This preliminary report will provide a geochemical and ionic characterisation of groundwater, to determine baseline conditions and, if possible, to distinguish between different aquifers in the Laura basin. The groundwater quality data will be compared against the water quality guidelines for aquatic ecosystem protection, drinking water use, primary industries, use by industry, recreation and aesthetics, and cultural and spiritual values to assess the environmental values of groundwater and the treatment that may be required prior to reuse or discharge.

The global ocean absorbs 30% of anthropogenic CO2 emissions each year, which changes the seawater chemistry. The absorbed CO2 lowers the pH of seawater and thus causes ocean acidification. The pH of the global ocean has decreased by approximately 0.1 pH units since the Industrial Revolution, decreasing the concentration of carbonate ions. This has been shown to reduce the rate of biological carbonate production and to increase the solubility of carbonate minerals. As more CO2 is emitted and absorbed by the oceans, it is expected that there will be continuing reduction in carbonate production coupled with dissolution of carbonate sediments. This study was undertaken as part of a program to collect baseline data from Australia's seabed environments and to assess the likely impacts of ocean acidification on continental shelf sediments. Over 250 samples from four continental shelf areas of northern Australia (Capricorn Reef, Great Barrier Reef Lagoon, Torres Strait, Joseph Bonaparte Gulf) were analysed to characterise the surface sediment mineral and geochemical composition. Of particular importance was the quantification of carbonate minerals (calcite, aragonite, high-magnesium calcite) and the magnesium content in high-magnesium calcite. The latter determines the solubility of high-magnesium calcite, which is most soluble of all common carbonate minerals. The thermodynamic stability of carbonate minerals as referred to the state of saturation was calculated using the current and predicted equatorial ocean water composition [1]. Northern Australian continental shelf sediments are largely dominated by carbonate. High-magnesium calcite had the highest abundance of all carbonate minerals followed by aragonite in all areas. The average mol% MgCO3 in high-magnesium calcite varied from 13.6 to 15.5 mol% for the different areas, which is in agreement with the global average magnesium concentration in high-magnesium calcite in tropical and subtropical regions [2].

This report gives an overview of the activities of the Geoscience Australia IVS Analysis Center during 2012

Volcanic ash represents a serious hazard to communities living in the vicinity of active volcanoes in developing countries like Indonesia. Geoscience Australia, the Australia-Indonesia Facility for Disaster Reduction (AIFDR) and the Indonesian Centre for Volcanology and Geohazard Mitigation (CVGHM) have adapted an existing open source volcanic ash dispersion model for use in Indonesia. The core model is the widely used volcanic ash dispersion model FALL3D. A python wrapper has been developed, which simplifies the use of FALL3D for those with little or no background in computational modelling. An application example is described here for Gunung Ciremai in West Java, Indonesia. Scenarios were run using eruptive parameters within the acceptable range of possible future events for this volcano, granulometry as determined through field studies and a meteorological dataset that represented a complete range of possible wind conditions expected during the dry and rainy seasons for the region. Implications for varying degrees of hazard associated with volcanic ash ground loading on nearby communities for dry versus rainy season wind conditions is discussed. Communities located on the western side of Gunung Ciremai are highly susceptible to volcanic ash ground loading regardless of the season whereas communities on the eastern side are found to be more susceptible during the rainy season months than during the dry. This is attributed to prevailing wind conditions during the rainy season that include a strong easterly component. These hazard maps can be used for hazard and impact analysis and can help focus mitigation efforts on communities most at risk.

Preliminary zircon data and tectonic framework for the Thomson Orogen, northwestern NSW

2013 Acreage Release Areas W13-19 and W13-20 in the offshore northern Perth Basin, Western Australia, cover more than 19,000 km2 in parts of the Houtman, Abrolhos, Zeewyck and Gascoyne sub-basins. The Release Areas are located adjacent to WA-481-P, the only offshore exploration permit active in the Perth Basin, granted to joint venture partners Murphy Australia Oil Pty Ltd, Kufpec Australia Pty Ltd and Samsung Oil and Gas Australia Pty Ltd in September 2012. Geoscience Australia recently undertook a regional prospectivity study in the area as part of the Australian Government's Offshore Energy Security Program. A revised sequence stratigraphic framework, based on new biostratigraphic sampling and interpretation, and an updated tectonostratigraphic model, using multiple 1D burial history models for Permian to Cenozoic sequences, give fresh insights into basin evolution and prospectivity. Geochemical studies of key offshore wells demonstrated that the late Permian's Lower Triassic Hovea Member oil-prone source interval is regionally extensive offshore in the Abrolhos and potentially Houtman sub-basins. This is supported by fluid inclusion data that provides evidence for palaeo-oil columns within Permian reservoirs in wells from the Abrolhos Sub-basin. Additionally, oil trapped in fluid inclusions in Houtman-1 can be linked to Jurassic source rocks suggesting that multiple petroleum systems are effective in the Release Areas. A trap integrity analysis was undertaken to mitigate exploration risks associated with trap breach during Early Cretaceous breakup and provides a predictive approach to prospect assessment. Potential seepage sites on the seafloor over recently reactivated faults correlate with hydroacoustic flares, pockmarks and dark colored viscous fluid observed over the areas. These observations may indicate an active modern-day petroleum system in the Houtman Sub-basin. The presence of a Jurassic petroleum system combined with the extension of the Hovea Member source rock offshore, the potential presence of seeps and results from trap integrity studies provide a platform to revitalize exploration in the offshore northern Perth Basin. The APPEA Journal

