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

Du Plessis, P. I.(Pieter Igenatius) (1993)

Thesis (M. Sc.) -- University of Stellenbosch, 1993.

Thesis

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.

AFRIKAANSE OPSOMMING: Dre Kalaharigroep in noord-Botswana word onderverdeel in die Orapa, Makoba en Makgadigadisubgroepe, elk met verskillende formasies. Na die intrusie van kimberliete gedurende die Laat Kryt, het 'n lang tydperk van verwering en erosie ingetree, gevolg deur die ontwikkeling van oppervlak-kalkreet. Die nat klimaat is vervang deur semi-ariede toestande, waartydens die onderste Kalaharisedimente afgeset is. Gedurende die Laat Kryt het groot afsettingskomme ontwikkel, wat elkeen deur grabens en horsts opgebreek is. Hierdie grabens is opgevul deur gereelde blitsvloede wat die horsts geërodeer het, gevolg deur lakustriene en uiteindelik soutmeertoestande. Gedurende die Tersiêr het h lang tydperk van nie-afsetting, verwering en erosie die landskap met meer as 25 m in sommige gebiede afgestroop, met die vorming van die Letlhakane Stonelineformasie. Regionale kalkrete wat daarna gevorm het, wissel in ouderdom van Mioseen to Pleistoseen. Gedurende die Vroeë Holoseen het droeë toestande die ontwikkeling van liniêre duinsisteme tot gevolg gehad, wat tydens natter klimaatstoestande in die Holoseen gedegradeer, omgedolwe en met plantegroei bedek is.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/58200
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