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  • A new continental-scale geochemical atlas and dataset for Australia were officially released into the public domain at the end of June 2011. The National Geochemical Survey of Australia (NGSA) project, which started in 2007 under the Australian Government's Onshore Energy Security Program at Geoscience Australia, aimed at filling a huge knowledge gap relating to the geochemical composition of surface and near-surface materials in Australia. Better understanding the concentration levels and spatial distributions of chemical elements in the regolith has profound implications for energy and mineral exploration, as well as for natural resource management. In this world first project, a uniform regolith medium was sampled at an ultra-low density over nearly the entire continent, and subsamples from two depths and two grain-size fractions were analysed using up to three different (total, strong and weak) chemical digestions. This procedure yielded an internally consistent and comprehensive geochemical dataset for 68 chemical elements (plus additional bulk properties). From its inception, the emphasis of the project has been on quality control and documentation of procedures and results, and this has resulted in eight reports (including an atlas containing over 500 geochemical maps) and a large geochemical dataset representing the significant deliverables of this ambitious and innovative project. The NGSA project was carried out in collaboration with the geoscience agencies from every State and the Northern Territory under National Geoscience Agreements. .../...

  • The 1:250 000 maps show the type and distribution of 51 regolith-landform units with unique dominant regolith-landform associations, and are a subset of the 205 mapping units on the six 1:100 000 maps. These units are distinct patterns of recurring landform elements with characteristic regolith associations. Geomorphic symbols indicate the location and type of geomorphic activity. The maps present a systematic analysis and interpretation of 1:89 000 scale 1973 RC9 aerial photography, 1:100 000 scale topographic maps (AUSLIG), and field mapping data. High resolution (250m line spacing) airborne gamma-ray spectrometry and magnetics (Geoterrex) were used where applicable

  • This map is designed to show broad regolith-landform units, giving a regional overview of the main regolith types and their associated landforms.Included are the author's detailed Explanatory Notes to the map.

  • Improving techniques for mapping land surface composition at regional- to continental-scale is the next step in delivering the benefits of remote sensing technology to Australia. New methodologies and collaborative efforts have been made as part of a multi-agency project to facilitate uptake of these techniques. Calibration of ASTER data with HyMAP has been very promising, and following an program in Queensland, a mosaic has been made for the Gawler-Curnamona region in South Australia. These programs, undertaken by Geoscience Australia, CSIRO, and state and industry partners, aims to refine and standardise processing and to make them easily integrated with other datasets in a GIS.

  • Geoscience Australia (GA) was engaged by Sydney Water Corporation (SW) to review existing geological, geophysical and geotechnical data from the Sydney region in an effort to better understand seismic hazard in SW's area of operations. The main motivation is that this information can be used to improve SW's understanding of the level of earthquake risk to their infrastructure in order to support their asset management practices. Of particular interest is improving SW's understanding of asset damage or loss and potential network disruption following a large earthquake. One of the main factors influencing earthquake hazard in the Sydney Water area of operations is the likelihood of a large earthquake to the west of Sydney on what is known as the Lapstone Structural Complex. Research conducted by Geoscience Australia suggests that large earthquakes in the Lapstone Structural Complex are extremely rare (i.e. they may only happen once every few million years). This means that the area probably does not contribute as much to the seismic hazard in Sydney as has been previously thought. An equally important factor is the response of near-surface geological materials to earthquake shaking. Two seismic site classification maps for the Sydney region have been developed here to characterise materials in terms of their potential response. One uses the modified United States National Earthquake Hazard Reduction Program (NEHRP) classification scheme, while the other uses the Australian Earthquake Loading Standard (AS1170.4-2007) classification scheme. Assessment and validation of the classifications against independently acquired data from sub-surface investigations in the region suggest that both classifications provide a satisfactory representation of the distribution of materials and their potential to amplify earthquake energy. The exception to this outcome is the area underlain by the Botany Basin, where geophysical investigations and drilling data have identified the thicker basin fill sediments as having the potential to effectively increase earthquake hazard. The aforementioned AS1170.4 site classification was used to generate Australian Standard (AS1170.4-2007) earthquake hazard maps covering SW's area of operations. The analyses were completed for three spectral periods (0 s, 0.2 s and 1.0 s) and two return periods (500 years and 800 years). Results show that earthquake shaking at 0.2 s spectral period produced the highest hazard at both return periods. Overall, areas characterised by the presence of unconsolidated Cenozoic sedimentary units exhibited the highest earthquake hazard under all conditions. The modified NEHRP site classification outputs were used to produce a probabilistic seismic hazard assessment for the SW area of operations, using the same spectral periods and return periods. Comparison of the AS1170.4-2007 and EQRM outputs reveal several key findings. Firstly, the use of the modified NEHRP site classification scheme better differentiates the properties of geological materials, and therefore the seismic hazard, across the SW area of operations. Secondly, the probabilistic seismic hazard assessment produced values that were up to 6 times lower than those generated using the Australian Standard methodology. Lastly, regardless of the site classification schema or hazard methodology employed, areas characterised by relatively unconsolidated Cenozoic (predominantly Quaternary) sedimentary deposits always represented the highest levels of earthquake hazard.

