Oligocene to Holocene sediment drifts and bottom currents on the slope of Gabon continental margin (west Africa): Consequences for sedimentation and southeast Atlantic upwelling

摘要: Seismic reflection profiles on the slope of south Gabon continental margin display furrows 2 km wide and some 200 m deep, that develop normal to in 500‐1500 water depth. Furrows are characterised by an aggradation=progradation pattern which leads margin-parallel, northwestward migration their axes through time. These structures, previously interpreted as turbidity current channels, distinctive seismic image internal organisation sediment drifts, constructed activity bottom currents. Sediment drifts were initiated above a major Oligocene unconformity, they developed within Present megasequence general progradation margin, whilst markedly absent from underlying Late Cretaceous‐Eocene aggradation megasequence. The presence upslope migrating waves, northwest indicate deposition flowing upslope, under influence Coriolis force. Such landwards-directed currents probably represent coastal upwelling, has been active along west Africa throughout Neogene. © 1999 Elsevier Science B.V. All rights reserved.