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The topography of the Okavango Delta, Botswana, and its tectonic and sedimentological implications

T. Gumbricht, T. S. McCarthy and C. L. Merry
The topography of the Okavango Delta, Botswana, and its tectonic and sedimentological implications
South African Journal of Geology (September 2001) 104 (3): 243-264

Abstract

A topographic map of the Okavango Delta and environs has been constructed using a combination of elevation data including trigonometric beacons and spot heights from the government of Botswana, surveys of the navigable channels, U.S. Department of Defense data and measurements made during a geophysical survey of the region. The topography provides insight into the local tectonic and sedimentary history. Local tectonics are dominated by uplift and horst formation associated with the Ghanzi Ridge, and an arch to the north of the Panhandle, which appear to represent the tips of incipient rifts which are propagating from the northeast. The Delta has formed in the resulting depression between these arches. The Panhandle has developed along a fault, and may be largely an erosional feature incised into the northern uplift zone. The Delta itself is an alluvial fan of remarkably uniform gradient. There is no evidence of regional tilting of the fan surface. Local highs and lows are developed on the fan, but channel location is relatively insensitive to this local topography. Moreover, marked elevation differences exit between adjacent channels, creating hydrologically unstable conditions. These unusual features of the local hydrology arise because of the confining effect of channel-flanking vegetation. Sedimentation in the Delta appears to be causing crustal sagging of the central Delta, which has: tilted the major palaeo-shoreline of the Mababe Depression to the west; formed a local depression within the Ghanzi Ridge facing the Delta; and detached a sliver of the ridge along the Thamalakane fault. It is suggested that local seismicity also results mainly from sediment loading. The Selinda spillway occupies a marked local depression, which is a graben between the Gumare fault and an extension of the Linyanti fault. It is Probable that southwesterly propagation of the uplift zone associated with the incipient rift will ultimately deflect the Okavango River into the Chobe-Zambezi river system via this graben.


ISSN: 1012-0750
EISSN: 1996-8590
Coden: TGSAA3
Serial Title: South African Journal of Geology
Serial Volume: 104
Serial Issue: 3
Title: The topography of the Okavango Delta, Botswana, and its tectonic and sedimentological implications
Affiliation: University of the Witswaterand, Department of Geology, Wits, South Africa
Pages: 243-264
Published: 200109
Text Language: English
Publisher: Bureau for Scientific Publications, Pretoria, South Africa
References: 59
Accession Number: 2002-064797
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., geol. sketch maps
S20°40'00" - S18°00'00", E21°45'00" - E24°30'00"
Secondary Affiliation: University of Cape Town, ZAF, South Africa
Country of Publication: South Africa
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200220
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