In this First Break article, published July 2024, TGS discusses how 2D and 3D mapping combined helps us to understand the differences in sediment input directions and faulting impact on the fairways of the Cretaceous, Paleogene and Miocene.
Abstract
Offshore Benin, and the wider Keta Basin, remains an underexplored area of the West Africa Transform Margin. The evolution of the different sediment fairways and their depocentres can be identified on structure maps from the mapping of a regional 2D seismic dataset. The 3D seismic offshore Benin supports the 2D interpretation but in addition, allows for a more complete evaluation through detailed seismic attribute analysis. The use of 3D spectral decomposition highlights the changes in fairway directions with clear imaging of the channel systems and their orientations, correlating with the thicknesses observed from regional 2D seismic mapping.
The transform faults strongly control the overall structuration of offshore Benin and the depositional style during the Cretaceous period. The onshore Togo and Benin river systems
supply sediment directly to the basin in a north to south direction which is limited and directed by the transform movement and ridges outboard. Towards the end of the syn-transform deposition, the main fairway input changes from a directly northern source to a north eastern source in the Dahomey Embayment. Finally, in the Cenozoic, the Niger River system drainage increased leading to the Benin Ultra Deep area to form part of the Niger prodelta, with a redominant easterly sourced sediment input. The transform faults are no longer active and no longer control sediment distribution, leading to an unconfined channelised system.
Download the full article HERE.