The western portion of the Nigerian continental margin is underlain by continental and transitional crust. It exhibits stable to moderately unstable progradation and is characterized by a well-developed shelf-slope break. Systems tracts are similar to those described by Vail for stable progradational margins.

In contrast, strata off the central portion of the Nigerian coast, in the vicinity of the Niger Delta, are underlain by oceanic crust. Systems tracts are similar to those in Neogene strata of the offshore Gulf of Mexico. The continental margin exhibits highly unstable progradation. Large growth faults, toe-thrusts and well-developed shale diapirs are present. The shelf/slope break is commonly not well-developed. Instead, a ramp is usually observed. In some places, this ramp is cut by large growth faults that define the shelf margin.

Lowstand basin floor fans in both areas are defined by a well-developed upper reflection. This reflection downlaps along the sequence boundary or abuts against the downthrown side of a growth fault surface. The lowstand slope fan contains channel complexes characterized by chaotic bedding with small bright spots and less common large channels, which exhibit concave-upward reflections. Most of the slope fan systems tract is comprised of discontinuous to semi-continuous subparallel reflections. In the western portion of the study area, slope fan deposits commonly pinch out at or near the shelf margin. Sand-rich facies (suggested by amplitude anomalies) are developed immediately downdip of major canyon cuts and deposition occurred largely from point sources. In contrast, contemporaneous shallow-water facies are developed in slope fan systems tracts off the central portion of the Nigerian coast. Deposition occurred along a line source.

Large amplitude anomalies in the lowstand prograding wedge suggest well-developed sheet sands are present off both western and central portions of the coast. These sands are present in both shallow-water (interpreted as delta front facies) and deepwater deposits (interpreted as shingled turbidites). The transgressive and highstand systems tracts are usually very thin.

Different exploration strategies are appropriate for each systems tract off both the western and central portions of the Nigerian coast. The best plays off the central portion of the Nigerian coast are probably structural traps (this includes updip pinchouts) whereas hydrocarbons may occur in both structural and stratigraphic traps along the west coast of Nigeria.

End_of_Record - Last_Page 11---------------