Characterizing shift systems and exploring their effects on sleep and fatigue in South African freight railway operators
- Authors: Mona, Chumani
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424300 , vital:72141
- Description: Embargoed. Expected release date 2025. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Mona, Chumani
- Date: 2023-10-13
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424300 , vital:72141
- Description: Embargoed. Expected release date 2025. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2023
- Full Text:
- Date Issued: 2023-10-13
The narratives of women in South Africa who use social media to talk about gender-based violence
- Authors: Walton, Donica Jasmin
- Date: 2022-04-07
- Subjects: Women Violence against South Africa , Social media and society South Africa , Internet and activism South Africa , Discourse analysis, Narrative , Internet and women South Africa , Subject positions
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232590 , vital:50005
- Description: There has been research conducted, both globally and in South Africa, on social media activism against gender-based violence (GBV). However, most research on the topic is based on participants in other parts of the world. Not much has been published on Black, African women. More specifically, not much is known about how women in South Africa experience using social media to talk about GBV. This research project draws on critical feminism and a narrative-discursive approach to explore the narratives of women in South Africa who use social media to talk about GBV. This is done by identifying the discourses women draw on to construct narratives, the subject positions utilised within these discourses, and how “trouble” and “repair” features in the narratives and positioning of women. Twelve interviews were conducted with women who volunteered and fit the inclusion criteria. The analysis of data was presented in two parts. The first set of discourses (discourses of ‘efficacy’, ‘convenience’, and ‘education’) were focused on what the use of social media achieves irrespective of the topic being discussed. These discourses speak to the idea that social media is powerful and useful because of its reach, speed, immediacy, and ability to be used to educate and be educated. The second set of discourses (discourses of ‘community and solidarity’, ‘validation’, and ‘vulnerability’) were focused on what the use of social media does for the people participating. Women have found a community and solidarity, and their experiences and thoughts have been validated on social media. Overall, the women in this research project justified their use of social media for activism against GBV, and acknowledged the tension that exists because despite its potential, there are limitations. , Thesis (MSocSci) -- Faculty of Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-04-07
- Authors: Walton, Donica Jasmin
- Date: 2022-04-07
- Subjects: Women Violence against South Africa , Social media and society South Africa , Internet and activism South Africa , Discourse analysis, Narrative , Internet and women South Africa , Subject positions
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232590 , vital:50005
- Description: There has been research conducted, both globally and in South Africa, on social media activism against gender-based violence (GBV). However, most research on the topic is based on participants in other parts of the world. Not much has been published on Black, African women. More specifically, not much is known about how women in South Africa experience using social media to talk about GBV. This research project draws on critical feminism and a narrative-discursive approach to explore the narratives of women in South Africa who use social media to talk about GBV. This is done by identifying the discourses women draw on to construct narratives, the subject positions utilised within these discourses, and how “trouble” and “repair” features in the narratives and positioning of women. Twelve interviews were conducted with women who volunteered and fit the inclusion criteria. The analysis of data was presented in two parts. The first set of discourses (discourses of ‘efficacy’, ‘convenience’, and ‘education’) were focused on what the use of social media achieves irrespective of the topic being discussed. These discourses speak to the idea that social media is powerful and useful because of its reach, speed, immediacy, and ability to be used to educate and be educated. The second set of discourses (discourses of ‘community and solidarity’, ‘validation’, and ‘vulnerability’) were focused on what the use of social media does for the people participating. Women have found a community and solidarity, and their experiences and thoughts have been validated on social media. Overall, the women in this research project justified their use of social media for activism against GBV, and acknowledged the tension that exists because despite its potential, there are limitations. , Thesis (MSocSci) -- Faculty of Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-04-07
Integration of dual metallophthalocyanine catalysis and green energy for sustainable oxidative removal of endocrine disrupting compounds
