No description available.

Sedimentary deposits are important aquifers in many parts of the world and in order to explore, develop and manage these aquifers, it is necessary to determine the relationship between the hydrogeologic properties and sedimentary facies (aquifer characterization). Within a sedimentary hydrogeologic system, the environment of deposition and the resulting distribution of grain sizes, texture, and facies associations within different individual aquifer bodies influence variations in hydraulic properties. Successful prediction of the quality of the aquifer is dependent on the accurate mapping of both lithologic units and hydrogeologic parameters. In this project, the influence of petrophysical characteristics of the sedimentary rocks to the quality of the aquifer is investigated with a view to finding a correlation between these characteristics, the type and nature of sedimentary rocks present and their hydrogeologic properties. Investigation methods involved the use of geophysical wireline log data, lithological core logging, thin section microscopy and X-Ray Diffraction analysis. All this was done to characterize the sedimentary rocks in terms of composition, grain size and diagenesis. Porosity tests were also performed on the samples collected while permeability data was collected from the Department of Natural Resources and Mines (DNR & M), Australia. The basins of interest for this project are the Bowen Basin in Australia and the Kalahari Basin in Botswana. The two basins are similar, though structurally different. The basins are similar in the sense that they have got similarity in their rock sequence. All the work done on the Bowen Basin and the results obtained are extrapolated to the similar Kalahari Basin. The units of the Bowen Basin are underlain by the Late Carboniferous to Early Permian Camboon Volcanics. The Permian units include the Buffel, Barfield, Flat Top, and Gyranda Formations and the Baralaba Coal Measures. The Triassic units are the Rewan Group, Clematis Sandstone and Moolayember Formation. Within the Bowen Basin the Permian units are generally argillaceous and therefore have generally low porosities and permeabilities and also give low resistivity (RES) base lines and high gamma ray (GR) baselines. However where fractured, the units yield some water from the shale. Boreholes drawing water from the Barfield, Flat Top and Gyranda Formations tap the fractured shales. The Triassic aquifers present a different picture. The best aquifers with high porosities and permeabilities are of the Triassic age and their distribution is influenced by their proximity to the source area. Sedimentary rocks of the Triassic age in the Bowen Basin become more argillaceous at more distal positions from the source area. The Rewan Group in particular shows this trend and hence better aquifers within the Rewan are those close to the source area. The Kalahari Basin Karoo stratigraphy commences with the Late Carboniferous to Early Permian glaciogenic sedimentary rocks of the Dwyka Group. The Dwyka Group is overlain by the argillaceous Permian to Early Triassic sedimentary rocks of The Ecca Group and the Beaufort Group. Overlying the Beaufort Group is the Lebung Group (lower Mosolotsane Formation-dominantly mudstone and siltstone sequence and upper Ntane Sandstone Formation- aeolian sandstone). Basaltic lavas of the stormberg Lava Group cap the Karoo stratigraphy. Few groundwater studies in the Karoo of the Kalahari Basin have shown that the Ecca Group does not posses good aquifer characteristics because of its argillaceous nature. However, thin arenaceous interbeds within the Ecca Group have yielded some groundwater. Non-measurable quantities of groundwater have been recorded from boreholes sunk in the Beaufort Group. Few boreholes penetrating the Mosolotsane Formation yielded very little groundwater whereas Ntane Sandstone have yielded a fair amount of groundwater. Groundwater yield from the Stormberg Lava Group is related to the presence of fractures.

