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Groundwater exploration in Ago-Iwoye Area of Southwestern Nigeria, using Very Low Frequency Electromagnetic (VLF-EM) and Electrical Resistivity methods

Very Low Frequency Electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES) method were us... more Very Low Frequency Electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES) method were used to delineate fracture zones for groundwater exploration within the permanent site of Olabisi Onabanjo University, Ago-Iwoye, Southwestern Nigeria which is underlain mainly by suites of gneissic rocks. The VLF-EM survey was made at 10 meters interval along eight (8) traverses at East - West direction ranging from 230 - 500 meters in length. The plot of filtered real and filtered imaginary identified eight (8) prominent fracture zones close to the surface or sub surface which was further delineated by VES method. Seventeen (17) VES soundings were carried out at locations of prominent VLF anomalies presumably typical of basement fracture using AB/2 of 100m. The results shows 3 distinctive geo-electric interpreted layers of sandy top soil, (0.6m to 8.6m, 107.8 m to 662.72 m), underlain by sandy clay/clayey sand (5.7m to 43.5m, 34.7Ωm to 346.8Ωm) which is underlain by fractured/fresh basement (484Ωm to 5651Ωm). The basement fractures identified from VLF-EM anomaly curves were confirmed by geo-electric interpretation of the VES, therefore, the use of the two methods help in identification and delineation of prominent prospective groundwater areas.

Geophysics and Geostatistics methods were combined to quantify the clay deposit in Idofe, Imope, ... more Geophysics and Geostatistics methods were combined to quantify the clay deposit in Idofe, Imope, Iganran, Aparaki and Falafanmu in Southwestern Nigeria. Vertical Electrical Sounding (VES) geophysical method was used to investigate eighty (80) different points on a 250m by 250m grid map. This was aimed at determining the thickness of the clay deposits. Schlumberger electrode array was employed with electrode separation ranging from 50 to 120m. The result was later subjected to geostatistical analysis to estimate the overall thickness of the clay deposit. Experimental variogram with a fitted spherical model was plotted. Model parameters were also determined. These were used as input for clay deposit contour map based on Kriging algorithm. The average thickness of the deposit was determined from the combination of the geophysical survey data and estimate from the contour map. Geophysical results revealed that clay is overlain by top soil and a lateritic horizon. Beneath the clay horizon is the bedrock. Apparent resistivity ranges from 1.8-197.4 Ohm-m for the Clay horizon with 0-39.1m thickness. The Variogram model revealed a range of influence of 342m and a nugget effect of 3m2. These values were incorporated to calculate the volume of the deposit which was estimated to be 35,062,528.

Journal of Geography and Geology, 2014

Hydrogeological assessment of groundwater resources of part of Abeokuta area was carried out with... more Hydrogeological assessment of groundwater resources of part of Abeokuta area was carried out with a view to highlighting the potential of the aquifers to provide portable water supply, chemical character and provenance of the groundwater resources of the area. Seventy-five Vertical Electrical Soundings (VES) were distributed across areas underlain by different rock types. This was complemented with fifty groundwater samples collected from wells and analyzed for the major ions and seventy two minor constituents. Three to five sub-surface geo-electric layers were delineated from the VES. The layers resistivities (Ωm) from top to bottom vary from 24.

Applied Water Science

This study focused on the evaluation of the baseline condition of saline water-groundwater interf... more This study focused on the evaluation of the baseline condition of saline water-groundwater interface in the coastal aquifers along Badagry, southwestern Nigeria. Geologically, Badagry lies within the coastal sands and recent alluvium of the Dahomey Basin. Two-dimensional electrical resistivity tomography (2D-ERT) data along 15 survey lines were acquired in the study area, adopting the Wenner electrode arrays system with minimum spacing of 10 m. Ninety-one water samples were also collected, and their physical parameters were measured using hand-held devices. The (2D-ERT) data were processed and interpreted with the aid of DiProWin software. Sandy topmost layer, freshwater sand, brackish water sand and saline water sand were delineated from the study. Brackish water sand and freshwater sand layers were dominant in areas with high proximity to the Atlantic Ocean located in the south, which were not observed in the northern part of the mapped area. The study established the freshwater-saltwater interface at a depth of 10 m and above, in areas around the coast, while the interface occurs at depth greater than 50 m in areas 3-5 km from the coastal area. Observations from the pH and the TDS show that 87.3% of the samples are slightly acid, while less than 12.7% of them are slightly alkaline, while the TDS vary from 8 to 520 mg/l. The EC of the samples varies from 13 to 1140 µS/cm. All water samples are fresh groundwater, which confirms the occurrence of freshwater aquifer even in areas closer to the Atlantic Ocean.

