Sediment Input Points Research Articles

Bathymetry and stratigraphy of the northern Natal Valley (SW Indian Ocean): A preliminary account

Thick sediments (maximum of at least 4900 m) infill the Natal Valley, which lies between the coast of South Africa/Mozambique and the Mozambique Ridge. Eight physiographic provinces are recognised in the valley, and their boundaries can be related to well-defined sediment thickness or facies discontinuities within the basin infill. The acoustic stratigraphy of the area is established by reference to two regionally developed reflecting horizons, which, on the basis of previously published borehole and seismic data, are tentatively identified as mid-Cretaceous (McDuff) and mid-Cainozoic (Angus) hiatuses or important facies boundaries. Sedimentation began in the Natal Valley before mid-Cretaceous times and since then sediment dispersion has been strongly influenced by the disposition of large basement (? volcanic) highs: the approximately NE—SW Almirante Leite and Naudé ridges, and the larger N—S Mozambique Ridge. There is abundant evidence that sedimentation in the vicinity of these ridges has been current-controlled since at least mid-Cainozoic (Angus) times. The two main terrigenous sediment input points have been the Tugela and Limpopo rivers, which have large sediment cones adjacent to their mouths.