PETROGRAPHY STUDY OF SEDIMENTS OF RIVER ERO, GEREGU – AJAOKUTA, NIGERIA

CHAPTER ONE: INTRODUCTION

1.1     GENERAL STATEMENT 

The study area is located in and around the Ajaokuta steel complex which is steel manufacturing complex, commissioned by the Federal Government of Nigeria in the 1980s. The company was situated in Ajaokuta so that it will be close to the source of Iron mined from the Itakpe iron formation.

The study site is part of the channel of River Ero in Geregu, a town in Ajaokuta area of Kogi State of Nigeria. Adiotomre, et al (2014) described the channel of River Ero to be over 10km long. River Ero trends NE-SW of Nigeria, and its characterized as a seasonal river that is recharged by rainwater because of the poor contribution of the groundwater in the area. In the Ajaokuta area the recharge from groundwater is not adequate because of the geographic locations. As a result River Ero is dry for most period of the dry season when the contributory tributary streams/rivers are dried up.

Petrography is an aspect of petrology that focuses on detailed description of the mineralogy and textural characteristics of rocks. The combination of petrography and geochemistry data of sedimentary rocks can reveal the nature of source region, the tectonic setting of sedimentary basins (Dickson and Suczek, 1979; McLennan et al, 1993). Tortosa et al, (1991) used the frequency of different types of quartz grains to infer the type of source rocks. Thus simple petrography of the different quartz consistent can be utilized for this purpose (Folk, 1974; Blatt et al, 1980; Asiedu et al, 2000).     

Petrological study of sedimentary rock tends to describe the mineralogical properties of the different types of sedimentary rocks as revealed by petrographic microscopy. Geochemical technique and sedimentary structures that characterized sedimentary rocks and helps to infer the dispositional origin of the rocks. Petrographic study is very necessary to unravel the characteristics of sandstone such as mineralogical constituent, cementation and effect of pressure solution (Blatt, 1967; Pettijohn, 1975).

1. 1GEOGRAPHICAL LOCATION AND ACCESSIBILITY

The study area falls within Latitude N07˚31ʹ and N07˚38ʹ and Longitude E006˚33ʹ and E006˚43ʹ on the Lokoja topographic sheet 247NW, it forms part of the Southern Bida Basin. The study area is linked with good road network. There are minor roads and footpaths within the study area which provide access to River Ero. (Fig. 1)

Fig. 1: Map of study area showing location and accessibility

Inset: Geologic map of Nigeria after (Kogbe, 1976).

1.3     AIM AND OBJECTIVES

The aim of this project is to study the petrography of sediments of River Ero, in Geregu, Kogi state.

The objectives are:

• To establish the mineral components of the river sediments.
• Petrographic characteristics of the sediment.
• To determine the provenance of the sediments.
• To determine the transportational and depositional history of the sediments.