159 leaves : ill., app'ces / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1967

Landscape evolution is important for mineral and petroleum exploration concepts, especially in dryland continental settings. This study seeks to understand the main issues and controls on landscape evolution that have produced the regolith and young sediments around the western side of Lake Eye, in the arid heart of Australia. Several methods were employed including satellite image analysis, geomorphometry, geological mapping, regolith mapping and surveying. Outcomes indicate that the underlying structural fabric of the basement has controlled the development of the surface morphology of the Umbum Creek Catchment. The arrangement of basement faults is reflected in the distribution of surface landforms and in the topography of the land surface. Significant deformation of the Etadunna and Eyre formations indicate tectonic activity occurred at the end of the Miocene and was probably related to movement in the Lake Eyre Fault Zone. Pleistocene faulting is expressed as minor blind faulting associated with pre - existing basement faults. These faults remain active and current seismic activity is driven by changes in hydrostatic pressure (hydroseismicity). The scale of Pleistocene faulting and modern seismic activity demonstrates that since the Pliocene tectonic activity has been subdued. Climate change caused landforms developed under wet conditions during the Palaeogene and Neogene to be preserved by the development of aridity in the Pleistocene. High erosion rates associated with tectonism and the onset of aridity in the Pleistocene led to topographic inversion of many features. Palaeo-Proterozoic inliers formed inselbergs, silcrete outcrops formed capstones, gypsum hardpans protected underlying sediment from erosion creating plateaux of gypsum patterned ground and palaeo-channels on the Neales Fan were eroded to make heavily armoured mounds and associated sand dunes and sand sheets. The dominant factor influencing the evolution of the landscape in the Umbum Creek Catchment was the deposition of sedimentary sulphides within the Bulldog Shale. The excess sulphur that this sediment supplied to the landscape over time created the necessary conditions for the formation of a range of landscape features that would not otherwise exist. Weathering, oxidation and leaching of the sedimentary sulphides led to the development of silcrete. Subsequent weathering and tectonic activity led to the breakdown of the silcrete and the distribution of silcrete pebbles widely across the landscape forming gibber plains. Sulphur from the Bulldog Shale continued to contribute to the landscape forming intra-formational gypsum and precipitating as gypsum hardpans. This study has implications for petroleum exploration in dryland continental settings as potential reservoirs may be affected by secondary diagenetic processes, such as the formation of gypsum or silcretes, that could act as baffles or result in reduced porosity within the reservoir. The broad-scale architecture of fluvial systems, like the Neales Fan, may not conform to traditional fan-shaped models being, instead, comprised of structurally rearranged channels. In terms of earthquake risk assessment, the identification of hydroseismicity active within the Lake Eye Basin allows for a new level of predictability of earthquake behaviour within Central Australia. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1260856 / Thesis (Ph.D.) -- School of Earth and Environmental Sciences, 2006

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Landscape evolution is important for mineral and petroleum exploration concepts, especially in dryland continental settings. This study seeks to understand the main issues and controls on landscape evolution that have produced the regolith and young sediments around the western side of Lake Eye, in the arid heart of Australia. Several methods were employed including satellite image analysis, geomorphometry, geological mapping, regolith mapping and surveying. Outcomes indicate that the underlying structural fabric of the basement has controlled the development of the surface morphology of the Umbum Creek Catchment. The arrangement of basement faults is reflected in the distribution of surface landforms and in the topography of the land surface. Significant deformation of the Etadunna and Eyre formations indicate tectonic activity occurred at the end of the Miocene and was probably related to movement in the Lake Eyre Fault Zone. Pleistocene faulting is expressed as minor blind faulting associated with pre - existing basement faults. These faults remain active and current seismic activity is driven by changes in hydrostatic pressure (hydroseismicity). The scale of Pleistocene faulting and modern seismic activity demonstrates that since the Pliocene tectonic activity has been subdued. Climate change caused landforms developed under wet conditions during the Palaeogene and Neogene to be preserved by the development of aridity in the Pleistocene. High erosion rates associated with tectonism and the onset of aridity in the Pleistocene led to topographic inversion of many features. Palaeo-Proterozoic inliers formed inselbergs, silcrete outcrops formed capstones, gypsum hardpans protected underlying sediment from erosion creating plateaux of gypsum patterned ground and palaeo-channels on the Neales Fan were eroded to make heavily armoured mounds and associated sand dunes and sand sheets. The dominant factor influencing the evolution of the landscape in the Umbum Creek Catchment was the deposition of sedimentary sulphides within the Bulldog Shale. The excess sulphur that this sediment supplied to the landscape over time created the necessary conditions for the formation of a range of landscape features that would not otherwise exist. Weathering, oxidation and leaching of the sedimentary sulphides led to the development of silcrete. Subsequent weathering and tectonic activity led to the breakdown of the silcrete and the distribution of silcrete pebbles widely across the landscape forming gibber plains. Sulphur from the Bulldog Shale continued to contribute to the landscape forming intra-formational gypsum and precipitating as gypsum hardpans. This study has implications for petroleum exploration in dryland continental settings as potential reservoirs may be affected by secondary diagenetic processes, such as the formation of gypsum or silcretes, that could act as baffles or result in reduced porosity within the reservoir. The broad-scale architecture of fluvial systems, like the Neales Fan, may not conform to traditional fan-shaped models being, instead, comprised of structurally rearranged channels. In terms of earthquake risk assessment, the identification of hydroseismicity active within the Lake Eye Basin allows for a new level of predictability of earthquake behaviour within Central Australia. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1260856 / Thesis (Ph.D.) -- School of Earth and Environmental Sciences, 2006

