GEOLOGY OF NNEWI AND ITS ENVIRONS

ABSTRACT
The study area covers latitudes 06000’N to 06007’N and longitudes 006045’E to 006059’E and underlain by two formations, the Benin Formation and Nanka Formation which are part of the lithostratigraphic units of the Niger Delta Basin. The Benin Formation is Miocene to Recent while the NankaFormation is Eocene in Age. The lithologic units encountered during this field work were; sandstone, sand, clay and silt. Physical sedimentary structures such as; cross beds, ripples, stratifications and biogenic structures in form of burrows of cylindrical shapes. The bivariate plot of MPSI versus OP Index shows that higher percentage (% ) of the pebbles lie within the river environment except for the plot of pebbles for Oboro which indicated beach. The plot of the sphericity against the OP Index for Nnewi and Nnobi both fell on the River side of the plot while that of Oboro fell on the Beach. The cross bed analysis shows a unimodal direction plot which helps to indicate the direction of sediment flow which infers that sediments are flowing from the Anambra basin into the Niger Delta Basin.
TABLE OF CONTENTS
List of Tables -- -- -- - -- - -- -- --xi
List of Figures -- -- -- -- -- -- -- -- --xii
Abstract -- -- -- -- -- -- -- -- -- --xv
CHAPTER ONE
INTRODUCTION
1.1 Location, Extent and Accessibility-- -- -- -- -- --1
1.2 Climate and Vegetation -- -- -- -- -- -- --3
1.3 Geomophology of The Area-- -- -- -- -- -- --4
1.4 Drainage Pattern -- -- -- -- -- -- -- --5
1.5 Literature Review -- -- -- -- -- -- -- --7

1.6 Purpose of the Study -- -- -- -- -- -- -- --10
1.7 Methodology -- -- -- -- -- -- -- - --10
1.7.1 Equipments Used in the Field -- -- -- -- -- --18
1.7.2 Some Problems Encountered and Precautions Taken -- --19
CHAPTER TWO
REGIONAL TECTONIC SETTING
2.1 Nanka Formation -- -- -- -- -- -- -- --20
2.2 Benin Formation -- -- -- - -- -- -- --20
2.3 Niger Delta Basin -- -- -- -- -- -- -- --22
CHAPTER THREE
3.1 Unit A: Sandstone Lithofacies -- -- -- -- -- --26
3.1.1 Friable Sandstone Lithofacies -- -- -- - -- --27
3.1.2 Fossilized Sandstone Facies -- -- -- -- -- --28
3.1.3 Ferruginized Sandstone Lithofacies -- -- -- -- --29
3.2 Sedimentary Structures -- -- -- -- -- -- --33
3.2.1 Biogenic Structures -- -- -- -- -- -- --33
3.2.2 Physical Sedimentary Structures -- -- -- -- -- --34

3.3.3 Chemical Sedimentary Structures -- -- -- -- --36
3.4 Sieve Analysis -- -- -- -- -- -- --37
3.4.1 Standard Deviation -- -- -- -- -- -- -- --38
3.4.2 Skewness -- -- -- -- -- -- -- -- --39
3.4.3 Kurtosis -- -- -- -- - -- -- -- --39
3.5 Pebble Morphometric Analysis -- -- -- -- -- --48
3.5.1 Bivariate Plots for Pebble Morphometric Analysis -- -- --48
3.5.2 The Dark Grey Shale Lithofacies -- -- -- -- --56
3.6 Paleontology -- -- -- -- -- -- -- -- --56
3.6.1 Paleoenvironment -- -- -- -- - -- -- --57
3.6.2 Correlation with Named Formation -- -- -- -- --58
3.6.3 Age -- -- -- -- -- -- -- -- -- --58
CHAPTER FOUR
STRUCTURAL GEOLOGY
4.1 Sedimentary Structures -- -- -- -- -- -- --59
4.1.1 Physical Sedimentary Structures -- -- -- - -- --59
4.1.2 Chemical Structures -- -- -- -- -- -- ---63

4.1.3 Biogenic Sedimentary Structures -- -- -- -- --64
4.2 Structural Geology-- -- -- - -- - -- --65
4.2.1 Fractures and Joints -- -- -- -- -- -- --65
4.3 Regional Dips -- -- -- -- -- -- -- --66
CHAPTER FIVE
ENVIRONMENTAL GEOLOGY
5.1 Geologic Hazards in the Study Area -- -- -- -- --67
5.2.1 Gullies-- -- -- -- -- -- -- -- -- --67
5.1.2 Mass Wasting -- -- -- -- -- -- -- --69
5.1.3 Flooding -- -- -- -- -- -- -- -- --70
5.1.4 Slide and Slumps -- -- -- -- -- -- -- --71
5.2 Effects of Geological Hazards -- -- -- -- -- --71
CHAPTER SIX
ECONOMIC GEOLOGY, HYDROGEOLOGY AND ENGINEERING
GEOLOGY OF THE STUDY AREA
6.1 Economic Geology -- -- -- -- -- -- -- --73
6.2 Hydrogeology -- -- -- -- -- -- -- --77

CHAPTER SEVEN
Summary and Conclusion -- -- -- -- -- -- --79
Appendix -- -- -- -- -- -- -- -- -- --81

xi
LIST OF TABLES
Table 1.1: The mathematical formula employed in the calculation of the morpho metric properties and statistical parameters. -- --17
Table 1.2: Stratigraphic Framework of Southeastern Sedimentary Basins showing the position of Nanka and Benin Formation -- --21
Table 2.1 Correlation of subsurface formations in the Niger Delta with the out crops in the study area -- -- -- -- -- -- --24
Table 3.2 Values of Statistical Parameters for Sieve Analysis -- --38

LIST OF FIGURES
Fig 1.1 Accessibility Map of the Study Area -- -- -- -- --2
Fig: 1.2 Drainage Map of the Study Area -- -- -- -- --6
Fig 1.3: Structural Units of Southeastern Nigeria (After Short &Stauble,
1967) -- -- -- -- -- -- -- -- -- --8
Fig 3.1: litholog of section of Nanka Sand outcrop In Alor showing an
upward coarsening sequence -- -- -- -- -- --27
Fig. 3.2: litholog of section of Benin Formation outcrop In Ojoto showing an
upward fining sequence with interbeds of Clay. -- -- --28
Fig 3.3: litholog of section of Nanka Sand outcrop In Nnobi gulley showing
an upward coarsening .facies pattern. -- -- -- -- --29
Fig 3.4: litholog of section of Benin Formation outcrop In Ichi, near Oboro
spring showing an upward -- -- -- -- -- --30
Fig 3.5: litholog of section of Nanka Sands outcrop In Akwu-Ukwu showing
an upward fining with some very pebbly -- -- -- --31
Fig 3.6: litholog of section of Nanka Sands outcrop In Umudim-Nnewi
showing a sand stone unit with intercalation of clay beds. --32
fig 3.7 graph of Alor bed A -- -- -- -- -- -- --41


Fig 3.8: graph of Alor bed B -- -- -- -- -- -- --41
Fig3.9:GraphOfAlorBedC -- -- -- -- -- -- --43
Fig 3.10: Graph of Nnobi sample A -- -- -- -- -- --44
Fig. 3.11: GraphofNnobibedC -- -- -- -- -- --45
Fig. 3.12: Graph of Nnobi bed D -- -- -- -- -- --46
Fig. 3.13: graph of UmudimNnewi bed -- -- -- -- --47

Fig. 3. 14a: a bivariate plot of sphericity against Elongation ratio for OboroFig. 3.14b: Bivariate Plot of Roundness against OP Index for Oboro --48 Fig. 3.1 5a: A Bivariate Plot of Sphericity against Elongation Ratio for
Nnewi -- -- -- -- - -- -- -- --49 Fig. 3.1 6b: Bivariate Plot of Roundness against OP Index for Nnewi --50 Fig. 3.1 7a: Bivariate Plot OfSphericity Against OP Index For Nnewi --51
Fig. 3.1 7b: Bivariate Plot of Roundness against Elongate For Nnobi --52
Fig. 3.18: Rose Diagram Showing Paleocurrent Data -- -- --53
Fig 4.1 Planar cross beds noted in Nanka Formation, Nnobi -- --55
Fig 4.2 Horizontal beds in the Nanka Formation, Nnobi -- -- --60
Fig 4.3 Liesegang Structures -- -- -- -- -- -- --64

Xiv
Fig 4.4: Ophiomorpha Burrows found at Umudim, Nnewi. -- --65
Fig 5.1 Gully erosion site at Nnobi -- -- -- -- -- --69
Fig 6.1 Laterite in an outcrop at Ojoto -- -- -- -- -- --74

CHAPTER ONE
INTRODUCTION
1.1 Location, Extent and Accessibility
This study was carried out in Nnewi and its environs, all in Anambra state. The study area is bounded by latitudes 06 00’N to 06 07’N and longitudes 006 45’E to 006 59’E. Some of the towns in the area are; Abatete, Ideani, Nnobi, Ojoto, Nnewiichi, Awka-etiti, Ichida, Ichi, Obosi, Oraifite and IyiowaOdekpe.
The area is accessible by major roads, but mostly by minor roads and foothpaths. The major and monor roads lead to the outcrops of road-cut exposures while the foothpath lead to outcrops of erosional exposures. The major access roads are the Agulu-oraukwu, Nnobi-Nnewiroad, the Oraukwu¬abatete road, the Nnobi-Ideani-ojoto-onitsha road, and the dual carriage express way from onithsha to oraifite.othes are Nnewi-ichi-Obosi roads and a host of minor roads.


Fig 1.1 Accessibility Map of the Study Area

1.2 Climate and Vegetation
The study area has a tropical climate characterized by two main seasons; the rainy and dry seasons. The rainy season lasts between the months of April and October while the dry season lasts from the months of November to march.
Rainfall is generally high during the rainy season except sometime in the month of august when rainfall is reduced. The temperature of the study area varies in magnitude according to the period of the year. The hottest period is usually between February and april. The temperature is usually high alloverthe yearwith an average minimum to maximium temperature of 25 degree centigrades and 32 degree centigrade respectively. The dry season is characterized by the dusty dry hammaternwind. This lowers the temperature appreciably in the months of December to January. With associated features like excessive evaporation, low relative humidity (20%), low rainfall and general dryness (egboka 1993). The daily mean humidity of the area varies between 40% to 92%, it is generally high during the early hours of the day.
The study area is located in the Awka –Orlu highlands of south eastern
Nigeria. The landscape is undulating in some places and flat terrained in

others.the topography of the study area is lower on the western half, rising between 150 to 450 meters in places and punctuated by valleys and hills that determine the natural course of the Idemili river running from east to west. The hills that define the valleys of the tributaries of River MmiliEze to the south.the friable to loosed soil conditions combined with the steep slope of the valleys of River idemmilihas been responsible for the excessive and pesistent soil erosion experienced in the subregion of the study area.
1.3 Geomophology of the Area
The study area has an undulating topography ranging from gently sloping low lands to slightly steep highlands. These high lands area numerous e in the study area. The topography and geomorphology of a place often reflects the tectonic and geological events that occurred over a long period of time and tectonically continue to shape the geomorphic landscapes. The regional ggeomorphicfeatures that has shaped the landscape is the Awka-orluhighlands (Floyd, 1965) which slopes gently into the floodplains of the river niger west of the study area.

1.4 Drainage Pattern
The study area is mainly drained by the Idemmili River, which flows westwards into the major lower River Niger drainage basin. Tributaries of the Idemmili River rise from the highlands and flows swiftly into the IdemiliRiver actively caving deep gulleys. The MmiliEze River also flows westwards from the Nnewi plateau into the floodplains of the River Niger.these rivers form a dendritic pattern which indicates the loose and unconsolidated nature of the uderlaying formation of the study area.


