Basement morphology of the middle Benue Trough, Nigeria, revealed from analysis of high-resolution aeromagnetic data using grid-based operator methods

Abstract

The middle Benue Trough is, the central segment of the Benue Trough, an elongate large intracratonic, Cretaceous to Palaeogene rift basin in Nigeria. This study provides new information about the depth to basement (sediment thickness), basement morphology and tectonics of the middle Benue Trough region through detailed analysis and interpretation of preconditioned high-resolution aeromagnetic data using three grid-based semi-automated depth-estimation methods. Integration of results reveals that the middle Benue Trough region is a moderate to deep, fault bounded rift basin with a maximum sediment thickness (basin fill) of about 6300 m. There are seven deep (>~2500 m) sedimentary sub-basins and several elongated shallow (<~1800 m) basement ridges. These sub-basins and basement ridges exhibit dominant NE-SW tectonic trends. Previously mapped magmatic bodies in the axial region of the Trough occur at depths less than about 1000 m. Most of the imaged subsurface features were previously unknown. Subsurface crustal basement structures show trends predominantly NE-SW, ENE-WSW, NNE-SSW and NW-SE and these generally reflect variations in pre-existing crustal basement structural trends in the area, superimposed by the effects of the regional tectonic stress fields responsible for the Trough's tectonic evolution in the Cretaceous – Palaeogene. The implication of the results in regards to hydrocarbon exploration, particularly when combined with published field geological and organic geochemical studies, is that the middle Benue Trough region is more likely to have moderate to low oil prospects and high gas prospects.