Geoscience Australia carried out a marine survey on Carnarvon shelf (WA) in 2008 (SOL4769) to map seabed bathymetry and characterise benthic environments through colocated sampling of surface sediments and infauna, observation of benthic habitats using underwater towed video and stills photography, and measurement of ocean tides and wavegenerated currents. Data and samples were acquired using the Australian Institute of Marine Science (AIMS) Research Vessel Solander. Bathymetric mapping, sampling and video transects were completed in three survey areas that extended seaward from Ningaloo Reef to the shelf edge, including: Mandu Creek (80 sq km); Point Cloates (281 sq km), and; Gnaraloo (321 sq km). Additional bathymetric mapping (but no sampling or video) was completed between Mandu creek and Point Cloates, covering 277 sq km and north of Mandu Creek, covering 79 sq km. Two oceanographic moorings were deployed in the Point Cloates survey area. The survey also mapped and sampled an area to the northeast of the Muiron Islands covering 52 sq km. cloates_3m is an ArcINFO grid of Point Cloates of Carnarvon Shelf survey area produced from the processed EM3002 bathymetry data using the CARIS HIPS and SIPS software

This atlas of reflection profiles penetrating the whole crust, with accompanying geological maps, represents a collaboration between the Research School of Earth Sciences at The Australian National University and Geoscience Australia. The reflection atlas project arose from work on the Australian Seismological Reference Model (AuSREM) sponsored by the National Infrastructure program of AuScope and the Australian National University.

Australia's floodplain environments are typically low-relief landscapes that can exhibit a high degree of (subtle) landscape complexity, high variability in permeability characteristics, and hence highly variable recharge potential. In the Broken Hill Managed Aquifer Recharge project, geomorphic maps of a large area (7,500 km2) of the Darling River floodplain near Menindee N.S.W. were produced in two stages. Initially, broad-scale mapping to identify high order landscape features was carried out using Google Earth. These maps were used for project planning and initial assessments of drilling locations. A second phase of higher resolution mapping utilised a LiDAR DEM, which was levelled using trend surfaces to eliminate regional slope (~20m). An ArcGIS interactive contour tool was then used to identify specific breaks in elevation associated with landform features. Multivariate image analysis of elevation, high resolution SPOT and Landsat-derived wetness further enhanced the contrast between geomorphic elements to confirm mapping boundaries. While specific landforms can be characterised by particular surface materials, these sediments can vary within a single geomorphic feature. Consequently, SPOT multispectral satellite imagery was used to identify surface materials using principal component analysis and unsupervised classification. This approach generated 20 classes; each assigned a preliminary cover/landform attribute using SPOT imagery. Field data (surface and borehole sample, and observations at shallow pits) were used to refine the classification approach. Interactive mapping using a de-trended DEM provided a rapid, effective and accurate alternative to time consuming manual landform digitisation. Integration of geomorphic and surface-materials maps helped identify potential natural infiltration sites and assess options for managed aquifer recharge (MAR) including potential dune and basin infiltration.. The high-resolution geomorphic and surface-materials maps, validated by shallow augering, pits and drilling, were also essential for the interpretation of near-surface layers in a regional airborne electromagnetics (AEM) survey. The geomorphic maps also provided a key input layer to the assessment of groundwater dependent vegetation and overall MAR assessments.

