sems conference proceedings
Transcript of sems conference proceedings
1
EDITORS
Dr. S.A. Opeloye
Dr. A.Y.B. Anifowose
Dr. G. M. Olayanju
Dr. A. Oluleye
Dr F. O. Akinluyi
Mr. R. B. Adesina
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CONTRIBUTORS
Page
Abe S.J, Akinlalu A.A, Fowowe C. and Ako B.D 3
Abubakar B. and Ogunjobi, K.O. 6
Adelabu, I.O. and Opeloye, S.A. 10
Adegbuyi, O., Akinyemi, O.M. and Ogunyele, A. C. 14
Adeseko, A.A and Bolarinwa, A.T. 19
Adesina R.B. and Aladejana O.O. 24
Adewoye, O. and Amigun, J.O. 28
Adiat, K.A.N., Adegoroye, A.R. and Akinlalu A. 33
Adisa, A.L. and Adekoya, J.A. 37
Aluko, A.B. and Anifowose, A.Y.B. 41
Anifowose, A.Y.B. and Aladejana, O.O. 46
Babatola, E.B., Adeyemi, E.O. and Esan, A.L. 52
Bala, B., Lawal, K.M. and Ahmed, A.L. 57
Bamisaiye, O.A..Eriksson, P.G., van Rooy, J.L., Brynard, H.M. and Foya, S. 61
Dada, B.M. and Okogbue, E.C. 66
Daramola S.O. and Ilesanmi, B.I. 71
Adediji, A., Iyamu, F. and Fakpor, A. M. 75
Ganiyu, S.A. and Adetunji, O.S. 81
N'Datchoh, E. T, Konaré, A. and Ogunjobi, K. O. 85
Ojo, B. T. 89
Okonkwo, C.T. and Adeoti, B. 94
Ola, P. S. and Agbaje, A. O. 98
Olaogbebikan, J.E. 102
Olayanju, G.M. and Ojo, A.O. 105
Oluwadare, O.A. and Olowokere, M.T. 110
Olisa B. A., Ako B.D. and Ojo, J.S. 113
Olowolafe, T. S. and Akintorinwa, O. J. 117
Osumeje, J.O. and Lawal, K.M. 120
Owoseni, J.O. and Malomo, S. 125
Wahab, S.A., Akinyokun O. C., Ojo J. S. and Enikanselu P.A. 130
Abiola, O. and Adeduyite, E.T. 135
Adeyemo, I. A., Mogaji, K.A., Olowolafe, T. S. and Fola-Abe, A. O. 139
Adeyemo I.A, Omosuyi G.O. and Adelusi, A.O. 146
Opeloye, S.A. 152
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APPLICATION OF S-LINE AND DAR-ZARROUK PARAMETERS IN DETERMINING DEPTH
TO BEDROCK FROM ELECTRICAL RESISTIVITY DATA
Abe S.J, Akinlalu A.A, Fowowe C., Ako B.D
Department of Applied Geophysics
Federal University of Technology Akure, Ondo State, Nigeria
ABSTRACT
Vertical electrical sounding technique in Electrical resistivity method of Geophysical prospecting over
time has been used in delineating subsurface layers and to determine the depth to bedrock among others.
Its efficiency and accuracy depends on the availability of space to obtain the maximum electrode spread
required to achieve a set objective. The bottleneck of space especially in built up areas can be overcome
by the use of the S-line method to determine depth to the top of the basement. Six VES points were
sounded and nine (9) curves were generated. VES 1 – VES 3, were used as control using the normal
spread length to the top of the basement, while VES1 - VES3 were also sounded with short spread on
which the S-line method was applied to obtain the depth to the bedrock. This method was also applied to
VES 3 - VES 6. The plot of the data from VES1 – VES 3 gave three (3) layer H-type curve type and the
layer parameters were thus determined from partial curve matching of the full spread of VES 1 – VES 3.
The abridged (short spread), VES 1 – VES 3 were also plotted, giving a two layer curve, and a 45° line
(known as S-line) was drawn to the curve. From the partial curve matching of the two layer curve
obtained and application of the Longitudinal Conductance equation of the Dar-Zarrouk parameters, the
layer parameters were determined. The layer parameters obtained from the plots of VES 1 – VES 3, with
those of the two layer curve of VES 1 – VES 3 in which the S-line method was applied were relatively
close, hence the functionality of the S-line method was thus affirmed. The S-line method was in turn
applied on VES 4 – VES 6 which were four (4) layer curves (AK and HK’s) to determine their depth to
bedrock. It is therefore established from the study that the S-line method could be an effective method in
determining the depth to bedrock in situations in which investigation has not reached the bedrock.
Keywords: Dar-Zarrouk, S-line, Longitudinal Conductance.
INTRODUCTION
Resistivity measurements are associated with
varying depths depending on the separation of
the current and potential electrodes in the
survey, and can be interpreted in terms of a
lithologic and/or geohydrologic model of the
subsurface.
In Vertical Electrical Sounding (VES) of the
electrical resistivity method, the increasing
electrode separation,(a; AB/2) also increases the
depth of penetration. However in scenarios in
which during data acquisition there is not
enough space to increase the electrode spacing
as appropriate or there is obstruction which
inhibits investigation to the desired depth, and in
turn prohibits the determination of the thickness
of the layer above the bedrock, the application of
S-line method becomes useful in mathematically
calculating the thickness of such layer using
Dar-Zarrouk (D-Z) Parameters together with the
45° (S) Line. This is so when maximum
electrode spacing could not be attained or to
justify thickness determined from partial curve
matching.
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Figure 1: Plot of VES 1, full spread Figure 2: Plot for the short spread of VES 1, with the
45° line (S-line)
Table 1: The calculated parameters for the control of VES 1
S/N VES AB/2spread
(m)
CURVE
TYPE
TRUE RESISTIVITES (ρ) LAYER THICKNESS (h)
ρ1 (Ωm) ρ2 (Ωm) ρ3 (Ωm) h1 (m) h2(m)
1 1 25 H 255 204 563 0.8 1.44
Where S = 0.05S, h1 = 0.8m, ρ1 =200 Ωm, ρ2 = 250Ωm.
Inputting the parameters into equation (1.2) h2 = 1.36m.
Table 2 : Comparing Results for Layer Thickness as Derived from partial curve matching and through s-line
VES 1
Full VES 1 Abridged VES 1
h1 0.8 0.8
h2 1.44 1.36
Z = h1+h2 2.24 2.16
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METHODOLOGY
Dar-Zarrouk Parameters Estimation
Dar-Zarrouk (D-Z) parameters termed by
Maillet (1947) plays an important role in
resistivity soundings. D-Z parameters are used
for computing the distribution of surface
potential and the section consists of ‘n’ fine
layers with thickness h1,h2,…hn and resistivity
ρ1, ρ2, … , ρn for a block of unit square area
and thickness
H = ∑ ℎ𝑖𝑁𝑖=1 1.1
Longitudinal unit conductance,
S = ℎ1
𝜌1+
ℎ2
𝜌2+
ℎ3
𝜌3+ ⋯ +
ℎ𝑛
𝜌𝑛= ∑
ℎ𝑖
𝜌𝑖
𝑁𝑛𝐼=1 1.2
Transverse unit resistance,
T = 𝜌1ℎ1 + 𝜌2ℎ2 + 𝜌3ℎ3 + ⋯ + 𝜌𝑛ℎ𝑛 = ∑ 𝜌𝑖ℎ𝑖𝑛𝑖=1 1.3
Equation 1.2 forms the basis of the S-rule technique of interpretation which is used in this work.
DISCUSSION OF RESULTS
Full Plots of VES 1
The manual plot of the apparent resistivity
against AB/2 on a bi-log graph for full spread of
VES 1, is shown in figure 1 . While the manual
plot for the abridge spread of VES 1, with the
45° line (S-line) is shown in figure 2.
CONCLUSION
Conclusively, the S-line technique has been used
to determine the depth to bedrock in VES 1 with
electrode spacing (AB/2) of short spread 12m
and the results obtained show a difference of
about (± 0.6𝑚) from that of the full spread 25m
of the same VES 1. Therefore, the S-line is
adjudged to be relatively effective in
determining depth to bedrock in situations where
the spread is short or the maximum AB/2 value
used is not enough to map top of the bedrock
REFERENCE
Maillet. R. (1947). The fundamental equation of
Electrical prospecting. Geophysics., 12, pp.
529-556.
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ABSTRACT
This study assesses climatology in wind speed in the North-west geo-political region of Nigeria,
performance of different wind turbines and their cost of production per kilowatt-hour. It is aim at
assessing the wind energy and wind power potential in selected stations over the Northern region of
Nigeria using thirty years monthly mean wind speed data (1982-2011) and five years daily mean wind
speed data (2007-2011) obtained from the record archive of the Nigerian Meteorological Agency
(NIMET) measured at 10 m height and subjected to 2-parameter Weibull analysis. The stations under
considerations are Katsina, Gusau, Sokoto, Kano and Zaria. Annually, the mean power density
ranges from 275.72 W/M2 in Gusau to 5705.63 W/M2 in Katsina. A technical electricity generation
assessments using three commercial wind turbines GE 1.5 xle, AV 928 and V90 were carried out. The
result indicates that GE 1.5 xle turbine produce at the highest Capacity Factor (%) with values
ranging from 6.18% in Gusau to 99.82% in Kano. The average wind power output from AV 928
ranges from 104.56 KW in Sokoto to 2499.18 KW in Kano and closely followed by GE 1. xle, with
power output ranging from 92.65 KW in Gusau to 1499.61 KW in Kano. These results indicate that
wind speed at the site may be economically viable for wind power generation at and above the height
of 10m.
INTRODUCTION
Energy is one of the crucial inputs for socio-
economic development. Energy is not only
prime agent for the generation of wealth but a
significant factor in economic development
and the driving force for industrialisation of
any society (Bala et al., 2013). One way to
increase energy generation in Nigeria is to
develop the available renewable energy
resources of which wind energy technology is
a major source. Therefore a careful wind
resource assessment of this region will be a
major leap in the move towards developing
sustainable energy and power for the nation
(Fagbenle et al., 2010).
METHODOLOGY
Wind data acquisition
Daily and monthly wind speed data were
collected from the records archive of the
Nigerian Meteorological Agency (NIMET).
The monthly wind speed for a period of thirty
years (1981-2011), also, the daily wind speed
for a period of five years (2007-2011)
covering five selected stations in the Northern
Nigeria. The stations considered for Sokoto,
Gusau, Katsina, Kano and Zaria. The data
obtained was recorded continuously using cup
counter anemometer at a height of ten meters
(10m).
RESULTS AND DISCUSSION
The analysis of the 30-years annual average
wind speed at 10 m height over Zaria, Sokoto,
Katsina, Kano and Gusau is shown in Figure 1.
The results reveals that the minimum and
maximum wind speed for the periods lie
between 1.8 to 6.3 m/s in Katsina, 4.6 m/s to
6.1 m/s in Kano, 3.6 m/s to 5.6 m/s in Sokoto,
2.3 m/s to 4.8 m/s in Gusau and 2.8 m/s to 4.9
m/s in Zaria, thus showing that Kano has the
highest range and Gusau having the lowest.
The annual mean wind speed over the stations
is 4.2 m/s in Katsina, 4.4 m/s in Sokoto, 3.6
m/s in Gusau, 3.6 m/s in Zaria and 5.2 m/s in
Kano while the standard deviation was 1.36 in
Katsina, 0.56 in Sokoto, 0.56 in Gusau, 0.54 in
Zaria and 0.37 in Kano.
WIND ENERGY POTENTIAL AND WIND POWER ASSESSMENTS IN NORTH-WEST
GEO-POLITICAL REGION OF NIGERIA
B. Abubakar, K.O. Ogunjobi
Department of Meteorology and Climate Science,
Federal University of Technology Akure, Ondo State, Nigeria
2 WASCAL, Federal University of Technology Akure, Ondo state, Nigeria.
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Figure 1: Plot of Annual average wind speeds (at 10 m height) over Zaria, Sokoto, Katsina, Kano and
Gusau, for the entire period (1982-2012).
The monthly mean power density as shown in Figure 2 ranges from about 10.46 W/m2 to 70.80 W/m2,
13.74 W/m2 to 60.71 W/m2, 29.1 W/m2 to 90.2 W/m2, 36.86 W/m2 to 157.13 W/m2 and 38.33 W/m2 to
167.20 W/m2 for Zaria, Gusau, Sokoto, Katsina and Kano respectively.
Figure 2: Plot of monthly variation of wind power density over the five stations using the 30-years
daily wind speed data.
To determine the likely output power and
average power which a wind energy
conversion system installed at the station could
possibly produce involves employing three
turbine machine models, GE 1.5 xle, AV 928
and V90. In terms of the production capacity,
the producible wind power (KW) at the sites
are presented in Figures 3. Figure 3
demonstrate that, although AV 928 model was
second best in terms of capacity factor of
average production over the rated power (PeR),
its production capacity is the best. This is due
to its power rating (2500KW). This ranges
from 109.10 KW (Zaria) to 2500KW (Kano).
This is followed by GE 1.5 xle with output
power ranging from 57.60 KW (Zaria) to
1500KW (Kano) and finally V90, with power
output ranging from 23.14 KW (Katsina) to
3000KW (Kano).
The average power output (Pe, ave) from the
three wind turbines reveal that AV 928
produces more wind power on the sites than
the other turbines. This ranges from 104.56
(Sokoto) to 2499.18 KW (Kano). This is
followed by GE 1. xle, with power output
ranging from 92.65 (Gusau) to 1499.61 KW
(Kano) and finally, 56.39 (Katsina) to 2595.93
KW (Kano).
CONCLUSION
An assessment of wind energy and wind
power generation at five selected stations in
the Northern region of Nigeria was carried out.
It was discovered that:
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Figure 3. Plot of electrical power output of (a) GE 1.5xle; (b) AV928; and (c) V90 wind turbine over
the five stations using the five years daily mean wind speed data.
1. The 30-years monthly average wind
speed variation ranged in all the five
stations from 1.8 m/s to 6.4 m/s.
2. The cumulative probability distribution of
the wind speed in the five locations show
a similar trend. Up to 80% of the values
ranges between 4.83 m/s to 8.33 m/s, 8.42
m/s to 8.75 m/s, 6.50 m/s to 7.42 m/s,
10.75 m/s to 11.71 m/s and 6.33 m/s to
9.83 m/s in Katsina, Sokoto, Zaria, Kano
and Gusau. This indicates that wind
turbine system with cut- in wind speed of
3m/s is suitable for all the locations.
3. The estimated monthly mean wind power
density ranges from about 10.46 W/m2
(September) in Zaria to 167.20 W/m2
(January) in Kano. Annually, the mean
power density ranges from 275.72 W/m2
in Gusau to 5705.63 W/m2 in Katsina.
The periods of December to February
appear to have a good potential for wind
energy harvest while January have the
highest potential for wind energy harvest.
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REFERENCES
Adaramola, M. S., Oyewola, O. M, (2011):
Wind speed distribution and
characteristics in Nigeria. Journal of
engineering and applied sciences. Vol.
6, 82-86.
Ajayi, O. O., Fagbenle, R. O., Katende, J.,
Aasa, S. A., Okeniyi, J. O (2013):
wind profile characteristics and
turbine performance analysis in Kano,
north-western Nigeria. International
Journal of Eergy and Environmental
Engineering. 4, 1-27.
Al-Buhairi, M. H., Alhaydari, A (2012):
Monthly and seasonal investigation of
wind characteristics and assessment of
wind energy potential in Al-Mokha,
Yemen. Energy and power
engineering. 4, 125-131.
Argungu, G. M., Bala, E. J., Momoh, M.,
Musa, M (2011): statistical analysis of
wind speed data in Sokoto, Nigeria,
based on Weibull and Rayleigh
distribution functions. Nigerian
journal of renewable energy. Vol. 16,
No. 1 & 2. 94-106.
10
MICROFLORA RETRIEVED FROM THE OPOLO-5 WELL, NIGER DELTA AS
PALEOCLIMATE INDICATORS
I.O. Adelabu and S.A. Opeloye
Department of Applied Geology, Federal University of Technology, Akure
ABSTRACT
The ditch cutting samples (3125 – 8150ft) retrieved from the Opolo-5 well yielded a fairly rich
assemblage of pollen and spores but dinocysts species were sparse. Fifty –seven (57) species of pollen
and spores (seven spores, fifty pollen species) were identified, two (2) species of algae (Botryococcus
braunii and Pediastrum spp). Aside the indeterminate dinoflagellate cysts, about three species were
identified (Spiniferites spp., Polysphaeridium zoharyi, Lingulodinium machaerophorum and
Operculodinium centrocarpum); one acritarch (Leiosphaeridia sp.) was also recorded. The dominant
land – derived forms recorded include Zonocostites ramonae, Monoporites annulatus,
Sapotaceoidaepollenites spp, Retibrevitricolporites protrudens, Retitricolporites irregularis,
Verrucatosporites spp., Acrostichum aureum etc. The brackish water swamp species are
Psilatricolporites crassus and Pachydermites diederixi, while the fresh water swamp species recorded
include; Retitricolporites irregularis, Retibrevitricolporites protudens, Magnastriatites howardii,
Psilatricolporites operculatus etc. Pteridophyte spores (vascular plants) were ubiquitous as they were
recorded in almost all the samples. Based on the inferences from phytoecological groupings and the
occurrence of paleoenvironmentally significant species, particularly Zonocostites ramonae,
Monoporites annulatus, Botryococcus braunii and some palynological marker species like
Retistephanocolpites gracilis and Nympheaepollis clarus, four ‘Floral’ zones were established. They
are the ‘Floral’ zone P6, P7 (Early Pliocene) and the ‘Floral’ zone M1 and M2 dated Late Miocene.
These ‘Floral’ zones are linked to dry, humid and wet paleoclimatic depositional regimes. A
predominantly humid tropical climate with intermittent rainfall is inferred for the Late Miocene
period with an alternation of dry and wet climates (cyclicity of vegetation and continental climate)
later in the Early Pliocene.
INTRODUCTION
Variations in vegetation types are directly
related to fluctuations in climatic conditions
(Ojo and Akande 2004). Since climatic
changes do affect the vegetation, the
reconstruction of past vegetation will help us
understand the mechanisms of such changes
(Ivanor et al., 2007). Most reports of
palynological studies in Niger Delta exist as
confidential reports of the oil and gas
prospecting companies, only a few published
papers are available. This study was embarked
upon as identification of fossil morphophtyes,
their stratigraphic ranges and dispersions
within the sediments of Niger Delta provide a
unique useful tool in the reconstruction of
ancient deposition environments in terms
paleoclimate. The Opolo-5 well is situated
within the OML-95 of Chevron Nigeria
Limited in the Western part of Niger Delta.
MATERIALS AND METHOD OF STUDY
A total of 56 ditch cutting samples, with
sampling intervals ranging from 3125ft to
8150ft were used for palynological analysis.
25g by weight of each of the samples were
treated with HCl, HF, HNO3 (70%) and ZnBr2
for the purpose of removing carbonates, silica
and silicates, nitrates and for the removal of
mineral matter. The prepared palynological
slides were studied under the transmitted light
microscope.
Lithostratigraphy of the Well:
The Opolo – 5 well sequence is composed of
interbedded sands and shales with varying
sand – shale ratio. The sands are milky white
to buff, ranging from very fine-grained to
coarsely-grained, poorly to moderately well
sorted and sub-rounded to sub-angular. The
shales are grey to brownish grey, platy to
flaggy and sometimes blocky, they are
moderately hard.
Age Definitions of the Sediments: Late Miocene – Early Pliocene (8150 –
4070ft)
The palynological evidence that defines the
Late Miocene age is the Quantitative Base
11
Occurrence of Nympheaepollis clarus at
7070ft. The Pliocene age was attributed to the
presence of Miocene/Pliocene boundary
marker species of the Niger Delta,
Retistephanocolpites gracilis, with Base
Occurrence at 4730ft (Evamy et al., 1978).
Early Pliocene (4070 – 3125ft)
This age is supported palynologically by the
continued occurrence of Retistephanocolpites
gracilis.
RESULTS
Fifty –seven (57) species of pollen and spores
were identified, two (2) species of alga,
Botryococcus braunii and Pediastrum spp.,
four (4) dinoflagellate species and one
acritarch, Leiosphaeridia spp. (Fig.1, Plate1).
Microfloral Paleoecology The definition of the ecological groups were
based on the study of Germeraad et al. (1968),
Sowunmi (1986). The ecological groups
include fresh-water swamp forest species,
savanna species, brackish-water swamp forest
species etc.
Four ‘Floral’ zones were established (Table 1),
based on the inferences from phytoecological
groupings and the occurrence of
paleoenvironmentally significant species,
particularly Zonocostites ramonae,
Monoporites annulatus, Botryococcus braunii
and some palynological marker species like
Retistephanocolpites gracilis and
Nympheaepollis clarus. These ‘Floral’ zones
are linked to dry, humid and wet paleoclimatic
depositional regimes as suggested by Poumot
(1989). The four ‘Floral’ zones established
are; the ‘Floral’ zone P6(4370 – 3125ft), P7
(4820 – 4370ft) dated as Early Pliocene, the
‘Floral’ zone M1(6440 – 4820ft) and
M2(8150-6440ft) dated Late Miocene.
Palaeoclimate The section of well was divided into four
climatic units based on the ‘Floral’ zones.
Different climatic conditions were inferred for
the varying ‘Floral’ zones as discussed below:
UNIT 4 (8150-6440ft)
A wet condition could have been suggested for
this zone due to the regular occurrence of
mangrove pollen and abundance of fresh water
alga, Botryococcus braunii along with
Brackish water swamp species, Pachydermites
diederixi and Psilatricolporites crassus, which
actually peaked within this zone, but for the
remarkable increase in the Gramineae pollen
and the rare record of Cyperraceaepollis spp.,
which is a humid climate indicator (Dupont
and Agwu, 1991), the zone probably
experienced a tropical humid climate with
irregular rainfall during this time. Species of
Operculodinium centrocarpum and
Polysphaeridium zoharyi were not dominant,
but their rare occurrence suggests that, there
was a brief dry climate when sea levels
receded.
UNIT 3 (6440 – 4820ft)
This zone is probably a dry climate phase with
warm temperatures. Vermoere et al. (1999) in
a study in SW Turkey reported that high
percentages of Gramineae pollen types in
sediment points to drier local conditions.
There was a noticeable presence of savanna
species Echitricolporites spinosus, which
further confirms the prevalence of a dry
climate. Other important savanna species
occurring.
Table 1:Microflorals in Opolo 1 Well
12
Fig.1: Palynomorph Distribution Chart of
Opolo-5 Well
Plate 1: Photomicrographs of some of
the recovered palynomorphs
(Magnification x 800).
within this zone include Concentricytis spp.,
Proteacidites spp., Cyperaceaepollis spp.,
Corylus spp., Pteris spp., Chenophodipollis
spp., and more. The occurrence of small
quantities of mangrove pollen in this zone was
probably due to minor local short-lived
transgressions of the sea, thereby allowing
only very limited extension of mangrove
vegetation.
UNIT 2 (4820 – 4370ft)
The pollen record indicates an extension of
mangrove swamps and a rise in sea level. It
has been reported that high values of
Zonocostites ramonae characterize periods
with a high sea level. The preponderance of
ferns and occurrence of Cyperaceae in this
zone coupled with the presence fresh water
swamp forest species indicate a dominance of
wet and humid conditions that supported the
ample vegetation, with the ground covered by
pteridophyte in this zone. Contrarily, there was
a substantial rise in quantities (numerical) of
Gramineae pollen, Monoporites annulatus
coupled with the occurrence of a few savanna
13
species like Corylus spp. This can be attributed
to varying environmental conditions.
UNIT 1(4370 – 3125ft)
An initial rise in sea level with the mangrove
vegetation increasing in extent is suggested for
this zone. The fluctuations in percentage
occurrence of Zonocostites ramonae may
probably be a result of variations in the
intensity and extent of the tidal streams
thereby causing fluctuations in the extent of
mangrove forest. This rise and fall of the tides
may also bring about drier conditions resulting
in a reduction of forest vegetation and
subsequently promoting expansion of the
savanna (Olugbenga et al. 2011). This agrees
with the reports of Leroy and Dupont (1994)
which suggests cyclic fluctuations in the
vegetation and continental climatic condition
of NW Africa in the Pliocene, when river
discharge ceased, wind transport of pollen
grains prevailed over fluvial transport.
Although mangrove forest elements, like
Zonocostites ramonae, persisted through the
well, along with rainforest elements Canthium
spp., Retitricolporites irregularis etc., this
does not necessarily mean that a wet condition
persisted through the Period, but possibly a
result of the ceaselessness of rainforests and
minor forests in the Niger River catchment,
perhaps as a corridor of forests along the rivers
during the glacial periods, when enhanced
trade wind conditions led to dry conditions.
CONCLUSION
The retrieved forms show variation of
paleoclimate. A predominantly humid tropical
climate with intermittent rainfall is inferred for
the Late Miocene period with an alternation of
dry and wet climates in the Early Pliocene.
REFERENCES
Ajaegwu, N.E., Odoh, B.I., Akpononu, E.O.,
Obiadi, L.L., and Anakwuba E.K., 2012.
Late Miocene to Early Pliocene
Palynostratigraphy and Paleoenvironments
of Ane 1 Well. Journal of Mining and
Geology.Vol. 48(1), p.31-44.
Dupont, L.M., and Agwu, C.O.C., 1991.
Environmental control of pollen grain
distribution patterns in the Gulf of Guinea
and offshore NW-Africa. Geologische
Rundschau 80: 567-589.
Evamy, B.D., Herembourne, J., Kameling, P.,
Knaap, W.A., Molly, F.A., and Rowlands,
P.H., 1978: Hydrocarbon habitat of
Tertiary Niger-Delta. American
Association of Petroleum geologist.
Bulletin, vol.62, p.1-39.
Germeraad, J. H., Hopping, C.A. and Muller, J.
1968. Palynology of Tertiary sediments
from tropical areas: Review of
Palaeobotany and Palynology, v. 6/3-4, p.
189-348.
Ivanor, D.A., Ashraf, A.R., and Mosbrugger, V.,
2007. Late Oligocene and miocene climate
and vegetation in the eastern paratethys
area (Northeast Bulgaria), based on pollen
data. Palaeogeography Palaeoclimatology
and Palaeoecology, 255: 342-360.
Leroy, S.A.G., and Dupont, L., 1994. Development
of vegetation and continental aridity in
Northwestern Africa during the Late
Pliocene: The pollen record of ODP site
658. Paleogeography Paleoclimatology,
Paleoecology, 109: 295-316.
Ojo, O.J., and Akande, S.O., 2004. Palynological
and Paleoenvironmental Analyses of
Selected Samples From Dukul and Jessu
Formation, Yola Basin, Nigeria. Nigerian
Association of Petroleum Explorationists
Bulletin. V. 17 No. 1(November 2004) p.
69-76
Olugbenga, E.I., Kalyani, D., Kanak, S., and
Krishna, K.R., 2011. Palynological Studies
of Sediments from North Chioma-3 Well,
Niger Delta and its Palaeoenvironmental
Interpretations. American Journal of
Applied Sciences 8 (12): 1249-1257.
Poumot, C. 1989. Palynological evidence for
eustatic event in the tropical Neogene
Bulletin Centre De Recherches
Exploration-Production Elf-Aquitaine.. 13
(2) pp 437-453
Sowunmi, M.A., 1986. Change of Vegetation with
Time. In Plant Ecology in West Africa.
John Wiley and Sons, New York, pp: 273-
307.
Vermoere, M., Degryse, P., Vanhecke, L.,
Muchez, P., and Panlissen, E., 1999.
Pollen analysis of two travertine sections
in Basköy (southwestern Turkey):
Implications for environmental conditions
during the early Holocene. Review
Palaeobotany Palynology.105: 93-110.
14
PETROLOGY AND GEOCHEMISTRY OF BASEMENT GNEISSIC ROCKS IN OKA-
AKOKO AREA OF ONDO STATE, SOUTHWESTERN NIGERIA.
1,2Adegbuyi, O, 1Akinyemi, O. M, 1Ogunyele, A. C. 1Department of Earth Sciences, Adekunle Ajasin University, P.M.B 001,
Akungba-Akoko, Ondo State, Nigeria. 2Department of Geological Sciences, College of Natural and Applied Sciences,
Achievers University, Owo, Nigeria.
Correspondence Author’s e-mail/mobile no – [email protected]/+2348036768984
ABSTRACT
The gneissic rocks of Oka-Akoko forms part of the Migmatite-Gneiss Complex of the southwestern
Nigerian Basement Complex. The main petrologic units within the study area include grey gneiss,
granite gneiss, older granite and other minor felsic and basic rocks (pegmatite, aplite, vein quartz and
amphibolite). Twelve gneissic rock samples (6 granite gneisses, 6 grey gneisses) from the area were
collected for petrographic and geochemical characterization. Petrographic analysis revealed that the
granite gneiss samples contain quartz (31.2–37.7%), plagioclase (17.4– 23.9%), opaque minerals
(2.5–6.1%), biotite (12.3–23.0%), microcline (16.6–25.2%), orthoclase (1.2–6.7%) and hornblende
(2.1–7.3%). In the grey gneiss samples, the following result was obtained: quartz (27.0–28.8%),
plagioclase (24.6–26.7%), opaque minerals (7.3–8.7%), biotite (11.5–16.1%), microcline (8.2–
11.4%), orthoclase (4.4–6.9%) and hornblende (9.4–13.0%). Petrographic and geochemical studies
show that Oka-Akoko granite gneisses and grey gneisses were derived from igneous protoliths of
granitic and granodioritic composition respectively. Both gneisses are alkalic, peraluminous,
dominantly iron-rich and characterized by intermediate-high silica content and low-moderate amount
of mafic minerals. These characteristics suggest that both rocks are S-type granitoids which were
derived from the partial melting of crustal rocks with conditions of limited availability of H2O and low
oxygen fugacity.
KEYWORDS: Petrography, Geochemistry, Gneiss, Granitic, Granodioritic.
INTRODUCTION
Oka-Akoko area forms part of the Precambrian
Basement Complex of Southwestern Nigeria,
comprising mainly of the Migmatite-Gneiss-
Quartzite Complex which is of Archean –
Proterozoic age averagely >2Ga (Annor, 1995;
Dada et al., 1998), the Late Proterozoic Schist
Belts (Turner, 1983; Fitches et al., 1985) and
the Older Granitoids of Pan-African age (500-
750Ma) which intruded the former two units
(Rahaman, 1976; Ajibade, 1982; Ekwueme,
1990). The area comprises mainly of gneisses
in association with other rock types which
include porphyritic granite, pegmatite, aplite,
quartz vein and amphibolite. The gneisses are
of two types: granite gneisses and grey
gneisses. Rahaman (1976) and Rahaman and
Ocan (1988) referred to the grey gneisses as
early or quartzo-feldspathic gneisses and
explained that they are granodioritic to quartz-
dioritic or tonalitic in composition. The granite
gneiss forms part of the felsic components of
the Migmatite-Gneiss complex (Rahaman,
1976). The grey gneisses are the second most
abundant rock type in the area forming
enclaves within the granite gneisses. They are
dark grey in colour and are medium-coarse
grained with well developed mineralogical
bands. The light coloured bands are quartzo-
feldspathic while the dark bands are biotite-
rich. The grey gneisses contain intrusions of
pegmatites and quartzo-feldspathic veins and
are regarded as the oldest rocks in the area into
which all other rocks in the area were intruded.
The granite gneisses are light coloured,
medium-coarse grained and characterised by
15
weak foliation defined by the alignment of
streaks of light and dark coloured minerals.
The granite gneisses contain xenoliths of the
grey gneisses and amphibolites. This indicates
that the granite gneisses post-date the grey
gneisses in the study area.
These gneisses (grey and granitic varieties) are
widespread in the area constituting about 90%
of the rock types found in the area and have
been intruded by the Pan-African granites.
They occur as massive rugged hills and rolling
plains assuming batholithic dimensions and
forming impressive outcrops which tower few
hundred metres above the surrounding
lowlands and showing different types of
geological structures such as folds, faults,
foliation, joints, veins, etc. These structures
show that the area has been subjected to at
least two phases of deformation.
Metamorphism in this area is of granulite
facies grade (Rahaman and Ocan, 1988).
METHODOLOGY
The study area was mapped and 12 fresh
representative gneissic samples (6 granite
gneisses, 6 grey gneisses) were collected for
petrographic and geochemical studies. Thin
sections of the samples were prepared and
studied under a petrological microscope. The
minerals present in the thin sections were
identified and counted by the microscope and
photomicrographs were captured. X-ray
fluorescence spectrometer (XRF) was used to
determine the major elements present in the
gneissic rocks. Detailed processes of the
methods of study are contained in Akinyemi,
2014. The mineralogical and geochemical
results were plotted on discrimination
diagrams for the purpose of petrological
classification, determination of chemical
affinities and petrogenesis.
RESULTS/DISCUSSIONS
Petrographic study results (Table 1) revealed
that the granite gneiss samples contain quartz
(31.2–37.7%), plagioclase (17.4– 23.9%),
opaque minerals (2.5–6.1%), biotite (12.3–
23.0%), microcline (16.6–25.2%), orthoclase
(1.2–6.7%) and hornblende (2.1–7.3%). In the
grey gneiss samples, the following result was
obtained: quartz (27.0–28.8%), plagioclase
(24.6–26.7%), opaque minerals (7.3–8.7%),
biotite (11.5–16.1%), microcline (8.2–11.4%),
orthoclase (4.4–6.9%) and hornblende (9.4–
13.0%). The QAP diagram of Streckeisen,
1976 revealed that the granite gneisses are
granitic while the grey gneisses are
granodioritic in composition.
The geochemical analysis (Table 2) shows that
the granite gneisses of Oka-Akoko contain
predominantly SiO2 (65.34-69.78wt%), Al2O3
(15.68-17.46wt%), K2O (4.33-4.67wt%), Na2O
(3.62-4.42wt%), FeO (1.33-2.03wt%) and
Fe2O3 (1.01-1.74wt%) while the grey gneisses
contain mainly SiO2 (59.49-62.76wt %), Al2O3
(15.67-18.66wt%), Na2O (4.31-5.31wt%), K2O
(3.12-5.65wt%), Fe2O3 (2.67-5.53wt%), FeO
(2.11-3.67wt%), and CaO (2.63-4.53wt%). The
granite gneisses of Oka-Akoko are more
siliceous than the grey gneisses. Hence, based
on silica content, the granite gneisses are silicic
or acidic while the grey gneisses are
intermediate in composition. This further
supports the granitic nature of the granite
gneisses and granodioritic composition of the
grey gneisses as revealed by the QAP diagram
and asserted by Rahaman and Ocan, 1988 and
Ademeso and Adeyeye, 2011. Also, the granite
gneisses contain more K2O than the grey
gneisses and this is reflected in the higher
amount of K-feldspars (microcline and
orthoclase) present in the former than the
latter. However, the grey gneisses contain
more TiO2, Al2O3, FeOtotal, MgO, CaO, and
Na2O than the granite gneiss and this account
for the higher amount of opaques(iron minerals
and others), hornblende, and plagioclase in the
grey gneisses than the granite gneisses.
Various petrochemical variation diagrams
reveal that both gneisses are similar – they are
alkalic, strongly peraluminous, dominantly
iron-rich, have intermediate-high silica content
and low-moderate amount of mafic minerals
and these suggests that they are of similar
origin. It is inferred that both rocks were
derived from the partial melting of crustal
rocks (S-type granitoids) with conditions of
limited availability of H2O and low oxygen
fugacity (Taylor and McLennan, 1981; Tarney
and Windley, 1977; Frost et al., 2001).
16
Table 1: Modal Composition of the Granite Gneisses (GGN) and Grey Gneisses (gGN) of Oka-
Akoko.
Minerals
Percentage in wt%
GGN1 GGN2 GGN
3
GGN
4
GGN
5
GGN
6
Ave.
GGN
gGN
1
gGn
2
gGn
3
gGN
4
gGN
5
gGN
6
Ave.
gGN
Quartz 34.0 36.7 31.2 33.3 34.6 31.9 33.62 28.0 27.1 27.9 27.0 28.8 27.0 27.63
Plagioclase 17.4 23.1 21.2 22.9 19.9 18.7 20.53 24.0 26.1 24.6 26.6 26.7 26.1 25.68
Microcline 19.1 24.7 16.6 25.2 19.0 21.1 20.95 11.4 8.0 11.4 11.2 10.1 11.3 10.57
Orthoclase 2.0 1.2 5.2 1.4 2.1 6.7 3.10 5.1 4.9 6.1 4.4 6.9 5.5 5.48
Hornblende 2.1 2.1 7.1 3.8 7.3 2.4 4.13 13.0 12.1 9.4 9.8 10.1 9.5 10.65
Biotite 20.3 10.6 14.1 13.0 15.1 15.1 14.70 11.1 14.1 14.5 11.5 12.1 16.1 13.23
Opaques 5.4 3.7 4.9 2.5 3.1 6.1 4.28 8.7 7.1 8.7 7.3 7.1 7.1 7.67
Total 100.2 99.7 100.
3
102.
1
101.
1
102.
0
101.31 101.
3
99.4 102.
6
97.8 101.
8
102.
6
100.91
17
Table 2: Major element compositions of Granite Gneisses (GGN) and Grey Gneisses (gGN) of
Oka-Akoko
Major
oxides
Weight Percentages (wt %)
GGN1 GGN2 GGN3 GGN4 GGN5 GGN6 gGN1 gGn2 gGn3 gGN4 gGN5 gGN6
SiO2 66.72 65.34 69.78 66.73 66.40 68.10 62.66 60.76 59.49 62.60 59.50 62.76
TiO2 0.44 0.41 0.4 0.43 0.46 0.40 0.41 0.93 1.04 0.81 0.50 0.90
Al2O3 16.52 17.46 15.68 17.43 16.68 16.73 15.73 17.82 18.66 15.67 17.50 17.70
Fe2O3 1.63 1.74 1.01 1.64 1.33 1.80 2.67 2.53 2.87 4.10 5.53 3.32
FeO 2.03 1.98 1.33 1.33 2.07 1.52 3.67 4.33 3.97 2.34 3.23 2.11
MnO 0.05 0.07 0.25 0.31 0.10 0.09 0.11 0.11 0.12 0.11 0.13 0.12
MgO 1.00 1.22 0.68 0.81 1.21 0.98 0.66 1.67 1.29 1.70 1.31 1.10
CaO 2.62 2.74 1.58 2.22 2.35 1.38 2.63 4.12 4.43 2.84 4.53 2.63
Na2O 4.40 3.78 4.42 4.40 4.42 3.62 5.31 4.31 4.33 4.40 4.31 5.31
K2O 4.33 4.57 4.35 4.33 4.67 4.66 4.65 3.12 3.74 5.65 4.43 3.34
P2O5 0.17 0.18 0.16 0.15 0.16 0.14 0.12 0.12 0.11 0.12 0.11 0.11
LOI 0.11 0.33 0.23 0.19 0.13 0.43 0.71 0.91 0.10 0.12 0.20 0.48
TOTAL 100.02 99.82 99.88 99.797 99.98 99.85 99.33 99.81 99.99 100.34 101.28 99.98
18
CONCLUSION
This study shows that the granite gneisses and
grey gneisses of Oka-Akoko are iron-enriched,
peraluminous, potassic orthogneisses of granitic
and granodioritic composition respectively
derived from the partial melting of crustal rocks
with conditions of limited availability of H2O
and low oxygen fugacity.
REFERENCES
Ademeso, O. A. and Adeyeye O. (2011): The
Petrography and Major Element Geochemistry
of the Granite Gneiss of Arigidi area, S/W,
Nigeria. Nature and Science 2011; 9(5):7-12.
Akinyemi, O. M. (2014): Petrographic and
Geochemical studies of Basement Gneissic
Rocks in Oka-Akoko area of Ondo state,
Southwestern Nigeria. Unpublished B.Sc
Dissertation, Dept. of Earth Sciences, AAU,
Akungba-Akoko.
Ajibade, A. C. (1982): Origin and emplacements
of the Older granites of Nigeria: some evidence
from the Zungeru region. Nigerian Journal of
Mining and Geology, 19(1): 221-230.
Annor, A. E. (1995): U-Pb Zircon age for
Kabba-Okene granodiorite gneiss: Implication
for Nigeria’s Basement Chronology. Africa Rev.
2:101-105.
