Gender bias in the field of economics: an analysis of South African academia
- Authors: Hitchcock, Siobhan
- Date: 2020-10-30
- Subjects: Sexism South Africa , Sexism in higher education South Africa , Economics Study and teaching (Higher) South Africa , Economics teachers South Africa , Women in higher education South Africa
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/366275 , vital:65850
- Description: In recent years there has been a growing focus internationally on the low participation of females in Economics, both in academia and business. While female enrolment in higher education, including other maths-based subjects, has grown substantially, this has not been the case for Economics. Economics, particularly as one progresses through postgraduate studies to doctoral degrees now stands out as an outlier. A number of reasons have been advanced for this, including the nature of the subject, the type of people it attracts and the lack of female role models. Male and female enrolments in South African HEIs have grown between 2007 and 2017, but females have grown at a faster rate, thus increasing the female share of total enrolments to 59%. Female students are more successful and so make up an even greater proportion of South African graduates. Female enrolments and graduates are also higher than in the US. As in the US there is a significant drop off in female representation when progressing from undergraduate to postgraduate studies in South Africa. When looking at Economics in South Africa in comparison to the broad CESM categories, female enrolment in Economics Bachelor degrees is significantly lower than in Business and Humanities, but on a par with STEM subjects. At the Doctoral level, there are sharp drop offs in female enrolments for all categories. Business and Economics are the laggards at the Doctoral level, below STEM and Humanities. Furthermore, females make up a minority of academic staff in South African HEIs, with males dominating in especially the higher academic ranks. As one moves up the academic ladder, the female share decreases. This research analyses gender compositions of staff and students at South African HEIs. National data are obtained from government publications and data relating to four specific South African universities was obtained directly from the universities. Questionnaires were sent to a sample of academic staff and students who are in the field of economics to identify whether there is a role model effect for economics students and whether female academics experience the same forms of biases, discrimination, or treatment as that identified in international studies. It was concluded that while there are drop offs in the overall female representation of students at the Masters and Doctoral levels in South Africa, this share is gradually increasing. Additionally, Economics seems to perform better than what is depicted in the US, and in comparison to some STEM subjects in South Africa. Furthermore, the environment within the field of academic economics for both female students and staff seems to be more positive than what the international literature depicts for the US. But there are nonetheless different levels of satisfaction between male and female academic economists. While the student surveys revealed that female Economics students do not attach great importance to female role models, there is some evidence of correlation between the percentage of female professors and the percentage of female PhD students across a range of STEM subjects in South Africa. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2020
- Full Text:
- Date Issued: 2020-10-30
- Authors: Hitchcock, Siobhan
- Date: 2020-10-30
- Subjects: Sexism South Africa , Sexism in higher education South Africa , Economics Study and teaching (Higher) South Africa , Economics teachers South Africa , Women in higher education South Africa
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/366275 , vital:65850
- Description: In recent years there has been a growing focus internationally on the low participation of females in Economics, both in academia and business. While female enrolment in higher education, including other maths-based subjects, has grown substantially, this has not been the case for Economics. Economics, particularly as one progresses through postgraduate studies to doctoral degrees now stands out as an outlier. A number of reasons have been advanced for this, including the nature of the subject, the type of people it attracts and the lack of female role models. Male and female enrolments in South African HEIs have grown between 2007 and 2017, but females have grown at a faster rate, thus increasing the female share of total enrolments to 59%. Female students are more successful and so make up an even greater proportion of South African graduates. Female enrolments and graduates are also higher than in the US. As in the US there is a significant drop off in female representation when progressing from undergraduate to postgraduate studies in South Africa. When looking at Economics in South Africa in comparison to the broad CESM categories, female enrolment in Economics Bachelor degrees is significantly lower than in Business and Humanities, but on a par with STEM subjects. At the Doctoral level, there are sharp drop offs in female enrolments for all categories. Business and Economics are the laggards at the Doctoral level, below STEM and