Sedimentary deposits are important aquifers in many parts of the world and in order to explore, develop and manage these aquifers, it is necessary to determine the relationship between the hydrogeologic properties and sedimentary facies (aquifer characterization). Within a sedimentary hydrogeologic system, the environment of deposition and the resulting distribution of grain sizes, texture, and facies associations within different individual aquifer bodies influence variations in hydraulic properties. Successful prediction of the quality of the aquifer is dependent on the accurate mapping of both lithologic units and hydrogeologic parameters. In this project, the influence of petrophysical characteristics of the sedimentary rocks to the quality of the aquifer is investigated with a view to finding a correlation between these characteristics, the type and nature of sedimentary rocks present and their hydrogeologic properties. Investigation methods involved the use of geophysical wireline log data, lithological core logging, thin section microscopy and X-Ray Diffraction analysis. All this was done to characterize the sedimentary rocks in terms of composition, grain size and diagenesis. Porosity tests were also performed on the samples collected while permeability data was collected from the Department of Natural Resources and Mines (DNR & M), Australia. The basins of interest for this project are the Bowen Basin in Australia and the Kalahari Basin in Botswana. The two basins are similar, though structurally different. The basins are similar in the sense that they have got similarity in their rock sequence. All the work done on the Bowen Basin and the results obtained are extrapolated to the similar Kalahari Basin. The units of the Bowen Basin are underlain by the Late Carboniferous to Early Permian Camboon Volcanics. The Permian units include the Buffel, Barfield, Flat Top, and Gyranda Formations and the Baralaba Coal Measures. The Triassic units are the Rewan Group, Clematis Sandstone and Moolayember Formation. Within the Bowen Basin the Permian units are generally argillaceous and therefore have generally low porosities and permeabilities and also give low resistivity (RES) base lines and high gamma ray (GR) baselines. However where fractured, the units yield some water from the shale. Boreholes drawing water from the Barfield, Flat Top and Gyranda Formations tap the fractured shales. The Triassic aquifers present a different picture. The best aquifers with high porosities and permeabilities are of the Triassic age and their distribution is influenced by their proximity to the source area. Sedimentary rocks of the Triassic age in the Bowen Basin become more argillaceous at more distal positions from the source area. The Rewan Group in particular shows this trend and hence better aquifers within the Rewan are those close to the source area. The Kalahari Basin Karoo stratigraphy commences with the Late Carboniferous to Early Permian glaciogenic sedimentary rocks of the Dwyka Group. The Dwyka Group is overlain by the argillaceous Permian to Early Triassic sedimentary rocks of The Ecca Group and the Beaufort Group. Overlying the Beaufort Group is the Lebung Group (lower Mosolotsane Formation-dominantly mudstone and siltstone sequence and upper Ntane Sandstone Formation- aeolian sandstone). Basaltic lavas of the stormberg Lava Group cap the Karoo stratigraphy. Few groundwater studies in the Karoo of the Kalahari Basin have shown that the Ecca Group does not posses good aquifer characteristics because of its argillaceous nature. However, thin arenaceous interbeds within the Ecca Group have yielded some groundwater. Non-measurable quantities of groundwater have been recorded from boreholes sunk in the Beaufort Group. Few boreholes penetrating the Mosolotsane Formation yielded very little groundwater whereas Ntane Sandstone have yielded a fair amount of groundwater. Groundwater yield from the Stormberg Lava Group is related to the presence of fractures.

No description available.

Sedimentary deposits are important aquifers in many parts of the world and in order to explore, develop and manage these aquifers, it is necessary to determine the relationship between the hydrogeologic properties and sedimentary facies (aquifer characterization). Within a sedimentary hydrogeologic system, the environment of deposition and the resulting distribution of grain sizes, texture, and facies associations within different individual aquifer bodies influence variations in hydraulic properties. Successful prediction of the quality of the aquifer is dependent on the accurate mapping of both lithologic units and hydrogeologic parameters. In this project, the influence of petrophysical characteristics of the sedimentary rocks to the quality of the aquifer is investigated with a view to finding a correlation between these characteristics, the type and nature of sedimentary rocks present and their hydrogeologic properties. Investigation methods involved the use of geophysical wireline log data, lithological core logging, thin section microscopy and X-Ray Diffraction analysis. All this was done to characterize the sedimentary rocks in terms of composition, grain size and diagenesis. Porosity tests were also performed on the samples collected while permeability data was collected from the Department of Natural Resources and Mines (DNR & M), Australia. The basins of interest for this project are the Bowen Basin in Australia and the Kalahari Basin in Botswana. The two basins are similar, though structurally different. The basins are similar in the sense that they have got similarity in their rock sequence. All the work done on the Bowen Basin and the results obtained are extrapolated to the similar Kalahari Basin. The units of the Bowen Basin are underlain by the Late Carboniferous to Early Permian Camboon Volcanics. The Permian units include the Buffel, Barfield, Flat Top, and Gyranda Formations and the Baralaba Coal Measures. The Triassic units are the Rewan