Electronic Theses and Dissertations (Masters)
Permanent URI for this collectionhttps://hdl.handle.net/10539/38012
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Item The Stratigraphy of the New Tuli Basin Fossil Sites in Zimbabwe(University of the Witwatersrand, Johannesburg, 2024-09) Zondo, Michel; Choiniere, Jonah; Broderick, Timothy; Munyikwa, DarlingtonThis thesis investigated new fossil-bearing outcrops of the Mpandi Formation of Zimbabwe, exposed at Sentinel Ranch in the Tuli Basin, at sites named “Wedding Hill “and “Pimwe Hill”. The Mpandi Formation exposures at Sentinel Ranch reveal strata that were deposited in fluvial environments that occasionally experienced flooding in otherwise usually dry and hot climatic conditions. These fluvial systems deposited facies that are mostly dominated by fine sediments and their facies have similarities with those found in the main Karoo Basin of South Africa. The use of borehole data helped establish the thickness of the Mpandi Formation and the explorable portion of the formation was estimated to be around 54 metres. Detrital zircons collected from main Sentinel outcrops were used to estimate the maximum depositional age of the sediments using inductively coupled plasma mass spectrometer (LA-ICPMS) methods. Although sparse, the youngest zircons in these samples yielded ages of 199.2 ± 5.1 Ma and 200.8 ± 5.8 Ma, with error bars suggesting maximum depositional ages in the earliest Jurassic or possibly the latest Triassic. A bonebed at the Wedding Hill site produced many postcranial bones of sauropodomorphs, including the articulated leg of a very large individual sauropodomorph, and the first theropod bones recorded from the Mpandi Formation at Sentinel. The discoveries improve our knowledge of the fauna diversity of the Mpandi Formation, permitting more accurate biostratigraphic correlation and enhancing our understanding of the Triassic- Jurassic interval.Item Taphonomy and palaeoecology of a monospecific microvertebrate bonebed: behavioural implications for the late Permian (Lopingian) parareptiles(University of the Witwatersrand, Johannesburg, 2024-06) Mukwevho, Lutendo; Choiniere, Jonah; Smith, RogerSociality in the vertebrate fossil record is a dynamic and fast-expanding area of research. Natural history observations of living animals are crucial for understanding and categorizing sociality, but these observations are not feasible for extinct species. Monotaxic bonebeds provide unique opportunities to conceptualize the social behaviours of these extinct animals. An unusual bonebed (SAM-PK-K11289) discovered in the uppermost Permian strata of the Balfour Formation, Karoo Supergroup, in the Eastern Cape presents a window into the sociality of Late Permian reptiles. The use of propagation phase-contrast synchrotron X-ray microcomputed tomography permitted the 3D reconstruction of skeletal elements in SAMPK-K11289, allowing the taxonomic identification of the individuals in the bonebed as most likely belonging to Owenetta. This is the largest aggregation of Owenetta individuals known to date, with a minimum number of 31, which are all very similar in body size. The ontogenetic profile of SAM-PK-K11289 was interpreted by analysing the size distribution of duplicate elements and by making comparisons with other Owenetta and procolophonid specimens. The specimens in the bonebed are all osteologically immature, indicating that they are juveniles. The bonebed occurs in a pedogenically modified ripple cross-laminated siltstone suggesting that a low-energy fluvial sedimentation likely contributed to the modification, disturbance and disarticulation of elements before the bonebed was buried at or very close to the death site. This bonebed provides novel information that directly challenges the popular belief that reptiles and their ancestors are non-social or asocial. Considering the overall circumstances of the bonebed, I hypothesize that Owenetta rubidgei juveniles were socially gregarious and this behaviour may have been induced or influenced by environmental changes during the early extinction phase of the end Permian mass extinction in the Karoo Basin.Item The Taxonomy and Phylogeny of Varanopidae from the Middle Permian of outh Africa(University of the Witwatersrand, Johannesburg, 2024-08) Sibiya, Zoleka; Rubidge, Bruce; Benoit, JulienVaranopidae are the only pelycosaur-grade tetrapods from the Abrahamskraal Formation of the Beaufort Group. Although four varanopid species are described from the middle Permian of South Africa (SA), their validity has been questionable. Moreover, Ford and Benson recently proposed that varanopids belong to the Diapsida rather than Synapsida. Given this taxonomic and phylogenetic turmoil, this study i) describes two newly discovered and well-preserved varanopid specimens from the middle Permian of SA using CT scanning and ii) re-assesses the validity of the four species from the Karoo Basin in the light of new data from these specimens. The phylogeny of the group is addressed by updating two pre-existing cladistics matrices. The two new specimens exhibit a mosaic of features that overlap the diagnoses of several species of SA varanopids. In addition, some diagnostic traits of the four SA varanopid genera and species are found to be variable across ontogeny. For instance, dorsal osteoderms and the extent of ornamentation on the angular bone co-vary with size. It is therefore proposed that all varanopid specimens currently described from the middle