Sediment dynamics on the narrow, canyon-incised and current-swept shelf of the northern KwaZulu-Natal continental shelf, South Africa

Side-scan sonar, multibeam bathymetry, Shipek(TM) grab, and high- to moderate-resolution sub-bottom data for the northern KwaZulu-Natal continental shelf reveal further insights into the interactions between sediment dynamics, strong western boundary currents and submarine canyon topography. Unlike previously recognised mechanisms for bedload parting on current-swept shelves, bedload partings here are the result of complex interactions between the western boundary poleward-flowing Agulhas Current and submarine canyon topography. This has resulted in bedforms orientated orthogonally to the canyon axis, with sediments entrained equator-wards into the canyon heads before resuming their dominant southerly migration. It is in these zones of parting where the most prominent bedforms occur; these bedform fields are formed by positive feedback in the boundary layer between an increasingly undulatory Agulhas Current and a seafloor incised by regularly spaced submarine canyons. Bedform morphometrics such as wavelength-height, depth-height and distance from thalweg-height relationships show no distinct patterns, indicating that the bedforms are heavily reworked and appear to be out of equilibrium with the inherent oceanographic conditions.