1        Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications                      (IJE...
1               Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications                   ...
1             Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications                     ...
1           Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications                       ...
1                                       Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applica...
1                          Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications        ...
1                     Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications             ...
1          Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications                        ...
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  1. 1. 1 Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1154-1161 Subsurface Stratigraphic Mapping Using The D.C Electrical Resistivity Around Shika, Kaduna State, Nigeria. 1 Fadele S.I , 2Jatau B.S and 3Patrick N.O 1 Department of Physics (Applied Geophysics), Ahmadu Bello University, Zaria, Nigeria. 2,3 Department of Geology and Mining, Nasarawa State University, Keffi.ABSTRACT Electrical resistivity investigation was detection of the surface effects produced by the flowcarried out around Shika, Kaduna state, Nigeria of electric current inside the earth. The electricalin order to delineate the subsurface geologic strata techniques have been used in a wide range ofwith a view of determining the depth to the geophysical investigations such as mineralbedrock and thickness of the geologic strata. exploration, engineering studies, geothermalVertical Electrical Sounding (VES) using exploration, archeological investigations, permafrostSchlumberger array was carried out at eighteen mapping and geological mapping. Electrical methods(18) VES stations. ABEM terrameter (SAS 300) are generally classified according to the energywas used for the data acquisition. The field data source involved, i.e., natural or artificial. Thus, selfobtained have been analysed using computer potential (SP), telluric current come under naturalsoftware (IPI2win) which gives an automatic source methods, while resistivity, electromagneticinterpretation of the apparent resistivity. The VES (EM) and induced polarization (IP) methods areresults revealed heterogeneous nature of the artificial source methods. The electrical d.c resistivitysubsurface geological sequence. The geologic method used in carrying out the present survey is ofsequence beneath the study area is composed of artificial source using the ABEM terrameter (SAShard pan top soil (clayey and sandy-lateritic), 300). Appraising the hydrogeology in Zaria, Danladiweathered layer, partly weathered or fractured (1985) has confirmed the presence of water bearingbasement and fresh basement. The resistivity fractures, which aquifers are located at a shallowvalue for the topsoil layer varies from 60Ωm to basement area of Zaria. McCurry (1970), who373Ωm with thickness ranging from 1.06 to 4.14 studied the geology of Zaria, has established that them. The weathered basement has resistivity values Basement Complex rock is made up of the Olderranging from 70Ωm to 708Ωm and thickness of Granite, Biotite granite-gneiss.between 1.77 to 33.04 m. The fractured or partly Farouq (2001), carried out geoelectricweathered basement has resistivity values ranging investigation of the groundwater potential in thefrom 318Ωm to 834Ωm and thickness of between Institute for Agricultural Research Farm, Samaru,12.9 to 26.3 m. The fresh basement (bedrock) has Zaria, showed that the thickness of the weatheredrelatively high resistivity values ranging from basement around the area varies from 3.4 to 30.4 m1161Ωm to 3115Ωm with infinite depth. However, and depth to fresh basement was 40 m. Similarly,the depth from the earth’s surface to the bedrock Saminu (1999), carried out a comprehensivesurface varies between 3.32 to 36 m. The study geophysical survey over the premises of Federalfurther stressed the importance of the findings in College of Education, Zaria, showed that theengineering, groundwater exploration and waste thickness of the top soil of the area ranges betweendisposal problem. 