Defomartional Styls Of The West African Margin

Reprocessing of the PROBE Study seismic data set indicates that the continental margin between Cameroon<br>and Southern Gabon is separated into the North Douala and Gabon Basins by the Kribi Fracture Zone. This is<br>a 75 km-wide transform fault that trends NE-SW and intersects the coastline between 2-3’ N. Much of the<br>margin off Equatorial Guinea is influenced or controlled by fracture zone tectonics. North of the Kribi<br>Fracture Zone, oceanic crust extends to the coastline and floors a narrow shelf off Cameroon. Little rift<br>margin exists in the North Douala Basin. Reflection Moho beneath oceanic crust is relatively weak but<br>continuous throughout the North Douala Basin and oceanic crustal thickness is extremely uniform,<br>averaging about 1.75 s in two-way travel time. South of the Kribi Fracture Zone, oceanic crust is offset about<br>350 km to the southwest, creating a broad rift margin off Gabon. Rifting of the margin here seems to involve<br>brittle, upper continental crustal sheets overlying a series of ductile lenses that generally dip southeasterly.<br>The ductile lenses may unroof toward outer highs, which mark the boundary between oceanic and<br>continental lithosphere. Strong reflection events are often associated with the ductile shear zones that define<br>the lenses, but a single, continuous event representing reflection Moho cannot be mapped. The concept of a<br>regional reflection Moho beneath rifted continental crust may be flawed in this area. The tectonic and<br>rheological models presented here may be useful in framing hydrocarbon exploration tactics and strategies<br>along this passive margin.