Micro-structures, mineralogy, and chemistry of peritidal tufa stromatolites along the Eastern Cape coast
- Edwards, Mark Joseph Kalahari, Rishworth, Gavin M
- Authors: Edwards, Mark Joseph Kalahari , Rishworth, Gavin M
- Date: 2019
- Subjects: Mineralogy -- Analysis -- South Africa , Environmental forensics Environmental chemistry Stromatolites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39896 , vital:35503
- Description: Peritidal tufa microbialites occurring along the coast near Port Elizabeth, South Africa have been investigated from multiple disciplines and are found to be similar to supratidal tufa deposits in South West Australia. Studies have been conducted on the biological factors, geomorphology, ecosystems, and associated water chemistry. However, to date no mineralogical, micro-fabric, or geochemical analyses have been reported on these tufa deposits. This work, carried out at a previously well-studied area, provides the first study of this kind on the tufa. Chapter 1 is a mineralogical and micro-fabric analysis of the tufa deposits near Port Elizabeth for the purpose of classification and contextualisation. Chapter 2 provides the first geochemical study of these peritidal microbialites. X-Ray diffraction (XRD) investigations reveal dominance of low-Mg calcite in the mineral make-up of the tufa. A micro-structure analysis via thin section exposes a number of fabrics, suggesting various micro-facies: phytoherm boundstone (layered), phytoherm framestone (non-layered), lithoclast, and minor metazoan tufa. Scanning electron microscopy (SEM) images show micro- to nano- scale variation in calcite grains and epitaxial forms of needlefibre calcite (NFC). The elemental composition of the tufa deposits were examined by X-ray fluorescence (XRF), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS), and Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDS). XRF and LA-ICP-MS were used to analyse the bulk rock chemistry while SEM/EDS was used to scrutinize specific areas within the tufa. These observations suggest the deposits are better classified as tufa microbialites (rather than exclusively “stromatolites”) and outline similarities and disparities to the micro-fabrics of supratidal tufa deposits in South West Australia, and Cape Morgan, South Africa. Here the Port Elizabeth tufa is shown to be similar, in terms of the dominant elements (O, Ca and to a lesser extent, Mg and Sr), to the Australian deposits despite subtle dissimilarities in water chemistry. Increasing trends toward more marine tufa for many elements are also shown here and can be explained by the interaction with increased amounts of sedimentary products and/or interactions with more saline water that contains a higher TDS (Total Dissolved Salts). This is also the first study to report needle-fibre calcite formation in stromatolites and the first to geochemically analyse modern peritidal microbialites.
- Full Text:
- Date Issued: 2019
- Authors: Edwards, Mark Joseph Kalahari , Rishworth, Gavin M
- Date: 2019
- Subjects: Mineralogy -- Analysis -- South Africa , Environmental forensics Environmental chemistry Stromatolites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39896 , vital:35503
- Description: Peritidal tufa microbialites occurring along the coast near Port Elizabeth, South Africa have been investigated from multiple disciplines and are found to be similar to supratidal tufa deposits in South West Australia. Studies have been conducted on the biological factors, geomorphology, ecosystems, and associated water chemistry. However, to date no mineralogical, micro-fabric, or geochemical analyses have been reported on these tufa deposits. This work, carried out at a previously well-studied area, provides the first study of this kind on the tufa. Chapter 1 is a mineralogical and micro-fabric analysis of the tufa deposits near Port Elizabeth for the purpose of classification and contextualisation. Chapter 2 provides the first geochemical study of these peritidal microbialites. X-Ray diffraction (XRD) investigations reveal dominance of low-Mg calcite in the mineral make-up of the tufa. A micro-structure analysis via thin section exposes a number of fabrics, suggesting various micro-facies: phytoherm boundstone (layered), phytoherm framestone (non-layered), lithoclast, and minor metazoan tufa. Scanning electron microscopy (SEM) images show micro- to nano- scale variation in calcite grains and epitaxial forms of needlefibre calcite (NFC). The elemental composition of the tufa deposits were examined by X-ray fluorescence (XRF), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS), and Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDS). XRF and LA-ICP-MS were used to analyse the bulk rock chemistry while SEM/EDS was used to scrutinize specific areas within the tufa. These observations suggest the deposits are better classified as tufa microbialites (rather than exclusively “stromatolites”) and outline similarities and disparities to the micro-fabrics of supratidal tufa deposits in South West Australia, and Cape Morgan, South Africa. Here the Port Elizabeth tufa is shown to be similar, in terms of the dominant elements (O, Ca and to a lesser extent, Mg and Sr), to the Australian deposits despite subtle dissimilarities in water chemistry. Increasing trends toward more marine tufa for many elements are also shown here and can be explained by the interaction with increased amounts of sedimentary products and/or interactions with more saline water that contains a higher TDS (Total Dissolved Salts). This is also the first study to report needle-fibre calcite formation in stromatolites and the first to geochemically analyse modern peritidal microbialites.