- Authors: Kruid, Jan
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192820 , vital:45267
- Description: Thesis (PhD) -- Faculty of Science, Biotechnology Innovation Centre, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Kruid, Jan
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192820 , vital:45267
- Description: Thesis (PhD) -- Faculty of Science, Biotechnology Innovation Centre, 2021
- Full Text:
- Date Issued: 2021-10-29
Understanding human‐wildlife conflict: a geographic study of the Pringle Bay chacma baboon troop
- Authors: Parsons, Wendy Jennifer
- Date: 2021-10-29
- Subjects: Chacma baboon South Africa Pringle Bay , Human-animal relationships South Africa Pringle Bay , Radio collars , Geographic information systems , Chacma baboon South Africa Pringle Bay Geographical distribution , Chacma baboon Behavior South Africa Pringle Bay , Chacma baboon Effect of human beings on South Africa Pringle Bay , Geospatial data , User-generated content
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/294828 , vital:57259
- Description: A better appreciation of the physical geography and environmental factors that play a role in the movement of the Chacma baboon troop in and around Pringle Bay (Overberg Municipality) and part of the Kogelberg Biosphere could lead to a better understanding of their movement. In turn, this insight may contribute to reducing the human‐wildlife conflict that has arisen in the town. Humanwildlife conflict escalated after the rapid urban development that followed the introduction of electricity in 1993. The baboon‐human conflict in Pringle Bay is, in part, due to habitat loss caused by urban development and the easy availability of food in the urban area. The wild animal’s natural behaviour (seeking food and fresh water) and the human way of living (food and waste management) has led to baboon habituation and increased raiding in the village. The objective of this geographic study was to understand the baboon troops spatial and temporal movements. Two methods are being used to track the baboon troop. The first method entails collection of data from GPS tracking collars which record the location of the baboons at 30 minute intervals. This is considered a reliable, but invasive and expensive method where the alpha male and female baboon had to be captured and fitted with tracking collars. The second method entails using volunteered geographic data, in this case, information from a WhatsApp baboon alert group. While this provided data at no real cost, the mining of the information was challenging and building a geodatabase was time consuming. However, this citizen science approach added valuable data and was able to identify human‐wildlife conflict sites in the urban area. The baboon location data was mapped using GIS. Primary and secondary spatial data was sourced and added to the geodatabase created in ArcMap 10.7. Various ArcMap tools were used in analysing the environmental factors (climate, vegetation, water sources and topography) together with the location data. Analysis of this data allowed the range of the baboons to be mapped, showing the maximum extent of the territory the baboons move in. The was refined by mapping their home range (defined as the area in which they spend 95% of the time) and their core area (in which they spend 50% of the time). High activity areas ‐ or hotspots ‐ were identified, as were the baboon sleep sites. The data allowed for habitat use and seasonal patterns of movement to be explored. A key finding of the research was that the baboons were observed outside of the urban area for 82% of the time. The baboons spent the majority of their time in mountain fynbos vegetation. Hotspot areas showing significant baboon activity were identified within the town and close correlation with their sleep sites and wetland areas was evident. No definitive seasonal or weather patterns were found that influence the baboon distribution. Baboon management is complex and difficult. The sustainability of the baboon troop is important for the biodiversity of the Kogelberg Biosphere Reserve. While the baboons should not be encouraged to enter the urban area, the residents should play a role in reducing the availability of food and baboonproofing their properties. The Overstrand Municipality also needs to address waste management and waste collection in the town. Understanding the biogeography of the baboons and implementing the above‐mentioned mitigating management measures would encourage human‐wildlife coexistence and inform future baboon management plans. , Thesis (MSc) -- Faculty of Science, Geography, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Parsons, Wendy Jennifer
- Date: 2021-10-29
- Subjects: Chacma baboon South Africa Pringle Bay , Human-animal relationships South Africa Pringle Bay , Radio collars , Geographic information systems , Chacma baboon South Africa Pringle Bay Geographical distribution , Chacma baboon Behavior South Africa Pringle Bay , Chacma baboon Effect of human beings on South Africa Pringle Bay , Geospatial data , User-generated content
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/294828 , vital:57259
