Browsing by Author "Olatunji, S"

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    Aeromagnetic and Resistivity Tomography Technique for Investigating Leakage Paths in Apodu Dam, Ilorin Sheet 201, Southwestern Nigeria
    (Alhikmah University, 2021) Olawumi, HB; Olatunji, S; Ajadi, J; Abubakar, HO
    The aeromagnetic and electrical resistivity tomography technique was used to evaluate the foundation conditions and stability of the Apodu earth dam located around Malete, Ilorin Sheet 201, Southwestern Nigeria. The Aeromagnetic data set was interpreted to identify dykes, lineaments, and magnetic sources controlling subsurface geology. The extracted lineament structures were employed to examine features controlling the distribution of surface and subsurface hydraulic substances cum stability of dam slope. Magnetic lineaments' length and parallelism in some areas suggested installation under a tensional stress field along pre-existing zones of weakness.Magnetic susceptibilities are not uniform in the area and were categorized viz: high, moderate, and low. The magnetic intensity range at Apodu dam is -644.19 to 285.40 nT. The northeastern part of the study area where the Apodu dam is located shows little or no sign of faulting and appears to be more stable structurally. Characterization of the Apodu dam subsurface for seepage appraisal using electrical resistivity tomography technique revealed that the dam is well compacted at the surface but with observed low resistivity values indicative of possible occurrences of weakness zones that are water-bearing in some areas of the dam embarkment body at depths of around 8m and 25m. These observed low resistivity zones indicating a water-bearing weakness zone were connected in RTM1 and RTM2, and a possible water pathway was established. This water pathway is indicative of a possible seepage pathway and adequate measures are expected to be made to arrest the situation. In conclusion, Apodu dam is situated in a geologically stable environment as deduced from the aeromagnetic study but its earth embarkment is suspected to possess areas with possible seepage zones as obtained from the electrical resistivity techniques of investigations. There is therefore a need to quickly remedy the dam earth embankment to ensure the longevity of the dam and avert possible failure.
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    Aquifer Vulnerability Evaluation in Southwestern Nigeria from AHP-GODT model using Geo-electrical Derived Parameters
    (Research and Development Center of the Meteorology, Climatology and Geophysics Agency, Indonesia, 2021) Olatunji, S; Emiola, AM; Adebisi, AW
    The study aimed to determine the exposure levels of the subsurface aquiferous layers, owing to the alarming rate of contamination of the groundwater within 8.150 0N - 8.156 0N and 4.244 0E - 4.248 0E. Analytical Hierarchy Process - Groundwater Overlying strata Depth to aquifer and Topography (AHP-GODT) multi-criteria Modeling approach was used. Thus, aquifers' overlying layers, resistivity, and thickness anomalies were determined to generate an aquifer vulnerability map. A multi-criteria decision method of estimated Groundwater confinement, Overlying strata, Depth to Aquifer, and Topography index approach was implemented. Schlumberger's Vertical Electrical Sounding technique was implemented to acquire 30 Vertical Electrical Sounding points under a maximum half-current electrode separation (AB/2) of 65 m. IP2Win geophysical software packages were used to analyze the varying layer resistivity, depth, thickness, and also the sounding curves of the study area. The geologic 2D models, derived from the equivalence electric layers, revealed a maximum of four geo-electric layers. The layers' resistivity and thickness ranges are clayey silt topsoil (52.5-1104 Ωm; 0.5-9.59 m), weathered layer (10.3-804 Ωm; 0.6-12.1 m), fractured basement (5.5-50832 Ωm; 6.7-18.1 m) and fresh basement (8.3-27348 Ωm; infinity m). On the Groundwater Overlying Strata Depth to Aquifer and Topography model scale, the area is generally characterized by the moderate vulnerability. Implying here is that aquifers have a moderate protective capacity in which the overlying strata above the aquifer are mostly impermeable layers (clay and silt) of high thickness and low porosity.
