School of Earth Sciences - Theses
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ItemFire weather in two regions of the Southern Hemisphere( 2017)This thesis investigated fire weather in Victoria, Australia and the Ecuadorian Andes. The selection of these areas considered several criteria. First of all, bushfires cause significant impacts in these two regions. Victoria has endured some of the most catastrophic bushfire events in Australian history (e.g. “Black Friday” (1939), “Ash Wednesday” (1983), “Black Saturday” (2009)). On the other hand, bushfires in Ecuador destroy every year large areas of national parks in one of the most biodiverse countries in the world. Secondly, the El Niño- Southern Oscillation (ENSO) is a strong climate driver in the two study areas. Finally, Victoria and Ecuador share the Eucalyptus as the dominant bushfire-prone species. The aim of this thesis is to better understand the drivers and evolution of fire weather in these two regions of the Southern Hemisphere. Specifically, it examined three aspects. First of all, it investigated fire weather spatial patterns in Victoria and their relationship with associated events like heatwaves. Subsequently, the study explored long-term fire weather variability and changes. Finally, the investigation evaluated the influence of ENSO and other climate drivers over fire weather. The analyses used three groups of data: bushfire records, meteorological and climate indices data. Consistent bushfire records were available only for Victoria during the period 1961-2010. Additionally, the investigation required observations from weather stations in Victoria and the Ecuadorian Andes. This research also analysed reanalysis data from the Twentieth Century Reanalysis Project (20CR) and the European Reanalysis of Global Climate Observations ERA-Clim project (ERA-20C). The study had a stronger emphasis on ENSO since it affects both regions. This research used two indices to represent fire weather. The first index was the McArthur Forest Fire Danger Index (FFDI). This Australian metric was designed for an Eucalyptus environment. Therefore, this investigation applied the FFDI for Victoria and Ecuador. Additionally, this thesis proposes an alternative fire weather index for Victoria: the “Victorian Seasonal Bushfire Index” (VSBI). The VSBI combines local meteorological variables and sea surface temperature in ENSO regions to represent—and predict—extreme fire weather. The investigation of fire weather in Victoria and the Ecuadorian Andes yielded several findings. First of all, bushfire and heatwave weather patterns display differences from one another in Victoria. These comparisons used synoptic climatologies with reanalysis data during the period 1961-2010. Additionally, the investigation showed that Victoria experienced an increase in fire danger during the period 1974-2010. There is also weaker evidence suggesting an increasing trend since 1920. “El Niño” events are the leading remote driver of fire activity in Victoria. In fact, the incorporation of ENSO indicators in a simple index (VSBI) shows skill to forecast extreme fire weather in this region. For the Ecuadorian Andes, this research indicates that its fire danger season (July-September) is longer than reported. October and November also display “high” fire danger during the period 1997-2012. Finally, “El Niño” events increase fire risk in the Ecuadorian Andes.
