo Basin will provide significant new insight to the tectonic and sedimentary history of the region.
Preliminary analysis of existing core, restricted field mapping, and interpretation of available geophysical data in the Gemsbok Sub-basin suggests that deposition was likely influenced by tectonic activity of large, regional structural features, particularly the Kalahari Line. The Kalahari Line is interpreted to be a mid-Proterozoic rift which is separated from the Kaapvaal Craton in the east by a north-south belt of the Kheis Terrane and it is defined as a geophysical lineament along the 22 degree east meridian in the Kalahari-Karoo Basin, and separates the deep magnetic basement to the west from shallow basement to the east.
Investigations of the impact of the Kalahari Line and the tectonic development of the Kalahari-Karoo basin are ongoing. Preliminary work suggests that reactivation of this lineament resulted in differences in subsidence rates and resulting thicknesses and facies distribution of stratigraphic units observed within the basin. Ultimately, this investigation will result in a 3D stratigraphic model of the Kalahari-Karoo Basin in the Gemsbok Sub-basin that will improve our ability to predict the sub-surface distribution and quality of both economic coal deposits and aquifers.