The Quaternary Seismic Architecture of the Eastern Part of the Submarine Niger Delta: A Very Detailed Record of the Eustatic and Tectonic Interplay

G. Badalini, B. Savoye, M. Dall'asta, and A.-M. Schwab

In 1992 and 1993, IFREMER and ELF Aquitaine Production conducted two high resolution seismic surveys in the Eastern Niger Delta (GUINES project). An integrated study of multichannel seismic, high resolution seismic and side-scan sonar data, allowed the definition of a structural style and main sedimentary units, which led to an understanding of the relationships between sedimentation, eustacy and tectonics.

The continental margin of the Niger Delta is affected by major gravity-tectonic deformation. Active growth-faults usually occur near the present shelf break, dip seaward and often are associated with landward dipping antithetic faults. Shale diapirs show variable size, shape, distribution, depth of burial and orientation. They strictly control the actual morphology of the delta and delineate different intraslope basins. Two main structural trends (NS and NE-SW) are identified. Different phases of diapiric deformation are recorded by the infill of the sediment basins. Phases of deformation are frequently associated with sedimentary instability and shifting of basins depocenters.

The shelf-edge shows a complex of prograding wedges, permitting the identification of different phases of relative sea-level fluctuation. This geometry is clearly the result of the complex interplay between vertical tectonic motion and eustatic cycles. The early Pleistocene units record a progressive landward migration of the depositional systems, while the most recent units show a seaward migration. Tectonics strongly influence the size, shape and internal geometry of the sedimentary bodies in these depositional systems.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California