GEOLOGY AND SEDIMENTOLOGY OF AKANU- OHOFIA AREA, SOUTHERN ANAMBRA BASIN

CHAPTER ONE

INTRODUCTION

Akanu-Ohofia Area comprises of villages in Ohofia local government area of Abia state. Communities within the studied area include; Akanu, Isi-ugwu, Ndi-uduma, Abia, Ania, Ndiokala, Ndi-orieka, Amankwu and Eziafor (Figure 1). The study area is part of the Southern Anambra Basin comprising of Akanu-Ohafia and its adjoining areas and lies within latitudes 50 31I - 50 36I N and longitudes 70 49 I - 70 54 I E. The Anambra Basin is located in the southern part of the regionally extensive northeast-southwest trending Benue Trough. It is a synclinal structure consisting of more than 5,000m thick of upper Cretaceous to Recent sediments representing the third phase of marine sedimentation in the Benue Trough (Figure 6). It is bounded on the west by the Precambrian basement complex rocks of western Nigeria and on the east by the Abakaliki Anticlinorium. The stratigraphic succession of the Anambra Basin comprises of the Campanian to Maastrichtian Enugu/Nkporo/Owelli Formations (lateral equivalents). This is succeeded by the Maastrichtian Mamu and Ajali Formations. The sequence is capped by the Tertiary Nsukka Formation and Imo Shale. The north-south trending of Enugu escarpment forms the major watershed between the lower Niger drainage system to the west, and the Cross-River and Imo drainage systems to the east. It is an asymmetrical ridge stretching in a sigmoid curve for over 500 km from Idah on the river Niger to Arochukwu on the Cross-River. The study area is accessible from Afikpo in Ebonyi state, Umuahia, Bende, Arochukwu and Ini in Akwa Ibom state through a network of well developed roads. Some of these roads are the Umuahia Abiriba  - Ohofia – Arochukwu road. The Afikpo – Nguzu – Ohofia Ebem – Akanu road. The minor roads include; Akanu – Isiugwu road, Ndi Uduma – Amankwu road, Ebem – ndi Uduma road. Footpaths were also used to access villages in the area (Figure 1).

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