Geophysical Determination of Subsurface Layers, Characterization of Soil Competence and Corrosivity for Engineering Site Evaluation at Iganran and Environs, Southwest Nigeria

Conference Proceedings on 1st Annual International Conference on Geological & Earth Sciences, 2012

Comparative study of the influence of cement and lime stabilization on geotechnical properties of lateritic soil derived from pegmatite in Ago-Iwoye area, southwestern Nigeria

Journal of Mining and Geology, 2008

Soil investigation was carried out at a proposed dam site across River Ome in Ago Iwoye, southwes... more Soil investigation was carried out at a proposed dam site across River Ome in Ago Iwoye, southwestern Nigeria to investigate the depth to bedrock, possible geologic structures, foundation conditions of the dam axis, abutments and choice of best location for construction of dam. Six Vertical Electrical Soundings (VES) were carried along the river course and this was done using Schlumberger configuration. Evaluation of the engineering properties of the soil was carried out for twelve samples collected across the river using atterberg limit, grain size analysis, California Bearing Ratio (CBR) and compaction characteristics of the soils. The geophysical result showed three geo-electric layers; top sandy layer, clay and weathered/fresh basement. Analysis of the atterberg limit shows a dominance of inorganic clay size particles with high plasticity and moisture content while the grain sizes analysis reveals well graded gravelly clayey silty sand. The soil type classification, CBR and compaction values obtained showed some significant agreement. The values of river discharge were computed during dry and wet seasons and this showed that the magnitude of flood to be averted will pose no challenge on the selection of spillway type. The integration of these methods helped in the choice of location for the dam axis.

Groundwater exploration in Ago-Iwoye Area of Southwestern Nigeria, using Very Low Frequency Electromagnetic (VLF-EM) and Electrical Resistivity methods

Very Low Frequency Electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES) method were us... more Very Low Frequency Electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES) method were used to delineate fracture zones for groundwater exploration within the permanent site of Olabisi Onabanjo University, Ago-Iwoye, Southwestern Nigeria which is underlain mainly by suites of gneissic rocks. The VLF-EM survey was made at 10 meters interval along eight (8) traverses at East - West direction ranging from 230 - 500 meters in length. The plot of filtered real and filtered imaginary identified eight (8) prominent fracture zones close to the surface or sub surface which was further delineated by VES method. Seventeen (17) VES soundings were carried out at locations of prominent VLF anomalies presumably typical of basement fracture using AB/2 of 100m. The results shows 3 distinctive geo-electric interpreted layers of sandy top soil, (0.6m to 8.6m, 107.8 m to 662.72 m), underlain by sandy clay/clayey sand (5.7m to 43.5m, 34.7Ωm to 346.8Ωm) which is underlain by fractured/fresh basement (484Ωm to 5651Ωm). The basement fractures identified from VLF-EM anomaly curves were confirmed by geo-electric interpretation of the VES, therefore, the use of the two methods help in identification and delineation of prominent prospective groundwater areas.

Geophysics and Geostatistics methods were combined to quantify the clay deposit in Idofe, Imope, ... more Geophysics and Geostatistics methods were combined to quantify the clay deposit in Idofe, Imope, Iganran, Aparaki and Falafanmu in Southwestern Nigeria. Vertical Electrical Sounding (VES) geophysical method was used to investigate eighty (80) different points on a 250m by 250m grid map. This was aimed at determining the thickness of the clay deposits. Schlumberger electrode array was employed with electrode separation ranging from 50 to 120m. The result was later subjected to geostatistical analysis to estimate the overall thickness of the clay deposit. Experimental variogram with a fitted spherical model was plotted. Model parameters were also determined. These were used as input for clay deposit contour map based on Kriging algorithm. The average thickness of the deposit was determined from the combination of the geophysical survey data and estimate from the contour map. Geophysical results revealed that clay is overlain by top soil and a lateritic horizon. Beneath the clay horizon is the bedrock. Apparent resistivity ranges from 1.8-197.4 Ohm-m for the Clay horizon with 0-39.1m thickness. The Variogram model revealed a range of influence of 342m and a nugget effect of 3m2. These values were incorporated to calculate the volume of the deposit which was estimated to be 35,062,528.