Inundation mapping is critical to improving our understanding of groundwater recharge processes in Australian floodplains. In this project, spatial extent, depth and frequency of flood waters were also critical inputs to MAR assessment and infrastructure design. Flood extent mapping can be undertaken in many ways including simple fill models reliant on elevation data or more complex numerical 1D or 2D models, both of which can be used to report on historical events and predict future scenarios. Remote sensing approaches are also used, although these are only capable of reporting on prior events. Simple fill models use a single known or estimated water level to produce a corresponding flood inundation extent, while numerical models account for and model the complex movement of water across the landscape in generating water levels and flood extents. However, numerical models are data intensive and somewhat subjective, being affected by input data, type of model and description of the river geometry in the model. In this study, insufficient information was available to develop a numerical model. Instead, a high-resolution LiDAR dataset was acquired over a 7,500 km2 area of the Darling River floodplain and combined with historic and real time river level gauge data to produce a simple fill model. A 20 m difference in floodplain elevation over the length of the river necessitated levelling of the LiDAR DEM to the Darling River floodplain. This was done by subtracting the interpolated floodplain elevation trend surface from the DEM, producing a de-trended floodplain surface. The levelled DEM surface was then adjusted to the water level as measured at the principal (Weir 32) river gauge station at the time of image acquisition. Flood extents were derived by elevation slicing of the new DEM surface to specified river levels; flood depth is an inverted version of the flood-extent grid. The approach proved successful in the central portion of the study area proximal to the river gauge station but overestimated and underestimated further south and north respectively. Calibration in these areas is hampered by a lack of survey and river gauge points, with possible approaches include generating trend surfaces for topographically discrete sections of the landscape and applying a simple fill to generate a continuous surface flow network.

Part- page item on matters related to the Australian Stratigraphy Commission and the Australian Stratigraphic Units Database. This column discusses the usefulness and vulnerability of type sections and reference sections.

A multi-disciplinary systems mapping approach, utilising airborne electromagnetics (AEM), and validated by a 7.5 km drilling program (100 sonic and rotary mud holes), and complementary hydrogeological and hydrogeochemical investigations, has identified potential groundwater resources stored within Pliocene aquifers (Calivil Formation (CFm) and Loxton Parilla Sands (LPS)) to depths of ~100m beneath the Darling River floodplain. The Pliocene aquifers are sandwiched between thick clay aquitards, and vary from confined to 'leaky confined' systems. The CFm, which extends over the north and central parts of the study area, varies significantly in thickness (0-70 m). This variability results from (1) in-filling of broad (structurally-controlled) palaeovalleys in an undulating palaeo-landscape, with relief of up to 40m from valley bottoms to hill tops; and (2) post-depositional tectonic effects that include structural inversion on faults, as well as warping and tilting. The lower bounding surface of the CFm is marked by an erosional contact (10 m year hiatus) with Renmark Group sediments. Facies analysis indicates that the CFm was deposited in deep braided streams across a dissected sedimentary landscape. Overall, the sequence is fining-upwards, with evidence for transgression over the LPS. Channel fill materials comprise gravels and sands, and local fine-grained units represent abandoned channels and local floodplain sediments. The upper surface of the CFm is irregular, with up to 16 m of relief evident, due to a combination of tectonics and depositional filling of channel and bar topography in the upper CFm. Integration of textural and hydraulic testing data has revealed there are five hydraulic classes within the CFm, ranging from clays to gravels. At a regional scale (kms), sands and gravels are widely distributed with particularly good aquifers developed in palaeochannels and at the confluence of palaeo-river systems. In these strategic locations, the CFm has high storage capacity, very high transmissivities (up to 50 l/s), and significant volumes of fresh groundwater. At a local scale, there is considerable lithological heterogeneity (10s to 100s of metres) within the palaeochannels. The use of AEM was critical to the targeting of premium aquifer sites and detailed hydrogeological investigations.

