Isotope and geochemical characterization of surface and subsurface waters in the semi-arid Sokoto Basin, Nigeria

Stable isotopes and geochemical studies have been applied in the investigation of groundwater resources in Sokoto Basin, northwestern Nigeria. Generally, the characteristic hydrochemical classification in the study area is calcium-alkali-bicarbonate. Surface waters are characterized by alkali-calcium-bicarbonate while groundwater is of Ca-Mg-HCO3. The plot of δ18O versus δ2H shows that five isotopic groups can be distinguished. Group I-III is of groundwater origin while group IV and V represent surface water. A combination of the hydrochemical and isotope data (14C, 13C and 3H) reveals the Sokoto basin aquifers generally contains good quality groundwater of Holocene age (100 to 10,000 years BP). Key Words: stable isotopes, geochemical characterization, groundwater, Sokoto Basin. African Journal of Science and Technology Vol.4(2) 2003: 80-8

Application of electrical resistivity survey for groundwater investigation in a basement rock region: A case study of Akobo - Ibadan, Nigeria

A geo-resistivity exploration has been carried out for groundwater within the Akobo catchment of the ancient city of Ibadan. The area lies within the basement rock terrain of South Western Nigeria and bounded by  longitudes 3o 51′ – 3o 53′E and latitudes 7o 22′ – 7o 24′N. The exploration was done using SYSCAL KID meter while a total of 10 VES with an average of 46m station interval were completed in 3 profiles by means of Schlumberger configuration with total current electrode spread of 160m. The results revealed that the area is underlain by four geo-electric layers. The top lateritic soil has resistivity values ranging from 28.1 to 481.8 Ωm and thickness of 0.8 to 5.7m. The second layer has sand/clay intercalation with resistivity values varying between 47.7 and 192.5 Ωm and thickness varying between 2.8 and 19.4 m. The weathered/fractured basement has resistivity values from 106.2 to 846.8 Ωm with thickness of 13.2 to 24.9m while the partly weathered/fresh basement layer has resistivities rangingfrom 130 to 856.4 Ωm. The distribution of resistivities in the area shows that the weathered basement has a relatively low resistivity (< 200 Ωm) values in the north-eastern and north-western axis coupled with high thickness values (> 20 m) which suggests the presence of an aquiferous zone. Therefore, this portion of the study area could be highly hydro-geologically promising and maybe recommended for siting groundwater tube.Key words: Geo-resistivity, groundwater, basement rock, borehole and Ibada

Geological and Electrical Resistivity Sounding of Olokonla Area in North-Central Nigeria

Geological mapping and Electrical resistivity sounding were carried out in Olokonla area in Moro Local Government of Kwara State in order to determine the apparent resistivities of the subsurface lithologies and correlate them with the exposed rocks observed during the geological mapping. The studies also delineate the pattern of fractures in the area which form prefential pathways for ground water. Three vertical electrical soundings (VES) were performed radially adopting the Schlumberger electrode configuration, with half-current electrode separation (AB/2) varying from 1m to 100m. Anisotropy polygon was also constructed based on the radial electrical sounding. The geoelectric parameters revealed five subsurface layers which were interpreted as topsoil, lateritic soil, dry sand soil, weathered granite and granite respectively. The geological mapping showed that the area is underlain by crystalline rocks comprising biotite granite, granite-gneiss and migmatite. The anisotropy polygon showed that a major fracture direction along 600 (northeast to southwest) and the coefficient of anisotropy is 0.79. Based on the apparent resistivities and the structural disposition, a potential aquifer was inferred at a depth of 45m. The fracture pattern in the area was constrained to northeast to southwest direction. The data obtained would be useful in borehole drilling for water within the study area.KEYWORDS: Vertical electrical sounding, aquifer, electrical resistivity, anisotropy polygon, geological mapping, fracture patter

Evaluation of Electrical Resistivity Anisotropy in Geological Mapping - A Case Study of Odo Ara, West Central Nigeria.