Journal of Geography and Geology, 2014

Hydrogeological assessment of groundwater resources of part of Abeokuta area was carried out with... more Hydrogeological assessment of groundwater resources of part of Abeokuta area was carried out with a view to highlighting the potential of the aquifers to provide portable water supply, chemical character and provenance of the groundwater resources of the area. Seventy-five Vertical Electrical Soundings (VES) were distributed across areas underlain by different rock types. This was complemented with fifty groundwater samples collected from wells and analyzed for the major ions and seventy two minor constituents. Three to five sub-surface geo-electric layers were delineated from the VES. The layers resistivities (Ωm) from top to bottom vary from 24.

Applied Water Science

This study focused on the evaluation of the baseline condition of saline water-groundwater interf... more This study focused on the evaluation of the baseline condition of saline water-groundwater interface in the coastal aquifers along Badagry, southwestern Nigeria. Geologically, Badagry lies within the coastal sands and recent alluvium of the Dahomey Basin. Two-dimensional electrical resistivity tomography (2D-ERT) data along 15 survey lines were acquired in the study area, adopting the Wenner electrode arrays system with minimum spacing of 10 m. Ninety-one water samples were also collected, and their physical parameters were measured using hand-held devices. The (2D-ERT) data were processed and interpreted with the aid of DiProWin software. Sandy topmost layer, freshwater sand, brackish water sand and saline water sand were delineated from the study. Brackish water sand and freshwater sand layers were dominant in areas with high proximity to the Atlantic Ocean located in the south, which were not observed in the northern part of the mapped area. The study established the freshwater-saltwater interface at a depth of 10 m and above, in areas around the coast, while the interface occurs at depth greater than 50 m in areas 3-5 km from the coastal area. Observations from the pH and the TDS show that 87.3% of the samples are slightly acid, while less than 12.7% of them are slightly alkaline, while the TDS vary from 8 to 520 mg/l. The EC of the samples varies from 13 to 1140 µS/cm. All water samples are fresh groundwater, which confirms the occurrence of freshwater aquifer even in areas closer to the Atlantic Ocean.

Geophysical Determination of Subsurface Layers, Characterization of Soil Competence and Corrosivity for Engineering Site Evaluation at Iganran and Environs, Southwest Nigeria

Conference Proceedings on 1st Annual International Conference on Geological & Earth Sciences, 2012

Comparative study of the influence of cement and lime stabilization on geotechnical properties of lateritic soil derived from pegmatite in Ago-Iwoye area, southwestern Nigeria

Journal of Mining and Geology, 2008

Soil investigation was carried out at a proposed dam site across River Ome in Ago Iwoye, southwes... more Soil investigation was carried out at a proposed dam site across River Ome in Ago Iwoye, southwestern Nigeria to investigate the depth to bedrock, possible geologic structures, foundation conditions of the dam axis, abutments and choice of best location for construction of dam. Six Vertical Electrical Soundings (VES) were carried along the river course and this was done using Schlumberger configuration. Evaluation of the engineering properties of the soil was carried out for twelve samples collected across the river using atterberg limit, grain size analysis, California Bearing Ratio (CBR) and compaction characteristics of the soils. The geophysical result showed three geo-electric layers; top sandy layer, clay and weathered/fresh basement. Analysis of the atterberg limit shows a dominance of inorganic clay size particles with high plasticity and moisture content while the grain sizes analysis reveals well graded gravelly clayey silty sand. The soil type classification, CBR and compaction values obtained showed some significant agreement. The values of river discharge were computed during dry and wet seasons and this showed that the magnitude of flood to be averted will pose no challenge on the selection of spillway type. The integration of these methods helped in the choice of location for the dam axis.