Basement geology derived from gravity anomalies beneath the Benue Trough of Nigeria

New gravity data over the lower part of the Benue Trough revealed two important anomalies that were not recognized from the past gravity data. The anomalies are the central positive gravity of the order of about +40mGal around the area of Oturkpo which is interpreted due to the contribution of an igneous intrusive (2.76g/cc) tentatively syenite intrusion. The other, which is the negative gravity anomaly (-33mGal), is consistent with the rifted Anambra basin where thicker sediment-fill of 8.4km is calculated. The interpretation of the gravity anomalies beneath the Peninsula Nigerian Benue Trough revealed that intrusions are hardly separated from the anticlinal folded axes. This could suggest the unstable geological units of the Peninsula Nigerian Benue Trough. In this paper, we have also mapped some volcanic extrusive bodies around the Gboko basement and Oban massif basement, north of Calabar area.