Aeromagnetic Survey as Reconnaissance Technique for Groundwater Exploration in a Typical Southwestern Nigeria Basement Complex

Abstract

This study was aimed at investigating the causes of reported boreholes failureparts in some part of the Federal Polytechnic Ado Campus using aeromagnetic geophysical method. The aeromagnetic geophysical data covering the area was processed to enhance shallow anomalies using different enhancement techniques such as derivatives and wavelength filters. Total Magnetic Intensity ranges from -28 to 201 nT after removing regional component. Residual magnetic anomaly ranges from -21 to 127 nT; First vertical derivative ranges from -0.18 to 0.36 nT/m; Magnetic Analytic signal (AS) ranges from 0.03 to 0.36 nT/m. It was observed, by correlating the magnetic responses and geology of the area, that rocks underlain the area have close magnetic susceptibility. Consequently, the variations of earth’s magnetism are mainly controlled by sediment thickness and suspected linear structures which are major factors in basement complex groundwater exploration. The probable depth to basement in the study area ranges from 8.13 to 74.05 m as revealed by AS and spectral method, which implies thicker regolith in southern part of the study area than northern part. However, linear structures are evenly distributed across the study area. Therefore, the groundwater potential of the southern part of the study area is higher due to regolith thickness. The failed groundwater boreholes that are prominent in northern part of the study area are not located on linear structures. Therefore, basement depth and linear structures should be considered during reconnaissance survey in groundwater exploration in a typical Basement Complex terrain.