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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
Cryptic indicators of provenance from the geochemistry of the Okavango Delta sediments, Botswana
Sedimentary Geology, Volume 174, No. 1-2, Year 2005
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Description
The siliciclastic sediments of the Okavango inland Delta of northwest Botswana have a modal composition of quartz arenites and result from a complex history, including transport by river and deposition in a nascent rift basin located in a desert environment with input of aeolian sands. The geochemical composition of sediments from the Okavango Delta was determined in order to constrain the role of weathering at the source and the composition of the source rocks. The chemical analyses and the interelement ratios show a broad compositional range usually encompassing the PAAS composition. The chemical index of alteration (CIA) values and the A-CN-K diagram define an evolution trend which can be interpreted using a mixing model involving a strongly weathered component which corresponds to the sedimentary fraction transported by the Okavango River and a relatively immature component which corresponds to the aeolian sand component of the Okavango sediments. Field geological data supported by geochemical ratios involving elements with affinity for mafic-ultramafic and felsic rocks such as Th/Cr, Th/Sc, La/Sc, La/Co and Eu/Eu* support a source area including mafic-ultramafic and felsic rocks, with or without intermediate rocks. The relationships between certain elements (Cr-Ni, Na2 O-Al2O3, K2O-Al2 O3) refine the interpretation by pointing to the existence of at least three source rock end-members, including a felsic rock source and pyroxene-rich and olivine-rich mafic-ultramafic source rocks. Proterozoic granitoid-gabbro and related volcanic and ortho-metamorphic rock complexes exposed in NW Botswana and adjacent Angola and Namibia are the source rocks of the sediment component which was mixed with aeolian sand and interacted with a variable proportion of diagenetic carbonates to produce the Okavango sediments. © 2004 Elsevier B.V. All rights reserved.
Authors & Co-Authors
Huntsman, Philippa
Botswana, Gaborone
University of Botswana
France, Plouzane
Laboratoire Geo-ocean
Kampunzu, Ali Basira H.
Botswana, Gaborone
University of Botswana
Vink, Bernard W.
Botswana, Gaborone
University of Botswana
Ringrose, Susan M.
Botswana, Gaborone
University of Botswana
Statistics
Citations: 74
Authors: 4
Affiliations: 2
Identifiers
Doi:
10.1016/j.sedgeo.2004.11.001
ISSN:
00370738
Study Locations
Angola
Botswana
Namibia