Dada, S. S., Briqueu, L. and Birck, J. L. (1998):
Primordial crustal growth in northern Nigeria:
Preliminary Rb-Sr and Sm-Nd constraints from
Kaduna migmatite gneiss complex. J. Min.
Geol., 34, pp. 1-6.
Ekwueme, B. N. (1990): Rb-Sr ages and
petrologic features of Precambrian rocks from
Oban massif, southeastern Nigeria. Precambrian
Res., 47:271-286.
Fitches, W. R., Ajibade, A. C., Egbuniwe, I. G.,
Holt, R. W., and Wright, J. B. (1985): Late
Proterozoic schist belts and plutonism in NW
Nigeria. Jour. Geol. Soc. Lond., 142: 319-337.
Rahaman, M. A. (1976): Review of the
Basement Geology of Southwestern Nigeria. In:
Geology of Nigeria (C.A. Kogbe, Ed).
Elizabethan Publ. Co. Lagos, pp. 41- 48.
Rahaman, M. A. and Ocan, O. (1988): The
nature of Granulite Facies Metamorphism in
Ikare Area, Southwestern Nigeria. In:
Precambrian Geology of Nigeria. GSN Publ. pp.
157-163.
Tarney, J. and Windley, B. F. (1977):
Chemistry, thermal gradients and evolution of
the lower continental crust. Journal of
Geological Society of London, 134:153-172.
Taylor, S. R. and McLennan, S. M. (1981): The
composition and evolution of the
continental crust: rare earth elements evidence
from sedimentary rocks. Phil. Trans. R. Society
of London, A30:381-399.
Turner, D. C. (1983): Upper Proterozoic Schist
Belts in the Nigerian Sector of the Pan-
African Province of West Africa. Precambrian
Research 21, pp. 55-79.
19
MINERALOGICAL AND INDUSTRIAL PROPERTIES OF CLAY IN SOSAN AKOKO,
SOUTHWESTERN NIGERIA
A.A. Adeseko, and A.T. Bolarinwa
African Regional Center for Space Science and Technology Education in English, OAU, Ile-Ife.
Department of Geology, University of Ibadan, Oyo State.
Corresponding Author: A.A. Adeseko (Email: [email protected])
ABSTRACT
Clay is a versatile mineral consumed in various manufacturing industries. In response to the challenges
that may be posed by the demand for clay materials in Nigeria, indigenous clays with industrial potentials
need to be investigated. However, clay deposit in Sosan Akoko area of Southwestern Nigeria was
explored in order to determine its industrial suitability. Fifteen representative clay samples were
collected from three pits dug in three locations in the area and subjected to mineralogical, chemical and
physical analyses. The mineralogical results from the XRD analysis show that Kaolinite (1.44 %) and
Nontronite (2.77 %) are the major clay minerals present while quartz is the major non-clay mineral
which constitutes up to 83.27% in the clay. Other non-clay minerals in the clay include orthoclase (3.78
%), Labradorite (4.92 %) and Albite (2.81 %) in subordinate amounts. Chemical analysis data showed
average values of SiO2 at 58.03%, Al2O3 at 13.38% and Fe2O3 at 7.66%, which represents more than 70%
bulk chemical composition. Wet sieve analysis indicate that the clay size (<2µm) fraction of the clay
samples is above 55%. Plots of plasticity indices showed that the clay sample is inorganic of moderate to
high compressibility and plasticity. The overall results showed that the clay materials could serve as raw
materials in the manufacture of paints, ceramic pots, cosmetics, building bricks and for waste water
treatment. It further revealed that the silica sesquioxide and alumina-iron ratio are within the range
considered for utilization in the manufacture of good quality cement.
Keywords: Clay, Sosan Akoko, Minaralogical, Industrial, Sesquioxide
INTRODUCTION
Clay is an abundant raw material which has an
amazing variety of uses and properties that are
largely dependent on their mineral structure and
composition. Other than the clay structure and
composition, there are several additional factors
which are important in determining the
properties and applications of a clay. These are
the non-clay composition, the presence of
organic material, the type and amount of
exchangeable ions and soluble salts and the
texture. However, the varieties of clays with
different structures and chemical compositions
have been discovered in Nigeria, but many clay
deposits in Nigeria still remain unidentified and
uncharacterized considering the quality and
quantity that occur in the country. The
underutilization of the clay deposits spread
across the country may be ascribed to
insufficient geological information on the
assessment of their properties as well as shallow
knowledge on the appropriate and effective
usage of each deposit discovered. Therefore, in
response to the challenges that may be posed by
the demand for clay materials in Nigeria,
indigenous clays with industrial potentials need
to be investigated. Hence, clay deposit in Sosan
Akoko area of Southwestern Nigeria was
explored in order to determine its industrial
suitability.
MATERIALS AND METHODS
The scope and method of investigation includes
geological field studies and collection of
samples. Fifteen clay samples were collected
from three pits dug in three different locations
within the Sosan clay body. Five samples were
collected from each of the weathering profile
from top to the depth of about 2.5m with the aid
of shovel and a digger. Twelve representative
samples out of the fifteen samples collected
were air-dried and disaggregated for
geotechnical tests while the pulverized samples
were subjected to mineralogical and chemical
analyses. Mineralogical analyses were
undertaken using the x-ray diffraction technique
(XRD). Inductively coupled plasma
20
spectrometer (ICP-MS) method was employed
to determine the major and trace elements
composition. These two analyses were
conducted in ACME laboratory in Vancouver,
Canada. Geotechnical tests include grain size
analysis, specific gravity, firing characteristics,
plasticity indices and linear shrinkage
determination which was conducted at the
Engineering geology laboratory, FUTA.
RESULT AND DISCUSSION
The mineralogical data showed that the clay is
composed of Nontronite and Kaolinite as the
major clay minerals. The diffractograms also
showed the abundance of quartz in the sample as
the major non-clay mineral with minor amount
of orthoclase and labradorite as well as
albite.Conspicuous kaolinite peaks reflected at
7.13A, Nontronite 15.76A, Quartz peaks are
identified at 4.2A, 3.33A and 1.81A as indicated
in figures 1, 2 and 3 respectively. The
mineralogical data of the whole sampleusing the
peak height ratio analysis showed that the
sample is composed of about 83.27% Quartz,
1.4% kaolinite and 2.77% nontronite, Iron-rich
montmorillonite clay of the smectite group.
Major element abundances of SiO2 (ca.58.03%),
Al2O3 (ca.13.38%) and Fe2O3 (ca.7.66%)
represent more than 70% of the bulk chemical
compositions as indicated in Table 1 while CaO,
MgO, Na2O, K2O, MnO, TiO2 and P2O5
relatively have lower values.The predominance
of SiO2 and Al2O3 which constitute the bulk
chemical composition of the Sosan clay is in line
with its classification as hydrated aluminum
silicates. The relatively high value of Fe2O3
(7.66) is probably due to tropical weathering and
the lateritic horizon overlying the clay deposit.
The K2O average composition of ca. 2.72
indicates that, feldspar has not been intensely
weathered. The amount of fine in the samples
ranges from (63-66%) and the percentage of clay
size particles between 50-53%, Silt 10-15% and
sand 34-38%. The grading curve indicates well
graded sandy clay (fig.4). The plot of plasticity
index values against the liquid limit value for the
clay sample showed that all the clay samples
falls within the region of moderate to high
toughness and compressibility. As shown on the
chart, the clay bodies are inorganic clay of
medium to high plasticity above A-line (fig.5).
CONCLUSION
Mineralogical composition based mainly on X-
ray diffraction studies confirms that the clay is
dominated by Nontronite and Kaolinite while
quartz is the major non-clay mineral present.
Orthoclase and Labradorite are present in minor
amounts as well as albite. Major element
abundances of SiO2 (ca.58.03%), Al2O3
(ca.13.38%) and Fe2O3 (ca.7.66%) represent
more than 70% of the bulk chemical
compositionswhile CaO, MgO, Na2O, K2O,
MnO, TiO2 and P2O5 relatively have lower
values. The presence of moderately high ferric
oxide imparted a reddish brown colourization.
This also supports the presence of Nontronite,
the iron-rich montmorillonite clay. On the basis
of physical parameters, plots of plasticity indices
showed that the clay sample is inorganic clay of
moderate to high plasticity, compressibility and
toughness with the clay-size fraction (<2µm)
above 55%. This is due to the greater
concentration of the fine clay-size materials and
Nontronite. The shrinkage values are relatively
high (ca.6.31%) and the loss on ignition (ca.
11.9%). Adequate mouldability characterizes the
clay with an acceptable firing colour of reddish
brown and yellowish brown. The clay-sized
body is very dense with an average specific
gravity of ca. 2.7. The mineralogical, chemical
and physical characteristics of these residual
bodies showed they are amenable to
beneficiations. For instance, the removal of the
non-clay fractions and gritty content could
upgrade the clay. Similarly, chemical treatment
of Fe2O3 through leaching method and other
impurities could enhance the Al2O3 content and
depreciate SiO2 abundances. Assessment of
industrial suitability of the Sosan clay based on
the mineralogy, geochemistry, physical
properties and the fine nature of the clay and
also with appropriate processing which include
screening of quartz and iron oxide minerals and
bleaching, the clay materials could serve as raw
materials in the manufacture for paints, ceramic
pots, cosmetics, building bricks and for waste
water treatment. It further reveals that the silica
sesquioxide and alumina-iron ratio are within
the range considered for utilization in the
manufacture of good quality cement.
21
Fig.1: Diffractogram of the whole rock sample
of Sosan clayFig.2: Diffractogram of the whole
rock sample of Sosan clay
Fig. 3: Diffractogram of the whole rock sample
of Sosan clay Fig. 4: The average
curve of Sosan clay
Fig. 5: Plasticity chart for the classification of
Sosan clay (After Cassagrande, 1948)
GRAIN SIZE ANALYSIS
Client: Date:
Project:
Location:
Borehole No. Sample No. SOS 1a Depth, mt.:
Sieve Analysis
100.000 100.0
75.000 100.0
63.000 100.0 D 10 = NA Cu = NA
37.500 100.0 D 30 = NA
20.000 100.0 D 60 = NA Cc = NA
14.000 100.0 0
6.300 100.0 0
3.350 100.0 0 Gravel = 0.76% Gravel = 0.76%
2.000 1.20 0.76 99.2 1.2 Coarse Sand = 2.03%
Coarse 0.600 3.20 2.03 97.2 3.2 Medium Sand = 11.34% Sand = 33.65%
0.425 4.10 2.60 94.6 4.1 Fine Sand = 20.28%
0.300 6.50 4.12 90.5 6.5 Fines = 65.59% Fines = 65.59%
0.212 7.30 4.63 85.9 7.3
0.150 9.30 5.89 80.0 9.3
0.106 12.30 7.79 72.2 12.3 Moisture Content % = 8.0 %
0.063 10.40 6.59 65.6 10.4
<0.063 103.51 65.59 Bulk weight = 170.4 g
Sum 54.30 100.00
Initial wgt 157.81 Dry weight = 157.8 g
S
A
N
D
Medium
Fine
FINES
Clay or
Silt
Cobbles
Particle
Description
Diameter
(mm)
Weight
(g)
Retained
(%)
Passing
(%)
G
R
A
V
E
L
Coarse
Fine
16/06/2011
0.002 0.006 0.02 0.06 0.2 0.6 2 6 20 60 200
BS Sieve Appature Size, mm0.425 1.18 3.35 14 75
0.063 0.212 0.6 2 6.3 20 37.5 63
CLAY
FINE
SILT
FINE
SAND
FINE
GRAVEL
COBBLE
MEDIUM COARSE MEDIUM COARSE MEDIUM COARSE
0
10
20
30
40
50
60
70
80
90
100
PE
RC
EN
TA
GE P
AS
SIN
G (
%)
PARTICLE SIZE (mm)
sieve analysis
hydrometer analysis
© skea 2010
22
Table 1: Average chemical analysis of Sosan
clay
Oxides Mean Range
SiO2 58.03 53.10-63.40
Al2O3 13.38 13.72-17.22
Fe2O3 7.66 7.15-8.00
MnO 0.04 0.04-0.05
MgO 0.83 0.55-1.12
Na2O 0.70 0.67-0.72
K2O 2.72 2.31-3.19
TiO2 1.50 1.35-1.67
P2O5 0.03 0.02-0.04
CaO 0.80 0.66-0.92
LOI 11.84 8.90-14.60
S.R = 2.76, A.R = 1.75, Na2O + K2O = 3.42,
CaO + MgO = 1.63, SiO2 + Al2O3 + H2O+
=83.27%
23
Selected References
Grim, R.E., 1950. Modern concept of clay
minerals. J. Geo., 50, 225-275p.
Odo, J.U. and Nwajagu, C.O., 2003. Possible
application of Eha-Alumona clay deposit in the
production of refractories and ceramic wares.
Proceedings of the Nigeria Materials Congress
and Meeting of the Nigerian Nigerian Research
Society at Conference Hall, Engineering
Materials Research Institute, Akure. November
12- 14: 109-119
Cassagrande, A. 1948. Classification and
identification of soils, Am, Soc. Civil Engr. pp.
113-901
Elueze, A.A. and Nton, M.E., 2004. Organic
geochemical appraisal of limestones and shales
impart of eastern Dahomey Basin, Southwestern
Nigeria. Journal of Mining and Geology, Vol.
40, No. 1, pp. 29-40
Murray, H.H. 1960. Clay industrial minerals and
rocks 3rd Ed. Publ. Am inst. of Mining Metall.
and Petroleum Engineers.
Huber, J.M., 1985. Kaolin Clays. Huber
Corporation (Clay Division), Georgia U.S.A.).
24
INTEGRATION OF GEOSCIENCES AND GIS IN SUSTAINABLE INTEGRATED COASTAL
ZONE MANAGEMENT (ICZM) IN NIGERIA
Adesina R.B. and 2Aladejana O.O.
Department of Marine Science and Technology, Federal University of Technology, Akure.
Department of Remote Sensing and GIS, Federal University of Technology, Akure.
Corresponding Author: Email: [email protected]
ABSTRACT
As coastal populations in Nigeria continue to grow, there is severe stress on both the living and non-
living resources. Exploitation of these resources, in addition to natural coastal hazards, can result to loss
or damage of human lives and property, diminishing biodiversity, civil unrest and the destruction of
coastal ecosystem. Several disciplines have focused their attention on the coastal zone, without
considering the interdependence of different key components of the ecosystem, working together to
maintain a balance. In view of the millennium development goals of sustainable development, the
Integrated Coastal Zone Management (ICZM) as a dynamic and multidisciplinary process was developed
to promote sustainable management of coastal zones. In the face of the current global climate change, the
key problems related to coastal zone sustainability in Nigeria include coastal erosion, flooding, pollution,
siltation, seawater intrusion into coastal aquifers and increasing socio-cultural degradation, as well as
poverty. Geoscientists are well equipped to contribute to ICZM, as the requirements and issues for a
sustainable coastal zone management often contain earth-related aspects. Centre to the application of
geosciences in ICZM is the remote sensing and GIS technology to provide spatio-temporal information on
numerous processes acting on any coastal zone. Established models for calculating the effects of coastal
hazards, and their mitigation based on geoscientific expertise are integrated in a GIS.
Keywords: ICZM, Geosciences, GIS, Remote Sensing, Ecosystem
INTRODUCTION
The Integrated Coastal Zone Management
(ICZM) is a dynamic and multidisciplinary
process, developed to promote linkages and
harmonization among various coastal and ocean
usages for sustainable management. The goals of
a sustainable coastal management include the
optimization of the benefits provided by the
coastal zone, to minimize conflicts and to
prevent harmful effects of activities upon coastal
resources and the environment. These zones are
of very high biological productivity and thus an
important component of the global life system.
More so, marine ecosystems play a vital role in
regulating climate and they are a major carbon
sink and oxygen source, thus the urgent need for
its sustainability.
Overview of the Nigerian Coastal
Environment
Nigeria has a coastline of approximately 853km
facing the Atlantic Ocean, and lies between
Latitude 4o10’ to 6o20’N and Longitude 2o45’ to
8o35’E (Fig. 1). The Nigerian coastal and marine
area consists of a narrow coastal strip of land
bordered by the Gulf of Guinea of the Central
Eastern Atlantic. The coastal areas stretch inland
for a distance of about 15 km in Lagos to about
150 km in the Niger Delta and about 25 km east
of the Niger Delta (Awosika and Folorunsho,
2009). The Nigerian coastal geology is basically
sedimentary, and is dominated by the geology of
Niger Delta composed of an overall classic
sequence which reaches a maximum thickness
of 9-12km (Ibe, 1988). The Nigerian coastal
areas are divided into four main geomorphic
zones (Fig. 1): Barrier lagoon, Mahin mud coast,
Niger delta and Strand coastline. The barrier
lagoon coastal complex extends eastward about
250km from the Nigerian-Benin border,
consisting of narrow beach ridges aligned
parallel with the coast (Ibe, 1988). The beaches
are subjected to high-energy waves, resulting in
the formation of characteristically steep beach
profiles (Ibe, 1988).
25
Fig. 1: Map of Coastal Nigeria showing the
main geomorphic units (Modified from Ibe,
1988)
The Mahin mud coast is a muddy coastal
complex, east of the barrier lagoon coast and
stretches to the Benin River in the northwest
flank of the Niger Delta. The coastline has
absence of sand along the beach and the
predominance of silt and clay sized sediments.
The coastal plain embodying this area stretches
about 20km inland. The Niger Delta extends
over an area of about 75,000 km2 covering a
coastline of 560 km, about two-thirds of the
entire coastline of Nigeria. It is rimmed by a
chain of sandy barrier islands, and spread over a
number of ecological zones. The Strand coast
stretches from Imo River eastwards to the Cross-
river estuary along the Nigerian-Cameroon
boundary. The vegetation of the 85 km long
strand coast comprises of mangrove swamps
with species composition similar to those of the
Niger Delta (Awosika and Folorunsho, 2009).
Problems Facing Coastal Zones in Nigeria
Coastal zones in Nigeria are currently facing a
variety of environmental issues coupled with the
threat of global climate change. Consequently,
there is severe stress on both the living and non-
living resources, through physical disruption
(development and exploitation) and addition of
land-based waste products into coastal waters.
Climatic variations also cause changes in the
direction in which waves impact the beach, or
changes in the volumes of sediments discharged
from rivers to the shore were considered to be
determining factors. The effects of the
deposition of silt from suspension, and the
related high levels of turbidity in coastal waters
resulting from river discharge, are likely to
degrade sensitive coral reef ecosystems
(Awosika et al., 2001). Presently, geosciences
information is lacking in the area of coastal zone
resources and pressures in terms of the
geological and geomorphological aspects of the
resource volumes available for exploitation.
There is also the problem of pressures to which
the coastal resources are subjected, which may
be generated by human activities such as beach
sand abstraction and indiscriminate waste
disposal. Alternatively, the pressures may result
from naturally induced events or changes such
as extreme climatic conditions, which may result
in severe coastal erosion and the destruction of
coastal infrastructure. These problems of
resource pressure involve an understanding of
geosciences-related processes such as
sedimentation, erosion and groundwater flow,
and the ways in which those processes may
change with time. Such knowledge applies to the
management of beach erosion and coastal
accretion, to making the best use of groundwater
resources in the coastal zone, and to developing
appropriate policy and management responses to
the problems of pollution in coastal and
estuarine environments. The danger of saltwater
intrusion is also recognised, whether of natural
occurrence or induced by over-abstraction.
Geosciences and GIS for Sustainable ICZM
Geosciences has a potential to add value to
coastal zone resources, either by drawing
attention to its existence, by assessing or
reassessing its quality, or by realising the
importance of its hosting role for other
resources. Any of these mechanisms can feed
through to providing benefit to society, in the
coastal context through ICZM. Geoscientists are
well equipped to contribute to ICZM, as the
requirements for a sustainable coastal zone
management often contain earth-related aspects.
In order to achieve this, it is necessary to
develop accurate, up-to-date and comprehensive
scientific databases on habitats, protected areas,
water quality, and environmental indicators, and
carry out periodic health assessment of the
system. The modern scientific tools of remote
sensing, GIS and GPS are extremely valuable in
26
development of databases and to analyse them in
the integrated manner and derive management
action plans. Availability of repetitive, synoptic
and multi-spectral data from various satellite
platforms viz. IRS, LANDSAT and SPOT, have
helped to generate information on varied aspects
of the coastal and marine environment. Ocean
colour data from OCANSAT I OCM, SeaWiFS,
MODIS, provide information on biological
aspects useful for fisheries and coastal
ecosystems. Satellite based information has been
used in developing countries for generating
inventory on coastal habitats, landforms, coastal
land use and shoreline condition assessment of
protected areas. GIS has been used for the
integrating satellite based information for
identifying aquaculture sites, coastal regulation
and environmentally sensitive zones. GIS helps
as a common ground for the integration of
various datasets from all disciplines in the
geosciences. By providing a platform for
creating geoscience data, archiving, processing
and analysing, major issues necessitating ICZM
such as coastal ecosystems and marine living
resources, shoreline protection, coastal water
quality, coastal hazards and climate change,
coastal development can be solved (Nayak,
2000).
As geological processes form the basis for
calculating the effects of coastal hazards,
prediction models should inevitably be based on
geoscientific expertise. Hazard zonation maps
could be produced to further contribute to
disaster reduction by predicting natural and
man-induced coastal hazards and their impacts
on coastal zones. Mitigation methods and early
warning systems can be developed the
authorities are to be alerted to the effects of
global change, such as the geologically realistic
estimate of sea-level rise.
Geoscientists in Nigeria can contribute to the
prevention of continual contamination of coastal
aquifer from saltwater by forecasting flow paths
of seawater in aquifers. They can also contribute
to the prevention of negative effects of
uncontrolled urbanisation by warning relevant
authorities of erosion/flooding prone areas.
These can be achieved by assisting in the
selection of optimal coastal sites for urban
expansion and urban land use, and by
developing a geo-information system (GIS)
database on the four coastal zones in Nigeria.
The negative effects of dredging and sand
mining can be mitigated by applying
information of environmentally sustainable
siting of plant (industrial complex), and by
developing and applying proper (biogeo-)
remediation methodologies in affected
ecosystems.
Geologists can contribute to poverty alleviation
of coastal communities by taking into accounts
the demand of the rural coastal communities and
by mitigating land deterioration and safe
housing situation thereby reducing potential geo-
hazards. Finally, geoscientists can contribute to
improved education and enlightenment
programmes both at local, state and federal
levels by educating local decision-makers in the
geological background of natural and man-
induced coastal hazards.
CONCLUSIONS
The adoption of Geosciences and GIS in ICZM
for the Nigerian coastal zones will ensure that
extraction or exploitation of mineral resources is
achieved in the most cost effective way and
without irreversible disruption or destruction of
the surrounding ecosystem. In such cases,
geosciences information can be integrated with
ecological and socio-economic expertise at the
planning stage. Accurate geological mapping of
the coastal zones will provide managers and
planners with the information needed to avoid
problems such as settlement of buildings and
aggressive attack of seawater on coastal
structures. Although geosciences in Nigeria is
focused on the exploration sectors, the target and
job markets for geoscientists tend to shift
towards the service sector producing a client-
oriented professional with broad,
multidisciplinary backgrounds who will not
solely focus on a geological approach for
problem solving, but also try to develop a total
solution through ICZM. Geo-information system
hence provides closely-related disciplines an
enabling environment in a spatio-temporal
model on geoscientific expertise.
27
REFERENCES
Awosika L.F., Osuntogun N.C., Oyewo E.O.and
Awobamise A. 2001.Development and
protection of the Coastal and Marine
Environment in Sub Sahara Africa:
Report of the Nigeria Integrated
Problem Analysis. 142p.
Awosika, L.F. and Folorunsho, F., 2009. African
Oceans and Coasts. Odido M. and
Mazzilli S. (Eds). IOC Information
Document, 1255, UNESCO Regional
Bureau for Science and Technology in
Africa, Kenya. 163p.
Ibe, A.C., 1988. Coastline Erosion in Nigeria.
Ibadan University Press, Ibadan, 217p.
Mmom, P.C. and Chukwu-Okeah, G.O, 2011.
Factors and Processes of Coastal Zone
Development in Nigeria: A Review.
Research Journal of Environmental and
Earth Sciences 3(6): 625-632.
Nayak, S. 2000. Critical issues in coastal zone
management and role of remote sensing.
In Subtle Issues in Coastal Management,
Indian Institute of Remote Sensing,
Dehradun. Pp. 77-98.
28
RESERVOIR CHARACTERIZATION AND RESERVE ESTIMATION OF “AFONJA” FIELD,
NIGER DELTA, USING WELL LOGS AND 3-D SEISMIC DATA.
Olumide Adewoye and John O. Amigun
Department of Applied Geophysics, Federal University of Technology, Akure, Nigeria.
Authors E-mail:[email protected], [email protected]
ABSTRACT
The aim of this research is to characterize the reservoirs and estimate the hydrocarbon reserve of
“Afonja” field Niger Delta using well logs and 3-D seismic data. Suite of well logs for six wells which
comprises of gamma ray, resistivity, neutron, density and sonic logs, 3D seismic data, and check-shot
data were analyzed and interpreted with petrel software for this study. The research methodology
adopted involve delineation of lithology and identification of reservoirs from well logs, well correlation,
determination of petrophysical parameters, well seismic tie, horizon and fault mapping, time to depth
conversion and reserve estimation. Five hydrocarbon reservoirs R1, R2, R3, R4 and R5 respectively were
revealed from Well logs analysis. Petrophysical parameters were evaluated with the gross thickness
ranges from 13 m to 60 m. Net/Gross ranges from 0.73 to 1.00, Effective porosity ranges from 0.29 to
0.42, hydrocarbon saturation ranges from 0.52 to 0.94 and volume of shale ranges from 0.02 to
0.14.Structural analysis deduced fault assisted structurally high anticlines and the reservoirs area extent
with a range of 1977-3459 acres across the field. Estimated gas initially in place (GIIP) was 483 billion
standard cubic feet (SCF) and 60% recoverable gas reserve was 290 billion (SCF). Similarly, estimated
stock tank original oil in place (STOOIP) was 970 million stock tank barrel (STB) and 35% recoverable
oil reserve was 339million stock tank barrel (STB) oil.
Keywords: reservoir characterization; reserve estimation, recoverable oil and gas, formation volume
factor & Niger delta.
INTRODUCTION
The objective of any exploration company is to
find new hydrocarbon reserves at a low cost and
in a short period of time (Frank et al., 2003).
Exploration and exploitation for hydrocarbon
using geophysical survey and the subsequent
exploitation via drilling of wells require large
capital. In order to avert any loss or wastage of
resources there is need to properly and
adequately characterize reservoirs and determine
the recoverable hydrocarbon. This will help to
ascertain the hydrocarbon potential of the
reservoirs. Potentials of oil reservoirs can be
determined using the results of the petrophysical
analysis. Good reservoir must be porous,
permeable, oil saturated and of appreciable
thickness (Adewoye et al., 2013 hence, accurate
determination of these parameters is therefore
necessary. Reservoir characterization study is to
integrate geological, 3D seismic and well log
petrophysical data in identifying the geometry,
continuity, internal structure and quantity of
hydrocarbon within the reservoir. The
knowledge of reservoir dimension is an
important factor in quantifying producible
hydrocarbon (Schlumberger, 1989). Among the
needed information includes the thickness and
area extent of the reservoir. Deduction of the
relevant reservoir parameters is made from well
logs and 3-D seismic data for the computation of
the volume of hydrocarbon in place and hence
the hydrocarbon reserves.
Location and Geology of the Study Area:
“Afonja” field is situated within offshore Niger
Delta, between Longitudes 30 – 90E and latitudes
40 – 60N (Fig. 1). There are 6 wells and a total of
762 crosslines and 883 inlines. The stratigraphy
of the Niger Delta has been described by Short
and Stauble (1967) and Frankl and Cordy (1967)
in detail.
29
Figure 1: Location and Base Map of the
Study Area.
METHODOLOGY
Materials used for this research work include:
3-D seismic data, checkshot data, suit of
wireline log data - gamma ray, resistivity,
neutron, sonic, and density logs. For the data
analysis and interpretation, Petrel software was
used. Lithologies were delineated using gamma
ray log. Hydrocarbon bearing reservoirs were
identified using both gamma ray and resistivity
logs. Fluid contacts within the reservoir intervals
were established from a cross-over of neutron
and formation density logs. Petrophysical
parameters were calculated from wells using
appropriate formulae (Halliburton, 2001). Wells
were tied with seismic data using checkshot
data. Horizons corresponding to the top of the
reservoirs were mapped across the 3D seismic
volume, faults were picked and fault polygons
were generated. Time surface maps were
generated across picked seismic horizons and
then converted to depth structural maps using
the time-depth conversion data. Reservoirs’ area
extents were calculated using square grid
method from depth structure maps. Area extent
of each reservoir was determined from the depth
structural maps. The last close contours were
gridded in square. The total number of the
square within the reservoir was multiplied by the
unit area in order to get the total area extent of
the reservoir. Average values of reservoir
parameters such as thickness, Net/Gross,
Porosity and hydrocarbon saturation were
computed. Formation volume factors for oil and
gas were used for the calculation of oil and gas
reserves of “Afonja” Field, Niger Delta.
RESULTS AND DISCUSSION
Well logs petrophysical analysis and seismic
interpretation results of “Afonja” oil field were
carried. Five hydrocarbon bearing reservoirs R1,
R2, R3, R4 and R5 were delineated across
“Afonja” oil field using well log data. Figure 2
(a) show two hydrocarbon reservoirs R1 and R2
that occur within four of the wells. R1 and R2
occur at depth; (1330m) and (1370m)
respectively in Afonja 6, (1328m) and (1369m)
respectively in Afonja 4, (1328m) and (1366m)
respectively in Afonja 1, (1356m) and (1389m)
respectively in Afonja 3. Reservoirs R3, R4, and
R5 were observed only in Afonjas 6, 4, 1, and 3
as shown in Figure 2 (b).
The Figure 2 (c) shows the fluid contacts in
reservoir R2. Gas-oil contact occurs at depth of
1383 m where there is crossover between the
density and neutron logs. The oil - water contact
occurs at the depth of 1386 m.
Table 1 and 2 show the average values of
computed petrophysical parameters for reservoir
R1, R2, R3, R4, and R5. The gross thickness
across R1 ranges from 13 m to 26 m. Its net
thickness ranges from 10 m to 25 m, Net/Gross
ranges from 0.77 to 1.00, Effective porosity
ranges from 0.27 to 0.39, hydrocarbon saturation
ranges from 0.52 to 0.94 and volume of shale
ranges from 0.02 to 0.09.
Synthetic seismogram was generated using
acoustic impedance log (computed from sonic
and density logs), reflection coefficient log and a
wavelet (Figure 3). The checkshot data was
imported and attached to appropriate wells, the
wells were uploaded on the seismic section and
the gamma ray (GR) and resistivity (RES) logs
were displayed, the reservoir tops were mapped
and picked as horizons (Figure 4).
30
(a)
(b)
(c)
Fig. 2 Well correlation panels
Figure 3: Synthetic Seismogram
Figure 4: The Tying of Wells to Seismic Section
using Checkshot Data
In
orde
r to
kno
w
the
area
exte
nt of
reser
voirs
,
depth structure maps were generated using look
up function from checkshot data. Five depth
structure maps for the five reservoirs give the
depth to the top of the reservoirs figures 5 (a-e).
Faults where mapped, reservoir area were
mapped at the last close contour and were
calculated to be 10km2, 12km2, 12km2, 6km2 ,
9.6km2 for reservoirs R1, R2, R3, R4 and R5
respectively using square grid method. Oil and
gas reserves in “Afonja” field were estimated
using appropriate formulae and were
summarized in table 1 and 2.
31
(a) (b) (c) (d) (e)
Table 1 Reservoir estimation of gas bearing reservoir.
Table2 Reservoir estimation of oil bearing reservoir .
CONCLUSIONS
In order to characterize reservoirs and estimate
the reserve of “Afonja” field, hydrocarbon
bearing reservoirs were delineated, petrophysical
analysis was carried out, structural interpretation
was done, reservoirs area extent were mapped
and hydrocarbon reserve was estimated.
The reservoirs area extent has a range of (1977-
3459) acres across the field.
Estimated gas initially in place (GIIP) was 483
billion standard cubic feet (SCF) and 60%
recoverable gas reserve was 290 billion standard
cubic feet (SCF). Similarly, estimated stock tank
original oil in place (STOOIP) was 970 million
stock tank barrel (STB) and 35% recoverable oil
reserve was 339 million stock tank barrel (STB)
oil. Three hydrocarbon prospects were identified
across the field. These prospects are suspected to
host hydrocarbon.
REFERENCES
Adewoye O. Amigun J. O., Okwoli E., and Cyril
A. G., (2013)Petrophysical And Structural
Analysis Of Maiti Field, Niger Delta, Using
Well Logs And 3-D Seismic Data, Petroleum
& Coal, 55 (4), pp. 302-310.
Figure 5: Depth Structure Maps for (a) Horizon 1 (b) Horizon 2 (c) Horizon 3 (d) Horizon 4 (e)
Horizon 5 “Afonja” field
32
Frank E.J. and Cordy E.A (1967) The Niger
Delta Oil Province Recent Development.
Onshore and Offshore Proceedings of
Seventh Word Petroleum Congress Mexico
City, 195 – 209.
Frank Jahn, Mark Cook and Mark Graham,
(2003), Hydrocarbon exploration and
production. Elsevier Science Ltd.,
Amsterdam. p. 15-16
Halliburton (2001) Basic Petroleum Geology
and Log Analysis, p 19-74
Schlumberger (1989). Log Interpreation,
Principles And Application: Schlumberger
Wireline And Testing, Houston,Texas, pp.
21-89
Short K.C and Stauble A.J., (1967) Outline of
Geology of Niger Delta. America
Association of Petroleum Geologists.
Bulletin, 51 761 – 779
33
DEVELOPMENT OF A ROAD FAILURE VULNERABILITY MAP FROM INTEGRATION OF
GEOPHYSICAL AND GEOTECHNICAL STUDIES OF A PROPOSED ROAD, IPINSA-AKURE,
SOUTHWESTERN, NIGERIA.
Adiat, K.A.N, Adegoroye, A.R., Akinlalu A.A.
Department of Applied Geophysics
Federal University of Technology Akure, Ondo State, Nigeria
Corresponding Author e-mail: [email protected]
ABSTRACT
Integration of geotechnical and geophysical investigations involving Magnetic, Very Low Frequency
Electromagnetic (VLF-EM) and Electrical Resistivity methods were carried out along Akure-Ipinsa road
in order to investigate the competence of the proposed road for pavement stability. Qualitative and
quantitative interpretation of the magnetic profiles provides information on the basement topography and
structural disposition beneath the proposed road. The VLF-EM method assist in depicting the geometry of
the conductors that are related to suspected linear features. Vertical electrical sounding results helped in
the delineation of four geo-electric layers namely the top soil, weathered layer, partly
weathered/fractured basement and fresh basement. The top soil constitute the subgrade and is generally
characterized by low resistivity values which suggest weak engineering materials. The presence of partly
weathered/fractured basement beneath the proposed road also brings the bearing capacity of the bedrock
under question. Geotechnical test (consistency limit, moisture content, grain size analysis, compaction
and California bearing ratio) carried out on the sampled soils reveals that most of the soil is clayey in
nature and as such not good for engineering works. Vulnerability map generated from the results
obtained from geophysical and geotechnical studies classified the road segment into three segments of
vulnerability namely high, moderate and low vulnerability zones. It is estimated that 60% of the road is
moderately vulnerable while 30% and 10% of the road are rated to be of high and low vulnerability
respectively. This suggest that the proposed road will be vulnerable to pavement failure if necessary
engineering precautions are not adhered to
Keywords: Pavement Stability, Basement Topography, Geotechnical Tests.
INTRODUCTION
Although virtual connectivity has become
increasingly important today with the emergence
of new communication avenues, a good and
reliable transport network remains vital. Roads
are integral part of the transport system and as
such play a significant role in achieving national
development and contributing to the overall
performance and social functioning of the
community. It is acknowledged that roads
enhance mobility, taking people out of isolation
and therefore poverty. Since there is a very
strong positive correlation between a country’s
economic development and the quality of its
road network, a country’s road network should
be constructed in an efficient way in order to
maximize economic and social benefits
(Ighodaro, 2009).
A survey on the state of roads in Nigeria was
carried out by the Central Bank of Nigeria
(CBN) between 11th and 13th December, 2002
along the six geopolitical zones in the country.
The survey indicated that most of the roads were
in a very poor condition and required complete
rehabilitation (Ighodaro, 2009).
Though road usage, construction practices and
maintenance have been reported to be
responsible for road failures (Adegoke and
Agada, 1980), field observation and laboratory
experiments have shown that road failures are
not primarily due to road usage or design
problems alone but can equally arise from
34
inadequate knowledge of the characteristics and
behavior of residual soils as well as the geology.
Hence, it is imperative that these factors are
properly investigated prior to any road
construction. In view of this, this study attempts
to undertake geophysical and geotechnical
investigations of a proposed road linking Akure
and Ipinsa, Southwestern Nigeria with the aim
of investigating the stability of the foundation
within the study area. The proposed road is a
1.03 km stretch of land, linking Akure to Ipinsa,
southwestern Nigeria (Figure 1). It is underlain
by the Precambrian Basement Complex of
southwestern Nigeria (Rahaman, 1988),
comprising of two major petrologic units namely
biotite granite and migmatite gneiss (Figure 2).
The biotite granite essentially covers the major
part of the study area, occurring as a flat-lying
shallow rock mass in most places. The
migmatite gneiss however, is observed to occur
within a small section of the area in the northern
part (Figure 2). This lithologic units is
characterized by bands of quartzite that extends
over 500 m. These rock units have extensively
undergone weathering most especially the biotite
granite, where shallow units are observed to
crumble easily during geotechnical sampling.
METHODOLOGY
The method of study engaged for this research
work involves integrated geophysical and
geotechnical methods. Two categories of data
were collected in the study area. These are
geophysical and geotechnical sampling data.
Geophysical Survey
The geophysical data were acquired by adopting
the ground Magnetic, VLF Electromagnetic
profiling and electrical resistivity methods.
Specifically, the Vertical Electrical Sounding
(VES) technique was adopted for the electrical
resistivity method. The magnetic profiling
involves taking magnetic measurements at an
interval of 10 meters along one thousand and
thirty meters (1030 m) traverse established
parallel to the proposed road. Similarly, the
very low frequency electromagnetic method
(VLF-EM) survey was conducted in the area at
an interval of 10 meters. A total of one hundred
and four (104) stations were occupied along the
proposed road using ABEM WADI VLF
receiver. Meanwhile, vertical electrical sounding
was adopted for the electrical resistivity survey
using Schlumberger array. A total of twenty-two
(22) stations were occupied across the study area
at 50 m inter-VES station. The electrode spacing
was varied between 1-65 m. The Ohmega
resistivity meter was used to acquire the field
data and the position of the occupied sounding
stations in Universal Traverse Mercator (UTM)
was recorded using the GARMIN ‘12 channel
personnel navigation Geographic Positioning
System (GPS) unit.
Geotechnical Investigation
Nine soil samples were collected from the study
for analysis in the laboratory based on the
interpretation of the VES results. The analyses
carried out on the samples include natural
moisture content, sieve analysis, atterberg limits,
compaction and California bearing ratio (CBR)
tests.
RESULTS AND DISCUSSION
Magnetic, VLF-EM and Vertical Electrical
Sounding results were obtained from the study
area. There is high level of correlation among
the subsurface models depicted by individual
methods with regards to the basement
topography, structural disposition and inferred
overburden materials. The magnetic subsurface
model depicts that the basement topography is
undulating in nature, recording a maximum
depth to bedrock of 13 m and subtly
characterized by ridges and depressions. This is
equally reflected on the geo-electric section
which puts the maximum depth to bedrock at
15.1 m. The inconsistencies in depth to bedrock
observed between the methods in certain places
along the section could be noted to be due to the
fact that both methods sense the basement
differently by being sensitive to different
properties of the bedrock. Similarly, structural
disposition of the subsurface modeled by the
three methods show good correlations. The
suspected fault/fractures depicted by the
geomagnetic section at about 150, 220, 400, 520
and 800 m respectively can be compared to the
geometry of linear features delineated on the K-
H pseudo-section at about the same locations.
