A seismic reconnaissance survey of the northern Congo Fan

To study the time-varying influence of the Congo River and the Benguela Current on the deposition at the Angola Continental Margin, a high-resolution reflection seismic survey was carried out on the northern Congo Fan. Four seismostratigraphic units have been defined for the upper 800 m (1000 ms TWT) of the data. The units record different depositional environments, ranging from pre-establishment of the Congo River drainage system to the influence of the Benguela Current. An indication of a general change in the turbidite system is provided by a shift in channel distribution and a relocation of the depocentre of coarse material. The ascent of salt is recorded up to the Pliocene. Gas that has migrated out of Lower Cretaceous shales and that was produced from large quantities of organic matter in the younger sediments can be found on the flanks and on top of the salt domes. In a few places, this gas even ascends to the ocean floor along structural pathways through the topmost unit. (C) 1997 Elsevier Science B.V.