Group, Clematis Sandstone and Moolayember Formation. Within the Bowen Basin the Permian units are generally argillaceous and therefore have generally low porosities and permeabilities and also give low resistivity (RES) base lines and high gamma ray (GR) baselines. However where fractured, the units yield some water from the shale. Boreholes drawing water from the Barfield, Flat Top and Gyranda Formations tap the fractured shales. The Triassic aquifers present a different picture. The best aquifers with high porosities and permeabilities are of the Triassic age and their distribution is influenced by their proximity to the source area. Sedimentary rocks of the Triassic age in the Bowen Basin become more argillaceous at more distal positions from the source area. The Rewan Group in particular shows this trend and hence better aquifers within the Rewan are those close to the source area. The Kalahari Basin Karoo stratigraphy commences with the Late Carboniferous to Early Permian glaciogenic sedimentary rocks of the Dwyka Group. The Dwyka Group is overlain by the argillaceous Permian to Early Triassic sedimentary rocks of The Ecca Group and the Beaufort Group. Overlying the Beaufort Group is the Lebung Group (lower Mosolotsane Formation-dominantly mudstone and siltstone sequence and upper Ntane Sandstone Formation- aeolian sandstone). Basaltic lavas of the stormberg Lava Group cap the Karoo stratigraphy. Few groundwater studies in the Karoo of the Kalahari Basin have shown that the Ecca Group does not posses good aquifer characteristics because of its argillaceous nature. However, thin arenaceous interbeds within the Ecca Group have yielded some groundwater. Non-measurable quantities of groundwater have been recorded from boreholes sunk in the Beaufort Group. Few boreholes penetrating the Mosolotsane Formation yielded very little groundwater whereas Ntane Sandstone have yielded a fair amount of groundwater. Groundwater yield from the Stormberg Lava Group is related to the presence of fractures.

Sedimentary deposits are important aquifers in many parts of the world and in order to explore, develop and manage these aquifers, it is necessary to determine the relationship between the hydrogeologic properties and sedimentary facies (aquifer characterization). Within a sedimentary hydrogeologic system, the environment of deposition and the resulting distribution of grain sizes, texture, and facies associations within different individual aquifer bodies influence variations in hydraulic properties. Successful prediction of the quality of the aquifer is dependent on the accurate mapping of both lithologic units and hydrogeologic parameters. In this project, the influence of petrophysical characteristics of the sedimentary rocks to the quality of the aquifer is investigated with a view to finding a correlation between these characteristics, the type and nature of sedimentary rocks present and their hydrogeologic properties. Investigation methods involved the use of geophysical wireline log data, lithological core logging, thin section microscopy and X-Ray Diffraction analysis. All this was done to characterize the sedimentary rocks in terms of composition, grain size and diagenesis. Porosity tests were also performed on the samples collected while permeability data was collected from the Department of Natural Resources and Mines (DNR & M), Australia. The basins of interest for this project are the Bowen Basin in Australia and the Kalahari Basin in Botswana. The two basins are similar, though structurally different. The basins are similar in the sense that they have got similarity in their rock sequence. All the work done on the Bowen Basin and the results obtained are extrapolated to the similar Kalahari Basin. The units of the Bowen Basin are underlain by the Late Carboniferous to Early Permian Camboon Volcanics. The Permian units include the Buffel, Barfield, Flat Top, and Gyranda Formations and the Baralaba Coal Measures. The Triassic units are the Rewan Group, Clematis Sandstone and Moolayember Formation. Within the Bowen Basin the Permian units are generally argillaceous and therefore have generally low porosities and permeabilities and also give low resistivity (RES) base lines and high gamma ray (GR) baselines. However where fractured, the units yield some water from the shale. Boreholes drawing water from the Barfield, Flat Top and Gyranda Formations tap the fractured shales. The Triassic aquifers present a different picture. The best aquifers with high porosities and permeabilities are of the Triassic age and their distribution is influenced by their proximity to the source area. Sedimentary rocks of the Triassic age in the Bowen Basin become more argillaceous at more distal positions from the source area. The Rewan Group in particular shows this trend and hence better aquifers within the Rewan are those close to the source area. The Kalahari Basin Karoo stratigraphy commences with the Late Carboniferous to Early Permian glaciogenic sedimentary rocks of the Dwyka Group. The Dwyka Group is overlain by the argillaceous Permian to Early Triassic sedimentary rocks of The Ecca Group and the Beaufort Group. Overlying the Beaufort Group is the Lebung Group (lower Mosolotsane Formation-dominantly mudstone and siltstone sequence and upper Ntane Sandstone Formation- aeolian sandstone). Basaltic lavas of the stormberg Lava Group cap the Karoo stratigraphy. Few groundwater studies in the Karoo of the Kalahari Basin have shown that the Ecca Group does not posses good aquifer characteristics because of its argillaceous nature. However, thin arenaceous interbeds within the Ecca Group have yielded some groundwater. Non-measurable quantities of groundwater have been recorded from boreholes sunk in the Beaufort Group. Few boreholes penetrating the Mosolotsane Formation yielded very little groundwater whereas Ntane Sandstone have yielded a fair amount of groundwater. Groundwater yield from the Stormberg Lava Group is related to the presence of fractures.