- Description: A better appreciation of the physical geography and environmental factors that play a role in the movement of the Chacma baboon troop in and around Pringle Bay (Overberg Municipality) and part of the Kogelberg Biosphere could lead to a better understanding of their movement. In turn, this insight may contribute to reducing the human‐wildlife conflict that has arisen in the town. Humanwildlife conflict escalated after the rapid urban development that followed the introduction of electricity in 1993. The baboon‐human conflict in Pringle Bay is, in part, due to habitat loss caused by urban development and the easy availability of food in the urban area. The wild animal’s natural behaviour (seeking food and fresh water) and the human way of living (food and waste management) has led to baboon habituation and increased raiding in the village. The objective of this geographic study was to understand the baboon troops spatial and temporal movements. Two methods are being used to track the baboon troop. The first method entails collection of data from GPS tracking collars which record the location of the baboons at 30 minute intervals. This is considered a reliable, but invasive and expensive method where the alpha male and female baboon had to be captured and fitted with tracking collars. The second method entails using volunteered geographic data, in this case, information from a WhatsApp baboon alert group. While this provided data at no real cost, the mining of the information was challenging and building a geodatabase was time consuming. However, this citizen science approach added valuable data and was able to identify human‐wildlife conflict sites in the urban area. The baboon location data was mapped using GIS. Primary and secondary spatial data was sourced and added to the geodatabase created in ArcMap 10.7. Various ArcMap tools were used in analysing the environmental factors (climate, vegetation, water sources and topography) together with the location data. Analysis of this data allowed the range of the baboons to be mapped, showing the maximum extent of the territory the baboons move in. The was refined by mapping their home range (defined as the area in which they spend 95% of the time) and their core area (in which they spend 50% of the time). High activity areas ‐ or hotspots ‐ were identified, as were the baboon sleep sites. The data allowed for habitat use and seasonal patterns of movement to be explored. A key finding of the research was that the baboons were observed outside of the urban area for 82% of the time. The baboons spent the majority of their time in mountain fynbos vegetation. Hotspot areas showing significant baboon activity were identified within the town and close correlation with their sleep sites and wetland areas was evident. No definitive seasonal or weather patterns were found that influence the baboon distribution. Baboon management is complex and difficult. The sustainability of the baboon troop is important for the biodiversity of the Kogelberg Biosphere Reserve. While the baboons should not be encouraged to enter the urban area, the residents should play a role in reducing the availability of food and baboonproofing their properties. The Overstrand Municipality also needs to address waste management and waste collection in the town. Understanding the biogeography of the baboons and implementing the above‐mentioned mitigating management measures would encourage human‐wildlife coexistence and inform future baboon management plans. , Thesis (MSc) -- Faculty of Science, Geography, 2021
- Full Text:
- Date Issued: 2021-10-29
Parents’ involvement in education of their children: case study of two selected secondary schools in the Amathole West District
- Authors: Adelabu, O J
- Date: 2020-10
- Subjects: Education -- Parent participation , Parent-teacher relationships
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19969 , vital:44857
- Description: Parents’ involvement is a very important element that has an influence on children’s education. However, research has shown that parents’ involvement is the biggest challenge facing South African schools. The study sought to investigate parents’ involvement in the education of their children at secondary school in Amathole West District, Eastern Cape Province of South Africa. The study was underpinned by Epstein’s theory of parental involvement and the Ecological framework. A qualitative approach was adopted in this study which was located within an interpretivist paradigm and used a case study approach with a sample of 26 participants which includes (2 school principals, 6 educators, 6 parents and 12 learners) were selected conveniently, data was collected using focus group discussions, interviews and document analysis. The study revealed that although schools have employed various strategies to improve parental involvement in their children’s education, there are still challenges which inhibit the effectiveness of these strategies. The study also revealed that most parents are unable to get involved as expected by the school due to some challenges such as poverty, unemployment, educational background, distance and illiteracy. Consequently, the study recommended that parents must be more actively involved in the school and collaborate with their children’s teacher in order to bring out the best in their children. Furthermore, to ensure effective parents’ involvement, schools may have activities that can develop, improve and encourage parents’ involvement in such areas as parenting, communication, learning at home, volunteering, decision making and community collaboration. , Thesis (MEd) -- Faculty of Education, 2020