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    Archaeo-Geophysical Investigation of Simulated Settlement: Case Study in a Part of Basement Complex of Nigeria
    (Sultan Qaboos University, Oman, 2022) Olatunji, S; Lawal, OI
    We have used the 2D Vertical Electrical Sounding method and Electrical Resistivity Tomography (ERT) method to map buried artifacts in a simulated settlement, and have shown how the geographical information system could aid future research. Stones, bones, metals, cement bricks, and cement-and-sand mixtures were locally constructed to fit into an African-archaeological setting. Parameters such as the materials’ composition, width, electrical resistivity, height, age, and depth of burial were taken into account before this investigation. The integrated methods employed collected data over the study area along with a pre-calculated dense network of parallel profiles. A total of eight (8) VES points and six (6) ERT profiles were obtained. The analysis and interpretation revealed that the VES yielded poor resolution for small-scale archaeological anomalies and could only be used fractionally for prospection whilst the ERT results were more suitable for delineation due to the high spatial resolution they provided. The field values correlated with other literature values. This research suggests that rapid significant prospection information, of any area under investigation, can easily be obtained from Google Earth time-lapse images and that its results will serve as a thorough reconnaissance in the search of prehistoric activities.
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    ASSESSMENT OF GEOTHERMAL POTENTIAL OF SOKOTO BASIN NORTH WESTERN NIGERIA USING SPECTRAL CENTROID ANALYSIS OF HIGH-RESOLUTION AERO MAGNETIC (HRAM) DATA
    (by School of Science and Technology Education, Federal University of Technology, Minna, 2016) Shehu, AT; Olatunji, S; Lawal, TO
    The work is aimed at estimating depth to the bottom of a magnetic source (DBMS) using spectral analysis of high-resolution aeromagnetic (HRAM) data over Sokoto Basin in the North Western part of Nigeria. The area is bounded by latitude 10.000 to 14.000N and longitude 3.500 and 7.000E with a total area of 111,925 km2. The HRAM data, acquired from the Nigerian Geological Survey Agency (NGSA), were divided into twenty-two (22) overlapping blocks of the size of, 110 × 110km. In the centroid method of estimating DBMS, two power spectrum plots were plotted for each of the twenty-two overlapping blocks. The high-wavenumber part whose slopes lead to the depth to the top of magnetic sources (Zt) and the low-wavenumber part whose slopes lead to the centroid depth of the magnetic sources (Z0). These depth values were subsequently used to determine, DBMS obtained from Zb = 2Z0 – Zt. The results show a variation in DBMS between 11.13 and 27.83 km with an average of 18.57km. The study is found to have geothermal potential in the northcentral part of the study area owing to shallow values of DBMS.
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    Characterization of Petrophysical Properties of Reservoirs in Bima Formation, Northeastern Nigeria: Implication for Hydrocarbon Exploration
    (Department of Geology School of Physical Sciences, Federal University of Technology, Minna, 2021) Omolaiye, GE; Ajadi, J; Olatunji, S; Jimoh, AY; Ubulom, DEN
    Characterization of petrophysical properties of reservoirs in Bima Formation was undertaken to understand their spatial distribution and impacts on hydrocarbon saturation in the highly heterolithic siliciclastic sequence. The study was carried out using nine well logs from Maiduguri and Baga/Lake sub-basins within the Borno Basin. Evaluation of the formation reveals largely undifferentiated to highly serrated and lenticular sand bifurcated by shale beds, which reduced their thicknesses variably from 0.61 to 6.1 m. The shale content in the sand bodies ranged from 11.00% to 88.00%. The formation also has variable porosity values, with calculated total porosity ranged from 10.00% to 35.00%. Similarly, effective porosity values spanned between 2.00 to 24.00%. The irregular porosity values also accounted for a wide range of field average permeability estimates computed for the formation, which measured between 0.03 to 319.49mD. Hydrocarbon saturation also varied from 40.00 to 78.00%. Gas accumulation was encountered in Ga-1, Da-1, Ar-1 and Ye-1 wells. These highly thin serrated sand beds with variable porosity and permeability constitute exploration challenges. The very thinly laminated or serrated alternation of sand and shale beds lithofacies of the Bima Formation is supportive of fluvio-lacustrine depositional environments.