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ItemMeasurement and modelling of heat flow in the Gippsland Basin, Victoria( 2015)Geothermal energy has the potential to provide significant quantities of highly available power with little environmental impact. Enhanced geothermal system (EGS) technologies have the potential to become major contributors to global energy production, with a much wider geographic scope than the more established conventional geothermal systems. Certain favourable geological conditions have been recognised as providing improved prospectivity for EGS resources, primarily elevated heat flow rates and thermally insulating cover sequences. Most attention has been given to the location of regions having anomalously high heat flow, typically due to increased heat production in basement rocks such as granites rich in radiogenic isotopes. Little attention has been paid to extremes in thermal insulation, which offer an alternative but equally effective mechanism for increasing geothermal gradients and thus reducing the depth to a geothermal resource. Large and thick deposits of highly insulating coal present a unique thermal environment, where the commonly assumed one-dimensional relationship between surface heat flow and temperature at depth described by Fourier's Law is not maintained due to heat refraction -- a three-dimensional process. Understanding the effects of heat refraction due to thermal insulation and its effect on surface heat flow is a crucial element of exploration strategies in coal-bearing sedimentary basins. The onshore Gippsland Basin, and in particular the Latrobe Valley, is an ideal setting to study the effects of buried confined insulators on surface heat flow and thermal structure. This thesis combines the results of observational insights from empirical field data collection with mathematically driven insights of theoretical models, and simulation-driven insights of numerical finite-element modelling. Additionally, it explores the relatively modern paradigm of data-driven statistical science to generate predictions of rock properties from related intrinsic variables. Measured surface heat flow is moderately variable, with the ten most reliable calculations from borehole data having an interquartile range of 61--78 mW/m², with a mean and standard deviation of 72±14 mW/m², slightly higher than previous estimates. Groundwater advection identified in previous studies appears to affect the thermal structure of only the Cainozoic stratigraphy. Losses of up to 37 mW/m² in the vertical heat flow in the sandy Balook Formation of borehole Rosedale-301 represents a local maximum of heat transfer associated with groundwater advection. Only minor thermal effects are observed in the uppermost Mesozoic section, indicating a return to a dominantly conductive thermal regime there. The self-organising map technique was applied to the prediction of lithostratigraphy and thermal conductivity from well-log data. It successfully identified 91.3% of lithostratigraphy samples from a supervised mapping of well-log data. Mapping of thermal conductivity with corresponding well-log data produced more variable results compared with a petrophysical log interpretation technique over a large cohort of boreholes. However, the SOM analysis returned predicted values with a better correlation with measured values at sampled depths, required less pre-processing of log data, and was able to perform with non-standard log data and legacy tools. With further refinements of the technique, potential improvements may be made with its prediction performance of thermal conductivity and other rock properties. Heat flow theory applied to an idealised simulation of the Latrobe Valley coal seams showed that temperature increases of 35°C beneath the coal are possible over a reference model having no such insulation. Finite-element forward models of cross-sections and 3D volumes through the onshore Gippsland Basin identified highly variable surface heat flow, having up to ±30 mW/m² variance from the basal flux input. Complex patterns resulting from heat refraction were produced, with two common features indicative of confined insulators: 1. the greatest increase in subsurface temperature is correlated with the greatest decrease in surface heat flow, however, 2. surface heat flow tends to be slightly increased above the margins of buried insulators. The main implication from these results is the identification of an end-member insulation-dominated geothermal resource style, requiring new strategies for exploration and resource targeting.
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ItemAltitudinal distribution of vegetation in the headwaters of the Wongungarra River, Victoria( 1993)Changes in vegetation composition with respect to altitude were investigated in the sclerophyllous forests of the Australian mountain region. Vegetation was surveyed at 148 sites along two transects which were located to maximise variation in altitude and minimise the influence of environmental factors not directly related to altitude. The measurement, simulation, and estimation of environmental variables revealed that this aim was met except at the end-points of the transects where secondary influences are present.
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ItemLeachate chemistry of two modern municipal waste landfills in Melbourne, Victoria( 1999-11)This study investigates the occurrence and chemical composition of leachate at Clayton South and Brooklyn Municipal waste landfills in Melbourne, Victoria. Both are ‘modern’ municipal waste landfills, being engineered and managed consistent with current regulatory requirements. These landfills accept only putrescible and solid inert waste, but not soluble chemical, hazardous, liquid or prescribed industrial waste. (For complete abstract open document) Analyses of an extensive range of chemical parameters reveals a complex mixture of inorganic and organic compounds, similar to those of international authors researching leachate chemistry. Dominant ions in these leachates are NH4+, Na+, HC03- and Cl-. Except for Fe, heavy metals are not present in significant concentrations (mostly
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ItemThe hydrogeology of the Gippsland Basin, and its role in the genesis and accumulation of petroleum( 2002)The Gippsland Basin of southeastern Australia is the most energy-rich basin of Australia producing petroleum, gas and brown coal. Three-quarters of the Basin lies offshore and the rest onshore. The basin was initiated as a rift valley, caused by the separation of the Australian continent from the Antarctic followed by a number of tectonic events throughout the basin history. Early Cretaceous sedimentary rocks form the basement, which is in turn covered with Late Cretaceous to Recent sediment of sand, clay, limestone, and brown coal seams. The total thickness of the in-filling sediments offshore attains up to 6000 m, but onshore is up to 1200 m. There are three main acquifer systems, the Hydrostratigraphic Units 2, 4, and 7, all of which are confined. The two lower aquifer systems, Units 4 and 7, contain high temperature groundwater. It is generally agreed that the hydrocarbons offshore have been derived from terrestrial matters including brown coal and ligneous clay offshore. In the present study, the author has developed a case that hydrocarbons offshore being derived not only from the offshore source but also from onshore brown coals and coaly matter and in this hydrocarbon forming processes, groundwater has played a significant role. The Central Deep, in particular, provides favourable conditions for hydrocarbon maturation. Throughout the basin history, the Central Deep has experienced the oil window temperatures. In supporting this hypothesis, geochemical studies on groundwater, brown coal, and hydrocarbons as well as hydrodynamics are presented.