- Full Text:
- Date Issued: 2020-10
- Authors: Adelabu, O J
- Date: 2020-10
- Subjects: Education -- Parent participation , Parent-teacher relationships
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19969 , vital:44857
- Description: Parents’ involvement is a very important element that has an influence on children’s education. However, research has shown that parents’ involvement is the biggest challenge facing South African schools. The study sought to investigate parents’ involvement in the education of their children at secondary school in Amathole West District, Eastern Cape Province of South Africa. The study was underpinned by Epstein’s theory of parental involvement and the Ecological framework. A qualitative approach was adopted in this study which was located within an interpretivist paradigm and used a case study approach with a sample of 26 participants which includes (2 school principals, 6 educators, 6 parents and 12 learners) were selected conveniently, data was collected using focus group discussions, interviews and document analysis. The study revealed that although schools have employed various strategies to improve parental involvement in their children’s education, there are still challenges which inhibit the effectiveness of these strategies. The study also revealed that most parents are unable to get involved as expected by the school due to some challenges such as poverty, unemployment, educational background, distance and illiteracy. Consequently, the study recommended that parents must be more actively involved in the school and collaborate with their children’s teacher in order to bring out the best in their children. Furthermore, to ensure effective parents’ involvement, schools may have activities that can develop, improve and encourage parents’ involvement in such areas as parenting, communication, learning at home, volunteering, decision making and community collaboration. , Thesis (MEd) -- Faculty of Education, 2020
- Full Text:
- Date Issued: 2020-10
Modification and application of the decentralised wastewater treatment technology for greywater treatment to reduce water needs
- Authors: Ngqwala, Nosiphiwe Patience
- Date: 2015
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/193509 , vital:45338
- Description: Water is a scarce resource that is being acknowledged as a limiting factor to further social- economic growth and development. Demand for freshwater is increasing with corresponding increases in human population, industrial and agricultural activities. Alternative sources, such as greywater and rainwater are often polluted. Though greywater can be used for non-potable purposes, such as irrigation, it still requires some measures of treatment to improve its quality. To improve on greywater quality to facilitate its reuse, decentralised wastewater treatment technologies carry a great potential as complementary and alternative means of wastewater management particularly in peri-urban areas. Five research goals are addressed in this thesis: (i) to monitor the performance of Fly Ash Lime Filter Tower (FLFT) in the treatment of greywater; (ii) to modify the Fly Ash Lime Filter Tower in the treatment of greywater in order to reduce the pH of the greywater, and improved on the reduction of chemical oxygen demand (COD) and coliform counts; (iii) to investigate the potential of the reuse of greywater for irrigation; (iv) to undertake a techno analysis of the FLFT system for commercial use; and (v) to evaluate the use of hydrogen-sulphide (H2S) test kit to monitor faecal contamination of various water sources using a multidisciplinary approach. The modification of the FLFT indicated good treatment efficiency, reducing the concentrations of COD, chlorides, nitrates, ammonia and sulphate by 82.6%, 60.4%, 72.9%, 60.5%, and 53.9%, respectively; while the average pH was at 8.3. Greywater contains nutrients that are beneficial to the growth of most plants. Growth variables included biomass, stem height, number of leaves and number of vegetables harvested. Soil analysis showed no effects of the treated greywater on soil physico-chemical and microbial quality with bulk density 2.0g/cm3, average pH 7.4, total phosphorus 0.16mg/L 8, faecal coliform 0.3 CFU/100 ml. The tomatoes had high biomass and dry weight (150 g; 33g) than beetroot (35 g; 15 g). Crops irrigated with greywater significantly grew faster compared with those irrigated with tap water. The community approach highlighted the value of knowledge management in greywater reuse. It highlighted the importance of creating an institutional knowledge in water management using the H2S kit. The techno-economic analysis was used to evaluate key factors and the activities that are relevant to develop a sustainable FLFT in order to gain insights into the possibility of developing, and incorporating a business model framework to support decision making in value creation and value capturing during the research and the scaling up of the system. By this, a long term perspective to accomplish sustainable FLFT service businesses can be achieved. , Thesis (PhD) -- Faculty of Pharmacy, Pharmacy, 2015
