Electronic Theses and Dissertations (Masters)

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Browsing Electronic Theses and Dissertations (Masters) by SDG "SDG-15: Life on land"

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    An investigation into high gear and low gear propulsion in human gait and its relation to metatarsal diaphyseal geometric cross-sectional properties
    (University of the Witwatersrand, Johannesburg, 2023-06) Reyneker, Mark Brenden; Carlson, Kristian J.; Zipfel, Bernhard
    This study investigates the relationship between metatarsal bone form, as quantified by cross-sectional geometric properties, and its relationship to high (medial forefoot loading) versus low gear (lateral forefoot loading) push-off during the propulsion phase of the gait cycle. The objective being to assess whether forefoot loading may be variable or whether high gear loading occurs in higher frequencies, as depicted in theoretical foot function models. The study sample (n=53), made up of three broad groups, include Later Stone Age southern Africans, post-industrial individuals from South Africa, and the Jomon of Japan. Metatarsals 1-5 cross-sectional geometric properties (CSA, Ix, Iy, Imin, Imax, Zx, Zy, Zp, Zmin, Zmax) taken from CT scans at 25%, 35%, 50% and 65% metatarsal diaphyseal biomechanical lengths are grouped into high gear (metatarsal 1-2) and low gear (metatarsal 2-5) for comparison. The combined population analysis reveals that the high gear metatarsal diaphysis exhibit significantly higher strength and rigidity driven mainly by the post-industrial individuals from South Africa and the Later Stone Age southern Africans. In contrast, the Jomon of Japan, exhibit no significant differences between high and low gear metatarsals except for CSA, Imax, and Zmax. Furthermore, metatarsal 1 and 5 differ far less in cross-sectional geometric properties in the Jomon of Japan compared to the other populations except for medial-lateral strength (Zy) and torsional and average bending strength (Zp) where metatarsal 5 is significantly higher. The study findings indicate that forefoot loading demonstrates variability during the propulsion phase of gait, while also suggesting a higher frequency of occurrence for high gear push-off. This challenges current theoretical models of foot function that emphasise high gear push-off as typical and normal for striding bipedalism.
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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.
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    Potential Source for the Alluvial Gold Deposit in the Kapoeta Area, Eastern Equatoria State, South Sudan
    (University of the Witwatersrand, Johannesburg, 2023-10) Bali, Francis Khamis Alex; Woldai, Tsehaie; Kinnaird, Judith A.
    This study concentrates on the integrated approach of applying geochemical, and remote sensing data combined with field investigation to understand the source of the alluvial gold deposit in the Kapoeta area. The use of an integrated technique approach proves effective in mapping and outlining areas of potential gold mineralisation in Kapoeta. Kapoeta has been known for its endowment of gold deposits for quite some time. Landsat-8 (OLI) and SRTM-DEM satellite images were employed during this study to map lithological units and highlight areas of hydrothermal alteration and structural trends in Kapoeta to understand the potential source for the widely distributed alluvial gold in the area. The several image-processing techniques employed were effective in mapping the lithological units and outlining the major structural trends in the area. Mapping the hydrothermal alteration zones was challenging because of the overburden that masks most parts of the Neoproterozoic juvenile metavolcano-sedimentary sequences. Secondly, the vegetation cover is another factor affecting the mapping of the lithological units around the Didinga Hills and Dongotona mountains. Structural mapping identified four main trends N-S, NNW-SSE, NW-SE, and NE-SW. The image interpretation, together with geochemical occurrence and anomaly map showing Cu, Co, Ni, and Cr, shows that N-S and NNW-SSE are the potential controls on mineralisation in the area. The whole-rock geochemical data plotted on the TAS discrimination diagrams shows that the rocks analysed are dominantly tholeiitic with minor calc-alkaline units. Trace elements normalised to the primitive mantle show low concentrations of Zr, Hf, Nb and Ta. The REE normalised chondrite values indicates general enrichment of LREE elements relative to HREE with a negative Eu anomaly. On the tectonic discrimination diagrams, the results indicate that the rocks of Greater Kapoeta belong in a marine environment related to a spreading centre, oceanic island, oceanic ridges, and floor. The distribution of Cu, Co, Cr and Ni and their high concentration suggest that these elements are the potential pathfinders for gold in the area. The study concludes the following: Based on the remote sensing, field observations and geochemical data indicates that the gold mineralisation of Kapoeta is orogenic in nature with a strong element of epigenetic characteristics, however, a syngenetic origin cannot be ruled out. The host lithologies may vary from quartz veins to schists, amphibolites, quartzo-feldspathic gneisses, and ultramafics and the marbles related to the N-S, NNS-W-SSE and NW-SE trending shear zones that limit the greenstone belt.
