Geological mapping project of Igayaza in Isingiro district, South Western Uganda

Abstract

This geologic mapping exercise was carried out in Igayaza located in Isingiro district in south western part of Uganda. The area mapped is within the Karagwe Ankolean system of rocks which stratigraphically overly the Basement complex rocks. The Karagwe-Ankolean (K-A) system (1400-950Ma) in Uganda is the northern most extension of the Kibaran mobile belt. The sediments of this system occupy a continuous area in southern and central Kabale, southern Mbarara, Bushenyi, Isingiro, Rakai and south eastern Masaka districts. The Buhweju plateau and surrounding hills in Bushenyi district belong to this system as well. This field work was majorly aimed at imparting the skill required to carry out a geologic mapping exercise besides other aims such as familiarizing with field conditions and equipment, collection and interpretation of data among others. The area to be mapped was gridded and we exclusively mapped area A. Therefore, this report contains majorly data obtained within this region which includes the rock types, structures present, economic potential, stratigraphy, metamorphism of the area as well as the regional synthesis using the data obtained by other groups as well. In the area A mapped the major rock types observed include Quartzite, ferruginous shales, Phyllitic shale, Granite, phyllites and conglomerates. Mudstones and slates were also observed in other areas within the region that were out of the area A. All these rocks, being in a region greatly affected by various stress and deformation events such as faulting and folding possessed a number of structures such as quartz veins, boudins, foliation, lamination and mud cracks, joints, beds and folds and folds most of which trended in the NW-SE direction, the major regional trend and a few in the NE-SW direction, the cross-fold trend. Some of these structures not only existed in a macro but also in a micro scale as will be shown in the petrographic analysis. Economic activities in the area included quarrying of majorly quartzite and mining of sand for the construction industry. Agriculture through growing of majorly Bananas in the valleys and the arena and rearing of livestock was also carried out.