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    Coal Exploration using Electrical Resistivity Method in Some Parts of Benue Trough, Nigeria
    (College of Natural and Applied Sciences, University of Dar es Salaam, 2020) Olatunji, S; Jimoh, AT
    Geoelectrical resistivity sounding technique was used to delineate the occurrence and extents of coal seam. Fifteen points were sounded with Schlumberger configuration in the suspected coal deposit site bounded by longitudes 7.344° E and 7.366° E, and latitudes 7.318° N and 7.33° N. The vertical electrical sounding (VES) data were analyzed and the corresponding geo-electric parameters at various depths were modeled. The earth model within the study area was correlated with available lithology of a nearby mine site. The sounding signatures are KOHK and KHK curve types which revealed five to six distinct geo-electrical equivalent layers. The wet to dry sandy topsoil has resistivity range of 300-1000 Ωm and average thickness of 1.5 m. Next is a layer with higher resistivity range (1000-20000 Ωm). This layer, which extends to 14 m depth, is considered probably to be laterite, patched with sand in some places. Underlain this is a shale formation that laterally sandwiched the coal seam. The thickness and resistivity range of the coal seam is 1.5-3.4 m and 778-103000 Ωm respectively, while the shale domain has resistivity range of 99-898 Ωm. Therefore, it could be concluded that the coal seam occurrence take shale as host rock in the area and the largest deposit appeared at the Eastern part of the area.
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    Cooling Effect of Some Materials in Clay Composite Bricks for Tropical Region
    (School of Environmental Sciences, Modibbo Adama University of Technology, 2014) Alabi, AB; Babalola, OA; Nwankwo, LI; Olatunji, S
    The thermal resistive effect of embedded materials in composite bricks resulting in cooling has been investigated. Different particulate materials and continuously aligned polyethylene fibers were used as supposed thermal resistors in preparing the bricks for houses in the tropical region. The face change in temperature {Outside temperature(T1) – Inner Temperature (T2)} across the brick insulated with particulate wood dust, paper, PVC, palm kernel, glass, and no-material are 27.9, 27.5, 19.0, 24.0, 25.5, and 26.6 °C respectively after 90 minutes and 26.2, 26.3, 17.9, 22.9, 22.8 and 24 °C respectively after 120 minutes. It is observed that ΔT°C after 90 and 120 minutes are higher for wood dust and paper than brick with no material but lower for PVC, palm kernel, and glass. A high face change in temperature indicates a drop in temperature T2, resulting in a cooling effect if used in building bricks. The same cooling effect was observed when continuous and aligned polyethylene fibers were used to make fiber–clay composite bricks. A side of each sample was subjected to the heat of about 70°C and heat transferred was measured at the other side as done for particulate-embedded bricks. Change in temperature ΔT°C was found to increase with the increasing quantity of polyethylene fibers embedded in the samples 34.2°C (0%), 35.4°C (0.5%), 35.5°C (1%), 35.7°C (1.5%), 36.6°C (2%) and 37.4°C (2.5%), these show that heat transfer decreases due to decrease in T2 with the quantity of fiber. The result shows that the effect is continuous and tends to equilibrium and the change in temperature becomes steady with time.
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    Determination of Aquifer Parameters from Resistivity Data: A Case of University of Ilorin Campus, Northcentral Nigeria
    (2021) Onawola, RB; Olatunji, S; Ologe, O; Jimoh, RO
    A total of twenty-one (21) vertical electrical sounding (VES) data were acquired using Pz-02 resistivity meter within the Precambrian basement area of part of Ilorin Metropolis north central Nigeria to evaluate the hydraulic characteristics of aquifers. The Schlumberger configuration with half-current electrode separation (AB/2) varying from 1 m to 60 m was used. The aquifer hydraulic characteristics such as hydraulic conductivity K and transmissivity T (Ωm2) were calculated from the interpreted VES data using the concept of Dar-Zarrouk parameters. The data, processed with computer software IPI2WIN, indicated three to four geo-electric layers, namely; topsoil, clayey (wet to dry), weathered or fractured basement and fresh basement with resistivity values ranging from 130 to 1469 Ωm, 52.6 to 8552 Ωm, 46.2 to 249 Ωm and 454 to 5022 Ωm, respectively. The depth to aquifer ranges between 6.17 m and 24.9 m and the overburden thickness ranges between 4.1 m and 22.7 m. The assessment of the materials above the aquifers showed that longitudinal conductance lies between 0.02 and 0.468 Ωm-1, transmissivity values vary from 246 to 2419.8 Ωm2. The results obtained have offered worthwhile hydrologic information that will aid both exploration and exploitation of the groundwater system of the study area.
