Geological report for the study trip to semiliki basin in the albertine graben

Abstract

This report is a detailed account of the field work which was conducted in the Semliki basin in the Albertine Graben Western Uganda. The field work was carried out in places like Kichwamba, behind Kisegi hill at the quarry, along seasonal Kisegi River, along the Kibuku road cut, Turaco area and Sempaya hot springs. The principal objective of the field work was to study the depositional processes that deposited the young sediments in Semuliki basin and understand physical sedimentological and sequence stratigraphical formations whereas the specific objectives of the field work included;  Identifying lithologies in the Semliki basin,  Identifying and relating structures observed in the basement and in the sediments and establishing the relationship between the structures in the sediments and the basement.  Identifying different elements of the petroleum system and identifying the facies and depositional environments. The climate of the region may be described generally as hot and humid with average monthly temperatures varying between 27°C and 31°C, It is characterised by extremely cold nights. The climate has favoured economic activities like agriculture. Another notable economic activity is stone quarrying. Lithostratigraphic units observed while conducting the field work are; gneisses, granites, sandstones, siltstones, clays, evaporites, conglomerates and travertine. Geological structures encountered in these units included faults, folds, joints, bedding, dikes, veins, trace fossils, mud diapir, concretions, lamination and plane parallel stratificatrion. Description and interpretation of results from geophysical explorations was done within the Semliki basin and interpretation of gravity and magnetics data obtained from this region. The fieldwork allowed better understanding of the stratigraphic relationship between the basement rocks and the young sediments. From the basin’s and facies analysis depositional environment of the sediments of the Kibuku area along the road cut is determined to be fluvial, lacustrine/deltaic and the provenance of these sediments is probably the basement rocks of the Rwenzori mountains because of the similarity in the mineralogy of the pebbles of the basal conglomerates observed to be in contact with the basement. These sediments represent a petroleum play for hydrocarbon accumulations in which necessary elements of valid petroleum system were identified such as potential reservoirs and source rocks, possible seals, traps and migration pathways of hydrocarbon