Geological and Hydrogeophysical Investigation of Angwan Zakara, Keffi Sheet 208N.E of North Central Nigeria (Published)
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.
Keywords: Assessment, Geologic, Groundwater, hydrogeophysical, potential, quantitative and qualitative
Delineating Saline Water Zones in an Inland Brine Area Using Electrical Resistivity Indicators (Published)
This paper presents results of saline groundwater zone delineation using electrical resistivity sounding. The geologic setting of the study area, Awe Town is that of the Biddle Benue Trough, a structure filled with Cretaceous sediments that include Awe Formation. The town is a predominantly rural area plagued with saline groundwater resulting from brines associated with Awe Formation. As a result of this challenge, water supply scheme for the area was situated about 6km away from the main settlement making access to potable water difficult. The present study was prompted by the need to delineate the extent of groundwater contamination by the brines and in so doing identify aquifers close to the settlement for exploitation. Electrical resistivity method has been applied extensively in delineation of saline groundwater zones. Electrical resistivity surveys were done around the town with the sole aim of delineating the saline groundwater and fresh groundwater regions around the settlement. A total of 20 vertical electrical soundings were carried out using the Schlumberger configuration. Geophysical indicators (longitudinal conductance and transverse resistance (S and T respectively) as well as transverse resistivity (ρt) and longitudinal resistivity (ρl)) were used to assess saline water distribution in the aquifers of the study area. Of the four indicators, Longitudinal Unit Conductance and Transverse Unit Resistance clearly demarcated saline groundwater zones. Contour maps showing the distribution of these indicators aided in the identification of fresh groundwater, 1.2km from the main town. Analysis of borehole logs in the fresh groundwater region revealed fresh groundwater aquifers within Younger rocks i.e. Ezeaku and Keana Formations, which overlie the Awe Formation. Geologic setting of the study area is such that Awe Formation is exposed in the Old Town due to uplift and weathering, while younger rocks of Ezeaku and Keana Formations overlie Awe Formation in the New Town area. Aquifers in these formations have resistivity in the range of 150 to 300Ωm, with thicknesses ranging between 20m and 35m; these zones were interpreted to have high yield potential in terms of quality.
Keywords: Groundwater, Saline, electrical resistivity, inland brine
AZIMUTHAL SQUARE ARRAY RESISTIVITY SOUNDING OF SHALLOW SUBSURFACE FRACTURE DISTRIBUTION IN PARTS OF THE EASTERN BASEMENT COMPLEX OF NIGERIA (Published)
Azimuthal square array resistivity sounding method was carried out at twelve (12) locations within Parts of the Eastern Basement Complex of Nigeria. The field data were collected using ABEM Terrameter with other accessories. For square – array, the location of measurement point is the centre point of the square and array size of 28m and 42m, 56m and 70m were used and each square was rotated in 150 increments about the centre point for a total of 3600.Data were analyzed using Origin pro. 8.0 Software. The results of the study showed the presence of fracture zones and seven (7) of the fracture zones were oriented in the NE – SW direction, while six (6) were oriented in the NW – SE direction indicating that the study area is has good potentials for ground water development.
Keywords: Abem Terrameter, Basement, Fracture, Groundwater, Resistivity, Square Array