Browsing by Author "Du Plessis, Pieter Igenatius"
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- ItemThe sedimentology of the Kalahari group in four study areas in Northern Botswana(Stellenbosch : Stellenbosch University, 1993-11) Du Plessis, Pieter Igenatius; Le Roux, J. P.; Stellenbosch University. Faculty of Science. Department of Earth Sciences.ENGLISH ABSTRACT: The Kalahari Group in northern Botswana is subdivided into the Orapa, Makoba and Makgadigadi Subgroups, each with different formations. After the intrusion of kimberlites during the Late Cretaceous, a long period of weathering and erosion set in, followed by the development of hardpan calcrete. The wet climate was replaced by semi-arid conditions, during which the lower Kalahari sediments were deposited. During the Late Cretaceous, major depositional basins developed, each broken up by grabens and horsts. These grabens were filled in by frequent flash floods eroding the horsts, followed by lacustrine sedimentation and finally saline lake conditions. During the Tertiary, a long period of non-deposition, weathering and erosion denudated the landscape by more than 25m in some areas, forming the Letlhakane Stoneline Formation. Regional calcretes formed subsequently vary in age from Miocene to Pleistocene. In the early Holocene, arid conditions resulted in the formation of linear dune systems, which were degraded, bioturbated and vegetated during subsequent wetter climatic conditions in the Holocene.