地球科学と気候変動ジャーナル

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Role of Equatorial Fracture Zones on Fluid Migration across the South Atlantic Margins

N.K. Samaila* and O.K. Likkason

The continental margin basins of Brazil and West Africa share very similar tectono-stratigraphic megasequences that are recognizable in petroliferous basins, as a result of the Late Jurassic-Early Cretaceous rifting of the South Atlantic basins. A number of oil families present along the South Atlantic conjugated margins are composed of genetically related oils of mixed provenance. Motion of tectonic plates and their configurations which depend so much on the nature of the boundaries and their orientations strongly influence fault tectonics within both continents The tectonic evolution of the plates leads to the formation of fracture zones parallel to the direction of plate motion. The Middle Benue Trough of Nigeria and by extension, the whole Benue Trough, is bound by two offshore transform faults (the Chain and the Charcot Fracture Zones). These faults are asymmetric longitudinally with an oblique transverse fault bounding the basin, and have been outlined by the presence of magnetic lineation. Five E-W profiles across the Middle Benue Trough were selected for the application of Werner deconvolution and subjected to harmonic analysis. The magnetic dataset was used in concluding that the Equatorial Fracture Zones (EFZ) in the South Atlantic Ocean extending from South America into the Gulf of Guinea are mainly responsible for long distance migration of marine hydrocarbons from the West Africa margin to the offshore of Brazil.