Multiple detachment levels and their control on fold styles in the compressional domain of the deepwater west Niger Delta

摘要

We interpret recently acquired two-dimensional (2D) and 3D seismic data from the contractional domain of the Tertiary deepwater west Niger Delta, which is an area of current hydrocarbon exploration and development to show that during its gravitational collapse, multiple detachments were active. Detachments are located within (1) what we herein refer to as the 'Dahomey unit', (2) the transition between the Agbada and Akata formations (Top Akata) and (3) the Akata formation. Seismic interpretation and quantitative measurements of fault displacements show that the utilisation of different detachments results in contrasting styles of thrust propagation and fold growth. Two geographical zones are defined. In zone A (NW sector of the study area), the stratigraphically shallowest Dahomey detachment is dominant and is associated with thrust truncated folds. In zone B (SE sector of the study area), a stratigraphically lower detachment approximately at the Agbada-Akata formation boundary is associated with thrust propagation folds. A third detachment, within the Akata formation, is locally developed and is also associated with thrust propagation folds. The different deformational histories are probably related to the mechanical stratigraphy and the pore-pressure characteristics of the succession.