research project

SURFACE MAPPING AND INTERPRETATION OF GEOLOGIC UNITS IN LEKWESI, LOKPANTA, AWGU, UGWUEME AND MMAKO AREAS OF

SOUTH EASTERN NIGERIA

BY

TIMI-ODIASE, KINGS U.REG. NO.: 2001/112516

THESIS SUBMITTED TO THE DEPARTMENT OF GEOLOGY FACULTY OF PHYSICAL SCIENCES,

IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD

OF BACHELOR OF SCIENCE, B.Sc. DEGREE

SEPTEMBER, 2006.

TITLE PAGE



ii

APPROVAL PAGE



BY

TIMI-ODIASE, KINGS U.

REG. NO.: 2001/112516

Thesis submitted to the Department of Geology, Faculty of Physical Sciences, in

partial fulfillment of the requirement for the award of Bachelor of Science, B.Sc.

Degree in Geology and Physics.

________________________________________________

MR. D.K. AMOGU DR. H.I. EZEIGBO SUPERVISOR HEAD OF DEPARTMENT

_____________________________

EXTERNAL EXAMINAER

DEPARTMENT OF GEOLOGYUNIVERSITY OF NIGERIA,

NSUKKA

iii

SEPTEMBER 2006.

DEDICATION

This Project Work is dedicated to the Glory of

Almighty God and to the eternal memories of my

grandma – Okponwan and my dearest Aunty – Rita

Obaghayomwan and my biological mother whom…

iv

ACKNOWLEDGEMENT

In God I have and will always trust. I am grateful for the gift of life and

for those around me especially my immediate and extended family and my close

friends given to “us” all by the Creator.

I thank and appreciate the knowledge, support and understanding I

enjoyed from my project supervisor in the person of Mr. Daniel Kalu Amogu

(there could only be few persons like him) and the entire members of staff (both

academic and non-academic) in the Department of Geology, University of

Nigeria, Nsukka.

I am appreciative for the moral and financial support I enjoyed from my

father Mr. Obaghayomwan Rotimi Odiase, and my father’s friend (friend of the

family in Nsukka) Prof. Patrick Obi Ngoddy and his family. They were always

there for me as and when due.

I am grateful to my family, my step-mum, brothers {Martin, Nosawaru

and Osatane}; my sisters {Eghe and Omowa (Faith)}; my grandpa, Pa Erhabor,

Obaghayomwan and the entire large family (the Erhabors’), for space will not

permit me to mention all yours names.

My sincere gratitude to my friends here in school, - Onwuchekwa

Chidiebere and Onyekachi and their family, Ivonye Chukwunonye, Ebirie

Kenneth, Nwogugu Kene (Pope Jones), Onyedire Nice, Aghara Kingsley, Okolo

Ikechukwu, Ojukwu Emeka, Ogbu Emeka, Ude Azor B.C and his family,

Onyekachi Amadi and her family; the entire Ogbu family especially Mr. Luis and

his father; my project group members and my classmates both in Geology and in

Physics. I am sincerely grateful for the help and support I enjoyed in one way or

the other from “you” all – thank you!

v

ABSTRACT

The studied area is bounded by longitude 7o25’E – 7o30’E and latitude 5o55’N –

6o09N; is underlain by three lithologic units; medium-coarse grains sandstone,

mud rock and shale. Tectonic activity that affected the area is responsible for the

presence of deformation as observed in the area eventually resulting to surface

exposure of hydrocarbon around Ugwueme area, thereby destroying any possible

trap mechanism for any of such hydrocarbon accumulation. Thus, the area shows

a general trend of NE-SW and average dip direction with unconformity or

deformation affecting some parts. The studied unit belongs to Owelli/Awgu

Sandstone, Mamu Formation [all cretaceous Campanian-Maastrichtian

sediments]; while the Shale material belongs to Eze-Aku Shale [Turonian–

Coniacian sediment] and the mottled clay belonging to Awgu Ndeaboh Shale

[Santonian Sediment]. Pebbles and Sieve analysis of the medium to coarse

grained sandstone units of Owelli/Awgu Sandstone and Mamu Formation suggest

a tidally influenced fluvial environment though of deltaic origin and the shale of

Eze-Aku and Ndeaboh Nkporo deposited in range of environments ranging from

shoreface to shallow marine environment for the Eze-Aku shale and swamp

environment for Ndeaboh Nkporo Shale.

vi

TABLE OF CONTENTSTitle Page-- -- -- -- -- -- -- -- -- ii

Approval Page-- -- -- -- -- -- -- -- iii

Dedication-- -- -- -- -- -- -- -- -- iv

Acknowledgement-- -- -- -- -- -- -- -- v

Abstract-- -- -- -- -- -- -- -- -- vi

Table of Content-- -- -- -- -- -- -- -- vii

List of Figures-- -- -- -- -- -- -- -- ix

List of Tables-- -- -- -- -- -- -- -- x

List of Plates---- -- -- -- -- -- -- -- xi

Chapter One: Introduction

1.1 Introduction.. .. .. .. .. .. .. .. 1

1.2 Objective of the Study.. .. .. .. .. .. 1

1.3 Scope of the Study.. .. .. .. .. .. .. 2

1.4 Location and Accessibility.. .. .. .. .. .. 3

1.5 Literature Review.. .. .. .. .. .. .. 5

Chapter Two: Regional geologic Setting

2.1 Tectonic Evolution of the Study Area.. .. .. .. 9

2.2 Regional Stratigraphic Setting.. .. .. .. .. 11

2.3 Topology and Drainage Pattern.. .. .. .. .. 14

2.4 Climate, Temperature and Vegetation.. .. .. .. 15

Chapter Three: Outcrop Description

3.1 Introduction.. .. .. .. .. .. .. .. 19

3.2 Lokpaukwu-Lekwesi Study Area.. .. .. .. .. 23

3.2.1 Lokpanta Junction.. .. .. .. .. .. 23

3.2.2 Lokpanta/Awgu Boundary.. .. .. .. .. 25

3.2.3 Lokpaukwu Area.. .. .. .. .. .. 31

vii

3.2.4 Lekwesi Area.. .. .. .. .. .. .. 31

3.3 Ugwueme Area.. .. .. .. .. .. .. 35

3.4 Awgu-Mmaku Study Area.. .. .. .. .. .. 36

3.4.1 Awgu Area.. .. .. .. .. .. ..

36

3.3.2 Mmaku Area.. .. .. .. .. .. .. 38

Chapter Four: Data Presentation and Analysis

4.1 Introduction.. .. .. .. .. .. .. .. 41

4.2 Pebble Morphology.. .. .. .. .. .. .. 41

4.2.1 Methodology and Data Presentation.. .. .. .. 41

4.2.2 Environmental Indication.. .. .. .. .. 43

4.3 Sieve Analysis.. .. .. .. .. .. .. 46

4.3.1 Methodology and Data Presentation.. .. .. .. 46

4.4 Analysis and Results of Sieve Data .. .. .. .. 52

4.4.1 Textural Parameter.. .. .. .. .. .. 57

4.4.2 Environmental Indication.. .. .. .. .. 59

4.4.2.1 Univariate Textural Parameter.. .. .. 59

4.4.2.2 Bivariate Analysis.. .. .. .. .. 63

4.4.2.3 Multivariate Analysis.. .. .. .. 65

Chapter Five: Interpretation and Discussion of Results

5.1 Introduction.. .. .. .. .. .. .. .. 68

5.2 Depositional Environment.. .. .. .. .. .. 68

5.3 Discussion of Shale Result.. .. .. .. .. .. 68

5.4 Tectonic/Structural Attributes in the Study Area.. .. .. 70

5.5 Economic Indications of the Study Area.. .. .. .. 71

Chapter Six: Summary and Conclusion

6.1 Summary and Conclusion.. .. .. .. .. .. 74

Appendixes

viii

References -- -- -- -- -- -- -- -- -- 77

LIST OF FIGURES

Fig. 1.1a: Geologic Framework of Nigeria showing the study area - 3

Fig. 1.1b: Accessibility Map of the Study Area – 4

Fig. 1.2: Structural Units of Southeastern Nigeria {After Short & Stauble, 1967) -6

Fig. 2.1: Tectonic Map of Nigeria during Albian to Lower Santonian -9

Fig. 2.2: Map of South Eastern Nigeria during the Campanian to Eocene – 10

Fig. 2.3: Topology and Drainage Map of the Study Area -16

Fig. 2.4 a, b & c: Various Extraction from Fig, 2.3 showing Cross section,

direction to major locality and geologic formations respectively -17

Fig. 2.5: Temperature / Climatic Map of Nigeria – 18

Fig. 3.1a: Outcrop map of the study area – 21

Fig. 3.1b: Geologic and Outcrop map of the Study Area – 22

Fig. 3.2: Log representation of Unit TOK/SH/01 – 24

Fig. 3.3: Schematic Representation of units, – 29

Fig. 3.4: Litho-log of the studied units and proposed interpretation of

environment of deposition of the units -30

Fig. 3.5: Litholog of Unit in the area [ TOK/SST/03] - 37

Fig. 3.6: Log of Affam Mmku-Ogo study area [TOK/SST/04-05]. -39

Fig. 3.7: Hypothetical (normal) (step-like) fault that affected the Affam Mmaku

Ogo area where the numbering represent the lithologic units in fig. 3.5

above – 40

Fig. 4.1: Plot of MPS against OPI for pebbles collected at Lokpanta/Awgu

Boundary Outcrop – 44

Fig. 4.2: Plot of OPI against FI for pebbles collected at Lokpanta/Awgu

Boundary Outcrop – 45

Fig. 4.3a, b, & c: Plot Representation of Sieve Analysis for Obtaining Modal

Class Size -50

Fig. 4.4: Log Probability Curves for Samples – 53

Fig. 4.5a. : Bivarate Plot of Ski Vs 1 for Samples – 64

Fig. 4.5b. : Bivarate Plot of Mz Vs 1 for Samples – 65

ix

Page No.

LIST OF TABLES

Page

Table 2.1 Regional Sediment cycle of the Anambra Basin and it correlative

counterparts - 14

Table 3.1: Position Description / Outcrop Location and Localities in Study Area

- 20

Table 4.1: Measured and Computed data from Pebbles collected – 42

Table 4.2: Limits of form indices for fluvial and surf processes – 43

Table 4.3a, b, : Summary of Sieve Data and Analysis - 48 , 49

Table 4.4: Data from Log Probability Curves for Statistical Computation – 58

Table 4.5a, b: Summary of Results of Statistical Parameters Obtained From

Grain Size Analysis with their Verbal Interpretation - 61, 62

Table 4.6: Summary of Environment From Multivariate Discriminate Functions

- 67

Table 5.1: Composition of Extracted and Fluid Samples from the Study Area - 69

Table 5.2: TOC Classifications for Source Rock Material - 70

x

D

LIST OF PLATES

Plate 3.1: Shale Outcrop as seen at Lokpanta Junction [ TOK/SH/01] – 23

Plate 3.2 showing Size and shape of typical fossil on exposed outcrop – 24

Plate 3.3: Showing concretions at the exposed outcrop [TOK/SH/01]. – 25

Plate 3.4: Section showing the (A) Cuesta and its trend, (B) exposure with units

labels TOK/MCL/01 and TOK/SST/01. – 26

Plate 3.5: Base of the Mottled Clay as seen in unit TOK/MCL/01 – 27

Plate 3.6: Extraction from Plate 3.4, the b section, showing the sandstone sections

and arrow showing the separation between same unit (this might be due

to incursion of water in the area, which is presently eroding this part of

the exposed outcrop), and where pebbles were collection for textural

analysis – 28

Plate 3.7: Section Extraction from Plate 3.6 above and arrow showing micro

folding structure – 29

Plate 3.8: Exposed Shale outcrop section along Enugu Port–Harcourt Road

[TOK/SH/02] – 31

Plate 3.9: Exposed section of (A) Nkporo Shale covered with vegetation (B)

Dolerite intrusion and (C) entrapped water body around Lekwesi area –

32

Plate 3.10: Dolerite at Crush Stone Industrial Site that intruded the Eza-Aku

Formation as a sill. – 33

Plate 3.11: Shale unit at Lekwesi area (inside Crush Stone Industrial Site)

[TOK/SH/04]. – 34

Plate 3.12: Shale outcrop at Lekwesi area (inside Crush Stone Industrial Site)

[TOK/SH/04] with lines showing folded region and trends of beds

(evidence of Santonian uplift) – 34

Plate 3.13: Oil Show/gas smell spot at Ugwueme [TOK/OSM/01] – 35

xi

Plate 3.14: Showing the studied Units (Awgu Sandstone) at Awgu Town Junction

with arrows showing the trends of beds – 36

Plate 3.15: Bioturbation structures as seen in the outcrop at Station TOK/SST/03

and inner cross bed. – 37

Plate 3.16: Organic Rich Shale at the unit TOK/SH/03 – 38

Plates in Appendixes

Appendix I: Abundant Vegetation land use for agricultural purpose in the Study

Area

Appendix II: (A) Flow out point of the Salt Water (Obilagu Salt water) and (B)

kegs used in collecting these water for local preparation of food at

Lokpanta

Appendix III: Flow out point of the Hard Water at Lokpanta

Appendix IV: Ogbanugwu water fall, which could be used to power a sub hydro

power generating station if developed. At Ogo-Mmaku

xii

CHAPTER ONE

INTRODUCTION

1.1 Introduction

Once there is a depression as a result of tectonic activity, a “basin” is

created and thus sedimentation starts in such a basin. The Anambra basin like

every other sedimentary basins has it peculiar characteristics, which can be

attributed to it geographic location. The basin is 300km NE-SW trending

syncline, located at the southwestern dip of the Benue trough in southeastern

Nigeria. The trough is characteristically linear in shape and its sedimentary

formations are continuous with the Nigerian Coastal Basin. Structurally, the

trough had been thought to be an ordinary rift valley but recently, Burke and

others have attempted to explain its origin in the light of the new ocean spreading

and plate tectonic theory. Their conclusion seems inconclusive owing to non-

availability or insufficiency of data.

