GEOLOGY OF AFIKPO AND ITS ENVIRONS
1.1 Location and Extant
The study area, Afikpo and its environs is located in Ebonyi State, South Eastern Nigeria on latitude 50 530 E and 50 550 E and on longitude 70 550 N and 70 570 N. The study area is accessible by Enugu- Abakiliki expressway and some track roads and footpaths, the study area is located within the lower Benue.
Geomorphologically, the area is composed of an alternation of high and low land with some of these low lands occupied by surface water bodies. Vegetation of the study area is that of the Guinea Savannah and it has tropical rain forest climate with annual rainfall of about 1500mm-2000mm. it is drained by streams, rivers, lakes and springs and has a dendrite drainage pattern.
The area is composed of sediments of the Upper Cretaceous and the Formation encountered is the Ezeaku, which has both shale and sandstone and the Aus-River group which is composed of shale and intercalation of sands. The intrusive activities found in the area show a doleritic intrusion (silt) probably of the initial phase of the rift formation. Its source could be the Oban-massif.
The area is accessible by road and footpaths. The primary access is through either the Abakiliki-Afikpo express road or through the Ameseri-Akaeze road, it is also accessible through cross river from Ndibe beach road. Other access to the study area is made possible through the minor roads linking the various towns and communities around the area. Footpaths and feeders road give accessibility to the study area and its environs.
Fig 1.1 accessibility map of Afikpo and its environs
1.3 Relief and Drainage
The topography of the study area is undulating in its nature with the sandstone units forming the ridges and hills, while the share units forming the lowland. Topographically, the study area exhibits a north-south trending cuesta with a gully intended terrain (Nwajide, 1977) within the low lying terrains are the streams channels that flow through the high relief area drain the study area.
The drainage of the study area is controlled by relief, topography and geology. The drainage pattern of the stydu area is dendritic. Where streams of Okpukpo, ololo, ubaji, ogberehi, ogbuko, nsikpu, Iyiechiamachara, streams ran through the heterogonous rocks joining almost at right angles to each other forming a tree like structure which later empty into the Iyieke Lake at Ndibe. Some of the streams are seasonal because they dry up during the dry season only to rejuvenate during the rainy season. The stream flow gradually with iyiechiamachara flowing at 0.46m/sec and Nsikpo stream is 235 Azimuth, which is mainly towards Iyieke Lake.
Fig 1.2 Drainage map of the study area
1.4 Objective of the Study
The basic objective of this field work is to give a detailed description of the geology of Afikpo and its environs, which can be used in interpreting and delineating the geologic history of the depositional sequence, structural geologic features, environmental hazards and important economic deposits in the study area.
This covers the aspect of lithology, stratigraphy, hydrogeology, geomorphology, environmental hazards, production of area base map and geologic map, structural geology, evaluation of paleontological data from sediments collected, sieve analysis of samples collected from study area.
1.6 Geomorphology and physiology
The terrains of the study area are not a flat terrain rather an alternation of high and low land terrain. It is mostly succession of hills and valleys. There is cultivation on the hills while surface water bodies occupy most of the valley the hill is strip steep with sudden drop to the valley below.
1.7 Vegetation of the Study Area
The vegetative aspect of the study area comprises mostly perennial trees, grass, stubs and climbers. The vegetation is influenced by human activities, annual rainfall, topography and other climatic factors. In the dry season, the grass withers and the shrubs turns yellowish while the vegetation in the valley still retains its greenish colour due to the shaley soil in the area which does not permit water to percolate deep into the soil, hence availability of interrupted by human activities especially in the valley low land.
The valley terrain mostly causes thick vegetation due to the availability of surface water caused by the impermeable nature of shale. While in the raining season, partially withered grasses are found in the hills with occasional occurrences of shrubs and trees and the valley mostly contains denser vegetation. Vegetation is mostly Guinea Savannah type due to extensive deforestation.
1.8 Methodology and Equipment and Their Importance
The various equipment, geological mapping techniques and descriptive analysis were used the descriptive analysis were used and the laboratory analysis yet to be used in order to achieve the aims and objectives of this field work. The equipment used include; base map, hand lens compass clinometers, sample bag, global positioning system (GPS),camera, geologic hammer, ranging pole, measuring tape, field note, pen, ruler, pencil, masking tape, mathematical set and other drawing equipment.
Base Map: It is very important. It can be regarded as the first aid to every field trip in field mapping in geology. The base map shows the outcrop and the direction of a place under consideration or mapping.
Compass: It is used to measure the attitude of the outcrops; it enables the trends of fault planner and through crossbeds to be measure.
Measuring Tape and Meter Rule: it is used to measure the thickness of a bed during logging.
Hand Lens: it is used for magnification.
Field Notebook: for recording information.
Sample Bag: for collection of rock samples for analysis in the laboratory.
Geological Hammer: it is mostly used to extract samples from the rocks.
Camera: for taking photography (image) of anoutcrop.
Pen and Pencil: pen for recording information while the pencil for sketching or drainage outcrop.
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