3.5 and 14 m while the thickness of the weathered basement ranges between 9 and 36.5 m. The depth toKeywords: Electrical Resistivity, Vertical Electrical bedrock varies from 5 to 14 m. In this study,sounding (VES), Top soil (TP), Weathered basement electrical resistivity investigation covering eighteen(WB), Partly Weathered Basement (PWB) and Fresh stations have been carried out and interpreted fullyBasement (FB). around Shika, Kaduna State, Nigeria, in order to map or delineate the subsurface geologic strata with aINTRODUCTION view of determining the depth to the bedrock and The use of geophysics for engineering thickness of the geologic strata. The study furtherstudies and water groundwater exploration has stressed the importance of the findings inincreased over the last few years due to the rapid engineering, groundwater exploration and wasteadvances in computer softwares and associated disposal problem.numerical modeling solutions. The Vertical ElectricalSounding (VES) has proved very popular with GEOLOGY OF THE STUDY AREAgroundwater prospecting and engineering The study area is part of the NW basementinvestigations due to simplicity of the techniques. terrain underlain by basement rocks of PrecambrianThe electrical geophysical survey method is the age. They are mainly granites, gneisses, and schists. 1154 | P a g e
  2. 2. 1 Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1154-1161 Oyawoye (1964) showed that there is structural stations. A regular direction of N-S azimuth was relationship between this Basement Complex and the maintained in the orientation of the profiles. rest of the West African basement. This is partly due Overburden in the basement area is not as thick as to to the fact that the whole region was involved in a warrant large current electrode spacing for deeper single set of orogenic episode, the Pan African penetration, therefore the largest Current electrode orogeny, which left an imprint of structural similarity spacing AB used was 200m, that is, 1/2AB=100m. upon the rock units. The gneisses are found as small The principal instrument used for this survey is the belts within the granite intrusions, and are also found ABEM (Signal Averaging System, (SAS 300) east and west of the batholiths (McCurry, 1970). The Terrameter. The resistance readings at every VES biotite gneiss extends westwards to form a point were automatically displayed on the digital gradational boundary with the schist belt. The gneiss readout screen and then written down on paper. continues eastwards to some extent and is occasionally broken up by the Older Granite (Wright RESULTS AND DISCUSSION and McCurry, 1970). The geometric factor, K, was first calculated for all the electrode spacings using the formula; K= π SITE DESCRIPTION (L2/2b – b/2), for Schlumberger array with MN=2b The study area is bounded approximately by and 1/2AB=L. The values obtained, were then longitudes 7031’50’’E and 7034’40’’E, latitudes multiplied with the resistance values to obtain the 11010’07’’N and 11012’10’’N as shown in location apparent resistivity, ρa, values. Then the apparent map (Fig 1) with an average elevation of 685m above resistivity, ρa, values were plotted against the sea level.. The area falls within the semi-arid zone of electrode spacings (1/2AB) on a log-log scale to Nigeria (Harold, 1970). It lies in the guinea obtain the VES sounding curves using an appropriate savannah; the woodland vegetation is characterized computer software IPI2win in the present study. by bushes generally less than 3m high. Some sounding curves and their models are shown in Fig 2. Similarly, geoelectric sections are shown in Figs. 3 and 4. Three resistivity sounding curve types were obtained from the studied area and these are the H (ρ1>ρ2< ρ3), A (ρ1< ρ2<ρ3) and KH (ρ1>ρ2< ρ3>ρ4) type curves. The results of the interpreted VES curves are shown in Table 1. The modeling of the VES measurements carried out at eighteen (18) stations has been used to derive the geoelectric sections for the various profiles. These have