Abstract

Sedimentation over large areas of a marginal plateau, the northernmost Natal Valley (NNV), is influenced by the tropical/sub-tropical Agulhas Current. Through mobilization of detritus and concentration of sedimentation into localized depo-centres, current action provides a mechanism for hiatus development both in on-shelf and off-shelf areas. Post-Gondwana break-up sedimentary basin in-fill is interrupted by several regional hiatuses. These correlate with coastal regressions, global sea-level low-stands, proposed phases of invigorated oceanic circulation and with global phases of slow deep-sea sedimentation. An assessment of these mechanisms indicates detritus supply related to sea-level changes cannot explain correlation of on-shelf and off-shelf hiatuses. Current action may have been a contributory factor in development of a Cenomanian/Turonian hiatus and facies change and a Cretaceous/Tertiary boundary hiatus.

An Early Oligocene hiatus clearly marks a change in the Agulhas Current regime. Current-moulded features, asymmetric sediment distributions and re-working attest to enhanced current action. Establishment of a cold bottom layer in the ocean at this time stimulated Indian Ocean surface/near-surface circulation. New circulation patterns were established after a Miocene/Pliocene boundary hiatus. Since then the main flow-paths have been fairly stable, although local depo-centre shifts late in the Pliocene–Recent sequence suggest eastward movement of a counter-current and cyclonic eddy off Maputo.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.