Humanities. Furthermore, females make up a minority of academic staff in South African HEIs, with males dominating in especially the higher academic ranks. As one moves up the academic ladder, the female share decreases. This research analyses gender compositions of staff and students at South African HEIs. National data are obtained from government publications and data relating to four specific South African universities was obtained directly from the universities. Questionnaires were sent to a sample of academic staff and students who are in the field of economics to identify whether there is a role model effect for economics students and whether female academics experience the same forms of biases, discrimination, or treatment as that identified in international studies. It was concluded that while there are drop offs in the overall female representation of students at the Masters and Doctoral levels in South Africa, this share is gradually increasing. Additionally, Economics seems to perform better than what is depicted in the US, and in comparison to some STEM subjects in South Africa. Furthermore, the environment within the field of academic economics for both female students and staff seems to be more positive than what the international literature depicts for the US. But there are nonetheless different levels of satisfaction between male and female academic economists. While the student surveys revealed that female Economics students do not attach great importance to female role models, there is some evidence of correlation between the percentage of female professors and the percentage of female PhD students across a range of STEM subjects in South Africa. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2020
- Full Text:
- Date Issued: 2020-10-30
Determination of speaker configuration for an immersive audio content creation system
- Authors: Lebusa, Motebang
- Date: 2020
- Subjects: Loudspeakers , Surround-sound systems , Algorithms , Coordinates
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/163375 , vital:41034
- Description: Various spatialisation algorithms require the knowledge of speaker locations to accurately localise sound in 3D environments. The rendering process uses speaker coordinates to feed into their algorithms so that they can render the immersive audio content as intended by an artist. The need to measure the loudspeaker coordinates becomes necessary, especially in environments where the speaker layouts change frequently. Manually measuring the coordinates, however, tends to be a laborious task that is prone to errors. This research provides an automated solution to the problem of speaker coordinates measurement. The solution system, SDIAS, is a client-server system that uses the capabilities provided by the Ethernet Audio Video Bridging standard to measure the 3D loudspeaker coordinates for immersive sound systems. SDIAS deploys commodity hardware and readily available software to implement the solution. A server sends a short tone to each speaker in the speaker configuration, at equal intervals. A microphone attached to a mobile device picks up these transmitted tones on the client side, from different locations. The transmission and reception times from both components of the system are used to measure the time of flight for each tone sent to a loudspeaker. These are then used to determine the 3D coordinates of each loudspeaker in the available layout. Tests were performed to determine the accuracy of the determination algorithm for SDIAS, and were compared to the manually measured coordinates. , Thesis (MSc) -- Faculty of Science, Computer Science, 2020
- Full Text:
- Date Issued: 2020
- Authors: Lebusa, Motebang
- Date: 2020
- Subjects: Loudspeakers , Surround-sound systems , Algorithms , Coordinates
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/163375 , vital:41034
- Description: Various spatialisation algorithms require the knowledge of speaker locations to accurately localise sound in 3D environments. The rendering process uses speaker coordinates to feed into their algorithms so that they can render the immersive audio content as intended by an artist. The need to measure the loudspeaker coordinates becomes necessary, especially in environments where the speaker layouts change frequently. Manually measuring the coordinates, however, tends to be a laborious task that is prone to errors. This research provides an automated solution to the problem of speaker coordinates measurement. The solution system, SDIAS, is a client-server system that uses the capabilities provided by the Ethernet Audio Video Bridging standard to measure the 3D loudspeaker coordinates for immersive sound systems. SDIAS deploys commodity hardware and readily available software to implement the solution. A server sends a short tone to each speaker in the speaker configuration, at equal intervals. A microphone attached to a mobile device picks up these transmitted tones on the client side, from different locations. The transmission and reception times from both components of the system are used to measure the time of flight for each tone sent to a loudspeaker. These are then used to determine the 3D coordinates of each loudspeaker in the available layout. Tests were performed to determine the accuracy of the determination algorithm for SDIAS, and were compared to the manually measured coordinates. , Thesis (MSc) -- Faculty of Science, Computer Science, 2020
- Full Text:
