Multi-Step Filtering of High Resolution Aeromagnetic Data for Geological Delineation over Sokoto Basin, Northern Nigeria

The aeromagnetic survey provides a means for prospecting subsurface structures based on the magnetic susceptibility contrast of the underlying materials. It is applied in hydrocarbon study, mineral exploration, environmental monitoring, unexploded ordinance, and geological mapping. In this research, high-resolution airborne magnetic data over Sokoto Basin were acquired, analysed, and interpreted using some selected filters applied in steps to delineate the geologic boundary of the study area. The data, which were acquired in the form of 0.5⁰ × 0.5⁰ square grids, were first knitted to form the composite total magnetic field intensity map of the study area. A hierarchical combination of four carefully selected enhancement filters was then applied to the composite total magnetic field intensity map to enhance regional features. The filters were reduction to the equator, Butterworth, vertical integration, and upward continuation – the algorithms are available in the Oasis Montaj environment. The results obtained showed four distinct regional fields – very high (>100 nT) at the northern part corresponding to the Sokoto Group, high (60-100 nT) at the north-western part corresponding to the Gwandu Formation, moderate (40-50 nT) at the mid part indicting the Rima Group and low (< 40 nT) in the south-eastern part of the area resulting from Continental Intercalaire. It is concluded that the multi-step filter has reasonably delineated the stratigraphic successions in the Nigerian sector of the lullummeden Basin (Sokoto Basin). The filtering was efficacious in resolving the geologic structures, which were not resolved when a single technique was applied in isolation.