The Benue trough in which the Anambra Basin is located at it dip is

marked by a lot of igneous activities. In the cause of this research, the lower

Benue trough outcrop as exposed along the Enugu port-Harcourt express road and

other parts within the study area is studied in detail in order to extract all possible

available information necessary to the field of geosciences.

1.2 Objective of the Study

Objective of the study is to extract all possible information from the study

area as far as the scope permits. They include detailed study of the area in order to

understand the following:

1 Geology of the area;

2 Igneous / tectonic activities and how they contribute to the

deformation of sediments in the area;

1

3 Interpretation of structural pattern in the area; and

4 Hydrocarbon prospects (issues, trend and analysis) in the area.

1.3 Scope and Method of Study

Scope of this research project includes:

1 Detailed field mapping of the study area;

2 Detailed study of the structural trends in the area;

3 Identification of different lithologic unit;

4 Identification of different igneous bodies and their relation to the host

rocks; and

5 Identification of different oil smell and show within the study area.

Method of study employed in this work is grouped into three as follows:

(a) Preliminary Studies / Desk Work

This aspect of the work is basically research on studies that had earlier

been carried out within the study area and also helped in the understanding of the

nature of research that is being carried out currently. This constitutes the early

part of this project.

(b) Field Work

In the field, outcrop are sited, observed and the position is marked using

Global Positioning System (GPS [Garmin-12]), this is followed by detailed

logging of the outcrop taking note of rock type (lateral extent, gross thickness,

bed thickness); textural features (colour, grain size, shape and sorting of grains,

clay content, cementation/compaction if present); sedimentary structures (nature

of bedding, internal structures); tectonic structure (fracturing, joints, fault, folds);

and biologic structures. This constitutes the central part of this project.

2

(c) Laboratory Work and Analysis

Samples of representative outcrops collected from the outcrop site were

sent into research laboratory for proper analysis. This is the most tedious aspect of

the project and is the last part of this project.

1.4 Location and Accessibility

The Anambra basin is large and wide but the area under study is bounded

by latitudes 5o55’ and 6o09’ all north and longitudes 7o25’ and 7o30’ all east. (See

Fig. 1.1a). Other neighboring towns (Awgu, Ugwueme, Mmaku, Ogo, Lekwesi

etc.) bound the area as shown in figs.1.1b.

Fig. 1.1a: Geologic Framework of Nigeria showing the study area

Study Area

Sedimentary Deposit

Basement Complex

3

Fig. 1.1b: Accessibility Map of the Study Area

The study area is mostly accessible by the Enugu Port-Harcourt express road. The

scarp slope of the Enugu Cuesta in the Enugu Okigwe area of the Anambra basin

provides complete and easy accessibility. Representative outcrop are located

along the Lokpanta-Awgu road, Enugu Port-Harcourt express road, and minor

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o00’N

6o05’N

6o00’N

6o05’N

0km 25 km

Lokpaukwu

Lekwesi

Lokpanta

Amaojiacha

Umuelem

Umuchieze

Ugwueme

AWGU

OnoliAwgu Market

Nkwe

Mgbidi

Obeagu

MmakuMarket

Mmaku

Express Road

Old Road

Footpath

Key

4

roads connecting the hinterlands in the study location as show in Fig. 1.1b, which

also connects the main roads and along the old Enugu – Awgu for outcrop located

in Awgu–Mmaku area.

Detailed studies of the outcrops were accessible by track/footpath, minor

roads, road cuts and minor river edge. Although most of the minor roads and

tracks connecting the express way from the hinterland are in bad condition

especially during the wet season owing to the presence of mud underlain beneath

the area, which makes is paramount for trips to be conducted to the study area

during the dry season.

1.5 Literature Review

Anambra basin has been studied by many researchers. It is believed that

the Anambra basin has age ranging from lower cretaceous to upper cretaceous

(Albian to Maastritchtian).

Researchers such as Brynmore (1948), Grove (1951), Barber and Tait

(1963), Jones (1964), Adeleye and Dessauvagie (1970), Peters (1978) Allix

(1983), Whiteman (1982), Benkilli (1989) and more worked extensively on the

lower Benue trough and Anambra basin in particular. They described the

individual or part of the Nigerian sedimentary basins . Short and Stauble (1967)

also noted the stratigraphic units of southeastern Nigeria with their respective

associated age, see Fig 1.2 below.

Grove (1965), Ogbukagu (1977), Nwajide and Hogue (1979) and Egboka

(1985), worked on the lithologic units in order to determine the factors

responsible for the intense gullies prominent in the area.

5

Key

Fig. 1.2: Structural Units of Southeastern Nigeria {After Short & Stauble, 1967)

Reyment (1965) described the Stratigraphy of different depositional basin

in the country and created a large number of lithostratigraphic and

biostratigraphic division of the basins. He also observed in another study that the

Benue trough as a whole is continuous with the coastal basin and that it had been

currently described as the long arm of the Nigeria coastal basin.

6

Carter et al (1963), Cratechlyey and Jones (1965) observed that the area

has a kind of rift structure due to the major fault long it.

Grove (1951) recognized the Nanka Formation as a direct mapable unit

and Kogbe (1976) maintained that the formation has lateral equivalent with the

Ameki Formation while Orjiaka and Ogbukagu (1976) considered the Nanka

Formation as a member of the Ameki Formation.

Murat (1970) presented a paleogeographic description of the Cretaceous /

depositional cycles resulting from the three main tectonic episodes. He also

considered the Anambra basin as a direct consequence of the folding and uplifting

of the Abakaliki / Benue area during the Santonian.

Reyment and Murat (1977) identified not less than 5-transgression in the Benue

trough, four of which are wholly or partly linked to global sea level changes.

Ladipo (1985), Ladipo et al (1994), Hogue (1976 and 1977) and Banergee

(1979) described the sedimentary structures of the Owelli Sandstone to include

large scale tabular cross stratification, wedge shaped trough types of Hummocky

cross stratification.

Arua (1988) wrote that the sedimentary and facies analysis of the Nkporo

Shale of southeastern Anambra basin have been critically interpreted in their

sequence and consists of a marine sequence of black carbonaceous and ammonite

bearing fissile shale inter-bedded with thin beds of sandstone [Peters (1988) and

Arua (1988)].

Arua and Okoro (1989) carried out research on the reconstruction of

paleo-wave and paleo-depth regime of the Nkporo Sea (which is located within

the Anambra basin territory). In their research, they found that the area was

characterized by low velocity wave to moderately-wave denominated period, low

to moderate water of wavelength and low wave height, thus, this part of the

Anambra basin was deposited in hydrodynamic regime of low to moderate

energy.

7

Okoro (1995) considered the Nkporo Shale to be the oldest

lithostratigraphic unit of the Anambra basin and the Afikpo syncline (Reyment

(1965) had earlier stated that it oversteps unconformably.

Nwajide and Reijer (1996) noted that the Enugu Shale of the Nkporo

Group (part of the Anambra basin) is composed of marginal to shallow marine

carbonaceous mudstone and fine sandstone characterized by thin coal seams and

extensive syn-sedimentary deformational structures.

In recent studies, others described the Benue trough of Nigeria to be a

sinistral wrench basin which extends from the Niger Delta in a NE direction to

Lake Chad where it transforms into a predominantly NW trending extensional

basin system through Niger.

Obi and Okogbue (2003 and 2004) described the appearance of soft

sediment deformational structures in the Campano-Maastritchtian succession of

strata in Anambra basin.

8

CHAPTER TWO

REGIONAL GEOLOGIC SETTING

2.1 Tectonic Evolution of the Study Area

During the pre-Cretaceous times, Nigeria consisted of an uplifted

continental landmass made up of the pre-Cambrian basement rocks which were

unconformably overlain by lower cretaceous sediments.

Deposition in the southeastern Nigeria basin during the pre-Maastritchtian

was controlled by the first of the three tectonic phases (Murat, 1970, 72). He also

recorded the three depositional cycles that accompanied each tectonic episode

when the rift-like Benue-Abakaliki trough was formed. The southeastern end of

the basin (Calabar flank) sedimentation was controlled by NW-SE trending fault

(Fig. 2.1) while the western limit of the basin, was the Benin-Benue hinge line

(fault zone) beyond which no marine sediment had been reported.

Fig. 2.1: Tectonic Map of Nigeria during Albian to Lower Santonian{Adapted from Murat 1970}

9

The Abakaliki-trough emerged during Santonian tectonic phase when at the same

time the Anambra basin begin to subside (Fig. 2.1). The Abakaliki trough was

subjected during it’s infilling to tectonic movement which is recorded in the

sediments (Fig. 2.2). A main tectonic episode of compression occurred during the

Santonian, turning the trough into a folded belt. Three main zones of deformation

are running parallel to the main N60oE trend of the trough. From the southeastern

basin edge towards the centre, a diversity of structural styles including fracturing,

open and tight folding with associated cleavages are observed (Fig. 2.2). In most

deformed area, clear evidence of transcurrent movements (indicated by arrow

direction in Fig. 2.2) are found, slumping, syn-sedimentary faulting results from

instability of weakly consolidated sediments. This instability was due to the

presence of a set of major faults in a narrow band located north of Worku Hill in

present day Nasarawa State of Nigeria.

Fig. 2.2: Map of South Eastern Nigeria during the Campanian to Eocene{Adapted from Murat 1970}

10

Until the Santonian, the tectonic regime was favouring transcurrent

movement rather than divergent movement that was responsible for the sinking

and filling of the basin (Burke, 1974). A sharp change to a convergent tectonic

regime with a slight transcurrent component, contributed to the activation of the

N60oE fault as reverse fault resulting in the deformation of the sediment located

in the surrounding of the axial fault system. Thus, uplift, tight folding, cleavage

and low-grade metamorphism characterized the area (i.e. Abakaliki trough, shown

in Fig. 2.2 above). This major event coincided with an important change in the

African plate movement (Burke, 1974) and consequently to the direction of the

Atlantic opening. In the post-tectonic period, a SE to NW polarity relative to the

axial fracture system resulted in the subsidence of the Anambra basin, which

developed north of the Abakaliki uplift. The subsidence is particularly strong and

the basin is the locus of a proto-Niger Delta, which was formed on the stretched

continental margin. The development of the basin was controlled by the N25oE

fault trend, which became dominant in the structural evolution of the region.

2.2 Regional Stratigraphic Settings

The Anambra basin which is in the southern Benue trough, being that the

trough itself is a continental-large scale intra-plate tectonic mega structure, which

is part of the mid-African rift system initiated in the latest Jurassic to early

cretaceous and it is related to the opening of central and south Atlantic ocean

(Murat, 1972). The southern Benue trough comprises the tectonically inverted

Abakaliki anticlinorium, Afikpo and Anambra basin flanking the anticlinorium to

the east and west respectively. The development and evolution of the tectonic, of

the Anambra basin, and the stratigraphic setting of the study area will be better

appreciated by renewing developments in the depositional area since early

cretaceous (Table 2.1) structural unit of the south east Nigeria as represented by

Short and Stauble, 1967 and presented above in Fig. 1.2 above.

11

Albian

The oldest sediment in the southeastern Nigeria is around Abakaliki area.

The sediments are unnamed and constitute part of the Asu River Group (Table

2.1). Reyment, 1965 identified the type area to be the along Asu River. The

sediments consist of Abakaliki Shale with sandstone and rather poorly banded

sandy shale. The fold axis stretch NE-SW. these beds have been recorded to be

associated with lead-zinc mineralization. The shale is deeply weathered and is

found to contain echinoids, some pelycepods and gastropods.

