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Source of the suspended load of the upper Orange River, South Africa

John S. Compton and Livhuwani Maake
Source of the suspended load of the upper Orange River, South Africa
South African Journal of Geology (September 2007) 110 (2-3): 339-348

Abstract

The Orange River is one of the World's most turbid; delivering 60 million tons of sediment each year to the western margin of South Africa. Much of this sediment is believed to be from soil erosion, an increasing environmental threat to sustainability in southern Africa. This study focuses on the upper reaches of the Orange River above the Caledon River confluence, because it is here that high rainfall and topographic relief of the Drakensberg Mountains produce most of the Orange River's suspended load. Comparison of grain size, mineralogy and geochemistry of the suspended sediment load with catchment bedrock soils provides an estimate of the source of the suspended sediment. Major and trace element ratios indicate that the suspended sediment load is primarily derived from Karoo (upper Beaufort and Stormberg groups) sedimentary rocks rather than Drakensberg basalt. The Caledon River carries the largest fine-mud suspended load primarily from the erosion of Karoo sedimentary rock soils. The organic carbon content of the suspended load ranges from 1.0 to 1.3 weight % with delta (super 13) C values that range from -19.7 to -16.9 per mil PDB. The delta (super 13) C values of the organic fraction of soils is highly variable (-21.5 to -12.7 per mil PDB) and reflect the mix of C3 and C4 vegetation in the catchment area.


ISSN: 1012-0750
EISSN: 1996-8590
Serial Title: South African Journal of Geology
Serial Volume: 110
Serial Issue: 2-3
Title: Source of the suspended load of the upper Orange River, South Africa
Affiliation: University of Cape Town, Department of Geological Sciences, Rondebosch, South Africa
Pages: 339-348
Published: 200709
Text Language: English
Publisher: Bureau for Scientific Publications, Pretoria, South Africa
References: 69
Accession Number: 2008-024186
Categories: HydrogeologySedimentary petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
S31°00'00" - S30°00'00", E26°00'00" - E27°00'00"
Country of Publication: South Africa
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Geological Society of South Africa. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200808
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