This refers to the general nature of the land form of the area. Topography, drainage pattern, vegetation, climate, and superficial deposits are the parameters discussed under the sub-headings below:
Afikpo and environs is generally an undulating alternation of highlands which is bounded by sandstone and lowlands which is bounded by shale. The highlands are mainly the ridges and hills which are mainly made up of sand stone lithology, minor siltstones/mudstones and clay stones which serve as cementing materials that bind the quartz grains together in sandstone. Shale’s and then some siltstones usually underlie the lower areas (the plains)
Hence, on a regional scale, Afikpo is a trough or a sub-basin but in terms of its local topography (relief), it is commonly undulating. The highest elevation from the map is about 450ft while the lowest elevation is 50ft
CLIMATE AND VEGETATION
The climate of Afikpo area is moderately high the area is located within the tropic rain forest and savannah region of the eastern Nigeria. The temperature is moderately high during the day time and very low during night.
The studied area is associated with thick vegetation covered similarly to that of rain forest as part of the south east Nigerian tropical climate condition. This vegetation cover more pronounced in the flood plain where they are more are more nutrient which in soil, some areas where there is less or no nutrient and there by the tree find it difficult to survive.
Drainage is simply the channel or water waves created by the action of running water in which the surface and groundwater of an area is discharged into the sea or the major drainage basin. The major drainage basin in our study area (Afikpo & it’s environs) is cross river on the south south eastern boarder of Afikpo. There are some minor livers (drainage basins) in the study area among which are River Woowoo from Izumgbala which flow towards Ndibe beach, river Inyioka which as well channels their loads and water into the beach (Ndibe beach). In the North-East and South west, the rivers flows directly into cross river.
They do not join cross river directly in the south, south and south East but do so later on their course as they move on. There are some other drainage features in the area among which are the streams located behind Ebonyi Hotels and that located at the base of a hill behind Government college junction.
All the streams located almost everywhere in Afikpo are usually recharged by contact springs which forms wherever the contact of impermeable rocks (i.e. shales) and permeable rocks (i.e. sandstones) intersect the surface.
These streams with some tributaries may inturn flow into the major rivers and the rivers finally flow into Cross River depositing large amounts of micaceous sands. It is important to note that majority of these drainage features are as a result of erosion and therefore only gets lively during rainy season but remains dry during the dry season.
Looking at the drainage pattern of the study area, it is very clear from the rivers on the map of Afikpo and it’s environs and the one observed in the field (opposite Egesco Hotel) that drainage pattern is dominantly dentritic pattern meaning that the tributaries of the rivers normally join the main stream in a tree-branch-like pattern.
Rivers and streams are well distributed within this area (Afikpo area) often flowing down under the influence of gravity from the ridges (higher area) into the plains eroding, transporting and depositing large amount of sandy sediments into Cross-river. Therefore, it is obvious that streams and rivers are responsible for wearing down the higher areas. Cutting erosion channels and hence depositing the eroded sediments into the lower areas.
This action of erosion has destructive impacts on building and constructions such as collapsing of houses and construction whose foundation are unconsolidated thereby uprooted by erosive action. Gullies on roadsides are as a result of erosion particularly on areas where there is no vegetative cover. This erosive action aids the accumulation of sands into cross-river which is in turn dredged for various construction purposes.
Superficial deposits are simply the shallow deposits of sands, muds and clays (mainly kaolin) which is the product of tropical weathering of aluminum-rich oil. In some areas such as Amasiri sandstone ridge there is consolidated superficial deposit. Other superficial deposits are shales which have undergone weathering as was observed at coal deposit (i.e. lignite observed in location 26 along woowoo river (about 20 metres from the river) along Uwana road and coal seam (anthracite) observed along the pathway to Ndibe beach (location 8).
METHODOLOGY AND MATERIALS
The methodology applied during this field mapping and exercise is the compass and transverse method. In this method, both major and minor road cuts including some footpaths were utilized to access the outcrops. The first thing done was to locate ourselves appropriately in the field using the base and geological map (though more topographical). Attitude of beds such as dips and strikes of beds, trends of joints and cross beddings and foreset beds were measured and these gave as the insight of the geological history of the area.
We also logged some interbedded outcrops in some of our location from the base to the top. By logging, it simply means taking the dips, strike and dip amount of each bed of an outcrop. We determine the grain sizes, mineralogy, texture, sorting, sedimentary structures, tectonic structure, biogenic structures and many other features of the outcrop which aids in naming the rocks and which will also help in the interpretation of the palaoenvironment of deposition. We as well collected examples from each location and labeled them properly for some analysis like pebble morphometry, sieve analysis etc. and for future use.
Below are the list of various tools/instrument used for the mapping exercise and their respective uses;
- Hand lens: This was used to view or identify fine particles of the rock. It aids clearer view than ordinary human eyes as some rocks are characterized by very fine particles/mineral contents
- Compass and clinometer: It is used for measurement of bed attitudes (dip direction, dip amount, strikes, trends of faults).
- Geologic hammer and sample bag: These are used for sample collection and storage respectively.
- Field map/Based map: This was used in the field to located oneself in the field.
- Measuring tape: Used for measuring the thickness of beds.
- Field notebook and pen:- Used for recording of information/lectures/field data.
- Masking tape and marker: Used for labeling of samples collected to avoid ambiguity
- Digital camera: used for photographing of outcrops and important geologic features.
- Automatic sieve chaker and set of standard sieves for proper sorting and mass measurement of sands/pebbles
- Vernier caliper:- for measuring pebble morphometry.
- Sensitive weighing balance:- for sample weight measurement in sieve analysis.
- Other materials include: pencil, eraser, metre rule etc.