The Lithostratigraphy and Basin Analysis of the Kibuku area in Semliki Basin, Ntoroko District , Western Uganda

Abstract

This report is a complete record of the field work and field excursion that was conducted from 10th - 23rd June 2018 at Kibuku, around and within the Semliki Basin in Ntoroko district, Western Uganda. The report is made up of a seven-fold dissection of chapters that give it a detailed account of the objectives, materials and methods, lithology and stratigraphy, basin and facies analysis, structures and Geophysics of the Semliki basin which altogether where useful in the deduction of the petroleum potential of the semliki basin. Outcrop studies near Kichwamba about the basement showed a highly metamorphosed and complex assemblage of volcanic, intrusive, igneous and metamorphic rock types majorly granitic gneisses and amphibolites. The area was marked by distinct structural features in the basement which included folds, faults and zone of intensive fracturing comprising different sets of joints. Tensional forces were responsible for the formation of most of the features such as the Semliki basin, though with the presence of the positive flowers structure such as in the sedimentary section of former Turaco sites in the Graben indicates that compressional forces also play a key role regional deformation of the area. Synthesis studies of the evolution of the Albertine Graben suggest that the Albertine Graben basin is a tertiary intra-continental rift basin that developed on the Precambrian orogenic belt of the African Craton. The sediment sequence within the Kibuku study area comprised sands, clays and siltstone ranging from tertiary to recent in age representing a prolonged and nearly continuous phase of cyclic sedimentation in the biggest part of the basin, considering that the source of such sediments were from the basement rocks at higher altitudes. The prominent cyclic pattern of clays and sands in the study area reflected changing depositional environments whereby sands were probably deposited by high energy water in the fluvial system and finer sediment such as clays were deposited with decrease in energy in the lacustrine system. The interpretation of gravity data helped to understand the crustal thickness variation while magnetic data enabled the mapping of basement depth, composition and the presence of intra sedimentary volcanic bodies. Integration of the gravity and magnetic interpretation suggested that the Northern part of the Semliki basin consisted of many faults with many structural trends. In summary I would recommend that further exploration works should be conducted on the basin for there is high potential for the existence of an active petroleum system. This is because all the elements and processes of the petroleum system exist in the basin