Seismic stratigraphic record of transpression and uplift on the Romanche transform margin, offshore Ghana

Recently, available multi-channel seismic reflection data from offshore Ghana have been reprocessed to probe the eastern Romanche Fracture Zone (RFZ) of the Equatorial Atlantic and the sedimentary basins of the paleotransform margin. The RFZ terminates landward in a submarine canyon, up to 2 km deep and >50 km wide, variably filled with submarine fans and projects landward into a Neoproterozoic dextral shear zone. By contrast, the RFZ to the southwest is represented by an ENE submarine escarpment juxtaposing continental and oceanic crusts. Three major sedimentary sequences representing pre-, syn- and post-rift strata have been identified from the seismic profiles and calibrated with chronostratigraphic data from oil exploration wells. The pre-rift sequence consists largely of Paleozoic strata ranging in age from Devonian to Carboniferous. The overlying syn-rift sequence, which was deposited during the intracontinental shearing stage, consists of Aptian to Albian silicilastic strata with distinct continental facies. The seismic sections provide some of the clearest images yet of: (i) folding associated with transform displacement, and (ii) southwest increasing subaerial erosion and stratal discordance. We attribute lateral variation in erosion to crustal thickening associated with folding and to transient thermal effect of ridge-transform interaction which is predicted to produce westward increasing uplift on this margin.