- Full Text:
- Date Issued: 2019
Spatial and temporal heterogeneity of plant flammability
- Authors: Calitz, Wynand
- Date: 2018
- Subjects: Forest plants , Forest ecology Plants -- Adaptation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23500 , vital:30572
- Description: Heterogeneity in the natural environment has led to plants adapting traits to fit a niche. Within natural systems, fire has been a major driver of vegetation across the globe. Flammability has been suggested by many to be a trait adapted to reoccurring fire events. Much of the literature on flammability is theoretical and little has been done to cement it as a functional trait. In this thesis, I explore flammability across a wide range of plant species from both fire-free and -driven communities and compare observed results to other functional traits to identify if any link may exist between fire and being flammable. I further focus on the impact moisture availability may have on flammability as fire regimes are often correlated to rainfall season. Lastly, I investigate how different vegetation types respond to seasonal climate in terms of flammability. As a functional trait, flammability does correlate with traits associated with fire-driven system (e.g. small leaves in dense twig matrix). However, fire associated traits were also observed in fire-free species (Forest, Thicket, and Nama-Karoo), and in some cases traits not associated to fire proved flammable (e.g. large leaves on trees). I find that at a regional scale, plant moisture only correlates to flammability when rainfall amounts are well above or below average (e.g. drought). I also identify that species have different responses to moisture fluctuations and that inherent or accidental responses may influence observed flammability (e.g. trichomes). Lastly, I note that some biomes indicate strong association to season or climate (Fynbos and Thicket), while others indicate plasticity towards weather with species having different responses (Grassland). The study is the first to present estimates of flammability across a large number of species sampled at different times of the year. Future research will have to approach flammability as a meta-analysis by experimenting on different scales, particularly temporal and spatial scales.
- Full Text:
- Date Issued: 2018
- Authors: Calitz, Wynand
- Date: 2018
- Subjects: Forest plants , Forest ecology Plants -- Adaptation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23500 , vital:30572
- Description: Heterogeneity in the natural environment has led to plants adapting traits to fit a niche. Within natural systems, fire has been a major driver of vegetation across the globe. Flammability has been suggested by many to be a trait adapted to reoccurring fire events. Much of the literature on flammability is theoretical and little has been done to cement it as a functional trait. In this thesis, I explore flammability across a wide range of plant species from both fire-free and -driven communities and compare observed results to other functional traits to identify if any link may exist between fire and being flammable. I further focus on the impact moisture availability may have on flammability as fire regimes are often correlated to rainfall season. Lastly, I investigate how different vegetation types respond to seasonal climate in terms of flammability. As a functional trait, flammability does correlate with traits associated with fire-driven system (e.g. small leaves in dense twig matrix). However, fire associated traits were also observed in fire-free species (Forest, Thicket, and Nama-Karoo), and in some cases traits not associated to fire proved flammable (e.g. large leaves on trees). I find that at a regional scale, plant moisture only correlates to flammability when rainfall amounts are well above or below average (e.g. drought). I also identify that species have different responses to moisture fluctuations and that inherent or accidental responses may influence observed flammability (e.g. trichomes). Lastly, I note that some biomes indicate strong association to season or climate (Fynbos and Thicket), while others indicate plasticity towards weather with species having different responses (Grassland). The study is the first to present estimates of flammability across a large number of species sampled at different times of the year. Future research will have to approach flammability as a meta-analysis by experimenting on different scales, particularly temporal and spatial scales.
- Full Text:
- Date Issued: 2018
An investigation into the role of social media in the 2014 South African general election
- Authors: Numa, Esethu
- Date: 2015
- Subjects: Social media -- South Africa , Communication in politics -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/5271 , vital:20833
- Description: The citizens of a state make sense of political parties from what is communicated about the parties as well as how that message is communicated. The use of social media, as a campaign communication vehicle, by political parties and voters is increasing, which brings rise to the need to examine the role of social media in South African politics. This study, which is a necessary exploration of political communication in South Africa, particularly on social media post-1994, looks at the scope of political communication on social media pre and post the 2014 elections in South Africa. Through a content analysis, this study analyses the communication messages of political parties on Twitter and the public‟s response to those messages. Furthermore, drawing from the theories of Framing and Agenda setting, this study explores how issues are framed on social media as well as the agenda setting role of social media. The study also identifies the issues that present themselves in political communication through social media in South Africa, and proposes ways in which the political parties could campaign more compellingly and effectively on social media.
- Full Text:
- Date Issued: 2015
- Authors: Numa, Esethu
- Date: 2015
- Subjects: Social media -- South Africa , Communication in politics -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/5271 , vital:20833
- Description: The citizens of a state make sense of political parties from what is communicated about the parties as well as how that message is communicated. The use of social media, as a campaign communication vehicle, by political parties and voters is increasing, which brings rise to the need to examine the role of social media in South African politics. This study, which is a necessary exploration of political communication in South Africa, particularly on social media post-1994, looks at the scope of political communication on social media pre and post the 2014 elections in South Africa. Through a content analysis, this study analyses the communication messages of political parties on Twitter and the public‟s response to those messages. Furthermore, drawing from the theories of Framing and Agenda setting, this study explores how issues are framed on social media as well as the agenda setting role of social media. The study also identifies the issues that present themselves in political communication through social media in South Africa, and proposes ways in which the political parties could campaign more compellingly and effectively on social media.
- Full Text:
- Date Issued: 2015
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