Indication of fault expressions from filtered and Werner deconvolution of aeromagnetic data of the Middle Benue Trough, Nigeria

The aeromagnetic intensity field anomaly of the Middle Benue Trough, Nigeria has been continued upward to an elevation of 100 km above flight height. The results of the calculations are usually free from the effects of inclination of the earth's main field and polarization vector. This was followed by progressive application of low-pass filters and their performance was compared. The upward continued field, which usually reveals the effects of deeper sources, is interpreted to be due to-two juxtaposed magnetic dipoles of dipolar length approximately 200 km. The configuration of the dipoles suggests an asymmetric geometry and has implications for the tensional regimes that prevailed in the area. The general indication is that the sedimentary trough might have resulted from simultaneous strike-slip motion and fault-normal transtension, similar to the way asymmetry is produced in larger transform basins. Depth estimates from five Werner profiles across the Cretaceous cover of the study area reveal variable sedimentary thickness (basement configuration) with the thickness nowhere exceedhig 4.80 km. The basement topography has a NE-SW oscillatory pattern revealing a maximum wavelength of 50 km with a tilted block-faulting pattern in which the anti-forms correspond to the trend of the inter-tonguing basement in some portions of the study area.