Controls from Depositional Systems and Sequence Stratigraphy of the Pliocene - Pleistocene Strata of Eastern Niger Delta, Nigeria
The Niger Delta is a tectonically active progradational margin where structural collapse under a prograding deltaic wedge complicates depositional patterns and sequence stratigraphic signatures. A Sequence stratigraphic analysis of the Pliocene-Pleistocene strata in the eastern part of Niger Delta based on 2D and 3D seismic data, as well as biostratigraphic and wireline data from 16 wells, documents the depositional patterns within five maximum flooding surface (MFS) bounded genetic sequences. While the Pliocene sequences shows a shelf - to - slope seismic facies association consisting of shallow marine deltaic sediments in proximal areas and hemipelagic shales basinwards, the Pleistocene sequences however, shows a shelf-to-slope seismic facies association consisting of shallow marine deltaic sediments, shelf-margin deltas and deep water sediments. There is an overall basinward shift in axis of deposition from the Pliocene to the Pleistocene.
The main control on sequence development and preserved depositional patterns and facies is the interplay between accommodation and sediment supply. Time structural and isochore mapping suggests that accommodation is primarily controlled by fault-related subsidence. Variation in fault controlled accommodation on the shelf-margins and slope leads to an along strike variation in facies, sequence thickness and stacking patterns. This is especially important in the Pleistocene where there is a marked variation in the developed and preserved facies along strike. Whereas the eastern part of the study area is mainly aggradational and comprises of stacked shelf-margin deltas and an upper slope that is composed primarily of hemipelagic shales, the western and central part of the study area in contrast are mostly progradational and dominated by shelf-margin deltas and multiple submarine channel fills, canyon fill, slope fans, mass transport complex and collapsed slope sediments. Local fault controlled accommodation is a key component in determining whether sediment is sequestered in a shale-cored fault mini-basin, or whether sediments are able to bypass the local fault-basin to deliver sediment to linked deepwater provinces.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009