Evaluation of Electrical Anisotropy within Ladoke Akintola University of Technology campus Ogbomoso, southwestern Nigeria

Abstract

Radial Vertical Electrical Soundings (RVES) were carried out within Ladoke Akintola University of Technology campus, Ogbomoso, Southwestern Nigeria located on Ogbomoso Sheet 222, in order to evaluate the electrical anisotropy of the concealed basement complex rock(s) and its implication on the groundwater potential of the area. The study area is underlain by porphyritic gneiss. Sixteen RVES stations were occupied and four Vertical Electrical Soundings conducted at azimuths of 00, 450, 900 and 1350 at each station using the Schlumberger electrode array with maximum current electrode spread of 100.0 m. The field data were interpreted by partial curve matching and computer iteration. Resistivity maps were constructed and coefficients of anisotropy were determined. The interpretation of the VES data revealed three main geoelectric units namely: the topsoil, regolith, weathered/fresh bedrock. The basement complex rocks beneath the study area are anisotropic. The anisotropy may have been caused by foliation. The inferred structural trends were along NE-SW, NW-SE, E-W and N-S. The coefficient of anisotropy varies from 1.05 to 1.45 with a mean value of 1.21. The low bedrock resistivity observed beneath RVES 14 indicates high groundwater potential. Radial vertical electrical sounding is effective for determining the strikes of foliation of concealed basement rocks in which foliation is predominant. The results of radial electrical sounding could aid geologic mapping in areas where the basement rocks are concealed.