>Magister Scientiae - MSc / Gully erosion and headcut migration has been at the crux of wetland degradation in South Africa. The resulting erosion and draining effect has seen more than 50% of wetlands in the country degraded. This study investigated the degradation of indigenous Palmiet, peat forming, wetlands through headcut erosion. This was done by exploring the relationship between headcut migration rate and morphodynamic characteristics through the use of multiple regression analysis. Wetlands investigated in this study occurred in the Kromme River catchment and Nuwejaars River catchment, in the Eastern Cape and Western Cape respectively. Morphodynamic characteristics assessed include headcut dimensions, gully characteristics, soil characteristics and drainage basin characteristics. These parameters were determined either through infield assessment, image analysis or laboratory analysis. Three headcut migration rate types were calculated through a combination of infield measurements and image analysis techniques executed within ArcGIS. These migration rate types include apex advancement (m/a), gully expansion (m2/a) and volume erosion (m3/a). Statistical analysis revealed significant relationships between morphodynamic characteristics and both volume erosion and gully expansion. Morphodynamic characteristics such as drop height, apex width, gully width, drainage rate and sand content were found to have a direct relationship with migration rates, whereas characteristics such as average drainage basin slope, clay content, silt content, SOM content and soil saturation were found to have an indirect relationship with headcut migration rates. Results provide insight into the headcut migration process, its influencing factors and the potential for headcut migration rate prediction. An evaluation of these results using WET-Health found that the wetland management tool captures wetland geomorphic controls to an accuracy of 68% and 70%. Furthermore, the influence of morphodynamic characteristics on migration rates contributes to the wetland rehabilitation process as it allows for the identification of headcut sites most susceptible to erosion. This will then allow for timely wetland rehabilitation, decreasing the rate of net wetland degradation and improving the management and efficiency of wetland restoration.

Petroleum migration pathways through a basin are determined by the three-dimensional distribution of discontinuous sealing surfaces, which are usually parallel to bedding. The petroleum migrates below the sealing surface taking the structurally most advantageous route. The three-dimensional distribution of migration pathways within the petroleum system can be modelled on a personal computer using a program based on the parameters developed during the research summarised in this thesis. Application of the model to the Paris, Williston, West of Shetlands and Wessex Basins demonstrates that a good correlation can be made between predicted pathways and discovered accumulations using simple models. Migration pathways form a dense network overlying hydrocarbon generating areas in the central parts of basins. Towards the basin margins they commonly become increasingly focused into discrete pathways by the sealing-surface morphologies. The Paris and Williston Basin research showed how relatively minor structuring of geological strata can result in a significant focusing of pathways. Eventually these pathways may reach the surface as shown by seepages. Research in the Wessex Basin revealed that reverse modelling of pathways from seeps assists in the prediction of the location of leaking accumulations. Deflection of the pathways from the structurally most advantageous route below the sealing surface may be caused by lateral sealing barriers due to facies variation in the carrier rock below the seal, fault juxtaposition, or cross-formational seals such as salt intrusions. Deflection of pathways also occurs where there are hydrodynamic conditions in response to topography-driven groundwater flow.