The same structures could also be related with
partly weathered/fractured delineated on the
geo-electric section most especially beneath
VES 3 and 17 (Figure 3). These structures are
35
potential weak zones that are capable of
compromising the stability of the proposed
pavement structure. Furthermore, the clayey
nature of the overburden could be correlated
with the conductors that pervade through the K-
H pseudo-section. This correlation could equally
be more corroborated by the fact that the
geotechnical results reflect that most of the soil
samples investigated are clayey materials and
thus are weak engineering materials. However,
samples 1, 2 and 4 which reflects fairly good
subgrade materials can be correlated with the
resistivity values (generally > 90 Ωm) of the
topsoil of the associated VES stations (VESs 21,
16 and 14 respectively). This follows that the
topsoil resistivity values of the associated VES
stations of the net soil samples are less than 80
Ωm, suggesting clayey materials which in turn
corroborate the geotechnical results. However,
the integration of the results from geophysical
and geotechnical investigations has enabled the
development of the road failure vulnerability
map for the investigated road. The road
segments are categorized into three zones of
vulnerability to failure. These zones are high,
moderate and low vulnerability zones (Figure 4).
It is estimated that about 60 % of the road
segments is rated to be of moderate vulnerability
while 40% and 10% of the segments are rated to
be of high and low vulnerability respectively.
36
CONCLUSION
Geotechnical and geophysical investigations
involving Magnetic, Very Low Frequency
Electromagnetic (VLF-EM) and Electrical
Resistivity methods have been carried out along
Akure-Ipinsa road southwestern Nigeria in order
to investigate the competence of the proposed
road for pavement stability. Synthesis of the
results demonstrates that the there is a good
correlation among the subsurface models
depicted by the three geophysical methods in
terms of the basement topography, structural
disposition and the inferred overburden
materials. The geotechnical result equally
corroborates these analyses especially in relation
with the geo-electrical parameters which
demonstrates a good correlation between the
engineering properties of the soil samples
investigated and the subsurface resistivity values
of the associated VES stations. The integration
of the results has allowed the development of the
road failure vulnerability map which classified
the proposed road segments into three zones
failure vulnerability namely high, moderate and
low vulnerability zones. It is estimated that
about 60 % of the road segments is rated to be of
moderate vulnerability while 40% and 10% of
the segments are rated to be of high and low
vulnerability respectively. The results obtained
from this study have established the relevance of
the application of geophysical methods in
engineering site investigation cannot be over-
emphasized. The results further establish that the
results of geophysical investigation can be
dependent and relied upon even when
geotechnical data or other forms of data that
provide an in-situ information about the
subsurface are either absent or not in enough
quantity in a given study area.
REFERENCE
Adegoke-Anthony, W. C. and A. O. Agada
(1980). "Geotechnical Characteristics of
some Residual Soils and their
Implications on Road Design in Nigeria.
Technical Lecture, Lagos, pp: 1-16.".
Agency, N. G. S. (2004). Geological and
Mineral Resources Map of Lagos State,
Nigeria. Published by the Authority of
the Federal Republic of Nigeria.
Ajayi, L. A. (1987). “Thought on Road Failures
in Nigeria. The Nigerian Engineer.
22(1): 10-17."
Ighodaro, C. A. U. (2009). "Transport
Infrastructure and Economic Growth in
Nigeria." Journal of Research in
National Development. Vol. 7 (2).
Mesida, E. A. (1987). " The Relationship
Between the Geology and the Lateritic
Engineering Soils in the Northern
Environs of Akure, Nigeria, Bulletin of
the international Association of
Engineering Geology, No. 35,
pp. 65-69. ."
Momoh, L. O., O. Akintorinwa, et al. (2008).
Geophysical Investigation of
Highway Failure - A Case Study
from the Basement Complex Terrain of
Southwestern Nigeria, Journal of
applied Sciences Research, Vol. 4, No.
6, pp. 637-648,
Oladapo, M. I., M. O. Olorunfemi, et al. (2008).
Geophysical Investigation of Road
Failures in the Basement
Complex Areas of Southwestern
Nigeria. Res, Jour. Appl. Sci. 3(2). 103-
112.
.Rahaman, M. A. (1988). Recent Advances in
the Study of the Basement Complex of
Nigeria. Precambrian Geology of
Nigeria. Kogbe C.A. (ed).
37
MULTI-ELEMENT ASSOCIATION ANALYSIS OF STREAM SEDIMENT GEOCHEMICAL DATA FROM
LAFIAGI AREA, WESTERN NIGERIA
Adisa, A.L. and Adekoya, J.A.
Department of Applied Geology, Federal University of Technology, Akure
Department of Geological Sciences, Osun State University, Osogbo.
Corresponding e-mail: [email protected]
ABSTRACT
This research work is aimed at determining the distribution pattern of twenty-four geochemical elements with a view
to isolating anomalous concentrations of the metals in the drainage system. Sixty-one stream sediment samples were
collected from the stream channels of River Oyi and its tributaries covering an area of approximately three hundred
and fifty square kilometres (350km2).The collected samples were analyzed for twenty- four elements by “Inductively-
Coupled Plasma Mass Spectrometer (ICP-MS)” after the samples had been air-dried and sieved to obtain the minus
80 mesh fraction (<177um). The concentrations of the analyzed elements are presented using both statistical and
spatial analytical methods. Distribution, anomalous and 3D Isograde maps were drawn to show the distribution
patterns of the analyzed elements in the study area. A visual inspection of the geochemical distribution and 3D
Isograde maps reveal that Th,La,U,and Pb show identical distribution. The anomalous distribution map revealed that
two of the reported anomalous values of Th,La,U,and Pb occur at the same sites underlain by fine-grained, quartz-
biotite flaggy gneiss. Cu,Au,Zn, and Ag also exhibit similar geochemical dispersion patterns and their anomalous
concentrations share the same site underlain by biotite and biotite-hornblende granodiorite. R-mode varimax factor
analysis of the log-transformed data produced a four-factor model, which accounted for 90.08% of the data
variability, with the following metal associations: Ga-Fe-Ni-Co-Sc-Mn-Tl-Ba-V-Mo-U-Cu-Zn-Ag-Au-Cd, Pb-La-Sr-
Th-U-Cd, Cu-Zn-Ag-Au-Sb and Bi-Cr These have been interpreted in terms of environmental control, lithology and
potential mineralization. The application of statistical and spatial analytical methods suggests the occurrence of
potential mineralization containing Cu-Zn-Ag-Au and Pb-La-Th-U in the gneisses and pegmatites of the study area.
These zones of mineralization could be subjected to further investigation.
INTRODUCTION
Multi-element analysis has been used by several
authors because it does not only provide more
information than univariate analysis, it gives insights
into the metallogenesis of an area (Harraz et al.,2012).
The Oyi drainage system which lies between latitudes
80 39’ N and 80 50’ N and longitudes 50 00’E and 50
09’E on the 1:100,000 topographic map sheet 203
(Lafiagi) covers an area approximately three hundred
and fifty square kilometres (350km2) and is situated
about 110 km northeast of Ilorin (Fig. 1).The area is
covered by the Precambrian basement complex rocks
and the Cretaceous sandstone of Bida basin. The
basement rocks underlying the study area are as shown
in the geological map of Kwara state (Fig. 2).
The aim of this paper is to determine the distribution
pattern of the analyzed geochemical elements with a
view to isolating anomalous concentrations of the
metals in the drainage system.
40
40
‘ 50
50
60
60
‘8
0 80
90 9
0
100
100
STATE
BOUNDARY
S T U D Y
AREA
TOWNS
L E G E N D
KWARA STATE
0 5 0 1 0 0
K i l o m e t r e
N
N
N
E E E
EEE
Internationaboundary
l
N
60
SF
SU
LEGEND
Sample Point
OGp
OGp
Famole
OlogomoBankole
River OyiNSS
OGd
KILOMETRES
8 39 No 1
5 00 Eo 1
8 39 No 1
5 09 Eo 1
8 50 No 1
5 00 Eo 1
5 09 Eo 1
8 50 No 1
Geological boundary inferred
Rivers and Streams
Nupe SandstoneNSS
Fracture/Fault inferred
SFSF
Undifferentiated Schist
Porphyritic Granite
Fine-grained flaggyquartz biotite gneiss
Biotite and biotite hornblende granodiorite
SU
OGp
OGd
SF
38
Figure 1: Map of Kwara state showing the study area. Fig. 2: Geological map of the study area showing
the sample locations.
METHODOLOGY
Sixty-one stream sediment samples which were evenly
spaced over the study area were collected from River
Oyi and its tributaries at sampling interval that varied
between 1.5 and 2.0 km using 1:100,000 topographic
map sheet 203 (Lafiagi sheet).
The samples were sieved, in the laboratory, to obtain
the minus 80-mesh (about 177um) fraction after they
had been air-dried and disaggregated. 0.5g of the
sieved samples were then analyzed for Ag, As, Au, Ba,
Bi, Cd, Co, Cr, Cu, Fe, Ga, La, Mn, Mo, Ni, Pb, Sb,
Sc, Sr, Th, Tl, U, V and Zn, using inductively-Coupled
Plasma Mass Spectrometer (ICP-MS).
RESULTS AND DISCUSSION
The analytical results were used to plot histograms and
curves (Figs. 3) and the threshold value for the
elements were determined using the formula “mean (x)
plus two standard deviation (s) (i.e., x+2s) (Hawkes
and Webbs, 1962). A critical study of these frequency
plots revealed that twenty out of twenty-four elements
viz:Ag,As,Au,Ba,Bi,Cd,Cu,Ga,La,Mn,Mo,Ni,Pb,Sb,Sc
,Sr,Th,Tl,U,and Zn are positively skewed and are log-
normally distributed (Ahrens’, 1954). The remaining
elements show approximately normal distribution.
However, eight of the log-normally distributed
elements, i.e. Cu, Ag, Bi, La, U, Th, Sr and Cd showed
strong positive skewness while others are less skewed
after the raw data were log-transformed. All the log-
transformed histograms showed a unimodal
distribution except Au, Co, Cr, Ga, Sb, Sr, V and Tl
which showed bimodal distribution and Ba, Mn, and
Pb which revealed multimodal distribution. The
variation in the frequency distribution revealed the
inhomogeneous nature of the distribution of the
elements in the stream sediments of the study area
(Chapman, 1976). A visual inspection of the
anomalous distribution patterns shows that the
anomalous values of Fe are found in the central and
northwestern parts of the study area underlain by
porphyritic granite and flaggy gneiss. These
anomalous sites also contain anomalous Ni, Tl, Ga, V
and Zn values. These elements are also positively
correlated with Fe. The concentrations of these
elements were found to be high, when their mean
concentrations were compared to their average
abundances in geological materials. This probably
indicates the scavenging action of Fe-oxides on these
elements.
The distribution patterns for Th,La,Pb,and U (Fig. 5)
are also strikingly similar as two of the reported
anomalous values of the elements are from the same
sites in the northwestern part of the study area
underlain by fine-grained flaggy quartz-biotite gneiss.
When the mean concentrations of these elements were
compared to their average abundances in geological
materials, the concentrations were found to be high.
Other
Cu content (ppm)
50.0
47.5
45.0
42.5
40.0
37.5
35.0
32.5
30.0
27.5
25.0
22.5
20.0
17.5
15.0
12.5
10.0
7.5
5.0
2.5
Fre
qu
en
cy
16
14
12
10
8
6
4
2
0
Std. Dev = 8.60
Mean = 11.2
N = 61.00
Ga content (ppm)
5.004.504.003.503.002.502.001.501.00.50
Fre
qu
ecy
20
10
0
Std. Dev = 1.08
Mean = 1.92
N = 61.00
39
Cu content (log ppm)
1.63
1.50
1.38
1.25
1.13
1.00
.88
.75
.63
.50
.38
Fre
qu
en
cy
8
6
4
2
0
Std. Dev = .28
Mean = .96
N = 61.00
Ga content (log ppm)
.75.63.50.38.25.130.00-.13-.25
Fre
qu
en
cy
14
12
10
8
6
4
2
0
Std. Dev = .25
Mean = .22
N = 61.00
Figure 3: Frequency distribution of raw and logarithmically transformed data on some elements in the stream
sediment of the study area.
N
60
SF
SU
LEGEND
OGp
OGp
Famole
Ologomo
River OyiNSS
OGd
A u (> 1 .4 p p b )
C u (> 2 8 .4 1 p p m )
Zn (> 4 4 .5 2 p p m )A g (> 1 2 .0 p p b )
S b (> 0 .0 6 p p m )
As (>0.62ppm)
KILOMETRES
8 39 No 1
5 00 Eo 1
8 39 No 1
5 09 Eo 1
8 50 No 1
5 00 Eo 1
5 09 Eo 1
8 50 No 1
Geological boundary inferred
Rivers and Streams
Nupe SandstoneNSS
Fracture/Fault inferred
SFSF
Undifferentiated Schist
Porphyritic Granite
Fine-grained flaggyquartz biotite gneiss
Biotite and biotite hornblende granodiorite
SU
OGp
OGd
SF
N
60
SF
SU
LEGEND
Th (> 56.49ppm)La (> 61.53ppm)U (> 5.4ppm)
Pb (> 16.32ppm)C d (> 0.36ppm)
OGp
OGp
Famole
OlogomoBankole
River OyiNSS
OGd
KILOMETRES
8 39 No 1
5 00 Eo 1
8 39 No 1
5 09 Eo 1
8 50 No 1
5 00 Eo 1
5 09 Eo 1
8 50 No 1
Geological boundary inferred
Rivers and Streams
Nupe SandstoneNSS
Fracture/Fault inferred
SFSF
Undifferentiated Schist
Porphyritic Granite
Fine-grained flaggyquartz biotite gneiss
Biotite and biotite hornblende granodiorite
SU
OGp
OGd
SF
Fig. 4: Location point symbol map showing sites Fig. 5: Location point symbol map showing sites
of anomalous Au, Cu, Zn, Ag,Sb and As concentrations. of anomalous Th, La, U, Pb and Cd concentrations.
40
elements with similar distribution patterns are
Cu, Au, Zn, Ag and Sb (Fig. 4). The reported
anomalous values of Cu occur in the northern
and the south eastern (north of Ologomo) parts
of the study area. One of these anomalous sites
(north of Ologomo) also contains anomalous Ag,
Au, Sb and Zn values and is underlain by biotite
and biotite - hornblende granodiorite. All of
these elements also correlate positively with Cu.
The other anomalous site of copper lies near
sites of human activities. These anomalies are,
therefore, probably related to mineralization and
human pollution.
The log-transformed values were also analyzed
by means of PCA with varimax rotation. A four
factor models with eigen-value greater than 1.0,
accounting for 90.08% of the data variability
was considered appropriate. The factors are as
follows
Factor 1 (Ga-Fe-Ni-Co-Sc-Mn-Tl-Ba-V-Mo-
U-Zn-Cu-Ag-Au-Cd):
Factor 2: ( Pb-La-Sr-Th-U-Cd)
Factor 3: (Cu-Zn-Ag-Au-Sb)
Factor 4: (Bi - Cr).
CONCLUSION
In conclusion, the distribution of metallic
elements in the study area can be considered as a
function of a number of factors, such as
lithology, mineralization and environmental.
There is the possibility of occurrence of Au
mineralization in the form of Au-bearing quartz
veins with associated sulphides in the rocks of
the study area, most probably gneiss. Possible
Th-U-La mineralization in the area is also
probably hosted by pegmatite. The influence of
Fe-and Mn-oxides is obvious as the occurrence
of elements like Ba, Co, Ni, Ga etc is due to the
strong scavenging effects of these oxides on
these elements. Furthermore, some fields in the
study area are cultivated. Therefore,
anthropogenic activities cannot be ruled out as a
contributor to some of the anomalies.
References
Ahrens, L. H. (1954): Lognormal distribution of
elements. Geochimica et Cosmochimica Acta,
Vol. 5, No.2, p 29-73.
Harraz, H.Z., Hamdy, M.M. and El-Mamoney.
(2012). Multi-element association analysis of
stream sediment geochemistry data for
predicting gold deposits in Barramiya gold mine,
Eastern Desert, Egypt. Journal of African Earth
Sciences, 68,1-14.
Hawkes, H. E. And Webb, J. S. (1962):
Geochemistry in Mineral Exploration. Harper
and Row. New York, and John Weatherhill, Inc.,
Tokyo, 415pp.
Chapman, R.P. (1978): Evolution of some
statistical methods of interpreting multi-element
geochemical drainage data from New
Brunswick. Journal Mathematical Geology, Vol.
10, p 195-224.
Lecomte, P. and Sondag, F.(1980): Regional
geochemical reconnaissance in the Belgian
Ardennes: Secondary dispersion patterns in
stream sediments. Mineralium Deposita. Vol.
15, p 47-60.
41
GEOLOGICAL AND GEOTECHNICAL INVESTIGATIONS OF FAILED PORTIONS ALONG
IKERE/IGBARA ODO ROAD, SOUTHWESTERN NIGERIA.
A.B. Aluko and A.Y.B. Anifowose
Department of Applied Geology, Federal University of Technology, Akure. Email:
Department of Remote Sensing and GIS, Federal University of Technology, Akure. Email:
ABSTRACT
The Ikere-Igbara Odo road is a major link between the agricultural hinterland and urban cities of Ikere
and Ado Ekiti, southwestern Nigeria. Geological mapping of the road alignment showed three dominant
rock types: biotite granite, biotite-hornblende granite and quartzite. Sixteen disturbed soil samples
derived from these rocks were subjected to geotechnical and clay mineral analyses. Results indicated that
the natural moisture content of the soils ranged between 7.64 and 41.18%, the liquid limit between 18.4
and 53.5%, the plastic limit between 12.1and 43.6% and the plasticity index between 3.4 and 29.2%. CBR
ranged between 14 and 63% while the compaction characteristics of the soil indicated a maximum dry
density between 1622kg/m3 and 2098kg/m3 at optimum moisture content between 13 and 22%. It was
observed that the presence of montmorillonite is a major cause of road failure in the study area.
Keywords: Clay minerals, Geotechnics, Petrography, Road failure, Soil classification
INTRODUCTION
Road transport has remained an index for
measuring the degree of development in most
countries. Unfortunately many of the roads in
Nigeria fail shortly after construction, with an
attendant massive cost of rehabilitation and
reconstruction. Previous workers have
established that pavement failure is a common
phenomenon in areas dominated by tropical
weather conditions (Abynayaka, 1977;
Anifowose, 1989; Jegede, 2000). Studies have
also shown that road failures are not primarily
due to usage and design/construction problems
alone but as a result of inadequate knowledge of
the behaviour of residual soils and the influence
of geology (Adeyemi, 1994; Akpokodje, 1986;
Idowu et al., 2010). The most common types of
clay minerals derived from the weathering or
alteration of feldspathic minerals in rocks are
kaolinite, illite, montmorillonite and halloysite.
The road alignment is about 20km long and runs
roughly east-west, linking Igbara Odo to Ikere
Ekiti in the southern part of Ekiti State,
southwestern Nigeria The general topography of
the study area is hilly and characterised by
outcrops of varying heights and extents. The
study area is underlain by rock types which
include charnockite, quartzite and granite. The
charnockite is located some kilometres to the
north of the road alignment while the quartzite
cuts across the road in some areas (Figure 1).
The granites comprise coarse porphyritic biotite
and biotite-hornblende granites and medium to
coarse grained biotite-granite located to the west
and south of the study area and are also exposed
as road cuts.
42
Figure 1: Geological map of the study area (Adapted from Dempster, 1966)
Figure 2: Sampling points along the road alignment
The following geotechnical tests were carried out on soil samples collected from the study area: Moisture content determination, Sieve analysis, Atterberg limits, Compaction, California Bearing Ratio (CBR),
Figure 3: Ruts and Potholes on the failed road filled with water
43
S/N DESCRIPTION
Colour
Natural
state of
soil
Condition of Area
L1 Reddish brown Dry “Unfailed” zone
L2 Reddish brown Dry Transported
material
L3 Darkish brown Dry Cracks, Mud cracks
L4 Brownish Wet
L5 Darkish brown Wet Stable “unfailed”
portion
L6 Greyish Wet Fairly stable, close
to river
L7 Greyish Wet Fairly stable
L8 Yellowish brown Damp River close by,
failed portion
L9 Dark brown Damp Cracks, potholes
L10 Dark greyish Dry Mud cracks in
rutted area
L11 Dark brown Water
logged
Muddy water in
rutted portion
L12 Darkish brown Damp Crocodile cracks
L13 Light brown Dry
L14 Whitish Dry Quartzite
L15 Reddish brown Damp
L16 Whitish Dry Crocodile cracks,
quartzite quarry
site, river close by
44
METHODOLOGY
Sixteen disturbed soil samples were collected
from test pits dug to a depth of 1meter and a
minimum of 150meters apart along the road
shoulder with attention paid to the various points
of intense failure (Figure 2). Some samples were
also taken along the stable/yet-to-fail portion for
the purpose of comparison.
Specific gravity, and clay mineral identification.
The standard procedures for carrying out these
tests were followed (Lambe and Whitman, 1969;
Bowles, 1981).
For this study, the method of clay mineral
identification was based on the work of
Skempton (1953) using a chart in which
plasticity index is plotted against liquid limit to
obtain the type of clay mineral that makes up a
soil sample.
Site Visits: Site visits were carried out in
October and mid-November. Many of the failed
portions were either still filled with water or
damp (Figure 3) and the rivers were flowing at a
high velocity, while the latter visits were in the
dry season when the rutted portions and potholes
had dried up and could be better observed.
RESULTS AND DISCUSSION
Two rock types were identified within the study
area namely granite and quartzite. The study
area is characterized by limited numbers of
outcrop with the available major ones been
slightly weathered, however, measurement were
taken from the available ones. Photomicrographs
were taken using the objective of the x10 and
x40 magnifications on the petrological
microscope. Thin section study of the samples of
porphyritic granite shows the presence of
plagioclase feldspars, quartz, and biotite (Plate
3.1 and 3.2).
Q= Quartz, F= Feldspar, B =Biotite
Plate 3.1. Photomicrograph of Porphyritic Granite in transmitted light showing quartz,feldspar and biotite
minerals (magnification x 40).
SOIL CONSTITUENTS AND CLASSIFICATION
With the aid of the Skempton’s activity chart i.e. plotting the liquid limit against plasticity index (Figure
4), the types of clay minerals in the different soil samples taken from the study area were determined and
plotted on the chart as follows:
45
Figure 4: Activity of the various clays from the study area (After Skempton, 1953)
The presence of Illite in some of the samples
could be as a result of the composition of the
granites which have been confirmed to contain
feldspar and biotite. The formation of the
Montmorillonite could be as a result of the
retention of water during weathering especially
at the peak of the rainy season, thereby reducing
the chance of leaching which promotes the
retention of magnesium and calcium ions. This
could further be buttressed by the fact that the
samples in which montmorillonite was observed,
were quite close to river channels and these may
have been the water source. The kaolinite as
earlier explained was introduced into the study
area through the laterite used in the construction
of the road which was brought in from outside
the area.
CONCLUSIONS
From this study, it is concluded that detailed
geological studies were not carried out before
the route was selected. This is evident by the
construction of the road along a fault zone
without adequate preparation for possible failure
as well as the use of laterite whose properties
were not known.
The study has also brought to the fore the
channel overflow made evident by the
waterlogged areas near the river channels hence
the need for wider bridges which should be
constructed to allow for continuous flow of the
pre-existing river channels.
The formation of montmorillonite from the
parent rock is one of the major problems in the
area, and this is promoted and sustained by the
presence of a zone of water influx into the area
due to slight depression of the area. The areas
with little or no problems are synonymous with
where Illite was found to be the major clay
constituent of the soil. They are also areas that
are slightly elevated.
REFERENCES
Anifowose, A.Y.B. (1989). The performance of
some soils under stabilization in Ondo
State, Nigeria. Bulletin of International
Association of Engineering Geology, 40, pp. 79-
83.
Idowu, S.O., Adeyemi, G.O. and Dada, S.S.
(2010): Permeability and Grain-Size
Characteristics of Sagamu and Ibadan Toll-Gate
Lateritic Soils in Southwestern Nigeria. Journal
of Environmental Sciences and Resource
Management, Vol. 2, pp 86-94.
Jegede, G. (2000): Effect of Soil Properties on
Pavement Failure along the F209 Highway at
Ado-Ekiti, Southwestern Nigeria. Journal of
Construction and Building Materials, Vol. 14,
pp. 311- 315.
Lambe, T.W. and Whitman, R.V. (1969): Soil
Mechanics. John Wiley and Sons, Inc., New
York.
Skempton, A. W. (1953): The Colloidal
“Activity” of Clays. Proceedings of the 3rd
International Conference of Soil Mechanics and
Foundation Engineering; Switzerland, Vol. 1,
pp. 57-60.
L1
L2
L12
L4
L5
L6
L7
L8
L9
L10
L11
L3
L13
L14
L15
L160
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100
Pla
stic
ity
In
dex
, PI
(%)
Liquid Limit, LL (%)
46
A PRELIMINARY ASSESSMENT FOR GROUNDWATER IN A PART OF NORTH
CENTRAL NIGERIA USING LANDSAT ETM+
A.Y.B. Anifowose, O.O. Aladejana
Department of Remote Sensing & GIS, Federal University of Technology, P.M.B. 704,
Akure, Nigeria.
Email: [email protected]; [email protected]
ABSTRACT
In a basement environment where groundwater is restricted to secondary permeability, structural
analysis using remote sensing is a reliable and cheap method for the start-up process for
groundwater exploration. In this study, remote sensing and GIS technology were employed as a
major tool for groundwater prospecting in a part of North Central Nigeria; an area prone to water
scarcity for more than half of every year. The geological map of the study area, Landsat7 ETM+, and
Shuttle Radar Topographic Mission (SRTM) imageries covering the area were employed in this study.
Edge enhancements and directional filtering were carried out to enhance the visibility of lineaments
on the Landsat imagery. To eliminate bias and subjectivity, Normalized Difference Vegetation Index
(NDVI) and Digital Elevation Model (DEM) of the study area were processed for further lineament
detection.
Results indicate that lineaments extracted from the Landsat imagery were in agreement with those
obtained from the DEM. Those obtained from the NDVI analysis were also in agreement, except for a
number of entirely new lineaments detected. This showed the importance of healthy vegetation
aligned in a linear or curvilinear way as a major guide to detecting subsurface water-bearing zones
that are not visible on the surface. Results also show that the dominant lineaments trend along the
NE-SW direction. The northwest and central parts of the study area have relatively high lineament
density, while the southern part has very low lineament density. These areas with high lineament
density values are more feasible zones for groundwater prospecting.
Keywords: Basement complex, Edge enhancement, Groundwater exploration, Landsat ETM+, NDVI
INTRODUCTION
Faults, joints, bedding planes and foliations are discontinuous structural trends that can be detected
in various ways for several environmental applications. Such discontinuous structural trends can be
detected not only by carrying out ground mapping but also using remotely sensed data such as
conventional aerial photographs and satellite imagery. Remote sensing products ranging from aerial
photographs and different forms of satellite imageries have proved to be efficient in structural
geology; the structures obtained from the field very much correlate with those obtained from
satellite imagery, most of the time with perfect structural manifestations (Morelli and Piana 2006).
Historically, lineament identification and extraction was performed using aerial photographs,
stereopairs, and transparencies on light tables (Gupta 2003), but in recent times, studies have been
conducted using medium-resolution sensors (Drury and Andrews 2002, Lee and Moon 2002,
Ricchetti 2002, Inzana et al. 2003, Hung et al. 2005, Arellano-Baezo et al. 2006, Khan and Glenn
47
2006, Meijerink et al. 2007, Sander 2007). The study area spans over about 22,000 km2, between
Latitudes 09°29’8.92’’N to 10°48’19.081’’N, and Longitudes 06°23’36.865’’E to 07°46’36.354’’E
(Figure 1). The underlying lithology consists of migmatites, gneisses, schists and other
metasedimentary rocks, and granitoids (Oyawoye 1972; Rahaman 1988; Dada 1989) as shown in Fig.
2. According to Rahaman (1988) the most dominant rock body in the study area is the Older Granites
which are the most obvious manifestations of the Pan African orogeny, and attempts to classify with
respect to timing during an orogenic event are valid over only short distances. They are believed to
be pre-, syn- and post-tectonic rocks which cut both the migmatite-gneiss-quartzite complex and the
schist belts. They widely range in age (750–450 Ma) and composition, from tonalites and diorites
through granodiorites to true granites and syenites, which represent a varied and long-lasting
magmatic cycle associated with the Pan African orogeny (Obaje, 2009). In the study area, paucity of
insitu data on groundwater is a major challenge and this has resulted in poor knowledge of the
hydro-physical characteristics of basement aquifers (Olorunfemi et al. 1999). This is the major cause
of numerous failed/abortive hand dug wells and boreholes in the area, resulting in water scarcity. In
view of these problems, this study focuses on developing a start-up methodology for groundwater
exploration using remote sensing data (Landsat ETM+) and GIS techniques
METHODOLOGY
The Landsat ETM+ of Path 189 and Row 053, acquired in 2001 over the study area was obtained from
Global Land Cover Facility (GLCF) website. The geologic map covering the study area was scanned,
georeferenced and digitized to obtain lithologic information. A mosaic of four 90-m SRTM DEM was
obtained from the United States Geological Survey (USGS). Data gaps in the SRTM DEM were filled to
produce a complete DEM coverage. All images were georeferenced to WGS 1984 and UTM Zone
32N. A sub-scene covering the study area was created from the full scene Landsat-7 ETM+ image. It
was subset to Latitudes 09°29’8.92’’N to 10°48’19.08’’N, and Longitudes 06°23’36.87’’E to
07°46’36.35’’E. Because of the large variations in the spectral response as shown by Band 7, image
histogram equalization was carried out with 10% stretching interval. The stretched image was then
filtered in order to emphasize the linear features (e.g., edges) with high spatial frequency.
Directional filters of 3x3 kernels were carried out in the North-South, East-West, and Northwest-
Southeast directions using convolution method in order to enhance linear trends along those
orientations
Fig. 1 Location map of the study area
48
Fig. 2 Geological map of the study area
Key: D-Dolerite, GG-Granite gneiss, M-Migmatite, MG-Migmatite gneiss, My-Mylonites, OGd-
Biotite&biotite hornblende granite, OGe-Medium to coarse grained biotic granite, OGf-Fine grained
leucocratic granites, OGh-Coarse porphyritic hornblende granite, OGp-Coarse grained porphyritic
biotite&biotite hornblende granite, OGu-Undifferentiated granite, migmatite and granite, migmatite,
porphyroblastic, Qzt-Quartzites, silicified shear zone, quartz vein, Su-Undifferentiated schist,
including gneiss, fine grained flaggy quartzites, amy-myanites with intercalated amphibolites, as-
amphibolite, b-GH-Biotite hornblende gneiss, ms-Pelitic schist
To eliminate bias and subjectivity, the DEM and NDVI of the study area were processed for detection
of lineaments. DEMs have shown to be useful for detecting lineaments because they can eliminate
bias caused by inherent East-West sun illumination (Henderson et al. 1996; Yun and Moon 2001). A 3
x 3 filterin the x-direction was applied to enhance the visibility of linear features occurring in the east
and west as a result of changes occurring in that direction. It was also repeated in the y-direction for
those occurring in the North and South. Inherent in this image were geomorphic lineaments,
especially those occurring along fault-controlled cliffs. These lineaments were identified, and
manually digitized. The NDVI which is based on the theory of a difference in reflectance in the near
infrared (NIR) and red bands of the electromagnetic spectrum has its roots in this application. Band 4
(NIR) and Band 3 (Red) were used for this procedure. Those with denser and more active vegetations
aligned in linear to curvilinear patterns were extracted appropriately by digitizing.
RESULTS AND DISCUSSION
The lineaments obtained from the DEM analysis of the study area were the same obtained from the
analysis of the Landsat imagery of the area. This further enunciates the fact that tonal changes and
relief differences are major characteristics enhance the visibility of linear structural features in these
imageries. Those obtained from the NDVI analysis were also the same with those previously
obtained except in areas of thick vegetation covers where newer lineaments were obtained. The
NDVI showed areas of healthy and flourishing vegetation. In this situation, this flourishing vegetation
49
was aligned in both linear and curvilinear directions (Bruning 2008). This showed the presence of
shallow underground water sources in form of lineaments. The lineament map of the study area
(Figure 3) depicts the structural trends obtained from the remote sensing analysis.
Fig. 3 Lineament map of the study area
A total of 1570 lineaments were mapped; they indicate three distinct lineament directions as shown
in the rose diagrams (Figure 4a&b). Spatial analysis of the lineaments indicates lineament densities
ranging between 1 and 12 per unit area (Figure 5).
Classification of the lineaments for their direction was done based on a 10ᵒ interval. From the rose
diagram obtained from the plotted lineaments, the dominant lineament direction was found to
occur in the 0ᵒ-10ᵒ direction.
A total of 192 lineaments occur in this interval, accounting for about 15% of the total mapped
lineaments. The second dominant direction was 10ᵒ-20ᵒ with a total of 188 lineaments, and
accounting for about 14% of the total lineaments. The third direction occurred in the 20ᵒ-30ᵒ
orientation, a total of 155 lineaments accounting for about 12% of the total lineaments. High
lineament frequencies also found to occur in Kugu, Alawa, Gadna and Masuka. In these areas, the
basement rocks outcrop or are close to the surface (i.e. areas with thin overburden) whereas in
other parts of the study area, low lineament frequencies which are characteristic of areas with
deeply buried basement rocks are observed (Edet et al. 1994).Therefore, regions with high
lineament densities tend to favour high groundwater availability (Mogaji et al. 2011).
50
Fig 4 Lineament analyses: a. Frequency based b. length based
Fig 5 Lineament density map of the study area
CONCLUSIONS
The result of the analysed lineaments shows that the lineaments/fractures within the study area are
aligned mainly in the NNE-SSW directions, as obtained from the satellite imagery of the study area.
As high lineament density areas have greater potential for groundwater prospecting, it is suggested
that further geophysical investigation of the zones of high lineament density of the study area for its
groundwater potential will prove to be very useful and efficient, providing a quantitative analysis of
this resource.
This study can be described as a major tool required for proper water resources management
towards sustainable development and water management in Nigeria. In view of this it is suggested
that other contributory factor to regional groundwater accumulation be considered to further
increase the accuracy of this study. Most important of these is that the suggested zones of high
groundwater accumulation should be combed with detailed geophysical investigation and mapping
for proper quantitative evaluation of the volume of groundwater available in these zones.
REFERENCES
51
Edet, A.E, Teme, S.C, Okereke, C.S, Esu, E.O (1994) Lineament analysis for groundwater exploration
in Precambrian Oban massif and Obudu Plateau, SE Nigeria. Journal of Mining and Geology,
Vol.30 No.1, pp. 87-95.
Obaje, N.G (2009) Geology and mineral resources of Nigeria. Springer Dordrecht, Heidelberg, 221p.
Olorunfemi, M.O, Ojo, J.S, Akintunde, O.M (1999) Hydrogeophysical evaluation of the groundwater
potential of Akure Area, Southwestern Nigeria. Journal of Mining and Geology. Vol. 35(2),
Pp. 207-228.
Sander, P. (2007) Lineaments in groundwater exploration: a review of applications and limitations.
Hydrogeology Journal, Vol. 15, pp. 71-74.
52
ADVERSE EFFECT OF COLD WEATHER ON UPPER RESPIRATORY DISEASES; A
CASE OF CHILDREN IN THE RESIDENCE OF JOSEPH AYO BABALOLA UNIVERSITY,
IKEJI-ARAKEJI
Babatola E.B., Adeyemi E.O. & Esan A.L
Department of Geography, Joseph Ayo Babalola University, P.M.B. 5006, Ikeji-Arakeji, Osun
State, Nigeria
Corresponding author: [email protected]
ABSTRACT
This research explored the effects of cold weather on the health of children residing in the Quarter of
Joseph Ayo Babalola University Campus, Considering the spread of illness among the children in the
months of June and July, and the prevailing weather in that particular period. This research was
carried out using primary and secondary data. Data were collected on the condition of atmosphere
and its direct effect on 30 children of the University Staff (Physiologic comfort) as well as indirect
effect (Lessen body immunity).The data for the condition of atmosphere were collected by measuring
the air temperature i.e. average minimum and maximum indoor and outdoor temperature over the
interval of six hours; 6:00 am, 12:00 noon, 6:00 pm, and 12:00 pm were taken, Monthly temperature
for a year 2012 was also collected from Joseph Ayo Babalola University Weather Station to
corroborate the primary data, wind speed was also recorded for the months of June and July. Also,
questionnaire and interview were used to elicit information about the condition of weather and its
effects on children’s health as well as cold related illness afflicting them during the period and their
body resistance to the illness. Data on the respiratory diseases in children for about three years were
collected from the Clinic of the University. Analyses were carried out using wind chill index to
determine the degree of coolness of the weather. The study concluded that there is direct relationship
between the cold weather and the health of children. It also reveals that the degree of exposure to
cold weather determines the rate of symptoms of cold stress manifested in children, and that the
exposure could be reduced by body insulators such as clothing materials, food, as well as body
exercise which can help to maintain the physiologic comfort during cold weather. This study
concluded that weather is usually cold during the period.
Keywords: Weather, Health, physiologic-comfort, Human-body, Diseases, Immunity
INTRODUCTION
This study reviews the effects of cold
temperatures on human health and mortality
with the study of Keatinge and Donaldson
(2001), who examined the effects of
temperature, wind, rain, humidity and sunshine
during high pollution days in the greater
London area over the period 1976-1995 to
determine what weather and/or pollution
factors have the biggest influence on human
mortality. The results of their complex
analysis were truly astounding: "no pollutant
in that analysis, SO2, CO, or smoke, was
associated with a significant (P < 0.05)
increase in mortality." There was, however, a
"large, delayed increase in mortality after low
temperature," which was "specifically
associated with cold and is not due to
associated patterns of wind, rain, humidity, [or
lack of] sunshine." Indeed, cold alone was
found to be responsible for the excess deaths,
although there was a small but "short-of-
statistical-significance" increase in mortality
with smoke, which the authors suggested
might possibly have been due -- if it really
occurred (which is highly questionable) -- to
the effects of PM10 (particulate matter of 10-
micron diameter).
So how does cold kill? According to Keatinge
and Donaldson, "cold causes mortality mainly
from arterial thrombosis and respiratory
disease, attributable in turn to cold-induced
hemoconcentration and hypertension [in the
first case] and respiratory infections [in the
second case]." Such a cause-and-effect
relationship has been demonstrated by Nafstad
et al. (2001), who studied the association
between temperature and daily mortality for
citizens of Oslo, Norway over the period 1990
to 1995. Because Norwegian law requires that
all deaths be examined by a physician, who
diagnoses the cause of death and reports it on
the death certificate, the authors were able to
categorize and examine the effects of
temperature on mortality from (1) respiratory
diseases, (2) cardiovascular diseases and (3)
53
all diseases (excluding deaths caused by
accidents, poisoning, suicide, or other non-
normal causes). The results of Nafstad et al.'s
analysis showed that the average daily number
of deaths in all three categories was higher in
winter (October-March) than in summer
(April-September). For respiratory diseases,
winter deaths were 47% more numerous than
summer deaths; while for cardiovascular
diseases and the all-disease category, winter
deaths were 15% more numerous than summer
deaths. Based on these findings the authors
conclude that "a milder climate would lead to a
substantial reduction in average daily number
of death.
METHODOLOGY
Data collection for this research were both
primary and secondary; Both indoor and
outdoor air temperature were measured over
the period of 6 hours intervals and the average
minimum and maximum temperature for
hours; 6:00 am, 12:00 noon, 6:00 pm, and
12:00 pm were taken, wind speed was also
recorded for the month of June and July. This
research sampled 30 children randomly
selected across the quarters. Questionnaire
and interview were used to elicit information
about the perception of respondents on the
condition of weather and its effect on the
health of the children. Information about cold
related illness afflicting them during the period
were also collected, and the degree of
exposure and control of the cold weather
which subject their body to respiratory
diseases also elicited. Furthermore, Joseph
Ayo Babalola Clinic was consulted in order to
gather information on issues relating to
respiratory diseases, their causes and the
period that they were recorded most. Analyses
were carried out using wind chill index K0 =
(10.45 +10 √V-V) (33-Td) Where K0 is the
wind chill index in kcal/m hr, V is wind
velocity in m/sec and Td is dry-bulb
temperature in 0C. Percentage and Graph were
also used to analyse the hypotheses of this
research.
