Geology and Stratigraphy of Middle Cretaceous Sequences Northeast of Afikpo Basin, Lower Benue Trough, Nigeria.

The geology of northeast of Afikpo basin consists of two major lithostratigraphic units of sandstone ridges and low-lying shales, each of which forms significant component of the Middle Albian Asu River Group and Turonian Ezeaku Formation. The major folds in the area have northeast southwest trend, south easterly dip and comprise both anticlines and synclines. The area is also marked by two significant angular unconformities; one interformational between the Asu River Group and Ezeaku Formation, and the other intraformational within the Ezeaku Formation. Mineral assemblages, poor to moderate sorting and angular to subrounded shapes of the minerals suggest a possible model in which sedimentary materials of northeast Afikpo basin were derived from proximal basement granites probably the Oban Massif and deposited in shallow to deep marine environments under fluctuating energy levels, with two major breaks in deposition in the Cenomanian and Turonian times

Structural Evolution, Magmatism, and Effects of Hydrocarbon Maturation in Lower Benue Trough, Nigeria: A Case Study of Lokpaukwu, Uturu, and Ishiagu.

The Benue Trough of Nigeria has been affected by at least two episodes of deformation in the Cenomanian and Santonian times. The deformations generated NE-SW trending structural features, which accommodated massive igneous activities in the Trough. The Lokpaukwu–Uturu–Ishiagu magmatic belt of the Lower Benue Trough is an example of these structurally controlled igneous intrusions. The igneous rocks are predominantly intermediate to basic in character, rich in plagioclase and ferromagnesian minerals and have impacted high maturity on the source sediments due to thermal effect. Total organic carbon contents of the mudrock inclusions in the pyroclastics range from 0.60%wt – 0.86%wt. It is apparent that prior to the eruption, an initial shaly source rock with higher organic carbon content was cooked during the eruption, thereby reducing the source quality of the rocks. Thus, heat from the igneous intrusions raised the temperature of the source rocks above the liquid oil window limit, and thus inhibited the preservation of the essential constituents of petroleum in the shales within the Lower Benue Trough