A study of the southwestern Karoo basin in South Africa using magnetic and gravity data
- Authors: Nxantsiya, Zusakhe
- Date: 2017
- Subjects: Groundwater -- South Africa -- Karoo Aquifers -- South Africa -- Karoo Hydrology -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10353/4748 , vital:28509
- Description: The early efforts of Booth, Johnson, Rubidge, Catuneanu, de Wit, Chevallier, Stankiewicz, Weckmann and many other scientists in studying the Karoo Supergroup has led to comprehensive documentation of the geology on the main Karoo Basin with regards to understanding the age, sedimentology, sedimentary facies and depositional environments. In spite of these studies, the subsurface structure, variations in thickness of various formations in large parts of the basin, the location and orientation of subsurface dolerite intrusions, and the depth to magnetic and gravity sources remains poorly documented. A geological study with the aid of geophysical techniques, magnetic and gravity, was conducted in the southwestern part of the main Karoo Basin. The objectives of the study were to construct numerous models of the main basin that image the crust to a depth of 45 km, to determine thicknesses of various formations, to relate observed geophysical anomalies with geological bodies and lineaments, to estimate the depth of existing anomalous bodies, to determine densities and porosity of various formations, as well as to determine the mineralogy of various rocks in the Karoo Basin.
- Full Text:
- Date Issued: 2017
- Authors: Nxantsiya, Zusakhe
- Date: 2017
- Subjects: Groundwater -- South Africa -- Karoo Aquifers -- South Africa -- Karoo Hydrology -- South Africa -- Karoo
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10353/4748 , vital:28509
- Description: The early efforts of Booth, Johnson, Rubidge, Catuneanu, de Wit, Chevallier, Stankiewicz, Weckmann and many other scientists in studying the Karoo Supergroup has led to comprehensive documentation of the geology on the main Karoo Basin with regards to understanding the age, sedimentology, sedimentary facies and depositional environments. In spite of these studies, the subsurface structure, variations in thickness of various formations in large parts of the basin, the location and orientation of subsurface dolerite intrusions, and the depth to magnetic and gravity sources remains poorly documented. A geological study with the aid of geophysical techniques, magnetic and gravity, was conducted in the southwestern part of the main Karoo Basin. The objectives of the study were to construct numerous models of the main basin that image the crust to a depth of 45 km, to determine thicknesses of various formations, to relate observed geophysical anomalies with geological bodies and lineaments, to estimate the depth of existing anomalous bodies, to determine densities and porosity of various formations, as well as to determine the mineralogy of various rocks in the Karoo Basin.
- Full Text:
- Date Issued: 2017
Factors that influence smallholder farmers maize varietal choice: the case of Mhlontlo Local Municipality Eastern Cape
- Authors: Nkohla, Siviwe
- Date: 2016
- Subjects: Agricultural productivity , Farms, Small -- South Africa -- Eastern Cape , Agriculture extension work -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10353/3121 , vital:28263
- Description: In South Africa, maize is grown all over the country under various environments including both dry and irrigated agriculture. The majority of maize farmers are smallholders farming on small pieces of land with low input technologies. Additionally, South Africa`s smallholder maize farmers are characterised by low maize productivity, this is despite of the availability of many improved maize varieties on the market. It is clear that professional maize breeders are continuously developing many superior maize varieties with traits more suitable for the commercial farming sector than the smallholder sector. Against this background, this study used a descriptive statistics approach to find out maize varieties and traits preferred by smallholder farmers. The study also evaluated factors that influence smallholder farmers` maize varietal selection choice using descriptive statistics and multinomial regression. The data used for the empirical analysis was obtained from a survey of 200 smallholder farmers in Mhlontlo Local Municipality, in the Eastern Cape Province of South Africa.
- Full Text:
- Date Issued: 2016
- Authors: Nkohla, Siviwe
- Date: 2016
- Subjects: Agricultural productivity , Farms, Small -- South Africa -- Eastern Cape , Agriculture extension work -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10353/3121 , vital:28263
- Description: In South Africa, maize is grown all over the country under various environments including both dry and irrigated agriculture. The majority of maize farmers are smallholders farming on small pieces of land with low input technologies. Additionally, South Africa`s smallholder maize farmers are characterised by low maize productivity, this is despite of the availability of many improved maize varieties on the market. It is clear that professional maize breeders are continuously developing many superior maize varieties with traits more suitable for the commercial farming sector than the smallholder sector. Against this background, this study used a descriptive statistics approach to find out maize varieties and traits preferred by smallholder farmers. The study also evaluated factors that influence smallholder farmers` maize varietal selection choice using descriptive statistics and multinomial regression. The data used for the empirical analysis was obtained from a survey of 200 smallholder farmers in Mhlontlo Local Municipality, in the Eastern Cape Province of South Africa.
