Modelling geologic features and structures in the Middle and Lower Benue Trough of Nigeria from gravity and aeromagnetic data sets

Understanding subsurface structures is key to predicting the evolution of a basin and its resources. The Benue Trough is a mega-structure that has been moderately well studied, although a detailed regional subsurface study of the basin is lacking. Our aim in this study is to highlight and show clearly the subsurface geologic structures/features through 2D and 3D models. We used high-resolution aeromagnetic and gravity datasets to map and investigate geologic features and subsurface structural texture of the trough in 2 and 3 dimensions. We constructed geologic models in 2D from gravity and magnetic datasets and mapped basement faults, depth to basement, Curie, and Moho depths, and interpreted the crustal structure of the basin. Three well-defined basement fault systems were identified: NE-SW, NW-SE, and ENE-WSW. Based on basement fault kinematics through paleo-stress field interpretation, we showed that the basement faults evolved through plate tectonic activities at the earlier stage of the evolution of the trough. We then carefully modelled in 3D critical interfaces (basement surface, Curie isotherm, and Moho), where we estimated their depths and interpreted their morphologies. The average basement depth is 4.3 km and areas of basement lows are interpreted as sub-basins; these are suitable sites for the accumulation of sediments (depocentres) while the basement highs are considered basement uplifts and blocks. The Curie depth (the depth to the bottom of the magnetic layer) is relatively flat across the area while the Moho is uplifted directly under the basin. We observed the crust to be thinned directly under the basin which we attributed to extensional rifting processes. This study exposed the subsurface tectonic architecture of the trough and demonstrated its continental origin due to crustal rifting and extension, accompanied by faulting, Moho shallowing, magma emplacement, and crustal thinning and stretching.