Abstract

Field Geology 2 was undertaken by level 300 students of the Department of Geology at the University of Buea in Penja in the Njombe-Penja subdivision of the Littoral Region of Cameroon. The objectives of this field trip was for students to be able to understand the processes that led to the formation of metamorphic rocks, be able to map geologic features on the field, interpret geologic maps, collect samples and be able to describe them.

The study involved the geologic field mapping of all the geologic features on the outcrop including the structures, petrography of the rocks, measurement of planer features using a compass clinometer, taking the coordinates of the outcrop using a geographic positioning system (GPS) build in a mobile phone, taking pictures of the outcrop, rock description and names were first given at the outcrop.

There, we described two types of metamorphic rocks (Amphibolite and biotite gneiss) and a vein of pegmatite an igneous rock which intruded the metamorphic rocks. The metamorphic rocks were foliated, showed fractures, faults and banding. The dominant type of metamorphism that led to the formation of these metamorphic rocks is regional metamorphism, with the main agent being pressure alongside temperature, differential stress and some chemically active fluids. The metamorphism occurred at very high pressures and temperatures. The type of metamorphism is also referred to as burial metamorphism.

CHAPTER ONE

INTRODUCTION/GENERALITY

1.1 Introduction

The field geologic trip to Penja was a one-day fieldtrip which took place on the 06of June 2018. The fieldtrip was aimed at providing the students with a field experience of what they have been studying in the classroom. The field study was based on metamorphic rocks as we visited the metamorphic terrain at Penja which is named the “Arab construction quarry” in the Njombe-Penja Subdivision.

This quarry is made up mainly of metamorphic rocks and a vein of pegmatite. The rocks at this quarry are typical of the type of metamorphism called regional metamorphism with the dominant agent of metamorphism being pressure, alongside with temperature and differential stress which makes the rocks foliated. Therefore, the types of metamorphic rocks found at the Njombe-Penja Arab construction are dominantly foliated metamorphic rocks and are of the Pan-Africandomain.

1.2 Definition Of The Course

The course GLY318 is titled “Field Geology 2”. It is geology as practiced by direct observations at the field. The course deals with rock analysis on the field at macroscopic scale and at the level of the outcrop.

The course deals with the petrography and petrology of the metamorphic rocks. Petrography deals with the description of rocks, their color, texture and the minerals that constitute the rocks.  Petrology deals with the origin, structure and composition of   the   rocks.   Lastly, we also looked at geologic map analysis wherein we learned how to calculate the dip values of planar structures on the map, draw contours and cross-section.

1.3 Background Of The course

The course Field Geology 2 was based on geologic field mapping. This was to prepare the students beforehand on how to identify metamorphic rocks at the field and how to map geologic features. A field trip was carried out to enable the students observe, map and collect data from the field; the data was collected in the form of photographs, measurements, notes and physical samples. At the end of the course a report is written by the students based on all the field observations.

1.4 Aims And Objectives Of The course

1.4.1 Aims

It is a field geology practical course to enable students see on the field what was taught in class and in the laboratory. This is done through the following;

1. To expose the students to outcrops as they are on the field.
2. To allow the students observe and describe the outcrop.
3. To enable the students’ carryout measurements of planar and linear structures on the field.

1.4.2 Objectives

The objectives of this course include;

Students should be able to understand the processes that lead to the formation of metamorphic rocks.

1. Be able to map geologic features on the field in order to better explain subsurface processes.
2. Be able to interpret geological maps.
3. Students should be able to describe geologic features at the outcrop.
4. Students are expected to collect samples and be able to give a good petrographic description of the rocks.