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    Edge detection and magnetic basement depth of Danko area, northwestern Nigeria, from low‑latitude aeromagnetic anomaly data
    (Springer, 2019) Salawu, NB; Olatunji, S; Adebiyi, LS; Olasunkanmi, NK; Dada, SS
    This study aims at estimating depths and boundaries of magnetic source bodies, in order to provide an indirect insight into subsurface geologic features within Danko area of Kebbi state. The study area is located within low magnetic latitude. Hence, the total magnetic intensity anomaly map was reduced to the magnetic equator. This is to center magnetic anomalies over their respective magnetic source bodies, which equally makes the interpretation of sources easier. Matched filtering of the reduced-to-equator (RTE) magnetic anomaly map indicates that the anomalies could be represented by two equivalent layers with some additional noise. The estimated mean depths of burial for the regional and residual sources are 1000 m and 500 m, respectively. Horizontal gradient magnitude and tilt derivative methods carried out on the RTE aeromagnetic anomaly map facilitated the identification of two distinct geologic trends bounded by a prominent fault suspected to be the documented Yelwa fault. Furthermore, the analytic signal map showed magnetic basement depth values between 50 and 900 m with an average value of 475 m, indicating a compelling alignment of results with the 500 m depth value for the residual matched filter layer. Several mineral occurrences have been found within the outcropping basement rocks of the study area. Hence, the combined appraisal of source edge locations and magnetic basement depth estimates offers useful information of the underlying basement configuration, which is highly essential for mineral exploration targets that are mostly obscured by regolith cover.
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    ELECTRICAL ASSESSMENT OF AQUIFERS IN THE BASEMENT COMPLEX OF UNILORIN: IMPLICATIONS FOR EXISTING BOREHOLES
    (School of Science and Technology Education, Federal University of Technology, Minna, 2015) Olatunji, S; Ojulari, BA
    Schlumberger 4-electrode array was employed to sound 21 stations. IPI2WIN and Surfer12 software were used to infer lithological series, aquifer thickness, and depth. The aquifer hydraulic conductivity K and transmissivity T were calculated from the VES data using the Dar Zarouk principles. The field curves show that the area has 3 and 4 geo-electric layers. The layers were interpreted as the topsoil (130- 1469 Ωm), clayey (wet to dry) (52.6 – 8552 Ωm), weathered/fractured basement (46.2- 249 Ωm), and fresh basement (454- 5022 Ωm) respectively. The aquiferous zones lie within the second and third layers. The aquifer depth is between 6.17 m and 24.9 m while the thickness ranges from 1.89 to 22.7 m. The longitudinal conductance S ranges from 0.02 to 0.468 Ω-1 and transmissivity T varies from 246 to 2419.8 Ωm2. The results confirmed the functionality of boreholes, such as VES3, sited in areas with maximum aquifers and highest transmissivity T. The NE and NW parts were found most suitable for freshwater exploitations. Low longitudinal conductance which implies low protective cover, in the vicinity of the borehole near VES 6 suggests the contamination claim of its water.
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    ELECTRICAL PROBE OF THE SUBSURFACE GEOLOGY FOR GROUNDWATER EXPLORATION IN IREWOLEDE ESTATE, ILORIN KWARA STATE
    (School of Pure and Applied Sciences Modibbo Adama University of Technology, Yola, 2018) Olatunji, S; Abubakar, HO
    The resistivity method involving an electrical resistivity survey was carried out using Vertical Electrical Sounding in Irewolede Estate of Ilorin west Local Government, Kwara State. This is to map depth to the thickness and the general resistivity distribution of the study area with high groundwater potential. The survey was carried out with Terrameter model DDC-8; a total of eleven VES points and three profiles respectively were covered. The survey lies within the crystalline basement complex of western central Nigeria and is bounded by latitude 080 27’ 40” N, 080 27’ 45“and longitude 40 33’ 11”, 40 33’ 14” E. The resistivity value was obtained between 2 Ωm to 3000mΩ for profiles 1-3. Four prominent geoelectric layers with varying resistivity and thickness were delineated on all the VES points. The first layer has a resistivity value ranging from 48 Ωm to 934 Ωm with their thickness ranging from 0.5m to 1.0m. This layer is the top soil which contributes to the development of groundwater because it is the passage for the flow of surface water to the fractured subsurface layers. The resistivity value of the second layer dominated by laterite ranges between 7.39Ωm to 2479Ωm while the thickness varies between 1.0m to 11.4m. The third layer resistivity values range between 23.4 Ωm to 255 Ωm with variations in their thickness that range between 3.7m to 29.7m. This and the next layer are believed to contain the aquiferous layer. The fourth layer is the fractured basement, which is believed to be a porch for the underground water. The depth of the aquifer in the area ranges between 3.7m to 29.7m. Overburden is the thickness (about 30m) around the southern part of the area.
