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4 - Megafans of the Northern Kalahari Basin (Angola, Botswana, Namibia, Zambia)

from Part II - Regional Studies

Published online by Cambridge University Press:  30 April 2023

Justin Wilkinson
Affiliation:
Texas State University, Jacobs JETS Contract, NASA Johnson Space Center
Yanni Gunnell
Affiliation:
Université Lumière Lyon 2
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Summary

Maps generated from various data sources reveal ten new megafans in the northern Kalahari region where, until now, the Okavango had been the only one recognised. Seven megafans were generated by rivers flowing off the Bié Swell of southern Angola, east to the Zambezi basin and south to the Owambo basin. Only three (Okavango, Cuando, Zambezi) are apexed at shoulders of the Okavango Rift (northern Botswana). Unusually, the Cubango/Okavango River has given rise to two megafans: the upstream Cubango megafan, and the well-known Okavango megafan downstream. Avulsion behaviour of three rivers has also demonstrably shifted discharge between major basins over time: the Cassai has, at times, flowed north into the Congo basin; the Cubango flowed into the Owambo basin (Etosha dry lake), but now discharges into the Makgadikgadi basin (via the Okavango megafan); and the Kunene, which now flows to the Atlantic Ocean, at one time discharged into the Etosha pan. Recognising the existence of so many more megafans than previously appreciated, as well as their autogenic, avulsive dynamics, is an invitation to reconsider the regime of sedimentary sequence deposition in these basins, which may have erroneously been interpreted as resulting from climatic or other external forcing factors.

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Publisher: Cambridge University Press
Print publication year: 2023

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