LIMITATION OF THE STUDY
In the course of this research, some difficulties
which posed limitation on the accurate
derivation of the result findings of this study
were encountered: First, Human research
always faces the problem of erroneous
attitudes, so this research was not left out in
the response of some people to the
questionnaire where facts that would validate
the result were hidden, or some people
disguise to meet up with all measures against
cold exposure for their children and so on.,
Secondly, Another limitation was that the
medical data collected in the clinic does not
really exhibit the no of children in JABU and
also could not really substantiate the effect of
cold with the number of patient attendance,
because majority of the residents of JABU are
not permanently residing there, they often
travel during the weekend and more so even
children travel for holidays during the cold
period established by this research.
RESULTS
The objective was to determine how cold is the
air during the period of study using both
secondary and primary air temperature data; a
line graph in fig2 of the work represents the
former and double-line graph in fig1 depicts
the latter, wind-chill index (K0) was also used.
Table 1 clearly showed the trend in the air
temperature from 6am to 12 mid night in the
intervals of 6 hours.
The graph in Fig. 1, shows that the average
temperature values for the months of June,
July and August were lower considering the
line in the graph, this was further explained in
Table 2 and Fig. 2 above, show the trend of
coolness of air temperature which get lower
towards the nights and it begins to rise again
as daylight is being approached. The two lines
i.e the Outdoor and Indoor temperatures rise
from 6am, go more higher toward 12noon and
steadily falling from 6pm to 12 midnight
through the whole night while start rising
again as 6am is being approached. This shows
that intense cold begins around evening and
increases through the night to the early
morning, during which many are inflicted by
cold.
Lastly, the Wind Chill Index is used to test the
fact that weather is cold during the periods as
shown by this equation; K0= (10.45+10√V-
V)(33-Td) where K0 is the Wind chill index in
Kcal/m hr, V is wind velocity in m/sec and Td
is the dry bulb temperature in 0C. The
interpretation is usually done using the Simple
and passel sensation scale of the wind chill
index. The value of K0 for JABU residence is
gotten by using the derived wind velocity V =
36m/sec and dry bulb temperature Td = 240C
gotten from the average of values of dry bulb
thermometer records for June, July and August
54
from JABU weather station. Therefore, K0=
(10.45+10√36-36)(33-24) = 780.3Kcal/mhr
Considering the sensation scale the value 800
is cold, so the K0 in JABU residence which is
780.3 is also cold and therefore the low air
temperature during the periods produces cold
weather in June, July and August in the JABU
environment.
Table 3, presents the cold stress
symptoms/illness that afflict the body system
of JABU children residence, cold body
temperature 16(53.3%), even though general
preventive measure of 82.2% was a quality
one, children were still suffering even severely
from some cold stress, Catarrh 73.3%, Cough
66.7%, Cold fever 60%, Cold body
temperature 53.3% and others, showed that
there cannot be absolute avoidance of cold as
in table 4 below.
Table 4 shows the techniques that the residents
of JABU practise to prevent their children
from cold exposure. It is very clear from the
table that the residents to a greater extent
prevent cold in their children, All the
respondents, (100%) practised warm bath,
Warm/Nutritious feeding, Thick/Cover
clothing for their children. And (80%) wore
socks, and (60%) wore gloves for their
children, about (53.3%) engaged their children
in body exercise. All these are quality ways of
preventing human body against cold which can
be said that JABU residents took 82.2%
preventive measures against cold.
Following the above results table 5, the record
of children attendance at the clinic over the
three years depicts clearly, as 2011shows
August having the highest number, followed
by July, then September and thereafter June
and May. In 2012, September has the highest
number, follow by August, October,
November, July, then, June and May, In 2013,
August has the highest number, followed by
June, September, then July. Considering the
total for the three years August has the highest
number of the attendance, followed by
September, July and then June still support the
fact that a factor influences children number in
those months to increase which is most likely
to be cold air.
The graph of JABU children attendance in the
clinic clearly shows that the four lines are
moving upward from June, while August is the
peak. This is undoubtedly a true evidence of
the fact that the period of June, July and
August are actually the time people in the area
suffer from cold fever and as such most likely
that human body could be made susceptible to
illness.
CONCLUSION
This research work has substantiated through
series of fact findings about coldness of air as
Table 1 and fig 1and Table 2 and fig 2 that the
months under study; June, July and August are
actually the coldest in the year, also analysis of
wind chill index used corroborates that the
periods are actually cold.
This research is a practical demonstration that
absolute avoidance of cold is impossible,
according to (Manfred, 2007) once there is
prevalence and persistence of cold weather,
the degree of suffering could only be lessened
by the extent of avoidance through preventive
measures applied by individual. As it was in
JABU residence, the degree of prevention was
very high, but it did not stop children from
suffering from cold.
Finally, this research also ascertained the fact
that cold effect on body immunity made
children to be subjected to illness (Ayoade,
2008). This is evident in Table 3 and fig 3, as
the total number of children attendance in the
clinic for the 3 years 2011, 2012 and 2013
revealed that June, July, August and
September are higher, thereby supporting the
conclusion that children illness corresponds
with the cold period in the area.
REFERENCES
Ayoade, J.O. (2008): Techniques in
Climatology, Stirling-Horden Publisher
Ltd. Ibadan.
Keatinge, W.R. and Donaldson, G.C. 2001.
Mortality related to cold and air
pollution in London after allowance for
effects of associated weather
patterns. Environmental Research 86:
209-216.
Manfred, K. (2009) How the weather affect
your health
55
Fig1: Graph showing indoor and Out-door
temperature at different time of the day in
June-August 2014
Fig 2: Graph showing Mean monthly temp of
JABU, for 2012
Fig3: Graph showing the attendance of JABU
Children in Clinic
56
Table 1: Mean monthly temp of selected time of the day around the JABU quarter in 2014
Table 2: Mean monthly temperature of JABU for 2012
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Temp 25.8 26.8 27.9 26.6 27.1 23.4 24.2 25.3 26.1 27.2 28.5 29.6
Table3: Cold Stress among Children in JABU Residence
Cold
Symptoms/illness
Freq. %
Cold body
temperature
16 53.3
Body Shivering 12 40
Finger bite 8 26.7
Ear bite 6 20
Fore-head bite 6 20
Nose bite 4 13.3
Catarrh 22 73.3
Cough 20 66.7
Head-ache 5 16.7
Breathing
Difficulty
8 26.7
Cold fever 18 60
Malaria fever 10 40
Table 4: Cold Prevention Practises among the Children in JABU Residence during the period
Prevention Techniques Freq. %
Warm Bathing 30 100
Warm/Nutritious Feeding 30 100
Thick/Cover Clothing 30 100
Socks Wearing 24 80
Gloves Wearing 18 60
Body Exercise 16 53.3
Time 6am 12nn 6pm 12mn 6am 12nn 6pm 12mn 6am 12nn 6pm 12mn
June July Aug.
M.Temp
(Indoor)
22.5 26 25.25 21.0 21.25 25.75 24 20.5 21.15 24.25 23.25 20.0
M.Temp
(Outdoor)
21.2 27.5 24.5 20.75 19.2 28 26.75 19.0 18.75 27.25 20.75 18.0
57
STRUCTURAL CHARACTERIZATION OF A SUSPECTED GEMSTONE DEPOSIT FROM
AEROMAGNETIC DATA OF PARTS OF IKARA, NORTHCENTRAL, NIGERIA
Bala B, Lawal K.M, Ahmed, A.L.
Department of Physics, Ahmadu Bello University, Zaria
ABSTRACT
Structural analysis of aeromagnetic map using second vertical derivative and Werner deconvolution
methods over parts of ikara was carried out to highlight and characterize linear features in the survey
area. The study area is part of Nigerian Basement Complex and the rocks typically found within the
Basement Complex include gneisses, migmatites, metasediments Older Granites and metavolcanics.
Boundaries and trend characteristics of magnetic lineaments were highlighted by zero contour of the
second vertical derivative while Werner deconvolution of aeromagnetic data profiles was utilized to
determine depth to magnetic sources. Depth to magnetic sources of aeromagnetic data profiles ranges
from 400m to 500m, while Magnetic susceptibility values range from 6.605x10-4SI unit – 1.694x10-3SI,
Dip angles have values from ranging-171.20 to 133.10 and trend in the NW-SE direction. The study area
is most likely a magneto-tectonic province of fractures filled with minerals such as amethyst and the
dominant NE-SW and NW-SE trends.
Keywords: basement, magnetic, trends.
INTRODUCTION
The magnetic method is widely used to detect
and map subsurface features. The interpretation
of aeromagnetic maps involves interpreting the
basement structures and detailed examination of
structures and lithologic variations in the
sedimentary section. Magnetic basement is an
assemblage of rocks that underlie sedimentary
basins and may also outcrop in places (Onyedim
& Awoyemi, 2006).
Linear features or lineaments can provide
important information on the extension of
deformation zones in the bedrock. The magnetic
susceptibility of rocks is often low in fractured,
altered or porous bedrock due to the destruction
of ferromagnetic minerals (Hans et al., 2006).
Magnetic anomalies arise from secondary
mineralization along fault planes, which are
often revealed on aeromagnetic maps as surface
linear features. Consequent on the relevance of
linear structures aforementioned and most times
geologists are handicapped by lack of exposures
of some geologic features, to prepare an accurate
and detailed geological map for structural
settings and exploration of mineral resources.
Soils, alluvium, bush forests and water bodies
often conceal geologic features (Aina and
Olarewaju, 1991).
In this study; second vertical derivative and
Werner deconvolution methods were utilized to
study magnetic lineaments with emphasis on
their trend and depth to sources. The survey area
is bounded by a longitude range of 80 00’E to
8030’E and latitude range of 110 00’N to
11030’N.The study area is shown in Figure 1.
Ikara area forms part of the Northern Nigerian
Basement Complex and apart from an extensive
superficial cover (McCurry, 1970). The rocks
typically found within the Basement Complex
include gneisses, migmatites, metasediments
Older Granites and metavolcanics.
58
METHODOLOGY
The High Resolution Aeromagnetic (HRAM)
data of Ikara located between 110 00’N - 110 30’N
latitudes and 08000’E - 080 30’E longitudes
covers the study area and its environs. The
HRAM was digitized using SURFER software.
Residual field map (Fig. 2) was extracted from
the total magnetic intensity map by the Least
Squares Method. A low-pass filtering of cut-off
frequency of 2rad/km equivalent 3.14km in
wavelength was applied on the residual
aeromagnetic data to reduce noise in the data
(see Figure 3). In order to get proper alignment
of magnetic boundaries and to sharpen the
anomalies, the second vertical derivative was
applied to the low pass-filtered residual field
map. Contacts/edges between anomalies are
obtained as inflection points by a zero contour of
the second vertical derivative (Figure 4). For
depth to magnetic anomalies sources to be
achieved in this research, Werner deconvolution
method was adopted to study magnetic
lineaments.Three profiles were selected for
Werner analysis (figure 6)
Study area
Figure 2: Residual Magnetic Intensity
Contour Map (Contour Interval is 10nT)
Figure 3: The low-pass filtered residual
magnetic field map of the area of study
(Contour interval is 15nT)
59
RESULTS AND DISCUSSIONS
Noise and any subsurface geologic structure
above 3.14km wavelength were filtered out in
order to get improved and reliable information
from the data in the study area. The contour map
of the low-pass filtered residual data is now
much smoother and shows clearly the
alignments and boundaries of the anomalies (see
Fig.3).
Thus, the second vertical derivative is in effect a
measure of the curvature, i.e., the rate of change
of non- linear magnetic gradients. The zero
magnetic contours of the second vertical
derivative often coincide with the lithologic
boundaries (Blakely, 1995). Other boundaries
trending NE-SW, with minor ones in the NW-
SE directions are also observed (see figure 4).
The Werner deconvolution operator is a sliding
window that moves along a profile and
continually solves for the four unknowns. The
parameterization of that operator consists of (1)
the size of the window, which will influence the
estimated depth of the anomaly; (2) how it
moves on a profile, which controls the number
of generated solutions; and (3) parameters that
exclude the spurious solutions (caused by noise).
Werner deconvolution program has been used
to constrain at depth solutions and the results at
the points of intersection(X, Y and Z) of the
three profiles across the residual field map are
shown in Figure (6).
It can be obtained that the pronounced variation
in magnetic field intensity values occurrs at
about 24km, 30km and 40km for X, Y and Z
respectively along the profiles. The depth values
for all the profiles range from 400m to 500m,
while Magnetic susceptibility values range from
6.605x10-4SI unit – 1.694x10-3SI units while dip
angle have values from-171.20 to 133.10 trending
in the NW-SE direction. Some amethyst quartz
was found around the study area, which seems to
be perpendicular to the direction of the fault
zone. This fracture could be filled with this
mineral.
CONCLUSION
From the interpreted aeromagnetic data in this
research, the fault zone and its surroundings in
Ikara Kaduna State, Nigeria have been
characterized. Significantly, the subsurface
Figure 4: Zero contoured second vertical
derivative of the low-pass filtered residual
magnetic field. The dashed line represents the
suspected structure.
Figure 5: Residual aeromagnetic
anomaly map with selected profiles;
AA’, BB’ and CC’
(Contour interval= 15nT)
60
major structural anomalies of NE-SW and NW-
SE directions have been confirmed, defined and
delineated. The depth values for all the profiles
range from 400m to 500m, while Magnetic
susceptibility values range from 6.605x10-4SI
unit – 1.694x10-3SI units while dip angle have
values from-171.20 to 133.10 trending in the
NW-SE direction. The study area is most likely
a magneto-tectonic province of fractures filled
with minerals such as amethyst.
REFERENCES
Aina, A. and Olarewaju, V. O. (1992).
Geological interpretation of aeromagnetic data
in some parts of northcentral, Nigeria.
Journal of African Earth Sciences, 14(1), 103-
109.
Blakely, R. (1995). Potential Theory in Gravity
& magnetic application,
Cambridge University press,
USA.
Hans, I., Timo, P. and Hans, T. (2006).
Forsmark Site Investigation Ground
Magnetic Survey and Lineament
Interpretation in an area Northwest of
Bolundsfjarden, Swedish Nuclear Fuel,
Stoskholm Sweden.
McCurry, P. (1970). The Geology of the Degree
Sheet 21 (Zaria). M.Sc. Thesis,
Department of Physics, Ahmadu Bello
University, Zaria, Nigeria.
Onyedim, G. C., Awoyemi, M. O., Ariyibi, E.
A., & Arubayi, J. B. (2006). Aeromagnetic
imaging of the basement morphology in
part of the Middle Benue Trough, Nigeria.
Journal ofMiningandGeology,42(2),157-
163.
Figure 6: Werner depth solutions for three (AA’, BB’ and CC’) across a suspected fault on the
aeromagnetic map of the study area.
61
SUBSURFACE STRUCTURAL MAPPING OF THE RUSTENBURG LAYERED SUITE (RLS) OF THE
BUSHVELD IGNEOUS COMPLEX IN SOUTH AFRICA
O.A. Bamisaiye, P.G.Eriksson, J.L. Van Rooy, H.M.Brynard, S. Foya
Applied Geology Department, Federal University of Technology, Akure, Ondo State.
Department of Geology, University of Pretoria, Private Bag X20 Hatfield, Pretoria 0028, South Africa.
Council for Geoscences, Pretoria, South Africa.
Correspondence: O. A. Bamisaiye, Applied Geology Department, Federal University of Technology Akure, Ondo
state Nigeria.
ABSTRACT
The purpose of this study is to generate 3D geological models of the Rustenburg Layered Suite (RLS) using available
borehole log record, field mapping reports and geophysical data in order to constrain its geometry and structural
architecture. Most frequently used data for this type of study are well-logs and seismic data, however for this type of
continous regional scale study, such data are not readily available. Geospatial analysis of borehole log data with
good spatial distribution serves as an exceptional alternative. The result showed perfect conformity with previous field
studies and geophysical investigation. It also revealed the structures and geometry of the stratigraphic units that were
inadequately constrained prior to this study. The study provides new insights into the structure and kinematic
evolution of the RLS leading to better structural interpretation.
KEY WORDS: 3-dimension; visualization; 3D-models;Rustenburg Layered Suite; geometry;Bushveld Complex.
INTRODUCTION
The Bushveld Complex (BC) of South Africa with
an area extent of 65,000km2 (Cawthorn and Webb,
2001), consist of laterally continuous RLS which
holds the world’s largest deposit of Platinum group
metals (Vermaak, 1995; Barnes et. al. 2004;
Naldrett, 2009). Despite the increase in knowledge,
researchers have not been able to unravel the
subsurface geometry of the entire area since field
based studies could not adequately describe the
geometry due to incompleteness of outcrop
exposures and limited availability of seismic data.
Knowledge of the subsurface geometry and
structure is important for a better understanding of
the emplacement, layering, depth and structural
relationship between the various limbs and
provision of information that will be useful in
addressing some geological problems. This may
also increase the knowledge about the distribution
of the mineral bearing zones. This research focused
on determination (from available borehole data), the
geometry, structure and depth relations to modern
topography of the RLS. Drawback in utilizing High-
resolution seismic data for a regional study such as
this is its unavailability, high cost and proprietary
restriction. Borehole log data are very valuable and
provide direct observation of structural and
lithologic information to centimetre detail; they also
provide clear descriptions of how rocks are spatially
laid down. Advances in geological data processing
techniques and software development coupled with
3D visualization techniques have improved the
understanding of subsurface phenomenon that
allows easy correlation, accurate feature detection
and better morphologic investigation. Each of the
stratigraphic units is accurately mapped with high
level of accuracy. The borehole log data were made
available by the Council of Geosciences, Pretoria
and were extensively utilized for this study
METHODS
The first stage involved borehole data collection,
sorting and validation. 1200 boreholes logs
thatpenetrate at least on strarigraphic unit were
included. Database construction and generation of
location maps, strip-logs, interval structure and
isopach maps and geological model followed this.
Other relevant information such as existing
stratigraphic section, geological maps (at various
scales), field mapping records, mine plans,
aeromagnetic, gravity and seismic records were
used for re-verification and interpretation purposes.
Validation of few of the inferred fault zones from
the structure contours, isopach maps and grid
models was carried out by direct observation and
62
measurement of fracture and fault slip orientations
on selected oriented cores. This information was
used for kinematic interpretation. 3D models,
stratigraphic solid models, isosurfaces, fence
diagrams, isopachs and isopach stacks, strip logs,
and surface maps were generated to enhance
interpretation of the subsurface structures and
geometry.
RESULT
Nortwestern Bushveld
The extreme NE end around Amandelbult and the
Northern section dips and thickens toward the
southeast in a step-like manner as revealed by the
3D model and fence diagram in Figure 1. The
Northern and Southern Gap area coincide with
inferred fault planes.
Central Parts of Western Bushveld
The structural trend and the outcrop trend are
parallel to the trend of Rustenburg fault indicating
that the NNW-SSE trend might have a strong
influence on the magma migration path in the area.
Southwestern Bushveld
The Southwestern Bushveld Complex indicates
NNW trending structures while the outcrop trends
E-W. More graben-shaped structures than indicated
on the current geologic map can be inferred from
the interval structural and isopach maps.
Northeastern Bushveld
Widespread doming of all the RLS stratigraphic
units and underlying units was observed on the 3D
models. Similarities between interval structure
contour patterns and the Archaean floor structure
contours indicate that structures here are probably
floor rock controlled. The structural trend is rather
irregular and includes N-S, NNW, E-W, and NE
trends.
Central Eastern Bushveld and Southeastern
Bushveld
The heterogeneities in structure, thickness
relationship and thickness trends are widespread in
the Eastern Bushveld Complex. Structures in the
Southeastern Bushveld trend N-S and NNW while
in the central section of the lobe, the structural trend
varies from E-W to ENE.
Northern Bushveld
The Northern Bushveld compartment model
exhibits northward dipping in the northern part,
while the central part of the lobe is dominated by
prominent horst and graben structures together with
several strike slip movement. The models also
reveal that the RLS in this lobe rests progressively
on older rocks from south to north where it directly
lies on the Archaean floor confirming the earlier
observation by Ashwal et al. (2005) and Kinnaird et
al. (2005). Further southwards the Upper Zone
transgressed underlying RLS rocks to form a horst
and graben structure at the central sector. Presence
of folds and step-like features in the floor of the
central sector probably indicate imbricate staking
due to thrusting which had been reported earlier by
Friese, 2004. However, the Lower Zone unit at the
southern sector of the Northern Bushveld
transgressed the overlying RLS rocks and rest
directly on the Transvaal rocks which further
confirms thrust movement in this area. The regional
outcrop trend is N-S to NNW while most of the
structures trend E-W, ENE-WSW, NE and N-S. A
number of folds mostly NW dipping with ENE
trend are also delineated in the central and southern
parts.
DISCUSSION
The step-like geometry (further confirmed by recent
mining activities) in the Northwestern Bushveld
section is probably a series of grabens initiated by
fault reactivation due to increasing magma influx.
This might have lead to differential offset of
different stratigraphic levels by different amount
with the bounding faults growing down-dip, which
probably indicate an extensional system. Another
suggestion is that it could be because of incremental
subsidence, which might be due to magma cooling
or isostatic adjustment to the increasing weight of
additional magma influx. General gentle dipping
and thickening towards the centre especiallyin the
Western Bushveld and Eastern Bushveld was
related to subsidence after deposition according to
Gough and Niekerk (1959) and Hattingh (1995).
However, thickening towards the centre as observed
on the 3D models (see Figure 1) and from inverse
correlation of structure and thickness in most parts
of the Bushveld Complex probably suggest a pre-
Bushveld emplacement feature. Otherwise the edges
of the Complex should be thicker than the subsided
central section; since dipping to the centre should
have been accompanied by flattening towards the
centre if due to subsidence only. Strong inverse
correlation exists between the structures and
thickness of RLS rocks and the Archaean floor of
63
the Northern Bushveld thus implies that most of the
structures are probably Pre- Bushveld and basement
controlled. However, it was observed that faulting
and folding within this compartment affected both
the Archaean floor rocks and the RLS rock and
might probably indicate tectonic movement after the
emplacement of the Bushveld Complex.
The geometric pattern interpretation of the
stratigraphic intervals of the RLS in this study
suggests continuous east-west horizontal to sub-
horizontal emplacement of the Bushveld Complex.
The study also revealed a few anomalously thick
zones, suggested to be likely magma feeder sites.
64
Figure 1: 3D Model and fence diagrams of sections of the RLS within the Bushveld Complex.
65
CONCLUSION
Major advantages of this study include the perfect conformity of the results with previous field studies
and geophysical investigations. The study allowed complex geological structures and architectures to be
depicted and demonstrates the usefulness of spatial analysis and 3D visualization in solving pertinent
geological problems.
The study provides good insight into both surface and subsurface structural investigation the RLS
geometry providing better understanding and enhanced thorough interpretation of geological relationships
and associated structural features.
REFERENCES
ASHWAL, L. D., WEBB, S. J. & KNOPER, M. W. 2005. Magmatic stratigraphy in the Bushveld
Northern Lobe: continuous geophysical and mineralogical data from the 2950 m Bellevue drillcore. South
African Journal of Geology, 108, 199-232.
CAWTHORN, R. G. & WEBB, S. J. 2001. Connectivity between the western and eastern limbs of the
Bushveld Complex. Tectonophysics, 330, 195–209.
FRIESE, A.E.W. (2004). Geology and tectono-magmatic evolution of the PPL concession area, Villa
Nora-Potgietersrus Limb, Bushveld Complex. Geological Visitor Guide, Potgietersrus Platinums Limited,
57 pp.
GOUGH, D. I., & VAN NIEKERK, C. B. (1959). A study of the palaeomagnetism of the bushveld
gabbrot. Philosophical Magazine, 4(37), 126-136.
HATTINGH, P. J. (1995). Palaeomagnetic constraints on the emplacement of the Bushveld
Complex. Journal of African Earth Sciences, 21(4), 549-551.
KINNAIRD, J. A., HUTCHINSON, D., SCHURMANN, L., NEX, P. & DE LANGE, R. 2005. Petrology
and mineralisation of the southern Platreef: northern limb of the Bushveld Complex, South Africa.
Mineralium Deposita, 40, 576-597.
NALDRETT, A. J. 2009. Fundamentals of magmatic sulfide deposits. In: Li C, Ripley EM (eds) New
developments in magmatic Ni–Cu and PGE deposits. Geol Publ House.
BARNES, S.-J., MAIER, W. & ASHWAL, L. 2004. Platinum-group element distribution in the main
zone and upper zone of the Bushveld Complex, South Africa. Chemical Geology, 208, 293-317.
VERMAAK, C. F. 1995. The Platinum-Group Metals: A Global Perspective, Randburg, South Africa :
Mintek, 1995.
66
ESTIMATING DAILY SOLAR RADIATION FROM MONTHLY VALUES OVER
SELECTED NIGERIA STATIONS FOR SOLAR ENERGY UTILIZATION
Dada, B.M and Okogbue, E.C
Federal University of Technology, Akure, Nigeria
E- mail: bolomos@ yahoo.com and [email protected]
ABSTRACT
The Solar radiation needed for effective research into solar energy utilization can be determined
using concise and reliable data which can be gotten from hourly or daily data.
The parameters which govern a physical model of the sky, should be taken hourly or daily. The
values which fluctuate according to the fluctuating changes in the meteorological and
environmental situations should be analysed with data over a short period of time. These
parameters include the sunshine hours, Solar radiation, cloud cover, temperature etc.
In predicting the performance of Solar energy conversion devices, a sequence of daily radiation
is always required. The daily data are not readily available, hence, there is need for the
derivation of the needed, which is the daily solar radiation data from the available – the monthly
averages.
For many stations in Nigeria, only monthly long – term averages are available and the problem
of extracting reliable information always sets in.
Therefore, this paper proffers solutions to this by establishing a procedure for the derivation of
daily Solar radiation from the monthly averages using Fourier series.
KEYWORDS: Solar Radiation, Month averages, Daily data and Fourier Series.
INTRODUCTION
Solar radiation is a very important variable
in the field of Meteorology and other related
field. Radiation from the sun is the major
source of energy for the sustenance of life
on earth. The sun being the heat engine
transforms one energy source to another.
Sun helps in the metabolism of plants which
are major contributors to the existence of
man. Therefore, it is germane to study the
solar radiation.
There are three major forms of
dissemination of solar radiation. They are;
the short wave radiation that originates
directly from the sun to the earth, the long
wave – infrared radiation which is emitted
by the earth atmospheric system, the net
radiation which is the outcome of the long
wave radiation and the short wave radiation.
Since most of the energy is swallowed by
the atmosphere only very few which are
radiated to the earth are stored up there. This
is known as the short wave solar radiation.
Due to the spontaneous changes in the rate
of insolation, short wave radiation can be
accurately studied by using daily data. The
importance of proper analysis and
monitoring of this form of radiation is the
import of this study. Though, the tropical
Africa is blessed with abundant solar
energy, it is however, still an unexplored
area because of the lack of comprehensive
data due to non – availability of instruments
and man – power. Therefore, it is of great
necessity to get a way around getting the
needed from the available. One of such ways
is by estimating daily data from monthly
averages and using the derived data to
characterize the sky condition in the area.
This method has been used in Genova (Italy)
and in Rome for Rainfall. Okogbue and
67
Adedokun (2002a) and Okogbue et al
(2002b) have also used Fourier series
method to analyse daily and monthly solar
radiation at Ondo and Ile-Ife, Nigeria
respectively. Angstrom model was
originally derived for the daily solar
radiation and hours of sunshine (Angstrom,
1929, 1930 and 1950). Nonetheless, being a
linear function it can be readily applied to
mean monthly data since the expected
values.
Hence, a number of workers have used both
daily data and monthly averaged daily data,
namely; Bristow and Campbell (1984),
Nagaraja Rao et al, (1985) and Allen (1997).
DATA AND METHODOLOGY
Dataset consisting of monthly global solar
radiation and sunshine hours for five stations
namely:Minna, Enugu Ibadan , Sokoto, and
Kano For the period of 1988 -1997 for both
and global radiation. The radiation data
which were measured using the Gunn-
bellani integrator which is graduated in mm
was graduated after Folayan (1998). He
reported the calibration of Gun – Bellani
radiation distillates with Pyranometer
readings for stations South of Ibadan as
1mm =1.357 mJ /m2 and 1.263 mJ/ m
2 for
Northern station.
ESTIMATION OF DAILY SOLAR
RADIATION FROM MONTHLY MEAN
USING FOURIER SERIES
The data set of monthly mean for the
aforementioned stations were used in
deriving daily data set using the following
Fourier series formulae;
Y(m) is considered to be a sequence of 12
monthly radiation averages of calculated
using a regular sequence of daily values.
𝑥𝑑 = 𝐴0 + ∑ (𝐴K cos2𝜋
𝑁𝐾𝑑 + Bk sin
2𝜋
𝑁Kd) + B6 Sin (
2π
N
5
𝐾=1
6d − φ) … … … … Eqn. 1
Such that,
< 𝑥𝑑 >𝑚= 𝑦𝑚 (𝑚 = 1, 2, … , 12)……. Eqn. 2
Where < > m = Average relative to the mth month.
D = Day number which can range from 1 to
N = 365 or 366 (leap year) days. For the
purpose of this work 366 days was used in
which case the mean of the last days in
February and the 1st days in March was
used as the data for February for non-leap
years..The system will originally satisfy 12
conditions going by the 12 months in a year,
therefore, ɸ = phase angle, will satisfy these
conditions. When ɸ = 0 or Π. The absolute
values of the fourier component
corresponding to the shortest period
(approximately 2 months i.e B6 ) takes the
minimum among its possible values.When
we reduce equation 1 and 2, we have:
𝑦𝑚 = 𝐴0 + ∑(𝐴𝑘 < 𝐶𝑜𝑠 2𝜋
𝑁
5
𝐾=1
𝐾𝑑 >𝑚+ 𝐵𝑘 < 𝑆𝑖𝑛 2𝜋
𝑁 𝐾𝑑 >𝑚) + 𝐵6 < 𝑆𝑖𝑛
2𝜋
𝑁 𝐾𝑑 >𝑚 … 3
68
Where ( m = 1, 2, …, 12)
A table for both the 365 days and 366 days
will be presented and the inverse Matric (C )
of each value will be gotten and will be
multiplied by 1000 this will help in the
calculation of the coefficient As and Bs for
the 12 monthly averages. The Formulae are;
𝐴𝐾−1 = ∑ 𝐶𝑘𝑚
12
𝑚=1
𝑌𝑚 ( 𝐾 = 1, 2, … , 6)
𝐵𝐾−6 = ∑ 𝐶𝑘𝑚12𝑚=1 𝑌𝑚 ( 𝐾 = 1, 2, … , 6)
There will be a symmetric breaking in the
line due to non - uniformity in the days in
each of the months, i.e., (28, 29, 30, 31
days).
TABLE 1: Coefficient Of Ckm Of The Matrix Defined In Equation (4) Multiplied By 100 For A Year Of 366
Days.
85 77 85 82 85 82 85 85 82 85 82 85
164 111 48 -41 -119 -160 -167 -121 -43 45 118 166
149 0 -147 -155 -4 147 156 1 -151 -151 -1 156
126 -125 -134 122 139 -126 -136 131 131 -131 -132 136
97 -199 92 111 -202 92 108 -203 101 101 -202 105
62 -170 226 -215 150 -47 -66 162 -218 217 -159 57
48 110 164 162 123 45 -42 -122 -161 -166 -117 -45
92 164 93 -82 -176 -92 85 177 86 -88 -174 -87
134 126 -123 -138 126 137 -129 -134 131 132 -132 -129
174 2 -176 164 15 -183 173 5 -178 178 -5 -169
219 -162 52 68 -167 219 -213 153 -55 -59 158 -215
136 -141 139 -133 130 -128 126 -125 127 -128 129 -131
TABLE 2: Derived figures for A0 – A5
STATIONS A0 A1 A2 A3 A4 A5
ENUGU 17.2997 2.2429 -0.9959 -0.8453 -0.6523 -0.5693
IBADAN 17.8286 1.4662 -1.8913 -1.1248 -0.0680 -0.4881
MINNA 18.9551 1.0528 -2.9029 -1.2850 -0.6273 -0.5291
JOS 20.8649 2.6464 -1.4995 -1.5072 -0.4098 -0.5149
SOKOTO 20.8565 0.1703 -2.2057 -0.2398 -0.0534 0.1362
KANO 20.8649 2.6464 -1.4995 -1.5072 -0.4098 0.5149
TABLE 3: Derived figures for
B1 – B6
STATIONS B1 B2 B3 B4 B5 B6
ENUGU 1.19707 -1.42229 0.87333 -0.18791 0.06530 0.12552
IBADAN 2.11684 -1.6323 0.82925 0.09669 0.43502 0.18772
MINNA 0.94118 -0.69847 1.18212 0.35976 1.10881 0.72238
JOS 1.52861 0.47452 0.82742 0.38243 1.27446 0.93583
SOKOTO 2.07932 -0.10533 0.13147 1.12089 0.62534 0.45412
KANO 1.52861 0.47452 0.82742 0.38243 1.27446 0.93583
69
Figure 1 represents the time series graphs of Minna. Similar graphs are generated for Ibadan, Enugu , Kano and
Sokoto. The graphs indicate the annual patterns of flow for the period of 1988 – 1997 ; for both the real data and the
simulated using fourier series.
RESULTS AND DISCUSSION
From the above formulae, A0, A1, A2, A3, A4, A5, B1, B2, B3, B4, B5, and B6 were derived from
equation 4 for all the stations.
CONCLUSION
Estimation of global solar radiation is vital for fabrication of solar energy system everywhere
where adequate observations are paramount. For predicting the performance of solar energy, a
sequence of daily radiation is often required which in most cases are not available.
Therefore, to get accurate estimation of global solar radiation over a station using the daily data
derived from the available monthly average, the method above can be employed.
REFERENCES
Adedokun JA, Adeyefa ZD, Okogbue E, Holmgren B. 1994. Measurement of Solar and
Longwave Radiation Fluxes over Ile-Ife, Nigeria.
Almorox, J., Benito, M., Hontoria, C. Estimation of monthly Angstrom–Prescott equation
coefficients from measured daily data in Toledo, Spain. Renewable Energy 30, 2005, pp. 931-
936.
Haubold HJ, Onuora LI (eds). New York AIP Press No. 320: New York; 179–190.
Hook JE, McClendon RW. 1992. Estimation of solar radiation data missing from long-term
meteorological records. Agronomy Journal 88: 739–742.
In American Institute of Physics (AIP) Conference Proceedings,
Iqbal, M, 1983. An introduction to Solar Radiation. Academic press, New York, pp: 223.
Okogbue EC, Adedokun JA, Jegede OO. 2002. Fourier series analysis of daily global and diffuse
Irradiation for Ile-Ife, Nigeria. Journal of Applied Sciences 5(3): 3034–3045.
Okogbue EC, Adedokun JA. 2002a. On the estimation of solar radiation at Ondo, Nigeria.
Nigerian Journal of Physics 14(1): 97–104.
Okogbue EC, Adedokun JA. 2002b. Characterization of sky conditions over Ile-Ife, Nigeria
based on 1992–1998 Solar Radiation Observations. Meteorogische Zeitschrift, Germany 11(6):
419–423.
5
10
15
20
251
21
41
61
81
10
1
12
1
14
1
16
1
18
1
20
1
22
1
24
1
26
1
28
1
30
1
32
1
34
1
36
1
SOLA
R R
AD
IATI
ON
(M
J/m
2)
DAYS
FIG. 1: TIME SERIES GRAPH OF SIMULATED AND REAL DATA SET FOR MINNA (1988 -1998)
SIMULATED usingfourier series
REAL
70
Okogbue EC. 2007. Broad-band solar irradiance and photometric illuminance at the tropical
station. Ile-Ife, Nigeria. Unpublished PhD Thesis, Obafemi Awolowo University, Ile-Ife,
Nigeria, 223
71
POTENTIALS OF SOME LATERITIC SOILS FROM ORE, SOUTHWESTERN NIGERIA AS
LINERS IN LANDFILLS
Sunday. O. Daramola* and Babafemi I. Ilesanmi**
*Department of Applied Geology, Federal University of Technology Akure, Nigeria
Email: [email protected] **Josh-Tob Geotechnics Engineering Limited,71a Shyllon Street, off Ikorodu road, Ilupeju Lagos.
Email: [email protected]
ABSTRACT
Liners are very important part of engineered landfills as they control the migration of leachates and
other toxic constituents into underlying aquifers or nearby rivers, thereby contaminating the local water.
Hence, materials to be used as liners should be able to stand the test of time and provide reliable leak
protection. The suitability of some lateritic soils from Ore in southwestern Nigeria has been investigated
for the purpose. Six bulk samples of lateritic soils were collected from the study area and subjected to
engineering geological tests which include grain size distribution, Atterberg limit, specific gravity,
compaction and permeability. Results indicate that the soils contain clay (24-37%), silt (18-28%), sand
(19-38%) and Gravel (10-16%) . Atterberg limits test also indicate that the liquid limit values range from
37-46%, plastic limit from 17.26%-19.20% and plasticity index from 16.58%-21.81%. Specific gravity
values range from 2.60-2.70, maximium dry density range from 1730.25-1780 kg/m3, optimum moisture
content varies from 17.96-19.20 while the permeability varies from 2.95 ×10-12 m/s to 8.34 ×10-12 m/s.
The soils were adjudged suitable for use as liners as they compare favorably with the recommendations
of earlier investigators.
Keywords: Atterberg Limits, Landfill, Lateritic Soils, Liner
INTRODUCTION
In most developing countries, rapid development
cum increased population has raised the quantity
of waste generated. However, little concern has
been shown to the management of wastes in
these developing countries like Nigeria as
piles/heaps of these wastes are recklessly
dumped in public arenas. Sanitary landfilling is
one of the most common and widely accepted
ways of getting rid of these wastes. This is due
to its economic and environmentally friendly
approach to waste management. For example,
most of the materials needed for the construction
are readily available and naturally occurring in
most environments.
The mineral seal or liner is an important
component of the sanitary landfill as it restricts
the movement of leachates/contaminants into the
subsurface or the groundwater thereby
contaminating them. It also prevents the flow of
infiltrating/percolating water into the waste. The
climatic setting of Nigeria favours the
production of lateritic soils which are the
products of intensive weathering that occurs
under tropical and subtropical climatic
conditions. Hence, since this type of soil
abounds everywhere (readily available) they are
the most commonly used soils for various
construction purposes. The intent of this study is
to investigate the geotechnical properties of
some lateritic soils from Ore, Southwestern
Nigeria with a view to determining their
suitability for use as mineral seals in sanitary
landfills.
MATERIALS AND METHODS A
reconnaissance visit to the site was undertaken
prior to the sampling. Six bulk soil samples were
collected from three test pits before Show-Boy
Junction, in Ore. The samples were collected at
depths 0.5m and 1.0m. The soils collected were
subjected to air drying for two weeks after
72
which laboratory tests were conducted to
determine the grain size distribution and
consistency characteristics, specific gravity,
permeability and moisture density relationships.
The tests were carried out in accordance with the
procedures outlined in the British Standards
(BS) 1377.
RESULTS AND DISCUSSIONS
The grain size distribution characteristic of the
studied soils is reflected particle size distribution
curves. Five of the samples classify as clayey
sand while one falls within the class of silty
clay. The result shows that the percentage fines
ranges from 46%-65%. All the studied soils also
met the >20% clay content specified by
Oeltzshner(1992) as they all contains clayey
fractions ranging between 24% and 37%. It is
also worthy to note that the largest particle
diameter recorded by the tested soils is ≤5mm,
this is smaller than the specification of ONORM
2074 (1990) who recommended soils with
largest grain size less than or equal to 63mm.