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    Estimation of Aquifer Hydraulic Characteristics from Surface Geoelectrical Methods: Case Study of Rima Basin, North Western Nigeria
    (Springer, 2013) Olatunji, S; Musa, A
    Forty vertical electrical resistivity soundings (VES) were acquired, using a Schlumberger array. Three soundings were additionally made at existing boreholes in the vicinity of the study area for comparison. Since the area is a basement complex terrain, a maximum current electrode spacing of 200 m which is believed to probe down to the fresh basement in the area was used. This is believed to enable fresh basement in the area to be observed. The concept of Dar Zarrouk parameters (transverse unit resistance and longitudinal conductance in porous media) was used to determine aquifer hydraulic characteristics in the sedimentary formation underlying the area. The results of the interpreted VES data using a combination of curve matching techniques and computer iterative modeling suggest that the area is underlain by between 3–5 geoelectric layers. The geologic sections derived from the equivalent geoelectrical sections revealed lithologic sequences of mostly five layers. However, there are minor isolated cases of three layers. The geoelectrical sections showed that the resistivity of the aquifer varies between 14.1 and 128.8 Ω m. The thickness of the aquifer ranges from 1.0 to 48 m while its depth from the surface lies between 1.0 and 50 m. Relationships between aquifer characteristics and the geoelectrical parameters revealed the hydraulic conductivity K and transmissivity T variations to be 3.10–28.34 m/day and 10.0–796.6 m2/day, respectively. The maximum K and T occur around VES 4 and 14; thus the maximum yield could be expected around VES 4 and 14
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    Estimation of Aquifer Hydraulic Characteristics from Surface Geoelectrical Methods: Case Study of the Rima Basin, North Western Nigeria
    (Springer, 2013) Olatunji, S; Musa, A
    Forty vertical electrical resistivity soundings (VES) were acquired, using a Schlumberger array. Three soundings were additionally made at existing boreholes in the vicinity of the study area for comparison. Since the area is a basement complex terrain, a maximum current electrode spacing of 200 m which is believed to probe down to the fresh basement in the area was used. This is believed to enable fresh basement in the area to be observed. The concept of Dar Zarrouk parameters (transverse unit resistance and longitudinal conductance in porous media) was used to determine aquifer hydraulic characteristics in the sedimentary formation underlying the area. The results of the interpreted VES data using a combination of curve matching technique and computer iterative modeling suggest that the area is underlain by between 3–5 geoelectric layers. The geologic sections derived from the equivalent geoelectrical sections revealed lithologic sequence of mostly five layers. However, there are minor isolated cases of three layers. The geoelectrical sections showed that the resistivity of the aquifer varies between 14.1 and 128.8 Ω m. The thickness of the aquifer ranges from 1.0 to 48 m while its depth from the surface lies between 1.0 and 50 m. Relationships between aquifer characteristics and the geoelectrical parameters revealed the hydraulic conductivity K and transmissivity T variations to be 3.10–28.34 m/day and 10.0–796.6 m2/day, respectively. The maximum K and T occur around VES 4 and 14; thus the maximum yield could be expected around VES 4 and 14.
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    Evaluation of Groundwater Level Time-Dependent Variation and Aquifer Characteristics within Sheet 223 Ilorin North-West, Southwestern Nigeria
    (Faculty of Physical Sciences, Chukwuemeka Odumegwu Ojukwu University, 2022) Ajadi, J; Issa, U; Olatunji, S
    The assessment of groundwater level time-dependent variation and aquifer characteristics has been carried out, aimed at knowing the variation in groundwater elevation at the end of the rainy season and at the peak of the dry season. The time-dependent variation was done by direct in situ groundwater level measurement from eighty existing wells. Aquifer characteristics were determined by using pumping test data of the available boreholes in the area, using modified Jacob's method. Configuration of groundwater level contours shows that the highest groundwater elevation in the area is 445 m and the lowest is 295 m above sea level. Also, areas with water levels ranging between 1 and 2 m are areas of low water level while areas with water levels ranging between 9.5 m and 11 m are areas of high water level. Transmissivity is estimated to range between 3.49 and 8.50 m2 /day with an average vale of [5.61 m2 /day, Hydraulic conductivity range between 2.18 × 10-1 and 7.64× 10-2 m /dav with an average value of 1.65 x 101 m /day and Storativity range from 3.45 to 9.15 with an average value of 5.04. Areas with the shallow water level, depicting high potential, are in the southern part while the northern part is an area of low groundwater potential. The average value for Storativity is higher than the assigned limit (0.005-0.00005) for most confined aquifers, indicating that the storage potential of the boreholes is high; hence their recharge potential is high.
