A report of geologic mapping project of area l, in Gayaza Isingiro District, Western Uganda

Abstract

Geological Field mapping exercise is a compulsory field exercise always conducted at the end of the second year in Gayaza, Isingiro district, Western Uganda for students undertaking Bachelor of Science in Geology and Bachelor of Science in Petroleum Geoscience and Production at Makerere University. The main objective of this field exercise is to acquire skills in geologic mapping through data acquisition, data processing and interpretation of field data equipping students with hands on experience from field preparation to geologic reporting. We had this field excursion from 23rd May to 05th June 2019 with a day of briefing on 16th May, 2019. The methods used during the excursion were: making groups of 5 to 6 students, standardizing pace lengths that makes measurement of structures easy in the field, establishment of stations on out crops, taking GPS readings and measurements of strikes and dips, plunge and trend of structures and taking samples from established locations. After the field work, samples were taken and sorted for further analysis. The area lies on a rugged topography with series of rounded hills, steep gorges with a tropical climate consisting of two wet seasons. The area had no economic minerals that have been discovered though had economic activities like farming, quarrying and cattle keeping. The rock types in the area are of thin arenaceous formations mainly composed of quartzites and thick argillaceous formations consisting of phyllitic shales, terrigenous shale and slates. The rocks were in the order of shales at the bottom, sandstones metamorphosed into quartzites at the top of the hills. The Karagwe-Ankolean system was intruded by granites which with long term weathering formed the arena. The rocks have undergone low grade metamorphism evidenced by foliations, relict beds and some index minerals such as chlorite. The major structures in the area are relict beds, faults, folds and joints exhibiting majorly two trends NW-SE trend and the NE-SW trend, fractures and silica rich veins. The drainage of the area is structurally controlled. From the findings it was concluded that the area forms part of the lower Karagwe-Ankolean system basing on the lithology.