Cenomanian

Beds of this age are restricted to the southeastern portion sedimentary

basin of southeastern Nigeria. They belong to the Odukpani Formation and

consist of arkosic sandstone, limestone and alternating limestone with shale,

which became predominantly shaley in the uppermost part. (Reyment, 1965)

Turonian

Deposits of this age belong to Eze-Aku Formation. The type locality is

the Eze-Aku River Valley in south eastern Nigeria. It consists of hard grey to

black shale and siltstone with frequent facies changing to sandstone or sandy-

shale.

Coniacian-Santonian

The evolution of the Abakaliki basin started with the opening of the Benue

trough in the early Cretaceous with the earliest deposit on the rift floor which are

unnamed base conglomerate of continental origin. They are overlain by the

Albian to Santonian succession suite divisible into the following; Asu River

Group at the bottom, Eze-Aku Formation and Awgu Formation (table 2.1) these

formations are separated by significant unconformities representing the time

12

interval between the major sea incursion. Each succession consists mainly of

shaley lithofacies with large sand bodies (as seen at Mmako village i.e. parts of

the Awgu Sandstone) and subordinate carbonate facies. The Albian Santonian

succession is also associated with basalts, micro diorites and pyroclastics outcrops

exhibiting alkaline to theolitic affinities (Maluski et al, 1995). The succession was

uplifted and became the topographic provenance (Abakaliki Anticlinorium),

which supplied the bulk of the Anambra basin fill (Hogue, 1977).

Campanian-Maastritchtian

The thermal regime responsible for the Santonian upliftment remained

active until the end of the Eocene. The period is characterized by spasmodic

quakes in the Abakaliki region (Agagu et al, 1985) and corresponding

transgression and regression in the Anambra basin (Peters, 1978). These events

along with the paleomorphology of the southern Benue trough and proximity of

sediment source area, controlled sedimentation and paleogeographic

reconstruction of the Anambra basin (table 2.1). Campanian sediments probably

belong to the base of Nkporo Formation. The filling of the Anambra basin took

place during the two-depositional cycles from the Campanian to early

Maastrichtian to Eocene (Petters, 1978). The commencement of the Campanian-

Maastrichtian is marked by a short transgression followed by a regression (Short

and Stauble, 1967).

Resting upon the Awgu Shale is the Nkporo Group comprising shale

facies (the Nkporo Shale), a shallowing upward sand, Owelli Formation

(Campanian-Maastrichtian) and marsh shale represented by the Enugu Shale. The

Nkporo Group is overlain by succession of parallel sandstone series of Mamu

Formation.

13

Table 2.1 Regional Sediment cycle of the Anambra Basin and it correlative counterparts

AGE (m.y) ABAKALIKI – ANAMBRA BASIN AFIKPO BASIN

33.7 Oligocene Ogwashi-Asaba Formation

Ogwashi-Asaba Formation

54.8 Eocene

Ameki/Nanka Formation/Nsugbe Sandstone Ameki Formation

65.0Paleocene

Imo Formation

Nsukka Formation

Ajali Formation

Mamu Formation

Imo Formation

Nsukka Formation

Ajali Formation

Mamu Formation72.0

Maastrichtian

Nkporo Owelli Formation / Enugu Shale

Agbani Sandstone

/ Awgu Shale

Nkporo Shale / Afikpo Sandstone

83

86.0

Campanian

Santonian

89.0

94.0

99.0112.2

121.0127.0132.7

Coniacian

Turonian

Cenomanian –Albian

Aptian Barremian Hauterivian

U n - n a m e d U n i t s

P r e c a m b r i a n B a s e m e n t C o m p l e x

{Modified after Reyment, 1965}2.3 Topology and Drainage Pattern

Hilly and low lands characterize the study area (fig. 2.4a,b, and c). The

area is located at the gentle westward dip slop of the Enugu Cuesta and it runs

Non-deposition/erosion

Eze Aku Group

Ezeaku Group (incl. Amasiri Sst).

Asu River Group

Asu River Group

14

through the area. The Cuesta is one of the three main landforms occurring in the

southeastern Nigeria, others are Cross-river Plains and the Niger-Imo low lands.

The entire study area is drained by three main rivers which are Oji, Miuna

and Nyana Rivers. These constitutes the major attributes of the Mamu and Imo

rivers which are the major river bounding the study area. Rivers Ajali, Oji,

Miuna, Azata and Nyana are the major rivers that drain the area. These rivers all

drain into River Niger (Fig. 2.3).

The drainage density varies depending on the geologic formation that

underlies the part of the study area under consideration. The drainage intensity is

higher at areas underlain by mud rocks than in area areas that are underlain by

sandstone. Mamu Formation, drainage and channel frequency are very high

whereas in the Ajali sandstone, there is paucity of surface drainage owing to the

high infiltration capacity of the sandstone formation. These stream flows through

the V-shaped gullies of the sandstone as well as through the well resistant

sandstone of the Nkopro Group (within the area), creating new gullies and

making the older once deeper. It is also seen that from the drainage figure (Fig.

2.3), that the pattern is dendritic and the streams are perennial. However, flow

rates and ground water table reduce during the dry season due to very low

recharge.

2.4 Climates, Temperature and Vegetation

The rainy season starts from April and run through the end of July, a short

break in August and then another rainy season from September to October

followed by dry season from November to March.

Inyang (1975) noted that the study area lies within the tropical forest of

Nigeria and he also noted that the region has four dry months in which

precipitation is less than 60mm while the annual total ranges between 1875mm

and over 2560mm. The main annual temperature in the area is 26.6oC and a

15

maximum range in altitude is about 1800ft. During the first quarter month, the

temperature normally rises to about 37.67oC and reaches its maximum towards

the end of the dry season. (Fig. 2.5) The august break is associated with the

0km 25 km

300 Contour lineRiver/

Streams

A

B

Key

Fig. 2.3: Topology and Drainage Map of the Study Area

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o00’N

6o05’N

6o00’N

6o05’N

Lokpaukwu

Lekwesi

Lokpanta

Amaojiacha

Umuelem

Umuchieze

Ugwueme

AWGU

OnoliAwgu Market

Nkwe

Mgbidi

Obeagu

MmakuMarket

Mmaku

300

300

300

400

400

400

400

400

500

500

500

500

60070

080012

00

600

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600

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700

700

700

800

800

750

900

1000

900

1100

800

700

900

800

1000

1400

700

1100

900

Mmabu River

Obe Stream

Obe River

Ezia River

Mamu River

Ochi River

Idimok

e River

1200

1400

Otutu River

0km 25 km 0km 25 km


Streams


Streams

A

B

Key

Fig. 2.3: Topology and Drainage Map of the Study Area

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o00’N

6o05’N

6o00’N

6o05’N

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o00’N

6o05’N

6o00’N

6o05’N

Lokpaukwu

Lekwesi

Lokpanta

Amaojiacha

Umuelem

Umuchieze

Ugwueme

AWGU

OnoliAwgu Market

Nkwe

Mgbidi

Obeagu

MmakuMarket

Mmaku

300

300

300

400

400

400

400

400

500

500

500

500

60070

080012

00

600

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700

800

800

750

900

1000

900

1100

800

700

900

800

1000

1400

700

1100

900

Mmabu River

Obe Stream

Obe River

Ezia River

Mamu River

Ochi River

Idimok

e River

1200

1400

Otutu River

16

A

Ele

vatio

n (m

eter

s)

7o25’E 7o30’E

400

200

600

1000

800

1200

1400

1600

B

Awgu Shale

Nkporo Group

0

Fig.2.4a: Extraction from Fig. 2.3, Cross-section of Study Area (A-B)

Maastrichtian

A

Ele

vatio

n (m

eter

s)

7o25’E 7o30’E

400

200

600

1000

800

1200

1400

1600

B

Eze-Aku sahe

Owelli Sandstone/ Awgu Sandstone

Agbani Sst.

0Awgu Ndeaboh Shale

7o26’E 7o27’E 7o28’E 7o29’E

Agbani Sandstone

Asata Nkporo Shale Mamu Formation

Cam

panian

Santonian

Coniacian

Fig.2.4c: Extraction from Fig. 2.3, Showing Formations/Geologic Units and Age

0km 25 km

A

Ele

vatio

n (m

eter

s)

7o25’E 7o30’E

400

200

600

1000

800

1200

1400

1600

B0

Fig.2.4b: Extraction from Fig. 2.3, Showing direction from Cross section to major Localities

Lokpanta area

Lokpanta areaLekwesi area

Awgu Area

Lokpaukwu Area

Ugwueme

NkweMgbidi

Mmaku

A

Ele

vatio

n (m

eter

s)

7o25’E 7o30’E

400

200

600

1000

800

1200

1400

1600

B

Awgu Shale

Nkporo Group

0

Fig.2.4a: Extraction from Fig. 2.3, Cross-section of Study Area (A-B)

Maastrichtian

A

Ele

vatio

n (m

eter

s)

7o25’E 7o30’E

400

200

600

1000

800

1200

1400

1600

B

Eze-Aku sahe

Owelli Sandstone/ Awgu Sandstone

Agbani Sst.

0Awgu Ndeaboh Shale

7o26’E 7o27’E 7o28’E 7o29’E

Agbani Sandstone

Asata Nkporo Shale Mamu Formation

Cam

panian

Santonian

Coniacian

Fig.2.4c: Extraction from Fig. 2.3, Showing Formations/Geologic Units and Age

0km 25 km 0km 25 km

A

Ele

vatio

n (m

eter

s)

7o25’E 7o30’E

400

200

600

1000

800

1200

1400

1600

B0


Lokpanta area


Awgu Area

Lokpaukwu Area

Ugwueme

NkweMgbidi

Mmaku

A

Ele

vatio

n (m

eter

s)

7o25’E 7o30’E

400

200

600

1000

800

1200

1400

1600

B0


Lokpanta area


Awgu Area

Lokpaukwu Area

Ugwueme

NkweMgbidi

Mmaku

17

Scrub land

Sudan Savannah

Guinea Savannah

Tropical Forest

Fresh Water Swamp

Mangrove Swamp Forest

KEY:

inversion in the tropical meantime air mass gives the air mass little incentive to

rise and cause conventional rainfall giving rise to humidity.

Across the country generally, Adetoro (1972) noted that the entire land

mass is divided into 5-main vegetation i.e. from the south end, the swamp forest,

the high forest, the semi-desert forest, the grasslands and the semi-desert

scrubland at the northern part. (Fig.: 2.5). The study area cut across Guinea

Savannah and tropical forest which lies between the deciduous forest and the high

forest and are characterized by thick to very thick and high evergreen trees mainly

hardwood. This thick vegetation is due to the high annual rainfall and constantly

moderate temperature within the study area. Below the level of the high trees,

there is layers of smaller tress and characterized by dense overgrowth of creeping

plants and parasites.

Fig. 2.5: Temperate / Climatic Map of Nigeria (modified after Adetero)

18

CHAPTER THREE

OUTCROP DESCRIPTION

3.1 Introduction

Outcrop in the study area is sparsely distributed, as shown in Fig. 3.1. The

locations (position and elevation values) of outcrops studied were obtained from

the field using the CG-12 Global Positioning System (GPS). The data as collected

from the field are tabulated in Table 3.1.

Three main lithologies were identified in the entire study area. They

include sandstone, shale and mottled clay. Other geologic features within the

study area include salt water located at Lekwesi area. Also distributed in the area

were buckets of dolerite intrusions. Quarrying activities that are going on in the

vicinity of the intrusions exposes these dolerites. Effects of Santonian uplift that

has been reported by other authors were also observed in some parts of the study

area. The structural implications of some of the observed trends will be discussed

in the appropriate section of this work.

The entire study area was uplifted making most of the studied outcrop to

be dipping to nearly vertical as recorded around the Lokpanta / Awgu Boundary,

parts of Lokpanta–Lekwesi area and the Awgu–Mmaku areas. The GPS data as

obtained from the field is presented below in Table 3.1.

GPS VALUE ALTITUDE OF OUTCROPMap Station Code Locality Lat. (oN) Long. (oE) Altitude Strike Dip Dir.

