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

2

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

3

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.

4

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

5

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.

6

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.

7

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:

8

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.

9

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 – tunadeg@yahoo.com/+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: debo_adeseko@yahoo.com)

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: georasheed@gmail.com

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:adewoyeolumidey@gmail.com, johnamigun@yahoo.com

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: adiatnafiu@yahoo.co.uk

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: adeshina4me2000@gmail.com

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:

beamborller@gmail.com

Department of Remote Sensing and GIS, Federal University of Technology, Akure. Email:

aybanifowose@futa.edu.ng

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: aybanifowose@futa.edu.ng; ooaladejana@futa.edu.ng

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: waleexcellent@yahoo.com

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 emokogbue@gmail.com

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: sodaramola@futa.edu.ng **Josh-Tob Geotechnics Engineering Limited,71a Shyllon Street, off Ikorodu road, Ilupeju Lagos.

Email: geofamo@yahoo.com

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.

remiadediji2003@yahoo.co.uk, iyamufelix@yahoo.com, amfakpor@futa.edu.ng (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: ganiyusikiru@gmail.com; osadetunji@futa.edu.ng

Corresponding E-mail: osadetunji@futa.edu.ng

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:goodyojo123@yahoo.co.uk

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: eniolajimoh2@yahoo.com

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: gmolayanju@futa.edu.ng; stay4life2k7@yahoo.com

Corresponding Author: Olayanju, G. M.; Mobile: (+234) 8035923017; E-mail:

gmolayanju@futa.edu.ng

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: bensonolisa@hotmail.com)

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: olowolafetope@gmail.com

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

josumejeh@yahoo.com or joosumeje@abu.edu.ng

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,

support@heritagegeophsyics.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: jo.owoseni@gmail.com; jowoseni@futa.edu.ng

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: abiola1703@gmail.com

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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