Permian of South Africa belong to a single valid species, Heleosaurus scholtzi, with differences between specimens being accounted for by ontogenetic changes. The phylogenetic analysis supports Ford and Benson’s hypothesis but contra the prediction of this hypothesis, no differences in cranial fenestration during ontogeny are observed. Morphological characters preserved in the manus of the newly discovered specimen BP/1/8499 suggest that Heleosaurus was arboreal.Item Machine Learning Algorithms-Based Classification of Lithology using Geophysical Logs: ICDP DSeis Project Boreholes, South Africa(University of the Witwatersrand, Johannesburg, 2024-09) Atita, Obehi Chapet; Durrheim, Raymond; Saffou, EricOne of the most significant geosciences tasks is the accurate classification of lithologies for metal and mineral resources exploration, characterization of oil/gas reservoir(s), and the planning and management of mining operations. With the availability of abundant, huge and multidimensional datasets, machine learning-based data-driven methods have been widely adopted to assist in solving geoscientific problems such as the efficient evaluation and interpretation of large datasets. The adoption of machine learning-based methods aims to improve lithological identification accuracy and extract information required for accurate and objective decision-making with respect to activities such as exploration, drilling, mine planning and production. Practically, this helps to reduce working time and operating costs. We aim to evaluate the feasibility of machine learning-based algorithms application to geophysical log data for the automated classification of lithologies based on the stratigraphic unit at the formation level for the purpose of distinguishing and correlating the quartzites between boreholes, and mapping key radioactive zones within the mining horizon. This study implemented four different machine learning algorithms: gradient boosting decision trees, random forest, support vector machine, and K-means clustering models. Analyzed features and labelled datasets are multivariate downhole geophysical and lithology logs from the two ICDP DSeis project boreholes drilled in the Klerksdorp gold field, respectively. To mitigate misclassification error and avoid model overfitting/underfitting, the optimal combination sets and optimal values for each implemented supervised model’s hyperparameters were obtained using the Grid search and 10-fold cross-validation optimization methods. The input dataset was randomly split automatedly into training and testing subsets that made up 80% and 20% of the original dataset, respectively. The models were trained and cross-validated using the training subset, and their performances were assessed using the testing subset. The classification performance of each model was evaluated using F1 scores and visualized using confusion matrices. The best supervised classification model for our study area was selected based on the testing subset F1 scores and computational cost of training models. The testing subset results shows that Random Forest and Support Vector Machine classifier models performed much better relative to the Gradient Boosting Decision Trees classifier model, with F1 scores over 0.80 in borehole A and B. In borehole A and B, Random Forest classifier has the least computational training time of about 14- and 6- hours, respectively. The feature importance results demonstrate that the logging feature P-wave velocity (Vp) is the highest predicting feature to the lithology classification in both boreholes. We find that the quartzite classes at different stratigraphic positions in each borehole are similar and they are correlated between the DSeis boreholes. The K-means clustering revealed three clusters in this study area and effectively map the radioactive zones. This study illustrates that geophysical log data and machine learning-based algorithms can improve the task of data analysis in the geosciences with accurate, reproducible and automated prediction of lithologies, correlation and mapping of radioactive zones in gold mine. This study outputs can serve as quality control measures for future similar studies both in the academic and industry. We identified that availability of large data is the major factor to high accuracy performance of machine learning-based algorithms for classification problems.Item Accessory REE mineralization of the Nokeng fluorite deposit as distal facies of the adjacent Vergenoeg pipe, Bushveld Complex, South Africa(University of the Witwatersrand, Johannesburg, 2024-10) Makhema, Relebohile Edward; Yudovskaya, Marina; Madlakana, NonkuseloThe Nokeng Plattekop deposit forms part of the Paleoproterozoic Bushveld Complex and it is located near Rust de Winter, approximately 80 km northeast of Pretoria. This deposit belongs to the Vergenoeg Igneous Complex, which is associated with a violent gas-vapour-rich rhyolitic eruption. The complex comprises the Vergenoeg discordant breccia pipe and a pyroclastic rock suite. Within the breccia pipe and associated pyroclastic rocks, rare earth element (REE) mineralization is observed in minerals like allanite, apatite, bastnasite, monazite, and xenotime. The Plattekop fluorite deposit, which lies 1000 m south of the breccia pipe, is postulated to represent spill-over remnants of the Vergenoeg volcanic edifice. This study performed a comprehensive petrographic and geochemical analysis of ore and pyroclastic breccia of the Nokeng Plattekop