19

S/N(m) Dir. (Az) (Az)

1 TOK/RJ/01 Lokpanta Junction 5o58'39'' 7o27'26'' 122.8 - -2 TOK/SH/01 Lokpanta 5o58'39'' 7o27'38'' 129.2 218 3083 TOK/WTR/01 Lokpanta 5o59'13'' 7o27'47'' 101.5 - -4 TOK/SWT/01 Lokpanta 5o59'18'' 7o26'34'' 140.2 - -5 TOK/MCL/01 Lokpanta/ Awgu Boundary 6o01'05'' 7o28'13'' 118.9 213 3036 TOK/SST/01 Lokpanta/ Awgu Boundary 6o01'08'' 7o27'56'' 153.6 210 3007 TOK/SH/02 Lokpaukwu Area 5o56'25'' 7o25'31'' 152.4 - -8 TOK/SH/03 Lekwesi Area 5o56'06'' 7o25'15'' 166.7 - -9 TOK/WTP/01 Lekwesi 5o56'03'' 7o25'25'' 139 - -10

TOK/SH/04 Lekwesi 5o56'41'' 7o29'02'' 97.8 205 29511 TOK/SST/02 Ugwueme 6o01'53'' 7o27'13'' 219.5 209 29912 TOK/OSM/01 Ugwueme 6o01'47'' 7o27'18'' 173.7 - -13 TOK/RJ/02 Awgu –Mmaku 6o05'15'' 7o28'30'' 21614 TOK/SST/03 Awgu –Mmaku 6o05'17'' 7o28'28'' 196.6 186 27615 TOK/SST/04 Affam Ogo Mmaku 6o08'07'' 7o28'23'' 347.516 TOK/SST/05 Ogo Area 6o08'12'' 7o28'33'' 25617 TOK/SST/05 Ogo Area 6o08'16'' 7o28'28'' 355.118 TOK/SH//03 Ogo Area 6o08'14'' 7o28'24'' 41019 TOK/SST/05 Ogo-Mmaku 6o08'12'' 7o28'19'' 403.9 201 29120 TOK/HDW/1 Ogo-Mmaku 6o08'14'' 7o28'21'' 423.721 TOK/WF/01 Ogbanugwu 6o08'27'' 7o28'03'' 313.6

KEY TOK=> Timi-Odiase, KingsSST=> Sandstone : OSM => Oil Smell : MCL => Mottled Clay :

SWT => Salt WaterWTR => Water : WTP => Water Peat : SH => Shale

: RJ = Road JunctionHDW => Hand Dug Well : WF => Water Fall

Table 3.1: Position Description / Outcrop Location and Localities in Study Area20

0km 25 km


Streams

Key

Fig. 3.1a : Outcrop Map of the Study Area

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o05’N

6o00’N

6o05’N

Lokpaukwu

Lekwesi

Lokpanta

Amaojiacha

Umuelem

Umuchieze

Ugwueme

AWGU

OnoliAwgu Market

Nkwe

Mgbidi

Obeagu

MmakuMarket

Mmaku

300

300

300

400

400

400

400

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500

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080012

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70070

0

700

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1100

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900

800

1000

1400

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900

Mmabu River

Obe Stream

Obe River

Ezia River

Mamu River

Ochi River

Idimok

e River

1200

1400

Otutu River2

1

12

4

56

11

3

10

78

9

1413

1518

1619

17 20 21

Studied Outcrop

Other geologic Feature

Express Road

Old Road

Footpath

Dolerite Intrusion

800

0km 25 km 0km 25 km


Streams


Streams

Key

Fig. 3.1a : Outcrop Map of the Study Area

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o05’N

6o00’N

6o05’N

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o05’N

6o00’N

6o05’N

Lokpaukwu

Lekwesi

Lokpanta

Amaojiacha

Umuelem

Umuchieze

Ugwueme

AWGU

OnoliAwgu Market

Nkwe

Mgbidi

Obeagu

MmakuMarket

Mmaku

300

300

300

400

400

400

400

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080012

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Mmabu River

Obe Stream

Obe River

Ezia River

Mamu River

Ochi River

Idimok

e River

1200

1400

Otutu River2

1

12

4

56

11

3

10

78

9

1413

1518

1619

17 20 21

Studied Outcrop


Express Road

Old Road

Footpath

Express Road

Old Road

Footpath

Old Road

Footpath

Dolerite Intrusion

800

21

0km 25 km


Streams

KEY

Fig. 3.1b : Geologic and Outcrop Map of the Study Area

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o05’N

6o00’N

6o05’N

Lokpaukwu

Lekwesi

Lokpanta

Amaojiacha

Umuelem

Umuchieze

Ugwueme

AWGU

OnoliAwgu Market

Nkwe

Mgbidi

Obeagu

MmakuMarket

Mmaku

300

300

300

400

400

400

400

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1400

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900

Mmabu River

Obe Stream

Obe River

Ezia River

Mamu River

Ochi River

Idimok

e River

1200

1400

Otutu River2

1

12

4

56

11

3

10

78

9

1413

1518

1619

17 20 21

Studied Outcrop


Express Road

Old Road

Footpath

Dolerite Intrusion

800

Map Drawn ByTimi-Odiase, Kings .U.2001/112516Geology/Physics

Eze-Aku Shale

Agbani Sandstone

Awgu NdeabohShale

Geologic Boundary

Awgu Sandstone

Asata NkoroShale

MamuFormation

0km 25 km 0km 25 km


Streams


Streams

KEY

Fig. 3.1b : Geologic and Outcrop Map of the Study Area

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o05’N

6o00’N

6o05’N

5o55’N

6o09’N

7o25’E 7o30’E5o55’N

7o25’E 7o30’E6o09’N

6o05’N

6o00’N

6o05’N

Lokpaukwu

Lekwesi

Lokpanta

Amaojiacha

Umuelem

Umuchieze

Ugwueme

AWGU

OnoliAwgu Market

Nkwe

Mgbidi

Obeagu

MmakuMarket

Mmaku

300

300

300

400

400

400

400

400

500

500

500

500

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080012

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600

600

600

600

600

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1300

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70070

0

700

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800

900

1000

900

1100

800

700

900

800

1000

1400

700

1100

900

Mmabu River

Obe Stream

Obe River

Ezia River

Mamu River

Ochi River

Idimok

e River

1200

1400

Otutu River2

1

12

4

56

11

3

10

78

9

1413

1518

1619

17 20 21

Studied Outcrop


Express Road

Old Road

Footpath

Dolerite Intrusion

800

Map Drawn ByTimi-Odiase, Kings .U.2001/112516Geology/Physics

Eze-Aku Shale

Agbani Sandstone

Awgu NdeabohShale

Geologic Boundary

Awgu Sandstone

Asata NkoroShale

MamuFormation

(See enlarged map at the back of this project)

22

3.2 Lokpanta – Lekwesi Study Area

3.2.1 Lokpanta Junction

The outcrop is a roadside exposure located 150m to Lokpanta junction

along the Enugu - Port-Harcourt express road. It has lateral extent of about 170m

and gross thickness of about 15m.The outcrop is grayish, fissile shale and appears

to have been tilted and also affected by heat at some of the areas in which it is

outcropping. The outcrop is labeled TOK/SH/01 (i.e. outcrop number 2 on the

geologic map (Fig. 3.1a and 3.1b) with position and altitude values as presented in

table 3.1 above. The slate-like nature of the outcrop is indicative of the very low

stage of metamorphism it has undergone. Some other sections of same outcrop

are also seen to contain concretions (iron-rich) as shown in Plate3.3. This material

must have been deposited in a very quiet environment to give room for such

accumulation. Some section of the outcrop contains a lot of fossil (see Plate 3.2

below). The log of the outcrop is also represented in Fig. 3.2.

Plate 3.1: Shale Outcrop as seen at Lokpanta Junction [ TOK/SH/01]

23

Plate 3.2 showing Size and shape of typical fossil on exposed outcrop.

Lithology Structures DepositionalEnvironment

CL FST MS CS CGL

5

10

15

20

(m)

Unit 2 (TOK/SST/01)

23o

Shallow Marine

Slatted and contains microfossil

Fig. 3.2: Log representation of Unit TOK/SH/01

24

Plate 3.3: Showing concretions at the exposed outcrop [TOK/SH/01].

3.2.2 Lokpanta / Awgu Boundary

The exposures at this locality are dominantly mottled clay [TOK/MCL/01

(number 5 in the map)] and sandstone [TOK/SST/01 (number 6)]. The clay dips

at 6o while the sandstone is dipping at 72o forming angular unconformity between

the two units as shown in fig. 3.3 below. The sandstone consists of many units

distinguished based on some lithic characteristics. These units are described

below. Some schools of thought have attributed the unconformity to be an uplift,

depicting the Santonian uplift which affected area (i.e the lower dip of Benue

trough – Anambra Basin, Reyment, (1965)). See Plate 3.4 below.

25

Pl

ate

3.4: Section showing the (A) Cuesta and its trend, (B) exposure with units labels

TOK/MCL/01 and TOK/SST/01.

Unit 1 (TOK/MCL/01)

This unit is an exposure of mottled clay exposed along a gully. It has long

lateral extent which approximates to thickness of about 15m. The outcrop is

grayish with strips of reddish stains. The unit is shown on Plate 3.5

A

B

A

26

Plate 3.5: Base of the Mottled Clay as seen in unit TOK/MCL/01

Unit 2 (TOK/SST/01)

As seen in the log (Fig. 3.3), this section is on top of unit 1 and has

position values slightly seconds difference from Unit 1 (above). It is shown in

Plates 3.6, and Plate 3.7. other details are presented in Table 3.1. The subunits of

Unit 2 are discussed below

Unit 2a is sandstone, medium to coarse grain with thickness of about

0.95m. It is massive and whitish in colour.

Unit 2b is a massive light coloured fine grained sandstone with thickness

of about 0.7m.

Unit 2c is a massive sandstone with fined grain texture and shows

alternation of colours with about 6.1m thickness.

Unit 2d is fine to medium grained sandstone with inter layered mudstone.

The Unit is about 5.6m thick.

27

Unit 2e is mudstone with alternating bands of sandstone. It is massive and

has thickness of about 6.6m

Unit 2f is sandstone, medium to coarse grain with about 15m thickness. It

is also massive.

In all Units 2, with total thickness of about 34.95m, has one peculiar thing

about them i.e., the entire rock units has same altitude i.e they are nearly vertical

to vertical at the point at which measurement and position values were obtained,

see Table 3.1 above, while hypothetical diagramme of the section is attempted

below as Fig 3.3.

The representative log of these units is presented as Fig. 3.4 below.

Plate 3.6: Extraction from Plate 3.4, the b section, showing the sandstone sections and arrow showing the separation between same unit (this might be due to incursion of water in the area, which is presently eroding this part of the exposed outcrop), and where pebbles were collection for textural analysis.

28

A

B

C

D

Plate 3.7: Section Extraction from Plate 3.6 above and arrow showing micro folding structure

Fig. 3.3: Schematic Representation of units, ABCD representing hypothetical fault plane,

29

Studied section and possible orientation of the units in Fig. 3.3 below, arrows showing their direction of motion.

Fig. 3.4: Litho-log of the studied units and proposed interpretation of environment of deposition of the units

Lithology StructuresDepositionalEnvironment

Unit 2 (TOK/SST/01)

CL

FST MS CS

CGL

(m)

5

10

15

20

25

30

35

40

45

50

Unit 1 (TOK/MCL/01)

72 o Massive

Massive

MassiveShallow Marine

Shoreface Sands

Beach Sands

6 o

Unconformity

30

3.2.3 Lokpaukwu Area

This station is label TOK/SH/02, which is part of the Nkporo Shale

exposed along Enugu-Port-Harcourt express road around Lokpaukwu area. The

outcrop is grey to black shale and massive. It has positions as presented in Table

3.1 above. See plate 3.8. This shale is very thick (about 25m). This outcrop must

have been deposited is a very quiet environment.

Plate 3.8: Exposed Shale outcrop section along Enugu Port–Harcourt Road [TOK/SH/02]

3.2.4 Lekwesi Area

31

This station is label TOK/SH/03 and is located around Lekwesi area. It is

shale and close to section TOK/SH/02. This is actually an exposure of Nkporo

Shale at the Lokpaukwu area but shows peculiar characteristics. This Shale is

underlain by dolerite intrusion. The quarrying of this dolerite lead to the

entrapment of large body of water for the locality, shown in Plate 3.9.

Plate 3.9: Exposed section of (A) Nkporo Shale covered with vegetation (B) Dolerite intrusion and (C) entrapped water body around Lekwesi area.

Further from this location where the dolerite is outcropping, we have

evidence of the Santonian uplift as seen present at Crush Stone Industrial site in

Lekwesi area (Plate 3.10 and 3.11). All position values measure is presented in

Table 3.1

Evidence of the Santonian uplift in the Abakaliki area was seen at the

Crush rock Quarrying site at Lekwesi Umuchieze. At this location (Plate 3.10),

C

B

A

32

dolerite sill was found to have intruded into materials of Eze-Aku Formations.

These materials consist of shale interbeded with thin layers of siltstone and the

sandstone (Plate 3.11). Attitude measurement of beds indicates that the dolerite

dip west consistent with beddings. This resulted to thicker over burden thickness

to the west. There is obvious evidence of Santonian folding as shown by the

presence of tight isoclinal fold in the shale (Plate 3.12). The exposed material

here appears like limb of a major fold.

Plate 3.10: Dolerite at Crush Stone Industrial Site that intruded the Eza-Aku Formation as a sill.

33

Plate 3.11: Shale unit at Lekwesi area (inside Crush Stone Industrial Site) [TOK/SH/04].

