Electronic Theses and Dissertations (Masters)

Permanent URI for this collectionhttps://hdl.handle.net/10539/38012

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Near-surface geophysical investigation of the Far Western Limb of the Bushveld Complex, South Africa
(University of the Witwatersrand, Johannesburg, 2023-10) Nadan, Thiashen; Scheiber-Enslin, Stephanie; Manzi, Musa
Platinum Group Elements (PGE’s) and chromium are the main economic minerals that are found within the Bushveld Complex. In particular, the Far Western Limb of the Bushveld Complex has not been completely explored, as it is overlain by a thick Quaternary sedimentary deposit which masks the contacts between the different underlying lithological units. Chromium outcrops within the Far Western Limb have already been identified and mined. The study aims to assess the feasibility of extended geophysical surveys which will further identify the shallow subsurface lithologies and evaluate the future mining potential in the area. Results of this study show that the quaternary cover is approximately eighty meters thick, implying a shallow bedrock within the Far Western Limb. This was used to delineate a contact between the Transvaal Supergroup and the Rustenburg Layered Suite that was lost beneath the sedimentary cover. This shows that shallow geophysical investigations and drilling can prove useful in delineating the lithologies hosting the chromium ores.
The tectonic evolution of the Bredasdorp Basin and its implications for oil and gas formation
(University of the Witwatersrand, Johannesburg, 2023-10) Tau, Rethabile; Enslin, Stephanie; Manzi, Musa; Saffou, Eric
The Bredasdorp Basin is an offshore rift basin located in the southernmost tip of Africa, within the larger Outeniqua Basin. Previous studies have indicated the presence of hydrocarbons, as well as structures or evidence that allude to the presence of hydrocarbons, where the basin has not yet been extensively drilled or explored. In this study, seismic attributes applied to high resolution pre-stack time migrated 3D seismic data are analyzed, in conjunction with well logs, specifically the gamma ray logs. By employing these methods, the study aims to delineate the presence of hydrocarbons and their migration, as well as deduce the evolution of the basin based on the structures observed. Using artificial neural network (ANN) to predict the lithologies and analyzing the patterns in the gamma ray logs, the stratigraphic results show that the basin begins with a marine dominated environment from the Valanginian age to Aptian age. From the Aptian to Albian age, there are consistent changes in sea level and sedimentation, caused by thermal sag and uplift. Past the Albian age to present age, the deposition environment is dominated by sandstones and coarse sediments. This is due to the evolving basin moving from a distal to a proximal environment of deposition. Using seismic attributes such as envelope attribute, edge detection and variance attribute, structures such as paleo pockmarks and fluid escape structures are identified. These identified paleo pockmarks have diameters ranging from 400m to 900m. In addition to these structures, erosive features were observed which could be classified as submarine channels or slump structures, with the dominating channel having depths of up to 1585 m. Using variance and ant-tracking, the fault structures observed of the study areas revealed two dominating phases of rifting. The first phase has horsts and grabens bounded by normal faults trending E-W, with implications that the rifting propagated N-S in this phase of rifting. This phase of rifting ends during the Aptian age. The next phase of rifting begins during the Santonian age, with the fault bound horsts and grabens trending N-S, which indicate an E-W rifting direction.