Late Proterozoic bedrock geology and its influence on neogene littoral marine diamondiferous trapsites, MA1-Sperrgebiet, Namibia
Master Thesis
2001
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University of Cape Town
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Abstract
Namibia's south western coast, the Sperrgebiet, hosts one of the world's largest diamond placer deposits. Diamond distribution in this placer deposit is directly related to the presence of a diamond-carrying gravel, the degree of reworking of the gravel and the quantity and quality of the diamond trapsites. The diamond-carrying gravel is present in the form of palaeo-beaches. Six Plio-Pleistocene beaches have been identified lying onshore between the Orange River mouth and Chameis Bay. The Plio-Pleistocene beaches are underlain by Late Proterozoic footwall. The Late-Proterozoic footwall has undergone extensive marine erosion and development of marine platforms during different sea-level stillstands. Diamond trapsites in the form of potholes and gullies are incised into palaeo platforms formed during the sea-level stillstands. The marine erosion palaeo-platforms have been cut into the predominantly siliciclastic rocks of the Gariep Belt. The Late Proterozoic Gariep Belt is divided into an eastern para- aulochthonous passive continental margin zone, the Port Nolloth Zone, and a western allochthonous Marmora Terrane. Previous work suggested that the Marmora Terrane had been thrust on top of the Port Nolloth Zone in a south-easterly direction and that the Marmora Terrane could be subdivided into three tectonostratigraphic units: the Schakalsberge Complex, the Oranjemund Complex and the Chameis Complex. In addition, previous work indicated that the Oranjemund Complex had been stacked tectonically between the Chameis Complex in the northwest and the Schakalsberge Complex in the southeast. However, this study questions the subdivision of the Marmora Terrane into three separate tectonic complexes. The rocks in the study area forms part of the newly deļ¬ned Oranjemund Group, Oranjemund Sub-terrane.
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Bibliography: leaves 117-128.
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Reference:
Jacob, J. 2001. Late Proterozoic bedrock geology and its influence on neogene littoral marine diamondiferous trapsites, MA1-Sperrgebiet, Namibia. University of Cape Town.