A report on the geologic and stratigraphic logging project of Semiliki Basin-Albertine Graben In Ntoroko District Western Uganda from 02th January 2022 to 10th January 2022

Abstract

The Semliki basin in the western Ugandan district of Ntoroko was the site of the geologic and stratigraphic logging project. The Semliki basin is situated in the western arm of the Albertine graben's core area. It is a pull-apart basin created when the active rifting-produced Albertine graben underwent trans-tensional strike-slip deformation under the supervision of pre-existing NE-SW normal faults that form grabens. The field study lasted for 8 days from 3/01/2022 to 10/01/2022The primary objective of the field research was to gain practical experience in gathering and interpreting stratigraphic, petrographic, sedimentologic, and structural data, all of which are crucial for hydrocarbon exploration. A geologic hammer, grain size scale, Jacob stick, handheld GPS, notebook, and geologic compass were a few of the tools utilized during the investigation. The methods involved desk Study conducted at camp, fieldwork, sedimentary logging exercise, data collection, discussions, analysis, and interpretation. Sediments from the Middle Miocene to Recent Epoch cover the Semliki basin. These layers show a fining upward sequence and may date from the Jurassic to Early Tertiary. These sediments rest unevenly on the basement rocks. The seven formations (in decreasing order of age) that make up the stratigraphic sequence visible in the basin are the Kisegi, Kasande, Kakara, Oluka, Nyaburogo, Nyakabingo, and Nyabusosi formations. Two lithofacies were found, each of which represents a distinct depositional environment (fluvial, deltaic, and lacustrine). Clay with some consolidation, gypsum crystals, and plant debris give Lithofacies 1 its reddish brown appearance. Massive reddish-brown, coarse to medium quartz sand, grey, dark brown, and army green clays, along with medium quartz sands, plant debris, and grey to white silt make up Lithofacies 2. The basin is affected by intensive tectonic activity, that led to the formation of vast types of structures that include faults, joints, bedding, cross-bedding, laminations, unconformities, mud diapirs, and plunging folds among others. Geophysical data of semliki basin and shallow, high resolution (150-200 Hz) seismic data from an intraslope salt withdrawal mini-basin in the Gulf of Mexico were availed for interpretation. This data was later analyzed by software such as Oasis montaj, sedilog, Google earth Pro and Teclog64. The sediments of the Semliki Basin represent a petroleum play for hydrocarbon accumulations as all elements of a petroleum system were identified in the field. The presence of oil seeps in kibuku indicates that organic-rich source rocks are present, an indicator of an active system and thus great petroleum potential. Information from the field visit to sempaya hot spring indicates the presence of high enough geothermal gradients of over 67°C/km for the maturation and generation of hydrocarbons at shallow depths