Plate 3.12: Shale outcrop at Lekwesi area (inside Crush Stone Industrial Site) [TOK/SH/04] with lines showing folded region and trends of beds (evidence of Santonian uplift)

3.3 Ugwueme Area

The outcrop in this area is a hillside exposure of sandstone. Though the

exposure was not studied in detail, samples were collected so as to obtain textural

parameters, with position and attitude as presented in Table 3.1 above. The sand

dips 28o to the west, having strike direction of 209Az and dip direction of 299Az,

and consists of fine to medium grained sizes. About 36.57m below the position of

the sandstone unit exposed along the hill are very big boulders of consolidated

coarse massive sandstone at the base of the scare face of the Cuesta in the area.

This position is where the oil seep/gas smell is located at Ugwueme (Plate 3.13).

The presence of the boulder and the oil seep may probably indicate the presence

of a fault.

34

Plate 3.13: Oil Show/gas smell spot at Ugwueme [TOK/OSM/01]

3.4 Awgu – Mmaku Study Area

The dominant Lithology in this area is sandstone. The sandstone is greatly

deformed from the sections that were seen and studied.

3.4.1 Awgu Area

Outcrop in this region of the study area is label TOK/SST/03 (Plate 3.14).

It was seen to be outcropping at three different locations, all displaying the same

trend (as detailed in table 3.1) with some area displaying evidence of bioturbation.

Ichnofossil such as Ophiamopha was seen at station TOK/SST/03 as shown in

Plate 3.15. The outcrop is weathered, poorly sorted sandstone and it is medium to

coarse grain, with most of the grains highly visible to the naked eyes at some

areas of the outcrop. The units are striking 186Az, with dip direction 276az and

35

dip amount 12o, with the units display variations along east to west i.e east coarser

than the western side of same outcrop. The sandstones are reddish brown to white

in colour, massive and clean. Further details are outlined in the log of the section

as shown in Fig. 3.5 below.

Plate 3.14: Showing the studied Units (Awgu Sandstone) at Awgu Town Junction with arrows showing the trends of beds

36

LithologyStructures

DepositionalEnvironment

CL FST MS CS CGL

4

8

12

16

(m)

Massive (poorly sorted)

Bioturbated (horizontal, nearly vertical and )

Massive (poorly sorted)

Massive (moderately well sorted)

Massive / consolidated(poorly sorted) & presence of cross beds

Shoreface

12o

Plate 3.15: Bioturbation structures as seen in the outcrop at Station TOK/SST/03 and inner cross bed.

Fig. 3.5: Litholog of Unit in the area [ TOK/SST/03]

37

3.4.2 Mmaku Area

This area of the study area shows a great evidence of deformation (more

of faulting) especially around the Affam Mmaku - Ogo town. A lot of geologic

features were encountered in this area most of these features seen at this location

are appended to this project as Appendixes. Shale (plate 3.15) and sandstone were

the main litho-units seen here. The log is presented in Fig. 3.6 and a schematic

representation of the orientation of the beds in Fig. 3.6. The first sand has

position and altitude as outlined in table 3.1 above and strikes at 201Az, dip

direction of 291Az with dip amount of 09o. It has estimated gross thickness of

about 130m. It is medium to coarse sand and reddish brown to white. The

sandstone is overlain by fissile shale, grey to black with thickness of about 20m

with as shown in plate 3.16, and the top of this unit, another sandstone body of

about 2.5m thick medium to coarse and brown in colour.

Plate 3.16: Organic Rich Shale at the unit TOK/SH/03

38

Lithology Structures DepositionalEnvironment

CL

FST MS CS

CGL

(m)

20

40

60

80

100

120

140

160

180

200

Massive

Massive

Shallow marine

??

Shoreface Sand

09o

Fig. 3.6: Log of Affam Mmku-Ogo study area [TOK/SST/04-05].

The sand at the base, going by the lithstratigraphic table presented above

as Table 2.1, depicts the Awgu Sandstone. Around this area also, there is a hand

dug well that has depth to water surface of about 5.1m. Table 3.1 show further

details., also, around this region, we have the Ogbnugwa Water fall as it is

39

32 (Shale1

3

2

1

Proposed Fault Plane for the Agbani Sandstone

popularly called by the locality and it shows flow direction of 20oN. The water is

relatively soft clean water and can be utilized for domestic and agricultural

purposes. Also close to this water fall is a minor water fall this is dirty colour and

relatively hard. The step-like nature of our decending from height of about

365.78m to 213.36m and the sharp drop to about 121.9m suggests a step like

normal fault in the area. (Fig. 3.7)

Fig. 3.7: Hypothetical (normal) (step-like) fault that affected the Affam Mmaku

Ogo area where the numbering represent the lithologic units in fig. 3.5 above.

40

CHAPTER FOUR

DATA PRESENTATION AND ANALYSIS4.1 Introduction

This chapter will focus on the presentation of the results obtained from the

analysis of the samples collected from the study area.

4.2 Pebble Morphology

4.2.1 Methodology and Data Presentation

A total of 31 pebbles were collected from distinct pebble horizon within

the Awgu Sandstone. During sampling all pebbles with distinct fresh breaks,

obvious primary elongation or flatness, and those that showed strong lithologic

inhomogeneities were discarded to assure true values of the desired parameters

(Sames, 1966).

The three mutually perpendicular axes: the long (L), the intermediate (I),

and the short (S) axes of each pebble were measured with the veneer calipers as

suggested by Dobkins and Folk (1970). The following were calculated

1. Maximum Projection Sphericity (MPS, Sneed and Folk 1958).

MPS={S2/LI} 1/ 3

2. Oblate Prolate Index (OPI, Dobkins and Folk 1970).

OPI= {(L-I / L-S) –0.5}/ (S/L)

3. Flatness Index (FI, Luttig. 1962)

FI = S/L x 100

Bivariate plots of MPS against OPI, and MPS against FI were also carried

out following the methods of Dobkins and Folk (1970), and Stratten (1974). The

computed form and roundness indices are shown in Table 4.1. below, bivariate

plots of flatness index against maximum projection sphericity (MPS), and MPS

41

against oblate-prolate index (OPI) are shown in Figs. 4.1 and 4.2 respectively,

while the sphericity form plots are presented in Fig. .

Table 4.1: Measured and Computed data from Pebbles collected

L S I I/L S/L S/I L-S L-I LI S2 LIS MPS FI OPI1 1.75 1.2 1.6 0.91 0.69 0.75 0.55 0.15 2.8 1.44 3.36 0.17 69 -0.332 1.52 1.72 1.15 0.76 1.13 1.5 -0.2 0.37 1.75 2.96 3.01 0.56 113 0.633 1.15 0.7 0.95 0.83 0.61 0.74 0.45 0.2 1.09 0.99 2.27 0.3 61 -0.094 1.92 1.5 1.72 0.9 0.78 0.87 0.42 0.2 3.3 2.25 4.95 0.2 78 -0.035 2 1.52 1.82 0.91 0.76 0.84 0.48 0.18 3.64 2.31 5.53 0.21 76 -0.166 1.8 1.15 1.78 0.99 0.64 0.65 0.65 0.02 3.28 1.32 3.68 0.13 64 -0.627 1.35 1.15 1.2 0.89 0.85 1.35 0.2 0.15 1.62 1.32 1.86 0.27 85 0.298 1.82 1 1.52 0.84 0.84 0.66 0.82 0.3 2.77 1 2.57 0.12 66 -0.169 2 1.2 1.75 0.88 0.6 0.69 0.8 0.25 3.5 1.44 4.2 0.14 69 -0.31

10 1.65 1.3 1.6 0.97 0.79 0.81 0.25 0.05 2.64 1.69 3.43 0.21 81 -0.3811 1.3 1.65 1.25 0.96 1.27 1.32 -0.3 0.05 1.63 2.72 2.68 0.56 125 -0.5512 1.72 1.3 1.62 0.93 0.76 0.8 0.42 0.1 2.79 1.69 3.62 0.2 76 -0.3413 1.8 1.65 1.7 0.94 0.92 0.97 0.15 0.1 3.06 2.72 5.05 0.29 92 0.1814 1.8 1.3 1.7 0.94 0.72 0.76 0.5 0.1 3.06 1.69 3.98 0.18 72 -0.4215 2.1 1.05 2 0.95 0.5 0.53 0.8 0.1 4.2 1.1 4.41 0.08 50 -0.7516 1.95 1.45 1.75 0.9 0.74 0.83 0.5 0.2 3.41 2.1 4.95 0.21 74 -0.1417 2.4 1.75 2.2 0.92 0.73 0.79 0.65 0.2 5.28 3.06 9.24 0.19 73 -0.2618 1.45 1 1.3 0.9 0.69 0.77 0.45 0.15 1.89 1 1.89 0.18 69 -0.2419 1.8 1.75 1.3 0.72 0.97 1.35 0.05 0.5 2.34 3.06 4.1 0.44 97 9.9720 1.95 1.6 1.6 0.82 0.82 1 0.35 0.35 3.12 2.56 4.99 0.82 82 0.6121 2.6 1.5 1.75 0.67 0.58 0.86 1.1 0.85 4.55 2.25 6.83 0.16 58 0.4722 1.45 1.15 2.3 1.58 0.79 0.5 0.3 0.15 3.34 1.32 3.84 0.13 79 023 1.6 1.25 1.3 0.83 0.78 0.96 0.35 0.3 2.08 1.56 2.6 0.25 78 0.4624 1.6 1.25 1.5 0.94 0.78 0.83 0.35 0.1 2.4 1.56 3 0.22 78 -0.2725 2.3 1.8 2.1 0.91 0.78 0.86 0.5 0.2 4.83 3.24 8.69 0.22 78 -0.1326 1.42 1.3 1.6 1.14 0.92 0.81 0.12 0.12 2.27 1.69 2.95 0.25 92 0.5427 2.45 2.15 2.35 0.96 0.88 0.91 0.3 0.15 5.76 4.62 10.41 0.27 88 028 1.7 1.35 1.4 0.82 0.79 0.96 0.4 0.3 2.38 1.82 3.21 0.25 79 0.2829 1.4 1.1 1.25 0.89 0.71 0.88 0.3 0.15 1.86 1.21 1.93 0.22 71 030 1.5 0.72 1.12 0.75 0.48 0.64 0.12 0.38 1.68 0.52 1.21 0.1 48 5.5631 1.7 1.6 1.5 0.76 0.94 1.07 0.1 0.2 2.55 2.56 4.08 0.33 94 1.6

42

4.2.2. Environmental Indications

Univariate pebble parameters: Several workers have demonstrated the usefulness

of pebble form indices in paleoenvironmental interpretation. Tables 4.2 shows

the critical values for form indices as established by previous workers for fluvial

and surf processes.

Table 4.2: Limits of form indices for fluvial and surf processes

Indices Fluvial Surf Reference

MPS More than 0.65 Less than 0.65 Dobkins and Folk (1970OPI More than –1.5 Less than –1.5 Dobkins & Folk (1970)FI More than 45% Less than 45% Stratten (1974)

Fluvial process is defined by MPS, OPI, and FI more than 0.65; -1.5; and

45% respectively, whereas surf process is defined by MPS, OPI, and FI less than

0.65; -1.5; and 45% respectively.

A critical analysis of Table 4.1 shows that within the Sandstone at

Lokpanta/Awgu Boundary, 100% of the flatness index values fall above the 45%

lower limit for fluvial process; these data thus suggest that the collected pebbles

from the pebble horizon at Lokpanta/Awgu Boundary, was largely shaped by surf

process.

The mean MPS value for pebbles sampled from the sandstone unit at

Lokpanta/Awgu Boundary is 0.25, the mean OPI is 0.49. The mean MPS and OPI

for pebbles from the Lokpanta/Awgu Boundary area suggest surf origin.

Bivariate plots: Discrimination of environments using bivariate plots of

pebble indices has been employed on ancient and recent gravel deposits with

43

much success (Luttig, 1962; Sames 1966; Dobkins and Folk, 1970; Stratten,

1974; Els, 1988; Obi, 1996). Plots of MPS vs. OPI and FI vs. MPS are

commonly used to discriminate fluvial and beach processes. Plots of MPS against

OPI (Figs. 4.1) indicate that all the pebbles sampled from the horizon at

Lokpanta/Awgu Boundary area reflect 54.84 % beach / surf action while 45.16%

reflects fluvial action. A plot of FI against OPI (Fig. 4.2) for pebbles sampled

from the same horizons at Lokpanta/Awgu Boundary area reflects 83.87% beach

action while 16.13% reflects fluvial action.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

-2 0 2 4 6 8 10 12

OPI

MP

S

SURF ACTION

FLUVIAL ACTION

Fig. 4.1: Plot of MPS against OPI for pebbles collected at Lokpanta/Awgu

Boundary Outcrop

44

0

20

40

60

80

100

120

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

MPS

FI

SURF ACTION

FLUVIAL ACTION

Fig. 4.2: Plot of OPI against FI for pebbles collected at Lokpanta/Awgu

Boundary Outcrop

Pebble form: Certain form classes (Sneed and Folk, 1958) are known to occur

more frequently in one environment than they do in another. For example the

three shape classes known to be most diagnostic of beach action are the Platy,

Very Platy, and Very Bladed, whereas forms most diagnostic of river action are

the Compact, Compact Bladed, and Compact Elongate (Dobkins and Folk, 1970).

