INTRODUCTION
1.1
The area of study is in the northeastern border of Afikpo North Local Government Area of Ebonyi State. The scope area of work covers geological mapping and aspects of geology like: lithology,sedimentology, stratigraphy, [biostratigraphy], and geomorphology, production of geological map, structural geology, and environmental analysis of samples collected from the study area. In the Southern Benue Trough, the nature of most of the units and the dense vegetation as a result of a wet tropical climate have hindered field studies and created a missing link in the proper explanation of the depositional and provenance framework of the basin. The Afikpo area offers a unique opportunity to study and understand thedepositional and provenance processes in the southern Benue Trough as the highly indurated nature of the sediments allow for an abundance of outcrops that is unmatched anywhere else in the region. The fundamental bjectives of this field work is to give detailed description of the geology of Ozara Ukwu and its environs which can be used in interpretation and delineating the depositional environment, areas of environmental hazards and minerals of economic importance in the study area.
1.0 BACKGROUND STUDY
The Benue trough is thought to be as a collection of pull-apart basins, related to transcurrent or strike-slip movement along deep-seated basement shear zones of Pan African origin, reactivated as oceanic transform faults (Benkhelil, 1982 and 1989, Guiraud, 1993).This view is supported by field evidence in the northern Benue Trough where the climate and the nature of the sedimentary units allow for classic geologic study. Geological and geophysical studies have enabled a broad understanding of the geology of the Benue Trough. It was only in the latter part of the 20th
century that the structural framework, within the Benue Trough was largely resolved. The Ozara Ukwu area offers a unique opportunity to study and understand the depositional processes, and Paleoenvironmental reconstruction of the Southern Benue Trough. Being highly indurated, the sediments allow for an abundance of outcrops which were studied in details. However, the dense vegetation of the area, which was as a result of wet tropical climate, hindered field studies and created a missing link in the proper explanation of the structural framework of the basin, (Okonkwo, 2014).
1.1Geographical setting
The study area, Ozara Ukwu and its environs, is located at the northeastern borderof Afikpo North Local Government Area of Ebonyi State. It lies within latitude of 050
55’N and 050
50’N and longitude of 070
55’E and 070
50’E. Notable towns that situates within the study area include, to the West is Amaseri town, to the south is Amangwu, and Owutu communities, respectively, etc.1.1.1 Accessibility
The study area, Ozara Okwu is accessible through road network from Abakaliki–Afikpo road, Afikpo–Okigwe road, Amasiri–Edda road, Unwana road, Ndibe and some outcrops are trekable few meters into the bush and others are along river channels. The main access road to Afikpo area is the Okigwe – Afikpo road and Abakaliki – Afikpo road.
1.1.2 Physiography
The map area lies around on elevation of about 170m above the sea level. Sandstone ridges forms the topographic highs of the area. Areas of moderate relief are often characterized by an intermediate condition of erosion between the extremes on area with high relief on one hand where the underlying shales are easily eroded.In Afikpo region also erosion is more pronounced from N-S along the Abakaliki anticlinorium, most generally occurring are planes underline by shales and silt stones, within the hills and ridges are composed of sand stone lithology.
1.1.3 Drainage Pattern
The drainage pattern is systematical flow of water, water surface or underground due to geomorphological feature of the area and it environment. It depends on the soil type, vegetation and relief. The river has a dendritic drainage pattern with tributaries forming trees structure and mainly associated with coastal area and clay siltstone dominated the environment.
1.1.4 Vegetation
Vegetation in Ozara is characterized by trees shrubs with abundant palm trees. Climate is the average condition of a place over a long period of time.
1.1.5 Weather and climate
The climate of Afikpo area is hot and humid with mean annual rainfall of about 152-203cm, which corresponds to its adjacent basin (Anambra basin.). There are two main seasons that dominates the climate in Ozara Ukwu. They are the rainy season and the dry season.The rainy season usually begins minimum temperature towards the end of the rainy season is about 18-210c.While dry season, lasted only from late November to early April.Finally the climate of the studied area is not stable due to seasonal variation.
– The aims are to identify mappable rock units and logging in other to study the lithostratigraphy of Ozara Ukwu and its environs and to describe in details the different lithology that were encountered.
– The objectives are to deduce the geologic history and possibly geologic time sequence of the deposition as well as to produce a geologic map showing detailed description of the structures and lithologies present in the mapped area.
Figure 1: Map showing the location, physiography, drainage pattern of the map area (inset).
Figure 2: Vegetation Map of Nigeria ((Atlas Map of Nigeria)
Figure 3: Rainfall map of the Study Area (Atlas Map of Nigeria). Inset is the location of the Study Area.
Figure 4: Geologic map of the study area Ozara Ukwu.