ABSTRACT
The geological and geophysical survey of Obeagu and environs in Awgu local government area of Enugu state. In other to study the area, various lithologies and description of the exposed outcrop sections based on their sedimentological characteristics were identified, dip and strike was taken on outcrops with natural bedding planes to get Azimuths of the beds. lithological and formation boundaries were delineated and indicated on the topographic map and other branches of geology like hydrogeology, economic geology, engineering geology and environmental geology were studied and interpreted and geophysical surveys were done. Also studies of existing literature, reconnaissance survey were done to have a pre-knowledge of the study area. Field mapping and samples were collected in order to carry out laboratory analysis such as grain size, Atterberg’s limit test and water analysis to have a better knowledge of the area. The study area is made up of three geologic formations which are the Owelli Sandstone; Mamu Formation and Ajali sandstone. The sand samples were subjected to grain size analysis and the result shows that they are medium-coarse grained in texture. The environment of deposition was beach/shallow agitated marine and fluvio-deltaic. The Atterberg limit test shows that the samples will be suitable for filling and embankment, sub-base course but with careful consideration. Paleocurrent analysis confirmed that the paleocurrent direction was southwest and deformation in southeast with the aid of cross-beds, ripple and joints. The water samples when compared to the World Health Organization permissible standards showed that the water is chemically and bacteriologically polluted and not suitable for domestic use but can be suitable for other purposes like agriculture and industries. From the geophysical data, groundwater can be exploited within areas covered by Ajali sandstone. The drainage pattern within the study area is dendritic. Boreholes should be drilled to reduce contamination of surface water, allocation of resources and engaging the services of earth scientist to tackle the problem of erosion and monitoring of quarrying site to check the extent of environmental hazards in the area.
TABLE OF CONTENT
Cover page – – – – – – – – – – i
Dedication – – – – – – – – – – ii
Acknowledgement – – – – – – – – – iii
Abstract – – – – – – – – – – iv
Table of content – – – – – – – – – v
Chapters – – – – – – – – – – vi
List of tables – – – – – – – – – – ix
List of plates – – – – – – – — – – x
List of figures – – – – – – – – – – xi
CHAPTER ONE INTRODUCTION – – – — – 1
1.1 Background of the study area – – – – – – – 1
1.2 Location and Accessibility – – – – – – – 2
1.3 Aim and Objectives – – – – – – – – 3
CHAPTER TWO LITERATURE REVIEW – – – – – 4
2.1 Geomorphology of the area – – – – – – – 6
2.1.1 Topography – – – – – – – – – – 6
2.1.2 Weathering and Erosion – – – – – – – – 7
2.1.3 Drainage pattern – – – – – – – – – 8
2.1.4 Climate and Vegetation – – – – – – – – 9
2.1.5 Vegetation – – – – – – – – – – 11
2.2 Regional geologic setting of the study area – – – – – 12
2.2.1 Tectonics and stratigraphy of south eastern Nigeria – – – – 14
2.2.3 Geology of ObeaguMmaku and its environs – – – – – 17
2.3 Hydrogeology of the area- – – – – – – – 22
2.3.1. Surface water hydrology – – – – – – – 22
2.3.2 Groundwater hydrology – – – – – – – 23
2.4 Geophysical surveying – – – – – – – – – 23
2.4.1 Theory of electrical resistivity method – – – – – – 24
2.4.2 Vertical electrical sounding – – – – – – – – 24
2.4.3 Plotting of vertical electrical sounding curve – – – – – – 25
CHAPTER THREE METHODOLOGY OF THE STUDY AREA. – – – 26
3.0.1 Desk study of Obeagu and environs – – – – – – – 26
3.1 Geological survey and sample collection – – – — – – 26
3.1.1 Equipments used for geological survey – – – – – – 27
3.1.2 Precaution taken in the field – – – – – – – 28
3.2 Outcrop studies and description – – – – – – – 29
3.3 Laboratory Analysis and data collection- – – – – – – 56
3.3.1 Grain size analysis – – – – – – – – – 57
3.3.2 Atterbergs limit test – – – – – – – – – 61
3.3.3 Liquid limit – – – – – – – – – – 62
3.3.4 Plastic Limit – – – – – – – – – – 63
3.3.5 Plasticity Index – – – – – – – – – 64
3.3.6 Application of liquid limit/plastic limit – – – – – – 64
3.4 water sample data collection- – – – – – – – 65
3.5 Structural Geology data collection – – – – – – – 65
3.6 Economic geology data collection – – – – – – – 65
3.7 Electrical resistivity data collection – – – – – – – 66
CHAPTER FOUR LABORATORY RESULT – — – – 71
4.0.1 Result of Sieve analysis – – – – – – – – 71
