Preliminary interpretation of isostatic residual gravity anomalies within the central portion of the Equatorial Atlantic African region

Abstract

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 south-western 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 south-western 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.