revealed that there are mostly four and three geologic layers beneath each VES station. The geologic sequence beneath the study area is composed of top soil, weathered basement, partly weathered/fractured basement, and fresh basement. The topsoil is composed of clayey and sandy-lateritic hard pan with resistivity values ranging from 60Ωm to 373Ωm and thickness varying from 1.06 to 4.4 m, the strata is thinnest at VES 12 and thickest at VES 17. It is however, observed from the geoelectric sections that VES 1, 2 and 7 are characterized with low resistivity values varying between 60Ωm to 85Ωm suggesting the clayey nature of the strata in these areas are possibly high moisture content. The second layer is the weathered basement with resistivity and thickness values varying between 70Ωm and 708Ωm and 1.77 to 33.04 m respectively. This stratum is thickest at VES 15, suggesting this point for siting borehole but thinnest at VES 7. Other points with probable high water potentials viable for siting borehole include:Fig 1: Location map showing the study area VES 2, 3, 5, 9, 10, 11, 13, 14, 15 and 17 respectively with appreciable thickness (12.7 - 33.04 m) of (From Northern Nigerian Survey Map) weathered or fractured rock also known as aquifferous zone. The third strata are the partly METHODOLOGY weathered or fractured basement with resistivity and Vertical Electrical Soundings (VES) using thickness values varying between 318Ωm to 834Ωm Schlumberger array were carried out at eighteen (18) and 12.9 to 26.3 m respectively. The strata are 1155 | P a g e
  3. 3. 1 Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1154-1161 extensive and thickest at VES 3 and thinnest at VES fissures or pore spaces that enhance groundwater 11. The fourth layer is presumably fresh basement permeability and storage hence suggesting these whose resistivity values vary from 1161Ωm to points for siting borehole. To ensure safety 3115Ωm with an infinite depth. However, the depth consumption of groundwater in the area, potential from the earth’s surface to the bedrock surface varies sources of contamination site should be sited far between 3.32 to 36 m, deepest at VES 15 and away from viable aquifer units because the area is shallowest at VES 7. vulnerable to pollution if there is leakage of buried tank, sewage channels or infiltration of leachate from CONCLUSION. decomposing waste disposal in the area as a result of Subsurface Stratigraphic mapping using the their shallow depth to the aquifferous zone ranging d.c electrical resistivity method was carried out from 1.06 to 4.14 m. It is also deduced that the area around Shika, Kaduna State, Nigeria, three to four can support low to massive engineering structures as geologic strata are delineated at the subsurface a result of the thin clayey nature in the study area composed of top soil, weathered basement, partly underlain by basement rocks at shallow depth. This weathered or fractured basement and fresh basement. underlying rock serve as pillar supports to the Based on the qualitative interpretation of the VES building, hence, the structural foundation requires data, it is deduced that VES Stations 2, 3, 5, 9, 10, 11, little or no pilling. Based on the resistivity values of 13, 14, 15 and 17 are viable postions for siting the different geoelectric layers, it has been concluded boreholes with appreciable thickness of weathered that the various geologic units, up to a depth of about and fractured basement (aquiferrous zone) ranging 25 - 30m are fairly competent and can support large from 12.7 to 33.04 m. These geologic strata are civil engineering structures. characterized by structural features like fractures, Table 1: The results of the interpreted VES curves 2.85 87 TPCT15 VES 6.86 Thickness 197 Layer resistivity WB Remarks A Curve types Numb of layers 3 Stations - (m) (Ωm) 1.77 85 TP 1 3.33 319 WB A 3 - 2115 FB 2.01 80 TP2 20.1 418 WB KH 4 12.9 318 PWB - 1396 FB 1.35 245 TP 3 5.05 290 WB KH 4 26.3 510 PWB - 1215 FB 1.24 145 TP4 2.04 100 WB H 3 - 1930 FB 2.22 214 TB5 4.95 493 WB KH 4 18.04 408 PWB - 2020 FB 2.57 135 TP6 7.6 523 PWB A 3 - 1520 FB 1.55 60 TP7 1.77 234 WB A 3 - 1230 FB 1.51 150 TP8 1.97 224 WB A 3 - 1280 FB 1.29 256 TP9 12.7 391 WB A 3 - 1450 FB 1156 | P a g e
