Spectral depth analysis of some segments of the Bida Basin, Nigeria, using aeromagnetic data

Abstract

Spectral depth analysis was carried out on ten (10) of the 2009 total magnetic field intensity data sheets covering some segments of the Bida basin, to determine the depth to magnetic basement within the basin. The data was obtained from the Nigerian Geological Survey Agency and used to produce a composite map of the study area which is situated within latitude 8⁰00'N - 10⁰00'N and longitude 4⁰30'E - 7⁰00'E. Sixteen (16) overlapping blocks were generated from the ten sheets and Spectral depth analysis was performed on each of the blocks. The results delineated two prominent magnetic zones of shallow and deeper depths with the depth to the shallow magnetic sources (h₁) ranging from 0.254km on Block 9 to 1.719km on Block 2, having an average depth value of 0.968km. The depth to the deeper magnetic bodies, h₂, on the other hand, varies between 1.830km on Block 10 and 4.615km on Block 15, with an average value of 3.063km. The shallower magnetic sources were attributed to near surface magnetic sources which could be laterite, ironstones or ferruginous sandstones that intruded into the sedimentary basin close to the surface. The places with deeper magnetic sources were ascribed to intrusions of the magnetic basement into the basin at deeper depths, lateral discontinuities in the basement and other features differing in magnetic susceptibilities such as dykes, faults, fractures, horsts and grabens within the study area. Based on these results, the Kainji (1), Fashe (2), Mokwa (4), Egbako (5), Baro (7), Patigi/Baro (14) and Baro/Gulu (15) spectral blocks with sedimentary thickness values above 3.0km show the greatest potential for hydrocarbon accumulation.

Keywords: Spectral Analysis, Depth to Magnetic Sources, Aeromagnetic data