A major concern for regulators and the public with geological storage of CO2 is the potential for the migration of CO2 via a leaky fault or well into potable groundwater supplies. Given sufficient CO2, an immediate effect on groundwater would be a decrease in pH which could lead to accelerated weathering, an increase in alkalinity, release of major and minor ions and heavy metals (particularly Pd, Ni and Cr) as well as CO2 mobilisation of trace organic contaminants. These scenarios potentially occur in a high CO2 leakage event, therefore detection of a small leak, although barely perceptible, could provide an important early warning for a subsequent and more substantial impact. Different approaches are required for the detection and quantification of these low level leaks and are the subject of this paper. A 3 year groundwater survey was recently completed in the Surat Basin, which provided comprehensive water and isotopic analysis of groundwaters together with their exsolved gases. The gases were analysed for composition, -13CCO2, -13CCH4 and -2HCH4. Methane is prevalent in the major Surat Basin aquifers (e.g. Mooga, Gubberamunda and Hutton sandstones) and is invariably associated with a bacterial (methanogenic) carbonate reduction source, evident from its isotopic signature ('13CCH4 ~ -70', '2HCH4 ~ -220'). In addition to methane and low levels of CO2, trace ethane is common. Two neighbouring wells, however, were quite different to the other 85 wells surveyed. Their exsolved gases contained comparatively high ethane, but also C1-C6 hydrocarbons in addition to methane. Methane isotope systematics were significantly different from other groundwater wells completed in the same formation. The -13C of the CO2 was similar to the surrounding groundwater wells, but the relative proportion of CO2 in the gas was significantly higher. Combined, these characteristics are consistent with hydrocarbon biodegradation. There was little difference in the groundwater chemistry for these wells compared to the regional baseline. The study provides a useful analogue study for detection, at various scales, of a leaky well associated with a geological storage site. Compositional and isotopic analysis of exsolved gases from groundwater samples could be used to demonstrate non-equilibrium conditions and intrusion of exogenic CO2. Abstract for the 2013 International Association of Hydrologist Congress, Perth

Wildfires are one of the major natural hazards facing the Australian continent. Chen (2004) rated wildfires as the third largest cause of building damage in Australia during the 20th Century. Most of this damage was due to a few extreme wildfire events. For a vast country like Australia with its sparse network of weather observation sites and short temporal length of records, it is important to employ a range of modelling techniques that involve both observed and modelled data in order to produce fire hazard and risk information/products with utility. This presentation details the use of statistical and deterministic modelling of both observations and synthetic climate model output (downscaled gridded reanalysis information) in the development of extreme fire weather potential maps. Fire danger indices such as the McArthur Fire Forest Danger Index (FFDI) are widely used by fire management agencies to assess fire weather conditions and issue public warnings. FFDI is regularly calculated at weather stations using measurements of weather variables and fuel information. It is important to calculate the spatial distribution of the return period of extreme values of indices such as FFDI, as it has been shown that relatively few extreme events cause most of the impacts. The long-term spatial tendency FFDI (indicator of fire weather conditions) has been assessed by calculating the return period of its extreme values from observational data. The frequency and intensity as well as the spatial distribution of FFDI extremes were obtained by applying an advanced spatial interpolation algorithm to the recording stations' measurements. As an illustration maps of 50 and 100-year return-period (RP) of FFDI under current climate conditions are presented. Future work will focus on the impact of climate change on FFDI.

Area features of the oil and gas fields.

The concentration of sulfur in fluids associated orogenic gold deposits is important for understanding the transport of gold species but still remains poorly defined. In this study Raman spectroscopy has been used to obtain the concentrations and fugacities of H2S in individual fluid inclusions from the Archean, sub-amphibolite facies Missouri gold deposit in Western Australia. Type III, vapor-rich (XH2O < 0.4) fluid inclusions from the Missouri gold deposit were shown to contain highly variable CO2/CH4 ratios (0.01 to 1.9) and H2S fugacities of up to 1.6 MPa. The calculated values of H2S are consistent with the location of fluids within the general pyrite stability field next to the pyrite-pyrrhotite reaction boundary. This is in accord with the quartz(-plagioclase)-biotite-carbonate-pyrite alteration assemblage that occurs adjacent to the quartz veins at the Missouri deposit. Geochemical modelling was used to investigate how the concentration of H2S was affected by the fCO2/fCH4 ratio of a fluid in equilibrium with the pyrite-pyrrhotite alteration assemblage. Overall, the highest H2S concentrations are predicted for 'reduced-fluids' near the CH4 apex of the H2O-CH4-CO2 ternary diagram. Comparisons with the measured H2S concentrations show that the CH4-CO2¬-Pyrite-Troilite equilibrium could be the controlling factor on the H2S concentration of the fluid; other processes could have affected some inclusions which contain higher than predicted H2S concentrations. These are mostly restricted to the population of water-poor (XH2O < 0.1), essentially CH4-CO2 inclusions.