2-D Electrical Resistivity Imaging Survey for Lithological Assessment at Igwete Primary School, Amai, South-South Nigeria

V.C Enebeli,R.E Kolagbodi,C.N Okorafor

doi:10.4314/jasem.v25i5.21

Abstract

Electrical Resistivity Imaging (ERI) is a useful near-surface imaging technique, which mainly include data acquisition, numerical modelling and tomographic inversion. Within the study area, only one – dimensional (1-D) Electrical Resistivity survey has been carried out for Geophysical investigations. Therefore, 2-D ERI survey was carried out at the Igwete Primary School, Amai to provide electrical picture of the subsurface from which discrete bodies and lithology are better revealed vertically and in lateral extent. The 2-D ERT survey data were acquired using the Petrozenith Earth Resistivity meter while employing the Wenner electrode array. The 2-D apparent resistivity data were inverted to obtain true resistivities of the subsurface using res2dinv software running on personal computer. The subsurface resistivity models were displayed as pseudo sections and inverted resistivity section in the form of colour shaded contour maps. The inverse resistivity model images indicate that at a lateral extent in the range (15.00-21.00) m and (33.00-39.00) m, anomalies suspected to be gravel mixed with sand is in place with resistivities of about (254.00-948.00) Ωm. From the geologic section we can infer that a geological formation is observed at a lateral position of (27.00-32.00) m of resistivity in the range (90.00-93.00) Ωm. This structure is inferred to be a clay pocket. The sandy nature of the formation requires that underground water development be sought for at (9.00-15.00) m over a depth (2.30-8.00) m in the sandy environment. Results of 2D resistivity imaging has helped to delineate the lithology which comprise mainly of; sand, sandy clay, clayey sand depositional environment. The resistivity of these lithology falls in the range (90.00-93.00) Ωm with depth to formation of about (2.30-6.00) m.

Highlights

Geophysical methods are employed in the exploration of geological structures and are implemented in a wide range of applications ranging from building, groundwater investigation to the inspection of dams and dike Klimis et al, (1999); Othman, (2005); Savaidisi et al, (1999); Soupios et al, (2006), aiming towards the exploration of geological structure and the determination of physical parameters of the rock formations/units
Electrical geophysical methods are used to determine the electrical resistivity of the earth's subsurface
The use of electrical resistivity tomography applied to environmental studies is well documented (Bernstone et al, 2019). 2-D Electrical Resistivity Imaging survey using the Wenner array was carried out at Igwete Primary School, Amai, South-South Nigeria with the research objective of surveying the lithological profile of the study area

Summary

Introduction

Geophysical methods are employed in the exploration of geological structures and are implemented in a wide range of applications ranging from building, groundwater investigation to the inspection of dams and dike Klimis et al, (1999); Othman, (2005); Savaidisi et al, (1999); Soupios et al, (2006), aiming towards the exploration of geological structure and the determination of physical parameters of the rock formations/units. Electrical geophysical methods are used to determine the electrical resistivity of the earth's subsurface. The resistivity distribution of the subsurface can be interpreted in terms of soil characteristics and/or rock type (lithology) and geological structure. Electrical Resistivity Imaging (ERI) is a near-surface electrical geophysical method that uses direct current to measure the earth's resistivity. It provides 2D and 3D images of the variation in electrical resistivity using electrodes typically placed on the ground surface. The use of electrical resistivity tomography applied to environmental studies is well documented (Bernstone et al, 2019). 2-D Electrical Resistivity Imaging survey using the Wenner array was carried out at Igwete Primary School, Amai, South-South Nigeria with the research objective of surveying the lithological profile of the study area The use of electrical resistivity tomography applied to environmental studies is well documented (Bernstone et al, 2019). 2-D Electrical Resistivity Imaging survey using the Wenner array was carried out at Igwete Primary School, Amai, South-South Nigeria with the research objective of surveying the lithological profile of the study area

Methods

Results

Conclusion