Geodynamic Evolution of the Benue Trough: New Constraints from Three-Dimensional Seismic Tomography and Receiver Function Analysis

The geodynamic origin and evolution of the Benue Trough remain unresolved despite decades of investigation, with competing models advocating mantle plume activity, oblique rifting related to the South Atlantic opening, and transform fault reactivation as the primary driving mechanisms. These models make distinct predictions about the structure of the mantle lithosphere and asthenosphere beneath the trough that can be tested using seismic tomographic imaging. This research constructs three-dimensional P-wave and S-wave velocity models of the mantle beneath the Benue Trough by inverting arrival time residuals from 34 teleseismic events recorded at a temporary network of 22 broadband seismometers deployed across the trough axis and flanking basement for 18 months. Complementary receiver function analysis at all 22 stations provides Moho depth and Vp/Vs ratio for constraint of the crustal component. The P-wave tomography reveals a low-velocity anomaly of approximately -1.5 percent in the upper mantle at 60 to 140 kilometres depth beneath the central trough, interpreted as a thermally anomalous upper mantle residual from Cretaceous rifting or younger lithospheric modification. The absence of a continuous low-velocity anomaly beneath the entire trough length argues against a simple plume model, instead supporting a model of segmented decompression melting driven by oblique extensional reactivation of Proterozoic terrane boundaries. These findings provide original geodynamic constraints that reconcile conflicting geological and geochemical datasets in the Benue Trough literature. Keywords: seismic tomography, Benue Trough, geodynamics, receiver function, mantle structure