deposit, utilizing various analytical techniques, including optical microscopy, XRF, ICP-MS, and SEM. The aim is to characterise the style of accessory REE mineralization at Nokeng as a provisional distal facies of the Vergenoeg volcanic field. The findings of this study suggest that the Nokeng Plattekop deposit comprises a hematite-fluorite unit overlying an ignimbrite unit. Hematite-fluorite ores of the upper unit resemble the Vergenoeg ore, exhibiting elevated CaO concentrations and reduced SiO2 content attributed to high fluorite and hematite proportions. Conversely, the ignimbrite unit displays reduced CaO and elevated SiO2 concentrations, corresponding to lower fluorite content and higher rhyolitic lava fragments. The basal ignimbrite is proposed to have formed during the early stages of rhyolitic volcanism, while Nokeng and Vergenoeg ores formed during later stages dominated by Ca- and F-rich ferruginous magma. Petrographic evidence suggests hematite pseudomorphs after magnetite, indicating mineral assemblage evolution. REE mineralization in the Plattekop fluorite deposit is represented by bastnasite, monazite and xenotime, mostly associated with quartz, goethite, aegirine, hematite and fluorite. The highest REE + Y content (~ 5 890 ppm) is associated with Plattekop hematite-fluorite ores. Comparative analysis of REE distribution patterns suggests similar styles of mineralization between Vergenoeg and Nokeng, indicating both deposits as potential sources of REEs as by-product.Item Finite Element Analysis of Dinocephalian Skulls to Address Head-Butting Behaviour in Early Therapsids(University of the Witwatersrand, Johannesburg, 2024-08) Bolton, Andrew; Benoit, Julien; Mangera, TaahirahThe origin of complex social behaviour in the mammalian lineage has been a long-standing enigma. Behaviours do not leave a rich fossil record; however, adaptations to highly specialised complex behaviour can be traced back in some lineages, such as the dinocephalians. Dinocephalians dominated carnivorous and herbivorous niches of terrestrial ecosystems in the Middle Permian (~273-259 million years ago). Species within this clade often have skulls with considerable pachyostosis (overly thickened bones) and cranial ornamentation (horns and bosses). This morphology has been interpreted as evidence for head-butting, but the evidence is circumstantial at best. For this project, I used three-dimensional models of the skulls of four dinocephalians and two outgroups to simulate and investigate the capabilities of these skulls to withstand different magnitudes of head-butting and flank-butting impacts with finite element analyses. Palaeopathological analyses vindicated the accuracy of FEA data, which indicates that dinocephalian skulls modelled here arguably reflect biological truth. As head-butting is a complex social behaviour, this would strongly suggest the presence of dominance hierarchies, territoriality, and gregariousness. This represents the earliest robust evidence of complex social behaviour in tetrapods, preceding all known examples of social interactions in dinosaurs and mammals by hundreds of millions of years.Item The Equidae from Gladysvale, a Hominin locality in the Cradle of Humankind, South Africa(University of the Witwatersrand, Johannesburg, 2023-10) Van der Merwe, Daniel Jean; Badenhorst, ShawThe later Pleistocene compared to modern census data indicated that Equidae are represented lower than comparably sized bovids (BOV III & IV). The reason for this may be due to numerous factors that have been previously investigated such as, landscape usage, carnivore and prey relationships and accumulation factors. However, a largely unexplored factor that may also have played a vital role in their lower representation may have been the difference and effectiveness of predator avoidance behaviours utilized by Equidae. The Equidae remains from the external and internal deposits of Gladysvale (730 to 580 Kya and 257 to 195 Kya) in the Cradle of Humankind, may provide insight into the predatory avoidance behaviours of two different Equidae species, Equus capensis and Equus quagga. This study aimed to create and renew an understanding of the role of these animals within larger faunal communities in the Cradle of Humankind. Equidae fossil material mostly from Gladysvale along with supporting material from Sterkfontein, Kromdraai and Coopers were examined, measured and photographed, in an attempt to broaden the understanding of Equidae relations within the Cradle of Humankind. Furthermore, to also elaborate on the potential differences between Equus capensis and Equus quagga. Past research has usually assigned Equus capensis to the larger version of Equus quagga during the later Pleistocene, with other studies based on DNA analysis suggesting the two species have very little intraspecific diversity. However as seen in this study it would appear that there is a notable difference in size between the two Equidae species, but also a difference in overall representation within the Cradle of Humankind. This could imply that not only are the two species different in size but that they also employed different predatory avoidance behaviours.Item 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.Item 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, BernhardThis 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.Item 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, VincentMalapa 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.