GEOLOGY AND OCCURRENCE OF GROUNDWATER IN ISHIEKE AREA SOUTHEASTERN NIGERIA

ABSTRACT

The study area is located in the southeastern part of Nigeria. The area is predominantly, Abakaliki formation of Albian, Asu-River group, Lower Benue Trough. The area lies between latitude N060221 011 to N060 281 011 of the equator and longitude E0080 001 0011 to E0080 061 0011 of the Greenwich meridian. The study was carried out to ascertain the geology and the occurrence of groundwater in the area through detail geological field mappings geophysical investigation borehole drilling and pumping test. Field observations showed that, the area is made up of two litho logical units. Unit “A” (dark gray to blue indurate shale) and Unit “B” (calcareous limestone); Geologic field mapping revealed that Ishieke area is underlain by Abakaliki shale of Abakaliki formation, Asu-River limestone, siltstone and intrusive rocks, all belong to the Asu-River group southern Benue trough. The Albian Asu-River group consist of dark gray to blue indurate shale which covers the entire Abakaliki formation with limestone, lenses of sandstone, intrusive dolerite sill, diorite, basalts and pyroclast. The occurrence of groundwater in the Ishieke area is locally distributed; this was confirmed with geophysical investigations and well drilling. Groundwater in the study area occurs in fractured, weathered zones or intrusive boundaries, which are mostly fractured shale and limestone which have been tectonically affected. The geophysical data acquired was interpreted with IPI2WIN software. The borehole was drilled with Rotary hammer drilling rig. The pumping test was done with 1HP submersible pump (high head), the test was done for 180 minutes and quick recovery of about 75 minutes was recorded showing that the aquifer is prolific.

TABLE OF CONTENTS

Chapter title Page

Approval                                                                                                                 iii

Dedication                                                                                                              iv

Acknowledgements                                                                                                 v

Abstract                                                                                                                    vi

Table of Content                                                                                                        vii

Chapter One                                                                                                                 1

Introduction                                                                                                                 1

1.1 Location and Accessibility                                                                                       2

1.2 Aim and Objective                                                                                                    4

1.3 Literature Review                                                                                                     5

1.4 Materials and Methods                                                                                            6

1.4.1 Materials                                                                                                                6

1.4.2 Methodology                                                                                                         6

1.5 Topography and Drainage                                                                                        8

1.5.1 Topography                                                                                                            9

1.5.2 Drainage                                                                                                                 9

1.5.2 Climate and Vegetation                                                                                         9

1.5.2.1 Climate                                                                                                             10

1.5.2.2 Vegetation                                                                                                        10

1.5.2.3 Soil Type                                                                                                            11

Chapter Two                                                                                                                 13

2.0 Regional Geology                                                                                                    13

2.1 Tectonic Setting and Evolution of Aulacogen                                                          15

2.2 Stratigraphic Setting                                                                                                16

Chapter Three                                                                                                                21

Local Stratigraphy of the Study Area                                                                             21

3.1 Lithologic Description                                                                                             21

Chapter Four                                                                                                                 35

4.0 Result and Discussion                                                                                             35

4.1 Geophysical Survey VES (Vertical Electrical Sounding)                                         35

4.1.1.1.2 Recommendations                                                                                         36

4.1.1.2. Discussion of results                                                                                         36

4.1.1.2.2 Recommendations                                                                                         37

4.1.2 Pumping test data                                                                                                38

4.1.2.2 Recovery                                                                                                            39

Chapter Five                                                                                                                 42

5.1 Sedimentary structures                                                                                         42

5.2 Tectonic structures                                                                                                 44

5.3 Igneous intrusion                                                                                                   46

Chapter Six                                                                                                                 46

6.1 Economic geology                                                                                                 46

6.1.1 Shale                                                                                                                    46

6.1.2 Limestone                                                                                                             46

6.1.3 Dolerite                                                                                                                 47

6.2 Hydrogeology                                                                                                         47

Chapter Seven                                                                                                             48

Summary and Conclusion                                                                                            48

7.0 Summary                                                                                                                 48

7.1 Conclusion                                                                                                             48

7.3 Recommendation                                                                                                 49

References                                                                                                                   50

Appendix                                                                                                                     53

LIST OF TABLES

1: Regional stratigraphic sequence of southeastern Nigeria. (Modified by Reyment

(1965), Murat (1972) and Hoque (1977).                                                                     21

2: .Local Stratigraphy of the Area                                                                                 22

3: Borehole Lithology from Monitoring Borehole at EBSU Perm Site

(location one)                                                                                                             25

4: Pumping Test data                                                                                                 41

5: Pumping Test Recovery Data                                                                                 42

6: Showing Trend of joint at location Two                                                                 44

LIST OF FIGURES

Figure 1: Accessibility map of Ishieke and Environment.                                             3

Figure 2: Map of Ebonyi State showing the study area.                                               4

Figure 3: Showing equipment used during the field work                                           7

Figure 4:Drainage map of Ishieke and Environment                                                    10

Figure 5: Mean annual rainfall of Nigeria for 1951 – 1995 (Adapted from Igbozuruike, 1975)                                                                                                                             11

Figure6: Vegetation of Ishieke Environment                                                                 12

Figure 7: Geologic map of southern Benue Trough (Murat, 1972)                               15

Fig.8Geologic Map of the Study Area.                                                                         23

Fig:9.Borehole point at EBSU perm site (location one)                                                 24

Fig:10 brown shale at location Two.                                                                             26

Fig:11Showing Bluewish- gray shale at location Six                                                     26

Fig.12: Brown shale at location eight.                                                                         28

Fig.13: Hammer Pointing at Shale Bed in Edomia Village.                                         29

Fig.14: Pencil showing Fissile Shale at Umuagarah Village                                        30

Fig:15 Dolerite intrusion at Alibaruhu village.                                                            32

Fig: 16.Limestone at location                                                                                     33

Fig.17: limestone with solution cavity at Idembia village Permanent Site.                34

Fig.19Limestone as observed at river bank in Umuagara Ngbo.                                35

Fig 20.VES GRAPH 1                                                                                                    37

Fig. 21 VES GRAPH 2                                                                                                    38

Fig.22 VES GRAGH 3                                                                                                     40

Fig. 23Rose Diagram Showing Trend of Joints at Location Two                                 45

Fig.24Dolerite sill at Alibaruhu village                                                                         46