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    Evaluation of Groundwater Level Time-Dependent Variation and Aquifer Characteristics within Sheet 223 Ilorin North-West, Southwestern Nigeria
    (Faculty of Physical Sciences, Chukwuemeka Odumegwu Ojukwu University, 2022) Ajadi, J; Issa, U; Olatunji, S
    The assessment of groundwater level time-dependent variation and aquifer characteristics has been carried out, aimed at knowing the variation in groundwater elevation at the end of the rainy season and at the peak of the dry season. The time-dependent variation was done by direct in situ groundwater level measurement from eighty existing wells. Aquifer characteristics were determined by using pumping test data of the available boreholes in the area, using a modified Jacob's method. Configuration of groundwater level contours shows that the highest groundwater elevation in the area is 445 m and the lowest is 295 m above sea level. Also, areas with water levels ranging between 1 and 2 m are areas of low water level while areas with water levels ranging between 9.5 m and 11 m are areas of high water level. Transmissivity is estimated to range between 3.49 and 8.50 m2 /day with an average value of [5.61 m2 /day, Hydraulic conductivity range between 2.18 × 10-1 and 7.64× 10-2 m /day with an average value of 1.65 x 101 m /day and Storativity range from 3.45 to 9.15 with an average value of 5.04. Areas with shallow water levels, depicting high potential, are in the southern part while the northern part is an area of low groundwater potential. The average value for Storativity is higher than the assigned limit (0.005-0.00005) for most confined aquifers, indicating that the storage potential of the boreholes is high; hence their recharge potential is high.
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    EVALUATION OFOF WIND ENERGY POTENTIAL IN ZARIA METROPOLIS
    (Faculty of Science, Obafemi Awolowo University, 2013) Olatunji, S; Sanusi, Y
    Meteorological data were acquired from the Nigerian College of Aviation, Technology Zaria. The station is located at Longitude 070 411 E, Latitude 110 081N, and an elevation of 686 m above sea level. Diurnal wind speeds and direction were recorded with Wind Vane and Anemometer from 1995 through 2004. The readings were usually taken twice daily at 10.00 am and 4.00 pm. A total of 6856 direction counts were recorded throughout the years. The north-easterly wind had 3050 direction counts, representing 44.5%. A maximum wind speed of 2.35 m/s was obtained at a height of 2.5 m while 3.0 m/s was obtained at 10 m above the earth’s surface showing speed enhancement with height. The available wind power in the area was 16.46 w/s-2 but the maximum average extractable wind power per unit area was 9.76 w/m2. It was also observed that the dry season (High North-East (NE)wind period), normally runs from the months of November to February whereas the rainy season (High South-West (SW) wind period) ran from the months of May to September. In spite of the low available power, exploitations could be enhanced at a higher level above the earth’s surface. Maximum output was expected within the months of November and February when the dominant north-easterly wind was high and consistent.