- Date Issued: 2020
The economic contribution of the tourism accommodation sector in the Karoo
- Authors: Chandler, Biddy Lee
- Date: 2013-04-06
- Subjects: Hospitality industry South Africa Karoo , Karoo (South Africa) Economic conditions , Small cities South Africa Karoo , Tourism South Africa Karoo
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/366169 , vital:65838
- Description: Tourism is not only the world’s largest traded commodity in which many countries have gained economic advantage and stability, it is also a phenomenon of great economic and social significance. Tourism’s contribution, especially within developing countries and within emerging markets like South Africa, has become increasingly significant as it has created major economic growth and has highlighted areas of potential new sustainable development. The ultimate goal of achieving an increase in GDP and the creation of new employment opportunities is enhanced through the development of tourism. Considering the importance of the above and because the impact of tourism development in small towns is of significant economic benefit, research into this field is of value. This is the core of this study. As a result of tourism demand continually changing in small towns, mostly due to globalisation, demographic changes and agricultural changes, the need to continually update tourism data to ensure that tourism products remain highly rated is vital. This requires identifying tourists’ needs and supplying exactly what tourists demand. More specifically, evaluating tourist satisfaction and dissatisfaction will give accurate indications of a destination’s ability to satisfy its tourists, which is what will encourage repeat visits. The first objective of this dissertation was to qualitatively evaluate, through determining 27 product owners’ and 206 tourists’, opinions/perceptions of the tourism product offering in the Karoo. This study examined the accommodation sector of the tourism industry within 13 small towns in the Karoo. This is a fast growing and maturing industry. The study revealed that product owners and tourists expressed a positive attitude towards the growth of tourism in the Karoo, which they said was due to its heritage and authenticity, climate, desert tourism, natural beauty, ecotourism, remoteness, peace and quiet and acting as a refuge in an unspoilt natural environment. Amongst other recommendations, this result highlighted the importance of keeping closed the ‘gap’ between the expected product/level of service and the customer’s perception of the actual product/service received, by paying special attention to each of the identified tourist benefits. Most importantly, product owners, local tourism organisations (LTOs), municipalities, the government and all tourism stakeholders need to ensure that they work efficiently and effectively through transparent and collaborative relationships to ensure that they generate the highest possible returns from tourism investment through strategies that take cognizance of the above. The second objective of this dissertation was to quantitatively evaluate the economic impact of tourism through gathering and calculating 107 tourists’ spending data and 15 product owners’ expenditure data over a six month period between December 2010 and May 2011 in Graaff-Reinet. It was found that there was an increase over time in tourist spending, which led to an increase in direct income (net injection of visitor spending) and thus there was an increase in indirect income(affecting the level of product owners’ income)in the Graaff-Reinet economy. The key calculations in this study reflected a high multiplier of 1.2and a small amount of leakage (21%);and the final tourism economic impact of the accommodation sector in Graaff-Reinet wasR8940 982.00. This implies a positive economic contribution to this town. A focus on growing the tourist market is therefore a goal worth pursuing. This study provides up-to-date, statistically valid numerical/quantitative data as well as current qualitative data. However, gathering data for a longitudinal study would be highly beneficial to determine trends of how the tourism market in small towns is developing. This field has been given minimal attention, specifically within small towns. This dissertation was thus an attempt to initiate and motivate further ongoing efforts with regards to gathering, specifically economic, tourism data. Showing the positive economic contribution, and the multiple ripple effects that attracting tourists to an area can have, and the ultimate measurable economic benefit created through having a strong multiplier effect, will hopefully encourage all stakeholders to be confident and take the tourism industry more seriously. This highlights the need to recognise the economic impact potential of the tourism sector and to use the positive results identified in this study as a tool to lobby for tourism investment, which is unfortunately not reflected currently in many governmental programmes. Developing greater co-operation and co-ordination between the private and public sectors is needed: the most appropriate development model for the tourism industry being government led, private sector driven, community based and labour conscious in order for it to reap the benefits reflected in this tourism study. , Thesis (MEcon) -- Faculty of Commerce, Economics and Economic History, 2013
- Full Text:
- Date Issued: 2013-04-06
