Fieldwork report of Kibuku area, Semliki basin within Albertine Graben, Ntoroko District, Western Uganda.
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The field study report was conducted from 21th/July to 1st / August, 2019 within the Semliki Basin in Ntoroko district, Western Uganda. This report comprises a detailed compilation of aims, methods and materials, lithology and lithostratigraphy, Basin and facies analysis, structures, Geophysics , discussions, conclusions and recommendations for the geologic and stratigraphic logging project of semiliki basin-Albertine graben-Ntoroko district, western Uganda. The aim of the field study was to enable the students apply the geological, geophysical and other relevant theoretical knowledge acquired during the course of the program to study the environments and process of deposition of sediments in the study area and also understand the physical, sedimentological and sequence stratigraphic formations of the area, which are very important in hydrocarbon exploration. The Semliki basin is generally filled with Middle Miocene to recent age sediments exhibiting a fining upward sequence (characteristic of fluvial systems) as well as sediments of lacustrine and deltaic origin from conglomerates (overlying the basement rock) to sands to silts to clays. The sediments are underlain by possible Jurassic to Early Tertiary age sediments resting unconformably over the basement rocks (granites and granite gneiss). Basin and facies analysis involved the interpretation of the depositional environments, basin architecture, paleo flow directions and petroleum potential of the Semliki basin. The basin was affected by intensive tectonic activity, that led to the formation of vast types of structures. These include faults, joints, and veins among others in the basement rocks. Structures present in the soft sediments include bedding, cross-bedding, laminations, unconformities, mud diapirs, and plunging folds among others. As far as the geophysics of the basin is concerned, Geophysical data ie potential field data of semliki basin and shallow, high resolution (150-200 Hz) seismic data with a vertical resolution of c. 3m from an intra slope salt withdrawal mini basin in the Gulf of Mexico were availed to students for interpretation and these were not obtained by students in the field. The sediments of the Semliki Basin represent a petroleum play for hydrocarbon accumulations as all elements (the source rock, reservoir rock, trap, seal, migration pathways, maturation and timing) were identified in the field. The presence of oil seeps indicates that organic rich source rocks are present. Information from the field visit to Sempaya hot spring indicate the presence of high enough geothermal gradients of over 67°C/km for the maturation and generation of hydrocarbons at shallow depths.