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The marine geology of the Northern KwaZulu-Natal continental shelf, South Africa.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Green, Andrew |
| Copyright Year | 2009 |
| Abstract | This study proposes that the submarine canyons of the northern Kwazulu-Natal continental margin formed contemporaneously with hinterland uplift, rapid sediment supply and shelf margin progradation during the forced regression of upper Miocene times. These forced regressive systems tract deposits volumetrically dominate the shelf sediments, and comprise part of an incompletely preserved sequence, amongst which six other partially preserved sequences occur. The oldest unit of the shelf corresponds to forced regression systems tract deposits of Late Cretaceous age (seismic unit A), into which a prominent erosive surface, recognized as a sequence boundary, has incised. Fossil submarine canyons are formed within this surface, and underlie at least one large shelfindenting canyon in the upper continental slope. Smaller shelf indenting canyons exhibit similar morphological arrangements. Late Pliocene deposits are separated from Late Cretaceous lowstand deposits (seismic unit B) by thin veneers of Late Palaeocene (seismic unit C) and mid to early Miocene (seismic unit D) transgressive systems tract deposits. These are often removed by erosive hiatuses of early Oligocene and early to mid Pliocene age. These typically form a combined hiatus surface, except in isolated pockets of the upper slope where late Miocene forced regressive systems tract units are preserved (anomalous progradational seismic unit). These sediments correspond to the regional outbuilding of the bordering Tukhela and Limpopo cones during relative sea level fall. Either dominant late Pliocene sediments (seismic unit E), or transgressive systems tract sediments which formed prior to the mid Pliocene hiatus, overlie these sediments. Widespread growth faulting, slump structures and prograding clinoforms towards canyon axes . indicate that these sediments initiated upper slope failure which served to create proto-canyon rills from which these canyons could evolve. The association of buried fossil canyons with modern day canyons suggests that the rilling and canyon inception process were influenced by palaeotopographic inheritance, where partially infilled fossil canyons captured downslope eroding flow from an unstable upper slope. Where no underlying canyons occur, modern canyons evolved from a downslope to upslope eroding system as they widened and steepened relative to the surrounding slope. Statistical quantification of canyon forms shows a dominance of upslope erosion. Landslide geomorphology and morphometric analysis indicate that this occurred after downslope erosion, where the canyon axis was catastrophically cleared and incised, leading to headward retreat and lateral excavation of the canyon form. Trigger mechanisms for canyon growth and inception point to an overburdening of the upper slope causing failure, though processes such as freshwater sapping |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://researchspace.ukzn.ac.za/xmlui/bitstream/handle/10413/5648/Green_Andrew_Noel_2009.pdf?isAllowed=y&sequence=1 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
