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Physics Journal
Vol. 1, No. 2, 2015, pp. 97-104
http://www.aiscience.org/journal/pj
* Corresponding author
E-mail address: [email protected] (A. T. Olugbenga)
Determination of Subsurface Delineation Using Electrical Resistivity Sounding in Zuba and Environs of Gwagwalada Area Council, Abuja, North Central, Nigeria
Adeeko Tajudeen Olugbenga1, *, Ojo Emmanuel Osiewundo2
1Department of Physics, Faculty of Science, University of Abuja, Abuja, Nigeria
2Science Infrastructure Department, National Agency for Science and Engineering Infrastructure, Abuja, Nigeria
Abstract
The electrical resistivity investigation of Zuba and Tungamaje area, of Gwagwalada Area Council, Abuja, was carried out with
a view to providing geology and geophysical information on the different sub-surface layers, depth, thickness, and distribution
of the fractured basement as potential sources of groundwater. The basement rocks consist of a migmatite-gneisses, granite
gneiss, and granite. The granite occurs in several locations of the study area. Twelve vertical electrical sounding stations were
established utilizing the Schlumberger electrode configuration. The electrical resistivity data obtained where interpreted using
IPI2win software. The results obtained from the analysis of the geophysical data showed that the study area is underlined by
three geo-electrical layers. These layers are the topsoil, weathered layers, and fractured basement. The top soil layer of
thickness and resistivity values ranging from 1.31-2.16m and 236-990 ohms meters, weathered layer ranging from 1.22-5.19m
and 33.8-213 ohms meters and the fractured basement ranging from infinity in thickness and 397-966 ohms meters. Also, the
study area lacks sufficient fractures and the thickness of the overburden was also thin for groundwater exploration activities.
Keywords
Gwagwalada, Granite Gneiss, lithology, potential, Schlumberger, Tungamaje, Zuba
Received: July 3, 2015 / Accepted: August 9, 2015 / Published online: August 19, 2015
@ 2015 The Authors. Published by American Institute of Science. This Open Access article is under the CC BY-NC license.
http://creativecommons.org/licenses/by-nc/4.0/
1. Introduction
Groundwater occurrence is greatly influenced by the geology,
topography and climatic factors that prevailed in a given
area. By the same fact, the hydro-geologic condition of
Gwagwalada area council is mainly controlled by the
geology and geological structure. Geological structures
(faults, fractures and lithologic contacts) play a great role in
the movement occurrence of groundwater in the study area,
the area is characterized by rocks like granite, pegmatite,
shiest and gneiss which are Precambrian in nature
groundwater occurs in the basement complex in the
weathered mantle or in the joint and fracture systems in the
unweathered rocks. The area under study belongs to the
Precambrian era. It is underlain by the Nigerian basement
complex rock of the Precambrian age. Weathering and other
denudational activities have made parts of the under laying
rock mass to be slightly thicker in some areas than others.
The area has a fairly plain topography with sparsely
distributed medium size hills and highlands that may have
been formed by outcropping basement rocks. The basement
rocks consist of a migmatite-gneisses, granite gneiss, and
granite. The migmatite-gneiss is the most wide spread rock
unit. The granite occurs in several locations. Detailed reports
Physics Journal Vol. 1, No. 2, 2015, pp. 97-104 98
of the lithological description, age, history, structure and
geochemistry of the Basement Complex of Nigeria are given
in Oyawoye, 1972; Black et al., 1979; Rahaman, 1988; Caby,
1989, and Dada, 2008. In Fig. 1 the blue arrow indicates the
location of Abuja on the geologic map of Nigeria. In the
study area, all the three major rock categories mentioned
above are well represented in Fig. 2. The rocks are generally
weathered into reddish micaceous sandy clay to clay
materials, capped by laterite (Obaje, 2009).
The choice of a particular method is governed by the nature
of the terrain and cost considerations [Emenike, 2001].
Fig. 1. Geological map of Nigeria, showing the position of Abuja (blue arrow) in the basement complex of north central Nigeria (modified from Obaje, 2009).
2. Geology of Study Area
The study area is zuba and Tungamaje in Gwagwalada Area
Council, is part of the basement complex of Nigeria
considered by various workers to be Precambrian to lower
Paleozoic in age (Oyawoye, 1970 and Rahman, 1976). Zuba
is located in the North Central part of Nigeria. It is situated
along Kaduna–Lokoja road, it is located at an elevation of
432 meters above sea level and its population amounts to
536,068 (cencus,2006). Its coordinator are latitude 90 05
1 47
11
N and longitudes 70 12
1 46
11 E. The Abuja Guide, a National
Space Research and Development Agency Atlas of 2002,
Abuja is located between latitudes 80 10
1 and 9
0 45
1 North
and longitudes 60 30
1 and 7
0 45
1 East.
The area of study forms part of the Basement Complex of
north central Nigeria; with lithologic units falling under three
main categories, which include (1) Undifferentiated
migmatite complex of Proterozoic to Archaean origin, (2)
Metavolcano-Sedimentary rocks of Late Proterozoic age and
(3) Older Granite Complex of Late Precambrian - Lower
99 Adeeko Tajudeen Olugbenga and Ojo Emmanuel Osiewundo: Determination of Subsurface Delineation Using Electrical
Resistivity Sounding in Zuba and Environs of Gwagwalada Area Council, Abuja, North Central, Nigeria
Palaeozoic age, also known as Pan-African Granites Ajibade
et al., 1987. All these rocks have been affected and deformed
by the Pan-African thermotectonic event. The rocks of the
area are generally quartz-rich acidic types which account for
the generally sandy nature of the soil. There is however, one
major advantage about the type of rocks and soils found in
the area because of the availability of construction materials
in the form of building stones, quartz and pistolitic gravel,
building sands and earth for use as foundation materials, as
well as pottery raw materials. Figure 3 shows the geological
map of Abuja showing Gwagwalada area council. The
amount of rainfall in the area is moderate between the
months of April and October and the dry season which begins
from October–November and last until March-April,
although there could be some scanty flashes of rain during
this period. However, within these seasons is a brief
harmattan season that is occasioned by the north east trade
wind and the attendant dust haze, increased cold and dryness.
Weather conditions in the area are influenced by its location
within the Niger–Benue trough on the windward side of the
Jos Plateau and at the climate transition zone between the
essentially ‘humid’ south and ‘sub-humid’ north of the
country. The high temperatures and the relative humidity in
the Niger-Benue trough give the area a heating effect.
Fig. 2. Geological map of the study area and showing positions of VES points.
Physics Journal Vol. 1, No. 2, 2015, pp. 97-104 100
Fig. 3. Geological Map of Abuja (source: Geology Unit of Bwari Area Council August, 2014).
3. Material and Method
The electrical resistivity method utilized the Vertical
Electrical Sounding (VES) is used to measure vertical
variations in electrical properties beneath the earth surface
involving the schlumberger array, ABEM Terrameter SAS
300C was used to acquire resistivity data. Field equipment,
include: Terrameter, current and potential electrodes, long
conductors with crocodile clips, hammers, field survey tapes
and mobile phones for communication. The Resistance
measurements are made at each expansion and multiplied by
the respective geometric factor (K) to give the resistivity. A
total of twelve VES soundings were carried out along the
study area. The electrode separation (AB/2) varied from 1.5
to 150 m was used with the aim of probing a depth of at least
1/3 of AB. The VES station were marked, two current
electrodes (C1 and C2) of equal distances on the opposite
side of the VES station were measured and hammered into
the ground. Similarly, two other electrodes (P1 and P2) of
equal distances at VES point between the current electrodes
were measured. The obtained field dates were subjected to
analysis and interpretation by computer iterations using
Ipi2Win Software.
4. Result and Discussion
A total number of twelve (12) VES were carried out, six in
each of the two locations. The results of the interpretation
were used to determine the expected subsurface geologic and
hydro-geologic features of the water bearing rocks. The
interpreted result of the vertical electrical sounding data
revealed the different geo-electric layers in terms of their
resistivities and depths in the study area. The software used
in the processing of the raw data works in such a way that it
merges neighbouring layers of slightly different resistivities
in order to minimize the layers detected. The sounding curves
show three layer earth models. The three layer curve
Characterized by H curve types covered 100% of the study
area. The rocks within this basement complex are grouped
into three categories; these are the older granites, gneiss and
mignetite; the older metasediments; and the younger
metasediments. According to Ajibade and Wright (1980), the
rocks of the basement complex are believed to have evolved
in at least four orogenic events namely: the pan African
(600±150My), The Kibaran (1100±200My), The Eburnian
(2000±200My) and the Liberian (2800±200My). The
migmatite–gneiss complex dominates the basement complex
in the study area consisting of fairly uniform biotite and
biotite–hornblende–gneisses with locally intercalated bands
of amphibolites and quartzite (Geological Survey of Nigeria,
1986).
The result of the geophysical investigation revealed three
subsurface geo-electrical layers in all the VES stations. The
observed geo-electric sections include the top soil layer,
101 Adeeko Tajudeen Olugbenga and Ojo Emmanuel Osiewundo: Determination of Subsurface Delineation Using Electrical
Resistivity Sounding in Zuba and Environs of Gwagwalada Area Council, Abuja, North Central, Nigeria
weathered layer, and fractured basement. The top layer
resistivity values ranges from 236 to 990 ohm-m, with mean
resistivity of 528.25 ohm-m. Its highest value was observed
at VES 12 and the lowest at VES 01 (as seen in fig. 4). The
top layer thicknesses range from 1.31 to 2.16m, with mean
thickness of 1.7892m. It highest value was observed at VES
07 and the lowest at VES 06. The second layer constitutes the
weather layer and its resistivity values range from 33.8 to
213Ωm with mean resistivity of 67.33Ωm (as seen in fig. 5).
The highest value was observed at VES 06 and the lowest at
VES 02. Its thicknesses range from 1.22 to 5.19m, with mean
thickness of 2.992m. The highest thickness was observed at
VES 06 and the lowest at VES 02 (as seen in fig. 7 and fig.
