Masters Degrees (Earth Sciences)
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Browsing Masters Degrees (Earth Sciences) by Author "Cilliers, Lambertus Marthinius"
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- ItemThe geology of the Graauwduinen heavy mineral sand deposit, west coast of South Africa(Stellenbosch : Stellenbosch University, 1995) Cilliers, Lambertus Marthinius; Rozendaal, Abraham; Stellenbosch University. Faculty of Science. Dept. of Earth Sciences.ENGLISH ABSTRACT: The sedimentology, mineralogy and stratigraphy of the Graauwduinen heavy mineral sand deposit 40km north of the Olifants River mouth on the west coast of South Africa were investigated. Deposition of the heavy mineralĀ enriched sediments is described in terms of marine and aeolian processes active in a north-facing bay bound by a southern headland. The most characteristic feature of the deposit is the presence of two palaeo-strandlines at 20m and 35m a.m.s.l., displaying extremely high concentrations of heavy minerals and situated at the base of two successions. These units formed during relative sea-level stillstands at the respective elevations. The two basal marine units are each overlain by a sequence of aeolian sediments which accreted onto the margin of the regressing sea after the stillstands at 20m and 35m a.m.s.l., respectively. Palaeontological evidence indicates an early Pliocene (1.7-1.8 Ma) age for the 20m strandline. Mineralogically the sequence matures from the basal marine units to the subsurface and surface aeolian units, with a low degree of alteration displayed by the Fe-Ti mineral assemblage. Mineral chemistry provenance studies indicate high grade metamorphic gneisses and phyllites as the probable source of the heavy minerals. Sediment supply to the Graauwduinen heavy mineral concentrating system was by the ephemeral Sout River, 5km north of the deposit, and indirectly by northward-moving longshore drift from the Olifants River, 40km to the south