O embasamento oceânico representa a situação tectônica de uma determinada área e seu conhecimento é crucial em estudos que visam explorar o fundo marinho. Devido à alta taxa de sedimentação, principalmente em bacias oceânicas, a topografia do embasamento é mascarada e suas estruturas podem estar enterradas, inacessíveis à observação direta. Este trabalho visa estimar a profundidade do embasamento na região da Bacia de Santos a partir de uma análise combinada de dados gravimétricos obtidos a partir de altimetria por satélite e gravimetria marinha, dados batimétricos e modelo de espessura sedimentar de bancos de dados internacionais e dados de espessura crustal disponíveis na região. Na primeira etapa do trabalho foi calculado o efeito do pacote sedimentar no sinal gravimétrico na Bacia de Santos e a profundidade da Interface Crosta Manto (ICM) foi modelada a partir de inversão gravimétrica com vínculos. Na etapa seguinte, a confiabilidade dos modelos obtidos foi testada através de análise flexural. Os dados de profundidade da ICM flexural e gravimétrica se mostraram em concordância, sinalizando a adequação de seu uso na próxima etapa do trabalho. O efeito gravimétrico da ICM encontrada por análise flexural e o efeito gravimétrico dos sedimentos foram então calculados e subtraídos da anomalia Bouguer original. O campo residual assim obtido, que se admite representar as feições topográficas do embasamento, foi invertido na última etapa do trabalho, fornecendo informações que mostram um embasamento com feições topográficas de até 700m em certas regiões isoladas. Este embasamento gravimétrico pode, dentro de suas restrições, oferecer importantes subsídios para a elaboração de modelos genéticos e tectônicos de interesse exploratório na região. / The ocean basement represents the tectonic situation of an specific area and their knowledge is crucial in studies aimed at exploring the seabed. Due to the high sedimentation rate, especially in ocean basins, the topography of the basement is masked and their structures can be buried, inaccessible to direct observation. This paper aims to estimate the depth of the basement in the region of the Santos Basin from a combined analysis of gravity data obtained from satellite altimetry and marine gravimetry, bathymetric data and sediment thickness from international data banks and crustal thickness data available in the region. In the first step of the work it was calculated the gravity effect of sediments in Santos Basin and the Crustal Mantle Interface (CMI) was modeled from constrained gravity inversion. In the next step, the reliability of the models obtained was tested by flexural analysis. The flexural and gravity CMI proved to be in agreement, indicating the appropriateness of its use in the next stage of work. The gravity effect of Flexural CMI and the gravity effect of sediments were then calculated and subtracted from the original Bouguer anomaly. The residual field thus obtained, which is assumed to represent the topographical features of the basement, was inverted in the last step of the work, providing information that show a basement with features of up to 700min some isolated regions. This gravimetric basement may, within its restrictions, offer important insights for the development of genetic and tectonic models off exploration interest in the region.

O embasamento oceânico representa a situação tectônica de uma determinada área e seu conhecimento é crucial em estudos que visam explorar o fundo marinho. Devido à alta taxa de sedimentação, principalmente em bacias oceânicas, a topografia do embasamento é mascarada e suas estruturas podem estar enterradas, inacessíveis à observação direta. Este trabalho visa estimar a profundidade do embasamento na região da Bacia de Santos a partir de uma análise combinada de dados gravimétricos obtidos a partir de altimetria por satélite e gravimetria marinha, dados batimétricos e modelo de espessura sedimentar de bancos de dados internacionais e dados de espessura crustal disponíveis na região. Na primeira etapa do trabalho foi calculado o efeito do pacote sedimentar no sinal gravimétrico na Bacia de Santos e a profundidade da Interface Crosta Manto (ICM) foi modelada a partir de inversão gravimétrica com vínculos. Na etapa seguinte, a confiabilidade dos modelos obtidos foi testada através de análise flexural. Os dados de profundidade da ICM flexural e gravimétrica se mostraram em concordância, sinalizando a adequação de seu uso na próxima etapa do trabalho. O efeito gravimétrico da ICM encontrada por análise flexural e o efeito gravimétrico dos sedimentos foram então calculados e subtraídos da anomalia Bouguer original. O campo residual assim obtido, que se admite representar as feições topográficas do embasamento, foi invertido na última etapa do trabalho, fornecendo informações que mostram um embasamento com feições topográficas de até 700m em certas regiões isoladas. Este embasamento gravimétrico pode, dentro de suas restrições, oferecer importantes subsídios para a elaboração de modelos genéticos e tectônicos de interesse exploratório na região. / The ocean basement represents the tectonic situation of an specific area and their knowledge is crucial in studies aimed at exploring the seabed. Due to the high sedimentation rate, especially in ocean basins, the topography of the basement is masked and their structures can be buried, inaccessible to direct observation. This paper aims to estimate the depth of the basement in the region of the Santos Basin from a combined analysis of gravity data obtained from satellite altimetry and marine gravimetry, bathymetric data and sediment thickness from international data banks and crustal thickness data available in the region. In the first step of the work it was calculated the gravity effect of sediments in Santos Basin and the Crustal Mantle Interface (CMI) was modeled from constrained gravity inversion. In the next step, the reliability of the models obtained was tested by flexural analysis. The flexural and gravity CMI proved to be in agreement, indicating the appropriateness of its use in the next stage of work. The gravity effect of Flexural CMI and the gravity effect of sediments were then calculated and subtracted from the original Bouguer anomaly. The residual field thus obtained, which is assumed to represent the topographical features of the basement, was inverted in the last step of the work, providing information that show a basement with features of up to 700min some isolated regions. This gravimetric basement may, within its restrictions, offer important insights for the development of genetic and tectonic models off exploration interest in the region.

Deltas are important coastal systems throughout the world. River mouth bars are key landforms in the development of deltas, are characterized by sediment deposition, and have high potential for sediment preservation. Scientists and professionals seek to understand the discrete response of mouth bars to the various controls governing their evolution. This study utilizes the numerical modelling software Delft3D to provide additional evidence supporting the morphological and stratigraphic responses resulting from variations in basin configurations and allogenic controls (fluvial discharge, tides, basin width). Mud content within the bar increased analogous to an increase in the tidal modulation, while a decrease in the initial basin depth reduced mud content. Initial basin slope and lateral confinement had less obvious impacts on stratigraphy. Finally, variable fluvial discharge and the incorporation of realistic tidal harmonics produced similar bar morphologies (compared to simulations with constant flow and sinusoidal tides), yet demonstrated significant differences in bar stratigraphy.

The economic efficiency of water development in Utah, including transfer systems, has seldom been examined, nor has the costs of public policies which result in deviations from efficient allocations. In order that public officials be better informed about water allocations , the present effort examines the efficient allocation of water in time frames up to 2020 under several alternative assumptions and calculates the cost of alternative policies. Us ing mathematical programming techniques, a computer mode l is developed to determine the supply (marginal cost) and demand (value of marginal product) relationships for agricultural water, given depletions for municipal and industrial (M & I) and wetland requirements. The model maximizes net profit per acre t o an average agriculturalist in each of ten study areas in Utah. Proposed interbasin transfers and their costs are included in supply. The optimal solution gene rated is an efficient allocation, since maximization of net profits occurs only when value of marginal product equals marginal cost. The requirements for M & I water are projected into the future using trending and probable industrial development. An efficient allocation (optimal solution) is generated by the model f or 1965, 1980, 1990, 2000, 2010, and 20 20. Th e timing of investments in water distribution systems can be determined from these solutions. Using alternative assumptions about policies (minimum inflows to Great Salt Lake and water salvage) several alternative temporal distributions are determined. Additionally, the effect of restrictions on groundwater pumping (present levels of storage must be maintained) are examined. The costs to users in higher supply curves (marginal costs) are approximated by areas between supply curves. In addition, losses to agricultural users from diminished efficient new production can be approximated. The critical factors in large proposed water transfers in Utah appear to be the growth of M & I requirements along the Wasatch Front, particularly in the Jordan River Basin. Sufficient water is available in the Colorado River Basins to provide maximum transfers, full oil shale and power generation development, and efficient agricultural production. Restrictions on groundwater pumping and water salvage in the Jordan River Basin and maintenance of high inflows to Great Salt Lake make transfers necessary sooner. The costs of such restrictions approaches 25 percent of the total investment by agriculture in transfer systems. If no r e strictions are made, but investment in these systems occurs now, a loss of foregone returns to alternative investment equal to about 70 percent of the total agricultural investment is incurred by society.

