Morphology, Limits, Origin, and Age of Salt Layer along South Atlantic African Margin

Abstract

Abstract The west African continental margin between Abidjan (Ivory Coast) and Walvis Bay (Southwest Africa) was surveyed in 1971 by the R/V Jean Charcot. Fifty-eight seismic-reflection (flexotir source), bathymetric (3.5 and 12 kc), gravimetric, and magnetic profiles were obtained. The seaward limit of an evaporitic zone outlined during the survey is at the boundary between continental slope and continental rise. Variation of depth of this limit as a function of latitude shows the presence of a large offset at 11°S which seems to be related to an east-east-southeast line of magnetic seamounts cutting into the continental slope. The Annobon-Cameroun volcanic axis separates the salt zones of the Nigerian basin and Congo-Angola basin. The northern limit of salt deposition in the Congo-Angola basin is marked near 1°N by a strong southwest-northeast magnetic trend. On the south it extends to near 14°S. The Walvis Ridge, located farther south, does not seem to have an effect on evaporite deposition.