Tectonic evolution of Mui basin and the depositional sequence of the basin sediments
This study was conducted over the Mui Basin which is located in the south eastern parts of Kenya. It focuses on the tectonic evolution and depositional history of the basin. One of the motivating factors for the choice of this basin is the recently discovery of coal deposits reserves of well into millions of metric tons within the basin. In order to maximize on the costs of exploration, exploitation and development of such resources ones’ understanding of the same is crucial. In order to undertake the study of establishing the causes or events that are associated with Mui Basin the author analyzed the orientation trends of both veins and joints measured on the outcrops in the basement rocks of the periphery or/within the basin to establish the deformation forces that operated during their formation. A study to establish the depositional sequence of the Sediments into the basin was also conducted. The geology of Mui Basin can be divided into metamorphosed sediments (meta-sediments) of the Precambrian Mozambique Belt, their intrusive rocks and the sediments of the Mui Basin. Meta-sediments include: biotite gneisses, migmatites, granitoid gneisses and marble, whereas intrusive are either quartzites or pegmatites. The Mui Basin sediments are varied and include: alluvial soils, mudstones, sandstone, clays, shale and or coal or lignite. The study found that Mui Basin was formed as a result of tectonic movements. The Neoproterozoic rocks at the periphery exhibit a general regional structural of north – south trend. The main deformational stress that caused the formation of the basin was that of tensile stress; although both shear and composite stresses played a significant role. The Mui basin sediments are mainly those of autocyclic type which exhibit repetitive patterns of sandstones and mud rocks. Deposition of sediments into the basin appears to have taken place in two different environments since sandstones and mud rocks are known to be deposited in different environments. In its early stages the basin had shallow and seasonal marine/lake waters which lead to the deposition of calcareous sediments found throughout the basin. Evidence of the shallow marine environment is the presence of gypsum and limestone sediments. v It is recommended from the study of Mui sediments – that since there exists large deposits of economic sediments within the basin a comprehensive study should be carried out to ascertain their quantities and quality to allow for private investments. Some of these economic sediments are the lignite/coal deposits, clays, gypsum and limestone/lime clays and marble.