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In an effort to have better understanding of the geologic settings and structural disposition of the Nigerian basement rocks, Ilorin area, a notably complex region within the Southwestern Basement Complex of Nigeria was studied using aeromagnetic data so that existing knowledge on the geology of the area can be appraised and updated. The aeromagnetic data was enhanced using various techniques which include the Total Horizontal Derivative (THD), Standard Euler Deconvolution, Tilt Derivative and Spectral Analysis. Striking features observed over the Residual Magnetic Field map were NE-SW trending anomalies aligned diagonally and running from the SW to the NE, forming a band having a width of between 16,000 and 20,000 m that coincided with the Banded Gneiss region on the geologic map; conspicuous E-W trending magnetic low whose location lies very close to the boundary between Migmatite and Banded Gneiss; and a ring-like magnetic low occurring in the southeastern part of the residual map with no surface expression on the geologic map. Residual Magnetic Field values ranged from +157 to −202 nT. The THD map showed that the Banded Gneiss was the most deformed unit within the Migmatite-Gneiss-Quartzite complex. Major fractures coincident with Banded Gneiss boundaries appeared to be possible channels from which heat was leached in the regional system during metamorphism such that the Banded Gneiss region attained a relatively lower grade metamorphism than the Migmatite sharing boundary with it. Result from the spectral analysis showed that the magnetic basement in the eastern region was downthrown abruptly relative to that in the western portion. The abruptness was interpreted to mean that such subsidence was fault controlled. The study concluded that the presence of major fractures interfering with metamorphic processes in a regional settings may influence the grades of metamorphism that may result; that the schist region in the study area could be overlying a region of downthrown bedrock; and that the stress pattern that defined the crustal deformation pattern at the near crust in the past had changed compared to the currently dominant pattern.

Regional-scaled gravity data was interpreted for the Central Equatorial Atlantic African region, a region comprising of both oceanic and continental areas, with a view to understanding more about its complex geological settings and the processes of tectonic evolution. The methods adopted involved the generation of topography/bathymetry, free-air and Bouguer anomaly grids from topography, free-air anomaly and Bouguer anomaly datasets; regional-residual gravity field separation, lineament mapping from the Horizontal Derivative and 2-D modelling of the sub-surface. Within the study area, the elevation ranged from-4,200 to 3,840 m. The free-air anomaly map showed a combination of elongated and circular positive free-air anomalies and elongated, negative free-air anomalies whose values varied between-40 mGal and 70 mGal. The Bouguer anomaly values ranged from-121 to +229 mGal. The Bouguer anomaly map also showed both elongated and circular positive and negative Bouguer anomalies. The dominant orientations of the elongated Bouguer anomalies were the NE-SW, the E-W and the ESE-WNW orientations. Gravity modelling within the oceanic region revealed the presence of a basaltic cover whose thickness varied between 1,330 m to 7,700 m in the oceanic and continental margin regions. Associated with the occurrence of this basaltic cover were kinks interpreted as eruption fissures from which the basaltic cover was ejected. It was discovered that the African West Coast Atlantic margin consisted of a trench around the continental margin region adjoined just to the north by some high density basalt, and also that the West African Coastline is heavily laced with magmatism and must have therefore been an active magmatic region in the past. Based on the interpreted data, the study concluded that the Equatorial Atlantic Ocean might have opened on a framework of rifts which extended into the inland regions to form the present day sedimentary basins and from the Bouguer anomaly profile along latitude 10 o N that it is possible that both the Minna batholith and the Jos Plateau exploited the Proterozoic basement weaknesses for their emplacement.

Airy's isostatic residual gravity anomaly map and profiles were interpreted for the central portion of the Equatorial Atlantic African region with a view to understanding the lithospheric dynamics, hence imminent vertical crustal movements and thus predict the future outlook of evolving landscape within the study area. In order to compute the isostatic residual gravity anomaly, the AIRYROOT algorithm of the United States Geological Survey was used and isostatically overcompensated, undercompensated and completely compensated portions were identified on the isostatic residual gravity anomaly map and profiles. The Airy's isostatic residual gravity anomaly map showed three distinct parts which were the oceanic southwestern part characterised by negative isostatic residual gravity anomaly values (− 11 to − 200 mGal), the volcanic eastern and extreme northcentral parts characterised by positive isostatic residual gravity anomaly values (+ 10 to + 90 mGal) and the central part having a network of sedimentary basins, characterised by isostatic residual gravity anomaly values that approach zero (− 10 to + 9 mGal). It was discovered that the oceanic southwestern part was isostatically overcompensated, the uplifted eastern part and the Younger Granite Province of the extreme northcentral part were undercompensated and the central part consisting of the Niger Delta, Benue Trough and the Mid-Niger (Nupe) Trough was completely compensated. It was consequently predicted that vertical uplift is imminent in the isostatically overcompensated oceanic region while subsidence is expected over the region of the eastern upland and the Younger Granite Province which were associated with isostatic undercompensation. The sedimentary basins within the study area are expected to remain stable.

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