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ItemThe Permian glacial sediments of central Victoria and the Murray Basin: their sedimentology and geochemistry( 1986)This study investigates the sedimentology and geochemistry of Permian glacial sediments cropping out in the Bacchus Marsh and Derrinal areas in central Victoria and in the subsurface beneath the Cainozoic Murray Basin in Victoria, New South Wales and South Australia. Facies analysis of the Bacchus Marsh Formation, based on a critical review of literature on glacial sedimentary processes and environments, identifies the following major facies groups: 1. Subglacial tillites deposited beneath wet-based ice. Some of these tillites exhibit structures indicative of a number of subglacial processes such as frictional lodgement of large clasts, subglacial bed deformation, subglacial meltwater flow and subglacial size sorting of clasts. Other subglacial tillites are essentially structureless. 2. Bedded diamictites to sandstones deposited predominantly by ice-rafting of debris into standing water. 3. Fluvial outwash sandstone and conglomerate facies that are finer-grained than typical proglacial outwash facies. 4. Deltas and subaqueous outwash fans vary from sandy sediments deposited by proglacial and subglacial streams to coarse, poorly sorted complexes deposited as debris aprons close to the ice front. Abundant underflow deposits suggest that less than normal marine salinities prevailed in these water bodies, even if they were arms of the sea. 5. Supraglacial tillites consisting of sandy diamictites to pebble conglomerates. Facies in the thickest sequence in the Bacchus Marsh area suggests that the area was covered by a major ice mass at least 8 times. Minor glacial advances took place during predominantly ice-free periods. The Derrinal Formation consists of a basal unit of predominantly subglacial tillite deposited in shallow glacially excavated valleys overlain by a complex of subglacial and supraglacial facies deposited by about 8 minor advances of a small ice tongue. Facies relationships in this part of the sequence are confused by intense deformation of the sediment pile during the melting of buried ice and dewatering of saturated diamictons. A major ice advance then overwhelmed the area depositing thick subglacial tillite. The Urana Formation, beneath the Murray Basin, is dominated by marine ice-rafted diamictite and mudstone. Rhythmically bedded siltstone and claystone, sediment gravity-flow deposits, traction-current deposits, and, possibly, subglacial tillites are also present. Facies assemblages in some drill holes indicate areas that were never covered by grounded glacial ice. Sedimentological and palaeontological evidence suggests that the Urana Formation was deposited towards the end of the glaciation. Ice motion indicators and ice sheet limits inferred from the facies assemblages in the Urana Formation are used to estimate the thickness of the ice over central Victoria during glacial maxima. These estimates support the conclusion drawn from the facies analysis that the ice was a large ice sheet. Comparisons of ice movement directions for central Victoria and formerly adjacent parts of Gondwana suggest that a large ice sheet was centred in North Victorialand. Major and some trace elements analyses of the clay component of marine and non-marine diamictites were used to test a number of methods of distinguishing marine from nonmarine glacial diamictites. None of the methods were clearly successful because sediment detrital mineralogy dominates the geochemical composition though V/Cr ratios may be useful in some circumstances.
