Structural trends and basement depths across Nigeria from analysis of aeromagnetic data

Abstract

This study analyses Aeromagnetic Survey Data to delineate magnetic lineaments associated with fault system trends across Nigeria. A High-Pass filter is used to separate the Total Magnetic Intensity's regional and residual components. A filter like Total Horizontal Gradient, Grid Analysis and Tilt Angle derivative are used to enhance the structural trends and fault systems that predominantly trend Northeast-Southwest and East-West. Some of the magnetic signatures on the southern and northeastern Nigeria follow the rift system trend that connects the South Atlantic and inland West Africa. The Euler deconvolution depth estimate of faults range between 1840 and 6321 m (meters) across the region. The Werner deconvolution and two-dimensional forward modelling are used to infer sedimentary thicknesses beneath ten profiles (each profile traverses a major river basin in the country). The estimated depths to basement range between 1500 and 7500 m beneath the Cross-River Basin (in the south) and the Gongola Basin (in the northeast). The Hadejia River Basin in northeast Nigeria is characterised by distinct magnetic anomaly lows and a shallow depth to the basement. Further investigation of this basin is recommended.