Field evidences demonstrates that the Precambrian rocks are fed from sedimentary petroleum source rocks overlying it. The oil residue observed within the fractures of the basement rocks occur as brittle solids which are believed to have emplaced as conventional light oils, but are now degraded to bitumen. Precambrian basement rocks of both the Gongola and Yola sub-basins of the Northern Benue Trough have oil residue, this implies that the occurrence is widespread (about 70 km apart for the localities considered in this study). They occur mostly where the Cretaceous Bima Formation are in contact with the Precambrian basement. The plain of unconformity separating the Cretaceous Bima Formation and the Precambrian basement rock is the route through which the oil migrated.
Key words: Precambrian Basement, Total Organic Carbon.
|
