Depth to Basement Mapping using Source Parameter Imaging (SPI): A Case Study from Federal University of Agriculture Abeokuta

Abstract

This research focuses on mapping the depth to the basement and delineating subsurface geological structures within the Federal University of Agriculture, southwestern Nigeria, using Source Parameter Imaging (SPI), a potential field technique. The research leverages ground magnetic data acquired using a Proton Precision Magnetometer, with measurements taken at 5 m intervals across a 100 m × 100 m study area. Data processing, including Total Magnetic Intensity (TMI) mapping, regional-residual separation, and analytical signal analysis, was conducted using Oasis Montaj software to enhance subsurface interpretation. The TMI map revealed magnetic anomalies ranging from 31,814.3 nT to 37,052.5 nT, with high-intensity anomalies in the southwestern and northwestern regions suggesting magnetically susceptible mineral concentrations, while low-intensity zones in the central and northeastern areas indicated sedimentary cover. The residual magnetic map further highlighted intrusive bodies and lithological variations, with anomalies between -2,359.7 nT and 2,712.8 nT. The analytical signal map, unaffected by magnetization direction, identified NS–SE trending discontinuities, likely fault zones, with intensities from 5.2 nT to 859.4 nT. SPI depth estimates ranged from 1.6 m to 9.5 m, revealing shallow magnetic sources (1.6–3.6 m) in the southeastern and northwestern regions and deeper sources (3.6–9.5 m) in the northeastern and southern areas. These findings underscore the undulating basement topography and structural complexity of the study area, which are critical for groundwater exploration and agricultural planning. The study demonstrates SPI’s efficacy in high-resolution basement mapping, offering valuable insights for resource management and environmental sustainability in geologically complex terrains.