The percentage gravel recorded by the soils also
conform with the specification of (Daniel, 1993)
who suggested a gravel amount less than or
equal to 30% as they have gravel size content
ranging from 10 to 16%. The liquid limit values
ranges from 37 -46%, plasticity limit between
19.26 and 23.64 and the plasticity index between
18.36-21.81. Hence all the soils lie above the
arbitrary A-line and falls within the field of
inorganic clays with intermediate plasticity on
the Cassagrande (1947) plasticity chart (Figure
2). The presence of high content of clay,
especially active clay minerals generally
corresponds to a decrease in the size of
microscale pores that subsequently lower the
hydraulic conductivity of the soil. The soils
fulfill the liquid limit and plasticity index values
requirement suggested by Seymour and Peacock
(1994) as they posses liquid limit less than 90%
and plasticity indicies less than 65%
recommended for soils to be used as liners in
landfills. However, soils with high liquid limit
and plasticity index are considered suitable for
mineral seals in sanitary landfills as they are
expected to possess low hydraulic conductivity
(Ige and Ogunsanwo, 2009). The soils possess
activity values ranging from 0.55-0.79, thus
ranking them as either normally active clays or
inactive clays according to Skempton (1957)
activity classification. Thus, the soils possess
activity values greater than 0.3 recommended by
Benson et al (1994) and Rowe et al (1995). The
specific gravity values of the soils tested range
between 2.6 and 2.7. These values are greater
than 2.22 specified by ONORM 2074 (1990),
hence can be adjudged suitable for use as
mineral seals. The soils recorded maximum dry
density values ranging from 1.73g/cm3 to 1.78
g/cm3, these values conform to 1.7g/cm3
specified by ONORMS 2074 1990 while all the
test soils recorded a maximum dry density
greater than 1.74t/ cm3 suggested by Kabir and
Tahar (2006). The soils recorded permeability
values which are
Figure 1: Grain size distribution curves of the studied soils
73
Figure 2: Plots of the studied soils on Cassagrande plasticity chart
lower than the specified maximum 10 ^-9
stipulated by USEPA (1982) ONORMS 1982
and Daniel (1993) except sample 1. In the
European Union, landfill regulations make it
mandatory to entomb waste using engineered
lining systems except at sites where in situ
hydraulic conductivity is less than 10-9 m/s
(Allen,2001).
CONCLUSION A comparison of the test results on the studied
lateritic soils with the values suggested by
previous investigators/researchers shows that the
soils possess a suitable potential as mineral seals
in landfills.
REFERENCES
Allen, A., (2001). Containment landfills: the
myth of sustainability. Engineering
Geology, 60, 3-19.
British Standard Institution 1377. (1990).
Methods of Test for Soil for Civil
Engineering Purposes. BS1377,
London.
Cassagrande, A. (1948) Classification and
identification of soils, Am, Soc. Civil
Engr. 113-901
Daniel, D.E. (1993). Clay Liners. In:
Geotechnical Practice for Waste
Disposal (Daniel D.E ed). Chapman
Hall, London, U.K, 137-163.
EPA. (1990.) Compilation of Information
on Alternative Barriers for Liner and
Cover Systems. EPA600-R- 91-002.
Prepared by Daniel, D.E. & Estornell, P.M.
for Office of Research and
Development, Washington, DC.
Ige O.O and Ogunsanwo, O.(2011): Characterisation of a Terrain and
Biotite-Granite Derived Lateritic Soils
of Ilorin, Nigeria, For use in Landfill Barrier.
Global Journal of Geological Sciences.
9(1). 1-9
Jones, R.M., Murray, E.J. & Rix, D.W.
(1993). Selection of clays for use as
landfill liners. Waste Disposal by
Landfill. Proceedings Symposium
Green 93. 433-438.
Kabir, M.H and Taha, TR. (2006).
Sedimentary Residual soils as a
hydraulic barrier in waste
74
containment systems. 2nd International Conference on Advances in soft soil Engineering.
Technology Putrajaya, Malaysia. 894-904.
Ogunsanwo, O (1996): Geotechnical Investigation of some soils from S.W. Nigeria for use
as mineral seals in waste disposal landfills. Bulletin of the International Association of
Engineering Geology, Paris. 54. 119-123.
Oeltzschner, H(1992): Anjoderin an die Geologic, Hydrogeologe und Geotechnik Beim
Bau von Deponie thorme-kozmiensky K.J. ed. Addichtung von Deponien und Altlasten.
E.F. Verlag fur Energie und Umwelttechnik GmbH, Berlin. 53-82
Parker, R.J., Bateman, S. and William, D. (1993): Design and Management of Landfills.
In: Fell R et al(eds) Geotechnical Management of Waste and Contamination. A.A.
Balkema, Roterdam. 209-252.
Rowe, R. K. (2005). Long-term performance of contaminant barrier systems. Geotechnique.
55(9): 631-678.
Seymour K.J. and Peacock A.J. (1994): Quality coctrol of Clay liners. In: Christensen
T.H et. al. (eds), Landfilling wastes Barriers. E & F.N. Spon. London. 69-79.
USEPA(United State Environmetal Protection Agency) (1982): Harzardous Waste
Management Systems: Permitting Requirements for Land Disposal Facilities. Federal
Register, July 16.
75
RISK ASSESSMENT OF ACCELERATED GULLY EROSION IN IKPOBA OKHA AREA
OF EDO STATE, NIGERIA
Adediji, Aderemi; Iyamu, Felix and Fakpor, Akpofure Miller
Department of Geography, ObafemiAwolowo University, Ile-Ife, Nigeria
Department of Remote Sensing and Geoscience Information System,
Federal University of Technology Akure, Nigeria.
[email protected], [email protected], [email protected] (Author for
Correspondence)
ABSTRACT
Accelerated erosion has continued to bea major ecologicaland environmental issuefacing Nigeria,
affecting human and natural resources. This is posing serious risk in Ikpoba Okha area of Edo State
despite measures at solving it.Thestudy is aimed atdetermining vulnerable areas, sediment lossfrom
the gully andidentifythreat to resources as well asmeasures for its management and control.
Geographic coordinates and elevation of gully catchments were collected from two purposely
selected gullies in the area using GPS receiver; gully morphometry attributes were also measured.
These were integrated with data obtained from satellite images, topographic and geologic maps of
the area using ArcGIS 9.3 software and analyzed. The total estimated sediment loss from the gullies
is 407,385.84tonnes.The risk assessment showed several buildings and roads under Highly Severe,
Severe andModerate vulnerability.Evidence of degradation of natural resourceswasalso observed,
with large land area around Ikpoba River under Severe threat of gully erosion thus affecting arable
land, water quality and the survival of aquatic life. A combination of ecological, engineering and
policy measures are recommended for control.
Key words: Gully Erosion, GIS, Resources, Environment, Vulnerability.
INTRODUCTION
The term accelerated erosion is often
used when the rate ofsoil removal is far faster
than its replacement or soil is naturally
formed. The process of soil erosion when
balanced with soil formation is said to be
normal only when it occurs naturally. Strahler
(1975) defined accelerated erosion as the
displacement and removal of soil from a land
surface such that the removal process far
exceeds its replacement by pedologicalmeans.
Ofomata (2000) observed that out of
75,488km2 land of southern eastern Nigeria,
accelerated soil erosion has affected
53,028km2 or 71.25% of the total land area.
76
Gullying is a manifestation of accelerated soil
erosion.Erosion is usually accelerated by such
human activities as forest logging, farming,
grazing, construction, mineral exploration and
exploitation.Gullies in southwestern Nigeria
appear to be an urban phenomenon (Enabor
and Sagua, 1988; Jeje, 1988) and have been
occurring at unprecedented rates, creating
numerous problems and resulting in heavy
economic, human and social losses in many of
our cities. Often, such losses are so heavy that
affected communities cannot cope without
external aids from ecological funds from
government and non-governmental
organizations.
Accelerated soil erosion has adverse
environmental andeconomic impacts (Lal,
1998) affecting natural and human resources.
This study presents a method by which soil
erosion can be assessed and its risk modeled
using field data, remote sensing and
Geographic Information System (GIS).The
capabilities of these technologies are
enhanced when they are integrated
withmulti-criteria decision analysis (MCDA)
for the generation of erosion index map based
on the relationshipsbetween various factors
as noted by Ojoet al. (2015) in their
evaluation of erosion risk in a basement
complex in Southwestern Nigeria. An
environment is considered to be at risk when
any of the mitigating factors of erosion in
terrain (surface cover, slope, land
management practice and soil erodibility)
favour the occurrence of soil erosion. The risk
factors change according to the prevailing
conditions whether man-made or natural
conditions. Therefore, the main thrust of this
study is on observing feature of soil erosion
and how they can be used in assessment and
spatialmodeling of erosion risk, determining
vulnerable areas as well as identify measures
for its management and control as it
affectsIkpoba-Okha local government area of
Edo State, Nigeria.
METHODOLOGY
Two gullies in Oregbeni Housing Estate
and Queen Ede School in IkpobaOkha Local
Government Area werepurposely selectedfor
this study due to their size and proximity to
human settlements in the area. Data on the
length, width and depth of each gully channel
was determined using leveling instrument,
abney level, measuring tape and surveyor’s
pegs. Measurements were taken at a regular
interval of 10 meters. All points interval which
include both the upper and basal parts of
gullies catchments were measured andGermin
72 Global Positioning System (GPS) receiver
was used for determining the coordinates and
spot heights. Secondary data were obtained
from satellite images, topographic, geologic,
road and lay out maps of the study area.
ArcGIS 9.3 softwarewas used for integrating
these data in its database and subsequent
construction of a Digital Elevation Model
(DEM) of the gullies.
A Multi-Criteria Evaluation (MCE) using
weighted overlay for erosion factors such
asslope, land cover/use, soil types and river
was carried out.MCE erosion potential area
map was produced. This shows the degree of
erosion sensitivity of each areawhich were
classified into five categories (nil, slight,
moderate, severe and highly severe).The
cross-sectional area of each of the study
gullies was determined using a formula
adopted by (Ofomata, 2000) in southeastern
Nigeria. The value of the cross-sectional area
obtained was used to estimate the volume of
soil removed by gully erosion from each of the
study gully catchments. The amount of soil
loss from the gully site was estimated by
multiplying volume with the soil bulk density
(Jeje, 2005; Adediji,et al. 2009). Figures 1 and
2 bellow shows the flowchart for the study
andSoils ofIkpoba River Basin.
77
.
Fig. 1: Flow Chart for the Study Methods
Fig. 2: Soils of the Ikpoba River Basin
(Source: Akujeze, 2004)
RESULTS/DISCUSSION
The total eroded area in Ikpoba-Okha is
estimated at 100,466.57m2which accounts for
2% of the study area. Of this amount, Queen
Ede school gully area accounted for about
95% (96,957.13m2) of the total eroded area
while Oregbeni Housing Estate gully area is
about 3,509.44m2. Built-up occupies the
largest area (3,441,154.46m2) accounting for
66%of the entire study area, while the
vegetated area, flood plain and river occupies
942,410.91m2, 514,412.04m2 and 34,736.94
m2 respectively. Figure 3 shows the land
use/cover classification.
Large tonnes of sediment were lost to
erosion. The total volume of soil loss and
weight of sediment loss at Queen Ede school
gully was the highest with value of
292,010.75m3 and 359,173.72 tonnes,
respectively. On the other hand, Oregbeni
Housing Estate had a sediment loss of
48,212.62 tonnes and a 39,197.25m3 volume
of soil loss to the erosion.
Fig. 3: Map of the Study Area showing Land
use Classification
The slope shapes as revealed by the
DEMs of the study gullies (figure 4) are mainly
convex with Queen Ede gully site being the
steepest. This would usually lead to overland
78
flow generated from all sides of the slope and
subsequently increase runoff into the gully
channels mostly in areas with poor vegetal
cover. This was similarly observed by Adedijiet
al. (2009) in Irele LGA of Ondo State, Nigeria.
Fig.4: Digital Elevation Model (DEM) showing
the Study Gullies lying in one of the Steepest
Areas of the Terrain
The risk assessment showed several
buildings and roads under Highly Severe,
Severe and Moderate vulnerability (Figure 5).
Evidence of degradation of natural resources
was also observed, with large land area
around Ikpoba River under Severe and
Moderate threat of gully erosion thus
affecting arable land, water quality and the
survival of aquatic life. Areas more vulnerable
to gully erosion are located on the steeper
slopes and unstable geology. This may be
enhanced further by high rainfall which
causes the saturation of soils also observed in
the study area.
Fig.5: Vulnerable Areas to Accelerated Gully
Erosion
CONCLUSION
It can be concluded that the gully
erosion in Ikpoba-Okha area, accelerated by
the built-up environment and other human
activities going on around the area, led to
serious land degradation and a poses high risk
to some natural resources and the socio-culture
of the people. A combination of ecological,
engineering and policy measures are
recommended for control.
REFERENCES
Adediji, A., Ibitoye, M.O and Ekanade, O.
(2009). “Generation of Digital Elevation
Models (DEMS) for Gullies in Irele Local
Government Area of Ondo State, Nigeria”
African Journal of Environmental Science
and Technology 4(3), 065-079.
Oregbeni Housing Estate
Gully Erosion Site
Queen Ede School Gully
Erosion Site
79
Enabor, E.E. and Sagua, V.O. (1988).
“Ecological Disaster in Nigeria Soil
Erosion, Introduction and
Recommendations. In Sagua, V.O. Enabor,
E.E; Ofomata, GEK, Oboge, K.O. and
Oyebande.
Jeje, L.K. (1988). “Soil Characteristics,
Processes and Extent in the Lowland
Rainforest Areas of Southwestern Nigeria
in (ed) E.E. Enaboret al; Ecological
Disasters; Soil Erosion, Federal Ministry
of Science and Technology, Lagos, 163-
189.
Jeje, L.K. (2005). “Urbanization and
Accelerated Erosion: Examples from
southwestern Nigeria”. Nigerian Journal
of Environmental Management, 2, 40-53.
Lal, R. (1998). Soil erosion impact on
agronomic productivity and environment
quality: Critical Review. Plant Science, 17:
319 – 464.
Ofomata, G.E.K. (2000). “Classification of
soil Erosion with specific reference to
Anambra State of Nigeria”.Environmental
80
Review, 3(2), 252-2555.
Ojo, J. S. Olorunfemi, M. O. Akinluyi, F. O. Bayode, S. Akintorinwa, O. J.and
Omosuyi, G. O. (2015). “Evaluating Soil Erosion Risk in the Basement Complex Terrain ofAkure Metropolis,
Southwestern Nigeria”, Journal of Geography and Geology; Canadian Center of Science and Education, Vol.
7, No. 1; 56-64.
Strahler, A.N. (1975). “Physical
Geography”. 4th Edition John Willey &
Sons Inc; New York.
81
ENERGY CONSERVATION IN THE BUILT ENVIRONMENT: THE ROLES OF ARCHITECTS
Ganiyu, Sikiru Abiodun and Adetunji, Olufemi Samson
Department of Architecture, Federal University of Technology, P.M.B. 704, Akure, Nigeria
Tel: +2348066063229 E-mail: [email protected]; [email protected]
Corresponding E-mail: [email protected]
ABSTRACT
Building industry appears to be entering another period of change in essence of minimizing energy, carbon
and environmental footprints of various building types. Among the most significant environmental challenges
of our time are global climate change, excessive fossil fuel dependency and growing demand of energy in our
cities. Globally, energy demand of buildings amounts to one third of world energy use and this is responsible
for more than half of total greenhouse gas emissions. This change is being driven by a need to optimize and
conserve resources especially energy. The architects as important stakeholder have important roles to play in
accomplishing this onerous goal. The roles of architects in achieving energy conservation in built
environment were drawn from relevant buildings that serve as case studies and literatures. This paper argues
that architects play a critical but poorly understood and often overlooked role in the built environment. In the
face of climate change, the paper finds purely architectural solutions, such taking advantage of their
sophisticated artistic visions in minimizing the negative environmental impact of their structures. Also,
inculcating the principles of green architecture and modern energy conservation technologies in the planning
and designing of buildings. The paper, therefore recommends that the positive impacts of architects’ creative
instinct is important to achieving energy conservation in new and existing buildings and in doing this
architects can not only preserve the environment but improve it.
Keywords: architects, building design, built environment, energy conservation, stakeholders
INTRODUCTION
There has been an increasing demand for energy
efficiency and sustainability in buildings (Janda,
2009). Therefore, reduction of energy use in
buildings is a critical componentof meeting carbon
reduction commitments. There are several ways of
accomplishing this goal, each of whichemphasizes
actions to be taken by different stakeholders. Much
of the work in this area follows a
physical,technical, and economic model of the
built environment (Lutzenhiser, 1993). In this
scenario, architects, engineers, andefficiency
advocates are the major players, makingtechnical
improvements to existing buildings anddesigning
new ones to higher standards. In many continents
of the world, different policies on energy
performance of buildings are enacted to serve as
guide to the stakeholders in achieving the goal.
This performance-based approach adds owners,
operators and developers to the list of the
stakeholders.
A problem with designing and constructing
buildings that demand less and conserve more
energy is that stakeholders, especially architects
hesitate to try new innovative design technologies
and processes that have not yet been adopted by
the mainstream (Van der merwe, 2011; Lehmann,
2011). Also, owners are unsure on benefits of
energy savings measures. Someone always has to
be first to use a technology. A few building owners
and designers have made great strides to
significantly change the way commercial buildings
use energy.
Therefore, this paper considers the responsibilities
of architects from profession standpoint. This
perspective conceptualizes work practices
involved in architecture as a profession that is
faced with the challenge of increase energy
demand in buildings and climate change. In the
face of climate change, the paper finds
architectural solutions such as use of materials of
low embodied energy, incorporation of solar
passive techniques in buildings amidst many other
solutions necessary for architects to achieve the
goal.
82
METHODOLOGY
In this study, information were collected different
four case studies on energy and resource efficient
architectural projects around the world.The case
studies are United Nations Office in Nairobi,
Cambria office building in Ebensburg,
Pennsylvania, RETREAT building in Teri and
Adam Joseph Lewis Centre for Environmental
Studies, Oberlin College, Oberlin, Ohio in United
States of America. Also, relevant literatures were
used to get more information of the study.In each
case, highlights were given to energy conservation
measures implemented by the architect such as
passive solar interventions, energy-efficient
systems, building materials with low embodied
energy.
FINDINGS AND DISCUSSION
1.1 Materials and construction technique
In building construction, choice of materials is
imperative in reducing the energy contents of
buildings. Energy reduction is therefore achievable
through the use of low-energy materials, efficient
structural design, reducing the quantities of high-
energy building materials and transportation
energy (Drewe, 2008; Government of Ireland,
2010). The choice of materials also helps to
maximize indoor comfort. This is demonstrated in
RETREAT building in Teri, United Nations Office
in Nairobi and Cambria Office building.
RETREAT building made use of ferro-cement in
the construction of walls and chimneys. Also,
United Nations office is constructed with
stabilized clay bricks and finished with
maintenance –free materials. The low-energy
design features in Cambria Office building are
ground source heat pumps, high performance
windows, walls and roof insulation while finishes
were made from recycled materials.
1.2 Building orientation and fenestration
Building orientation is a significant design
consideration, mainly with regard to solar radiation
and wind. In Nigeria, buildings are best oriented
with the longer sides facing North and South to
minimize solar gain. Windows and other glazed
areas are most vulnerable to heat gains and losses
therefore building are better oriented to reduce the
exposure of such areas to direct sunlight
(Torcellini et al, 2006). Proper location, sizing and
shading forms are important aspect to consider in
achieving low-energy demand buildings. In United
Nations office, the buildings are oriented facing
north-south to achieve maximum daytime lighting
with maximum heat intake and the windows and
other glazed areas are equipped with high quality
solar glasses that insulate the interior against heat
and cold.
1.3 Energy efficient lighting
The Energy Conservation Centre, Japan (2010)
states that lighting is a crucial element in
buildings. In achieving low-energy demand
buildings, the lighting sources are to be
considered. These buildings are to be designed to
allow uttermost dependence on daylighting and
can be supplemented with energy-saving artificial
lighting. United Nations office building in Nairobi
was planned to make use of natural light. The
building has a central atrium running through and
covered with barrel vaulted translucent roof. Also,
glazed roof lights are set at intervals into the roof
above the offices to allow vertical transmission of
light.
1.4 Renewable energy system
In United Nations Building, Nairobi all power
used in the building and its occupants were
generated through harvesting of solar energy
through the use of photovoltaic panels. The cells
were installed on the roof for optimum solar
harvest. In the same building, energy demand is
reduced to 42.5kWh per square metre per year
from much higher value of 62kWh. The generated
solar power is used for low-energy office
equipment installed in the office building. The
architect designed the building for maximum solar
energy yield through mixing polycrystalline and
amorphous silicon solar modules to generate the
energy required by the occupants.
1.5 Landscaping
Landscaping is an important element in altering
the microclimate of a place and conserving energy
83
(Pickles, Brocklebank and Wood, 2011). Proper
landscaping reduces direct sun from striking and
heating up of building surfaces. It prevents
reflected light carrying heat into a building from
the ground or other surfaces. Shanghai Manual
(2011) argues that building landscaping creates
different airflow patterns and can be used to direct
or divert the wind advantageously by causing a
pressure difference. In addition, shades are created
by trees and the effect of grass and shrubs reduce
air temperatures adjoining the building and
provide evaporative cooling. Properly designed
roof gardens help to reduce heat loads in a
building. United Nations Environmental
Programme (2011) revealed that the ambient air
under a tree adjacent to the wall is about 2 °C to
2.5 °C lower than that for unshaded areas, which
reduces heat gain by conduction. In RETREAT
building, deciduous trees are planted on the south
side to cut off teat gains in the summer. Also, these
trees shed leaves during the winter periods to
allow solar gains and to provide wind breaks to
protect the building from winter winds.
CONCLUSION
Each of the four case studies has unique purposes
and functions with their common features.
Therefore, architects as designers are to adopt the
features of energy conservation in designing new
buildings and renovating existing buildings. The
adoption of passive building design principles to
create conservation environments has been
increasingly developed and applied in buildings to
achieve reduced energy demand in building. Also,
the architects are to provide main motivation for
low-energy building through sensitization of
clients to the benefits. The architects also, are to
set measurable energy saving goals at the outset of
project to provide tracking mechanism for the
design and construction process of the project.
REFERENCES
Drewe, D. (2008). Energy conservation in
traditional buildings. Retrieved from
http://www.carbonaction2050.com/sites/car
bonaction2050.com/files/document-
attachment/English%20Heritage%20Energy
%20Conservation.pdf
Government of Ireland (2010).Energy efficiency in
traditional buildings. Retrieved from
http://www.ahg.gov.ie/en/Publications/Herit
agePublications/BuiltHeritagePolicyPublicat
ions/Energy%20Efficiency%20in%20Tradit
ional%20Buildings%20(2010).pdf
Janda, K. B. (2009). Buildings don’t use energy:
People do. Retrieved from
http://www.eci.ox.ac.uk/publications/downl
oads/janda09buildingsdont.pdf
Lehmann, S. (2011). Energy-efficient building
design: Towards climate-responsive
architecture. Retrieved from
http://www.eolss.net/sample-
chapters/c15/e1-32-19-00.pdf
Lutzenhiser, L., (1993). Social and Behavioral
Aspects of Energy Use. Annual Review of
Energy and the Environment, 18: p. 247-89.
Pickles, D., Brocklebank, I. & Wood, C.
(2011).Energy efficiency in historic
buildings. Retrieved from
http://www.english-
heritage.org.uk/publications/energy-
efficiency-historic-buildings-ptl/eehb-
partl.pdf
Shanghai Manual (2011). Green buildings for a
resource efficient future. Retrieved from
http://www.un.org/esa/dsd/susdevtopics/sdt_
pdfs/shanghaimanual/Chapter%206%20-
%20Green%20buildings.pdf
The Energy Conservation Centre, Japan (2010).
Energy conservation for office buildings.
Retrieved from http://www.asiaeec-
col.eccj.or.jp/brochure/pdf/office_building.p
df
Toledo, F. (2006).The roles of architecture in
preventive conservation. Retrieved from
http://www.iccrom.org/ifrcdn/pdf/ICCROM
_13_ArchitPrevenConserv_en.pdf
84
Torcellini, R., Pless, S., Deru, Griffith, B., Long,
N., &Judkoff, R. (2006). Lessons learned
from case studies of six high-performance
buildings. Retrieved from
http://www.nrel.gov/docs/fy06osti/37542.pd
f
United Nations Environmental Programme (2011).
Building for the future: A United Nations
showcase in Nairobi. Retrieved from
http://www.unep.org/gc/gc26/Building-for-
the-Future.pdf
Van der merwe, M. (2011).The importance of
external walls in energy efficiency of
buildings. Retrieved from
http://www.icoste.org/wp-
content/uploads/2011/08/The-Importance-
Of-External-Walls-In-Energy-Efficiency-
Of-Buildings.pdf
Retrieved from http://External-Walls-In-Energy-Efficiency-Of-Buildings.pdf
85
WEST AFRICAN DUST MODELING BY REGCM4: VALIDATION AND RADIATIVE
IMPACTS
N'Datchoh E. T, Konaré A and Ogunjobi K. O
Université Felix Houphouet Boigny, Abidjan, Côte d'Ivoire WASCAL, Federal University of Technology Akure, Ondo state, Nigeria
ABSTRACT
Dust particles interact with West African climate and induce changes in the radiative forcing at the
regional scale. Using the Regional Climate Model (RegCM4), the objective of this work is to assess
the radiative impacts of dust at the regional scale throughout the year. Results show that the model
better reproduced AOD in Dakar and Cape Verde stations. This suggests that the model performs
very well in reproducing dust outflow over tropical Atlantic Ocean. The radiative forcing at the Top
of Atmosphere (TOA) is minimum during June-July-August (JJA) both over the Ocean (-30 to -40
W.m-2) and land (-10 to -20 W.m-2), and maximum during December-January-February (DJF) with
transitional value during March-April-May (MAM) and September-October-November (SON).
INTRODUCTION
West Africa and indeed the entire Africa has been identified as the primary source of mineral dust
aerosols in the world (Hunees et al., 2011; Engelstaedter et al., 2006; Washington et al., 2003;
Prospero et al., 2002). These mineral dust aerosols interact with the regional climate through their
radiative impacts.
METHODOLOGY
Two sets of experiment were conducted over West African domain, one without the dust (referred to
as CTRL) and one with dust (referred to as DUST). The domain is centred on 15o N and 3o E with 295
x 197 grid points and the Grell convective scheme was used. Both experiments cover a period of 11
years, spanning from January 2000 to December 2010, with a horizontal grid spacing of 30 km and 18
sigma vertical levels. Model outputs were processed by using the post processing tools available with
the model package; daily and monthly means were computed using Climate Data Operator (CDO).
RESULTS AND DISCUSSION
RegCM4 model performance in simulating dust Aerosols Optical Depth in regard to AERONET
ground base level 2 observations as well as MODIS-TERRA, and MISR satellite observations at
several West African stations, is showed in Figure 1 and 2 for the period 2000 – 2010. Results
revealed that RegCM4 reproduced AOD variability, but with values consistently lower than
observations from AERONET, MODIS-TERRA, and MISR. In Dakar, correlation coefficients vary
from 0.65 to 0.9 with a small Centred Root Mean Square Difference (RMSD) ranging from 0.05 to
0.2. In Banizoumbou, correlation coefficients vary between 0.45 and 0.88 associated to RMSD small
values of 0.05 – 0.2. Higher correlation coefficients (higher than 0.7 to 0.92) associated to small
RMSD (from 0.05 to 0.15) are found in Cape Verde station. This suggests that the model performs
very well in reproducing dust outflow over tropical Atlantic Ocean. This is in agreement with studies
which suggested that models were able to better reproduce transatlantic dust transport and perform
better during boreal summer than winter (Kim et al., 2014; Huneeus et al., 2011).
86
Figure 1: Comparison between dust simulations AOD and observations over AERONET stations
across West Africa.
(a)
(b)
87
c)
Figure 2: Comparison of simulated and observed MISR, MODIS and AERONET AOD in some West
African AERONET stations. (a) Dakar (Senegal); (b) Banizoumbou (Niger) and (c) Cape Verde
(Cape Verde)
Also, the radiative forcing induced by dusts at the Top of Atmosphere (TOA) as simulated by
RegCM4 (Figure 3) showed that over the desert region, the forcing is close to zero during December-
January-February (DJF), March-April-May (MAM), June-July-August (JJA) and September-October-
November (SON). This may be explained by the high albedo in the region that reduces the incident
solar radiation in the short wavelengths. Also, around 15°N, the dust induce radiative forcing at the
TOA decreased to negative values, explained by the changes in surface albedo, from desert in the
North to the Sudanian savannas in the South and reduction in dust loading quantity. The radiadive
forcing at the TOA is minimum during JJA over both Ocean (-30 to -40 W/m2) and land (-10 to -20
W.m-2), with maximum during DJF while transitional value are observed during MAM and SON.
Figure 3: Solar radiative forcing (Longwave and shortwave) in W/m2 induced by dusts at the TOA .
(a) DJF, (b) MAM, (c) JJA and (d) SON.
Dust-induced radiative forcing at the surface (Figure 4) is negative at the surface during the entire
year over West Africa. The minimum of the surface radiative forcing coincided with the monsoon
season but values can reach -60 W.m-2 over the source. The negative value of the total radiative
forcing indicates that dust exerts essentially a cooling effect independently of the season over West
Africa with maximum cooling during JJA. The obtained values by RegCM4 are in the same range
with observation made by Ogunjobi and Kim (2008) over Korea during a dust outbreak. Also, JJA
radiative forcing obtained in the present work are in agreement with previous works using RegCM
such as N’Datchoh et al. (2012); Solmon et al. (2012; 2008), Malavelle et al. (2011); Konaré et al.
(2008).
88
Figure 4: Solar radiative forcing (Longwave and shortwave) in W/m2 induced by dusts at the top
surface. (a) DJF, (b) MAM, (c) JJA and (d) SON.
CONCLUSION
The RegCM4 model better reproduced AOD in Dakar and Cap Verde stations suggesting that the
model performs very well in reproducing dust outflow over tropical Atlantic Ocean. The study
revealed that dust induced cooling both at TOA and surface throughout the year.
REFERENCES
Engelstaedter, S., Tegen, I. and Washington, R., (2006), North African dust emissions and transport,
Earth-Science Reviews, 79(1-2), 73–100.
Huneeus, N., Schulz, M., Balkanski, Y., Griesfeller, J., Prospero, J., Kinne, S., Bauer, S., Boucher, O.,
Chin, M., Dentener, F., Diehl, T., Easter, R., Fillmore, D., Ghan, S., Ginoux, P., Grini, A.,
Horowitz, L., Koch, D., Krol, M. C., Landing, W., Liu, X., Mahowald, N., Miller, R.,
Morcrette, J.-J., Myhre, G., Penner, J., Perlwitz, J., Stier, P., Takemura, T., and Zender, C. S.,
(2011), Global dust model intercomparison in AeroCom phase I. Atmospheric Chemistry and
Physics, 11(15).
Kim, D., Chin, M., Yu, H., Diehl, T., Tan, Q., Kahn, R. A. and Koffi, B., (2014), Sources, sinks, and
transatlantic transport of North African dust aerosol: A multimodel analysis and comparison
with remote sensing data, Journal of Geophysical Research: Atmospheres, 119(10), 6259-
6277.
Konaré, A., Zakey, A. S., Solmon, F., Giorgi, F., Rauscher, S., Ibrah, S. and Bi, X., (2008), A regional
climate modeling study of the effect of desert dust on the West African monsoon, Journal of
Geophysical Research: Atmosphere, 113, D12.
Malavelle, F., Pont, V., Mallet, M., Solmon, F., Johnson, B., Leon, J. and Liousse, C., (2011),
Simulation of aerosol radiative effects over West Africa during DABEX and AMMA SOP-0,
Journal of Geophysical Research, 116(D8).
N'Datchoh, E. T., Konaré, A. and Silué, S., (2012), Intercontinental Transport and Climatic Impact of
Saharan and Sahelian Dust, Advances in Meteorology 2012.
Ogunjobi, K. O. and Kim, Y. J., (2008). Aerosol characteristics and surface radiative forcing
components during a dust outbreak in Gwangju, Republic of Korea, Environmental
Monitoring and Assessment, 137(1-3), 111-126.
Prospero et al., 2002 Prospero, J. M., Ginoux, P, Torres, O., Nicholson, S. E. and Gill, T. E., (2002),
Environmental characterization of global sources of atmospheric soil dust identified with the
nimbus 7 total ozone mapping spectrometer (TOMS) absorbing aerosol product, Reviews of
Geophysics, 40, 1002.
Solmon, F., Elguindi, N. and Mallet, M., (2012), Radiative and climate effects of dust over West
Africa, as simulated by a regional model, Climate Research, 52 97–113.
Solmon, F., Mallet, M., Elguindi, N., Giorgi, F., A. Zakey, and A. Konaré (2008), Dust aerosol impact
on regional precipitation over western africa, mechanisms and sensitivity to absorption
properties, Geophysical Research Letters, 35(24).
Washington, R., Todd, M., Middleton, N. J. and Goudie, A. S., (2003), Dust-Storm source areas
determined by the total ozone monitoring spectrometer and surface observations, Annals of
the Association of American Geographers, 93(2), 297.
89
EVALUATING THE PRODUCIBLE HYDROCARBON COLUMN POTENTIAL
USING WELL LOGS IN ‘SAM’ FIELD, NIGER DELTA, NIGERIA
Ojo, Bosede Taiwo
Department of Applied Geophysics, Federal University of Technology, Akure. Email
address:[email protected]
ABSTRACT
The search for economic reserves of oil and gas is the ultimate target of any petroleum exploration.
This project is aimed at identifying and delineating hydrocarbon potential zones of ‘Sam’ field to
determine its economic viability. Well logs data from three wells drilled in the onshore region of
Niger Delta utilized for the study comprise of Gamma Ray (GR), Spontaneous potential (SP), Short
Normal (SN), Long Normal (LN), Laterolog (LATL), Neutron (NEUT.) and Density (DEN) logs. Both
qualitative and quantitative well logs analyses were utilized using interactive petrophysics software.
The delineated lithologic units consist essentially of intercalated sand, shaly-sand and shale. Six
reservoir sands were delineated and the fluid contacts show gas-water contacts. Quantitatively, the
volume of shale ranges between 14.72% and 35.51%. Porosities and permeability were relatively
high, water saturation were moderately low and the highest hydrocarbon saturation was obtained in
Sand B (85.16%) from ‘Sam’ 2 well while the lowest value of 1.03% was obtained in Sand C from
‘Sam’ 2.The porosity logs showed that the field is gas prone because the density logs present higher
values than the neutron logs with the gas in place presenting high values. It was established that
reservoirs with higher hydrocarbon column (10 – 35 m) will contribute the largest percentage (72%)
of hydrocarbon during production. In conclusion, the field showed high potential for economically
viable oil and gas accumulation for future production
Keywords: Potential zone, well logs, porosity, hydrocarbon column and gas
INTRODUCTION
The ever growing demand for hydrocarbon has
given apprehension of an imminent shortage
of the resources, thus the effort to meet this
increasing demands in the future is the major
objective of all explorations. Wireline logging
is a means of gathering data from a well, in
order to understand the subsurface geology, by
lowering a measuring instrument (sonde)
down the well. When seismic data is not
available then, petrophysics can be used to
study the lateral extent of reservoirs in a field
Adeoye and Enikanselu (2009). Almost 90%
of the worlds’ total primary energy supply
comprises non-renewable energy which
includes the natural gas, oil, coal and uranium.
Oil and gas occupy a very vital position
among these energy resources, Gas was
recently adjudged to yield as much as oil
revenue and also served as raw materials to
petrochemical plants (NNPC, 2005). This
project is aimed at identifying and delineating
hydrocarbon potential zones of ‘Sam’ field to
determine its potentiality. ‘Sam’ field is
located in Niger Delta basin, in southern
Nigeria as shown in Figure 1. The Niger Delta
basin is located on the continental margin of
the Gulf of Guinea in equatorial West Africa
and lies between latitudes 4° and 7°N and
longitudes 3° and 9° E. Ejedawe (1981). It
ranks among the worlds’ most prolific
petroleum producing Tertiary deltas. Niger
Delta basin comprises of three litho-
stratigraphic units. These are from the
youngest to the oldest, the Benin, Agbada and
Akata Formations.
90
FIG. 1: Location map and base map of the
study area (Courtesy SPDC 2009).
METHODOLOGY
For this study, a base map and a suite of
geophysical Well logs data from three wells
(SAM 1, SAM 2, and SAM 3) drilled in the
onshore region of Niger Delta were utilized
and they comprise of Gamma Ray (GR),
Spontaneous potential (SP), Short Normal
(SN), Long Normal (LN), Laterolog (LATL),
Neutron (NEUT.) and Density (DEN) logs.
Both qualitative and quantitative well logs
analyses were utilized using interactive
Petrophysics software. Qualitative
interpretation method involves identification
of lithology, delineation of potential reservoir,
fluid types and correlation of sands units
across the fields using interactive petrophysics
software. The gamma ray log was used to
identify the lithology. Fluid type identification
was done using resistivity log response,
density log, neutron porosity log and
calculated values of water saturation.
Reservoir sands which contain hydrocarbon or
fresh water are characterized by their
resistivity.
However a more specific identification of fluid
type was achieved using crossover relationship
between density and Neutron logs. Amigun
and Odole (2013). Quantitative interpretation
method involves computation of petrophysical
parameters to characterize the six reservoir
sand units across the wells. The Volume of
Shale (Vsh), Formation Factor (F) Water
Saturation (Sw), Hydrocarbon Saturation (Sh),
Residual Hydrocarbon Saturation (Shr), Water
Saturation of the flushed zone (Sxo),
Calculated Porosity (Ø), Irreducible Water
Saturation (Swirr), Bulk Volume of Oil
(BVO),Bulk Volume Of Water (BVW),
Movable oil Saturation (MOS), Movable
Hydrocarbon Index (MHI) and Permeability
(K) were computed for these reservoir sand
units.
Manual grading of the hydrocarbon column
height for potential reservoirs were conducted
to establish their percentages.
RESULT AND DISCUSSION
From the readings of the Gamma ray log, the
lithologic unit revealed intercalations of sand
and shale sequences down each of the three
wells. Six reservoir zones delineated were
SAND A, SAND B, SAND C, SAND D,
SAND E and SAND F respectively as in
figure 2.
The volume of shale in the delineated
reservoirs were estimated and their values
ranges within 14.72% and 35.51% making the
sand units delineated a shaly sand unit since
the volume of shale is between 10% and 35
% for shaly sand units
The average porosity values obtained for the
sand units identified were high. It ranges
91
between 35% and 45%. It shows the reservoir
is highly porous, which is good for
accumulation of hydrocarbon. Based on the
calculated water saturation, hydrocarbon
saturation and formation factor, it is clear that
about 35% of the fluid in the hydrocarbon
bearing sand consist of interstitial water while
about 65% of the fluid in the hydrocarbon
bearing sand consists of hydrocarbon.
The relative permeability to water (Krw)
ranges from 0.001to 1.21 and most of the
reservoirs have low relative permeability to
water which implies that less water production
is expected from the reservoir. The relative
permeability to oil (Kro) was quite high in
reservoirs sands with high hydrocarbon
saturation, which implies that hydrocarbon is
moveable in this reservoir sand (Reijer et al
(1996).
The absolute permeability is generally high
across all the wells in the studied area. The
movable hydrocarbon Index of all the
reservoirs studied are generally less than 0.7,
which further confirmed that the hydrocarbon
in the reservoirs are movable.
Total number of hydrocarbon bearing
reservoirs delineated from all the well logs are
eighteen in number. The histogram depicting
the distribution of hydrocarbon column height
(figure 3) showed that out of 18 mapped
reservoirs, 28% have oil column height
ranging from 5m-10m, 11% has 10m -15m,
22% has 16m -20m, 6% has 21m-25m, 22%
has 26m-30m and 11% has 31m-
35m.(Table1). It can be established from this
result that reservoirs with higher hydrocarbon
column (10m-35m) will contribute the largest
percentage (72%) of hydrocarbon during
production.
Fig. 2: Lateral correlation across the
three wells
TABLE 1: Data of hydrocarbon height of
‘Sam’ field.
Hydrocarbon
Column
Height (m)
Number
Of
Reservoir
Percentage
(%)
1-5 0 0
6-10 5 28
11-15 2 11
16-20 4 22
21-25 1 6
26-30 4 22
31-35 2 11
92
LEGEND
PERCENTAGE (%)
HYDROCARBON
COLUMN HEIGHT (m)
FIG. 3: Histogram showing
the hydrocarbon column
height of the reservoirs
0%
28%
11%
22%
6%
22%
11%
0-5m 5-10m 10-15m 15-20m 20-25m 25-30m 30-35m
Nu
mb
er
of
rese
rvo
ir
Hydrocarbon column height (m)
Percentage
93
CONCLUSION
The information extracted from the well log analysis in the delineation of prospect area on ‘Sam’ field
revealed that the field is gas prone. The hydrocarbon column height is relatively high and the
hydrocarbon is movable. Generally, hydrocarbon potential of the field is relatively high and the field
shows a lot of potential for oil and gas accumulation for future exploration.