  4. 4. 1 Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1154-1161Table 2: The results of the interpreted VES curves VES Thickness Layer resistivity Remarks Curve types Numb of layers Stations (m) (Ωm) 1.43 373 TP s10 6.8 221 WB KH 4 17 473 PWB - 1251 FB 1.65 370 TB 11 15.7 70 WB KH 4 20.4 503 PWB - 1161 FB 1.06 276 TP 12 12.84. 351 WB KH 4 11 522 PWB - 1197 FB 2.02 304 TP 13 5.51 593 WB KH 4 17.4 834 PWB - 2019 FB 2.64 257 TB 14 32.36 144 WB H 3 - 1410 FB 2.96 256 TB 15 33.04 391 WB A 3 - 1450 FB 1.87 272 TP 16 17.13 228 WB H 3 - 1362 FB 4.14 367 TP 17 3.85 298 WB H 3 - 1765 FB 1.54 353 TP 18 6.58 708 WB A 3 - 3115 FB 1157 | P a g e
  5. 5. 1 Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1154-1161Apparent resistivity (Ωm) Where, N is the number of layers, ρ is the apperent resistivity, h is the thickness and d is the depth to interface of each layer. Electrode spacing (m) (a) VES Station 11 (TYPE KH CURVE) Apparent resistivity (Ωm) Where, N is the number of layers, ρ is the apperent resistivity, h is the thickness and d is the depth to interface of each layer. Electrode spacing (m) (b) VES Station 6 (TYPE A CURVE)Apparent resistivity (Ωm) Where, N is the layer number, ρ is the apperent resistivity in ohm-metre, h is the layer thickness and d is the depth to interface of each layer Electrode spacing (m) (c) VES Station 9 (TYPE A CURVE) FIG. 2: Typical curve types and models obtained from the study area. 1158 | P a g e
  6. 6. 1 Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1154-1161 VESVES 1 1C VES VES 2 2C VESVES 3 3C VES VES 4 4C VES VES 5 5C VES VES6C 6 VES VES7C7 VESVES 8 8C VES VES9C9 A 55 𝜴𝒎 Ai 245 𝜴𝒎 38 𝜴𝒎 38 𝜴𝒎 39 𝜴𝒎 452 𝜴𝒎 245 𝜴𝒎 73 𝜴𝒎 84 𝜴𝒎 114 𝜴𝒎 133 𝜴𝒎 190 𝜴𝒎 520 𝜴𝒎 211 𝜴𝒎 219 𝜴𝒎 196 𝜴𝒎 120 𝜴𝒎 218 𝜴𝒎 1233 𝜴𝒎 1287 𝜴𝒎 10 1931 𝜴𝒎 408 𝜴𝒎 1520 𝜴𝒎 526 𝜴𝒎 1329 𝜴𝒎 219 𝜴𝒎DEPTH (m) 20 396 𝜴𝒎 1520 𝜴𝒎 30 1215 𝜴𝒎 1396 𝜴𝒎 40 Clayey (Top soil) Sandey Lateritic hard pan (Top soil) Weathered layer Partly weathered/fractured layer Fresh basement i FIG. 3: Geoelectric section along profiles A-A 1159 | P a g e
  7. 7. 1 Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1154-1161 VES 12 VES 13 VES 15 VES 16 VES 17 VES 10 VES 11 VES 14 VES 18 B 276 𝜴𝒎 Bi 373 𝜴𝒎 370 𝜴𝒎 304 𝜴𝒎 365 𝜴𝒎 272 𝜴𝒎 353 𝜴𝒎 257 𝜴𝒎 367 𝜴𝒎 𝟐𝟐𝟏 𝜴𝒎 59 𝜴𝒎 708𝛺𝑚 298 𝜴𝒎 351 𝜴𝒎 228 𝜴𝒎 77 𝜴𝒎 10 3115 𝜴𝒎 1765 𝜴𝒎 144 𝜴𝒎 391 𝜴𝒎 473 𝜴𝒎DEPTH (m) 20 834 𝜴𝒎 522 𝜴𝒎 1362 𝜴𝒎 503 𝜴𝒎 30 1251 𝜴𝒎 1410 𝜴𝒎 1450 𝜴𝒎 40 Lateritic hard pan (Top soil) Weathered layer Partly weathered/fractured layer Fresh basement er FIG. 4: Geoelectric section along profiles B-Bi AND MN AND IJ 1160 | P a g e
  8. 8. 1 Fadele, Jatau, Patrick./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.1154-1161REFERENCES 1 DANLADI, G.G. 1985. “Appraisal of Geography,Occasional Paper No. 4, Hydrological Investigation in Shallow Ahmadu Bello University, Zaria, P. 223 – Basement Area of Zaria”. npublished 238. M.Sc. Thesis, Department of Geology, 5. McCURRY, P. 1970. “The Geology of Ahmadu Bello University, Zaria. Zaria Sheet 21”. Unpublished M.Sc. 2. FAROUQ, A.U. 2001. “Geoelectric Thesis, Department of Geology, Ahmadu Investigation of the groundwater potential Bello University, Zaria. in the Institute for Agricultural Research 6. OYAWOYE, P. O. 1964. “Geology of farm”. Unpublished M.Sc. Thesis, Nigerian Basement Complex”. Journal of Department of Physics, Ahmadu Bello Mining and Geology, Vol.1, P. 110-121 7. University, Zaria. SAMINU, O. 1999. “Geophysical 3. HAROLD, E.D. 1970. “Arid Lands in Investigation of Federal College of Transition”. The Hornshafer Company Education, Zaria”. Unpublished M.Sc. Division of G.D.W. King Printing Co., Thesis, Department of Physics, Ahmadu U.S.A. Bello University, Zaria. 4. KLINKENBERA, K. 1970. “Soil of Zaria 8. WRIGHT, J. B. and McCURRY, P. Area, In Zaria and its Region” (ed. M. J. (1970). “The geology of Nigeria Sheet 102 Mortimore), Department of SW, Zaria and its regions. Edited by M. J. Mortimore. Department of Geography, Occasional paper, No. 4, Ahmadu Bello University, Zaria. 1161 | P a g e

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