Structural Evaluation for Groundwater Within the Crystalline Basement of Ilorin, Nigeria, Using Multisensory Data Techniques

Abstract

Within the hard rock terrains, stream channels are suspected to be controlled by fractures and joints. In the same light, the topographic lineaments and the lineaments observed from the aeromagnetic anomalies are expected to reflect the structural trends within the complex. This study has therefore adopted multi-data sets results first on a regional scale to depict the structural fabric of Ilorin Sheet 223 and then at the chosen location of the University of Ilorin Main Campus, which is made up of the Basement Complex rocks. From the remote sensing map of Ilorin Sheet 223 structural trends have been divided into two: the NE-SW and the NW-SE structural trends. The aeromagnetic anomalies divide the rocks types into metamorphic (low-to-medium magnetic intensity) and igneous (high magnetic intensity) rocks. The resistivity data interpretation reveals the weathered basement at the University of Ilorin ranges from 5m to 20m. The radial sounding results reveal the structural trend to be NW-SE and NE-SW with the interconnection of joints. The radial sounding shows the rock type in the University of Ilorin Campus to be quartzitic, clayey and igneous as judged from the near hexagonal and elongated shapes of the polygons. The results reveal a good agreement between the trends of fractures derived from the radial vertical electrical sounding and that from the lineament maps. Areas with low bedrock resistivity, thick overburden, presence of two or more interconnected fractures, and high co-efficient of anisotropy indicate intense fracturing and thus, indicate areas of high groundwater potentiality and good water quality.