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.

National Geochemical Survey of Australia field training for the geoscience agencies of all States and the Northern Territory took place during 2007 and early 2008. The knowledge transfer mechanisms comprise a detailed National Geochemical Survey of Australia: Field Manual (GA Record 2007/08), this training presentation and several days of in-field sample collection under the guidance of NGSA staff.

Poster for the Australian Earth Sciences Convention 2010.

The National Geochemical Survey of Australia (NGSA) was initiated in late 2006, and details of progress were published, among others, in Caritat et al. (2009). The ultra-low density geochemical survey was facilitated by, and based on, overbank sediment sampling at strategic locations in 1186 catchments. Included in the analysis methods was a partial extraction method by the Mobile Metal Ion (MMI) technique (Mann, 2010) of sediment sampled at the depth of 0-10 cm, air-dried and sieved to <2 mm. The MMI method is based on solubilisation of adsorbed ions and potentially can provide a measure of bio-availability, as ions in natural soil pore waters are subject to solubility by solutions stronger in complexing ability than pure water, but not subject to soil phase dissolution as achieved by strong acid or total digestion methods. Of the ten elements considered essential for plant growth (Ca, Cu, Fe, K, Mg, Mn, N, P, S and Zn), only two (N and S) were not included in the 53 elements analysed after MMI extraction of the overbank samples. Comparison of a number of MMI concentrations for each element with the corresponding total analysis for the same soil samples provides an estimate of the recovery % by MMI in a similar manner to that used by Albanese (2008) to evaluate ammonium acetate-EDTA as a measure of bio-availability. Individual maps for the eight nutrients based on MMI analysis provide some very interesting and potentially useful information. For example, highest 'bio-available' Fe concentrations are not related to the Fe-rich soils and rocks of the Pilbara, but to high rainfall areas close to the coast, where processes akin to lateritisation are still taking place. The movement of Fe as Fe2+ and its subsequent oxidation to Fe3+ is not only important to agriculture, but on the east coast of Australia it has a number of environmental consequences in river systems. The distribution pattern for Mn .../...

Legacy product - no abstract available

Legacy product - no abstract available

In late 2006, the Australian Government announced its Energy Security Initiative, allowing Geoscience Australia to initiate, among others, a major program of onshore activities [1]. An 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. Building on methods developed during precursor pilot projects [2], NGSA targets catchment outlet (overbank) sediments as a uniform sampling medium. A shallow and a deeper level are being collected in 1390 catchments covering 91% of the country. Sampling is carried out by State and Northern Territory geoscience agencies following protocols described in a detailed Field Manual [3] and practiced during in-field training; all equipment and consumables are provided centrally. Dry and moist Munsell colours, soil pH, digital photographs and GPS coordinates are recorded in the field. In the laboratory, these transported, fine-grained regolith materials are dried and a split is archived for future use. Electrical conductivity and pH of 1:5 (soil:water) slurries, laser particle size distribution and infrared spectroscopy are measured on the remaining split. This split is further sieved into two grain-size fractions (<2 mm and <75 mm) for analysis by x-ray fluorescence (XRF), inductively-coupled mass spectrometry (ICP-MS) after total digestion (multi-element) as well as after aqua regia digestion (multi-element, including low level gold), and by specialised methods for platinum group elements, fluorine and selenium. As at February 2009, 78% of the samples have been collected and most analyses have been completed for the first 25% of samples. The project will contribute fundamental knowledge to the energy and mineral resources exploration industry by its completion in June 2011. This pre-competitve knowledge, used in combination with other datasets, can reduce exploration cost/risk by helping target more detailed activities. Spin-offs into other applications are also expected.

The National Geochemical Survey of Australia (NGSA) aims to collect samples from 1529 sites located in 1390 catchments (10% of which are sampled in duplicate) covering over 90% of Australia. At each site, two depth ranges are sampled, giving 3058 samples to be processed. Each sample results in 13 individually packaged sub-samples, meaning that 39,754 separate containers will be prepared, labelled, delivered to the laboratories or archived during the sample preparation phase of the project. Any excess fraction in the processing streams is kept for potential future use. The detailed procedures for preparing the NGSA samples in the laboratory are described with an overview of Quality Assessment/Quality Control and Operational Health and Safety measures also provided. There are three main parts to the sample preparation protocol. The first part is the Bulk Sample stream. The sample is received from the field, weighed, dried (for a minimum of 48h at 40°C) and sieved through a 4.75 mm mesh to remove any foreign material. The sample is then homogenised and split into two halves. One half is sealed and set aside for archiving for future analyses/investigations. The other half is split into sub-samples or aliquots for: 1. laser particle size analysis (LPSA), pH 1:5 (soil:water) and electrical conductivity (EC) 1:5 (soil:water) analysis; and 2. X-ray diffraction (XRD) analysis. The remainder of the bulk material is sieved through a 2mm mesh, and split into two portions (~20% and ~80%), which are processed in the following two streams. The second part is the Coarse Fraction stream. In this stream, the ~20% split of <2 mm sample prepared above is further split to prepare two aliquots for: - platinum group element (PGEs) analysis; and - gold (Au) analysis after aqua regia (AR) leach. The third part is the Fine Fraction stream. In this stream, the ~80% split of <2 mm sample prepared above is sifted using small stainless steel riffle splitters. The sample <75 um fraction is split into 5 different aliquots (splits) for different analyses. These aliquots are ranked in order of decreasing priority.

Spectral data from airborne and ground surveys enable mapping of the mineralogy and chemistry of soils in a semi-arid terrain of Northwest Queensland. The study site is a region of low relief, 20 km southeast of Duchess near Mount Isa. The airborne hyperspectral survey identified more than twenty surface components including vegetation, ferric oxide, ferrous iron, MgOH, and white mica. Field samples were analysed by spectrometer and X-ray diffraction to test surface units defined from the airborne data. The derived surface materials map is relevant to soil mapping and mineral exploration, and also provides insights into regolith development, sediment sources, and transport pathways, all key elements of landscape evolution.

Introduction to a supplementry issue on Cenozoic Continental Sediments in Australia.