REFRENCES
Adeoye, T.O and Enikanselu, P (2009): Reservoir mapping and volumetric analysis using seismic and
well data. Ocean Journal of Applied Science, Vol. 2, Issue 4. pp 66-67
Amigun, O.J and Odole, O.A (2013): Petrophysical evaluation for reservoir characterization of SEYI
oil field, Niger Delta. International Journal of Innovation and Applied Studies. Vol. 3 No 3. pp765-773.
Asquith, G and D. Krygowski, (2004):
Relationships of Well Log Interpretation
in Basic Well Log Analysis: AAPG
Methods in Exploration 16,239p
Ejedawe, J.E., (1981). Patterns of incidence of oil reserves in Niger Delta Basin:American Association
of Petroleum Geologists, v. 65, p. 1574-1585.
NNPC (2005): Overview of the Nigeria Petroleum Industry and opportunities for Investment. Paper
presented at the 18th World Petroleum Congress, Johannesburg, South Africa, September,
pp.25-29.
Reijer, T. J. A., Petters, S. W. and Nwajide, C. S., (1996): The Niger Delta Basin. In: Reijers T. J. A.
(eds), Selected Chapters on Geology: Sedimentary geology and sequence stratigraphy in Nigeria and
three case studies and a field guide, shell Petroleum Development Company, Warri, Nigeria, pp.105-114.
94
STRUCTURAL EVOLUTION, KINEMATICS AND DEFORMATION CONDITIONS OF THE
IWARAJA SHEAR ZONE, SOUTHWESTERN NIGERIA
C.T. Okonkwo and B. Adeoti
Department of Applied Geology, Federal University of Technology, Akure
ABSTRACT
The Iwaraja area is the eastern flank of the Ilesha Schist Belt, southwestern Nigeria. The basement rocks
of Iwaraja area comprises quartzites and quartz-schists of the Effon Psammite Formation. The area is
also underlain by quartz-mica schists, biotite schists, migmatitic gneiss, granitic gneiss, late and post-
tectonic granitic rocks including pegmatites. The metamorphic basement rocks had been subjected to
polyphase deformations. A major, late, NNE-SSW trending sub-vertical shear zone (the Iwaraja Shear
Zone) divides the area into two. Deformation within the shear zone involved the mylonitisation of the
affected rocks especially the granite gneiss ranging in intensity from protomylonite to ultramylonite and
took place in several stages and was associated with retrograde mineralogical evolution from
amphibolite facies to greenschist facies. Shear related late folds of pegmatite dyke in the mylonite show
typical geometry of synthetic folds characterized by a thin short limb which recorded changes in the
shape of the folded layer during progressive shearing. Kinematic indicators such as ơ-type
porphyroclasts and fractured feldspars indicate dextral shear sense. The sub-vertical dip of the S2 shear
fabric and the sub-horizontal L2 lineation also indicated that the Iwaraja Shear Zone had a transcurrent
displacement during Neoproterozoic times.
Key words: Iwaraja Shear zone, Shear, Transcurrent displacement, kinematic indicator
INTRODUCTION AND GEOLOGICAL
SETTING
Major shear zones have been recognized as
important elements of crustal deformation
during orogenesis involving collisional,
transcurrent or oblique (transpressive)
displacements. The nature of activity along these
shear zones generally evolve with orogenic
development going from dominantly convergent
to dominantly transcurrent at the later period.
Several Neoproterozoic orogenic belts are
characterized by several of such shear zones
trending generally parallel to their elongation.
Regional scale, steep, generally north-south
trending shear zones have been recognised in the
western part of the Nigerian basement complex
(Ajibade, 1982; Grant, 1978; Caby, 1989;
Odeyemi, 1993; Anifowose et al., 2007;
Okonkwo et al. 2014). These shear zones have
been traced north wards to and correlated with
those of the Central Hoggar (Caby, 1989, 2003).
These zones are marked by mylonites and
cataclasites produced by the shearing of the
rocks at different crustal levels (temperatures
and confining pressures) and activities of the
fluid phase.
One of these is the Ifewara Shear zone in
southwestern Nigeria. This is 200km long and
about 2km wide structure separating dominantly
amphibolite- mica schist complex in the west
from dominantly othogneissic- quartzite
complex in the east. The major shear zone has
an easterly splay called the Iwaraja Shear zone
(Fig.1).
95
Fig.1: The geological map of Iwaraja area.
Since its recognition, the structural evolution
and nature of displacement in this shear zone has
been the subject of different interpretations.
Some workers have inferred a wholly
transcurrent motion while others have suggested
thrust displacement. This paper seeks to
elucidate the structural evolution of the Iwaraja
shear zone and thus constrain its kinematic
evolution.
The basement rocks of Iwaraja area comprising
quartzites and quartz-schists of the Effon
Psammite Formation, quartz-mica schists, biotite
schists, migmatitic gneiss, granitic gneiss, late
and Post-tectonic granitic rocks including
pegmatites. The metamorphic rocks have been
subjected to polyphase deformation, D1
structures include schistosity in the
metasediments as well as gneissic foliation
including banding in the migmatitic gneiss and
96
the granitic gneiss (S1) and tight to isoclinal
minor folds. These were succeeded by localized
intense deformation in the shear zone D2 which
gave rise to the S2 shear fabrics as well as shear-
related folds of pegmatite dykes in the shear
zone.
Shear Zone Deformation
A major, late, NNE-SSW trending, sub-vertical
shear zone, the Iwaraja Shear Zone, divides the
area into two. Deformation within the shear
zone involved the mylonitisation of the affected
rocks especially the granite gneiss ranging in
intensity from protomylonite to ultramylonite
and took place in several stages and was
associated with retrograde mineralogical
evolution from amphibolite facies to greenschist
facies.
The primary mineral composition of the
unsheared granitic gneis is essentially perthitic
microcline, quartz, plagioclase, biotite with
some hornblende. Within the shear zone the
granitic gneiss is transformed into a mylonite
made up of relict porphyroclasts of K-feldspar
within a very fine-grained matrix of feldspars,
biotite, chlorite, quartz, sphene, ore, epidote and
sericite. The deformation intensity increases to
ultramylonitic locally characterized by few
remnant, rounded porphyroclasts of feldspars in
very fine-grained groundmass of chlorite, quartz,
epidote, ore, and elongate quartz ribbons parallel
to the foliation. This fabric is locally overgrown
by late green biotite grains.
Microcline-perthite porphyroclasts contain
intracrystalline fractures with the fragments
being displaced obliquely to the mylonitic
foliation indicating rotation of these
porphyroclasts under non-coaxial strain with a
dextral sense of shear.
Shear zone-related folds of a pegmatite dyke in
the mylonite show a range varying from early
folds to late folds. The early folds were
produced by rotation and shearing of the
rheologically stiffer dyke are close to tight folds
with westerly vergence. The late folds produced
at higher strains flank the early folds and possess
the typical geometry of synthetic folds
characterized a thinned short limb and record
changes in the geometry of the folded layer
during progressive shearing.
Kinematics
Several kinematic indicators occur in the
mylonites; they range from ơ-type
porphyroclasts to fractured and displaced
feldspar porphyroclasts which indicate a dextral
sense of shear. The sub-vertical dip of the S2
shear fabric and the sub-horizontal L2 lineation
also indicate that the Iwaraja Shear Zone had a
transcurrent displacement.
CONCLUSIONS
The Iwaraja Shear Zone is part of the major
shear system traceable from SW to NW Nigeria
which is traceable to Neoproterozoic Shear
zones of Central Hoggar Belt (Caby 2001, Caby
and Boesse 2001) in the Trans-Saharan Mobile
Belt which played a major role in the final
amalgamation of the different terranes during
the closing stages of the Pan-African Orogeny.
REFERENCES
Ajibade, A. C. (1982). The cataclastic rocks of
the Zungeru region and tectonic significance.
Journal of Mining and Geology, 18, 29-41.
Anifowose, A.Y.B., Odeyemi, I.B. & Borode,
A.M. (2007). The tectonic significance of the
Ifewara-Zungeru Megastructure in Nigeria, In
Proceedings of the 1st International Workshop
on Geodesy and Geodynamics, Centre for
Geodesy and Geodynamics, Toro, Nigeria, 17-
28.
Caby, R. (1989). Precambrian terranes of Benin-
Nigeria and northeast Brazil and the Late
Proterozoic South Atlantic fit. Geological
Society of America Special Paper 230, 145-158.
97
Caby, R. (2003). Terrane assembly and geodynamic evolution of central-western Hoggar: a synthesis.
Journal of African Earth Sciences, 37, 133-159.
Caby, R.& Boesse, J.M. (2001). Pan-African nappe system in southwest Nigeria: the Ife-Ilesha schist belt.
Journal of African Earth Sciences, 33, 211-225.
Grant, N.K (1978). Structural distinction between a metasedimentary cover and an underlying basement
in the 600 my old Pan-African domain of northwestern Nigeria. Geological Society of America Bulletin,
89, 50-58.
Odeyemi, I.B. 1993. A comparative study of remote sensing images of the structure of the Okemesi Fold
Belt. ITC Journal,1, 77-81.
Okonkwo, C.T., Adetunji, A. and Folorunso, I.O. 2014. Microstructural and Mineralogical Evolution of
the Oke Awon Shear Zone in the Jebba Area, S.W. Nigeria. The Pacific Joiurnal of Science and
Technology, 15, 335-344.
98
FORAMINIFERA AND NANNOFOSSIL BIOSTRATIGRAPHIC SIGNIFICANCE OF NGOR – 1
WELL, BORNU BASIN
P. S. Ola and A. O. Agbaje
Department of Applied Geology,
Federal University of Technology, Akure, Nigeria
ABSTRACT
Two hundred and thirty samples retrieved within a section of Ngor – 1 well (Depth 460 - 2745 m) were
subjected to foraminiferal and nannofossils studies for its biostratigraphic significance and relationship
with selected Cretaceous basins in the Tropic. A total count of one thousand two hundred and sixty six
(1266) species of foraminifera made up of only four (4) planktonic and eleven (11) arenaceous benthic
species were recovered. The section studied is totally devoid of nannofossils. Only a spot occurrence of
Heterohelix globulosa was recorded and used to define the section of the well that is assumed not
younger than the late Maastrichtian or older than the Campanian and an informal foraminiferal zone:
Globotruncanita elevata – Globotruncana aegyptiaca. All the recovered forms have been described from
several Cretaceous stratigraphic units in Nigeria including the Cenomanian to Lower Turonian
Odukpani Formation, Eze-Aku and Awgu Formations of Turonian to Coniacian ages, Nkalagu
Formation of Cenomanian to Coniacian age and Nkporo Shale. Elsewhere it occurs in Campanian to
Maaatrichtian of western Gulf coastal plain U.S.A; and Campanian and Maastrichtian of South America.
Based largely on benthic foraminifera species the sequences penetrated by the well were designated into
continental, littoral (deltaic) and open marine (outer neritic) environments of deposition. Generally, the
low diversity of the benthic and planktic foraminiferal assemblages as well as the total absence of
nannofossils in Ngor-1 well is indicative of a shallow marine paleoenvironmental condition of deposition
in the basin.
Key words: Bornu Basin, stratigraphy, Cretaceous, G. desyptiaca,
INTRODUCTION
Ngor – 1 well is located at the extreme south western part of the Bornu Basin. This portion of the basin
falls within the probable corridor linking the Bornu Basin with the Benue Trough. Unlike the Benue
Trough, biostratigraphic study of the Cretaceous/Tertiary sediments of Bornu Basin has attracted only few
published research work, which include: Olugbemiro, 1997; Hamza et al., 2002; and Ola-Buraimoh, 2011
The objectives of this work is to reconstruct the paleoenvironmental history of the studied section of
Ngor-1 well using its fauna content for environmental reconstruction and correlation with some selected
basin in the tropic..
Background Geology of the Bornu Basin
The Nigerian portion of the Chad Basin is herein described as the Bornu Basin. Detailed mechanism of
the evolution of the Chad Basin appears speculative as various models have been proposed (Genik 1993,
Fairhead 2013). The sedimentary fill of the basin, which span over Cretaceous and Tertiary have been
divided stratigraphically into six (Fig. 2).
MATERIALS AND METHOD
A total of two hundred and thirty ditch-cutting samples obtained between depths 460 and 2745 m in
Ngor-1 well, in the Bornu Basin were used for this study. The standard laboratory techniques
99
100
101
for retrieving foraminiferal and nannofossils were followed.The textural and lithologic characteristics of
all the samples were studied.
RESULTS
Litholog and Electrofaies Interpretation The sequences penetrated within this interval could be
classified into 10 lithological units (Fig. 3).
Foraminifera and nannofossils: Sixteen (16) foraminifera species were recovered from the
studied samples. Four (4) of these were planktonic species while twelve (12) were arenaceous benthic
species. The samples were devoid of calcareous benthonic species while ostracod species were also
recovered. The stratigraphic distribution, age and paleobathymetric ranges of the species are presented in
a Stratabug spreadsheet (Fig. 4).
DISCUSSION
All the recovered forms have been described from several Cretaceous stratigraphic units in Nigeria, which
include the Cenomanian to Lower Turonian Odukpani Formation, Eze-Aku and Awgu Formations of
Turonian to Coniacian ages, Nkalagu Formation of Cenomanian to Coniacian age and Nkporo Shale.
Elsewhere it occurs in Campanian to Maaatrichtian of western Gulf coastal plain U.S.A; Campanian and
Maastrichtian of South America.
Planktonic Foraminifera Zone.: One planktonic foraminifera zone (G.aesyptiaca – G.elevata Zone -
spot occurrence of Heterohelix globulosa at 1650 m which suggests an age that is not younger than Late
Maastrichtian and not older than Early Campanian) and an indeterminate zone were recognized based on
the planktonic foraminiferal zonation scheme of Caron (1985).
Foraminiferal Paleoecology: The foraminiferal assemblages of Ngor-1 well consist mainly of
agglutinated benthic species. The calcareous planktic species are of lesser abundance except Heterohelix
navaroensis. Both the agglutinated and calcareous foraminiferal assemblages show low species diversity
and differ from normal marine faunas which consist predominantly of calcareous ones. Development of
faunas consisting of entirely or dominantly of agglutinated form is attributed to brackish environments or
to stagnant conditions (Lofaldli and Nagy, 1980; Nagy et al., 1988; 1990). The low diversity of the
benthic and planktic foraminiferal assemblages from the Ngor-1 well is indicative of a shallow marine
paleoenvironment.
CONCLUSION.
The section of Ngor 1 well studied composed wholly of shale, sandy mudstone and sandstone sequences.
The foraminiferal assemblages of Ngor-1 well consist mainly of agglutinated benthic species. No single
nannofossils was recovered in this study. These suggest a shallow marine paleoenvironmental condition
of deposition in the basin.
102
IMPACT OF TRANSPORTATION ON THE ENVIRONMENT
Olaogbebikan Jimoh Eniola
Transport Management Technology Department, School of Management Technology, Federal
University of Technology, PMB 704, Akure, Nigeria
E-mail of the corresponding author: [email protected]
ABSTRACT
Transportation consumes a lot of energy, for example an average car during its life time travels some
160,934.4 Kilometers, consuming over 13,638.27 Liters of petrol and over 227.3045 Liters of oil and
discharge many of this to the environment, the estimate for Ship as well as Aircraft are also high.
Therefore the welfare and wellbeing of the environment is based on the efficiency with which energy
resources are deployed in the transport sector. The release of carbon monoxide to the environment
destroy the environment, the carcinogenic gases released also caused health hazard killing the forest and
causes crop loses, it degrades marine life and also the major man made contributors to the greenhouse
effect and the noise generated increase the decibel level in humans which can results into deafness,
environmental degradation also results from the operation of transportation hence it is adjudged one of
the worst defilers of the environment.
Proactive environmental management in all the transport sectors will reduce and mitigate the impact of
transportation on the environment. Also the negative impact of transportation on the environment can
be addressed through the promotion of fuel efficiency, introduction of efficient fuel pricing, reduction of
congestion and environmental impact assessment of transport projects. Adaptation and mitigation
measures must be effectively implemented if the impact of transportation on the environment is to be
addressed, the key players in the transport sector, government agencies, transport service users must
synergize to effectively monitor their operations in order to ensure a sustainable, clean and healthy
environment.
Key Words: Transportation, Environment, Sustainable, Energy and Management
103
INTRODUCTION
Transportation plays a major role in human livability as the existence of human being is tied to
transportation. It affects every aspect of human existence hence transport and environment is
paradoxical in nature as it conveys substantial socio economic benefits. In spites of the attendance
benefits derived from transportation it is adjudged the worst destroyer of the environment because
transport activities are associated with growing level of externalities. Transport activities which cut
across all modes of transport has a deleterious effects on the environment.
The question that comes to mind as this important subject is being considered is what is environment?
Environment is defined as all the external factors influencing the life and activities of people, plant
and animal hence transport impact affects people plant and animal inhabiting the environment.
Public funds goes into financing transport activities but not much has been plough back positively to
the environment in order to make it habitable for the people. It is as a result of this that Bruntland in
1948 came out with the idea of Environmental Sustainability that the environment in which transport
business is being transacted needs to be preserved for the future generation so that the product of
transportation will not render the environment uninhabitable for the human race. The users of
transport infrastructure must endeavor to pay for it so that environment will be kept safe for human `
existence. The opportunity cost of transport operation should be considered by the
responsible authority and the transport users be made to offset this cost.
The activities of transport is responsible for ingesting harmful gases to the environment such as
Carbon monoxide, Carbon dioxide, Nitrogen oxide, Sulphur dioxide , Particulate matters. The impact
of these gases on the environment is great, it negatively affects every aspect of the environment that is
human being, plant and animals are not left out.
This study seek to examine the impact of transportation on air quality, water quality, noise,
Biodiversity and land take, the impact of climate change on the environment will be explored.
METHODOLOGY
These studies seek to carry out an in-depth exploration of the impact of transportation on the
environment. It seeks to carry out an empirical study of the impact of transportation on the
environment. In-depth literature review on this subject will be adopted in order to determine the gap
in research in this area especially in developing countries like Nigeria. Secondary data were gathered
and assessments were done qualitatively. It is noteworthy that transportation is regarded as the worst
defilers of the environment; therefore various aspect of the environment which transportation affects
will be explored.
RESULT AND DISCUSSION
It is expected that transportation contributes negatively to the environment. The impacts of all
transport modes on the environment are negative. Maritime transportation ingest fossil fuel to the
ocean thereby destroying the fish and other marine organism in the marine environment, ship
ballasting leads to the dislocation or disruptions of the ecosystem as strange species of marine
organism are introduces from one location to other marine environment, The survival of marine
104
organism is negatively affected by the dumping of waste material to the ocean. The noise pollution
produced by land transport is highly unbearable the decibel levels in human has been raised which
affect the occupant of such environment, the affinity of this transport mode for fuel consumption had
led to the release of noxious gases to the environment thereby defiling it. The degradation of land due
to the activities of motor garages, mechanic repair shops are high, also water pollution result because
all the fuels released from mechanic workshop and car washes are introduced to the nearby rivers or
ocean which eventually pollutes it. The noise generated by locomotives as well as vibration thereby is
very high. The noise generated by air transportation is very high and unbearable by the occupant of
such environment, it increase blood pressure as well as increase annoyance, airport environment is
not a conducive environment for human habitation as a result of this.
This research work proffers solution to all this problems. The regulatory bodies should come up with
policy framework that enhances green transportation thereby putting the activities of all transport
operators in proper check. The polluters pay all as obtained in the developed countries should be
adopted whereby the users of transportation or the operators should be made to pay for the
defilement of the environment, the money realized from such should be plough back to the
environment in order to clean it up. Petroleum tax should be introduced as well as various policy
measures that discourage private motoring. Environmental protection initiatives should start from the
local level and the responsible authorities must ensure proper execution.
REFERENCES
Eyring, V., et al., Transport impacts on atmosphere and climate: Shipping, Atmospheric Environment
(2009), doi:10.1016/j.atmosenv. 2009.04.059 University of New Brunswick Canada pg.428, 436
www.intechopen.com
Jean-Paul Rodrigue (2013) The Geography of transport system, New York Routledge
Olaogbebikan Jimoh Eniola 2014: The impact of Transportation on climate change. A proceeding of
the conference presentation at School of Science Federal University of Technology, Akure
Sunday Olayinka Oyedepo (2012) Energy and sustainable development in Nigeria The way forward
Tina Hodges 2011, Flooded Bus, Barns and Buckled rails. Program Analyst Office Budget and
Policy Federal Transit Administration U.S. Department of Transportation 1200 New Jersey Avenue,
SE Washington, DC 20590
U.S. Environmental Protection Agency, 2005. Inventory of U.S. Greenhouse Gas Emissions and
Sinks: 1990–2003. Washington, DC, Table 2-9.
Weart, Spencer (2008), "The Carbon Dioxide Greenhouse Effect". The Discovery of Global
Warming, American Institute of Physics
105
MAGNETIC CHARACTERISATION OF ROCKS UNDERLYING FUTA CAMPUS, SOUTH-
WESTERN NIGERIA
Olayanju, G. M., and Ojo, A. O.
Department of Applied Geophysics, Federal University of Technology, Akure, Nigeria.
Department of Marine Geosciences, Universität Bremen, Bremen,
Germany.
E-mails: [email protected]; [email protected]
Corresponding Author: Olayanju, G. M.; Mobile: (+234) 8035923017; E-mail:
ABSTRACT
The Federal University of Technology, Akure Campus is predominantly underlain by the Migmatite-
gneiss-quartzite complex of the West African Basement Rocks, which forms part of the Pan-African
mobile belt. Geo-magnetic characterisation of the underlying rocks was conducted in order to
determine the rock boundaries and geologic features within the near surface and subsurface areas of
the Campus. Both qualitative and quantitative interpretations of total magnetic intensity data obtained
in the area yielded results in terms of different rock units, linear magnetic fabrics, subsurface features
and depth to basement of the rocks. On the basis of magnetic response, four rocks units including
Granite, Migmatite gneiss, Charnokite and Quartzite were delineated, with varying degree of fabrics’
alterations. Depth-to-bedrock in the Campus varies from 0 to 98.5 m, while depth to fracture/fault in
the area falls between 0.1 m and 149.6 m.
Key Words: Geo-magnetic characterisation, depth-to-bedrock, rock fabric, total magnetic intensity,
magnetic response
1. INTRODUCTION
The magnetic geophysical method can be
employed as a tool in differentiating rock types
based on the magnetic mineral contents of the
various rock types forming the Earth materials.
Most geophysical methods can be used in
delineating rock boundaries, contacts and
internal structures of subsurface geology. In most
cases, these geophysical methods are non-
invasive, such as magnetic, gravity, electrical
resistivity and electromagnetic methods.
Magnetic surveying is used to investigate the
subsurface geology of an area by detecting
magnetic anomalies within the Earth's magnetic
field, which are caused by the magnetic
properties of the underlying rocks. Despite the
fact that most rock-forming minerals are
nonmagnetic, few rock types contain sufficient
amounts of magnetic minerals which can impact
magnetism to their host rock and thus produce
detectable magnetic anomalies. Geological
contacts or rock boundaries could be defined as
the meeting point between two or more rock
types depending on the geologic setting
(Oyawoye, 1972).
This paper gives details of geologic mapping of
The Federal University of Technology, Akure
Campus through comprehensive ground
magnetic survey in order to determine the rock
boundaries and geologic features within the near
surface and subsurface areas of the Campus.
Site Description
The Federal University of Technology, Akure is
located in the North-western part of the ancient
city of Akure, south-western Nigeria and has a
land mass of about 6 km2. It is situated within
latitude 7° 07’ N to 7° 08' N and longitude 5° 08'
E to 5° 12' E (Figure 1). The study area is
underline by crystalline rock of the Precambrian
basement complex of the southern Nigeria
(Rahaman, 1988). There are four major different
rock units in the area as shown in Figure 1,
comprising of migmatite-gneiss, quartzite,
charnokite, and granite.
106
Figure 1: Local Geology map of the Study Area
(After Kareem, 1995)
2. MATERIALS AND METHODS
The magnetic survey conducted within the entire
Campus involves total field intensity
measurements with the aid of the GSM 19T
Proton Precession (PPM) magnetometer.
GARMIN 72 Global Positioning System (GPS)
was used for recording the geographic location of
data position.
The whole Campus was demarcated into blocks,
while each block was covered with a base station
established within and tied to a common base
station for drift monitoring through the entire
period of data collection. Field observation of
rock types was also carried out as the magnetic
survey progressed. Each rock sample were
carefully observed on the field, identified and
located on the base map in order to update
information on the rock types in the area and
enhance geophysical interpretation of the
acquired magnetic data. Further processing of the
ground magnetic data involved removal of
variations in the Earth’s main field with latitude,
longitude and time by removing the International
Geomagnetic Reference Field (IGRF) resulting
in the anomaly separation.
The interpretation of residual anomaly map
generated involved both qualitative and
quantitative interpretations which provide useful
information on magnetic characteristics of
different rock units, linear magnetic fabrics,
subsurface features and depth to basement of the
rocks. A quick estimate of depth-to-bedrock was
carried out using the straight-slope and half-slope
lengths and two dimensional (2D) Euler
inversions of the residual anomaly profiles along
sections drawn across the contoured magnetic
field intensity map. The solutions from the Euler
de-convolution aid in the structural interpretation
for delineation of rock boundaries, linear features
(dykes, faults or contacts) and depth- to- the
basement in the study area (Panisova et al.,
2013). Details of application of Euler
Deconvolution to geopotential fields have been
documented by several authors (Oruc and Selim,
2011; Dewangan et al., 2007). Euler expression
for a homogenous 3 dimensional geopotential
field of degree n has the form:
𝑓(𝑡𝑥, 𝑡𝑦, 𝑡𝑧) = 𝑡𝑛𝑓(𝑥, 𝑦, 𝑧) (1) Potential fields which also satisfy the equation
below known as Euler equation are referred to as
harmonic functions:
𝑥𝜕𝑓
𝜕𝑥+ 𝑦
𝜕𝑓
𝜕𝑦+ 𝑧
𝜕𝑓
𝜕𝑧= 𝑛𝑓 (2)
The usual Euler’s equation is re-arranged in the
form:
(𝑥 − 𝑥0)𝜕𝑇
𝜕𝑥+ (𝑦 − 𝑦0)
𝜕𝑇
𝜕𝑦+ (𝑧 − 𝑧0)
𝜕𝑇
𝜕𝑧= 𝑁(𝐵 − 𝑇)
(3) where (x0, y0, z0) is the position of a source
whose total magnetic field T is detected at (x, y,
z). B is the regional value of the total field and N
is the structural index equivalent to –n in the
Euler’s equation.
Equation 3 can be expressed for a 2D Euler
problem as:
(𝑥 − 𝑥0)𝜕𝑇
𝜕𝑥+ (𝑦 − 𝑦0)
𝜕𝑇
𝜕𝑦= 𝑁(𝐵 − 𝑇) (4)
3. RESULTS
Figure 2 shows the corrected and enhanced total
field intensity map over the study area, while
Figure 3 shows the superimposition of the
residual anomaly map on the existing geologic
map of the study area. Typical structural models
from the results of the Euler de-convolution of
the residual field in the area using EULDEP
software developed at University of
Witwatersrand, South Africa (Durrheim and
Cooper, 1998) is shown in Figures 4
107
Figure 2: Total magnetic field intensity map over
the study area.
Figure 3: Superposition of residual magnetic
intensity field on the geologic map of the
area.
Figure 4: 2D forward modeling showing
subsurface geologic section along cross-
section AB. 4. DISCUSSION
Magnetic Structures
From Figure 3, the comparison of the produced
geologic map of the area from the earlier work of
Kareem (1995) and direct field observation
provide opportunity to relate the magnetic
textural imprints or alteration of rock fabrics in
the area, which is reflection of variation in the
rocks’ susceptibilities.
Characteristic magnetic anomalies from the
residual anomaly map correlated with the field
observation of the various rock units and existing
geologic map of the study area revealed magnetic
domains recognised to be coincided with the
existing rock units in the area.
The rocks underlain the area have great imprints
of several faulting/fracturing occurring as linear
features. Magnetic anomaly pattern reflects
relative low magnetic amplitude in the range of -
800 to 500 nT as shown in Figure 3 and Table 1.
Table 1: Characteristic magnetic anomaly of
rocks in the study area.
S/N *Residual
anomaly
amplitude
Rock type
1 < -200 nT Charnokite
2 -200 – 0 nT Granite
3. 0 – 100 nT Migmatite-
gniess
4. 100 – 500 nT Quartzite *anomaly amplitude is relative and negative
values do not translate to negative magnetic
susceptibility
Strong magnetic anomalies are associated with
rocks containing magnetite, pyrrhotite, chromite
or ilmenite, while felsic rocks (such as granite or
rhyollite) and most sedimentary rocks cause
distinct magnetic lows (Ako et al., 2004).
Quartzite and migmatite-gneiss show relatively
high magnetic amplitudes in comparison with
low amplitudes observed over granite and
charnokite. High amplitudes of magnetic
anomalies over quartzite and migmatite-gniess
can be attributed to their metamorphism
(Neawsuparp et al., 2005).
For most structural interpretation, anomaly
sources can be adequately represented by
dyke-like model (SI of 2), while structural
index of 1 was used for contact/fault models.
Average main earth magnetic field intensity
33,069 nT, inclination -11.17 and declination -
2.21 obtained from the IGRF values over the area
were used as input to the Euler inversion
software for the depth and source location
determination.
108
W-E Profiles
Anomaly amplitude along five profiles made
along W-E directions varies from -713 – 439 nT,
while depth to the bedrock along these profiles
varies between 0.84 m and 112.9 m.
Along these profiles series of Euler solutions for
contact model show the position and depth to the
magnetic lineaments recognized as basement
fractures and faults, while the location and depth
to bedrock of the dyke model coincide with the
top of the basement rock along the profiles.
Depth to the lineaments (fracture/fault) along
these profiles varies from 0.8 – 149.6m, while
depth-to-bedrock ranges between 0.4m and
50.1m.
NW-SE Profiles
Along two NW-SE profiles across the study area,
the anomaly amplitude ranges from -425 – 311
nT, while depth-to-bedrock was estimated to be
between 0 m and 98.5 m. Depth to the position of
lineaments (fracture/fault) vary from 0.1 – 112.9
m. In a similar pattern to the W-E profiles, some
recognized faults/fractures are located at the rock
contacts. From the results of magnetic survey,
modified geological map (Figure 56) was
generated on the basis of the observed magnetic
textural imprints of the various rock types, which
is reflection of variation in the rocks’
susceptibilities.
5. CONCLUSIONS
On the basis of the magnetic characteristics of
the various rock units as shown in Table 1 and
the delineated geologic sections from the Euler
inversion of the magnetic data, a modified
geologic map of FUTA was produced.
Figure 5: Modified geologic map of FUTA
Campus.
Position and depth to basement rocks and
locations of contacts, fractures/faults within the
Federal University of Technology, Akure
Campus have been determined from the Total
Magnetic Intensity (TMI) over the area.
Recognized rock types within the Campus are
Charnokite, Granite, Migmatite and Quartzite;
each of the rock types gives different response to
magnetic measurement. The residual magnetic
value of the rocks ranges from ranges for -800 to
500 nT, with Charnokite having lowest magnetic
response (consequently lowest magnetic
susceptibility), while the high magnetic
anomalies amplitudes observed over quartzite
and migmatite-gniess can be attributed to their
level of metamorphism.
From the magnetic interpretation results, the
basement rocks delineated show intense
weathering of the basement rock within the
Campus as well as high degree of fracturing and
faulting as observed on the magnetic structural
sections. The rocks in this area are competent for
most structural infrastructures; however there is a
need to carry detailed geophysical survey in most
areas in order to avoid locating structures on
some of the linear features which are likely to be
fractures or faults. In addition, position of most
deep fractures in the area will be of hydro-
geologic significance to groundwater
development of the Campus.
REFERENCES
Ako, B.D., Ojo, S.B., Okereke, C.S., Fieberge,
F.C., Ajayi, T.R., Adepelumi, A.A.,
Afolayan, J.F., Afolabi, O., and Ogunnusi,
H.O. (2004): Some observation from
gravity/magnetic data interpretation of the
Niger Delta. Nigerian Association of
Petroleum Explorationists, vol. 17, No. , pp
1-21.
Durrheim, R. J. and Cooper, G.R.J. (1998):
EULDEP: A program for the Euler
deconvolution of magnetic and gravity data.
Computer & Geosciences, Vol. 24, No. 6,
pp. 545-550.
Kareem, W. A. (1995): Geological mapping and
geophysical investigation of FUTA mini-
Campus. Unpublished M. Tech. Thesis,
Department of Applied Geophysics, FUTA.
Neawsuparp K., Charusiri, P., and Meyers, J.
(2005): New Processing of Airborne
Magnetic and Electromagnetic Data and
Interpretation for Subsurface Structures in
the Loei Area, Northeastern Thailand.
109
ScienceAsia , Vol. 31, pp. 2813-298: doi:
10.2306/scienceasia1513-1874.2005.31.283
Oruc, B., and Selim, H. H. (2011): Interpretation of
magnetic data in the Sinop area of Mid Black
Sea, Turkey, using tilt derivative, Euler
deconvolution, and discrete wavelet transform.
Journal of Applied Geophysics. Vol. 74, pp 194–
204. doi:10.1016.
Oyawoye, M. O. (1972): The Basement Complex of
Nigeria. In : African Geology 1970 edition.
Dessauvagie and Whiteman
(editors). Geol. Dept. Univ. Ibadan. Nigeria. pp 67-99.
Panisova, J., Frastia, M., Wunderlich., T., Pasteka., R., and Kusnirák., D. (2013): Microgravity and Ground-penetrating
Radar Investigations of Subsurface Features at the St Catherine’s Monastery, Slovakia. Archaeological Prospection,
Vol. 20, pp. 163–174. dOI: 10.1002/arp.1450
Rahaman, M.A. (1988). Recent Advances in the study of the Basement Complex of Nigeria. (In) Precambrian Geology of
Nigeria, second edition, pp 11-45.
110
PETROPHYSICAL ANALYSIS OF ‘S.T’ FIELD,OFFSHORENIGER DELTA USING WELL LOGS.
Oluwadare, O.A. and Olowokere, M.T.
Department of Applied Geophysics, Federal University of Technology, Akure
Department of Applied Geology, ObafemiAwolowo University, Ile-Ife.
ABSTRACT
Petrophysical well log was used in the analysis of the reservoir characteristics of ‘S.T’ Field Offshore Niger Delta,
Nigeria. This study was carried out in order to determine the reservoir properties such as lithology, volume of shale,
porosity, permeability, depositional environment, net pay thickness e.t.c.Wireline logs which included deep induction
log (ILD), gamma ray (GR), water saturation (Sw), neutron and density logs were used in the study. The hydrocarbon
in place of the reservoirs was determined based on mean weighted average of porosity, water saturation, gross rock
volume and net to gross ratio. From the analysis, the well logs showed that the area is characterised by sand/ shale
interbeds and the thickness of sand varies for the interpreted beds. The ‘S.T’ wells in offshore Niger Delta
encountered a total of eight hydrocarbon bearing reservoirs (B1000G, C9000G, D1000G, D7000G, E1000G, E3000G
&F1000G) which are oil bearing and D3200G which is gas bearing. The reservoir quality for ‘S.T’especially within
the hydrocarbon zone is of good quality with an average effective porosity ranging from 25% to 36%, gross thickness
ranging from 20.5m to 153m andis characterised by high Net/Gross – 0.84. The petrophysical properties (high
hydrocarbon Saturation, thick reservoir sand which increases with depth) of the reservoirs in ‘S.T’ wells are
favourable for the high hydrocarbon volume.
INTRODUCTION
The ultimate target of any petroleum exploration is to
search for hydrocarbon of economic quantity.
Petrophysical log interpretation is one of the most
useful and important tools in exploration which
provides vital subsurface information on rock
properties and fluid movement. Well logging involves
probing the earth with instrument that gives continuous
reading of physical parameters of formation such as
natural potentials, electrical resistance, temperature,
bulk density, interval transit time, natural radioactivity,
hydrogen content etc lowered into the boreholes. The
formation obtained from these logs can be used to
interpret geophysical condition, determine depth and
thicknesses of reservoirs, distinguish between gas, oil
and water in reservoirs, identify productive zones,
estimate hydrocarbon reserves, determine porosity,
pore geometry and permeability, differentiate lithology
etc. Petrophysical well log was used in the analysis of
the reservoir characteristics of ‘S.T’ Field, Offshore
Niger Delta, Nigeria. This study was carried out in
order to determine the reservoir properties such as
lithology, volume of shale, porosity, permeability, net
pay thickness e.t.c. Wireline logs which included deep
induction log (ILD), gamma ray (GR), water saturation
(Sw), neutron and density logs were used in the study.
The study area ‘S.T’ Field lies within the Niger
Delta which is located in the Southern Nigeria,
between Latitude: 030 08’ – 06oN and Longitude: 040 -
08oE, offshore Eastern Niger Delta (Figure 1)
The Niger-Delta is divided into three formations.
These are the continental top facies (Benin formation),
the paralic delta front facies (Agbada formation) and
the pro delta facies which is the Akata formation
(Short and stauble 1967). They represent prograding
depositional facies that are distinguished mostly on the
basis of sand-shale ratios. ( Doust and Omatola, 1990;
The three sedimentary sequences are tertiary in age .
111
Figure 1: Location Map
showing Niger Delta and
the study area.(Doust &
omatsola,1990)
‘ S.T’ FIELD
METHODOLOGY
A suite of well logs which included deep induction log
(ILD), gamma ray (GR), neutron and density was used
in this study for the petrophysical analysis of ‘S.T’
wells ( ‘S.T’ 1,2 & 3) in Offshore, Niger Delta. This
study was carried out using interactive interpretation
softwares, Kingdom Suite and Petrel Tm for qualitative
and quantitative evaluation.
The Qualitative evaluation involved the use of Gamma
ray log to identify the lithologies and Gamma ray with
deep induction log to correlate reservoirs, Neutron and
Density logs to delineate fluid contacts (gas – oil and
oil – water contacts).
Quantitative evaluation involved the estimation of
parameters using relevant petrophysical equations. The
estimated parameters include Gamma Ray Index (IGR),
Volume of Shale (Vsh), Water Saturation (Sw), Porosity
(Փ) and Permeability (K) e.t.c. The estimated values
obtained both qualitatively and quantitatively were
used for further deductions.
RESULT & DISCUSSION
Petrophysical analysis of ‘S.T’ Field, offshore Niger
Delta was carried out using available electric logs. The
gamma ray logs in ‘S.T ‘ reservoir sand units are
characterized by a low gamma ray reading with
intercalated siltstones and shales. The resistivity log is
generally characterized by higher resistivities opposite
the sandstones than the subjacent shales (Figure 2). On
the neutron/density curve for reservoir D3200G, the
gross S.T’ well sandstone shows increasing density
porosity values and decreasing neutron porosity
values. The hydrocarbon saturation is made up of two
components: Oil saturation (So) and Gas saturation (Sg)
Schlumberger Log Interpretation, 1989. Based on
the qualitative and quantitative interpretation, a total of
eight hydrocarbon bearing reservoirs (B1000G,
C9000G, D1000G, D7000G, E1000G, E3000G
&F1000G) which are oil bearing and D3200G which is
gas bearing were identified. The hydrocarbon types
were identified based on the evidence drawn from the
neutron –density log signatures at their corresponding
depth. A separation of the neutron/density log with the
neutron deflecting to the right and density log to the
left indicated gas while the tracking together of the two
curves indicated oil in the reservoirs. Reservoir quality
of the sand varies widely with porosity ranging from
25 to 36%. Average petrophysical values for each
reservoir are shown in Table 1. Low water saturation
in the reservoirs of the ‘S.T’ wells indicated that the
proportion of void spaces occupied by water is low
thus indicating high hydrocarbon saturation. The
petrophysical properties of the reservoir are enough to
permit hydrocarbon.
Figure 2: Correlation Panel of D7000
Table 1: Petrophysical Parameter for S.T wells
112
CONCLUSION
Detailed petrophysical analysis of ‘S.T’ Field,
Offshore Niger Delta was carried out using wireline
logs to determine some reservoir properties of the
potential reservoirs and the hydrocarbon potential of
the wells. It was discovered that the estimated
reservoir parameters agree with the previous work with
an insight to the hydrocarbon distribution within the
field.
From the study, the delineated reservoirs have high
porosity and permeability that enhance their excellent
quality.
The reservoir quality for ‘S.T’ field especially within
the hydrocarbon zone is good with an average effective
porosity ranging from 25% to 36%, gross thickness
ranging from 20.5m to 153m and is characterised by
high Net/Gross – 0.84 and water saturation – 0.19.