4.1.1 Paleocurrent Analysis- – – – – – – – – 73
4.1.2 Environment of deposition from interpretation of sieve analysis – – – 74
4.1.3 Engineering geology – – – – – – – – – 75
4.1.4 Result and interpretation of atterbergs limit test – – – – – 75
4.2 Water sample result – – – – – – – – 76
4.2.1 Water quality assessment – – – – – – – – 77
4.2.2 Hydrogeochemistry- – – – – – – – – 77
4.2.3 Interpretation – – – – – – – – – 78
4.3 Sedimentary structure of the area – – – – – – – 81
4.4 Economic geology of the area – – – – – – – 85
4.4.1 Environmental geology of the area – – – – – 87
4.5 Geophysical survey – – – – – – – – 91
4.5.1 Geoelectric curve types – . – – – – – – 91
4.5.2 Qualitative interpretation – – – – – – 91
4.5.3 Quantitative interpretation – – – – – – – 92
4.6 Correlation of geoelectric sections – – – – – – – 100
4.6.1 Aquifer conductivity- – – – – – – – – 101
4.6.2 Aquifer transmissivity – – – – – – – – – 102
4.7 Discussion – – – – – – – – – – 103
CHAPTER FOUR SUMMARY AND CONCLUSION – – – – – 105
5.1 Recommendation – – – – – – – – – 106
References – – – – – – – – – – – 108
Appendix – – – – – – – – – – – 113
LISTS OF TABLES
Table 2.0: Lithostratigraphic framework of the Early Cretaceous-Tertiary
Period in the southeastern Nigeria (after Nwajide, 1990).- – – 6
Table3.3.1 Descriptive terms and scale (Folk and ward, 1957) – – – 59
Table: 3.2 Verbal Terms and Values for Atterberg’s Limit and Computations. – 63
Table 4.1: Statistical parameters calculated from sieve analysis – – – 71
Table 4.4: Computed Data for Atterberg’s Limits Tests – – – – 75
Table.4.5 showing Nigerian specification for LL and PI for engineering work – – 76
Table 4.6: Results of water analysis – – – – – – – 78
Table 4.6b: Classification of VES curve types in the study area. – – – 92
Table 4.6: VES 1 Ugbo-Okpala community secondary school layers – – 93
Table 4.7 VES 2 Ebenebe village junction layers – – – – – 96
Table: 4.8. VES 3 Igwebuike primary school layers – – – – – 98
LISTS OF PLATES
Plate 2.1: Vegetation of the study area – – – – – – 12
Plate 3.1: Crossbeds at Awgunta – – – – – – – – 30
Plate 3.2: Nkwashi stream – – – – – – – 32
Plate 3.3: Crossbeds at a quarry site along Obeagu road – – – – 34
Plate: 3.4 Ofio spring – – – – – – – – – 38
Plate 3.5: Gully erosion site in the study area. – – – – – – 40
Plate 3.6: showing a section Nmiri father. – – – – – – – 44
Plate 3.7: Obuo Village Spring. – – – – – – – – 47
Plate 3.8: Ngene stream. – – – – – – – – – 54
Plate 3.9: Sieve sets and electrical weighing machine. – – – – – 57
Plate 3.10: Project group during VES survey. – – – – – – 68
Plate 3.11: (a)Setup of equipment (b) Ammeter(c) power source/battery
(d) Inverter (e) cable reel: (f)Voltmeter – – – – – 70
Plate 4.1: Outcrop showing laminations at Awgunta – – – – – 82
Plate 4.2: Outcrop opposite St. Joseph Medical clinic Mmaku showing crossbed – 83
Plate 4.3: Outcrop showing joints within the gully erosion site – – – 84
LISTS OF FIGURES
Fig 1.1: Accessibility map of Obeagu. – – – – – – 2
Fig: 2.1 Topographic map of Obeagu – – – – – – – 7
Fig 2.2: Drainage map of Obeagu- – – – – – – – 9
Fig 2.3Map of Nigeria showing the annual rainfall distribution and the position of the
Study area (source: Wikipedia) – – – – – – – 7
Fig 2.4: Enugu climate graph. – – – – – – – – 9
Fig 2.5: Map of Nigeria showing natural vegetation (source Wikipedia). – – 11
Fig: 2.6. Stratigraphic section of the Anambra Basin from the Late
Cretaceous through the Eocene and time equivalent Formations in
the Niger Delta. Modified from Reijers and others, 1997. – – – 17
Fig: 2.7 Geologic map of the study area. – – – – – – 18
Fig. 3.1: Lithologic log of Outcrop at station One – – – – – 31
Fig. 3.2: Lithologic log of Outcrop at station three – – – – – 35
Fig. 3.3: Lithologic log of Outcrop at station fiour – – – – – 37
Fig 3.4 Lithologic log of Outcrop at station five – – – – – – 39
Fig. 3.5: Lithologic log of Outcrop at station six – – – – – 41
Fig. 3.6: Lithologic log of Outcrop at station seven – – – – – 43
Fig. 3.7: Lithologic log of Outcrop at station eight- – – – – – 45
Fig. 3.8 Lithologic log of Outcrop at station nine – – – – 48
Fig. 3.9: Lithologic log of Outcrop at station ten – – – – – 49
Fig. 3.10: Lithologic log of Outcrop at station eleven – – – – 51
Fig. 3.11 Lithologic log of Outcrop at station twelve – – – – 53
Fig 3.12: Lithologic log of Outcrop at station thirteen – – – – 55
Fig 3.9: Showing equipment for Atterberg’s limit (A. Casagrande, weighing pan and groove B. Mortar and pestle C. Glazed glass) – – – – – – 62
Fig.3.13. Flow of current and voltages during VES exercise (Dobrin and Savit, 1988).