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ItemOccurrence of nitrate in soil and groundwater in the Corangamite area, Western Victoria( 1996)Soil and groundwater samples taken from two areas of different land use in the Corangamite Region, 200 km west of Melbourne, were analysed for nitrate and ammonium, and in some cases chloride. Both sites are located on the Later Newer Volcanics 'stone rises', and groundwater was sampled from nested bores which intersect the shallow unconfined aquifer and deeper semi-confined aquifer at both sites. The Carpendeit site is an area of native Eucalypt forest, and the Purrumbete North site is a pasture for grazing dairy cows. Low concentrations of nitrate (< 1 mgN/L) in groundwater at Carpendeit correspond to low soil nitrate concentrations (< 3 µgN/cm3 ). Higher groundwater nitrate concentrations occurred in the shallow unconfined aquifer at Purrumbete North, (up to 3 mgN/L), but not in the lower semi-confined aquifer, and corresponds to higher nitrate concentrations in soil (1 to 60 µgN/cm3 ). Elevated nitrate concentrations also occurred in groundwater discharge at McVeans Springs, in the range 2.61 to 4.72 mgN/L, and at Ettrick Springs in the range 8.08 to 16.07 mgN/L, greater than the limit of 10 mgN/L for drinking water specified in ANZECC water quality guidelines. Nitrate in soil under the pasture is probably derived primarily from the activity of nitrogen fixing bacteria associated with subterranean clover introduced to the pasture. Soil nitrate distributions suggest intense return of nitrogen in dung and urea occurs at 'camps' locations on the pasture, where cows tend to gather for shelter. Transport of nitrogen to shallow groundwater is stimulated by cracks and channels in the basalt clay soils. Local groundwater flow includes interaction with the many lakes and temporary ponds 'which form in surface depressions at times of high rainfall. The ponds probably serve as an effective nitrate supply in recharge to the shallow aquifer.
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ItemTransport, attenuation, and degradation of organic chemicals in a basaltic aquifer system near Melbourne, Australia( 1996)Groundwater in the Pliocene to Pleistocene fractured and jointed Newer Volcanics basaltic aquifer system beneath Melbourne's industrialised western suburbs is extensively contaminated by a wide variety of organic and inorganic compounds. Groundwater in Tertiary sediments underlying the Newer Volcanics is probably also contaminated by the same sources. The main objectives of this research were 1) to assess the types, concentrations, and distribution of contaminants in the Newer Volcanics aquifer system in Melbourne's western suburbs and at a selected contaminated site and 2) to determine contaminant transport, attenuation, and degradation processes affecting organic contaminants in this aquifer system. Contaminants detected in the Newer Volcanics aquifer system during this research include phenols, volatile organic compounds, polynuclear aromatic hydrocarbons, polychlorinated biphenyls, metals, and inorganic anions. The groundwater flow system in the study area comprises a single heterogeneous and anisotropic unconfined aquifer, and includes both the Newer Volcanics and underlying sedimentary units (the Brighton Group and the Werribee Formation), although hydraulic connection of these units to the volcanics is irregular. Groundwater flow in the Newer Volcanics is through vesicular and/or scoriaceous lava flow tops and bottoms, in intercalated fluvial deposits, and through the fractured and jointed lava flows. Locally (scale of less than I km square), the basaltic aquifer system may consist of hydraulically separated shallow and deep aquifer zones that are connected on a larger scale. The deep aquifer zones may be semi-confined to confined. Groundwater in the study area is recharged via throughflow from upgradient and infiltration of rainfall. Discharge from the Newer Volcanics in the study area is primarily to underlying sedimentary formations, but also to surface water features and directly to Port Phillip Bay. Several mechanisms which reduce contaminant concentrations are possible in the Newer Volcanics aquifer system. These include volatilisation, dispersion and diffusion, transient storage, matrix diffusion, sorption, hydrolysis, and biodegradation. However, the nature of porosity in the Newer Volcanics may significantly extend the lifetime of contaminant plumes via the processes of transient storage and matrix diffusion. The primary mechanisms of attenuation and degradation of organic contaminants in the Newer Volcanics aquifer system are probably biodegradation, matrix diffusion, sorption, and dispersion (for non-reactive contaminants) in order of decreasing effect. Biodegradation at the water table and discharge areas will also be significant because of atmospheric contact and increased dissolved oxygen concentrations. Because of the relative lack of organic carbon in the basaltic aquifer system, sorption will occur mainly to mineral surfaces in clay-rich zones and within the rock matrix (concurrent with matrix diffusion). In some cases, relatively undiluted contaminants may be transported along preferred flow paths to discharge locations where they may pose a potential threat to the environment prior to degradation or attenuation. It was found, at least with phenols and volatile organic compounds in groundwater at a study site, that contaminants are degraded and/or attenuated rapidly, probably via biodegradation, matrix diffusion, and sorption. Biodegradation testing of groundwater at this study site confirmed the existence of microorganisms in the aquifer system capable of aerobic degradation; indirect evidence may indicate the presence of anaerobes.
