GEOLOGY OF OZIZZA AND ENVIRONS, EBONYI STATE, NIGERIA

ABSTRACT

Cretaceous sediments outcropped extensively in the Afikpo sedimentary basins. Detailed geological mapping of Ozizza and environs was undertaken in order to give a detail descriptions of the lithological features, stratigraphic relationships and contacts, sedimentary structures, and their paleontological contents. Sieve analysis, hydrological and palynological analyses of selected outcrop samples were carried out in order to reconstruct the depositional history of the sediments in the area and their provenance, assess the age of sediments and establish their paleoenvironments of deposition, and evaluate the hydrocarbon source rock potential and the degree of thermal maturation. Two main lithological units were encountered, which include sandstone and shale. Result from thesieve analysis indicates that the sandstones in the study areawere mostly deposited in a beach and fluvial settings. Physicochemical results from heavy metals analysis indicated significant concentration of sodium (Na) in the water samples. Results from the palynological investigation revealed a Late Campanian to Earliest Maastrichtian for the sediments, with the following index sporomorphs assemblage:Cingulatisporites ornatus, Zlivisporis blanensis, Distaverrusporites simplex, Longapertites marginatus, Constructipollenites ineffectus, Monocolpites marginatus, Echitriporites trianguliformis,, Buttinia andreevi, and Retidiporites magdalenensis. Environmentally significant palynomorphs indicated that the sediments in the study area were depositedin a marginal marine/ nearshore brackishwater environments of deposition, with minor marine influence. Kerogen analysis shows that all the sediments were mostly dominated by phytoclasts followed by opaque debris and AOM, giving rise to mostly type III kerogen, which are generally immature but have potential to generate gas.

CHAPTER ONE:

INTRODUCTION

1.1   LOCATION AND ACCESSIBILITY

The study area is located along Afikpo-Okigwe axis and bounded by latitudes 5° 51^IN and 6°03^IN and longitudes 007º51^IE and 8° 06^I 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 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 27^o-30^o of annual temperature. The climate of this area is classified as a tropical wet and dry savannah