The sedimentology of the Kalahari group in four study areas in Northern Botswana

[摘要] ENGLISH ABSTRACT:The Kalahari Group in northern Botswana is subdivided into the Orapa, Makobaand Makgadigadi Subgroups, each with different formations. After the intrusionof kimberlites during the Late Cretaceous, a long period of weatheringand erosion set in, followed by the development of hardpan calcrete. The wetclimate was replaced by semi-arid conditions, during which the lower Kalaharisediments were deposited. During the Late Cretaceous, major depositionalbasins developed, each broken up by grabens and horsts. These grabens werefilled in by frequent flash floods eroding the horsts, followed by lacustrinesedimentation and finally saline lake conditions. During the Tertiary, along period of non-deposition, weathering and erosion denudated the landscapeby 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 lineardune systems, which were degraded, bioturbated and vegetated during subsequentwetter climatic conditions in the Holocene.

[发布机构] Stellenbosch University