Data from Geo-electrical survey using VES (vertical electrical sounding) measurements has been carried out in order to demarcate groundwater zones in Supare Akoko, Southwestern, Nigeria. Presently, the major source of drinking water supply in this area is via shallow hand dug wells and few borehole constructions provided by the government. In order to improve the standard of living of the community and ease the problem of water scarcity in the area, this study was initiated to delineate the groundwater potentials. Twenty (VES) was carried out with ABEM SAS-1000 Terrameter using the Schlumberger electrode array and the result shows three geoelectric layers within the study area. These subsurface layers include weathered layer, the topsoil, partially weathered/ fractured basement and fresh basement. Weathered zones, Valley fills/basement depressions, and fractured zones were the feasible groundwater pockets that were delineated in the study area. A series of bedrock ridges and depressions were delineated within the surveyed area. The isopach map revealed relatively high overburden thicknesses (25 m) within the depressions. The bedrock depressions were observed to be variably fractured. The main aquifer unit constitutes a relatively low resistivity weathered basement. Generally, the groundwater potential was zoned into low, medium and high. The VES station mapped as medium and high groundwater potential zones are viable for groundwater development within the study area. This study has proved to be quite successful for mapping fractures, outrocks types and structural formation which cannot be observed at the surface.

The Basement Complex rocks of Akungba-Akoko, southwestern Nigeria, typically migmatites (M), biotite gneisses (BGN), granite gneisses (GGN), charnockites (Ch), biotite granites (BG) and pegmatites (P), were assessed using ground gamma-ray spectrometry (GRS). This study aimed at determining rocks' radionuclides concentration, alterations, radionuclides mobilization, radiogenic heat production (RHP) rate (first report for the area) and environmental radiation risk to humans. The results of this study were integrated with previous data on the petrography and geochemistry of these rocks, for detailed interpretation. The results of average elemental and activity concentrations for Akungba-Akoko rocks, were 2.66%, 3.16 ppm and 13.98 ppm, and 831.35, 39.01 and 56.77 for 40 K, 238 U and 232 Th, respectively; with increasing rock order of Ch < M < GGN < BGN < P < BG. High radionuclides concentration in the rocks, with exception of charnockites, were determined by high fraction of K-feldspar, plagioclase, biotite and accessory minerals -zircon and monazites. On the other hand, the low radionuclides concentration in the rocks, especially in Ch and M, were aided by the variability of the naturally occurring radioactive elements (NORMs) caused by alterations and mobilization during metamorphism and crystallization processes as suggested by radioelements composite, K/eTh ratio and F-parameter of Efimov analyses. RHP average of 2.03 µ above the crustal average range of 0.8 -1.2 µ may have significantly contributed to the heat flux in the studied area; however, the RHP of charnockites are lower than the crustal range. The absorbed dose rate average of 87.98 was within the permissible range, and other estimated radiological parameters, namely annual effective doses, hazard indices, gamma activity and activity utilization index, were all far below the permissible limit of 1 for these rocks. However, annual gonad dose equivalent (618.874) and excess life cancer risk (1.511 10 ) were above their permissible limits. Due to the high gamma radiations from the pegmatitic and biotite-rich rocks in the studied area, their high usage should be reduced. Hence, periodic monitoring of the study area is advised.

An integrated geophysical (involving two-dimensional [2D] electrical resistivity) and petrophysical study was conducted in the Precambrian Crystalline Basement area of Iwaro-oka Akoko, southwestern Nigeria. Five 2D resistivity profiles, both around the perimeters and inside the dump, were investigated with maximum lengths of 100 m. Results of the resistivity imaging delineated the leachate plumes as low-resistivity zones, with values ranging from 3 Ω m to 55 Ω m. The coefficient of permeability ranged from 4.33 × 10 -6 to 7. 82 × 10 -3 , and the average porosity ranged from 32 Ω m to 169 Ω m, thus indicating migration of leachate plume to the groundwater due to the high coefficient of permeability and the porosity.Key words: geophysical, geochemical, coefficient of permeability, porosity, leachate IzvlečekNa območju deponije odpadkov, ki leži na ozemlju predkambrijske kristalinične podlage pri kraju Iwaro--oka akoko v jugozahodni Nigeriji so izvedli povezano geofizikalno (z uporabo dvodimenzionalne električne upornosti) in petrofizikalno prospekcijo. Na odvalu in v njegovi bližnji okolici so izmerili pet 2D upornostnih profilov dolžine do 100 m. Na podlagi podatkov upornostnih meritev je bilo mogoče omejiti območja širje-nja lužine iz deponije kot cone nizke upornosti v razponu 3 Ω m to 55 Ω m. Količnik prepustnosti in povprečna poroznost se gibljeta prvi v mejah od 4.33 × 10 -6 do 7.82 × 10 -3 in druga od 32 Ω m to 169 Ω m. Visoke vrednosti količnika prepustnosti in poroznosti nakazujejo poti, po katerih odteka lužina v podtalnico.

The integration of Ground Penetration Radar (GPR), magnetic and electrical resistivity methods revealed detailed and cost effective identification of zones of potential archaeological interest at the theatre of war in Igbajo. The Ground Penetrating Radar (GPR) were acquired using the GSSI SIR 3000, the magnetic method were acquired using the proton precession magnetometer while Ohmega resistivity was used to acquire the electrical resistivity data. The applications of geophysical method to delineate the depth and locations of archaeological materials have been demonstrated. The result of the magnetic survey showed regions of high magnetic intensity which indicates the existence of certain buried artifacts; this assisted in the gridding of the Ground Penetrating Radar (GPR) profiles. Significant features were observed on the radargram which correlates with high resistivity anomalies observed on the inversion profile. It was observed that a region of high resistivity values on the inversion coincides with the ground penetrating radar on the radargram. The results show that the region with the highest resistivity between 510-54959 Ohm-m and at depths between 0.5-3 m from the resistivity inversion indicates the possible presence of artifacts which can further be confirmed through excavation

The Vertical Electrical Resistivity surveys in the Sunshine Garden Estate have contributed to a better understanding of the basement complex of Southwestern Nigeria. Nine (9) vertical electrical sounding (VES) using the Schlumberger electrode array were interpreted and the results shows three (3) subsurface geoelectric layers within the study area. These are the weathered layer, topsoil, fresh/fractured basement. Groundwater pockets such as fractured zones, valley fills/basement depressions, and weathered zones were delineated in the study area. Weathered/partially weathered layer and weathered basement/fractured basement were the two major aquifer mapped out and these aquifers are characterized by thick overburden, found within basement depressions. The groundwater potential of the study area was zoned into low, medium and high potentials. Zones where the overburden thickness (which constitutes the main aquifer unit) is greater than 13m and of low clay composition (average resistivity value between 200 - 400Ωm) are considered zones of high groundwater potential. Area where the thickness of the aquifer ranges from 11-13m with less clay composition are considered to have medium groundwater potential and the areas where the thickness of the aquifer is less than 11m are considered to have a low groundwater. The VES station underlained by high and medium groundwater potential zones are envisaged to be viable for groundwater development within the area.