Aeromagnetic and Gravity Evidence for Precambrian Basement Architecture Under the Anambra Basin, South East Nigeria

The Anambra Basin is a Late Cretaceous intracratonic basin superimposed on the Precambrian basement of South East Nigeria, and the geometry and structural architecture of this basement fundamentally controls the distribution of overlying sedimentary units, the localisation of structural traps, and the evolution of the petroleum system. This study derives a new basement architecture model for the Anambra Basin using the integration of gravity and aeromagnetic data through advanced processing and modelling techniques. Complete Bouguer anomaly and aeromagnetic total field intensity datasets were obtained from the Nigerian Geological Survey Agency for the basin area spanning Anambra, Imo, Enugu, and Delta states. The gravity data were processed using Parker-Oldenburg iterative inversion to generate a basement depth surface, constrained by two control points from deep exploration wells. Aeromagnetic data were processed using the source parameter imaging method for independent depth-to-source estimates and structural lineament interpretation. The combined basement depth model shows a NE-SW trending depocenter reaching 3,800 metres in the central basin, bounded by NW-SE trending basement faults that exerted first-order control on basin geometry. A previously undescribed basement high of approximately 500 metres structural relief is identified in the northern basin beneath Enugu State, with potential implications for reservoir pinch-out trapping. The basement lineament map derived from the aeromagnetic data reveals a penetrative NE-SW grain consistent with the regional Pan-African structural fabric documented in exposed basement to the north. Keywords: Anambra Basin, basement architecture, gravity inversion, aeromagnetic, Pan-African