8). The third layer which constitutes the fractured basement
which has resistivity values that range from 297 to 966 ohm-
m, with mean resistivity of 539.42 ohm-m. Its highest value
was observed at VES 8 and the lowest at VES 1(as seen in
fig. 6).
The lithology was used as a preliminary basis for rock type
identification, in the (FCT) (Edetand Okereke, 1985),
malomo et al, 1982/83, omeje et al, 2013 and the lithology of
the study area agree with the earlier study mention.
Table 1. Simulated Result of Resistivity Data from the Study Area.
VES Layers ρ ( Ω-m) Thickness(m) Depth(m) Probable Geological Section Curve types Coordinates
01
1 236 1.65 1.65 Top soil
H
9.0961113N
2 42.3 1.56 3.22 Weather layer
3 397 - Fractured basement 7.1958333E
02
1 249 1.85 1.85 Topsoil
H
9.094444N
2 33.8 1.22 3.07 Weather layer
3 420 - Fractured basement 7.211666E
03
1 261 1.87 1.87 Topsoil
H
9.095833N
2 35.7 1.44 3.31 Weather layer
3 400 - - Fractured basement 7.096111E
04
1 308 1.63 1.63 Topsoil
H
9.0963889N
2 39.2 1.32 2.95 Weather layer
3 477 - - Fractured basement 7.212778E
05
1 322 1.93 1.93 Topsoil
H
9.09555N
2 51 1.64 3.56 Weather layer
3 429 - - Fractured basement 7.211944E
06
1 955 1.31 1.31 Topsoil
H
9.095277N
2 213 5.19 6.49 Weather layer
3 506 - - Fractured basement 7.211666E
07
1 612 2.16 2.16 Topsoil
H
9.095833N
2 76.9 2.9 5.06 Weather layer
3 500 - - Fractured basement 7.2125E
08
1 405 1.65 1.65 Topsoil
H
9.0963886N
2 69.2 2.27 3.92 Weather layer
3 966 - - Fractured basement 7.212778E
09
1 747 1.76 1.76 Topsoil
H
9.0969441N
2 97.6 3.35 5.11 Weather layer
3 627 - - Fractured basement 7.213889E
10
1 714 2.15 2.15 Topsoil
H
9.096111N
2 47.9 1.6 3.75 Weather layer
3 597 - - Fractured basement 7.2125E
11
1 540 1.86 1.86 Topsoil
H
9.0966663N
2 45.7 1.59 3.45 Weather layer
3 519 - - Fractured basement 7.21306E
12
1 990 1.65 1.92 Topsoil
H
9.0963886N
2 55.7 1.92 3.57 Weather layer
3 635 - - Fractured basement 7.212778E
Physics Journal Vol. 1, No. 2, 2015, pp. 97-104 102
Fig. 4. Topsoil Layer Iso-Resistivity.
Fig. 5. Weather Layer Resistivity.
Fig. 6. Fracture Basement.
Fig. 7. Weather Thickness.
9.094
LATITUDE
7.1
7.11
7.12
7.13
7.14
7.15
7.16
7.17
7.18
7.19
7.2
7.21
LONGITU
DE
200
240
280
320
360
400
440
480
520
560
600
640
680
720
760
800
9.094
LATITUDE
7.1
7.11
7.12
7.13
7.14
7.15
7.16
7.17
7.18
7.19
7.2
7.21
LONGIT
UDE
35
45
55
65
75
85
95
105
115
125
135
145
155
165
175
9.094
LATITUDE
7.1
7.11
7.12
7.13
7.14
7.15
7.16
7.17
7.18
7.19
7.2
7.21
LONGIT
UDE
380
400
420
440
460
480
500
520
540
560
580
600
620
640
660
680
700
720
740
760
780
800
820
9.094
LATITUE
7.1
7.11
7.12
7.13
7.14
7.15
7.16
7.17
7.18
7.19
7.2
7.21
LONG
ITUDE
1.3
1.5
1.7
1.9
2.1
2.3
2.5
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
103 Adeeko Tajudeen Olugbenga and Ojo Emmanuel Osiewundo: Determination of Subsurface Delineation Using Electrical
Resistivity Sounding in Zuba and Environs of Gwagwalada Area Council, Abuja, North Central, Nigeria
Fig. 8. 3D of Weather Thickness.
5. Conclusion
This study has been able to shown the importance of
resistivity method in determine the lithology of an area. The
geophysical investigation carried out delineates the presence
of three subsurface layers which comprised the top soil
which is composed of sandy clay or clayey sand, weathered
layer which due to the low resistivity of the VES point for
this layer, there is indication of possible clay materials within
the weathered layer, and fractured basement rock cannot
sustain boreholes. The basement rocks consist of a
migmatite-gneisses, granite gneiss, and granite. The
migmatite-gneiss is the most wide spread rock unit. In zuba
and tungamaje, the rock compositions are made up of
granites; granite gneiss gave relatively higher yields in the
faulted zones or apparently fractured which could be the
evidence of volcanic activity marked by the occurrence of
flat toped lateritised basalt. There should be a thorough
investigation of rock to determine its characters and
properties within the area.
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