Pebbles sampled at Lokpanta/Awgu Boundary unit belonging to Awgu Sandstone

show a remarkable transition from mainly Very Platy forms to Very Bladed form

and also from compact bladed to compact elongated.

45

4.3 Sieve Analysis

4.3.1 Methodology and Data Presentation

Fresh sandstone samples were obtained systematically collected from the

deformed sandstone unit at Lokpanta/Awgu Boundary [Awgu Sandstone (Five

samples from Station TOK/SST/01)], Ugwueme Area [Mamu Formation (three

Samples from Station TOK/SST/02)] and Awgu-Mmaku area [Awgu Sandstone

(Ten samples from Station TOK/SST/03)], the indurated sandstone samples were

carefully disaggregated in a mortar by a rubber padded pestle while the friable

ones needed no disaggregating. The sandstone samples were then dried.

About 100 grams of each disaggregated sample was divided into equal

parts by using the prescribed Jones sample splitter to avoid any biases in terms of

grain distribution. 50 gram of each sample was sieved for 15minutes on a Ro–Tap

sieve shaker using a set of U.S standard sieves at ¼ phi sieve internal to provide

maximum accuracy of results as was suggested by Folk (1974). Each sieve

fraction was weighed to a precision of 0.01 gram. The data obtained is as

presented in table 4.3 below. The data is also represented as histogram (as shown

in Fig. 4.3 below), plotted on the arithmetic scale, to obtain the modal class size

for each sample as well as cumulative frequency curves plotted on the log-

probability scale as shown in Fig. 4.4 below. The scale is derived by dividing the

area beneath a normal distribution curve into columnar segment of equal area.

46

Those near the center of the distribution are long and relatively narrow where as

those towards the tails are low and proportionally broader. From the cumulative

plots, values intercepted from the percentile were read off and used to compute

the statistical parameters. The parameters which include Graphic Mean (Mz),

Sorting Coefficient (1) Skewness (Ski) and Kurtosis (Kg), computed using

formulas which were adopted from Folk and Wards (1957) as defined below.

Formulas for computation of statistical parameters of sieve analysis.

Mz= 1/3 (16 + 50 + 84)

1 = 84 – 16 + 95 – 5

4 6.6

SKi = 16 + 84 – 2 50 + 5 + 95 – 2 50

2(84 –16) 2(95-5)

Kg = 95 - 5 . 2.44 (75-25)

47

Table 4.3a: Summary of Sieve Data and AnalysisStation: TOK/SST/01 (Lokpanta - Awgu Lokpanta Awgu Boundary - LAB)

Unit LAB I Unit LAB II Unit LAB III Unit LAB IV Unit LAB V

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

-2 0 0 0 0 0.00 0.00 0 0.00 0 0 0.00 0.00 0.1 0.20 0.20

-1 0.9 1.84 1.84 2.3 4.63 4.63 1.5 1.84 1.84 4.2 8.57 8.57 5.5 11.04 11.24

0 3.6 7.38 9.22 1.6 3.23 7.87 3.5 7.38 9.22 7.2 14.69 23.26 15.8 31.73 42.97

1 9.7 17.83 27.05 2.7 5.44 13.31 5.6 17.83 27.05 8.3 16.94 40.20 16.9 33.94 76.91

2 23.8 48.77 75.82 29.07 59.88 73.19 18.5 48.77 75.82 14.3 29.18 69.38 8.6 17.27 94.18

3 11.1 22.25 98.82 12 24.19 97.38 19.8 22.75 98.57 13.5 27.55 96.93 2.5 5.02 99.2

4 0.7 1.43 100 1.3 2.62 100 0.8 1.43 100 1.5 3.06 99.98 0.4 0.80 100

Station: TOK/SST/02 (Ugwueme Area - UA)

Unit UA I Unit UA II Unit UA III

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

-2 0.3 0.60 0.60 0 0.20 0.20 0 0.00 0.00

-1 2.3 4.62 5.22 1.5 3.01 3.21 0.2 0.40 0.40

0 6.9 13.86 19.08 4.6 9.24 12.45 0.7 1.41 1.81

1 14.1 28.31 47.39 10.6 21.29 33.74 2.9 5.84 7.65

2 21.4 42.97 90.36 19.5 39.16 73.90 13.5 27.16 34.81

3 4.4 8.84 99.20 12.6 25.30 98.20 28 56.34 91.15

4 0.4 0.80 100 0.9 1.81 100 3.9 8.85 100

48

Table 4.3b: Summary of Sieve Data and AnalysisStation TOK/SST/03 (Awgu-Mmaku –AM)

Unit AM I Unit AM II Unit AM III Unit AM IV Unit AM V

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

-2 1.2 2.42 2.42 0.4 0.80 0.80 0.5 0.10 0.10 0.3 0.6 0.6 0 0 0

-1 4.6 9.29 11.71 5.53 11.07 11.87 3.2 6.39 6.49 4.9 9.82 10.42 5.1 10.2 10.2

0 9.4 18.99 30.7 18.82 37.63 49.50 12.5 25.13 31.62 3.9 7.82 18.24 19.2 38.4 48.6

1 16.6 33.54 64.24 17.31 34.61 84.11 10.4 20.80 52.42 18.6 37.27 55.51 21.5 43 91.6

2 16.0 32.32 96.56 7.15 14.29 98.4 16.3 34.60 87.02 15.6 31.26 86.77 3.5 7 98.6

3 1.5 3.02 99.59 0.72 1.41 99.81 6.07 12.15 99.17 6.5 13.03 99.8 0.4 0.8 99.4

4 0.2 0.40 99.99 0.1 0.20 100. 0.41 0.82 99.99 0.1 0.2 100 0.3 0.6 100

Pa

n

Unit AM VI Unit AM VII Unit AM VIII Unit AM IX Unit AM X

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

Wt

(g)

%

Freq

Cum.

%

-2 0 0.00 0.00 0 0.00 0.00 0.3 0.60 0.60 0 0.00 0.0 0.2 0.20 0.20

-1 5.9 11.8 11.8 2.2 4.4 4.4 3.8 7.62 8.22 1.2 2.41 2.41 4.9 9.82 10.02

0 4.2 8.4 20.2 3.7 7.4 11.8 21.3 42.69 50.91 3.3 6.63 9.04 20.2 40.48 50.50

1 16.5 33.0 53.2 5.9 11.8 23.6 18.5 37.07 87.98 16.2 32.53 41.57 20.5 4108 91.58

2 17.5 35.0 88.2 14.3 28.6 52.2 5.6 11.22 99.2 2 40.16 81.73 3.4 6.81 98.39

3 5.5 11.0 99.2 20.5 41.0 93.2 0.3 0.60 99.8 7.3 14.66 96.39 0.5 1.00 99.39

4 0.4 0.8 100 3.4 6.8 100 0.1 0.20 100 1.8 3.6 99.99 0.3 0.60 99.99

Pa

n

49

Fig. 4.3a: Plot Representation of Sieve Analysis for Obtaining Modal Class Size

0

5

10

15

20

25

30

35

40

45

50

-2 -1 0 1 2 3 4

Phi ()

Unit LAB I

Percentage Weight ( % g)

0

10

20

30

40

50

60

-2 -1 0 1 2 3 4

Phi ()

Unit LAB II


Phi ()


0

5

10

15

20

25

30

35

40

-2 -1 0 1 2 3 4

Unit LAB III

Phi ()

0

5

10

15

20

25

30

-2 -1 0 1 2 3 4

Unit LAB IV


0

5

10

15

20

25

30

35

-2 -1 0 1 2 3 4

Unit LAB V

Phi ()


0

5

10

15

20

25

30

35

40

45

-2 -1 0 1 2 3 4

Unit UA I

Phi ()


0

5

10

15

20

25

30

35

40

-2 -1 0 1 2 3 4 Pan

Unit UA II

Phi ()


0

10

20

30

40

50

60

-2 -1 0 1 2 3 4 Pan

Unit UA III

Phi ()


Station: TOK/SST/02 (Ugwueme Area - UA)

Station: TOK/SST/01 (-Lokpanta -Awgu Boundary LAB)

50

0

5

10

15

20

25

30

35

-2 -1 0 1 2 3

0

5

10

15

20

25

30

35

40

-2 -1 0 1 2 3 4

0

100

200

300

400

500

600

700

-2 -1 0 1 2 3 4

Station TOK/SST/03 (Awgu-Mmaku -AM)

Unit AM I

Phi ()

Per

cent

age

Wei

ght

( %

g)

Phi ()

Per

cent

age

Wei

ght

( %

g)

Phi ()

Per

cent

age

Wei

ght

( %

g)

Unit AM II

Unit AM III

0

5

10

15

20

25

30

35

40

-2 -1 0 1 2 3 4 Pan

Unit AM IV

Phi ()

Per

cent

age

Wei

ght

( %

g)

0

5

10

15

20

25

30

35

40

45

-2 -1 0 1 2 3 4 Pan

Unit AM V

Phi ()

Per

cent

age

Wei

ght

( %

g)

Phi ()

Per

cent

age

Wei

ght

( %

g)

0

5

10

15

20

25

30

35

-2 -1 0 1 2 3 4

Unit AM VI

0

5

10

15

20

25

30

35

-2 -1 0 1 2 3

0

5

10

15

20

25

30

35

40

-2 -1 0 1 2 3 4

0

5

10

15

20

25

30

35

40

-2 -1 0 1 2 3 4

0

100

200

300

400

500

600

700

-2 -1 0 1 2 3 4

0

100

200

300

400

500

600

700

-2 -1 0 1 2 3 4

Station TOK/SST/03 (Awgu-Mmaku -AM)

Unit AM I

Phi ()

Per

cent

age

Wei

ght

( %

g)

Phi ()

Per

cent

age

Wei

ght

( %

g)

Phi ()

Per

cent

age

Wei

ght

( %

g)

Unit AM II

Unit AM III

0

5

10

15

20

25

30

35

40

-2 -1 0 1 2 3 4 Pan

Unit AM IV

Phi ()

Per

cent

age

Wei

ght

( %

g)

0

5

10

15

20

25

30

35

40

-2 -1 0 1 2 3 4 Pan

0

5

10

15

20

25

30

35

40

-2 -1 0 1 2 3 4 Pan

Unit AM IV

Phi ()

Per

cent

age

Wei

ght

( %

g)

0

5

10

15

20

25

30

35

40

45

-2 -1 0 1 2 3 4 Pan

Unit AM V

Phi ()

Per

cent

age

Wei

ght

( %

g)

0

5

10

15

20

25

30

35

40

45

-2 -1 0 1 2 3 4 Pan

0

5

10

15

20

25

30

35

40

45

-2 -1 0 1 2 3 4 Pan

Unit AM V

Phi ()

Per

cent

age

Wei

ght

( %

g)

Phi ()

Per

cent

age

Wei

ght

( %

g)

0

5

10

15

20

25

30

35

-2 -1 0 1 2 3 4

Unit AM VI

Phi ()

Per

cent

age

Wei

ght

( %

g)

0

5

10

15

20

25

30

35

-2 -1 0 1 2 3 4

0

5

10

15

20

25

30

35

-2 -1 0 1 2 3 4

Unit AM VI

Fig. 4.3b: Plot Representation of Sieve Analysis for Obtaining Modal Class Size

51

Fig. 4.3c: Plot Representation of Sieve Analysis for Obtaining Modal Class Size

4.4 Analysis and Results of Sieve Data

The computed statistical parameters for textural analysis from sieve data

are presented in Table 4.5 and the data used for the computation is below in table

4.4. Representative histograms of the grain–size distribution are shown in Fig

4.3a, 4.3b and 4.3c above and the probability curves are presented below in Fig.

4.4. The statistical parameters are; Mean size (Mz): Sorting (1), Skewness

(SKi,) and Kurtosis (KG).

0

5

10

15

20

25

30

35

40

45

-2

-1

0 1 2 3 4

Unit AM VII

Phi ()


0

5

10

15

20

25

30

35

40

45

-2

-1

0 1 2 3 4

Unit AM VIII

Phi ()


0

5

10

15

20

25

30

35

40

45

-2

-1

0 1 2 3 4

Unit AM IX

Phi ()


Phi ()


0

5

10

15

20

25

30

35

40

45

-2

-1

0 1 2 3 4

Unit AM VII

Station TOK/SST/03 (Awgu-Mmaku -AM) Continues

52

Sample No.: TOK/SST/01 [Lokpanta Awgu Boundary (LAB)]

LAB ILAB II

(Phi – Scale)

LAB III LAB IV (Phi – Scale)

Fig. 4.4 Log Probability Curves for Samples

53

Sample No.: TOK/SST/01 [Lokpanta Awgu Boundary (LAB)]

LAB VUA I

(Phi – Scale)

UAII UA III

Sample No.: TOK/SST/02 [Ugwueme Area (UA)]

(Phi – Scale)

54

Sample No.: TOK/SST/03 [Awgu Mmaku (AM)]

AM IAM II

(Phi – Scale)

AM III AM IV (Phi – Scale)

55


AM VAM VI

(Phi – Scale)

AM VII AM VIII (Phi – Scale)

56

4.4.1 Textural Parameters

Mean Size (Mz):

The mean size reflects the overall competency of the transport system.

