A sequence stratigraphic framework for a narrow,current-swept continental shelf: The Durban Bight,central KwaZulu-Natal,South Africa |
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| Institution: | 1. Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic;2. Centre for Polar Ecology, Faculty of Science, University of South Bohemia in České Budějovice, Na Zlaté stoce 3, 370 05 České Budějovice, Czech Republic;3. Department of Physical Geography and Geoecology, Faculty of Science, Charles University in Prague, 128 43 Praha, Czech Republic;4. Department of Geography, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic |
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| Abstract: | High resolution seismic lines from the inner and mid-shelf of the Durban Bight reveal an unprecedented view of the seismic stratigraphy of the central KwaZulu-Natal uppermost continental margin. Seven units are recognised from the shelf on the basis of their stratal architecture and bounding unconformities. These comprise four incompletely preserved sequences consisting of deposits of the highstand systems tract (Unit B), falling stage systems tracts (Unit C), the transgressive systems tract (Units A, D and G) and lowstand systems tracts (early fill of the incised valleys and strike diachronous prograding reflectors of Unit A). Seismic facies recognised as incised valley fills correspond to the lowstand and transgressive systems tracts. When integrated with published accounts of onshore and offshore lithostratigraphy and local sea level curves, we recognise an Early Santonian transgression (Unit A to Unit B), superimposed by uplift-induced pulses of forced regression. A Late Campanian relative sea level fall (Unit C) followed. Sediments of the Tertiary period are not evident on the Durban Bight shelf except for isolated incised valley fills of Unit D lying within incised valleys of Late Pliocene age. Overlying these are two stages of Pleistocene shoreline deposits of indeterminate age. Erosion concurrent with relative sea level fall towards the last glacial maximum shoreline carved a third set of incised valleys within which sediments of the Late Pleistocene/Holocene have infilled. |
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