- Full Text:
- Date Issued: 2016
Assessment of the effects of stream channel incision on soil water levels, soil morphology and vegetation in a wetland in the Hogsback area, Eastern Cape, South Africa
- Authors: Omar, Mohamed Yussuf
- Date: 2015
- Subjects: Hydrology Wetland Soil Formation
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10353/3132 , vital:28264
- Description: Wetland degradation in the form of channel incisioning can significantly alter the hydrological functioning of a wetland. In this study in a small headwater wetland in the Hogsback area, Eastern Cape Province, the impact of channel incisioning on soil water levels and soil morphology was examined. A good correlation (R2 = 0.89) exists between the depth of channel incisioning and average water table depths in most of the 21 installed piezometers. In localised cases the upslope supply of water was in equilibrium with drainage from the piezometers. Although all the studied soils show hydromorphic characteristics, those continuously saturated close to the surface exhibit redox accumulations in oxygen supplying macropores, whereas gleyic colour patterns occur deeper in soils where the water table has been lowered by channel incision. The nature and occurrence of different hydromorphic soil indicators observed confirm the contribution of soil morphology as a valuable indicator of long-term average soil water conditions. The study evaluates the effects of hydrological processes on plant species composition and distribution in a Hogsback wetland. Twenty-four circular plots with a radius of 2 m were established between March and August 2013. Within each sample plot, the habitat information and species present were recorded including Braun-Blanquet cover-abundance value for each and every species present in the plot. Plant species were identified in the field and the unknown plant species were collected, pressed, oven-dried and identified at the National Herbarium, South African Biodiversity Institute (SANBI), Pretoria and Schonland Herbarium, Rhodes University, Grahamstown. A total of 39 taxa belonging to 19 families and 34 genera were recorded from the Hogsback wetland. Of the documented taxa, three were exotic and three endemic to South Africa, indicating diversity and dynamic nature of Hogsback wetland flora. Plant families with the highest number of species were: Poaceae (11 species), Asteraceae (5 species), Onagraceae and Cyperaceae with 3 taxa each. The low number of exotic plant species in Hogsback wetland (three taxa in total) indicates limited anthropogenic influence. Unique species recorded in Hogsback wetlands are three species that are endemic to South Africa, namely, Alchemilla capensis, Helichrysum rosum and Lysimachia nutans. Five main floristic associations were identified from the Hierarchical Cluster Analysis whilst Detrenched .Correspondence Analysis (DCA) identified four groups. The Canonical Correspondence Analysis (CCA) indicates that edaphic factors, particularly in an area covered with water, erosion category, organic matter content and water table depth were the most important environmental variables measured accounting for the vegetation pattern present in the Hogsback wetland.
- Full Text:
- Date Issued: 2015
- Authors: Omar, Mohamed Yussuf
- Date: 2015
- Subjects: Hydrology Wetland Soil Formation
- Language: English
- Type: Thesis , Masters , Degree
- Identifier: http://hdl.handle.net/10353/3132 , vital:28264
- Description: Wetland degradation in the form of channel incisioning can significantly alter the hydrological functioning of a wetland. In this study in a small headwater wetland in the Hogsback area, Eastern Cape Province, the impact of channel incisioning on soil water levels and soil morphology was examined. A good correlation (R2 = 0.89) exists between the depth of channel incisioning and average water table depths in most of the 21 installed piezometers. In localised cases the upslope supply of water was in equilibrium with drainage from the piezometers. Although all the studied soils show hydromorphic characteristics, those continuously saturated close to the surface exhibit redox accumulations in oxygen supplying macropores, whereas gleyic colour patterns occur deeper in soils where the water table has been lowered by channel incision. The nature and occurrence of different hydromorphic soil indicators observed confirm the contribution of soil morphology as a valuable indicator of long-term average soil water conditions. The study evaluates the effects of hydrological processes on plant species composition and distribution in a Hogsback wetland. Twenty-four circular plots with a radius of 2 m were established between March and August 2013. Within each sample plot, the habitat information and species present were recorded including Braun-Blanquet cover-abundance value for each and every species present in the plot. Plant species were identified in the field and the unknown plant species were collected, pressed, oven-dried and identified at the National Herbarium, South African Biodiversity Institute (SANBI), Pretoria and Schonland Herbarium, Rhodes University, Grahamstown. A total of 39 taxa belonging to 19 families and 34 genera were recorded from the Hogsback wetland. Of the documented taxa, three were exotic and three endemic to South Africa, indicating diversity and dynamic nature of Hogsback wetland flora. Plant families with the highest number of species were: Poaceae (11 species), Asteraceae (5 species), Onagraceae and Cyperaceae with 3 taxa each. The low number of exotic plant species in Hogsback wetland (three taxa in total) indicates limited anthropogenic influence. Unique species recorded in Hogsback wetlands are three species that are endemic to South Africa, namely, Alchemilla capensis, Helichrysum rosum and Lysimachia nutans. Five main floristic associations were identified from the Hierarchical Cluster Analysis whilst Detrenched .Correspondence Analysis (DCA) identified four groups. The Canonical Correspondence Analysis (CCA) indicates that edaphic factors, particularly in an area covered with water, erosion category, organic matter content and water table depth were the most important environmental variables measured accounting for the vegetation pattern present in the Hogsback wetland.
- Full Text:
- Date Issued: 2015
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