(1) Consultant, Houston, TX
(2) Texaco, Lagos, Nigeria
(3) Texaco, Houston, TX
Abstract: Tectonic controls on regional sequence stratigraphy in the Niger Delta, offshore Nigeria
Regional distribution of stratigraphic ages and systems tracts in the offshore Niger delta are closely tied to the depositional and tectonic development of the delta depocenter. Gravitational loading and down-dip tectonic styles, including counter-regional and down-to-basin normal growth faults in shelf areas, diapirism in slope areas, and compressive toe thrusting in near-distal and far-distal basin regions. Differences in the amount of gravitational displacement and structural intensity between depocenter and flanks result in lateral strike-slip displacement along depocenter flanks.
Toe thrusts form an inner zone along the outer fringe of the diapir zone, and an outer zone which has two large lobes controlled by an oceanic crustal high in the central delta area. A “quiet” area of minor thrusting and detachment folding separates inner and outer thrust zones on either flank of the depocenter.
Counter-regional normal fault systems consist of Upper Miocene to Lower Pliocene prograding reservoirs. Down-to-basin growth fault systems contain Upper Pliocene and Pleistocene distal prograding units with shingled toe turbidities. Depocenters of these young sediments are restricted to withdrawal areas of shales now forming the diapiric zone. Miocene or older deepwater sands occur in outer diapiric slope areas and in compressive folds and thrusts farther seaward. They consist of deepwater sheet sands and leveed channels. Seismic and well-log signatures of sand types and regional maps of systems tracts are illustrated.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana