Integrated Aeromagnetic and Gravity Interpretation for Tectonic Framework and Basement Depth Estimation in Anambra Basin

A comprehensive understanding of the tectonic framework and basement depth distribution in the Anambra Basin is critical for resource exploration and geodynamic interpretation in southeastern Nigeria. This study integrates aeromagnetic and Bouguer gravity data to characterize the tectonic framework and estimate basement depth across the Anambra Basin. High-resolution aeromagnetic data at 500 m line spacing were obtained from the NGSA archives, and gravity data were sourced from the BGI global database supplemented by ground measurements. Aeromagnetic data were processed to generate total magnetic intensity, upward continuation, and first vertical derivative maps. Gravity data were processed for all standard corrections and complete Bouguer anomaly maps were produced. Spectral analysis, 3D Euler deconvolution, and Werner deconvolution were applied to both datasets for basement depth estimation. Depth estimates from Euler deconvolution range from 0.5 km at the basin margins to over 5 km at the basin depocenter south of Onitsha. Basement configuration maps reveal a series of horst and graben structures trending northeast-southwest, consistent with the extensional tectonics of the Benue Trough. Gravity modelling along four regional profiles constrains total sediment thickness and confirms the asymmetric nature of the basin fill. The northeastern and southwestern basin flanks show relatively shallow basement, while the axial zone is characterized by deep, gravity-low responses consistent with thick low-density sedimentary sequences. These results provide an updated tectonic framework and basin architecture model with direct applications in petroleum systems analysis and mineral exploration.

Keywords: aeromagnetics, gravity, Euler deconvolution, Anambra Basin, basement depth