Note: The current electrode spacing equals the depth penetrated. – – – 67
Fig: 4.1: bivariate plot of Y2 against Y1- – – – – – – 72
Fig: 4.2: bivariate plot of skewness against standard deviation – – – – 72
Fig: 4.3: bivariate plot of standard deviation against mean size – – – – 73
Fig: 4.4: Rose diagram of crossbeds – – – – – – — 73
Fig: 4.5: Rose diagram of ripples – – – – – – – – 74
Fig: 4.6: Rose diagram of joints – – – – – – – – 74
Fig. 4.5.1: Classification of curve types (Keller and Frischnecht, 1966; Telford et. al., 1990) – – – – – – – – – – – 91
Fig. 4.6 a: VES 1 Ugbo-Okpala community secondary school curve – – 94
Fig. 4.6 b: Lithologic log of VES 1 – – – – – – – 95
Fig. 4.7 a: VES 2 Ebenebe village junction curve 2 – – – – – 97
4.7 b: Lithologic log of VES 2 – – – – – – – – 97
Fig. 4.8 a: VES 3 Igwebuike primary school curve – – – – – 99
Fig. 4.9: Correlation of geo-electric layers – – – – – – – 100
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE STUDY AREA
The study is located in Obeagu, Awgu LGA of Enugu state. The major villages covered are Obeagu, Amoli-Owelli, Egwuachi, Awgunta and Mmaku. The study area is a rural area with no major industries present. The settlement pattern is dispersed. The occupations practiced by the indigenes in the study area include Quarrying, farming, fishing and transporting. The major means of transportation is by vehicles, bicycles and motorcycles.
Surface water has been the major source of water for both domestic and industrial water supply in the area, which is known to be prone to contamination. However, with the intention of introducing recent technological development to make groundwater to be the choice of water supply in the area, electrical resistivity survey was conducted to determine the depth of aquifer in the area.
Electrical resistivity method is one of the geophysical methods used in groundwater exploration. The subsurface information inferred from this survey gives a better knowledge of the aquifer systems and a more realistic picture of groundwater potential of any area. The technique has been successfully used in investigating groundwater potential in different geological settings. Also this method was used to explore for groundwater in a sedimentary environment (Emenike, 2000). In this study, vertical electrical sounding was used to establish the occurrence and depth of groundwater within the part of Obeagu area in the Anambra Basin.
Although some work might have been done in the area in the past, the records were not well documented. This work will help to facilitate further studies on the geology of the area.
1.2 LOCATION AND ACCESSIBILITY
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The study area is located in Obeagu and environs which lies within 007° 23′ E and 007° 27′ E and latitude 06° 7′ N and 06° 11′ N. The study area has an area extent of about 44.6 km2. The area of study encompasses Obeagu, Amoli-Owelli, Egwuachi, Awgunta and Mmaku in Awgu Local Government Area in Enugu State. It is accessible through Enugu-Port Harcourt expressway by Akinaukwa junction or through the Oji-Agwu express way.
Fig 1.1: Accessibility map of Obeagu
1.3 AIM AND OBJECTIVES
The aims and objectives of this research work include:
- To identify various lithology and description of the exposed outcrop sections based on their sedimentological characteristics.
- To take dip and strike in an outcrop within the study area in other to get the azimuths of beds.
- To delineate boundaries between one lithology and the other, or between one formation and another.
- To identify and interpret the valuable economic deposits, hydrogeology, engineering and environmental geologic features in the area and to carry out geophysical survey.
- Take photographs and rock samples for sieve analysis, water analysis, Atterberg and liquid limit test.
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