  • In late 2006, the Australian Government announced its Energy Security Initiative, allowing Geoscience Australia to initiate a major program of onshore and offshore activities. The ambitious National Geochemical Survey of Australia (NGSA) project was launched in January 2007 as part of this program because until then Australia lacked a complete geochemical data coverage. Such a dataset informs on the concentrations and distributions of chemical elements in the near-surface environment. This pre-competitive knowledge, used in combination with other datasets, can contribute to making exploration for energy and mineral resources more cost-effective and less risky by helping target more detailed activities. As a spin-off, the multi-element dataset can also have applications in the fields of natural resources management, land-use decision-making and geohealth, for instance. During precursor pilot projects carried out between 2003 and 2006 in the Riverina, Gawler and Thomson regions, various sampling media, grain-size fractions and analytical methods were tested. In particular, it emerged that catchment outlet sediments from either overbank or floodplain settings or from similar low-lying settings were an ideal sampling medium that could be found across Australia. These sediments are, by their very nature, well-mixed composites of contributions from the dominant rock and soil types found within a catchment. Further, being deposited during times of receding floods, they are typically fine-grained, a beneficial property that enhances the geochemical signal-to-noise ratio. The data from the pilot projects indicated that even surface catchment outlet sediments could reflect geochemical signatures from basement and mineralisation, even when covered by thick transported overburden. .../...

  • Outlet sediment (or overbank) samples from 99 catchments in the Thomson region have been examined by conventional geochemical analytical methods and by partial extraction using Mobile Metal Ion (MMI) leach. Elements such as Pb have good correlation with known mineral deposits using conventional (near-total digestion) methods, whilst elements such as Cu, Au and Ag show a better correlation with known mineral deposits when MMI concentrations are used. This study shows that very low density sampling of catchment outlet sediments (1 site/1540 km2) provides useful and possibly predictive geochemical information for mineral exploration in areas dominated by transported regolith.

  • Analytical data for 10 major oxides (Al2O3, CaO, Fe2O3, K2O, MgO, MnO, Na2O, P2O5, SiO2 and TiO2), 16 total trace elements (As, Ba, Ce, Co, Cr, Ga, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn and Zr), 14 aqua regia extractable elements (Ag, As, Bi, Cd, Ce, Co, Cs, Cu, Fe, La, Li, Mn, Mo and Pb), Loss On Ignition (LOI) and pH from >3500 soil samples from two continents (Australia and Europe) are presented and compared to (1) the composition of the upper crust, (2) published world soil average values, and (3) data from other continental-scale soil surveys. It is demonstrated that average upper continental crust values do not provide reliable estimates for natural concentrations of elements in soils. For many elements there exist substantial differences between published world soil averages and the median concentrations observed on two continents. Direct comparison with other continental datasets is hampered by the fact that often mean, instead of the statistically more correct median, is reported. Using a database of the worldwide distribution of lithological units, it can be demonstrated that lithology is a poor predictor of soil chemistry. Climate-related processes such as glaciation and weathering are strong modifiers of the geochemical signature inherited from bedrock during pedogenesis. To overcome existing shortcomings of predicted global or world soil geochemical reference values, we propose Preliminary Empirical Global Soil reference values based on analytical results of a representative number of soil samples from two continents (PEGS2).

  • Inland sulfidic soils have recently formed throughout wetlands of the Murray River floodplain associated with increased salinity and river regulation (Lamontagne et al., 2006). Sulfides have the potential to cause widespread environmental degradation both within sulfidic soils and down stream depending on the amount of carbonate available to neutralise acidity (Dent, 1986). Sulfate reduction is facilitated by organic carbon decomposition, however, little is known about the sources of sedimentary organic carbon and carbonate or the process of sulfide accumulation within inland sulfidic wetlands. This investigation uses stable isotopes from organic carbon (13C and 15N), inorganic sulfur (34S) and carbonate (13C and 18O) to elucidate the sources and cycling of sulfur and carbon within sulfidic soils of the Loveday Disposal Basin.