This thesis consists of six published papers. The present-day stress tensor has been determined using petroleum well data in the Gippsland and Otway Basins in Southeast Australia (Papers 1 and 4) and the Cooper Basin in Central Australia (Paper 5). In the Gippsland Basin, the present-day stress regime is transitional between one of reverse and strike-slip faulting and the maximum horizontal stress (SHmax) is oriented ~139°N. The present-day stress regime in the Victorian sector of the Otway Basin is also transitional between one of reverse and strike-slip faulting and SHmax is oriented ~135°N. Horizontal stresses are lower in the South Australian sector of the Otway Basin where the stress regime is one of strike-slip faulting and SHmax is oriented ~124°N. The orientations of SHmax in Southeast Australia are consistent with focal mechanism solutions, neotectonic structures and modelling of plate-boundary forces (Paper 4). Closure pressures from mini-frac injection tests are commonly used to determine the minimum horizontal stress (Shmin) magnitude. However, in high stress basins such as the Cooper and Gippsland Basins, these pressures may not reliably yield Shmin (Papers 2 and 5). In the Cooper Basin, high closure pressures (>18 MPa/km) were observed in tests where pressure-declines indicated complex hydraulic fracture growth. Closure pressures in these injections are unlikely to be representative of Shmin. They are believed to reflect the normal stress incident on pre-existing planes of weakness that are exploited by hydraulic fluid during the mini-frac injection (Paper 5). Sub-horizontal fabrics that are open at the wellbore wall were observed on image logs in the Cooper and Gippsland Basins (Papers 2 and 5). This fabric is believed to be at least partially responsible for the complex growth of hydraulic fractures observed in the Cooper Basin. The occurrence of these sub-horizontal fabrics and knowledge of rock strength have been used to constrain the magnitudes of SHmax and Shmin independently of mini-frac injections in the Cooper and Gippsland Basins (Papers 2 and 5). The present-day stress tensor is often quoted as a single gradient at a sedimentary basinor petroleum field-scale. Image logs and mini-frac data from Central and Southeast Australia indicate significant stress differences between stratigraphic units (Papers 3 and 5). Finite element modelling of the stress distribution between interbedded sands and shales in the Gippsland Basin indicates that stress is ‘partitioned’ to ‘hard’ lithological units in high stress areas. This accounts for the observation that borehole breakout only occurs in hard, cemented sandstones in the Gippsland Basin (Paper 3). A generic ‘mechanical stratigraphy’ derived from knowledge of wellbore failure (from image logs), rock strength and rock properties in individual rock units in the Cooper Basin allows an approximation of the present-day stress-state to be made directly from image-logs for individual rock units prior to mini-frac injection (Paper 6). This is important for predicting and understanding hydraulic fracture growth and containment. When considered together, the papers comprising this thesis provide significant new data on the orientation and magnitude of present-day stresses in Central and Southeast Australia. They also provide insight into the tectonic origin of those stresses and their distribution within sedimentary basins. In particular the papers develop and use new methods for constraining the present-day stress in regions of high tectonic stress. They also discuss implications for problems in petroleum development including wellbore stability and hydraulic fracturing. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1283781 / Thesis(Ph.D.) -- Australian School of Petroleum, 2007