Publication Date:
2019-07-16
Description:
The transfer of sediment from the upper continental slope to rise is poorly documented along the
southeast African passive margin. New swath bathymetric and sub-bottom data collected in the Natal
Valley, southwest Indian Ocean, provide insight into the evolution of the Tugela canyon and fan system.
Several distinct downslope changes in canyon morphology are noted. The canyon increases in relief and
widens with depth. Basement outcrop is restricted to the head of the canyon becoming less prominent
with depth. Step-like terracing of the canyon walls and floor becomes prominent in the mid-slope
portions of the canyon and is related to a marked increase in the cross sectional asymmetry of the
canyon profile. The contemporary Tugela canyon rests within a depression of the last phase of infilling.
The canyon is the product of downslope erosion, and incision, caused by several phases of hinterland
uplift in the mid Oligocene, mid Miocene and late Pliocene. Each phase was followed by pelagic infilling
of the palaeo-canyon form. Downslope, the uplift phases are preserved in the cut-terraces and axial
incisions within the main canyon thalweg. The contemporary canyon is a moribund feature, sediment
starvation of the shelf area by current sweeping of the Agulhas current has decreased the material
available for canyon incision and fan development. Additional current sweeping by the North Atlantic
Deep Water current has stunted the development of the associated fan complex.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
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