The high hydrocarbon saturation, thick reservoir
sands which increases with depth are responsible
factors for the high hydrocarbon accumulation in ’S.T’
Field.
REFERENCES
Doust and Omatsola; (1990). Divergent /Passive
Margin Basins, American Association of Petroleum
Geologists Memoir 48, p.239-284
Schlumberger, (1989): Log Interpretation Principles
and Application; Schlumberger Wireline and Testing
Houston , Texas 21p
Short and Stauble (1965). Outline of Geology of
Niger Delta:American Association of Petroleum
Geologists Bullettin P 761-768
113
ESTIMATION OF TOTAL ORGANIC CARBON (TOC) FROM DENSITY LOG IN THE NIGER
DELTA EOCENE SHALE
Olisa B. A., B. D. Ako and J.S. Ojo
Department of Applied Geophysics, Federal University of Technology, Akure
(Corresponding author: [email protected])
ABSTRACT
Total organic carbon (TOC) is an important parameter in source rock studies. Laboratory method is the
traditional means of TOC analysis. Samples are collected at discreet sampling points in the borehole. It is
necessary to get a continuous TOC sampling in a shale section for further studies of the subsurface.
Previous work to estimate TOC from well logs had imposed constraints like using combinations of logs
and presence of matrix in the rock composition. Plotting laboratory measured TOC and density (from
well logs) with depth for each well section shows no relationship. The aim of this study is to use density
log alone to derive TOC in the Niger Delta Eocene shale. The objectives are to analyse the sections into
sands/shales, compare laboratory measured TOC to calculated density TOC, derive equations to
calculate TOC from density-TOC relationship and to relate TOC with density in the well bore. Plotting
the laboratory measured TOC (wt%) against density (g/cm3) at the sampling points shows that the
relationship is disordered. This could be due to lithological or mineralogical effects masking expression
of any relationships. Using known hypothesis relating TOC with density, these effects were able to be
removed and the samples were then ordered. Equations were established to calculate TOC from density
logs for three wells regionally spread. The results show that laboratory TOC and calculated density
(TOC) are comparable. In Well 1, at the depth of 8960ft (2731m), the laboratory TOC is 3.6wt% while
calculated density TOC is 3.7wt%. The TOC is inversely proportional to density and TOC can be
calculated from density log
INTRODUCTION
Total organic carbon traditionally is determined in the laboratory by elemental analysis, pyrolysis etc.
This method involves rock samples analysis which is often difficult to obtain from boreholes. Besides,
very costly chemical is required for analysis. As a result, many wells are without TOC data, an important
parameter for source rock studies.
Density log could be an alternative method for TOC estimation because many of the wells have density
logs and calculations could be done without rock samples.
Density log is an induced log measurement and it is a reaction to gamma ray bombardment, Rider (2002).
Passey et al. (1990) gave a model of organic rich rock as containing, the organic matter, the matrix and
fluid(s). He also gave a model curve to explain the crossplot of density and TOC. In a sequence of organic
lean rock (shale) and organic rich rock (black shale), bulk density is less in the organic rich rock, (Meyer
and Nederlof 1984, Meissner 1978, Jia et al. 2012).
The aim of this research is to derive an equation to calculate TOC from bulk density log in the form of
y = mx + c.
y = variable on the y-axis, x is the variable on the x-axis, m is the constant and c is the intercept.
GEOLOGY OF THE NIGER DELTA
The Niger Delta is located on the Gulf of Guinea, between longitudes 50 E to 80 E and latitudes 30 N to 50
N (Figure 1). There are three sequences of rocks in ascending order the Akata Formation, Agbada
Formation and Benin Formation.
114
Figure 1: Map of Nigeria (inset) and Map of the Niger Delta (OML, Oil and Gas Fields) (After
Nton et al., 2012)
Bustin (1988) stated that total organic-carbon (TOC) content of sandstone, siltstone, and shales in his
study is essentially the same (average of 1.4 to 1.6%TOC).
MATERIALS AND METHODOLOGY
Three wells, Well 1, 2 and 3 were selected based on availability of rock-eval TOC (Figure 2). The
respective intervals of interest (Eocene) are 9330-8930 feet (2843-2721m), 6465-7590 feet (2313m-
1970m) and 9790-7450feet (2983-2270m). All wells contain density and gamma ray logs and rock-eval
TOC data. The sands were first separated from shales using gamma ray (GR) with 70 % cut-off values.
The shales have high concentrations of radioactive materials recorded in API and the shales give
deflections to the right. The sands have low concentrations of radioactive materials and give deflections to
left. Total organic carbon (TOC) was analyzed by using three steps. The first step was the cross-plot of
rock-eval TOC against bulk density. The second step was the removal of matrix and fluid(s) effects and
the third step was cross-plot of filtered TOC against bulk density.
Figure 2: Positions of to one another showing density and gamma ray logs, lithology and sampling
intervals
115
Results and Discussion
Figure 3 Rock-eval TOC versus bulk density at Well 1.
Figure 4 Rock-eval TOC versus bulk density at Well 2.
Figure 5 Rock-eval TOC versus bulk density at Well 2.
The cross-plot shows that the correlation coefficients are poor for the cross-plots. This is because of the
matrix effect masking the expression of relationships between TOC and bulk density.
Figure 6 shows the crossplot of filtered TOC against Bulk density. The equation of the line is
y = -0.1692x + 2.6227
y = bulk density (g/cm3) and x is TOC (wt%). R2 is the correlation coefficient (0.8067).
116
Figure 6 Cross-plot of filtered TOC against bulk density.
CONCLUSION
An equation to calculate TOC from bulk density log in conjunction with rock-eval TOC was established
for three wells in the Niger Delta. Though the correlation between the calculated TOC and rock-eval
agrees in many sampling points in each well, the disagreements in some points is due to limited data used
to establish the generalized equation. Results will be improved with the provision of more data.
REFERENCES
Rider M. (2002), The Geological Interpretation of Well Logs, 2nd edition, Rider-French Consulting, p. 1-
279
Passey Q. R., S. Creaney, J. B. Kulla, F. J. Moretti and J. D. Stroud, (1990), A Practical Model for
Organic-Richness from Porosity and Resistivity Logs: Bull. Am. Assoc. Petrol. Geol. v. 74, no.
12, p. 1777-1794.
Meyer B. L., and M. Y. Nederlof, (1984), Identification of Source Rock on Wireline Logs by
Density/Resistivity and Sonic Transit time/Resistivity Crossplots: Bull. Am. Assoc. Petrol. Geol.
v. 68, p. 121-129.
Meissner F. F., (1978), Petroleum Geology of the Bakken Formation Williston Basin, North Dakota and
Montana, the economic geology of Williston basin: Montana geological society, 1978 Williston
Basin symposium, P. 207-227.
Jia J., Z. Liu, Q. Meng, R. Liu, Sun P. And Y. Chen, (2012), Quantitative evaluation of Oil Shale Based
on Well Log and 3D Seismic Technique in the Songliao Basin, Northeast China: Oil Shale, v. 29,
no. 2, p. 128-150.
Nton, M.E., M.N. Tijani, and B.A., Adebmabo,(2012).Petrophysical evaluation and depositional
environments of reservoir sands of X- field, offshore Niger delta, Mineral Wealth Vol. 150 pages
1-12
Bustin, R. M., (1988), Sedimentology and Characteristics of Dispersed Organic Matter in Tertiary Niger
Delta: Origin of Source Rocks in a Deltaic Environment: Bull. Am. Assoc. Petrol. Geol. Bulletin,
v. 72, p. 277-298.
117
Integration of 3D-Seismic and Well Logs In The Sequence Stratigraphic Analysis Of ‘QISS’ Field,
Offshore Niger Delta, Nigeria
Olowolafe, T. S. and Akintorinwa, O. J
Department of Applied Geophysics, Federal University of Technology, Akure
Corresponding Author e-mail: [email protected]
ABSTRACT
The sequence stratigraphic framework of the Agbada formation within “Qiss” field, Southern Offshore
Niger Delta has been established in this study from the integration of well logs and three dimensional
(3D) seismic volume. This was with a view to identifying stratigraphic opportunities that can supplement
depleted structural closures in the area. The study area is extensively deformed by mobile shale substrate
and thus limits the sequence analysis to the upper part of the Agbada Formation. Four sequence
boundaries subdividing the interpreted interval into three sequences were defined based on such
termination patterns as downlaps, toplaps and onlaps exhibited by seismic reflections on the seismic
sections. The inflections between the fining and coarsening upward trends of the log motifs were used to
establish three systems tracts namely the lowstand, trangressive and highstand systems on the well logs
and were tied to the seismic facies on the seismic record using checkshot data. Seismic facies analysis
revealed three major facies namely the chaotic, progradationalfacies and low amplitude parallel seismic
facies. The chaotic facies constitute most of the incision fill basinward as much as they record the
deformation of the strata geometry from the over-pressured shale. While the foreset of the progradational
deltaic deposits could provide reservoir sands that are laterally continuous, the low amplitude parallel
facies record the slow deposition of fine grains from suspension that are potential sealing units within the
basin. A canyon system incised to about 100 meters deep within the second sequence was delineated and
inferred to act as the feeder channel for the deposition of lowstandfaciesbasinward. The fill of such
declivity and the associated levee delineated in this study could constitute excellent reservoirs.
Environments of deposition inferred from log facies analysis include channels, shoreface sands,
transgressive sands and progradational delta within a marginal depositional system. The depositional
architecture of the study area is considered to be majorly influenced by episodes of structural subsidence
caused by sediment loading over the underlying Akata mobile shale. Such collapse enhanced the
deformation of the strata geometry through the depositional history of the field. However, the
stratigraphic predictions of the reservoir and sealing facies within the undeformed interval will enhance
further exploitation strategy in the study area.
Keywords: Sequence stratigraphy, 3D-seismic, Well Logs, Canyon
INTRODUCTION
Extensive hydrocarbon production from “Qiss”
Field offshore Niger Delta province has depleted
reserves associated with growth fault systems
and rollover anticline giving impetus to
exploring the inherent potentials of stratigraphic
plays. Meanwhile, information from the
available three wells provided for this study does
not provide sufficient control to permit
conventional subsurface facies analysis and
mapping. Consequently, it is pertinent to extract
maximum subsurface information from seismic
reflection profiles and the available well logs.
Hence, sequence stratigraphic analysis of this
field is required to meet this need and this has
however necessitated this research.
METHODOLOGY
This study is focused on the interpretation of
depositional processes within the Niger Delta
clastic wedge using well log data from “Qiss”
Field and seismic data spanning the field. The
study area is extensively deformed by mobile
shale substrate and thus limits the sequence
analysis to the upper part of the Agbada
Formation. The concepts and techniques
modified after Vail and Wornardt (1991) form
the basis for this study. The structural and
stratigraphic frameworks of the study area were
interpreted using the workflow in Figure 1 with
the aid of Petrel TM (2009) workstation. Stratal
discontinuities and regionally parallel reflections
in the seismic cube were related to vertical
118
patterns in well logs for sequence stratigraphic
analysis. Subsequently, seismicfacies analysis
and interpretation of depositional environment
and lithofacies from the objectively determined
seismic facies parameter were carried out. Well
log-seismic sequence stratigraphic cross-section
was prepared and possible prospects within the
study area were evaluated.
Figure 1:The Interpretive Workflow for the
Study
RESULTS AND DISCUSSION
Four sequence boundaries subdividing the
interpreted interval into three sequences were
defined based on such termination patterns as
downlaps, toplaps and onlaps exhibited by
seismic reflections on the seismic sections.
Three systems tracts namely the lowstand,
trangressive and highstand systems were
established on the well logs based on the
inflections between the fining and coarsening
upward trends of the log motifs and were tied to
the seismic facies on the seismic record using
checkshot data. Seismic facies analysis revealed
threemajor facies namely the chaotic,
progradationalfacies and low amplitudeparallel
seismic facies. The chaotic facies constitute
most of the incision fill basinward as much as
they record the deformation of the strata
geometry from the over-pressured shale. While
the foreset of the progradational deltaic deposits
could provide reservoir sands that are laterally
continuous, the low amplitude parallel facies
record the slow deposition of fine grains from
suspension that are potential sealing units within
the basin. A canyon system incised to about 100
meters deep within the second sequence was
delineated and inferred to act as the feeder
channel for the deposition of
lowstandfaciesbasinward. The fill of such
declivity and the associated levee delineated in
this study could constitute excellent reservoirs.
Environments of deposition inferred from log
facies analysis include channels, shoreface
sands, transgressive sands and progradational
delta within a marginal depositional system.
The growth fault structures and the associated
four way dip closures constitute the major
structural leads within the study area while the
basal incision fills of the lowstand systems
tractthat are capped by overlying by trangressive
sealing facies(Figure 2) are expected to serve as
major stratigraphic prospects.
119
Figure 2: Cross-sectional Interpretation of Stratigraphy within Qiss Field
CONCLUSION
The depositional architecture of the study area
(Figure 2) is considered to be majorly influenced
by episodes of structural subsidence caused by
sediment loading over the underlying Akata
mobile shale. Such collapse enhanced the
deformation of the strata geometry through the
depositional history of the field. However, the
stratigraphic predictions of the reservoir and
sealing facies within the undeformed interval
will enhance further exploitation strategy in the
study area
REFERENCE
Vail, P. R. and Wornardt, W. (1991). An
Integrated Approach to Exploration and
Development in the 90s. Well log Seismic
Sequence Stratigraphy Analysis. Gulf Coast
Association of Geologists XL1, 630-650.
120
THE IMPORTANCE OF ROLL-ALONG MEASUREMENT IN ELECTRICAL RESISTIVITY
TOMOGRAPHY (ERT)
Osumeje J.O. & Lawal K.M.
Department of Physics, A.B.U., Zaria
[email protected] or [email protected]
INTRODUCTION
The conventional four (4) number of electrode
system used in geophysical investigation has
been in existence for decades ago. They have
been used for surface and subsurface
investigations that have yield good results. With
improvements in technology and the need to
reduce the difficulties involved in carrying out
field measurements, the need to use more than
four electrodes (multiple electrodes) at a time
came into existence. Although out of the
multiple electrodes connected at ones only the
required four electrodes (two current and two
potential electrodes) are selected at any
instantaneous time for a particular measurement.
Recently, many Nigerian universities have
purchased this latest set of equipments
consisting of the resistivity meter and the
multiple electrode selector. In this work, we
intend to show the need to always use the roll-
along technique in electrical resistivity field
measurements. For any electrical resistivity
measurements, current must be ejected into the
earth and equi-potential surfaces are created on
which the potential is measured. When the
profile line to prospect is longer than the length
of the multi-core cable, a roll along procedure is
usually used (Bernard, 2003). If for a given
electrode spacing, several midpoints are probed
laterally and for wider electrode spacing several
other midpoints are probed laterally, we shall
end up with a midpoint of measurement
increases in depth and also shifting gradually to
form a V-shaped pattern shown in figure 1,
(Bernard, Leite, & Vermeersch, 2003).
Stations 3 with
electrodes
Stations 2 with
electrodes
Stations 1 with
electrodes
Terrameter
Electrode
Blind Spot Blind Spot
(a)
Figure 1: Gradual shift in spread (a) 3 spread end-to-end pattern with multiple electrodes
(b) 5 spread roll-along pattern with multiple electrodes
Stations 5 with electrodes
Stations 4 with electrodes
Stations 3 with electrodes
Stations 2 with electrodes
Stations 1 with electrodes
Terrameter
Electrode
Continuous
depth of probe
(b)
121
METHODOLOGY
The measurements were carried out in a
basement terrain were the depth to basement has
been established to be between 25 m to 35 m.
Details of the Geology of the area could be
obtained from this literatures (Osazuwa &
Osumeje, 2007, 2008; Osumeje, Oniku, &
Lawal, 2011). The Terrameter (Abem SAS
1000) is placed at the centre of the spread and
the electrodes are distributed to the left and right
of the Terrameter. The electrodes are connected
as required and all the necessary settings are
done. Before measurements commences, each
electrode will be tested for good contact with the
earth. The duration of the measurement depends
on the protocol (array) type and on the length of
the cycle (i.e duriation of taking a reading).
After the last reading is taken for any spread, the
Terrameter displays a “UP”, “DOWN”, “END”
options. Since there is the need for a continue
prospect and we are moving upward along the
profile line, we selected the “UP” option.
Without switching off the equipment, we
detached the necessary cables and move to the
next station. With the same setting, the same
array, the measurement continued after the
electrode contacts are confirmed again. Theis
process is repeated for as long as required. At
the end of the profile line where the roll-along
stops, we choose the “END” option after the
measurement was completed. The whole
measured data was saved in a single file. We
downloaded the data from the file, converted it
to the necessary format that is accepted by the
processing software (RES2DINVx3) after
reduction of the data we generated of the 2D
resistivity image in pseudosections (Loke, 1999,
2012, Sorensen 1996).
RESULTS AND DISCUSSION
In the investigation, three parallel profile lines
were carried out. The data was processed and the
results are shown in figure 5, figure 6 and figure
7. The estimated error for each pseudo section
was below 16%. In each figure there is the roll-
along profile (figure 2a) and the end-to-end
profile (figure 2a and 2b). By comparism, if we
match the two single profiles on the roll-along
profile, it is obvious that the section “C” which
is located at the centre of the roll-along spread
will not be accounted for. The second section
(with white dash lines boundary) carries a lot of
information about the anomaly present in this
study area and this is the missing part for the
end-to-end single profile. A close look at the
figure show that the shape and resistivity value
of the anomalies labelled “A”, “B”, “D” and “E”
in the roll-along pseudosection (figure 2a) are
identical with those on the end-to-end
pseudosections (figure 2b). But the anomaly
located at section “C” is completely missing
from end-to-end pseudosection. The missing
section (“C”) carries very vital information of
the nature of the anomalies in the subsurface.
The same can be identified for the other profile
(figures 3a and 3b).
CONCLUSION
In all the results, the roll-along measurement has
shown details of the anomalies present in the
subsurface together with missing anomalies
from the blind spots recorded in the end-to-end
A comparism between anomalies present in the
two types of measurement has shown very
strong correlation based on anomaly shape and
resistivity values.
This implies that with the roll-along type of
measurement, accurate results with detail
information of subsurface anomalies can be
obtained. The roll-along type of measurement in
Electrical Resistivity Tomography profiling can
therefore give a much better image into the earth
subsurface and hence recommended for practice.
122
B A
C D
E
B A
D
E
Figure 2b: End-to-end profile
Figure 2a: Roll-along profile
A
B
D E
F
C
Figure 3a: Roll-along profile
123
B
A
D E
F
Figure 3b: End-to-end profile
124
REFERENCE
Bernard, J., Leite, O., & Vermeersch, F.,
(2003). Multi-electrode resistivity
imaging for environmental and mining
Applications, IRIS Instruments,
Orleans, France.
Loke, M. H., (1999), Electrical imaging
surveys for environmental and
engineering studies, a practical guide
to 2D and 3D surveys,
geoelectrical.com.
Loke, M.H., (2012). Tutorial : 2-D and 3-D
electrical imaging surveys. Geotomo
Software, Malaysia.
Bernard, J., (2003), short note on the depth of
investigation of electrical methods,
www.heritagegeophysics.com,
Lawal K.M., Oniku S.A. and Osumeje J.O.,
(2011). A Fractal Geological Map of
Zaria Area, North Central Nigeria.
BAGALE Journal of pure and applied
sciences, 8(1):36 - 52.
Osazuwa I.B. & Osumeje J.O., (2008). The
delineation of clay substratum using
seismic refraction technique,. Bayero
Journal of Physics and mathematical
Science, 1(2): 201-209.
Osazuwa I.B. & Osumeje J.O., (2007).
Application of geophysics tomography
for the foundation study of collapsed
building at Ahmadu Bello University,
Zaria. 43rd Annual International
Conference of Nigerian Minning and
Geosciences Society (NMGS), held at
Akure, pp 71.
Osumeje J.O., Oniku S.A. & Lawal
K.M.,(2011). The use of seismic
tomography to determine the stability
of overburden load. International
Journal of Scientific Research, 1(3):
187-192.
Sorensen K. I. (1996): Pulled Array
Continuous Electrical Profiling. First
Break 14: 85–90.
Telford, W.M. Geldart, L.P. & Sheriff, R.E.,
(2004) Applied Geophysics, second
edition. Cambridge University Press,
New York Port Chester Melbourne
Sydney.
125
GEOTECHNICAL CHARACTERIZATION OF SUBGRADE SOILS ALONG HIGHWAY
PAVEMENTS IN PARTS OF ONDO STATE, NIGERIA
Joshua O. Owoseni and Siyan Malomo
Department of Applied Geology, Federal University of Technology, Akure, Nigeria
E-mail: [email protected]; [email protected]
ABSTRACT
This paper evaluates the index and engineering properties of some subgrade soils in parts of Ondo
State, Nigeria. This is with a view to establishing likely geotechnical basis for the instability of
portions of some flexible pavements in the area. Investigative tests include, grain size distribution,
specific gravity of grains, consistency limits, compaction, Californian Bearing Ratio (CBR), and
unconfined and triaxial compressions. The British Standards (BS) 1377 was used with necessary
modifications. The Casagrande charts classification indicated that the subgrade soils below stable
pavements have low plasticity while soils below unstable sections possess medium to high plasticity.
The Optimum moisture contents and Maximum dry densities range from 12.2% to 16.8% and 1775
Kg/m2 to 1964 Kg/m2 for soils at stable locations, and from 13.2% to 25.1% and 1438 Kg/m2 to 1923
Kg/m2 for soils at unstable locations respectively. The Unconfined compressive and triaxial Shear
strength for soils underlying stable locations range from 50.21 KPa to 209.62 KPa and 42.20 KPa to
170.10 KPa respectively while those soils under unstable locations range from 25.19 KPa to 62.85
KPa and 19.00 KPa to 88.90 KPa respectively. Moreover, soils below stable pavements exhibited
relatively higher CBR values than their counterparts below unstable sections. Obviously, soils from
stable locations showed better compaction characteristics and higher strengths than their
counterparts from unstable locations. Therefore, the stability (or failure) of the flexible highway
pavements in the study area is largely a function of the geotechnical properties of the subgrade soils.
Keywords: Road failure, flexible pavement, subgrade soils, geotechnical properties
INTRODUCTION
Most often than not, the socioeconomic
development of a nation is directly or
indirectly a function of good transportation
network. It is sad to note that many roads in
Nigeria are in deplorable states thereby
limiting national development. Several factors
can lead to the degradation and eventual
failure of highway pavements. Such factors
may include: (1) seasonal moisture and
volume changes in expansive soils resulting in
soil volumetric changes; (2) poor engineering
properties of subgrade soils which fall short of
highway subgrade standard specifications; (3)
poor drainage conditions; (4) construction
defects and excessive traffic/vehicular load
(Adewoye and Adeyemi, 2004; Van Der
Merwe, 1980). Road failure can take different
forms, such as, waviness, soil movement by
creep, slides, settlement and compressibility.
In such situations, soil stabilization becomes
inevitable in order to improve on the
engineering geological properties of the soils
for better engineering performance.
This study evaluates the geotechnical
properties of soils at stable sections
(longitudes N07o 12.822', N07o 26.470', N07o
32.014', N07o 15.091' and latitudes E005o
33.323', E005o 45.850', E005o 46.271', E005o
126
11.175' respectively) and unstable sections
(longitudes N07o 12.867', N07o 26.290', N07o
32.016', N07o 15.090' and latitudes E005o
33.303', E005o 45.850', E005o 46.218', E005o
11.137' respectively) along three major roads
in Ondo State. This is with a view to
determining the geotechnical basis, if any, for
the failure or stability of sections of the
flexible pavements.
RESEARCH METHODOLOGY
The research involved field study and
laboratory investigations. Field investigation
entails geologic mapping, soil sampling,
description and preparation soil samples.
Surface geologic mapping was carried out to
ascertain the parent rocks on which the
residual lateritic soils are developed. Bulk soil
samples were collected from trial pits at
reasonable depths (about 1.5m) below the
stable and failed sections of the flexible
pavements, and described by visual inspection.
The soil samples were air-dried at room
temperature prior to laboratory analyses.
Investigative laboratory tests conducted
include specific gravity of soil grains, particle
size distribution, consistency limits,
compaction, Californian bearing ratio, and
unconfined and triaxial compressions. The
analyses followed the procedures outlined in
the British Standards (BS) 1377 with minor
modifications as appropriate.
RESULTS AND DISCUSSION
Table 1 shows the results of some
investigative index and engineering tests
conducted on the subgrade soils from both
stable and failed sections along the road
pavements.
Specific gravity
The specific gravity of soil grains at stable
locations range between 2.70 and 2.75
whereas the values are between 2.64 and 2.70
for soils at unstable locations. This clearly
indicates higher degree of soil maturity and
laterization, and hence stronger soils at the
stable locations than the failed sections.
Particle size distribution
The grain-size distribution characteristics
show that the soils are generally well-graded.
However, the unstable locations exhibit higher
percentage fines than the stable sections
(Table 2). The implication of this is that the
observed poor engineering behaviour of such
portions of the pavements is partly a reflection
of the relatively higher amounts of fines
because the amount of fines is inversely
proportional to the engineering performance of
most lateritic soils (Adewoye and Adeyemi,
2004; Owoseni et. al., 2012).
Consistency limits
The Casagrande charts classification (Figure
1) indicated that the subgrade soils are all
inorganic, plotting above the A-line. However,
soils below stable pavements have low
plasticity while their counterparts beneath
unstable sections possess medium to high
plasticity. The shrinkage limit values for soils
at stable locations range between 6.4% and
9.3%. However, the values are relatively
higher at unstable locations, ranging between
10.7% and 15.0%. This may have contributed
largely to the failure of the pavements.
Compaction characteristics
The maximum dry density (MDD) values for
soils below stable sections range between
1775 Kg/m2 and 1964 Kg/m2 while the values
vary from 1438 Kg/m2 to 1923 Kg/m2 for soils
127
beneath unstable sections. Similar behavioural
trend was observed with the moisture content
of the soils, in which case the soils below
stable sections exhibit lower moisture contents
than their counterparts beneath unstable
sections of the roads (Figure 2). It is obvious
from these that the subgrade soils underlying
the stable sections possess better compaction
characteristics than those associated with
unstable portions of the flexible pavements.
California bearing ratio
The bearing capacity of subgrade and sub-base
soils is often estimated using the CBR test
results. Both the un-soaked and soaked CBR
of samples from unstable sections are lower
than the CBR of corresponding samples from
stable sections (Table 1). This is an indication
that the subgrade soils from beneath stable
sections possess better load bearing and
strength characteristics than those beneath
unstable sections of the pavements.
Table 1. Some Index and Engineering Properties of soils investigated.
Properties
Location 01 Location 02 Location 03 Location 04
S01 U01 S02 U02 S03 U03 S04 U04
Natural moisture content (%) 6.30 14.30 8.20 15.30 11.20 15.10 20.00 22.10
Specific gravity, Gs
Shrinkage limits, SL (%)
2.75
9.30
2.66
10.70
2.70
6.40
2.64
15.00
2.75
7.10
2.71
12.10
2.75
8.60
2.70
12.90
Liquid limits, LL (%)
Plastic limits, PL (%)
34.60
17.10
37.20
17.90
27.60
16.70
53.00
25.00
19.70
N.P.
37.80
17.40
34.80
18.50
56.00
27.70
Plasticity Index, PI (%) 17.53 19.28 10.92 28.00 0.00 20.44 16.33 28.26
Optimum moisture content, OMC (%) 12.30 13.20 12.20 13.70 16.80 18.90 15.70 25.10
Maximum dry density, MDD (kg/m3) 1956 1923 1964 1902 1775 1688 1820 1438
CBR unsoaked (%)
CBR soaked (%)
UCS (KPa)
Triaxial shear strength, г (KPa)
59.00
15.00
209.6
42.20
6.00
3.00
49.87
19.00
26.00
15.00
50.21
97.30
23.00
9.00
23.98
52.70
16.00
11.00
50.22
110.7
59.00
10.00
25.19
59.90
25.00
13.00
97.44
170.1
3.00
2.00
62.85
88.90
Table 2. Grading characteristics of soils investigated.
128
S01 U01 S02 U02 S03 U03 S04 U04
% Fines (Clay + Silt) 21.50 35.50 15.10 17.00 9.90 29.50 49.20 64.20
% Sand 50.30 41.70 50.10 43.80 47.40 51.40 34.90 31.20
% Gravel 28.20 22.80 34.80 39.20 42.70 19.10 15.90 4.60
Figure 1: Casagrande chart classification of
the studied subgrade soils
Figure 2: Compaction curves for the studied
subgrade soils
Compressive and Shear Strength
Both the compressive and shear strength
values for soils in stable areas are relatively
higher than those for unstable locations (Table
1). The better grading characteristics of soils
beneath stable sections of the pavements is
reflected here.
CONCLUSION
The subgrade soils are generally well-graded.
Those ones underlying stable sections of road
pavement possess low plasticity while those
beneath unstable portions of the roads exhibit
medium to high plasticity. Moreover, the
subgrade soils below stable pavements
exhibited relatively higher CBR, UCS and
shear strength values than their counterparts
below unstable sections. Furthermore, soils
from stable locations showed better
compaction characteristics than their
counterparts from unstable locations.
Therefore, the stability (or failure) of the
flexible highway pavements in the study area
is largely a function of the geotechnical
properties of the subgrade soils.
REFERENCES
Adewoye A. O. and Adeyemi G. O. (2004).
Geotechnical properties of soils along the
Lagos-Ibadan expressway, Nigeria. USEP:
129
Journal of Research in Civil Engineering. vol.
1 (1), pp. 1 - 10.
British Standards Institution (1990).
Methods of Testing Soils for Civil
Engineering Purposes British Standards 1377.
Owoseni J. O., Adeyemi G. O., Asiwaju-
Bello Y. A., and Anifowose A. Y. B. (2012).
Engineering geological assessment of some
lateritic soils in Ibadan, south-western Nigeria
using bivariate and regression analyses.
African Journal of Science and Technology,
Science & Engineering series, vol. 12 (1), pp.
59-71.
Van Der Merwe, C. P. (1980). The
Deterioration of Road Pavements Due to
Volumetric Changes in the Road Bed. 7th Reg.
Conf. Africa. Soil Mechs. Found. Eng. Accar
130
EXPERIMENTAL STUDY OF SCHLUMBERGER VERTICAL ELECTRICAL SOUNDING
DATA ANALYSIS AND INTERPRETATIONS IN MICROSOFT WINDOWS
ENVIRONMENT
Wahab S. A., Akinyokun O. C., Ojo J. S. and Enikanselu P. A.
Applied Geophysics Department, Federal University of Technology, Akure
ABSTRACT
In this paper we developed a methodology on which application software for the interpretation of
Schlumberger vertical electrical sounding data was built. The iterative method used involves pre
process data quality check, forward modeling and adjustment of layer parameters until acceptable
minimum Rms error is obtained. The developed application software coded in Microsoft Visual Basic
language is user friendly, menu driven and runs on Microsoft Windows operating system. The graphic
user interface provides menu for printing of final output. Field data acquired from Osun State has
been used as an experimental study to demonstrate the efficacy of the application software.
NTRODUCTION There exist three well known methods for Schlumberger Vertical Electrical Sounding (VES) data
processing and interpretation over a horizontal stratified media (Zohdy, A.A.R.,1989.). The first
method involves partial curve matching, using standard curves to arrive at an approximate model of
the subsurface. The disadvantage of this method is that the percentage error could be as large as
twenty five percent (25%). The second method is the computer iterative method, in which layer
parameter obtained from partial curve matching is used as the initial input from which resistivity
transform is calculated and apparent resistivity is calculated by process of convolution with Ghosh
filters (Ojo, J. S., 1993 and Vander Velpen, B.P.A., 1988). The third method involves direct
interpretation of VES data without any initial input of layer parameter, layer parameter used is derived
automatically from the field data. The drawback of this method is spurious number of layers is often
generated and final output is not as accurate as the second method (Zohdy, A.A.R., 1989.)
There is a dearth of specialized geophysical application software in the market today. A popular
geophysical electrical resistivity application software described as Resist has been described in
Vander Velpen, B.P.A., (1988.). It supports Wenner, Schlumberger and Dipole-dipole arrays. The
software has no provision for the following:
a. Pre-process data quality check and control.
b. Printing of final output.
c. Windows enabled graphic user interface.
d. User-friendly, menu driven and intelligence.
In the field of geophysics, the interpretation of data is as good as the data. Special attention must be
given to the issue of data quality assurance. The cost and risk involved in drilling boreholes either for
oil or water prospecting is so high that no one would want to drill a dry well. In order to avoid this,
interpretation must be accurate and timely.
An attempt is made in the research reported in this paper to adopt the iterative procedure for VES data
analysis and interpretation presented in Ojo, J. S., (1993.). Application software for VES data analysis
and interpretation which runs on Microsoft Windows operating system platform is developed using
Microsoft Visual basic language. A case study of VES data collected in some locations in Osun State
of Nigeria is carried out and the results obtained were presented.
The specific objective is to provide a tool that will remedy the flaws of the existing and popular
geophysical application software which were highlighted above.
131
METHODOLOGY
The Windows based Schlumberger vertical electrical sounding data analysis and interpretation
application software is an extension of the work in (Zohdy,A.A.R., 1989, Vander Velpen, B.P.A.,
1988 and Ojo, J. S., 1993).
The following modules serve as frame work for the application software developed.
a. Acquisition of field data.
b. Field data quality check
c. Storage of field data
d. Computation of resistivity transform curve
e. Computation of apparent resistivity curve by convolution
f. Computation of Root Mean Square (RMS) Error
g. Iteration
h. Multimedia presentation of output graph
1.1 Field Data Quality Check and Control
Filtering poor quality data otherwise known as noise from the field enhances data quality. Field data
in Schlumberger array for VES is naturally divided into segments as dictated by electrode separation.
There are points of repetitions in successive segments, and since the apparent resistivity obtained at
the end of a segment should be equal in most cases to that obtained at the beginning of the next
segment, as seen at electrode separation 6.0m, 15.0m, 40.0m and 100.0m. A mechanism is built in the
design for an alarm to be raised if these points are not the same.
Noisy data is filtered out by suppressing those data that are not consistent with any known geology of
the area and are incongruous with the average data of a particular segment of the model curve. A
dialogue session is invoked so that user can make correction if necessary. In this way, data quality is
ensured. User edits any variance highlighted by the system before further processing. The decision to
accept final correction is solely that of the human expert user who relies on his past experience to
decide.
2.2 Evaluation of Apparent Resistivity Model Curves
The evaluation of the apparent resistivity model curve is a two phase process. The first phase is
concerned with the computation of the sample values of the resistivity transform from the layer
parameters as proposed in Pekeris, (1940). This is accomplished by the application of a recurrence
relation defined by:
Ti = [T i+1 + ρi tanh(λti)] / [ 1 + T i+1 tanh(λti)/ ρi] (1)
The second phase is concerned with the determination of the sample values of the apparent resistivity
from those of the resistivity transform by convolution of sampled transform with inverse filter
coefficients proposed in Ghosh, D.P., (1971.). This is accomplished by the application of the equation
defined by:
ρapp (x0) = Σ fjT(y0 - j∆y) (2)
The filters for the conversion of the resistivity transform into apparent resistivity in a Schlumberger
configuration have been published in Ghosh, D.P., (1971.). The filter coefficients for Schlumberger
adopted in this research are; 0.0024, -0.0103, 0.0144, -0.0211, 0.033, -0.0574, 0.1184, -0.3162,
1.0219, -2.4514, 1.8192, 0.6486, 0.1739, 0.0079, 0.0200, -0.0106, 0.0093 and -0.0038. (Koefoed, O.,
1979).
2.3 Iterative Procedure
132
The iterative process is as follows:
a. Comparison is made between field and calculated apparent resistivity data, percentage Rms error
is calculated using the equation defined by:
RRmmss %% == √√∑∑ NN
jj==11
[[((PPoojj –– PPccjj))//PPoojj))22//NN]] XX 110000 ((33))
It is normal to expect a high Rms error at the beginning of iteration, as no adjustment of layer
parameters has taken place.
b. If the Rms percentage is unacceptable, adjustment in layer thickness is carried out by
multiplication of thickness of layer by a factor of 0.9, a layer at a time.
c. A new set of calculated apparent resistivity data is obtained.
d. Step (a) is repeated to see whether there is increase or decrease in Rms. If the Rms is
increased, the previous thickness for the layer under consideration is accepted as the true layer
thickness. If Rms decreases, the previous thickness is again reduced by a factor of 0.9 until
convergence.
e. Resistivity ρi is adjusted iteratively until minimum Rms is obtained with the equation;
ρ i+1 (j) = ρi(j) x ρo (j)/ ρci (j) (4)
Iteration process is terminated when one of the following conditions is met:
(i) A prescribed minimum Rms percentage (less than 2% for field data) is obtained.
(ii) A little or no further improvement in fit is detected.
(iii) A maximum number say 30 iterations are done.
(iv) The Rms percent increases instead of decreasing.
The initial results obtained are displayed on the screen for the visual observation of the earth scientist.
The layer parameter file is opened and updated with newly calculated layer parameters which are used
to generate new calculated apparent resistivity. Two new curves are generated and a new Rms
calculated. Further iterations are carried out until Rms value changes no more.
RESULT AND DISCUSSION
Field data collected in Ejigbo, Osun State is used in this report as shown in Table 3.1
Table 3.1 Field data obtained at VES 4.
S/N Electrode separation (m) Apparent resistivity (Ωm)
01 01 1426.00
02 02 955.00
03 03 616.00
04 04 653.00
05 06 645.00
06 06 615.00
07 08 631.00
08 12 715.00
09 15 898.00
10 15 778.00
11 25 874.00
12 32 1029.00
13 40 1056.00
14 40 804.00
15 65 849.00
16 100 914.00
17 100 1202.00
133
The initial graph and corresponding layer parameters are presented in figure 3.1. The curves obtained
after a number of iterations are presented in figure 3.2. The initial Rms of 22.37% is not acceptable.
Further iterations were carried out until the Rms converged at 14.80%.
Figure 3.1 Graphical User Interface showing field curve and model curve with layer parameters at top
right corner with Rms of 22.37%.
Figure 3.2 Graphical User Interface after iterations with the final Rms of 14.80%.
There are five layers with the following parameters;
Table 4.1 Optimum parameter of the subsurface
Layer
Number
Thickness Resistivity
1 0.675m 1695.75Ωm
2 6.075m 559.597Ωm
3 25.65m 1394.50Ωm
4 27.3599m 523.687Ωm
5 ∞ 3491.25Ωm
134
In comparison Resist software, converged with a smaller Rms % error for same case study but this as
a result of its more tolerance for noise.
CONCLUSIONS
Geophysical interpretation of sounding data collected from the field in recent times is done with the
aid of computers. The available software applications used are most of the time not written
purposefully for the use of the geophysical data interpretation and those so written are always too
expensive and very scarce. In this work, some models have been studied and areas of improvement
identified. An improved model which is a collection of the strong features of some of the existing and
popular models has been developed and its experimental study carried out. The improved model
provides adequate mechanism for data quality check and control, iterative analysis, data analysis in
Microsoft Windows environment using Microsoft Visual Basic Language and multimedia
presentation. The developed application software is user friendly, menu driven, intelligent and
interactive. The geophysical field data from Osun State have been used to test run the software and
the results obtained presented.
REFERENCES
Bayode, S. (2000.). Geophysical Characterization of the Iwo Migmatite Gneiss/Granite Complex: its
significance to ground water Potential. (M. Tech. Thesis).
Ghosh, D.P., (1971.) The Application of Linear Filter Theory to the Direct Interpretation of
Geoelectrical Resistivity Sounding Measurement. Geophysical Prospecting, vol. XIX, No. 2, pp.
192 – 217.
Ojo, J. S., (1993.) A generalized computer program for Schlumberger Depth Sounding Data
Interpretations. Jour. Of Min. Geol., vol. 29, No. 2, pp. 37 – 45.
Pekeris,. (1940.) A Recurrence Relation. Geosounding Principles, 1. Resistivity Sounding
Measurement. (Elsevier Scientific Publishing Company).
Vander Velpen, B.P.A., (1988.) Resist (M.Sc. Research Project).
Zohdy, A.A.R., (1989.) A new method for the automatic Interpretation of Schlumberger and Wenner
sounding curves. Geophysics vol. 54, No. 2 (February 1989); pp. 245 – 253.