>Magister Scientiae - MSc / This study investigates the viability of the sedimentary deposits in the Northern Orange basin for carbon storage and sequestration. A combination of geological modelling, petrographic and geochemical techniques are used to investigate this scenario after an initial seismic-well tie had been performed to match the formation tops in Well AF-1 with the 3D seismic volume acquired in this basin in 2009. Core description of well AF-1 assisted in identifying different facies and samples taken at specific depths for petrographic and geochemical analyses, while different geological formations were mapped from the calibrated positions of seismic-well tie throughout the seismic volume. The well data and geophysical logs were utilized to generate petrophysical properties and used to calibrate observations made from seismic interpretations. The facies log used in this study was generated using the Python’s script on Petrel 2014 Gamma Ray, while the density log was used to generate the porosity log. The generated facies and porosity logs were upscaled and used to populate a 3D grid using faults and surfaces identified in the seismic volume. The sedimentological properties of the subsurface were identified utilizing petrographic descriptions including measurements of sorting, colour and grain sizes. While the mineralogical properties of the record was verified through XRD analyses and thin section. The facies and porosity modelling revealed the dominance of siltstones and sandstones as the main sedimentary facies throughout the sequence. Sandstones are extensive and prominent within the Cenozoic and Mastrichtian, while the unit dated to the Barremian is identified as having the best potential for CO2 storage based on the overlaying capping unit. Quartz, Plagioclase feldspar (Albite), Biotite and Kaolinite are the major minerals identified in all four samples. Each of these minerals has an implication for which may influence the long term storage of CO2 with the potential to form as they may form part of the inra-porous post-depositional cementation and hence change the porosity and permeability properties. The presence of Albite as observed on the XRD may predict possible mineralisation of CO2 to form Dawsonite when reservoir is injected with CO2. The Barremian sandstone which straddles the Aptian shale at the top and the Hauterivian Shale and Siltsone deposit at the bottom holds a good promise for a potential CO2 storage. An estimated volume of CO2 that could be stored in the reservoir of the Barremian sandstone in zone 8 is limited to the lateral seal of shale above the reservoir in zone 7 of the Aptian age. The method used to determine the potential storage capacity of CO2 was performed by Alexandros Tasianas and Nikolaos Koukouzas (2016). The Equation used to determine CO2 storage capacity is: mCO2 = RV * Ø * Sg * δ(CO2) . / 2021-09-01

A suite of samples consisting of twenty-two crude oils and eight sedimentary rocks has been analysed for biological marker compounds by GC-MS. The sedimentary rocks are rich in carbonate minerals and the crude oils were reported to have been derived from carbonate source rocks. These samples are from a variety of geographical origins, geological ages and depositional environments. They consistently contain a homologous series of 30-nor-17 [alpha] (H)-hopanes. Seven homologues (C28 - C34) of the 30-nor-17 [alpha](H)-hopane series have been identified. These compounds appear to be useful biological markers for samples having carbonate associations.A series of 25,30-bisnor-17 [alpha] (H)-hopanes has been observed in a severely biodegraded crude oil of probable carbonate origin. This observation, together with the well-established enrichment of normal hopanes demethylated at position 25 in severely biodegraded crude oils, suggests that the presence of this series of hopanes indicates severe biodegradation of crude oils originating from carbonate-rich source rocks.Another series of hopanes which was previously unreported, the 2-methyl-30-nor-1 [alpha] (H)-hopanes, has also been observed in the carbonate samples. Seven members (C29-C35) of this homologous series have been identified in this study. This series appears to be associated with carbonate rocks deposited under extreme reducing conditions.The biological marker compounds in another sample suite comprising twelve sediments and three crude oils from the North Sumatra Basin, Indonesia, have also been analysed by GC-MS as part of a correlation study. Sediment samples classified as shales, carbonaceous shales and calcareous shales have been shown to contain very different biomarkers. These distinctive biomarkers have enabled the source characteristics of the crude oils to be inferred. Two crude oils have been recognised ++ / with similar biomarker characteristics to the shales and one crude oil has the characteristics of the calcareous shale. The distinctive features of the carbonaceous shale were not observed in the crude oils. This study therefore provides an excellent example of how the 30-nor-17 [alpha] (H)-hopane compounds can be useful in oil-source rock correlation studies.

Bibliography: 80-82. Electronic publication; full text available in PDF format; abstract in HTML format. The process of calibrating a numerical model is examined in this thesis with an application to the flow of groundwater in the Willunga Basin in South Australia. The calibration process involves estimating unknown parameters of the numerical model so that the output obtained from the model is comparable with data that is observed in the field. Three methods for calibrating numerical models are discussed, these being the steepest descent method, the nonlinear least squares method, and a new method called the response function method. Electronic reproduction.[Australia] :Australian Digital Theses Program,2001.

Addendum on back page. Includes bibliography. Groundwater levels within the Willunga Basin, South Australia, are declining due to excessive extraction of water for irrigation purposes. An alternative source of water is needed to supplement the declining levels to ensure the sustainability of the groundwater system. A model was developed to evaluate the potential for using aquifer storage and recovery in conjunction with the surface storage of streamflow as a possible alternative water source. The application of this model to the largest catchment in the Willinga basin shows that sufficient streamflow is available to reverse the current overexploitation of the groundwater system.