Geological and Geophysical Investigation of Groundwater in Parts of Paiko, Sheet 185, North-Central Nigeria

Abstract

Geological and geophysical investigation of groundwater potential was carried out in Paiko town, Niger state. The area is part of the Basement complex of north central Nigeria, comprising of granite-gneiss and granitic rocks varying in grain size, outcropping at different locations within the area. The Schlumberger configuration of electrical resistivity method was employed with a maximum AB/2 of 70m. A total of not less than 33 Vertical Electrical Soundings (VES) were established within the study area. Qualitative and quantitative interpretation of the obtained data were carried out, via visual inspection of the field curve, traditional curve matching involving the master and auxiliary curves as well as the computer iteration (Winresist software) to generate resolution curves. The dominant curve types in the area are: H, HA, and HK curve types. The pre and post drilling data obtained, also indicates the dominance of these curve types. Geoelectric sections generated from the geoelectric logs indicate three major layers exist in the Paiko Basement rocks at various depths. The topmost layer is the Loess unsaturated topsoil with resistivity value ranging between 50 - 125.9?m and a depth of about 0.9-1.5m. The topmost layer is underlain with the slightly weathered/fractured Basement with resistivity values ranging between 90-270?m with a thickness of 4.6-12m to the depth range 15-30m. The last layer is the Fresh Basement unit with resistivity value ranging between 388-1800?m to a fairly infinitive depth. Borehole depth in the study area ranges between 30-60m. The study also revealed that the fractures in the study area are discrete, localized and discontinuous.