Geological field study report of Albertine graben, Semliki basin, Western Uganda

Abstract

This report gives a detail of fieldwork activities carried out from 12th to 23 June 2017 within the semliki basin in Albertine graben. The fieldwork was carried out in areas of Kichwamba, behind Kisegi hill at the quarry, along seasonal Kisegi River, along Kibuku road cut, Turaco area and Sempaya hot springs. The main objectives of the field work was to study the environment and processes of deposition of sediments in the area and understand physical sedimentological and sequence stratigraphical formations. The specific objectives of the fieldwork were; to identify lithologies in the Semliki basin, to identify and relating structures observed in the basement and in the sediments, to identify different elements of the petroleum system and to identify the facies and depositional environments. Different materials used were to measure, record and store geological data. The manuals provided to each group were used to guide group members in the study process. Most of the activities done were in groups though some of the activities like presentation of results were individual work. We collected vast structural and stratigraphic data that we then analyzed to make conclusions about the petroleum potential of Semliki basin. The study area comprised of fluvial, deltaic and lacustrine sediments. Intensive tectonic activity affected the basin. This led to the formation of different structures with in the basement and sediments that we observed. Examples of these structures include faults, joints, folds, veins and banding. Sedimentary structures observed include cross bedding, unconformities, faults, and mud diapir and deformation bands. Mud diapirs, faults, plunging folds would be good structural seals. The presence of hot springs with in the area indicated the presence of high enough geothermal gradient that is important factor for source rock maturation and expulsion of hydrocarbons. Sedimentology, stratigraphy and tectonics are applied to develop a full understanding of the rocks and the sediments that fill Semliki sedimentary basin and use this information to interpret the geologic history and evaluate the economic importance of these rocks (e.g. Boggs, 1995). We concluded that the study area had a good (working) petroleum system characterized with all the required system components that is source rocks reservoir rocks, seals, traps and migration pathways and there is a chance of discovery of petroleum. So, exploration programs should be continued.