Lithostratigraphic Characterization of the Subsurface Soil and Lithological Identification Using Electrical Resistivity Method’ on Ovade Community of Oghara, Southern Nigeria

Abstract

This research is carried out to determine the lithostratigraphic characterization of the Subsurface Soil and lithological identification using Electrical Resistivity Method’ on Ovade Community of Oghara, Southern Nigeria. The study area is located between latitudes 5°38'37.782"N to 5°58'33.894"N and longitudes 5°41'20.32"E to 5°41'17.52"E. The geophysical prospecting method adopted for this study is the Wenner Survey profiling and Vertical Electrical Sounding (VES) techniques of the Electrical resistivity method which ABEM SAS-300C Terrameter was used determine to the stratigraphy of the subsurface soil and identify the lithology and determine drilled depth to groundwater.  The data were analyzed using IX1Dv3 and Dipro software. The 2-D Resistivity structure reveals five (5) layers in the subsurface of the study area which are the lateritic soil (clay), fine to coarse sand, very coarse sand, weathered zone and Bedrock. The clay materials presence in the subsurface soil has apparent resistivity ranges from 286 – 414 Ωm. The aquifer zone is revealed to be at 25m to 50m depth with resistivity range of 511 - 2688Ωm. The aquifer is not contaminated with any leachate plume. The VES reveals Seven (7) geoelectric layers. The apparent resistivity ranges from 1221 Ωm to 9948.7 Ωm, overburden has a thickness range from 0.94013 m to 2.5055 m and depth ranges from 0.94013 m to 3.4456 m. The VES reveals that the third, fourth, fifth and sixth geoelectric layer is sand with little presence of gravel with an average thickness range of 15.088 m to 87.252 at depth range of 18.534 m to 87.252 m with resistivity range of 1396.7 Ωm to 9948.7 Ωm. The recommended drilled depth to groundwater is 53m (174 ft) and 72 m (240 ft) resistivity respectively. The first aquifer is for shallow well and second aquifer is for deep well. The curve type is AKH curve. From the results of 2D and 1D resistivity structure, the study area is predominantly Sand and little presence of clay materials before the aquifer zone. The study will provide detail information about the presence of clay materials which is a disadvantage to water from hand dug wells and building foundation.