- Full Text:
- Date Issued: 2015
- Authors: Ngqwala, Nosiphiwe Patience
- Date: 2015
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/193509 , vital:45338
- Description: Water is a scarce resource that is being acknowledged as a limiting factor to further social- economic growth and development. Demand for freshwater is increasing with corresponding increases in human population, industrial and agricultural activities. Alternative sources, such as greywater and rainwater are often polluted. Though greywater can be used for non-potable purposes, such as irrigation, it still requires some measures of treatment to improve its quality. To improve on greywater quality to facilitate its reuse, decentralised wastewater treatment technologies carry a great potential as complementary and alternative means of wastewater management particularly in peri-urban areas. Five research goals are addressed in this thesis: (i) to monitor the performance of Fly Ash Lime Filter Tower (FLFT) in the treatment of greywater; (ii) to modify the Fly Ash Lime Filter Tower in the treatment of greywater in order to reduce the pH of the greywater, and improved on the reduction of chemical oxygen demand (COD) and coliform counts; (iii) to investigate the potential of the reuse of greywater for irrigation; (iv) to undertake a techno analysis of the FLFT system for commercial use; and (v) to evaluate the use of hydrogen-sulphide (H2S) test kit to monitor faecal contamination of various water sources using a multidisciplinary approach. The modification of the FLFT indicated good treatment efficiency, reducing the concentrations of COD, chlorides, nitrates, ammonia and sulphate by 82.6%, 60.4%, 72.9%, 60.5%, and 53.9%, respectively; while the average pH was at 8.3. Greywater contains nutrients that are beneficial to the growth of most plants. Growth variables included biomass, stem height, number of leaves and number of vegetables harvested. Soil analysis showed no effects of the treated greywater on soil physico-chemical and microbial quality with bulk density 2.0g/cm3, average pH 7.4, total phosphorus 0.16mg/L 8, faecal coliform 0.3 CFU/100 ml. The tomatoes had high biomass and dry weight (150 g; 33g) than beetroot (35 g; 15 g). Crops irrigated with greywater significantly grew faster compared with those irrigated with tap water. The community approach highlighted the value of knowledge management in greywater reuse. It highlighted the importance of creating an institutional knowledge in water management using the H2S kit. The techno-economic analysis was used to evaluate key factors and the activities that are relevant to develop a sustainable FLFT in order to gain insights into the possibility of developing, and incorporating a business model framework to support decision making in value creation and value capturing during the research and the scaling up of the system. By this, a long term perspective to accomplish sustainable FLFT service businesses can be achieved. , Thesis (PhD) -- Faculty of Pharmacy, Pharmacy, 2015
- Full Text:
- Date Issued: 2015
The depositional history and evaluation of two late quaternary, diamondiferous pocket beaches, south-western Namibia
- Authors: Milad, Micael George
- Date: 2004-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/420934 , vital:71795
- Description: The two Late Quaternary, diamondiferous pocket beach deposits studied here are situated along a 10 km stretch of the storm-dominated, Atlantic coastline of the Sperrgebiet, south-western Namibia. The pocket beaches are approximately 130 km north of the Orange River mouth, which is widely accepted as a long-lived point source for diamonds sourced from the interior of southern Africa. A total of fourteen pocket beach deposits were recently evaluated in this area, but only two of these, namely Site 2 (to the south) and Site 3 (to the north), are considered here. The main diamondbearing horizons are beach gravels, which occur within, and form part of, the pocket beach sequences. The beach gravels are mostly blanketed by sand overburden, meaning that exposures available for study were limited, and much reliance was placed on borehole logging and observations of evaluation sample tailings. The main aims are to unravel the depositional history of the pocket beach sequences, identify the controls on diamond mineralisation in the beach gravels, and critically examine two different methods of estimating average diamond size for the deposits. In pursuit of these aims, sedimentological characteristics of the unconsolidated pocket beach deposits were recorded using small diameter drill holes, hydraulic grab bulk samples, trench exposures and surface outcrops. The surface geology, geomorphology and modern wave patterns were mapped using high-resolution, Airborne Laser Survey imagery coupled with extensive field checking. Three-dimensional geological modeling software was used to gain insight into the subsurface morphology of the