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    Sedimentology and geochronology of the fossil bearing upper member of Malapa site in the Cradle of Humankind (South Africa, Johannesburg)
    (University of the Witwatersrand, Johannesburg, 2023-08) Maphanda, Dakalo Portia; de la Peña, Paloma; Jinnah, Zubair; Makhubela, Vincent
    Malapa is a palaeoanthropological site in the Cradle of Humankind in South Africa. It is known for preserving two partial skeletons of Australopithecus sediba. These skeletons are encased in Pleistocene cave deposits that are subdivided into six sedimentary facies i.e., A-F. There are two pits exposed at the site i.e., the main pit (pit 1) and pit 2. Sedimentary facies A-E are deposits from the main pit, and facies F occurs in both pit 1 and 2. Pit 2 deposits were previously classified as a homogenous deposit of facies F. Recent excavation campaigns carried out in 2019 and 2020 exposed new deposits adjacent to the deposits in pit 2. The purpose of this study was to enhance the geological understanding of the deposits at Malapa by investigating the newly exposed deposits. We found that facies F deposits are not as homogenous as previously thought, based on grain size, textural variation, and general appearance of the deposit. The newly exposed deposits and facies F were collectively called the upper member as they entail the deposits investigated in this study. Facies F and the newly exposed deposits were then targeted for sampling to investigate the petrography of the deposits. The study also investigated the stratigraphic position of the upper member in relation to facies A-F from the main pit by attempting to resolve an age of the deposits. The study utilized a sedimentary analysis approach by combining petrographic descriptions, mainly SEM-EDS and XRF to confirm the existence of multiple facies in the upper member. The results show that the upper member comprises facies B, C, F and a newly defined facies G. Facies G contains more chert and quartz clasts than any facies described in the previous studies. It only has calcite in the form of a micrite matrix supporting chert, quartz, or Mn-Fe-coated grains. Considering that the six facies from previous studies are chronologically well constrained, the age of facies G was also investigated. Two flowstones were used to estimate the maximum age of the clastic sediments. Flowstone 2 was situated between the clastic sediments of facies B, C and F so it represents a maximum age for sediments below it and the minimum age for those above it. Flowstone 2 is the same as the Flowstone 2 sampled by a previous study where it returned a well-constrained age of 2.06 ± 0.021 Ma. Flowstone 3 was determined to be a clast that could have collapsed from the cave roof and was situated in previously unstudied sediments. The sediments were determined to be Facies C deposits close to Pit 1. We attempted to date Flowstone 2 by U-Pb LA-ICP-MS but attained an age of 3.72 ± 0.77 Ma (Pliocene in age), inconsistent with previous dating and unrealistic in the context of the Malapa. Flowstone 3 produced a U-Pb age of 7.50 ± 0.37 Ma (Miocene in age). The U-Pb flowstone ages have large errors. Flowstone 2 has an error of ~21% of the age and flowstone 3 has an error of ~5%. Both flowstone ages have too large an error to be considered useful to constrain the age of the upper member. A second dating approach was then used on the clastic sediments themselves using cosmogenic nuclide burial dating. The method yielded more well-constrained ages of 1.59 ± 0.44 Ma. This is an isochron burial age that suggests that the upper member is much younger than the deposits in the main pit, but the isochron burial age is in agreement with the literature U-Pb ages from the flowstones. This is because 1.59 + 0.44 = 2.03 Ma which coincide with the U-Pb ages of the flowstones in the main pit and pit 2. The age of the samples from facies G have an average age of 1.52 ± 0.088 Ma which makes facies G the youngest in stratigraphy.