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    Geo-Electrical Delineations within Kubanni Basin, North Central Nigeria
    (Springer, 2012) Olatunji, S; Osazuwa, IB
    The research site is the whole landmass of the Federal College of Education, Zaria, seated on the basement complex of north-central Nigeria. Direct current resistivity geophysical method was employed to characterize parameters such as the basement depth and topography, aquifer depth and thickness, weathered basement distribution as well as mapping of orientations of fractures and faults present in the premises using the radial sounding technique. The conventional vertical electrical sounding (VES) Schlumberger array was carried out at 40 stations, eight of which were radial stations. Radial sounding was used to establish resistivity anisotropy which gives clue for the choice of consistent VES profile direction used throughout the fieldwork. Results from the resistivity interpretation suggest three layers in most parts of the premises with some minor occurrence of two and four layers. The first layer (topsoil) has a thickness ranging between 3.5 and 14.0 m; the second layer (weathered basement) thickness ranges between 9.0 and 36.5 m, while the third layer (fresh basement) is deepest (40.1 m) towards the eastern corner of the area. The aquifer depth ranges from 1.5 to 4.0 m with a thickness range of 5.0 to 14.0 m. The thickest aquifer occurs around the center to the west of the area. Results from radial sounding show the presence of resistivity anisotropy, an insight into fracturing and faulting; this is more pronounced around the west-central part of the premises
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    Geoelectrical Viability Characterization Of Existing Boreholes
    (Faculty of Physical Sciences, Chukwuemeka Odumegwu Ojukwu University, 2022) Olatunji, S
    Vertical electrical sounding (VES) technique was conducted at the vicinities of 21 boreholes in the premises of the University of Ilorin; to evaluate general conditions of the boreholes. Data processing was done using the IPI2WIN package. The borehole hydraulic characteristics such as hydraulic conductivity K and transmissivity T were calculated from the interpreted VES data using the concept of Dar-Zarrouk parameters. The 2D sections obtained, indicated a maximum of four geologic equivalence of geo-electric layers namely Topsoil, Laterite, Weathered Basement, fractured basement with resistivity values ranging from 2.3 - 365.7 Ωm, 15 – 731 Ωm, 7.4 - 298 Ωm and 120 - 1500 Ωm respectively. The aquifer depth ranges between 0.91 m and 70 m and the overburden thickness ranges between 0.5 m and 7.2 m. The aquifer thickness ranges between 5.61 and 37.5 m. The materials above the aquifers showed that longitudinal conductance lies between 0.033 and 2.703 Ω-1 while transmissivity values vary from 0.0336 to 2.703 Ω-1. Borehole at VES 3 is considered to stand the best chances as it falls in the vicinity of the largest transmissivity and longitudinal conductance, deepest and thickest aquifer, which makes it free from sewage and surface contamination. The borehole at VES 6 is least suitable as the aquifer is shallow and characterized by low longitudinal conductance, implying low protective cover. This conformed to the reality on the ground, as it has been confirmed contaminated and prohibited from consumption.
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    Geomagnetic Assessment of the Igbeti Marble Deposit (Nigeria)
    (Springer, 2019) Olatunji, S; Adebisi, WA
    The Magnetic Intensity data of aeromagnetic survey, as conducted by Nigerian Geological Survey Agency, were acquired from sheets 200 and 201 for qualitative and quantitative interpretation purposes. The area is bounded by latitudes 8.5°N–9.0°N and longitudes 3.5°E–4.5°E covering an area of about 6150.50 km2. The data were reduced off the regional field to obtain the residual field. Upward continuation and analytical signal were employed for qualitative interpretations. In addition to Euler and Werner Deconvolutions, spectral depth analyses were carried out to estimate the depth to causative geologic structures and basement of the target marble deposit. The residual field contour shows an intensity ranging from −63.05 to 52.65 nT, indicating series of magnetic highs and lows. The obtained positive residual anomalies could stand as responses to the outcrops common in the area, while the negative field could be associated with the presence of granitoids and felsic volcanic rocks or major fault zones. The reached result prove to reveal minimum and maximum depths of 1.07 and 3.79 km, suggesting an expected thickness extent of the deposit. Further Depth estimate around the current mining appears to range from 2.0 to 2.2 km.
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    Geophysical Assessment for Characterising Leakages from Asa dam, Nigeria
    (Faculty of Pure and Applied Sciences, Ladoke Akintola University of Technology, 2021) Olawumi, HB; Olatunji, S; Ajadi, J; Abubakar, HO
    Aeromagnetic and Electrical resistivity tomography techniques were used to evaluate the foundation conditions and stability of the Asa earth dam located in Ilorin. The Aeromagnetic data set was interpreted to identify dykes, lineaments, and magnetic sources that are controlling the subsurface geology. The extracted lineament structures were employed to examine features that are controlling the distribution of surface and subsurface hydraulic substances which affects the stability of the dam. The nature of the magnetic lineaments in some parts of the area suggests rock emplacement under a tensional stress field. Magnetic susceptibilities are not uniform in the area and were categorized viz: high, moderate, and low. The magnetic intensity range at Asa dam is 126.56 to -20.90 nT. The northwestern part of the Asa dam area shows little or no sign of faulting and appears to be more stable structurally than the other part of the study area. Characterization of Asa dam earth embankments for seepage appraisal using resistivity tomography technique revealed that the Asa dam is well compacted with no sign of any seepage. In conclusion, the Asa dam is situated in a geologically stable environment as deduced from the aeromagnetic study, while the earth embankments are well compacted with no sign of seepage as obtained from the electrical resistivity tomography technique of investigations