Geological and Hydrogeophysical Investigation of Angwan Zakara, Keffi Sheet 208N.E of North Central Nigeria

The geological and hydrogeophysical assessment of the groundwater prospect/potential in Angwan Zakara and its environs, Karu Local Government, Nasarawa State, North-Central, Nigeria has been carried out in this study. The study area covers 25km2.The area is underlain by the Basement Complex of the North-Central Nigeria consisting of Medium grained biotite granite, biotite gneiss, phyllite and un-mappable muscovite schist with structural features such as joints, veins, foliation, faults, and xenoliths trending NW-SE direction. Forty Nine (49) Vertical Electrical Sounding were carried out in the study area using Omega Resistivity Terrameter, GPS12 Garmix with a maximum cable spread of AB/2=100m and MN/2=5m. The results obtained from the field data were interpreted using IXID Software for quantitative analysis. True resistivity map, piezometric map, basement resistivity map and depth to basement map were prepared and interpreted using computer software for qualitative analysis (SURFER 8). From the IXID interpreted results, five (5) curve types were obtained from the acquired data namely A, H, KH, AH, and HK curve types are the dominant. The study area showed depth to basement ranges from 20-90m. That revealed good groundwater potential. The study area revealed 4-7 lithologic sequences consisting of top soil, laterite, clay, weathered/ fractured basement however the host rocks in the study area are biotite granite, quartzite and schistose-gneiss. The results obtained shows that the direction of water flows revealed five ridges R1-R5 and four depressions D1-D4 with receptacles trends of the ridges are R1 and R2:NW-SE; R3 N-S, R4 : NE-SW and R5; E-W. The geoelectric sections were produced and correlated with the geology of the study area and it was found to be in conformity with the each other. Based on this, the study area is zoned into three namely good, moderate and poor groundwater potential zones.