The Mount Isa and May Downs Faults are part of a network of significant faults that define, control, or partition deformation in the Early to mid-Proterozoic Mount Isa Inlier. The middle Proterozoic deformation history includes at least two extensional basin-forming events (Leichhardt Superbasin: ~1800 Ma to ~1700 Ma and Isa Superbasin: ~1700 Ma to ~ 1600 Ma) and a major protracted contractional orogenic event (Isan Orogeny: ~1585 Ma to ~ 1500 Ma). Uplift between the Mount Isa and May Downs Faults during the Isan Orogeny has exposed mid to upper amphibolite facies rocks of the structurally deeper levels of the early rift systems. Also exposed is the Sybella Granite, a composite batholith of variably deformed gneissic granite, which, at ~1660 Ma, is broadly coeval with inception of the Isan Superbasin basin. Two prevailing kinematic models had been proposed for the fault systems during Isan Superbasin formation. The traditionally accepted model involves episodic E-W or NW-SE extension with the N-S Mount Isa Fault, but Southgate et al (2000b) presented an alternative sinistral strike-slip model in which the May Downs Fault acted as a releasing bend fault associated with motion on the Mt Isa Fault. In the Southgate model, the Sybella Granite was interpreted as syn-tectonically filling the dilational releasing bend. This study provides a detailed structural analysis of the 100 km by 40 km area west of Mount Isa City lying between the Mount Isa and May Downs Faults. The aim was to resolve a number of outstanding issues, including those outlined above. The resultant 1:250 000 structural map of the area is based on: reconnaissance-scale mapping; aerial photography, satellite, magnetic and radiometric image interpretation; field observations at locations throughout the area; and local detailed mapping (1:12000 scale or less). The mapping and associated geometrical analysis of the area has shown that the Sybella Batholith consists of two granite sills and a more globular body of microgranite. The deepest, gneissic, sill is up to 5 km thick and was emplaced at about 15 km below the basal Mount Isa Group unconformity (palaeosurface). The other, less deformed, sill formed higher in the crust, and the microgranite intruded to within 1-2 km of the palaeosurface. The two sills are located between two major fault systems (Mount Isa and May Downs Faults) that developed from inherited basin margin faults. The fault systems dip toward each other and the rocks between them have been folded into a single large antiform and uplifted as a wedge. Previous interpretations of the area have suggested that the batholith consists of a single sill folded by tighter, shorter wavelength folds. A cross-sectional reconstruction of the study area suggests that thin-skinned processes dominated much of the Isan Orogeny, contrary to previous interpretations. A three-dimensional reconstruction of the area, evaluated by comparing the predicted strain and amount of shortening with measured strain and shortening estimates, suggests deformation was driven by a rigid block to the west of the May Downs Fault moving toward the northeast. In the restored pre-Isan geometry, both the margins of the lowermost gneissic granite sill and its immediate country rocks have a strong, horizontal, layer-parallel, shear foliation with top-to-the-east asymmetry. The fabrics are strongly constrictional and 2 Abstract the stretching lineation trends east-west. Field observations and thin sectional analysis of these fabrics provide positive evidence that the Sybella Batholith was syn-tectonically emplaced in a basin-forming environment. A kinematic model is presented to show that these features are consistent with granite emplacement into a dilational jog in a sub-horizontal shear zone with a top-to-the-east shear sense. A component of east-west directed horizontal simple shear across the dilating zone explains the strongly constrictional fabrics in the granite. Under these conditions significant north-south shortening in the deforming zone leads to the initiation of folds parallel to the stretching direction (as observed). The shear zone into which the granite was emplaced developed at about fifteen kilometres depth and was probably at or near the brittle-ductile transition. The consistent shear sense, very high strains and implied 30 km of translation required to accommodate the sill indicates that this was a major crustal structure, rather than a simple detachment at the brittle-ductile transition in a crustal pure shear extension. The results are consistent with the east-west extensional model for basin development and totally inconsistent with the sinistral strike-slip model.

