Integrated geophysical methods and techniques for studying the perennial springs in Ikanje- Share, Kwara State, Nigeria

Abstract

An integrated magnetic, self-potential (S.P.) and electrical resistivity survey involving magnetic profiling and 1D Vertical Electrical Sounding (VES) electrical imaging techniques were carried out in the transition environment between the Nupe Basin and Southwestern Nigeria Basement Complex at Ikanje-Share in Kwara State, Nigeria. The Ikanje-Share perennial springs started gaining a lot of attention after many travelers and tertiary institutions in Nigeria made it a good choice for their fieldwork exercise. The surveys were done in order to delineate the subsurface layers, determine the geoelectrical characteristics and identify geological structures (e.g., faults and fractures) that are responsible for the perennial spring formation. The magnetic profiling was used as reconnaissance technique to identify lineament features that are favourable to groundwater accumulation and transmission. Some magnetic lineaments were qualitatively inferred from some profiles in the study area. The fault locations coincide with inflection points in S.P. curves and occur as horizontal and consistent planes of discontinuities at depths of approximately 1.25, 4.25, 8.75, 13.15 and 21.25 m, respectively. The VES interpretation results indicated four to five major geologic units, which include: the topsoil/clay/lateritic layer, the lateritic layer, the weathered basement, the weathered/fractured basement and the fresh bedrock. The weathered and fractured basements constitute the main aquifer units and the overburden thickness varies from 5.0 to 16.8 m. The study has shown the usefulness of integrated geophysical methods and techniques in subsurface structural and groundwater development study over the perennial springs in the transition environment between the Nupe Basin and the Southwestern Nigeria Basement complex.