Diapirs of the Continental Margin of Angola, Africa

Abstract

A geophysical study of the continental slope and rise off Angola shows the presence of two basement ridges under the sedimentary prism. These ridges are the continuation of onshore basement highs, or parallel to them. The continental rise deposits are built up behind the outermost of these ridges; the deposits of the onshore Cuanza basin and its northward offshore equivalent behind the innermost one. The sedimentary sequences in both zones have a parallel history of evaporite deposition followed by diapirism. Two separate phases of salt tectonics can be distinguished which propagated eastward with time from their western terminal basement ridges. The relative ages of the onshore and offshore sequences cannot be established at this time. The offshore diapir province has a width of more than 300 km and extends possibly from the Congo Canyon in the north to near the Walvis Ridge in the south.