The structure of the Goulfey-Tourba sedimentary basin (Chad-Cameroon): a gravity study

A gravity study of the Goulfey-Tourba basin, southeastern Chad Lake, northern Cameroon, is presented to establish its main shallow crustal structural features. Regional and residual anomalies are interpreted in terms of the available geological information. Spectral analysis and 2.5D modelling of three profiles selected from the residual anomaly map provide depths to basement of 4.0, 2.0, and 2.9 km. These depths constrain the gravity models along the profiles, which indicate that the sedimentary infill is of variable thickness. Thus, we have three sub-basins along the Goulfey-Turba depression: Goulfey, Tom-Merifine, and Tourba. These sub-basins are of tectonic origin. They are associated with the extension tectonics that have affected the region from the Benue trough to the Chad basin. The Goulfey sub-basin is the deepest one. The sedimentary infill is probably constituted by sandy clayey alluvial deposits, sandstones or shales. Depths to basement were constrained with by spectral analysis results. The basement is granite and gneiss, with basaltic intrusions. The inferred faults are of the normal type.