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South African Journal of Science

Print version ISSN 0038-2353

Abstract

BOSMAN, C. et al. Shelf sediments off the Thukela River mouth: complex interaction between fluvial and oceanographic processes. S. Afr. j. sci. [online]. 2007, vol.103, n.11-12, pp. 490-492. ISSN 0038-2353.

The shelf off the Thukela River has a unique geological and oceanographic setting within the KwaZulu-Natal continental margin. High terrestrial sediment input from the Thukela is delivered to this unusually wide shelf, resulting in deposits that exhibit both deltaic and submarine fan characteristics, the latter initiated during flood events. The Inner shelf (0 to -30 m) is dominated by well-sorted sands reworked by fair-weather processes. The Mid-shelf (-30 to -60 m) comprises poorly sorted sands subjected to ocean storm processes and redistribution by the semi-permanent KwaZulu-Natal Gyre. The Outer shelf (-60 to -100 m) is characterized by gravels and large bedforms produced by the southerly-flowing Agulhas Current. During fair-weather conditions, the Mid-shelf is dominated by the KwaZulu-Natal Gyre and the Outer shelf by the Agulhas Current. During extreme flood events, sedimentation extends further offshore, building the submarine fan, overprinting the typical outer-shelf sediment distribution. This model provides a basis for the effective assessment and management of the biological communities and commercial prawn industry in the area.

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