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ItemStructural analysis of selected duplex soils( 1971)The profile characteristics, geographical extent and general environmental relationships of duplex soils are described. They are shown to be an important group in Australia and particularly in Victoria. The variety of approaches and definitions employed by investigators of soil structure are discussed. These are contrasted with the definition used in this thesis which incorporates the concepts of spatial distribution and orientation of vectorial fabric elements in the soil. The importance of describing structural features at a number of scales is emphasized. At each scale an attempt is made to quantitatively describe (where possible) the three or two-dimensional geometrical properties of the soil components. A structural classification of duplex soils that incorporates a number of descriptive geometrical elements is proposed. A detailed study is made of the structure and related chemical, physical and mineralogical properties at an undisturbed site (Boorook) in Western Victoria. The ground surface at the Boorook site is described as being deformed into gilgai microrelief. It is demonstrated that soil structural analysis can be usefully employed to develop a swelling mechanism that explains how the Boorook gilgai probably formed. The data and subsequent analysis tends to place some doubt on mechanisms proposed by past workers. A detailed study is also reported from a site (Hartwell) near Melbourne. The site is described as being illustrative of profiles that show little or no internal and ground surface deformation. An unfolded stoneline is considered to be the principal structural feature. The mechanism for the formation of the stoneline is shown to probably involve gravitational settling of the grains in a fluid-like medium. Regional investigations of profiles throughout Western and Central Victoria and New Guinea are also described. It has been found that the principles and techniques of soil structural analysis can also be applied to buried soil structures. By these means it has been possible to establish that buried fold-like structures seen in section in a road cutting at Terang, are in fact relics of gilgai. Experimental models have assisted the investigations into the structure of duplex soils and have provided additional information on the dynamic interaction of moisture with the soil components. The main processes and sequences in the genetic development of structure of duplex soils as discussed in the light of observations of natural structures and experimental results. Attention is drawn to the differences between the dominant structural processes in the two main horizons of the profile. The approach of soil structural analysis is formalized for profile studies into the discipline of Structural Pedology. The principles of Structural Pedology threaded through the body of the thesis are summarized and shown to be very similar to those of Rock Fabric Analysis. The need for an interdisciplinary approach in this field is emphasized. It is shown that soil structural analysis is not limited to Pedology but rather can be applied to a number of academic and applied problems in a variety of disciplines that include Engineering (Soil Mechanics), Earth Sciences, Agriculture, Soil Erosion and Conservation.
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ItemStructural geology of the area between Bacchus Marsh and Blackwood( 1968)Scope of study: This thesis is concerned primarily with the structural geology of the Ordovician basement rocks along the Lerderderg River Gorge and its two main tributaries. Deformation of the Ordovician rocks constituted the fundamental interest that led to the detailed study of structural elements at various scales. Fabric diagrams were widely used in structural of macroscopic structures. Micro-fabric analysis was not applicable because of low grade regional metamorphism and the fine texture of the rocks. A computer programme used in the preparation of the various fabric diagrams greatly increased the efficiency and accuracy of the study of the structural geometry and symmetry of the deformed Ordovician rocks. A brief description is given of the Permian glacial deposits, the Cainozoic alluvial deposits, the Older and Newer Basalts, the quartz veins, and the different types of dykes.