Relationship between Miocene to Present Sediment Dispersal and Structural Deformation in the NW Niger Delta

Leduc, Amelie M.¹; Davies, Richard J.¹; Densmore, Alexander L.^2
1 Department of Earth Sciences, CeREES (Centre for Research into Earth Energy Systems), Durham University, Durham, United Kingdom.
² Institute of Hazard & Risk Research, Department of Geography, Durham University, Durham, United Kingdom.

Understanding deep-water sedimentary and structural systems is a key challenge for the prediction of reservoirs in settings where sedimentation is contemporaneous with deformation. We still know little about how the sediment fairway responds to tectonic deformation at a variety of spatial scales, and over the life span of a sediment routing system.

This project focuses upon the northwest Niger Delta, which is comprised of a slope extensional, translational and compression structural settings. In the deep-water region, the overpressured upper unit of the mudstone-dominated Akata formation hosts a regional-scale detachment, above which a fold and thrust belt has developed within the Agbada formation. This formation contains a succession of mass-transport deposits, turbidites and channel-levee deposits. Sedimentation could be related to a number of factors including relative sea-level changes at different scales, due to contemporaneous deformation.

Prior work on the western Niger Delta using essentially 2D data has established the relationship between structure and channel development, in recent deposits and in distal areas. The uplift of the fold-and-thrust belt seems responsible for channels cutting through the relief and large channel systems localized above active transfer faults for long periods of time. Previous studies have shown that sedimentary processes such as knickpoints migration in the most distal areas can also help us in indicating the evolution of the deformation in the westernmost Delta. However no systematic study of the change in channel location and pattern during fault growth has yet been made in older strata and in closer areas from the shelf.

Here we exploit the marked structural heterogeneity and well-imaged sedimentary systems in the northwest Niger Delta. A large 2D and 3D seismic data set from is being used to relate the growth of individual fault arrays to spatial patterns of erosion and sedimentation and channel development. We focus in particular on the temporal persistence of sediment pathways across the delta, and on identifying long-term changes in channel geometry and process that may be driven by the time-varying distribution of surface deformation. We expect to identify the main areas of local sediment source and deposit, and to map these results. Our investigations may be extended to more distal areas (diapir belt and toe thrust belt) as appropriate. Models production could then be considered to test our hypothesis.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009