A prospectivity assessment of the offshore northern Perth Basin was undertaken as part of the Australian Government's Offshore Energy Security Program. The study integrates a newly-developed tectonostratigraphic framework, regional trap integrity analysis and data from a hydrocarbon seepage survey to provide new insights into the petroleum prospectivity of the basin and reduce exploration risk. The study developed a new sequence stratigraphic framework based on results from new biostratigraphic sampling and interpretation. The existing tectonostratigraphic model was revised using multiple 1D burial history models for the Permian to Cenozoic sequences. New findings on prospectivity of the Perth Basin come from geochemical studies of key offshore wells. The studies demonstrated that the late Permian-Early Triassic Hovea Member (Kockatea Shale) oil-prone source interval is regionally extensive offshore in the outer Houtman and Abrolhos sub-basins. This is supported by fluid inclusion data that provide evidence for palaeo-oil columns within Permian reservoirs in wells from the Abrolhos Sub-basin. Oil shows in the offshore part of the basin can be linked to potential Early Permian and Jurassic potential source rocks. A number of potential plays were identified by the study. To mitigate exploration risks associated with trap breach during Early Cretaceous breakup, a trap integrity analysis was undertaken. Geomechanical analyses showed that NNW-SSE oriented faults have a high risk of reactivation and high permeability zones at fault intersections are prone to leakage. Optimally-oriented large faults preferentially accommodate strain and shield nearby structures from reactivation. Hydroacoustic flares, pockmarks and a dark coloured viscous fluid observed over potential seepage sites on the seafloor may indicate an active modern-day petroleum system in the Houtman Sub-basin.

Abstract for AMSA Conference

The Virtual Geophysics Laboratory (VGL) is an environment that was developed as a data discovery and delivery facility with software and computing facilities. This design enables geoscientists to store, discover, retrieve and process datasets. Recent developments are expanding the VGL to incorporate the functionality of the Underworld software. Underworld is open source, parallel software capable of calculating the 3D temperature distribution in the crust. Numerical modelling of temperature is a tool that can be used to predict the temperature distribution at depth between and beneath measurement points based on a 3D geological map. Computing models on a regional scale tends to be computationally intensive, and high-performance computing (HPC) facilities are often required to run computations at full resolution. In order to assess uncertainty quantitatively, HPC facilities are almost always a requirement. The new developments to VGL will facilitate the discovery and access to 3D geological maps. It will also provide easier access to the Underworld software, and will provide the high performance and cloud computing facilities (hosted at the National Computing Infrastructure and elsewhere) required to run large models. The metadata associated with each run performed using VGL is automatically stored, and therefore runs completed on VGL will be repeatable and testable.

Surprisingly few natural hydrocarbon seeps have been identified in Australia's offshore basins despite studies spanning thirty years. Initial studies of natural hydrocarbon seepage around the Australian margin were generally based around the geochemical analysis of stranded bitumens, water column geochemical `sniffer' sampling, synthetic aperture radar or airborne laser fluorsensor. Later studies involved the integration of these remote sensing and geochemical techniques with mutli-channel and shallow seismic. A review of these earlier studies indicates that many seepage interpretations need to be re-evaluated and that previous data sets, when set in a global context, often represent normal background hydrocarbon levels. Relatively few sites of proven natural hydrocarbon seepage in Australia's offshore sedimentary basins can be reconciled with the dominantly passive margin setting and low recent sedimentation rates, which are not favourable for high rates of seepage, and difficulties in proving seepage on high energy, shallow carbonate shelves, where seabed features may be rapidly reworked and modern marine signatures are overprinted on authigenic seep carbonates. Active thermogenic methane seepage on the Yampi Shelf, the only proven documented occurrence in Australia, is driven by deposition of a thick Late Tertiary carbonate succession and Late Miocene tectonic reactivation. Therefore, to increase the success of detecting and correctly interpreting natural hydrocarbon seepage, data need to be analysed and integrated within the context of the local geological setting, and with an understanding of what is observed globally.