Fig: 1.2 Drainage Map of the Study Area

1.5 Literature Review
Previous studies have been carried out on sedimentology and stratigraphy of the study area by Reyment, 1965; Hoque and Ezepue, 1977; Banerjee, 1979; Ladipo, 1985; Amajor,1986,1989; Reijers and Nwajide, 1996; Awalla and Eze, 2004, and Nwajide, (2005). . It is believed that the Anambra basin has age ranging from lower cretaceous to upper cretaceous (Albian to Maastritchtian).Researchers such asas Peters (1978), 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 3.0 below.


Fig 1.3: 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.

Short and Stuable (1976), suggested that three depositional cycles occurred in the sedimentary basins of the region with regards to the tectonic activities of the region. The first cycle was confined to the Benue Trough, the second one filled the Anambra Basin and the Afikpo syncline, whereas the third cycle formed the tectonic separation of the Niger Delta. Hogue (1979) studied the significance of the textural and petrographic aspects of several Cretaceous sandstone in the southeastern Nigeria and he suggested that granite of the Cameroon basement complex must have accounted for a large part of the second depositional cycle which is ditinquished by quartz arenite.
Kogbe (1976) and Nwajide (1972) recognised the Nanka Formation as a distinct formation which is a lateral equivalent of the Ameki Formation. whileOrjiaka and Ogbukagu (1976) considered the Nanka Formation as a member of the Ameki Formation. Nwajide(1977) studied the mineralogical and textural characteristics of Nanka Formation and noted that the unit is composed of loosely consolidated quartz arenite and is completely devoid of cement. From his investigation he established that the study area is underlain by the Nanka Formation. Nwajide and Hoque (1979) noted the role that the

poorly consolidated Nanka Formation plays giving rise to gully erosions. Egboka (1993) studied the hydrogeology of Nanka Formation and noted that the thickness of the aquifer ranges from 137m in places of low elevation and 174m for places of higher elevation.
1.6 Purpose of the Study
The purpose of the study is to have a better understanding of the geology of the study area. This entailed;
1. producing a geologic map of the area with description of the mapped units
2. Evaluating the engineering properties of the soil in the study area.
3. interpreting depositional environment
4. Evaluating the sedimentologic and stratigraphic information on the area.
1.7 Methodology
This involves the methods and principles used in this work. This study was accomplished through

1. Desk studies
2. Reconnaissance survey
3. Detailed geologic survey
4. Laboratory analysis
Desk Studies
Available literature on the study area was studied to get a pre-knowledge of the geology of the area. Materials such as journals, books, geologic maps.
Reconnaissance Survey
This was used to introduce ourselves to the traditional rulers and chiefs of the varicose areas to be mapped. This was aimed at sensitizing them on the mapping and to create good personal rapour with them .possible access roads and outcrops were noted.
Detailed Mapping
The detailed mapping carried out in the study area involved the observation
and mapping of contacts of lithologic units, taking note of variation inlithology, rock types, structures and other geologic features. The attitude of beds were measured (dips and strikes), using a clinometers compass outcrops were carefully studied and logged. Rock samples for laboratory studies were collected at the outcrops and photographs of interesting geologic exposures were taken.
The study of the out crop was carried out with the following procedure:
The location is taken from the GPS and recorded, the rock type is recorded after which if sand, each bed is measured for thickness and the properties recorded which includes; color, grain size, sorting, roundness, other properties, the altitude of the bed is measured if a good surface is found. Geologic Structures are recorded if present.
Structures like faults, fractures, laminar and chemical structures like Leis gangue structure, biogenic structure found were burrows identified according to their shape. After the field studies, samples were collected from each bed and labeled accordingly bearing the location and bed name. The samples were taken to the laboratory for analysis. Sieve analysis and atterberg limit test were carried out.