deposits. Fossil shell samples were used to aid interpretation of ancient depositional environments and to date parts of the pocket beach sequences. Variations in diamond concentration and the size of diamonds were recorded using bulk samples, some of which were taken from a trench, but most of which were excavated using a hydraulic grab tool called the GB50. Finally, by using diamond size data from Site 3, sample data from diamondiferous beach gravels to the south of the study area and sample campaign simulations, two alternative methods of evaluating average diamond size in marine gravel deposits were appraised.The pocket beach sequences occur within north-south trending valleys of a major deflation basin and are separated from one another by rocky headlands. The ridge-and-valley topography of the deflation basin has resulted from differential erosion of Late Proterozoic basement rock units, alternating layers of which differ greatly in their resistance to the long-lived, local denudationalprocesses. On the basis of the stratigraphic information collected from the unconsolidated pocket beach valley fills, interpreted within the context of global, Late Pleistocene sea level records, the following depositional history is deduced : a) Deposition of sheetflood gravels by ephemeral streams, activated during a regressive phase. b) Transgression, culminating in the deposition of a gravel beach, representing a sea level highstand of +4 metres above mean sea level (mamsl) at between 120 000 and 130 000 BP. c)A regressive phase, resulting in deflation of former valley fills to the bedrock valley floor and accompanied by re-activation of ephemeral stream activity to form sheetflood deposits; this represents a protracted period of subaerial exposure of the +4 m gravel beach deposit. d) Deposition of a great volume of sediment in the valleys during the latter stages of the transgression from the Last Glacial Maximum (LGM). The sequence generated during this phase, which started at ca. 9 000 BP, contains : i) pan/coastal sabkha sediments, ii) shallow, sheltered bay sediments, iii) back-barrier lagoonal sediments, iv) a gravel beach deposit representing a sea level stillstand at -5 mamsl, laid down between 7 600 and 5 600 BP, v) another gravel beach deposit representing the well-known Middle Holocene sea level highstand at +2 to +3 mamsl, laid down at ca. 5 000 BP, and which terminated the transgression from the LGM. e) A minor regression to the current sea level, accompanied by progradation of the shoreline to its current position. This progradational marine unit consists almost entirely of sand and grit, reflecting the lack of gravel supply to this part of the coastline in the most recent past. f) Deposition of modern coastal dunes, which cap the pocket beach sequence and are the youngest sediments in the study area. Using trench and hydraulic grab evaluation sample results, in combination with analysis of wave patterns and field observations, the following local controls on the density distribution (ie. concentration) and size distribution of diamonds in the gravel beach deposits (+4, -5 and +2 to +3 mamsl stands) are recognised: a) Gravel beach depositional processes, which are responsible for clast sorting on the beach, have influenced the density and size distribution of diamonds. The infill zone, or beach toe, favours maximum diamond concentration while diamond size decreases from the imbricate zone (intertidal) to the infill zone (subtidal). b) Wave energy is identified as the dominant local control on diamond size distribution, but has also influenced diamond concentration to a limited degree. Larger diamonds are intimately associated with coarser beach gravels, both of which are a reflection of increased wave energy. Higher concentrations of diamonds are sometimes associated with zones of coarser gravel and therefore greater wave energy. c) The time of deposition of the host gravel beach is seen to be the dominant controlling factor with respect to diamond concentration. This is seen as evidence of significant temporal variation in the availability of diamonds in the littoral evironment. A significant reduction (20%) in average diamond size from Site 2 to Site 3, over a distance of only 6 km, is evident. The following were identified as reasons for this reduction in diamond size : a) Longshore sorting processes, of which the long-lived northerly littoral drift is a key part, are known to have played a role in the diminution of diamond size northwards from the Orange River mouth point source. However, it is believed that this can only partly account for the observed 20% reduction in diamond size. b) Input of sediment and smaller diamonds at Site 3, reworked out of an older, Eocene-aged marine succession in the hinterland, is recognised as a possible additional reason for the large reduction in diamond size from Site 2 to Site 3. It is also speculated that the large size of the pocket beach at Site 3, relative to Site 2, may have resulted in lower average wave energy at Site 3, with consequent reduced average diamond size. Diamond size in the beach gravels of Site 3, as well as in beach gravels elsewhere in the Sperrgebiet, is seen to be lognormally-distributed within geologically