Project Abstract

Abstract
The petrographic study of sediments from the rivers Ero, Geregu, and Ajaokuta in Nigeria aimed to understand the mineral composition, texture, and structure of these sediments. Sediments play a crucial role in the environment as they can act as carriers of pollutants and nutrients. In this study, samples were collected from the rivers and analyzed using petrographic techniques to determine their mineralogical composition and characteristics. The results of the study revealed that the sediments from the rivers Ero, Geregu, and Ajaokuta are predominantly composed of quartz, feldspar, and clay minerals. Quartz was found to be the most abundant mineral in all three rivers, indicating a common source for the sediments. The presence of feldspar suggests a granitic source, while the clay minerals indicate weathering processes in the catchment areas of the rivers. The texture of the sediments was found to vary, with some samples showing well-sorted grains while others exhibited poor sorting. The presence of angular grains in some samples suggests limited transportation and deposition processes, while rounded grains indicate longer transport distances. The sediment structures observed included cross-bedding, laminations, and bioturbation, indicating varying depositional environments within the rivers. The petrographic study also identified the presence of heavy minerals such as zircon, rutile, and garnet in the sediments. These heavy minerals are resistant to weathering and can provide insights into the provenance and history of the sediments. The distribution of heavy minerals varied among the rivers, suggesting differences in sediment sources and transport processes. Overall, the petrographic study of sediments from the rivers Ero, Geregu, and Ajaokuta provides valuable information about the mineral composition, texture, and structure of these sediments. Understanding the characteristics of these sediments is essential for assessing their environmental impact, such as pollutant transport and sedimentation processes. Further research could focus on tracing the sources of the sediments and investigating the relationship between sediment properties and environmental factors in the study area.

Project Overview

 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.

1.4     SCOPE OF STUDY

The project work was done in three stages. The first stage entails detailed geologic mapping of the study area. Fourteen soil samples were obtained at an interval of 200m from the field at different locations. And samples were collected from depth of about 20-25cm

The second stage includes the preparation of samples for laboratory analysis (petrographic analysis).

The final stage involves the interpretation and collation of results, and writing up of project.

1.5     SETTLEMENT AND LAND USE                                            

The study area is characterized by linear settlement with sparse population and is occupied by the Ebira people. The rural areas include Ero, Eroko and Geregu, these are located along the river bank of river Niger. Some of the village and towns in the study area are far apart and linked by footpaths and rivers. The land in the study area is mainly used for agricultural purposes, farming and fishing along River Ero being the major occupation in the area. (Fig.2)

Fig. 2: Type of Land use in the study area

1.6     CLIMATE AND VEGETATION

The climatic condition of the study area fall within the tropical climate region where wet and dry season are prevalent. Average annual rainfall is between 1100mm – 1300mm with temperature as high as 36.7ËšC.

The study area occurs within the rainforest belt with ever green vegetation which is characterized by Guinea Savannah type Vegetation and the study area comprises occasionally of stunted trees.

1.7     TOPOGRAPHY AND DRAINAGE

The study area is characterized by hills ridges of basement complex rocks. The drainage system over the areas of the basement complex is usually marked with the proliferation of many small stream channels (Olusiji, 2012). The channels of these smaller streams are dry for many months especially from November to May. The major river in study is river Niger. Others include river Ero and river Adogo, which drains into the river Niger. The drainage pattern of the study is indicated as dentritic, it develops in region underlain by homogenous materials where the subsurface geology have similar resistance to weathering such that there is no apparent control on the flow direction of the tributaries, which later join larger streams or rivers at acute angle (Olusiji, 2012).

1.8     LITERATURE REVIEW

Interest has grown among researchers to understand the mineral potential, depositional history and petrography of many stream sediments in Nigeria in the last few years, particularly in the southern part of Bida basin. Among the previous studies include Braide (1992a), Ojo and Akande (2003, 2009) Obaje et al (2004) Akande et al (2005). In the Northern Bida basin, particularly areas North of Niger River, Adeleye (1974), Braide (1992b), Olaniyan and Olabaniyi (1996), Olugbemiro and Nwajide (1997) examined the morphology of pebbles, grain size distribution, facies distribution and inferred fluvial environment for the sandstone and conglomerate. Notably, published works dealing on the research area are scarce Hence, this study is focused on the petrography of the sediments of River Ero so as to document the mineral composition, petrographic characteristics, provenance, transportational and depositional history of the sediment samples.