The mean diameter is the size at which 50% of the particles (by weight) are

medium and the remainder finer. Samples obtained from the Station

TOK/SST/01, show moderately stable current from the base and slight variation

at the top (LAB V) with high current for depositing the coarse sand. Station

TOK/SST/02 shows moderate current for the three samples at this station. Station

TOK/SST/03 show that the depositing medium had high current responsible for

deposing coarse sand and slightly varied in the cause of depositing towards the

top of the section detail of analysis is presented in table 4.5 below after table 4.4.


AM IXAM X

(Phi – Scale)

57

Table 4.4: Data from Log Probability Curves for Statistical Computation

Sample Station: TOK/SST/01 (Lokpanta - Awgu Lokpanta Awgu Boundary - LAB)

5 16 25 50 75 84 95

LAB I -0.40 0.40 0.80 1.40 1.80 2.30 3.50LAB II -0.60 1.00 1.20 1.60 2.10 2.30 2.80LAB III -0.40 0.40 1.10 1.70 2.40 2.80 3.40LAB IV -1.20 -0.60 0.00 1.00 2.00 2.50 3.40LAB V -1.30 -0.70 -0.50 0.20 0.90 1.20 2.30Sample Station: TOK/SST/02 (Ugwueme Area - UA)UA I -080 -0.10 0.30 1.00 1.60 1.90 2.60UA II -0.40 0.20 0.00 0.60 1.30 2.10 2.80UA III 0.80 1.30 1.50 2.20 2.80 3.00 3.60Sample Station TOK/SST/03 (Awgu-Mmaku –AM)AM I -1.40 -0.80 -0.40 0.40 1.20 1.70 2.40AM II -1.30 -0.90 -0.60 0.00 0.70 1.00 2.20AMIII -1.20 -0.60 -0.20 0.60 1.40 1.80 3.00AM IV -0.80 -0.20 0.20 0.80 1.60 2.00 3.00AM V -1.20 -1.00 -0.60 -0.40 0.40 0.60 1.80AM VI -0.80 -0.20 0.50 0.80 1.60 1.80 2.60AMVII -0.70 0.40 1.0 1.70 2.40 2.80 3.40AM VIII -1.20 -0.80 -0.60 0.00 0.60 0.80 2.10AM IX -0.40 0.20 0.50 1.20 1.80 2.10 2.80AM X -1.20 -0.80 -0.50 -0.20 0.40 0.60 1.80

Coefficient of Sorting ()

This parameter is a measure of the spread of size about the average and it

defines the dispersion of sediment. Samples from units at station TOK/SST/01

shows moderate sorting from base to top, station TOK/SST/02 shows all samples

to be moderately sorted, and same for station TOK/SST/03. (See Table 4.5)

Skewness (Ski)

Skewness is a measure of the asymmetry of a frequency distribution. If

negative, it is coarse and fine if positive. Stations TOK/SST/01, TOK/SST/02

and TOK/SST/03 showed samples to be fine from the base of the units and

through the entire unit and its indicated as positively skewed.

58

Kurtosis ( KG)

Kurtosis in a measure of the peakedness of a curve from normal (Tucker

1982). In effect, it measures the degree of sorting in the center of the curve

compared to sorting at the tails. Fluctuation in kurtosis between “leptokurtic” and

“platykurtic” were observed in samples from station TOK/SST/01 and

TOK/SST/02 had all its samples to be platykurtic. Station TOK/SST/03 showed

dominant platykurtic and varied in the middle showing mesokurtic. This means

that their curves are moderately peaked and sometimes strongly peaked. Kurtosis

is an indirect measure of sorting that flat curves of poorly sorted sediments are

platykurtic while strongly peaked curves of good sorting are leptokurtic.

However, it should be noted that kurtosis is not a diagnostic parameter in

predicting depositional process (Blatt et-at 1972).

4.4.2 Environmental Indication:

The textural parameters namely: Mean Size (Mz), Sorting, (), Skewness

(Ski), and kurtosis (KG) are used as environmental indicators. The technique

involves using the unvaried textual parameters, beverage plots of such textural

parameters and multivariate statistical functions to predict possible environment

of deposition of the various units at the stations.

4.4.2.1Univariate Textural Parameters

Mean Size, Mz

The sandstones of Awgu Sandstone are dominantly medium-grained and

coarse-grained fractions (Table 4.5.) Suggesting a relatively high-energy

condition at the time of deposition of the sediments. Occasional increase

in hydraulic energy may be associated with the deposition of the coarse-grained

fractions. The fining-upward motif at the muddle internal is attributed to fluvial

59

processes and may probably be the result of lateral migration of fluvial channels

(Pettijohn 1975, p 628). This observed abrupt variation in mean size from

medium to coarse may be related to rapid changes in hydraulic energy commonly

associated with tidal processes This interpretation is supported by the presence of

variation of sand sizes (from medium to coarse) at the observed stations.

Coefficient of Sorting or Standard Deviation (,)

Sorting indicates function in the velocity of the depositing agent. The

sandstone units at stations TOK/SST/ 01, TOK/SST/02 AND TOK/SST/03 do not

show uniform sorting. Fluctuations from moderately well sorted to only one

sample from station TOK/SST/01 being poorly sorted sand, can be attributed to

difference in water turbulence and variability in current velocity. Sorting reflects

relatively stable current velocity (for moderately sorted) and minute turbulence

(poorly sorted) during deposition typical of tidally influenced action for moderate

sorting and fluvial action for poor sorting. Cant (1982) related moderately sorted

to poorly sorted sandstone with dominant polymodal distribution to tidally

influenced fluvial channel. The symmetrical to asymmetrical shaped of

histograms (Fig. 4.3a, 4.3b and 4.3c above) of frequency distribution for

sandstone of the units at stations TOK/SST/01, TOK/SST/002 and TOK/SST/03

along with the generally moderate to poor sorting suggests tidally influenced

fluvial setting.

Skewness (SKi)

Trend in the Skewness are also significant of sandstone deposition

medium which shows Skewness / medium fluctuation between dominantly

negatively or coarsely skewed, finely or negatively skewed and symmetrical

fractions. The coarsely skewed or positively skewed fractions implies that the

velocity of the depositing agent operated at a higher velocity than the average

60

velocity for a greater length of time than normal and / or the velocities occur more

often than normal. The subordinate finely skewed or negatively skewed fractions

indicated that the velocity of the depositing agent operated at a lower velocity

than the average velocity for a greater length of time than normal. Near

symmetrical Skewness indicates that a broad spectrum of population is present in

the sample. It indicates that occasional stability in the velocity conditions of the

depositing agent, (see detail of studied area as presented in table 4.5a and 4.3b

below).

Table 4.5a: Summary of Results of Statistical Parameters Obtained From Grain Size Analysis with their Verbal Interpretation

Sample No

TOK/SST/01 – Lokpanta – Awgu Boundary (LAB)

Mean Size (Mz) Sorting (1) Kurtosis (KG) Skewness (SKi)

LAB I 1.77 Medium Sand

1.18Moderately Sorted

1.11Leptokurtic

0.27Pos. Skewed

LAB II 1.80Medium Sand


1.32 Leptokurtic

0.18Pos. Skewed

LAB III 1.83Medium Sand


1.01Mesokurtic

0.18Pos. Skewed

LAB IV 1.27Medium Sand

1.56Poorly Sorted

0.76Platykurtic

0.14Pos. Skewed

LAB V 0.6Coarse Sand


0.73Platykurtic

0.14Pos. Skewed

TOK/SST/02 – Ugwueme Area (UA)

UA I 1.17Medium Sand


0.85Platykurtic

0.11Pos. Skewed

UA II 1.20Medium Sand


0.79Platykurtic

0.57Pos Skewed

UA III 2.37Medium Sand


0.69Platykurtic

0.47Pos. Skewed

61

Table 4.5b: Summary of Results of Statistical Parameters Obtained From Grain Size Analysis with their Verbal Interpretation

TOK/SST/03 – Awgu Mmaku (AM)

AM I 0.67Coarse Sand


0.79Platykurtic

0.11Pos. Skewed

AM II 0.43Coarse Sand


0.73Platykurtic

0.14Pos. Skewed

AM III 1.00Medium Sand


0.77Platykurtic

0.17Pos. Skewed

AM IV 1.20Medium Sand


0.82Mesokurtic

0.26Pos. Skewed

AM V 0.13Coarse Sand


0.74Platykurtic

0.23Pos. Skewed

AM VI 1.07Medium Sand


0.51V. Platykurtic

0.18Pos. Skewed

AM VII 1.83Medium Sand


1.02Mesokurtic

0.12Pos. Skewed

AM VIII 0.43Coarse Sand


0.68Platykurtic

0.12Pos. Skewed

AM IX 1.40Medium Sand


0.79Platykurtic

0.22Pos. Skewed

AM X 0.27Coarse Sand


0.82Platykurtic

0.16Pos. Skewed

Kurtosis (KG)

Kurtosis is an in an indirect measure of sorting, flat curves of poorly

sorted sediments are platykurtic while strongly peaked curves of good sorting are

leptokurtic. It should be noted that kurtosis is not a diagnostic parameter in

predicting depositional process (Blatt, et al, 1972).

Log Probability Plots: Presented above as fig. 4.4 for the entire stations, has

been suggested that these cumulative frequency curves on log-probability scale

could be subdivided into two, three, or four linear segments representing the

62

traction, saltation, and suspension modes of sediment transport (Visher, 1974).

The number, amount and degree of mixing, size range, and sorting of these

subpopulations vary systematically in relation to provenance, sedimentary

processes, and dynamics. Visher (1974) investigated these characteristics and

reproduced several curve patterns, each reflecting various sedimentary processes

(e.g. current, wave, tide, channel, etc. Log -probability plots of sands of the

present study area, were analyzed for environmental indications following the

method of Visher (1969). Plots for samples from the Awgu Sandstone at labeled

Stations TOK/SST/01, TOK/SST/03 and Mamu Formation label TOK/SST/02

representing LAB, AM and UA respectively show the following general

characteristics:

a small poorly-to-fairly well sorted traction load;

a saltation subpopulation that ranges from -1 phi to 1 phi, with the saltation-

suspension junction occurring at between 2 phi and 3.0phi.

These characteristics are very similar to the characteristics of curves obtained for

sandstone samples from the Almond and Lance Formation which Weimer (1965)

interpreted as being of deltaic origin. The characteristics are believed to be

produced by strong tidal currents in areas where the surface creep population has

been removed probably in shallow water, or on bars in the tidal channel.

4.4.2.2 Bivarate Analysis

Information pertaining the processes and environments of sand deposition

can be extracted from grain size data and have been demonstrated by several

workers such as Mason and Folk, 1958, Friedman, 1967, and Cant, 1982.

63

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

LAB

UA

AM

Beach

Fluvial

Fig. 4.5a. : Bivarate Plot of Ski Vs 1 for Samples

Bivariate plots of textural parameters (sk1 Vs1) could also be used to delineate

adjacent environments. A plot of Skewness (Sk1) against standard deviation (1)

for samples collected from station labeled Stations TOK/SST/01, TOK/SST/02

and TOK/SST/03 representing LAB, UA and AM respectively (Fig. 4.5) indicates

a dominant fluvial process. Also, plot of mean size (MZ) against standard

deviation (1) used for interpreting depositional environment for the analyzed

sand; (fig 4.5b) classifies the sand units as almost 100% fluvial deposit.

1

SK

i

64

0

0.5

1

1.5

2

2.5

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

Mz

LAB

UA

AM

Surf Process

Fluvial Action

1

Fig. 4.5b. : Bivarate Plot of Mz Vs 1 for Samples

4.4.2.3 Multivariate Analysis

Statistical methods to discriminate between adjacent environments having

closely similar energy conditions as presented by Sahu (1964) is the basis of this

method of analysis. He proposed some discriminate functions among which three

(3) would be used in this study being found relevant. He discriminated between

shallow marine and beach, shallow turbidity currents based on a defined function

(Yu.).

In the first case, he established

Yu for Beach: shallow marine

Yu = 15.6534 Mz + 65.7091 + 18.1071Sk1,+18.5043KG and proposed that Yu<

65.3650 indicates beach environment while Yu > 653650 indicates shallow marine

environment.

65

In the second case, the established

Yu for shallow marine: fluvial (deltaic)

Yu = 0.2852 M2 – 8.7604 - 4.8932Sk1+0.0482KG and proposed that Yu < -

7.4190 indicate a fluvial environment, while Yu > -7.4190 indicates shallow

marine environment.