homogeneous zones. In theory, lognormal mean estimators represent the best method of estimating average diamond size in such cases, whereas the arithmetic mean estimator has the tendency to overestimate when large outlier values occur. Lognormal mean estimators have the added benefit of providing for the calculation of confidence limits, which are becoming increasingly more important as financial lending institutions insist on better quantification of the risk involved in resource estimates. Sample campaign simulations demonstrate, for the kinds of diamond size-frequency distributions typical of beach gravel deposits at Site 3, that there is no significant improvement in the accuracy of average diamond size estimates when lognormal mean estimators are used instead of the arithmetic mean estimator. This is because the variance (a ) of the diamond populations is low, and large outlier values are extremely unlikely to occur. However, simulation of a diamond population with high variance, drawn from a sample of beach gravels near the Orange River mouth, shows that lognormal estimators produce significantly more accurate results when a is large. Since individual diamond weights were not recorded during evaluation sampling of Site 3, numerical solution of lognormal estimators is not possible, and these would need to be solved using a less accurate graphical method. It is therefore recommended that individual diamond weights are recorded in future sampling campaigns, allowing for the use of lognormal mean estimators, and the calculation of confidence limits for average diamond size estimates. , Thesis (MSc) -- Science, Geology, 2004
- Full Text:
- Date Issued: 2004-03
- Authors: Milad, Micael George
- Date: 2004-03
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/420934 , vital:71795
- Description: The two Late Quaternary, diamondiferous pocket beach deposits studied here are situated along a 10 km stretch of the storm-dominated, Atlantic coastline of the Sperrgebiet, south-western Namibia. The pocket beaches are approximately 130 km north of the Orange River mouth, which is widely accepted as a long-lived point source for diamonds sourced from the interior of southern Africa. A total of fourteen pocket beach deposits were recently evaluated in this area, but only two of these, namely Site 2 (to the south) and Site 3 (to the north), are considered here. The main diamondbearing horizons are beach gravels, which occur within, and form part of, the pocket beach sequences. The beach gravels are mostly blanketed by sand overburden, meaning that exposures available for study were limited, and much reliance was placed on borehole logging and observations of evaluation sample tailings. The main aims are to unravel the depositional history of the pocket beach sequences, identify the controls on diamond mineralisation in the beach gravels, and critically examine two different methods of estimating average diamond size for the deposits. In pursuit of these aims, sedimentological characteristics of the unconsolidated pocket beach deposits were recorded using small diameter drill holes, hydraulic grab bulk samples, trench exposures and surface outcrops. The surface geology, geomorphology and modern wave patterns were mapped using high-resolution, Airborne Laser Survey imagery coupled with extensive field checking. Three-dimensional geological modeling software was used to gain insight into the subsurface morphology of the deposits. Fossil shell samples were used to aid interpretation of ancient depositional environments and to date parts of the pocket beach sequences. Variations in diamond concentration and the size of diamonds were recorded using bulk samples, some of which were taken from a trench, but most of which were excavated using a hydraulic grab tool called the GB50. Finally, by using diamond size data from Site 3, sample data from diamondiferous beach gravels to the south of the study area and sample campaign simulations, two alternative methods of evaluating average diamond size in marine gravel deposits were appraised.The pocket beach sequences occur within north-south trending valleys of a major deflation basin and are separated from one another by rocky headlands. The ridge-and-valley topography of the deflation basin has resulted from differential erosion of Late Proterozoic basement rock units, alternating layers of which differ greatly in their resistance to the long-lived, local denudationalprocesses. On the basis of the stratigraphic information collected from the unconsolidated pocket beach valley fills, interpreted within the context of global, Late Pleistocene sea level records, the following depositional history is deduced : a) Deposition of sheetflood gravels by ephemeral streams, activated during a regressive phase. b) Transgression, culminating in the deposition of a gravel beach, representing a sea level highstand of +4 metres above mean sea level (mamsl) at between 120 000 and 130 000 BP. c)A regressive phase, resulting in deflation of former valley fills to the bedrock valley floor and accompanied by re-activation of ephemeral stream activity to form sheetflood deposits; this represents a protracted period of subaerial exposure of the +4 m gravel