The role of deformation in controlling depositional patterns in the south-central Niger Delta, West Africa

The Niger Delta has a distinctive structural and stratigraphic zonation. Regional and counter-regional growth faults, developed in an outer-shelf and upper-slope setting, are linked, via a translational zone containing shale diapirs, to a contractional zone defined by a fold-thrust belt that developed in a toe-of-slope setting. Structural and depositional systems have migrated with the progradation of the delta. A paleo fold belt is buried under the modern upper/middle slope. The structural system in this paleo fold belt is complex and comprises a series of en échelon thrust-cored folds and associated ponded slope-basins, shale diapirs, and extensional growth faults. Analysis of the growth sections filling the ponded slope-basins provides a record of how this accommodation was created and subsequently filled and how the individual structural elements interact to create and modify the available space. The depositional systems initially exploit primary accommodation on the slope created by structural movement—the synchronous growth of the fold, the extensional faults and the shale diapir. As the pond is progressively filled, the previously deposited strata modify the accommodation and subsequent depositional systems compensate accordingly.