Geophysical Exploration for Clay in Igbesa Area and Its Environ, Southwestern Nigeria

Aims: A 3-D resistivity survey was carried out in Igbesa area and its environs, a sedimentary terrain of South-western Nigeria.

Materials and Methods: The wenner alpha electrode configuration was engaged throughout this study. Ten profiles were covered; each profile 25 metres apart. A 3-D square grid was generated using parallel 2-D lines. Five transverse lines were in the North –South direction and the others in the West –East direction.

Results and Discussion: An inverse model resistivity value that utilises the smoothness constrained least-squares inversion of RES3DINV software was used. Seven iterations were undertaken and this produces an RMS error of 21.5%. The high RMS error is attributed largely to resistivity variation obtained from the lithological materials within the study area.

Conclusion: From the results obtained, clay was suspected only in a small portion in the east of the first layer which was approximately about 2.50m deep. Associated materials like clayey sand and lateritic clay were delineated at the surface to the third layer (i.e., a depth of approximately 9.0m), and at the surface to the fourth layer (i.e. a depth of about 17.0m) respectively.