beach deposit. d) Deposition of a great volume of sediment in the valleys during the latter stages of the transgression from the Last Glacial Maximum (LGM). The sequence generated during this phase, which started at ca. 9 000 BP, contains : i) pan/coastal sabkha sediments, ii) shallow, sheltered bay sediments, iii) back-barrier lagoonal sediments, iv) a gravel beach deposit representing a sea level stillstand at -5 mamsl, laid down between 7 600 and 5 600 BP, v) another gravel beach deposit representing the well-known Middle Holocene sea level highstand at +2 to +3 mamsl, laid down at ca. 5 000 BP, and which terminated the transgression from the LGM. e) A minor regression to the current sea level, accompanied by progradation of the shoreline to its current position. This progradational marine unit consists almost entirely of sand and grit, reflecting the lack of gravel supply to this part of the coastline in the most recent past. f) Deposition of modern coastal dunes, which cap the pocket beach sequence and are the youngest sediments in the study area. Using trench and hydraulic grab evaluation sample results, in combination with analysis of wave patterns and field observations, the following local controls on the density distribution (ie. concentration) and size distribution of diamonds in the gravel beach deposits (+4, -5 and +2 to +3 mamsl stands) are recognised: a) Gravel beach depositional processes, which are responsible for clast sorting on the beach, have influenced the density and size distribution of diamonds. The infill zone, or beach toe, favours maximum diamond concentration while diamond size decreases from the imbricate zone (intertidal) to the infill zone (subtidal). b) Wave energy is identified as the dominant local control on diamond size distribution, but has also influenced diamond concentration to a limited degree. Larger diamonds are intimately associated with coarser beach gravels, both of which are a reflection of increased wave energy. Higher concentrations of diamonds are sometimes associated with zones of coarser gravel and therefore greater wave energy. c) The time of deposition of the host gravel beach is seen to be the dominant controlling factor with respect to diamond concentration. This is seen as evidence of significant temporal variation in the availability of diamonds in the littoral evironment. A significant reduction (20%) in average diamond size from Site 2 to Site 3, over a distance of only 6 km, is evident. The following were identified as reasons for this reduction in diamond size : a) Longshore sorting processes, of which the long-lived northerly littoral drift is a key part, are known to have played a role in the diminution of diamond size northwards from the Orange River mouth point source. However, it is believed that this can only partly account for the observed 20% reduction in diamond size. b) Input of sediment and smaller diamonds at Site 3, reworked out of an older, Eocene-aged marine succession in the hinterland, is recognised as a possible additional reason for the large reduction in diamond size from Site 2 to Site 3. It is also speculated that the large size of the pocket beach at Site 3, relative to Site 2, may have resulted in lower average wave energy at Site 3, with consequent reduced average diamond size. Diamond size in the beach gravels of Site 3, as well as in beach gravels elsewhere in the Sperrgebiet, is seen to be lognormally-distributed within geologically homogeneous zones. In theory, lognormal mean estimators represent the best method of estimating average diamond size in such cases, whereas the arithmetic mean estimator has the tendency to overestimate when large outlier values occur. Lognormal mean estimators have the added benefit of providing for the calculation of confidence limits, which are becoming increasingly more important as financial lending institutions insist on better quantification of the risk involved in resource estimates. Sample campaign simulations demonstrate, for the kinds of diamond size-frequency distributions typical of beach gravel deposits at Site 3, that there is no significant improvement in the accuracy of average diamond size estimates when lognormal mean estimators are used instead of the arithmetic mean estimator. This is because the variance (a ) of the diamond populations is low, and large outlier values are extremely unlikely to occur. However, simulation of a diamond population with high variance, drawn from a sample of beach gravels near the Orange River mouth, shows that lognormal estimators produce significantly more accurate results when a is large. Since individual diamond weights were not recorded during evaluation sampling of Site 3, numerical solution of lognormal estimators is not possible, and these would need to be solved using a less accurate graphical method. It is therefore recommended that individual diamond weights are recorded in future sampling campaigns, allowing for the use of lognormal mean estimators, and the calculation of confidence limits for average diamond size estimates. , Thesis (MSc) -- Science, Geology, 2004
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- Date Issued: 2004-03
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