Geophysical Investigation for the Delineation of Lithology at Novena University, Ogume, Delta State Using the Vertical Electrical Sounding (VES) Method and Electrical Profiling
Publication Date : 10/05/2022
Lithology is the basis of subdividing rock sequences into individual lithostratigraphic units for the purposes of mapping and correlation between areas. Geophysical investigation for the delineation of lithology has been carried out at Novena University, Ogume, Delta State using the Vertical Electrical Sounding (VES) method and electrical profiling. The major aim of this research work is to obtain the internal distribution of physical properties of a subsurface geological structure or materials within the study area so as to guide against the challenge of dry water wells, effective drainage channels and other geotechnical issues. The VES was acquired using Schlumberger array. For Profiling, data acquisition was executed with 5m inter electrodes spacing in Wenner configuration. The Petrozenith Earth Resistivity Meter was used for the field measurement in both cases. For the VES, the apparent resistivity data were input into IP2WIN software running on personal computer. The data was inverted to obtain the subsurface true resistivity. The VES reveals that at a probing point of about 10.11m, a resistivity less than 100? m was encountered originating from the surface. This suggests that the near surface layer is made up of sandy clay / clay just underlain by an unsaturated coarse sand. Beneath it is a high resistivity material of 6857? m. The high resistivity is probably due to very low water content since the upper layer, sandy clay and clay has very low permeability for water to reach the coarse sand layer. The line plot gotten from the profiling indicates that the near- surface geologic section investigated is not homogeneous. The curve of profile 2 is more irregular than that of profile1. This is most likely due to lateral changes in water content, sand grading, clay content and mineralogical compositions or texture of near surface sand changes laterally.
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