- Authors: Chandler, Biddy Lee
- Date: 2013-04-06
- Subjects: Hospitality industry South Africa Karoo , Karoo (South Africa) Economic conditions , Small cities South Africa Karoo , Tourism South Africa Karoo
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/366169 , vital:65838
- Description: Tourism is not only the world’s largest traded commodity in which many countries have gained economic advantage and stability, it is also a phenomenon of great economic and social significance. Tourism’s contribution, especially within developing countries and within emerging markets like South Africa, has become increasingly significant as it has created major economic growth and has highlighted areas of potential new sustainable development. The ultimate goal of achieving an increase in GDP and the creation of new employment opportunities is enhanced through the development of tourism. Considering the importance of the above and because the impact of tourism development in small towns is of significant economic benefit, research into this field is of value. This is the core of this study. As a result of tourism demand continually changing in small towns, mostly due to globalisation, demographic changes and agricultural changes, the need to continually update tourism data to ensure that tourism products remain highly rated is vital. This requires identifying tourists’ needs and supplying exactly what tourists demand. More specifically, evaluating tourist satisfaction and dissatisfaction will give accurate indications of a destination’s ability to satisfy its tourists, which is what will encourage repeat visits. The first objective of this dissertation was to qualitatively evaluate, through determining 27 product owners’ and 206 tourists’, opinions/perceptions of the tourism product offering in the Karoo. This study examined the accommodation sector of the tourism industry within 13 small towns in the Karoo. This is a fast growing and maturing industry. The study revealed that product owners and tourists expressed a positive attitude towards the growth of tourism in the Karoo, which they said was due to its heritage and authenticity, climate, desert tourism, natural beauty, ecotourism, remoteness, peace and quiet and acting as a refuge in an unspoilt natural environment. Amongst other recommendations, this result highlighted the importance of keeping closed the ‘gap’ between the expected product/level of service and the customer’s perception of the actual product/service received, by paying special attention to each of the identified tourist benefits. Most importantly, product owners, local tourism organisations (LTOs), municipalities, the government and all tourism stakeholders need to ensure that they work efficiently and effectively through transparent and collaborative relationships to ensure that they generate the highest possible returns from tourism investment through strategies that take cognizance of the above. The second objective of this dissertation was to quantitatively evaluate the economic impact of tourism through gathering and calculating 107 tourists’ spending data and 15 product owners’ expenditure data over a six month period between December 2010 and May 2011 in Graaff-Reinet. It was found that there was an increase over time in tourist spending, which led to an increase in direct income (net injection of visitor spending) and thus there was an increase in indirect income(affecting the level of product owners’ income)in the Graaff-Reinet economy. The key calculations in this study reflected a high multiplier of 1.2and a small amount of leakage (21%);and the final tourism economic impact of the accommodation sector in Graaff-Reinet wasR8940 982.00. This implies a positive economic contribution to this town. A focus on growing the tourist market is therefore a goal worth pursuing. This study provides up-to-date, statistically valid numerical/quantitative data as well as current qualitative data. However, gathering data for a longitudinal study would be highly beneficial to determine trends of how the tourism market in small towns is developing. This field has been given minimal attention, specifically within small towns. This dissertation was thus an attempt to initiate and motivate further ongoing efforts with regards to gathering, specifically economic, tourism data. Showing the positive economic contribution, and the multiple ripple effects that attracting tourists to an area can have, and the ultimate measurable economic benefit created through having a strong multiplier effect, will hopefully encourage all stakeholders to be confident and take the tourism industry more seriously. This highlights the need to recognise the economic impact potential of the tourism sector and to use the positive results identified in this study as a tool to lobby for tourism investment, which is unfortunately not reflected currently in many governmental programmes. Developing greater co-operation and co-ordination between the private and public sectors is needed: the most appropriate development model for the tourism industry being government led, private sector driven, community based and labour conscious in order for it to reap the benefits reflected in this tourism study. , Thesis (MEcon) -- Faculty of Commerce, Economics and Economic History, 2013
- Full Text:
- Date Issued: 2013-04-06
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
- Full Text:
- Date Issued: 2004-03