In the third case, we established

Yu for fluvial: Turbidity currents

Yu = 0.7215M2 – 0.40301 + 6.7322Sk1 + 5.2927KG

And proposed that Yu < 9.8433 indicates turbidity current deposition while Yu >

9.8433 indicate fluvial (deltaic) deposition.

Results obtained using these multivariate relationships are shown on Table

4.6. From the tables, it is evident that all samples of station TOK/SST/O1 and

TOK/SST/03 of Awgu sandstone and Station TOK/SST/03 of Mamu Formation

were dominantly deposited in a shallow marine environment, using the first

relationship. Using the second relationship, samples deviated, indicating fluvial

environment of deposition. And, upon using the third relationship, the fluvial

deposits of the samples become indicative of turbidity current deposition.

66

Table 4.6: Summary of Environment from Multivariate Discriminate Functions Sample no

Beach Shallow Marine Shallow Marine: Fluvial

Fluvial :Turbidity Current

VALUE VERBAL TEARM

VALUE Verbal term Value Verbal Term

LAB I 144.63 Shallow Marine -12.96 Fluvial 8.49 Turbidity CurrentLAB II 107.91 Shallow Marine -7.24 Fluvial 9.12 Turbidity CurrentLAB III 150.01 Shallow Marine -13.56 Fluvial 7.38 Turbidity CurrentLAB IV 196.39 Shallow Marine -21.61 Fluvial 5.25 Turbidity CurrentLAB V 109.34 Shallow Marine -11.66 Fluvial 5.63 Turbidity Current

UA I 112.68 Shallow Marine -10.38 Fluvial 5.60 Turbidity CurrentUA II 113.43 Shallow Marine -11.70 Fluvial 8.47 Turbidity CurrentUA III 112.79 Shallow Marine -8.85 Fluvial 8.16 Turbidity Current

AM I 133.08 Shallow Marine -14.44 Fluvial 4.89 Turbidity CurrentAM II 105.20 Shallow Marine -11.52 Fluvial 4.67 Turbidity CurrentAM III 152.73 Shallow Marine -16.48 Fluvial 5.40 Turbidity CurrentAM IV 136.47 Shallow Marine -13.93 Fluvial 6.46 Turbidity CurrentAM V 81.72 Shallow Marine -9.30 Fluvial 5.59 Turbidity CurrentAM VI 107.51 Shallow Marine -10.96 Fluvial 5.46 Turbidity CurrentAM VII 157.35 Shallow Marine -14.37 Fluvial 7.01 Turbidity CurrentAM VIII 91.35 Shallow Marine -9.73 Fluvial 4.30 Turbidity CurrentAM IX 110.23 Shallow Marine -9.93 Fluvial 6.25 Turbidity CurrentAM X 77.9 Shallow Marine -8.08 Fluvial 5.24 Turbidity Current

67

CHAPTER FIVE

INTERPRETATION AND DISCUSSION OF RESULTS

5.1 Introduction

The study area is interpreted using the analyzed data presented in chapter

four. Samples collected and analyzed though representative of the area is used to

infer the depositional environment of the sediments in the area, structural

interpretation based on hypothetical analysis carried out in the study areas, with

concluding section on the economic importance of the study area.

5.2 Depositional Environment

Using the pebble analysis, though samples are small in number, the

pebbles of Lokpanta/Awgu boundary (belonging to Awgu Shale) shows a fluvial

environment of deposition shaped largely by surf processes.

Sandstone analysis carried out in the study area, samples preventative of

Awgu Sandstone and Mamu formation is used to infer this environment of

deposition. The analysis point to the fact that the samples were deposited in

fluvial environment with active turbulent current acting on the samples, while

their cumulative plots was indicative of deltaic origin.

5.3 Discussion of Shale Result

Samples collected from station 2, 7, 8, and 10 (TOK/SH/01, TOK/SH/02,

TOK/SH/03, and TOK/SH/04) belonging to Eze-Aku Shale; Station 18

(TOK/SH/05) belonging to Asata Nkporo Shale; and seeped oil collected at

Station 12 (TOK/OSM/01), were analyzed using methods of pyrolysis and liquid

chromatography. The result is presented in Table 5.1 below.

68

Table 5.1: Composition of Extracted and Fluid Samples from the Study Area.

Map

No.

Sample Code

and Location

Sample

Type

TOC

(wt%)

SOM

Ppm

SHC

%

AHC

%

NSO

%

2 TOK/SH/01 Shale 2.50 4670 1.25 10.7 88.1

7 TOK/SH/02 Shale 4.06 13069 309 19.0 50.1

8 TOK/SH/03 Shale 2.40 771 12.8 7.6 80.7

10 TOK/SH/04 Shale 4.27 4137 31.5 3.4 65.1

18 TOK/SH/05 Shale 2.27 3642 21.9 7.3 70.8

18 TOK/SH/05 Shale 2.10 1355 14.5 5.2 80.3

12 TOK/OSM/01 Seeped oil - - 0.69 1.05 98.2

TOC - Total Organic Content; SOM – Soluble Oganic Matter AHC – Aromatic Hydrocarbon; SHC Saturated HydrocarbonNSO – Nitrogen, Sulfur and Oxygen

Table 5.1 shows that Map No. 2, 7, 8, 10 belong to Eza-Aku Shale, Map. No. 18

belongs to Asata Nkoro Shale and Map. No. 12 belonging to Mamu Formation

(See Table 3.1 and enlarged map).

The analyzed samples show relatively high sulfur, nitrogen and oxygen

content and the saturate show low percentage of viscosity and porosity of the

materials, which suggest low asphatene precipitation which in turn will affect the

two mentioned factors of the material mentioned above.

High resin content (SOM) show intensive biodegradation of the materials

involved, which is common in the very near surface.

From energy point of view, it is considered that if the average organic

content and a sample is less than 2.5% per weight, more energy is required for

processing than is produced. Also studies by a number of authors indicate 1.5-2%

per wt for TOC and were adequate for the rock to be an oil source rock. Tissot

and Walte (1978) used 0.5%wt of TOC for clastic and 0.3%wt for carbonate

69

sediments to be oil source rock. Table 5.2 present TOC classification for source

rocks.

Table 5.2: TOC Classifications for Source Rock Material

TOC (%wt) Interpretation

0-0.5 Poor

0.5-1.0 Fair

1.0-2.0 Good

2.0-4.0 Very Good

>4.0 Excellent

Thus Table 5.2 shows that the samples are good to excellent source rock material

It should be noted that not all organic carbon in sedimentary rocks is converted to

hydrocarbon and actually, TOC may reach 20% or more by weight. These high

values are mainly seen in coal and rich oil shale (which are not source sediment

for potential reservoir).

The oil potential associated with these shale deposit within Anambra basin

in the study area can be measured in hundred of billion assuming it will

sometimes be of economic importance to mine and process or process in-situ,

although in some area, the shale (s) have been buried to considerable depth,

which in-order words can be considered to be source rock for neighboring oil

fields.

5.4 Tectonic / Structural Attributes in the Study Area

Sedimentary and tectonic structures general characterize the study area.

Plates 3.8, 3.15, 3.10, and 3.16 in chapter three, shows these features, including

that of biogenic activities. For shale, it shows that the environment of deposition

must have been affected by low to very quiet environment, giving rise to the thick

70

accumulation of the organic sediments in the area. But the presence of dolerite

intrusion within this material could infer that that organic matter may have been

destroyed, due to high temperature of the dolerite thereby destroying the organic

matter that are to yield hydrocarbon or that the hydrocarbon being vaporized doe

to its presence, since organic matter ordinarily will not thrive in such an

environment.

Different varieties of soft sediment deformation structures have been

observed in southern Anambra basin. The structures include angular discordance

in the form of folds (Plate 3.12), faults and ball and pillow structure. (Obi, 2000).

Evidence of tectonic activities in the study area (Plate 3.10), could as well

have created subsurface structures capable of trapping hydrocarbons post the

tectonic activity, but since crude are seen in the surface as oil seep and gas smell,

the structures in place prior to migration of the fluid to the reservoir (Mamu

Formation) could have been destroyed by the Santonian uplift in the area. This

statement of fact should further be investigated by used of subsurface exploration

techniques for fault patterns in the area so as to understand the depth and nature

of tectonics activity in the study area.

Mudrock and fine grained sandstone of Eze-Aku Shale as observed at

Crush Stone Industrial Site shows deformation structure that are readily

observable from side view sections Plate 3.11 and appear in the form of intra

formational angular unconformity and deformed strata.

5.5 Economic Importance of the Study Area

The study area is endowed with abundance of economic prospects, some

of which are not yet developed. This probably may be due to lack of good road

networks as a result of low funding for such projects

71

Road Construction and Building Material

The Agbani, Awgu and parts or Mamu materials in the area particularly in

Ogo-Mmaku, Ugwueme, Lekwesi and their respective environs contains a thick

sequence of extensive sandstone found to be quartz rich The sand though in

some areas it is being quarried recently, it can further be quarried as glass sand for

glass industry and is also suitable for concrete mixing used for bridges and other

civil engineering construction purposes.

Clay (Mud) and Shale

Shales in the area have high drying and frying shrinkage. The shale when

mixed with clays that have low drying and firing shrinkage can be used for the

manufacture of vitrified bodies such as paving bricks, roof tiles and sewage pipes

(Ogbukagu, 1979).

The clay within the area has a whitish to dull colour. Most of the clays of

the Awgu Ndeaboh unit is very plastic in nature and could be used for the

manufacture of refractory substances. The clays when fired to very high

temperature and treated chemically could be used in the manufacture of china

waves, building bricks, earthen- ware, conduits and foundry, septic tanks and

tiles.

Agriculturally, clay, shale, sandy clay, sandy shale and sandstone of the

Agbani Sandstone and Awgu sandstone form abundant productive fertile

farmland around Mmaku Area (Appendix I) on the plains to the east (Grove,

72

1951). Those living on the uplands often have farms some mile further east, and

are largely dependent on the cassava, yam and other crops produced in the area.

Dolerite is also presently being quarried in the area, which can be used for

edifying houses, construction of roads etc., both by local contractors around

Lokpaukwu areas and cooperate body around Lekwesi area.

Hydrogeology

Drainage pattern presented in chapter two suggests abundance of surface

water in study area. Though chemical analysis of these water is not carried out, so

as to obtain its suitability for domestic purposes, but form informal sources owing

to interview carried around the environs, indigenes responded that though the salt

water (Obilagu Salt water) is perennial, it is still of economic importance to them

since it immediately alleviate their salt needs. (Appendix II).

Hard Water was also encountered in the study area around Ogo Mmaku

environs. (Appendix III). The Ogbanugwu water fall (Appendix IV) was also

encountered in the area around Ogo-Mmaku area. This water fall have an average

falling kinetic energy to be greater than 140-160 m/s. if this is developed to be up

to >200m/s, it could be used to power a mini hydro power substation that could

alleviate electricity problem within it immediate vicinity.

73

CHAPTER SIX

SUMMARY AND CONCLUSION

5.1 Summary and Conclusion

The study area, underlain by three lithologic units; medium-coarse grains

sandstone, mud rock and shale, have a general trend of NE-SW and average dip

direction with unconformity or deformation affecting some parts. The unit

(TOK/SST/01, 03, 04, and 05) belonging to Awgu Sandstone and the unit

(TOK/SST/020) belonging to Mamu Formation [all cretaceous Campanian-

Maastrichtian sediments]; Shale (TOK/SH/03 and 10) belonging to Eze-Aku

Shale [Turonian–Coniacian sediment]; and Mottled clay rock (TOK/MCL/01)

belonging to Awgu Ndeaboh Shale [Santonian Sediment].

Pebble and Sieve analysis of the medium to coarse grained sandstone

units of Awgu Sandstone and Mamu Formation suggest a tidally influenced

fluvial environment though of deltaic origin and the shale of Eze-Aku and

Ndeaboh Nkporo deposited in range of environments ranging from shoreface to

shallow marine environment for the Eze-Aku shale and swamp environment for

Ndeaboh Nkporo Shale.

Tectonic activity that affected the area could be responsible for the

presence of deformation as observed in the area eventually resulting to surface

exposure of hydrocarbon around Ugwueme area, thereby destroying any possible

trap mechanism for any of such hydrocarbon accumulation.

74

APPENDIXES

Appendix I: Abundant Vegetation land use for agricultural purpose in the Study Area

Appendix II: (A) Flow out point of the Salt Water (Obilagu Salt water) and (B) kegs used in collecting these water for local preparation of food at Lokpanta

A B

75

Appendix III: Flow out point of the Hard Water at Lokpanta

Appendix IV: Ogbanugwu water fall, which could be used to power a sub hydro power generating station if developed. At Ogo-Mmaku

76

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research project

Documents

awgu area

ugwueme area

lekwesi area

lokpaukwu area

mmaku area

awgummaku study area

lokpaukwulekwesi study

shale of eze