HOPKINS, ANDREW E., Cardiff University, Department of Earth Sciences, Wales

ABSTRACT: The Influence of a Prominent Paleobathymetric Feature on a Continental Margin Depositional System: The Phoenix High, Walvis Basin, Offshore Namibia

The Phoenix High, located towards the northern margin of the Walvis Basin, offshore Namibia, is one of several Late Cretaceous volcanic centres related to the nearby Walvis, Ridge and to the opening of the South Atlantic. As a prominent bathymetric feature, with an area of about 1,000 square kilometres, and a maximum relief in excess of 2,000 metres, it exerted a significant influence on post-rift sedimentary processes in the basin.

The mainly clastic post-rift deposits of the Walvis Basin include prograding deltaics, turbidites, sediment drifts and channel fill. Many of these show evidence on seismic data and on maps of non-uniform depositional patterns, indicating the operation of processes additional to down-slope action. These are believed likely to include erosion and redeposition by the northward-flowing Benguela bottom current and possibly by landward-directed upwelling currents.

This project is designed to investigate the role played by the Phoenix High in influencing depositional patterns produced by the various current directions. Additionally, other impacts such as the extent to which subsidence around the cooling volcano affected accommodation, and the ways in which successive episodes of erosion and collapse of the volcano contributed to local sediment supply will be studied.

The main tools of the study are 2-D seismic and well data. A key aim will be to predict the distribution and heterogeneity of potential reservoir sands. Comparison will also be made with other, similar settings on the West African margin. It is hoped that this study will have a bearing on the general understanding of how paleobathymetric features have influenced depositional systems.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid