Abstract               

A geologic field mapping was carried out in Kumba and it environ for a periods of 12days. The work was base on the study of rocks in Kumba alongside with lakes, wells, soils and streams. The rocks were studied with the aid of a hand lens to view all the minerals found in them. Streams discharge was measured using area velocity and volume time method.

Depths of well were measured and some physic chemical parameters like temperature, pH , electrical conductivity . At the end of the day water sample were collected from the stream, lakes, and wells including samples of rocks and soils for laboratory analysis.

The field mapping project was a success especially as a wide range of geologic aspects like hydrogeology, engineering geology and physical geology of Kumba and its environs were studied.

CHAPTER ONE

BACKGROUND OF THE STUDY

1.0 Introduction

GEOLOGY 498(GEOLOGICAL FIELD MAPPING) is a map that shows the occurrence of structural features across a region and the distribution of the rock units, types and age relationship. Itequally involves planning, observing or collecting of data in the form of photographs, measurements notes, physical samples (quantitatively as well as qualitatively) and report

This field work was carried out at Kumba by level 400 students from the 3th to the18th of March 2015.On the 3th of March we all guarded at University of Buea Junction at 9am, the bus departed at 10am and arrived Kumba at 12 noon. We were lorging at Jomas Motel for the 15days

The next day our supervisor gave us an overview of what we have to do on the field to better understand our work and to avoid confusion ,he equally show ushow to use equipments on the field such as the PH meter, compass clinometer and GPS.

The mapping of KUMBA was divided in to 4 Locations; Fiango, Kumba Road, KaKe and Lake Barombi, were each of had different localities. Wemapped Kumba in 12days, each location was studied for 3days from 8am to 5 pm and having lunch from 1 pm to 3 pm every day.

On the 13thday we had our rest and packed our things, the next day wecollected watersamples took a bus and departed to Buea. Wethen took the water samples to the Laboratory at EKONA for analysis

1.1 Location and Accessibility

Administratively, Kumba is located in Meme Division, South West region of the Republic of Cameroon found in Central Africa,with a population of 144,268(at the 2005 census )

Geographically, Kumba lies between longitudes 9027II 00E and 9024II 15E and Latitudes 40 39II 45N and 40 38II 00Nand approximately240m above sea level.

Kumba is refer  to as K-town , bounded in the Northwest by Lake Barombi. Most of the roads in Kumba are tarred making transportation very easy but in areas of high secondary vegetation cover, bushes were cleared to facilitate access to study position and various outcrops since we could also use possible means like motor bikes, taxi, and footpath that permitted us to penetrate into these areas.

The map below goes a long way to illustrate the location and accessibility of Kumba and its environs

1.2 Literature Review

According to Jacque Nougier’s, Cameroon belong almost to a vast African Shield covered by sediment or lava flow and is equally marked bythepresence of sedimentary basins like the Douala Basin.

The geology of Cameroon dates as far back as the Precambrian age ;that is about 4billion years ago, The tectonic setting of Cameroon led to the formation of  Metamorphic rocks  found in the basement complex of Cameroon which outcrops in the Ntem complex in the Southern Region of Cameroon, the Nyong series and the Yaoundé series.

These metamorphic rocks own their origin from the tectonic setting of Cameroon. A major fault line called the central Cameroon Share Zone (CCSZ) runs across Cameroon in a NE-SW trending direction. It was the tectonic activities along this fault that triggered the metamorphism of the pre-existing rocks.

Also, the fact that a major shear zone runs across Cameroon in a NE-SW direction gave rise to a chain of volcanoes who owe their magmatic activities to the tectonic setting.

This chain of volcanoes and lakes is known as the Cameroon volcanic Line (CVL) with only one active volcano, the mount Cameroon. It has  Y-shaped and is similar to the Penamboco Fault Line in Brazil and the Benue Trough in Nigeria.

During the south Atlantic drift of Gondwanaland which eventually spitted into Africa and South America, the major rift had tributaries that penetrated into the continents.

One of such smaller rift was the central African Share zone, which in Cameroon is refered to as the Central Cameroon Share Zone (CCSZ).

The central African Share Zone (CASZ) runs from south West Africa to North Africa , precisely Sudan. The development of these rifts are pan African events dating about 6000 million years ago.

During the rift, there was an influx of marine sediments along the coast through the process of transgression. Subsequent deposition of sediments like sandstone and conglomerates into the inland led to the formation of the sedimentary basin we have in Cameroon.

Sedimentary basins in Cameroon are Douala basin, Rio del Rey basin, Kribni Campo, Mamafe basin, Djerem basin, and Garoua basin.

The Douala basin is the largest of all the sedimentary basins in Cameroon. Kumba is situated at the edge of the Douala basin which outcrops around Hill Top. The Douala basin is a gas prond.

J.C Dumort in his postulates says that Rio Del Rey basin is one of Cameroon’s coastal sedimentary basins is a continuation of the Niger Delta in Nigeria. The Douala basin serves as a transition between these formations and those of Gabon to the south.

The Douala basin is separated from the Rio Del Rey basin by the Cameroon Volcanic Line (CVL). To the North and the East, the basin is limited by the African basement. It slopes down westward a few thousand meters into the Gulf of Guinea.

Geophysical data indicates the basement at depths between 3000 to 4000meters and sometimes as much as 7000m. the length of the outcrop reduces southwards. A last outcrop pears in Campo area.

1.3 The Geology of Kumba

Cameroon is found predominantly on a mobile belt (fault line). As a result of tectonic activities within this fault line, an aliment of volcanoes were outcrop along this fault line forming the Cameroon volcanic line (CVL).

The CVL has a NE-SW trendfor about 1600km from the Atlantic island of Palagu across the continental margin through the continent up to Soudan.

Kumba and its environs lie on the Cameroon Volcanic Line (CVL), characterized by crater lakes like Lake Barombi and volcanoes like mount Cameroon being the only active volcanoes and has been dormant for a very long period of time.

Kumba also lies at the edge of the Douala Basin, Therefore the rocks actually originated from deposition of pre-quaternary volcanic rocks and the recent basalts. However, the rocks found at Kumba have experience some degree of tectonism and deformation.

In 1960s, studies have shown that the daily temperatures of Kumba were about 400c which led to the formation of laterites that outcrop nearly the entire area of study.

This is true because temperature increases is one important factor necessary for laterization. . The tectonic setting of the Douala Basin resulted in the metamorphism of granites producing gneisses which outcrops in Mabanda.

1.5 Aim

The main aim of field mapping project is to fulfill the conclusion of a Bachelor Degree in Geology by the University of Buea.

The field mapping project was also aimed at mapping Kumba base on its geology, structure, texture, rock type and its mineralogy.

It also involved the survey of well water, stream discharge, springs and collecting fresh rocks and soil samples.

Our coming in close contact with the natural geologic environments of Kumba and environs, we were able to have a better understanding of the course we have been thought so far, because geology is on the field.

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