1.1 LOCATION AND ACCESSIBILITY
The study area is located along Afikpo-Okigwe axis and bounded by latitudes 5° 51I
N and 6°03I
N and longitudes 007º51I
E and 8° 06I
E (Fig. 1), and with an area extent of about 74 sqkm (Fig. 1). The study area is bounded on the north by Afikpo, on the south by Eberiba and on the west by Amasiri town.It covers area such as, Anofia Nkanu, Amangbala and Ebom in Ebonyi State, South Eastern Nigeria. Access to the area is through the roughly east-west Afikpo-Okigwe road, which connects the Okposi-Amaseri-Amoso road at Amasiri. On the outskirts of Afikpo town, this road connects with the Northbound Abakaliki road passing through Akpoha and Abomege. The eastern side of the study area is accessible through the Abomege-Ugep road, which passes through the Cross River at Itigidi to Ugep and Calabar towards the southern part of the study area. Other minor roads link the smaller interior villages from these major roads. The major roads are tarred while the minor roads are untarred and may not be accessible during the rainy season.1.2 GEOGRAPHY
1.2.1 CLIMATE
The study area experiences of two seasons, the rainy and dry seasons. There is however, a short break of one to three times, usually referred to as “August break”. The hottest months are usually between October and March.
Rainfall in this area is evenly distributed and is high, about 190 cm per annum, and 95 % of this takes place between the months of April and October (Ibe and Okeke, 1974). The rate of evaporation from the open surface water as estimated by Mirenenko (1966) is 2cm per annum.
Fig. 1: Location and accessibility map showing the drainage system of study area.
The mapped area falls within the zone of 27o
-30o
of annual temperature. The climate of this area is classified as a tropical wet and dry savannah climate.1.2.2 VEGETATION
The vegetation of the area ranges from humid tropical rainforest to savannah, with gradation of one form to the other which can be attributed to the relief patternof the area (Fig. 2). Afikpo area belongs to a forest community known as moist lowland forests and is characterized by forests where the conditions are favourable (Ofomata, 1978). The lithological combination and the climate play a part in the vegetation of the area (Igbozurike, 1975). There are considerable disparity in vegetation between the shaley plains and the sandstone ridges. The ridges are generally covered with sparse vegetation while the plains have luxuriant vegetation. This is because the sandstone ridges are permeable and could not hold sufficient water to support luxuriant vegetation while the lowland plains of mud rocks are impermeable and thus retain water very well for crops.
The streams, river courses and lowland of shale beds have fairly thick vegetation and high trees while hill-tops and other dry areas consisting of siltstones and ferruginized sandstones are marked by savannah vegetation and isolated trees. This indicates that the vegetation is controlled by geological factors such as topography, lithology, relief as well as anthropogenic activities. Deforestation has taken place in certain areas where the land is being used for agriculture, industries and other developmental activities.
1.2.3 THE PEOPLE
Afikpo is the birthplace of several accomplished Nigerian men and women. A notable example is the late Dr. Akanu Ibiam of Uwana, one of the first Igbo medical doctors and former Governor of the Eastern Region. Afikpo is a Mecca of ancient Igbo tradition and ceremonial (now antique) masks which have been carefully preserved by the state tourism board. Several archeological findings support the claim that Afikpo civilization existed as far back as the Neolithic age.
The origin of the people of Afikpo like most of their pre-literate counterparts in African is shrouded in obscurity. However, their oral tradition has tried to throw much light on the matter. Now there appears to be a general agreement among the oral sources collected that the original inhabitants were non-Igbo speaking groups called the EGU, the NKALU and the EBIRI. There was also a legend of the existence of a distinct group called the OHAODU.
Fig. 2: Vegetation map of Nigeria showing the study area (after Igbozurike, 1975)
Afikpo tradition is unanimous that the founder of Ehugbo (Afikpo) was Igbo Omaka, otherwise called Igbo–ukwu Omaka. He migrated from Arochukwu in company with other kinsmen who founded Edda, Amasiri and Akpoha. On arrival, he settled at a place called Oroghoro or Amaozara between Amaobolobo and Amaizu. This migration took place probably in the Mid-17th Century. It might be as a result of warfare for historians always talk of the Ibibio–Aro–Akpa war which took place in the Mid-17th Century. The Aro had invited the Akpa from the Cross River valley. The Akpa who were armed with superior weapons called blunderbusses and better organized, helped the Aro to defeat the Ibibio. During and after the war, a lot of migrations took place. The elders of Ehugbo often refer to the Akpa–Ibibio war during which there were dispersions. But the exact identity of this group, Akpa is not known. It was traditionally believed among all the Afikpo people that Igbo Omaka was a very strong warrior. He came with admixture of Igbo culture. Igbo, the warrior launched a war on the Nkalus and the Egus and other non-Igbo original inhabitants most of whom had to flee as mentioned earlier. The rest were assimilated into Ehugbo society. These later migrants had been settling with his authority and permission.This war, it is further said, was referred to as Nkpu Oroghoro, because all the Igbo groups in Ehugbo (Afikpo) sent their war lord to Oroghoro to help in the war effort. It was in this way that the oldest village-group in Ehugbo (Afikpo) called Nkpoghoro derived its name–Nkpu agbaari Oroghoro.
1.3 LITERATURE REVIEW
Geological study of the Nigerian sedimentary basins began with the establishment of the Geological Survey of Nigeria (GSN) in colonial times. Early research was motivated by –among other things- the potential of the discovery of mineral deposits. Early accounts of the stratigraphy of the Benue were given by Falconer (1911), Wilson and Bain (1928), Tattam (1944), McConnel (1949), Farrington (1952) and Simpson (1955) among others. Oil exploration began in the years following the Second World War and this gave a big thrust to the studies in the area. Shell BP (1957) mapped most of the sedimentary areas of the country and produced geological maps on the scale of 1:250000.
It was after independence and the establishment of the first universities that more detailed studies began to be carried out. Reyment (1965) described a number of lithostratigraphic and biostratigraphic units with giving names to the various formations that are still in use today.
Murat (1972) presented a palaeographic description of the cretaceous and lower tertiary with a mega-tectonic framework. More recent work on the stratigraphy and basin fill of the various depositional basins have been carried by Adeleye and Dessauvagie (1970), Offodile (1976), Kogbe (1982; 1989a; 1989b), Petters (1978), Nwajide (1982), Ojoh (1992), and Riejers (1996) among others.
Along with the more detailed knowledge of the stratigraphy of the Benue trough came theories to account for the evolution of the Benue trough especially within a plate tectonic framework. Authors like King (1959), Grant (1971), Burke, Dessuvagie and Whiteman (1970), Wright (1976), Benkhelil, Guirand, Ponsard and Saugy (1989), and Ojoh (1992) among others proposed theories to account for the evolution of the Benue trough.
The Anambra basin has seen more detailed work in recent times related to it’s having the greatest potential after the Niger delta for oil and gas accumulations. The recent advances in stratigraphy has been applied to the basin by authors like Nwajide and Riejers (1996), Riejers (1996), Obi (2000), Okogbue and Nwajide (2001) Oboh-Ikuenobe, Obi and Jamarillo (2005) and Mode (2002).
1.4 SCOPE OF WORK AND OBJECTIVES OF PRESENT STUDY
SCOPE OF WORK
The scope of work covers the Late Campanian to Early Maastrichtian Intervals, and located within the Afikpo sub-basin. The field work covers the geological mapping, lithologic characteristics, sedimentology, biostratigraphy, and the production of geologic map on a scale of 1:25000.
OBJECTIVES OF PRESENT STUDY
The fundamental objective of this work is to give a detail description of the geology of Ozizza and its environs, which can be used in interpreting and delineating the depositional environments, depositional sequence, biostratigraphy, structural features, hydrogeology, and deposits of economic importance in the area. The main objectives include the following:
1.5 STUDY METHODOLOGY
The methodology employed during the field mapping exercise is the compass and traverse method. The major and minor roads, including foot paths were used to access the exposures. The Global positioning system (G.P.S) was used to establish coordinate location of outcrops on the base map. During the period of the field exercise, G.P.S readings were taken at each location so as to obtain the latitude, longitude and elevation; attitude of beds were made at locations where needed, with the aid of the Brunton compass clinometers. At each outcrop locatiopn, the texture, mineralogy, sedimentary structures and other geologic features were determined. These helped in terms of identification, descriptions and interpretation of the different rock types.
The systematic study of the area was carried out in three phases: preliminary review of literature and visits to outcrops, deskwork and field studies, and laboratory analyses of collected samples.
1.5.1 PRELIMINARY STUDIES:
Reviews of the relevant literature concerning the area of study both on a regional and local scale were consulted to get acquainted with the area. The regional stratigraphic succession and accessibility of the area were depicted in elevation and geologic maps. A reconnaissance exercise was embarked on, featuring outcrop visitation, recording of co -ordinates, getting acquainted with the local traditional authorities and arrangement for accommodation.
1.5.2 FIELD STUDIES:
This phase of the study includes deskwork and field work, the outcrops were visited in early march 2017. It was carried out in the field with the aim of collecting field data. The data were collected through measurements, photographs, notes and outcrop sampling. Lithological sections and sketches of notable features were made. Collected field samples were appropriately packaged and labelled using sample bags, and masking tapes.
1.5.3 LABORATORY ANALYSES: This phase involves the analysis of selected samples collected from the field in the laboratory for the development of appropriate results