Electrical Resistivity Tomography for Subsurface Lithology Mapping in Groundwater Exploration at Mosogar, Delta State, Nigeria

The objective of this paper is to apply electrical resistivity tomography for substrate lithology mapping in groundwater exploration in Mosogar, Delta State, Nigeria with five profiles spreading over 100 meters using appropriate standard techniques. The results revealed distinct resistivity zones corresponding to clay, sand, and gravel layers, with implications for groundwater potential. Geoelectric sections identified reveal a diverse lithological sequence, including clayey soils, sandstones, shale, laterite, and mixed clay-sand units, with resistivity values ranging from < 200 Ωm for clayey soils to > 20,000 Ωm for compact sandstone formations. In profile 1 low values of < than 200 Ωm was observed at distances 10 – 20 m to a depth of about 9.94 m and distances 55 m – 75 m to a depth of about 5.00 m from the top soil, while in profile 2,Distinctive zones with low resistivity values were observed at distance 45 m – 65 m to a depth of about 3.00 m from the surface and distance 10 m – 24 m at a depth between about 6.76 m to 9.94 m, with low resistivity values ranging from 40.5Ωm – 150Ωm. The 2D inversion of profile 4 and 5 has resistivity of moderately high magnitude at the top layer and patches of low resistive rocks can be seen across both profiles. The resistivity values from both profiles indicate the possible presence of clayey soil, laterite, sandstone and patches of clay. The results identified the most promising aquifer zone within the resistivity range of1225–7000 Ωm, corresponding to a lithological composition of laterite, shale, and sandstone, at a depth of 9.94 - 17.3 m. This zone exhibited favorable hydrogeological properties, with sufficient permeability for groundwater storage and transmission. The findings highlight the effectiveness of ERT in resolving subsurface complexities and identifying optimal groundwater-bearing zones in sedimentary environments. This study provides critical insights for borehole placement and sustainable groundwater resource management, offering a valuable framework for similar investigations in the Niger Delta and beyond.