The Geology of Amanguwu and Environs
The Main objective of this work is to study the geology and carry out the facies analysis of the Cretaceous Sediments of Afikpo at Ebonyi state and produce a geologic map of the study area. The work was done in the field making observations, taking measurements using the GPS, Compass, hammer etc, and taking down recordings, Laboratory analysis were also carried out on the samples from the field, Bivariate And Univariate analysis were done on the samples. The results from this analysis helped us decipher the facies found in the area which includes; Mudstone facies, Sandstone Facies which include; laminated Sandstone Facies, Biourturbated Sandstone Facies, Massive Sandstone Facies, Meandering River Sandstone Facies and Environments of depositions which includes; possible dominant Marine Environment, Fluvial, Beach Environment. From the study this has pointed out that this area is dominantly a Marine, Beach, and from previous works carried out fluvial Environment. From previous works carried out I agree to the that fact that the area is a Marine, and Fluvial Environment and I want to also decipher from the result of the Bivariate analysis carried out that it is a possible predominantly Beach Environment, and from observations of field structures such as Biogenic structures e.g. skolithos that it is a predominant Marine environment.
CHAPTER ONE (Introduction)
1.1 Background Information
Geology is an applied course that has been designed to enlighten and expose students to the procedures of practical field geologic mapping. This involves the study and practical significances of the study of outcrops on rocks in a study area to deduce important information. Research on the study of sedimentary rocks have shown that sediments, pieces and fragments of sedimentary old and pre-existing rocks have created some features and rock attributes which are especially distinct and useful in the sedimentary terrain. This concept makes up about 80%-90% of mineral products that are being utilized in our day to day living and up building. Product of sedimentary rocks which have been a major commodity which has sustained living economics of major developed or developing nations and detailed study on its further use and maintenance is necessary so as not only to develop new uses but also to preserve products of sedimentary rocks for future generations.Thus the field work at Afikpo provided a better practical understanding of the Geology of the area which involves its Geomorphology, regional/structural Geology, Hydrogeology, Economic Geology, Sedimentary facies of the area.
In the course of this research we would be looking at the facies analysis of the cretaceous sediments of Afikpo, facies deals with the chemical and biological aspects of sedimentary beds of the same geologic age. Sedimentary facies is defined as a mass of rock which can be defined and distinguished from others by its geometry, lithology, sedimentary structures, paleocurrent pattern and fossils. Facies analysis is done to construct a geologic model that describes an ancient sedimentary environment and this agrees with Ly’ells doctrine of uniformitarianism which means that (the presence is the key to the past) i.e. modern equivalences are used as analogs of ancient environment. In industries that exploit earth resources such as fossil fuels, facies analysis is very important in research apart from examination of rock specimens, this kind of analysis may also rely heavily upon the geophysical properties of the rock such as density, radioactive electrical and even magnetic properties of the rocks but for the cause of this research we would be using just examinations of rock specimen, biological and geological structures to analyze our facies.
1.2 OBJECTIVES AND SCOPE OF STUDY
The major objective of this field work is to:
To study the facies of the area using lithological, physical characteristics and laboratory analysis
To create a geologic map that gives a detailed structural and lithological description
1.3 LOCATION AND EXTENT
Afikpo and its environs is in Ebonyi State and is located geographically in the South-eastern part of Nigeria within the co-ordinate of latitude 5053’N and 5055’N, and longitude 7054’E and 7057’N. Afikpo is bounded by Owututu to the South, Abba-Omega to the North, Oso to the West, Nko (Cross River) to the East. Afikpo lies at an elevation of about 170m above sea level.
1.4 PHYSIOGRAPHY OF THE AREA
The primary access was through either the Amasiri-Akaeze road or the Abakiliki-Afikpo express road. Other accesses to the field area mapped are through minor roads and footpaths linking the various towns and communities around the area.
1.4.2 GEOMORPHOLOGY OF THE AREA:
Geomorphologically, the study area is undulating, composed of alternating highlands and lowlands with some of the low lands being occupied by surface water bodies.
The highlands are mainly the ridges and hills which are made up mainly of sandstone lithology, minor siltstones/mudstones and claystones which serve as cementing material that bind the quartz grains. Shales and then some siltstones usually underlie the lower areas. On a regional scale, Afikpo is a trough or sub-basin but in terms of local topography is commonly undulating.
The drainage of the study area is controlled by relief, topography and geology. The drainage pattern of the study area is dendritic (tree-like pattern). Some of the
streams are seasonal due to the fact that they dry up during the dry season and are restored during the rainy season.
Afikpo is in transition between the tropical rain forest and guinea savannah. The field area comprises mostly of perennial trees, grasses, stubs and climbers. Its vegetation is affected by various factors such as:
Topography, and various climatic factors
The valley terrain produces thick, green vegetation even during the dry season due to availability of surface water caused by the shale which does not permit water to percolate deep into the soil, while partially withered grasses are found in the hills.
The prevailing climate is typically tropical, with an average temperature of 250C and average rainfall of about 200cm and 250cm (Offodile, 1992); though the temperature may be higher than 250C during harmattan season. The climate is marked by 2 seasons:
Rainy season (from April to October)