Laboratory Analysis

Sieve Analysis
Seven sand samples were collected from Alor, Nnobi and UmudimNnewiand were sieved according to the technique of Friedman (1979). The nest of sieve was arranged with the coarsest at the top and the pan at the bottom. The disaggregated and weighed samples of each of the sands were poured into the uppermost sieve and shook for 15minutes. The frequency curves of the samples were plotted and critical percentiles (p5, p16, p25, p50, p75, p84 and p95) were obtained and the textural parameters of the sands which include the graphic mean, median, graphic standard deviation, inclusive graphic skewness and graphic kurtosis were calculated.
Statiscal Parameters
Mean: this is the overall average grain size of the distribution. It is a product of source of supply, depositional processes and environment of deposition.

Mean = 016 + 050 + 084
3
Standard Deviation (Sorting): this is termed as the degree of uniformity orspread of the grain size particles. If the grain size range is wide, the sedimentis poorly sorted and if narrow, it is well sorted.
Standard deviation (d) = 084 - 016 + 095 - 05
4 6.6
Skewness: This represents the asymmetry of the distribution curve. Thedirection of skewness of the tail determines whether it is positively ornegatively skewed.
Skewness, SK = 084 + 016 - 2050 + 095 – 05 + 2050
2(084 – 016) 2(095 – 05)
Kurtosis: This measures the ratio of distribution (spread) at the central part tothe distribution at the tails. Kurtosis,
Kg= 095 – 05
2.44(075 – 025)

Pebble Morphormetry
A total of 300 quartz pebbles, 100 at each locations and after the measurements, they were segregated into 10 batches and at the end of it, the average of these 10 batches were taken which makes it a representative sample of 1 for each 10 pebbles. This now brought out 10 average samples, 30 in all for these three locations. These pebbles were selected for Nnobi, Nnewi and Oboro areas respectively. Pebble morph metric studies involves measurement (using vernier caliper) of the long (L), intermediate (I), and short (S) axes of pebbles from pebbly sandstones. The three mutually perpendicular axes (S, I and L) of each of the pebbles were measured and their roundness were estimated with the aid of a roundness image set of Sames (1966) (tables 14-16). Morphometric parameters which were computed include flatness ratio and elongation ratio (after Luttig, 1962), maximum projection sphericity index (after Sneedand Folk, 1958), oblate- prolate index (after Dobkins and Folk, 1970) and coefficient of flatness (after Luttig, 1962). The forms of the pebbles were noted using the sphericityform diagram of Sneed and Folk (1958) as shown in fig.8a and b. The bivariate plots of

M.P.S.I versus OP Index, Roundness versus Elongation ratio were very useful in the environmental discrimination of the pebbles. Morphometric and rose diagram was made from the azimuths of cross beds for inference on the paleocurrent direction during deposition of sediments.

Table 1.1: The mathematical formula employed in the calculation of the morpho metric properties and statistical parameters. (Modified from 1 E.N., Asiegbu,;J.O., Etu- Efeotor, Natural and Applied Sciences Journal Vol. 9 No. 3, 2008).


Atterberg Limits
The atterberg limit test comprises the plastic limit and the liquid limit tests; this was carried out so as to be able to get information on the engineering geology of the study area.
For the liquid limit test, casagrande equipment was used, recording the number of blows and moisture content, a graph was plotted to determine the liquid limit. While the plastic limit was determined by rolling a wet sample of the soil (clay or laterite) into a 3mm thick thread and getting the weight before and after drying for 48hours. Subtracting the liquid limit from the plastic limit gave the plasticity index.
1.7.1 Equipments Used in the Field Some of the equipments used include;
1. Base map: where features are located and also the area traversed.
2. Geologic compass; for measuring attitudes of beds
3. Measuring tape: for measuring bed thickness
4. Field note: for recording information during field work

5. Sample bags: for collecting samples
6. GPS: for taking coordinates
7. Haversack: for caring equipments
8. Camera: for taking photographs
1.7.2 Some Problems Encountered and Precautions Taken
Some limitations were encountered during the field work one of which was that the topographic map that was available was out dated and as such some of the features had changed their form, example is some footpaths that have been converted to major roads and some structures such as some markets that have long stopped being in existence. Some possible errors due to instruments and human errors cannot be ignored. Traversing the thick vegetation and long distance to locate most of the physical features in the area also constituted some problems.

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