135
ESTIMATION OF PORE PRESSURE FROM WELL LOGS: A CASE STUDY OF
‘’MALCOLM FIELD’’, OFFSHORE NIGER DELTA, NIGERIA
Abiola Olubola and 2Adeduyite Ebenezer Temidayo
Department of Applied Geophysics, Federal University of Technology, Akure, Nigeria
Department of Earth Sciences, Adekunle Ajasin University, Akungba Akoko, Nigeria
Corresponding Author email: [email protected]
ABSRACT Pore pressure evaluation and prediction was undertaken in Malcolm field, offshore Niger Delta, Nigeria
using wireline log data. The pore pressure gradient indicator used is the sonic log from three wells
namely; A, B and C which were drilled in the field. Ben Eaton’s method was used to estimate pore
pressure gradient in this research work. Overpressured intervals were also delineated on the sonic log
data with the use of a Normal Compaction Trendline (NCT). In well A, normal pressure at depths 6605 ft
and 9265 ft with its pore pressure delineated to be 0.449 psi/ft. Abnormal formation pressure at depths
6682 ft, 8914 ft, 9547 ft was delineated to be 0.2686 psi/ft, 0.1250 psi/ft, and 0.1700 psi/ft respectively. In
well B, at depths 7573 ft and 9014 ft abnormally low pressure of 0.2942 psi/ft and 0.1159 psi/ft
respectively were delineated, while at depth 11106ft, abnormally high pressure was delineated to be
0.6755 psi/ft. In well C, at depths 7447 ft and 8299 ft abnormally high pressure was delineated to be
0.6264 psi/ft and 0.6982 psi/ft respectively, while at depths 9676 ft and 10005 ft, abnormally low pressure
were delineated to be 0.1409 psi/ft and 0.2442 psi/ft respectively. There was no normal pressure in well B
and C. As a result of these, accurate pore pressure prediction in overpressured regions is essential to
ensure safe drilling operations and reduce the cost of drilling.
Keywords: Pore pressure, Normal compaction trendline, Abnormal formation pressure, High pressure,
Overpressured
INTRODUCTION
With the drilling of most deep wells, formations
are penetrated that will flow naturally at a
significant rate. In drilling these wells, safety
dictates that the wellbore pressure (at any depth)
be maintained between the naturally occurring
pressure of the formation fluids and the
maximum wellbore pressure that the formation
can withstand without fracture. Knowledge of
formation fluid pressure and fracture pressure,
and how these two parameters vary with depth is
extremely important in planning and drilling a
deep well (Eyinla and Oladunjoye, 2014).
The prime target of petroleum exploration is the
measurement of various geophysical properties
of the subsurface rock formations of particular
interest are porosity, permeability and fluid
content. Petrophysical interpretation of logs
plays an important role in the discovery and
development of petroleum and natural gas
reserves (Eyinla, 2011). It also helps to correlate
zones, identify productive zones, and determine
depth and thickness of zones to distinguish
between oil and gas or water in a reservoir and
to estimate hydrocarbon reserves.
The different formation pressure encountered in
an area play a vital role both during exploration
and exploitation of hydrocarbon resources
reservoir. The different kinds of reservoir
pressure which are usually encountered during
the course of drilling are broadly divided into
three main components: Hydrostatic pressure,
Overburden pressure and Formation pressure.
METHODOLOGY
Methods of evaluating abnormal pore pressures
are separated in two categories, prediction
methods and detection methods. The prediction
methods normally use data obtained from
seismic surveys, offset well logs and well
history. Detection methods traditionally utilize
drilling parameters and well log information
obtained during the actual drilling of a well
(Yoshida, 1996). The methods of pore pressure
estimation include: Dc-exponent, Zamora‘s
method, Bourgoyne-Young drilling model, and
Eaton‘s method.
136
The Eaton‘s method was used in this research
work to estimate the pore pressure gradient from
well logs. Three pore pressure prediction
strategies was reviewed and applied to the
available data. The three pore pressure
prediction strategies require petrophysical data,
specifically formation resistivity or conductivity,
to predict pore pressures. Eaton‘s equation is as
follows:
PP = OBG – ((OBG – Pn) * (ΔTn/ΔTo)^3.0)
………………… (i)
Where: PP = Predicted pore pressure (psi/ft) at
depth Z,
OBG = Overburden Gradient (psi/ft) at depth Z,
Pn = the normal pressure at depth Z,
ΔTn = the assumed normal sonic slowness
(μsec/ft) at depth Z (calculated from the NCT),
ΔTo = the observed (measured) sonic slowness
(μsec/ft) at depth Z.
Equation exponent for Sonic is 3.0. Regardless
of which log data to be used for the pressure
estimation, they all rely on creating a trend line
based on data from a formation with a normal
pressure regime, in the addition to knowledge of
the overburden pressure gradient and normal
pore pressure gradients of the area.
RESULTS AND DISCUSSION
The results of this study were presented in form
of curve and depth picking.
Curve picking A set of curve was picked through smoothed
sonic log data from three wells in order to
establish Normal Compaction Trend (NCT)
from sonic log. These curves were plotted with
respect to depth and the normal compaction
trend established (Figures 1, 2 and 3). The
deviation from this trend is an indication of
abnormal pressure (Dutta, 2002; Huffman,
2002). Quantitative pressure analysis using the
sonic log is based on calibrating the observed
sonic log value and an expected or normal sonic
value with known pressure measurements.
Fig. 1: Fitting Normal Compaction Trend to the
sonic data of Well A
Fig. 2: Fitting Normal Compaction Trend to the
sonic data of Well B
Fig. 3: Fitting Normal Compaction Trend to the
sonic data of Well C
137
Depth Picking The depth of the normal compaction trend
(NCT) was picked in the three well from
smoothed sonic data and the depth was
corresponded to the each other in the three wells.
This method is based on the principle of flow
direction of the pore pressure gradient.
Using the methodology described above from
the well-studied, the pore pressures of the well
vary from depth to depth ranging from 6505ft to
11764ft. Normal pore pressure occurred only at
depth 6605ft (at 0.449PSI/FT) and depth 9265ft
(also at 0.449PSI/FT) in Well A but abnormal
formation pressure occurred at the depths of
7113ft (0.6059psi/ft) which is abnormally high
pressure. Abnormal formation pressure also
occurred at depth 6682ft, 8914ft, 9547ft with
values 0.2686psi/ft, 0.1250psi/ft, and
0.1700psi/ft respectively. All the remaining
depths are moderately pressured. Pore pressure
above 0.449psi/ft is said to be abnormally high
pressure (supressure) while pressures below
0.449psi/ft is said to be abnormally low pressure
(subpressure).
From table 4.2 below, the evidence of pore
pressure in the well, with various depth of
interval (6235ft -11106ft) in Well B in the
formation. The case of abnormally low pressure
occurred at depths 7573ft and 9014ft with values
0.2942psi/ft and 0.1159psi/ft respectively.
Abnormally high pressure occurred at depth
11106ft (0.6755psi/ft). Aside from the
aforementioned depths, there was moderately
pressure in the well of the formation. Pore
pressure above 0.449psi/ft is said to be
abnormally high pressure (supressure) while
pressures below 0.449PSI/FT is said to be
abnormally low pressure (subpressure). Pore
pressure values below the standard normal
pressure value (0.449psi/ft) in SEKEMI WELL3
show abnormally low pressure while values
above 0.449psi/ft indicate abnormally high
pressure. Depths at 7447ft and 8299ft recorded
abnormally high pressure at pore pressure
0.6264psi/ft and 0.6982psi/ft respectively, while
depths at 9676ft and 10005ft recorded
abnormally low pressure at pore pressure
0.1409psi/ft and 0.2442psi/ft respectively.
CONCLUSION
The has study shown that the standard Eaton‘s
methodology as well as the proposed approach
provides reasonable pore pressure estimations
before and during drilling operations.
In Well A, at depth 6605ft the normal pore
pressure was 0.449PSI/FT and also at depth
9265ft the pore pressure was estimated to be
0.449PSI/FT, while at depth 6682ft, 8914ft,
9547ft abnormal formation pressure was
estimated 0.2686psi/ft, 0.1250psi/ft, and
0.1700psi/ft respectively.
In Well B, at depths 7573ft and 9014ft
abnormally low pressure of 2942psi/ft and
0.1159psi/ft respectively were estimated, while
at depth 11106ft, abnormally high pressure was
estimated to be 0.6755psi/ft.
In Well C, at depths 7447ft and 8299ft
abnormally high pressure was estimated to be
0.6264psi/ft and 0.6982psi/ft respectively, while
at depths 9676ft and 10005ft, abnormally low
pressure was estimated to be 0.1409psi/ft and
0.2442psi/ft respectively.
In conclusion, accurate pore-pressure prediction
in overpressured regions is essential to ensure
safe drilling operations and reduce the cost of
drilling. Pore pressure detection and evaluation
using in-direct method shows that the lower part
of the rollover structure south of a major growth
fault in ‘’Malcolm Field’’ (lower Agbada
Formation) is overpressured. Analysis of sonic
and density log data shows that overpressure in
the field could be inferred to be generated by
disequilibrium compaction based on porosity
anomaly.
REFERENCES
Dutta, N. C., (2002): Geopressure prediction
using seismic data: Current status and road
ahead: Geophysics, 67, pp 2012- 2041.
Eaton, B.A., (1972): The Effect of Overburden
Stress on Geopressure Prediction from Well
Logs SPE 3rd Symposium on Abnormal Pore
Pressure, 1972 SPE paper # 3719
Eaton, B.A., (1975): “The equation for
Geopressure prediction from well logs”
Society of Petroleum Engineers
138
Eyinla D. S, (2011): Reservoir evaluation of
success oil field, offshore Niger Delta,
Nigeria. Unpublished Thesis submitted to
Department of Geology, Adekunle Ajasin
University Akungba Akoko.
Eyinla D. S. and Oladunjoye M. A., (2014):
Estimating Geo-mechanical Strength of
Reservoir Rocks from Well logs for Safety
Limits in Sand-free Production.
Huffman, A.R. (2002): "The future of pore
pressure prediction using geophysical
methods", The leading edge, 21, pp 199-205.
Yoshida C., Ikeda S., Eaton B.A.( 1996): “An
Investigative Study of Recent Technologies
Used for Prediction, Detection, and
Evaluation of Abnormal Formation Pressure
and Fracture Pressure in North and South
America”, paper ADC/SPE 36381, presented
at IADC/SPE Asia Pacific Drilling
Technology Conference, Kuala Lumpur
139
Aquifer vulnerability modelling from geoelectrical derived parameters-case of GODT model
approach
Adeyemo, I. A., Mogaji, K.A., Olowolafe, T. S. and Fola-Abe, A. O.
Department of Applied Geophysics, Federal University of Technology, Akure, Nigeria
ABSTRACT
Aquifer vulnerability assessment was carried at Ipinsa and Okeodu area, Southwestern Nigeria using
geoelectrically derived GODT model. One hundred and two (102) vertical electrical soundings (VES)
data was acquired with Schlumberger array using current electrode separation (AB/2) of 1 to 150 m. The
acquired VES data were qualitatively interpreted to determine the area geoelectric parameters (layer
resistivity and thickness). The geoelectric sections revealing the lithological sequence such as topsoil,
weathered layer, partly weathered/fractured basement and fresh basement underlying the area were
prepared from the interpreted geoelectrical parameter results. Applying the GODT vulnerability model
approach, the aquifer vulnerability index was estimated for the area. Using the kriging interpolation
technique, the GODT index results were used to produce the area aquifer vulnerability map. The
produced aquifer vulnerability map zoned the area into four vulnerable zones namely very low, low,
moderate and high vulnerable classes. The estimated percentage areal coverage for the very low, low,
moderate and high vulnerable classes are 15 %, 40 %, 35 % and 10 %, respectively. The geoelectrically
derived GODT model produced vulnerability map can be useful by the stake holder and the community
policy maker in land use planning and water resources management in the study area.
Keywords: Aquifer vulnerability, GODT model, vertical electrical sounding and geoelectric parameters.
INTRODUCTION
The assessment of groundwater vulnerability to pollution has been the subject of intensive research during the past years and a variety of index methods have been developed to evaluate aquifer vulnerability. These methods include DRASTIC (Aller et. al., 1987), GOD (Foster, 1987), AVI (Van Stempvoort et. al., 1993), SINTACS (Civita, 1994) e.t.c. and are all subjective to varied vulnerability parameters. The derivation of the various parameters required for the computation of the index vulnerability models is usually multi-disciplinary while the accuracy of the resulting models depends majorly on the available information and their authenticity.
Meanwhile, site specific vulnerability assessments using these methods are not readily feasible since in most cases there might not be enough hydrogeological information to compute and thus they are usually applied at regional scale. Consequently, attempt is made in this study to compute hydrogeological parameters from geoelectric parameters for the assessment of aquifer vulnerability at Ipinsa and Okeodu area, near Akure, Southwestern Nigeria. Most geophysical assessments of aquifer vulnerability recorded in the literatures have engaged the use of longitudinal conductance, a second order geoelectric parameter to assess the protective capacity of the overburden units, (Abiola et. al., 2007; Aweto, 2011 and Akintorinwa and
140
Olowolafe, 2013). This approach however, is non-sensitive to the possible presence of relatively high resistive geological formations like laterites that are good protective barriers for the underlying aquifers. More importantly, vulnerability models become more effective as more parameters influencing the disposition of contaminants are available as input for the model. Therefore, four aquifer vulnerability parameters namely groundwater occurrence (G), overlying strata (O), depth to aquifer (D) and topography (T) are integrated in this study to assess the aquifer vulnerability of the study area. The former three parameters GOD has been successfully integrated for aquifer vulnerability assessment in the past (Foster, 1987; Khemiri et. al, 2013) while the fourth parameter (T, topography) is an added input parameter considered to improve the resulting vulnerability model since the topography of an area can influence the migration of contaminants. The ridges usually associated with run-off and less infiltration, while the opposite is the case for depression. Furthermore, studies have shown that contaminants can be topographically controlled whereby contaminants are held downslope by gravity and prevented from migrating upslope (Khemiri et. al., 2013).
2. STUDY AREA
The study area covers two communities namely; Ipinsa and Okeodu situated near Akure Ondo State (Figure 1). It lies within latitudes 70 170
44.71N and 70 190 21.91N and longitudes 50 070
49.231E and 50 090 37.251E. The study area occupies a total area of about 10 km2. The terrain across the study area is undulating with surface elevation ranging between 355 m and 430 m above sea level with more depressions in the southeastern part relative to the northwestern part (Figure 2). The study area is underlain by the Precambrian Basement Complex rocks of Southwestern Nigeria. The two lithologic units recognized in the area include; undifferentiated Older Granite-Charnockites suites and Migmatite-Gneiss-Quartzite complex (Figure 3).
3. METHODOLOGY
One hundred and two (102) Vertical Electrical Soundings (Figure 1) data were acquired in the study area, using PASI 16GL Earth Resistivity Meter and its accessories. The Schlumberger array was adopted for the field survey, with half current electrode spacing (AB/2) varying from minimum of 1 to maximum of 40 to 150m depending on the depth to bedrock and spread allowance. The GODT index which is used to evaluate the aquifer vulnerability in the area was calculated by multiplication of the influence of the four parameters such as Groundwater occurrence (confinement of the aquifer), Overall lithology overlying the aquifer, Depth to the aquifer and Topography of the area. These GOD parameters were interpreted from the geoelectric
141
Figure 1: Base map of the study area showing the Vertical Electrical Sounding (VES) Stations
Inset; Administrative map of Nigeria, (After Obaje, 2009)
Table 1: Attribution of notes for GODT model parameters (modified after Khemiri et al., 2013)
Aquifer Type Note Depth to Aquifer
(m)
Note Lithology (Ω-
m)
Note Topography Note
Non-Aquifer 0 <2 1 <60 0.4 Ridge 0.7-0.8
Artesian 0.1 2-5 0.9 60-100 0.5 Depression 0.9-1
Confined 0.2 5-10 0.8 100-300 0.7
Semi-confined 0.3-0.5 10-20 0.7 300-600 0.8
Unconfined 0.6-1 20-50 0.6 >600 0.6
50-100 0.5
The GODT index was then calculated by
multiplying the influence of the various
parameters together as shown in equation 1
GODT Index = G × O × D x T
Where:
G = Type of Aquifer
O = Overburden Lithology
D = Depth to the Aquifer
T= Topography
Results and Discussion
Figure 4 shows the GODT vulnerability model generated based on four parameters: i) G, groundwater confinement, ii) O, overlying strata, iii) D, depth to the aquifer and iv) T, topography of the area. The ultimate integrated aquifer vulnerability index is the final product of component indices for these parameters (Foster et. al., 2002; Afonso et. al., 2008). The study area was categorized into four ratings viz; very poor, poor, moderate and high vulnerability zones based
142
on the Vulnerability assessment presented in Table 4.3 (Murat et. al., 2003). The vulnerability model shows that major part of the study area falls within the low and moderate vulnerability classes. The most vulnerable zones transect the southeastern axis of the area where low surface elevations are recorded. Thus, the aquifers in these areas are adjudged readily vulnerable to contamination from near surface pollutants.
143
Figure 2: Topographic map of the study area showing VES locations
Figure 3: Geological map of the study area showing the VES points.
144
Table 3: Interval Values of the GODT Index and Corresponding Classes (Modified after Murat et al,
2003).
Index Vulnerability Class
0-0.1 Very Low
0.1-0.3 Low
0.3-0.5 Moderate
0.5-0.7 High
0.7-1.0 Very High
Figure 4: GODT vulnerability map of the study area
5. Conclusion
Aquifer protection is essential for a sustainable use of the groundwater resources, protection of the dependent ecosystems, and a central part of spatial planning and action plans. The key expression for a quantification of aquifer protection is vulnerability. It is in view of this that this research was undertaken to effectively characterize the vulnerability of the underlying aquifers to near surface contaminants around Ipinsa-Okeodu area, near Akure, Southwestern Nigeria. The GODT vulnerability model depicts that the study area is characterized by four vulnerability zones which are very low, low, moderate and high vulnerable zones. According to the model, about 10% of the area is highly vulnerable while about 35% is of moderate rating. The low and very low ratings constitute 40% and 15% respectively of the area. Therefore, it is highly recommended that the least vulnerable zone should be the primary target for future groundwater development in the area in order to ensure continuous supply of safe and potable groundwater for human consumption in the area and more importantly, location of septic tanks, petroleum storage tanks, shallow subsurface piping utilities and other contaminant facilities should be confined to these least vulnerable zones.
145
References
Abiola O., Enikanselu P. A. and Oladapo M. I. (2009). Groundwater Potential and Aquifer Protective Capacity of Overburden Units in Ado-Ekiti, Southwestern Nigeria; International Journal of Physical Sciences, 4 (3) 120-132.
Adagunodo, T. A. and Sunmonu L. A. (2012). Geoelectric Assessment of Groundwater Prospect and Vulnerability of Overburden Aquifers at Adumasun Area, Oniye, Southwestern Nigeria. Arch. Appl. Sci. Res., 4 (5):2077-209.
Afonso, M. J., Pires, A., Chamine, H. I., Marques, J. M., Guimares, L., Guilhermino, L. and Rocha, F. T. (2008). Aquifer Vulnerability Assessment of Urban Areas Using A GIS-Based Cartography: Paranhos Groundwater Pilot Site, Porto, NW, Portugal. 33rd International Geological Symposium: Hydrogeology, Oslo (Norway).
Aller, L., Bennet, T., Lehr, J.H., Petty, R.J. and Hackett, G. (1987). DRASTIC: A Standard System for Evaluating Groundwater Pollution Potential using Hydrogeologic Settings. EPA/600/2-85/018, US Environmental Protection Agency, Ada, Oklahoma, 455pp.
Akintorinwa O. J. and Olowolafe, T. S. (2013). Geoelectric Evaluation of Groundwater Prospect within Zion Estate, Akure, Southwest, Nigeria. International Journal of Water Resources and Environmental Engineering. Vol. 5(1). Pp. 12-28
Aweto, K. E. (2011). Aquifer Vulnerability Assessment at Oke-Ila area, Southwestern Nigeria. International Journal of the Physical Sciences Vol. 6(33), pp. 7574 - 7583,
Baghvand, A., Nasrabadi, T., Nabibidhendi, G., Vosoogh, A., Karbassi, A., Mehradadi N (2010). Groundwater Quality Degradation of an Aquifer in Iran central desert. Desalination 260(3):264-275.
Civita, M., 1994. Le Carte della Vulnerabilità degli acquiferi all inquinamento: Teoria and pratica. Pitagora Editrice, Bologna
Foster, S.S.D. (1987). Fundamental Concepts in Aquifer Vulnerability Pollution Risk and Protection Strategy. In Vulnerability of soil and groundwater to pollution: Proceedings and information. W. van Duijvenboodennd H.G. van Waegeningh (editors).TNO Committee on Hydrological Research, The Hague, 69-86.
Harter, T. (2003). Groundwater Quality and Groundwater Pollution. Publication 8084, http//:anrcatalog.ucdavis.edu.
Hoque, M. A., Khan, A. A., Shamsudduha, M., Hossain, M. S., Islam, T. and Chowdhury, S. H. (2009). Near Surface Lithology and Spatial Variation of Arsenic in the Shallow Groundwater: Southeastern Banglandesh. Environmental Geology, 56, 1687-1695.
Keller, G. V. and F. C. Frishchnecht, (1966). Electrical Methods in Geophysical Prospecting. Pergamon Press, New York, pp. 96.
Koefoed, O., (1979). Geosounding Principles 1. Resistivity Measurements. Elsevier Scientific Publishing, Amsterdam, Netherlands. pp. 275.
Murat, V., Paradis, D., Savard, M.M., Nastev, M., Bourque, E., Hamel, A., Lefebvre, R. and Martel, R., (2003). Vulnérabilité à la nappe des aquifères fractures du Sud-ouest du Québec- Evaluation par les methods DRASTIC et GOD. Current Research, No. 2003-D3, 2003; 14p.
Obaje, N.G. (2009). Geology and Mineral Resources of Nigeria. Published by Springer London. 221p.
Omosuyi, G. O. (2010). Geoelectric Assessment of Groundwater Prospect and Vulnerability of Overburden Aquifers at Idanre, Southwestern Nigeria. Ozean Journal of Applied Sciences 3(1). pp. 19-28.
Omosuyi, G.O. and Oseghale, A. (2012). Groundwater Vulnerability Assessment in Shallow Aquifers using Geoelectric and Hydrogeologic Parameters at Odigbo, Southwestern Nigeria. Am. J. Sci. Ind. Res., 3(6): 501-512
Van Stempvoort D, Ewert L, Wassenaar L (1993). Aquifer Vulnerability Index (AVI): A GIS Compatible Method for Groundwater Vulnerability Mapping. Can Water Res J 18:25–37.
146
Geoelectric soundings for delineation of saline water intrusion into aquifers in part of
eastern Dahomey basin, Nigeria
Adeyemo I.A, Omosuyi G.O and Adelusi A.O Department of Applied Geophysics, Federal University of Technology, Akure, Nigeria
ABSTRACT
This study was aimed at mapping the subsurface extent of saline water intrusions into aquifers at
the eastern part of Dahomey basin, Nigeria. The study adopted geoelectric sounding methods.
108 vertical electrical soundings and 9 induced polarization sounding data were acquired using
Schlumberger array technique. Three aquifer units were delineated across the study area. The
resistivity of the first, second and third aquifer layers vary from 0.2 to 1569 ohm-m, 0.5 to 904
ohm-m and 0.4 to 665 ohm-m respectively, while depth to the top of first, second and third
aquifer vary respectively from 0.7 to 151.5 m, 1.4 to 305.5 m and 12.9 to 452.9 m. The depth to
the first aquifer layer is shallow (less than 5m) in the coastal area which makes this area to be
highly vulnerable to surface pollution while their proximity to Atlantic Ocean makes them
susceptible to saline water intrusion. In all the three aquifer units, the coastal area, Agbabu and
other few locations in the mainland are characterized by low resistivity values (below 60 ohm-m)
indicating possible presence of brackish or saline water. IP sounding results showed that all the
low resistive layers in the mainland are characterized by clayey materials. The integration of all
results enabled the delineation of the saline water lateral extent across the study area. There is a
strong direct correlation (r² = 0.8564) between location distance from the saline water source
and depth to saline water in the study area. This can therefore serve as a predictive model to
determine depth to saline water at any location within the saline water zone in the study area.
Keywords: Saline water intrusion, saline-freshwater boundary, vertical electrical sounding
(VES), induced polarization sounding (IPS) and correlation curve.
INTRODUCTION This study is aimed at mapping saline water
intrusion, subsurface extent of saline water
incursion and fresh-saline water boundary
within aquifer settings in the easternmost
Dahomey basin, covering five Local
Government areas (Odigbo, Irele, Okitipupa,
Ese-Odo and Ilaje in Ondo state, and Ogun
Waterside in Ogun State) in southwestern
Nigeria
Methodology
The study adopted an integrated method
comprising Vertical Electrical Sounding
(VES) and Induced Polarization Sounding
(IPS) and borehole logs analysis. A total of
one hundred and eight (108) VES, using
Schlumberger array were carried out across
the area with maximum current electrode
separation (AB/2) of 750 m. Induced
polarization soundings (IPS) were carried
out in some selected locations requiring
resolution of ambiguities often inherent in
depth sounding interpretation. The IPS
results assisted in resolving the ambiguity of
low resistivities due to clayey materials and
one deriving from brackish/saline water
intrusion.
Results and Discussion
The resistivity at the first aquifer layer
(Figure 2) varies from 0.2 (Obenla) to 1569
ohm-m (Ayadi). In the coastal areas and
Agbabu, Ilubirin and part of Odeaye in the
northern part of the study area, the resistivity
values were below 60 ohm-m suggesting
that the shallow aquifer layer in these areas
might contain brackish or saline water. The
147
IP sounding results gives low chargeability
values within the low resistive layer at
Agbabu, but high value at Odeaye, thereby
confirming possible saline water intrusion
only in Agbabu. That saline water exists in
Agbabu was equally attest to by
hydrochemical analysis earlier carried out
across the study area (Omosuyi, 2001 and
Adeyemo et. al., in press)
The depth to first aquifer layer ranges from
0.7 (Eruna and Molutehin) to 151.5 m
(Itebukunmi). The depth to first aquifer
layer map ((Figure 3) shows that depth to
first aquifer layer is generally shallow (less
than 5m) in the coastal area which is
generally water logged. The first aquifer
layer in this area is highly susceptible to
surface pollution and saline water intrusion
because of its shallow depth, possible poor
protective capacity of the sandy overlying
layer and proximity to the Atlantic Ocean
respectively.
The resistivity of the second aquifer layer
(Figure 4) varies from 0.5 (Molutehin) to
904 ohm-m (Apata Ijaw) ohm-m. The low
resistivity values along this aquifer extends
only to some coastal towns, such as Obe-
Rebiminu, Eruna, Ugbo, Awoye, Gbabijo,
Adagbakuja, Abealala, Ugbonla, Araromi
seaside, Ayetoro, Molutehin and Oretan. It
also extends to the north eastern area such as
Owode road, Iyansan road, Agadagba road1,
Laworo, Legbogbo, Lokaka, and Irele road
and likewise at Odeaye, Oluagbo, Okitipupa
and Idepe in the north central part of the
study area. The IP sounding results again
shows high chargeability values at Odeaye,
Iyansan road and Agadagba thereby
eliminating the possibility of saline water
within the second aquifer layer within the
northeastern area. The depth to second
aquifer across the study area varies from 1.4
(Awoye) to 305.5 m (Owode road). The
depth to second aquifer layer map ((Figure
5) shows that depth to this aquifer layer is
shallow (less than 23 m) at some part of the
coastal areas, such as Obe-Rebiminu,
Figure 1: Geological map of the study area, showing VES and IPS locations
148
Figure 2: First aquifer layer resistivity map
Figure 3: Depth to first aquifer layer map
Araromi Seaside, Temidire, Ugbonla,
Ayetoro, Awoye, Molutehin and Oretan.
Likewise in some places in the mainland the
intermediate aquifer also exists at shallower
depth. Some of these areas are closer to
streams and tributaries which are directly or
indirectly connected to the sea water, such
as in Agbabu, Igbokoda and Aboto. This
probably explains the possible source of
brackish/saline water delineated in these
areas.
Figure 4: Second aquifer layer resistivity
map
Figure 5: Depth to second aquifer layer map
149
The resistivity of the third aquifer layer
(Figure 6) varies from 0.4 (Eruna) to 665
ohm-m (Oriopo). The low resistivity values
along this aquifer layer extends to Araromi
seaside, Obinehin, Gbabijo, Adagbakuja,
Ugbonla, Eruna, Ayetoro, Awoye and
Molutehin in the coastal area. This is
indicative of saline water intrusion in this
area. However in the northeastern part of the
road, Lokaka, Laworo, Agadagba, Arogbo
and Amapere. This probably suggests that at
depth, aquifers in this area will start yielding
brackish to saline water. Again the IP
sounding results have taken care of any
suspicion of occurrence of brackish/saline
water intrusion in these areas based on
chargeability value obtained from these area.
The depth to the third aquifer layer (Figure
7) ranges from 12.9 (Awoye) to 452.9 m
(Arogbo).
The depth to the third aquifer layer is
generally significant (about 100 m) in most
parts of the coastal towns and mainland with
exceptions of Zion, Temidire, Ogoluwayo,
Ebute Ipare and Abealala, the western and
eastern parts of the study area.
Average longitudinal resistivity; a second
order geoelectric parameter was generated
from the primary geoelectric parameters
(Figure 8). The map enabled the delineation
of lateral extent of saline water intrusion
across the study area based on resistivity
values. Low resistivity values (less than 60
ohm-m) were considered brackish to saline
water intruded zone. Saline water extent
map (Figure 9) was generated based on the
three aquifer layer maps and the average
longitudinal resistivity map. The map
project possible extents of saline water
intrusion across the study area. The map
shows that the southeastern part are the
worst hit by saline water intrusion, this
perhaps due to the fact that there are more
tributaries in this area through which sea
water can move land ward.
150
Figure 6: Third aquifer layer resistivity map
Figure 7: Depth to third aquifer layer map
CONCLUSION
A synthesis of the interpretation of the parameters derived from the composite methods
enabled the delineation of brackish/saline-water intruded zone and saline-fresh-water
interface in the study area. The study also enabled the delineation of depth to brackish/saline
water units and their lateral extent in the study area.
REFERENCES
Adeyemo, I.A., Omosuyi, G.O. and
151
Figure 8: Average longitudinal resistivity
map
Figure 9: Saline water extent map
Adelusi, A.O. (In press). Hydrochemical Investigation of Saline Water Intrusion into
Aquifers in Part of Eastern Dahomey Basin, SW Nigeria.
Omosuyi, G.O. (2001). Geophysical and
Hydrogeological Investigations of Groundwater Prospects in the Southern Part of Ondo State,
Nigeria. PhD Thesis, Department of Applied Geophysics, FUTA, Nigeria.195pp.
152
Turonian Global paleosea Incursion: the Benue Trough experience
Saka Adelayo Opeloye
Department of Applied Geology,
Federal University of Technology, Akure
ABSTRACT
Turonian sediments in the Nigerian Benue Trough are reviewed on the strength of being part
of the worldwide Cretaceous transgressive events. Nkalagu, Eze-Akwu, Gongila, Fika and
Dukul Formations bear the imprints of open and shallow marine environments and constitute
the correlative stages to other Turonian beds across the globe. The planktonics are mainly
represented by ammonites occurring as Acanthoceratids and Vascoceratids as well as the
foraminifera Heterohelicids and Hedbergellids. The benthics are also mainly in the forms of
Lituolid foraminifera and Cytherideid ostracods. They are common biotic forms in the basins
adjoining the Mediterranean Europe and North Africa, Brazil, Caribbean and USAWestern
Interior. The benthics are cosmopolitan rather than being endemic on account of dispersal by
the Turonian epeiric sea across Africa as well as the circum-global movement provided by
the nascent Atlantic at the split of Gondwana.
INTRODUCTION
The process of rifting that initiated the
opening of the Atlantic led to marine water
flooding of the nascent Benue Trough in
the mid-Cretaceous Period. Although the
earliest marine or brackish water deposit in
the trough was located in the basal Aptian
Bima Sandstone and the Asu River Group
(Allix et al., 1981), the Turonian stage
marked the maximum highstand of sea
level in the trough record. The Turonian
was also the peak of worldwide
transgression as its imprints were marked
across the West–Central African Rift
System and other basins of the world
(Flexer and Reyment, 1989). Much
referred discussion on such marine related
deposition in Nigeria has been the
Paleocene events in the Taloka, Dukamaje
and Kalambaina Formations of the Sokoto
Basin as influenced by Saharan sea route
(Petters, 1980). Adegoke (1972) also
adduced the combined incursion of the
Guinea and the Saharan sea to the
evolution of Paleocene Ewekoro of the
Benin Embayment. Nevertheless, the
deposition of an earlier Turonian
inundation impacted much on the Geology
of Nigeria and are found embedded only in
the successions of the Benue Trough and
its contiguous Borno Basin. Account of the
deposits in the Benue Trough is hereby
presented and related to similar deposits
elsewhere around the world.
DISCUSSION
Events of the Cenomanian-Turonian
Paleo-sea
The beginning of mid-Cretaceous was
marked by sea incursion world-wide. The
incursion was consequential to series of
Mesozoic thermo-tectonic events that
culminated in the convergent margin
orogenies (the Alpine) and the divergent
rifting (the Atlantic). The activities of the
active collisions lifted the crust at the welt
while the divergence rifted the crust apart
to produce basins at different sections of
the earth. The tectonic activities,
undoubtedly, served as precursors to
cretaceous global warmth. It is on record
that lots of volcanogenic gases were issued
out during the events as greenhouse gases.
Barron (1989) opined that extreme warmth
in this period represents one of the best
examples of "greenhouse" climate
conditions in the geological record.
153
The attendant dramatic rise in sea level led
to the flooding of the continent. During
this period inland sea flooded the mid-
Western part of USA nearly reaching
Canadian border. Much of the central and
western Europe and a larger parts of Africa
including the Benue Trough were
innundated.
Turonian Deposits in the Benue Trough
The Turonian deposits constitute the
typical open marine sediments. In the
southern Benue Trough, the Eze-Akwu
Formation constitutes the Turonian of the
Abakaliki trough. It is a dark grey and
black shale interspersed with siltstone
outcropping along Eziiyiakwu River and
along Calabar-Itu highway. The Formation
also extends to the central Benue Trough
as outcrops occur at Ortesh near
Jangerigeri, along River Tokura-20 km
east of Keana and along Chikinye-Awe
road. Petters and Ekweozor (1982) claimed
that that the formation is correlatable with
units of carbonate and shale successions
observed in the Awgu and Odukpani
Formations as well as in the quarry at the
Nigercem Factory. They therefore
renamed the entire units as Nkalagu
Formation. The spate of subsidence might
have slowed down to allow pockets of
regressive deposits namely Agala
Sandstone, Amaseri and Konshisha
Formations adjoining the extensive
Nkalagu as the trough approached the
central portion.
The enriched sedimentological attributes
of Eze-Akwu Formation, perhaps, was the
basis for its reclassification over time. It
was initially referred to as Eze-Akwu
Group (Geological Survey of Nigeria,
1974). Dessauvagie, (1974) rebranded it as
Eze-Akwu Formation while Petters and
Ekweozor (1982) combined it with the
correlatable Awgu Shale and Odukpani
Formations to form Nkalagu Formation.
The latter alongside inter-digitating
regressive sand bodies of the Amaseri,
Markudi, Agbala and Agbani was
established by the same workers as the
Cenomanian-Santonian Cross River
Group. Nevertheless, Eze-Akwu
Formation as a litho-unit remains the
subject of this study in the southern and
central Benue Trough, as it isochronously
occupies the Turonian.
The formation is composed mainly of
shaly limestone and dark gray fissile shales
with interbeds of laminated as well as
lenticular limestone and siltstone bodies
especially at the limbs of the Abakaliki
Anticlinorium. The outcrops are prominent
along the Ezeyiakwu stream, at Nkalagum,
Okigwi and Akaeze as well as the plains of
Cross River. At the plains of Cross River,
the EzeAkwu Formation occurs in form of
rigdes of sandstone and swales of shales.
The sandstones are cross-stratified,
bioturbated and often with heterolithic
intervals. The shale and the included
limestone of the swales are dark and
contain coquina made of pelecypods and
gastropod shells. Acanthoceratid;
Watinoceras and Mammites nodosoides
typical of the basins in northwest Europe,
the Venezuela and Morocco were
recovered in the carbonate nodules of the
Lokpata black shale. Recovered benthic
forms are Cytheredeid ostracods as well as
the Lituolid foraminifera. The Turonian
diagnostic Cytheredeid Qvocytheridea spp.
is common and diverse. The Lituolid
foraminifera include Trochamina
taylorina, Cassidella tegulata, Ammotium
nkalagum, Ammobaculites benuensis,
Gabonita spinosus, Bolivina anambra and
Ammotium nwaliumwhile recovered
planktonics are Whitenella
154
HOPLOTOIDES
GOMBIOCERAS
PSEUDOSPIDOCERAS
VASCOCERAS
COILOPOCERAS
ACANTHOCERATIDS
VASCOCERATIDS
Fig. 4: Acanthoceratids and Vascoceratids of the Turonian beds of the Benue Trough
10 cm
Ammobaculites bauchensisAmmobaculites irregulariformis Ammobaculites pindigensis
Ammotium nwalium
Ammobaculites benuensis
Ammomaginulina sp.
LITUOLIDS
Ovocytheridea reniformis
Heterohelix reussi
Ovocytheridea apiformis
HETEROHELICIDS
Heterohelix moremani
CYTHERIDIDS
Ovocytheridea symmetrica
Fig. 5: Turonian Lituolids, Cytheridids and Heterohelicids recovered from beds of
Eze Akwu Formation and Fika Shale
155
archeocretacea, Heterohelix reussi H.
pulchraand H. moremani.
The northern portion of the trough
experienced much influence of the marine
deposition as evidence revealed inundation
influences of both Saharan and Atlantic
Gulf of Guinea paleo-sea.
Dukul, Pindiga, Gongila Formations were
deposited as mainly carbonate interspersed
wwith black and dark grey shales
reflecting open and shallow marine sea
deposits. Fika is a shale deposit.
The outcrop at the Ashaka in the Gongola
arm as well as Dukul and Chahakiya
localities in the Dadiya Syncline of the
Yola arm present a good record of the
Turonian event in the northern Benue
Trough. The Ashaka Cement Quarry
consists of both limestone and shale
belonging to Gongila and Fika Formations
respectively with the Cenomanian-
Turonian boundary slightly below the base
of the shale on Gongila Formation
(Gebhardt,1997). Ammonites and
Heterohelicid foraminiferas the
planktonics in both formations are very
distinctive and age diagnostic. The
recovered Acanthoceratids are
Pseudospidoceras, Hoplotoides and
Coilopoceras spp. Fig. 4). In some few
cases, Watinoceras and Mammites spp.
typical of the basins in Europe, Western
Interior of USA and Venezuela are also
encountered. The Vascoceratids are mainly
Gombeoceras and Paravascoceras while
the Heterohelicids are Heterohelix fayosei,
H. moremani, H. reussi. The Lituolid
foraminifera and the Cytheredid ostracods
are the prominent benthics. The Lituolids
are mainly composed of Ammobaculites
sp. While the cytheredeids are the diverse
Ovocytheridea sp. (Fig. 5).The forms
strongly put the considered sections within
the Turonian (Gebhardt, 1997 and 1999).
Similar ammonites and foraminiferal
content is retrieved from the Turonian
outcrops in Dukul and Chahakiya within
the Dadiya Syncline (Opeloye, 2002). In
addition, their limestone beds are
composed of interlayers of wackestones
and packstones with fragments of bivalves,
bryozoans and biogenic impressions.
These attributes suggest deposition in open
marine shallow shelf environment.
156
CONCLUSION
Inundated sea water resulting from global
high stand sea level was at its peak in the
Turonian during the mid-Cretaceous. The
entire portions of northeastern-southwestern
elongated Benue Trough were affected by
the inundation.The lithological and faunal
compositions of the Turonian strata are
comparable with similarly affected basins in
the world. The newly opened Atlantic as
well as sea connection of the Gulf of Guinea
and the Saharan sea wereresponsible for the
similarities in ammonites, foraminifera and
ostracods in north Africa, USA and the
Caribbeans.
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