Application of VES and VLF-EM methods for groundwater exploration through overburden thickness estimation of aquiferous zones within Kabawa Area, Lokoja Kogi State, Nigeria

The area of study was surveyed to know more about the geology of the area which was characterized by Lokoja Formation, Patti Formation, and Agbaja Ironstone. The geoelectric and electromagnetic survey was carried out at Kabawa with the view to delineate the overburden thickness and aquiferous zone in the area. Geological field mapping were carried out which was accompanied with acquisition of sixteen (16) Vertical Electrical Sounding (VES) data, and ten (10) Very Low Frequency Electromagnetic (VLF-EM) data. The major rocks encountered are sandstones, claystone, and siltstones. Further findings revealed that the VES result showed five (5) geo-electric layers in the area, these layers are the top soil having resistivity and thickness value ranges from 30.2-1194.9 Ωm and 0.3-4.0 m, highly ferruginous sandstone has resistivity and thickness value ranges from 3.6-39.5 Ωm and 1.2-8.3 m, dry sandstone has resistivity and thickness range of 4.4-1043.7 Ωm and 0.5-5.1 m, claystone has resistivity and thickness range of 2.1-1360 Ωm and 0.5-22.1 m, siltstone has resistivity and thickness ranges from 3.9-241.2 Ωm and 0.6-76.8 m, and the water-saturated sandstone has a resistivity ranging from 13.5-431.3 Ωm and an undefined thickness respectively. Generally, the VLF-EM result correlated with what was obtained from the VES data and further confirmed that the water-bearing strata (aquiferous zones) are in the overburden units. Therefore, the integration of geology, VES and VLF-EM techniques served as very important approaches for aquiferous zones delineation