The study of electrical resistivity anisotropy in rocks has become important in increasing the accuracy of geological mapping using electrical resistivity survey. The study area, Odo Ara near Egbe, west central Nigeria, has been surveyed using electrical resistivity soundings. Sixty Radial Vertical Electrical sounding (RVES) measurements were carried out in the study area which comprises of the banded gneiss, amphibolites, schist and intrusive pegmatites. The aim of the study is to use the electrical resistivity anisotropy properties of the area to resolve its geological setup. The VES data showed a significant presence of electrical resistivity anisotropy. The VES curves obtained were predominantly of 3 geoelectric layer of H-type (ρ1>ρ2<ρ3) curves; the topsoil, sandy clay/ clay layer and fractured basement. The pseudo-sections show a good correlation with the geoelectric section. Moreover, the iso-resistivity and isopach maps also show a significant correlation with the lithological and strike of the rocks in the area but due to the non uniqueness of electrical resistivity, the lithologic difference between the banded gneiss and the amphibolite at the south western part of the area could not be totally resolved. However, the combination of the anisotropy polygons and the iso-resistivity map has reduced the ambiguity inherent in using a single geophysical parameter.Key words: Electrical resistivity anisotropy, radial vertical electrical sounding, anisotropy polygons

Groundwater potential evaluation of a part of Gidan Kwano campus of The Federal University of Technology, Minna, central Nigeria using geoelectric methods

Groundwater potential evaluation of Gidan Kwano campus of the Federal University of Technology, Minna, Central part of Nigeria was undertaken using Vertical electrical Sounding (VES) to provide information about the subsurface lithology and structures with the aim of evaluating its  groundwater potential. A total of 48 VES was made along eight profiles with six sounding stations per profile within an area of about 10km2, using the Schlumberger array configuration. A combination of VES, Horizontal  Resistivity Profile and Sounding – Profiling produced a subsurface  geological appraisal of the study area. The results of the interpretations of VES data were used to produce the Isopach map of depth to Basement and the Fracture map of the study area. The results and the surface geologic map were found to be closely correlated. Fractures located within the study area coincide with the direction of stream flow suggesting that the drainage system is structurally controlled. The VES curves reveal that the area is generally characterized by three geoelectric layers. The top soil layers thickness ranges from 0.2m to 7.4m. The weathered layer has an average thickness of 0.3m to 58.8m. The mean depth to bedrock was computed as 35m. Out of the 48 VES made, 8 VES stations have been selected as priority locations for the development of groundwater resources. The study area has a very high potential for groundwater development. Despite all the limitations of the VES technique, it has been found to be reliable for groundwater exploration in the Basement Complex terrain particularly when the Schlumberger Configuration and combined with computer - aided interpretation for the survey data.Keywords: Vertical Electrical Sounding (VES), Horizontal Resistivity Profiling (HRP), Sounding-Profiling (Pseudosection), Groundwater Potential

A Gradient Analysis-Based Study of Aeromagnetic Anomalies of Some Dikes in the Nupe Basin, Central Nigeria

An aeromagnetic intensity contour map of a part of Nupe Basin of Nigeria was acquired, digitized and analysed. This work was carried out for a better understanding of the study area using the Gradient analysis-based technique to calculate depth to basement and to interpret the aeromagnetic anomaly map of the area. Statistical method of Ajakaiye et al.(1989) was employed to produce a magnetic facies map of the area. Regional-residual separation of the total intensity map was done to produce a residual aeromagnetic intensity data. Depths to the magnetic source bodies were estimated from the profiles obtained from residual data using Pal’s (1985) gradient analysis method. The estimated depths ranged from 0.44km to 1.67km which agrees with those predicted by some earlier workers on the Nupe Basin. These depths fall within the lithospheric layer of the earth and the causative magnetic anomalies body are likely basic intrusives. While this approach appears cheap, accurate and cost-effective, it is recommended that other ground geological and geophysical techniques be applied to further strengthen the assertions made in this work. Keywords: Gradient, Digitized, Aeromagnetic, Intensity, Regional, Residual, IntrusiveNigerian Journal of Technological Research, 8(2), 201

Depth estimates from a ground magnetic survey across a North- South trending geologic structure in a part of the basement complex terrain of Ilorin, west of central Nigeria

No Abstract.Global Journal of Pure and Applied Sciences Vol. 13 (2) 2007: pp. 209-21

Spectral analysis of aeromagnetic anomalis of the Nothern Nupe Basin, West central Nigeria

No Abstract.Global Journal of Pure and Applied Sciences Vol. 14 (2) 2008 pp. 247-25