The Mount Isa and May Downs Faults are part of a network of significant faults that define, control, or partition deformation in the Early to mid-Proterozoic Mount Isa Inlier. The middle Proterozoic deformation history includes at least two extensional basin-forming events (Leichhardt Superbasin: ~1800 Ma to ~1700 Ma and Isa Superbasin: ~1700 Ma to ~ 1600 Ma) and a major protracted contractional orogenic event (Isan Orogeny: ~1585 Ma to ~ 1500 Ma). Uplift between the Mount Isa and May Downs Faults during the Isan Orogeny has exposed mid to upper amphibolite facies rocks of the structurally deeper levels of the early rift systems. Also exposed is the Sybella Granite, a composite batholith of variably deformed gneissic granite, which, at ~1660 Ma, is broadly coeval with inception of the Isan Superbasin basin. Two prevailing kinematic models had been proposed for the fault systems during Isan Superbasin formation. The traditionally accepted model involves episodic E-W or NW-SE extension with the N-S Mount Isa Fault, but Southgate et al (2000b) presented an alternative sinistral strike-slip model in which the May Downs Fault acted as a releasing bend fault associated with motion on the Mt Isa Fault. In the Southgate model, the Sybella Granite was interpreted as syn-tectonically filling the dilational releasing bend. This study provides a detailed structural analysis of the 100 km by 40 km area west of Mount Isa City lying between the Mount Isa and May Downs Faults. The aim was to resolve a number of outstanding issues, including those outlined above. The resultant 1:250 000 structural map of the area is based on: reconnaissance-scale mapping; aerial photography, satellite, magnetic and radiometric image interpretation; field observations at locations throughout the area; and local detailed mapping (1:12000 scale or less). The mapping and associated geometrical analysis of the area has shown that the Sybella Batholith consists of two granite sills and a more globular body of microgranite. The deepest, gneissic, sill is up to 5 km thick and was emplaced at about 15 km below the basal Mount Isa Group unconformity (palaeosurface). The other, less deformed, sill formed higher in the crust, and the microgranite intruded to within 1-2 km of the palaeosurface. The two sills are located between two major fault systems (Mount Isa and May Downs Faults) that developed from inherited basin margin faults. The fault systems dip toward each other and the rocks between them have been folded into a single large antiform and uplifted as a wedge. Previous interpretations of the area have suggested that the batholith consists of a single sill folded by tighter, shorter wavelength folds. A cross-sectional reconstruction of the study area suggests that thin-skinned processes dominated much of the Isan Orogeny, contrary to previous interpretations. A three-dimensional reconstruction of the area, evaluated by comparing the predicted strain and amount of shortening with measured strain and shortening estimates, suggests deformation was driven by a rigid block to the west of the May Downs Fault moving toward the northeast. In the restored pre-Isan geometry, both the margins of the lowermost gneissic granite sill and its immediate country rocks have a strong, horizontal, layer-parallel, shear foliation with top-to-the-east asymmetry. The fabrics are strongly constrictional and 2 Abstract the stretching lineation trends east-west. Field observations and thin sectional analysis of these fabrics provide positive evidence that the Sybella Batholith was syn-tectonically emplaced in a basin-forming environment. A kinematic model is presented to show that these features are consistent with granite emplacement into a dilational jog in a sub-horizontal shear zone with a top-to-the-east shear sense. A component of east-west directed horizontal simple shear across the dilating zone explains the strongly constrictional fabrics in the granite. Under these conditions significant north-south shortening in the deforming zone leads to the initiation of folds parallel to the stretching direction (as observed). The shear zone into which the granite was emplaced developed at about fifteen kilometres depth and was probably at or near the brittle-ductile transition. The consistent shear sense, very high strains and implied 30 km of translation required to accommodate the sill indicates that this was a major crustal structure, rather than a simple detachment at the brittle-ductile transition in a crustal pure shear extension. The results are consistent with the east-west extensional model for basin development and totally inconsistent with the sinistral strike-slip model.