This study investigated the surrogacy relationships between marine physical variables and the distribution of marine infauna species and measures of benthic biodiversity across the continental shelf offshore from Ningaloo Reef, Western Australia. The three study areas are located at Mandu Creek, Point Cloates and Gnaraloo covering a combined area of 1038 km2. The physical variables include morphometric variables derived from multibeam bathymetry data, texture measures derived from acoustic backscatter data, sediment variables from 265 samples, seabed exposure estimates and geomorphic feature types. Together, these data were used to model total abundance and species richness, and 10 individual infauna species using a Random Forest Decision Tree. The key findings are: - Generally, the surrogacy relationships are stronger at Gnaraloo than at Mandu and Point Cloates. This is likely due to the fact that Gnaraloo is dominated by soft sediment and Point Cloates and Mandu have larger areas of hard substrates which preclude infauna. - At Gnaraloo, the most important physical surrogates were the sediment variables. - At Point Cloates, the most important physical surrogates were the bathymetry-derived parameters including seabed heterogeneity, morphological position, and slope. - At Mandu, the most important physical surrogates were the mixture of the bathymetry- derived parameters including morphological position and geomorphic features, and the sediment variables including gravel content, and backscatter derived texture measures. - Seabed exposure was not a useful physical surrogate for the infauna distribution in this study. The likely reasons are not clear, but could be a function of the grid resolution (150 m) of the hydrodynamic model used to generate the exposure variable relative to infaunal patterns; or that the infauna species are protected by the sediment from seabed disturbance.

This Geocat record is a CD of presentations delivered as part of the 4th Technical Advisory Group workshop for the Palaeovalley Groundwater Project. The workshop was held in Canberra at Geoscience Australia on 5 and 6 April 2011 and involved ~20 people including GA staff and invited guests from state government water resource and geological survey organisations in SA, NT and WA. The CD has been compiled as a record of the workshop and will be delivered to the workshop participants as a record of the event.

This map shows the estimated extent of surface water in the Tully region shortly after the passing of Tropical Cyclone Yasi (TC Yasi). It has an AVNIR2 imagery background. It's Scale is 1:58,000. The map is a compilation of GA topographic data, surface water extent derived from satellites and imagery.

Image showing gravity sation coverage and relative reliability over Australia, updated to May 2011

Models of seabed sediment mobilisation by waves and currents over Australia's continental shelf environment are used to examine whether disturbance regimes exist in the context of the intermediate disturbance hypothesis (IDH). Our study shows that it is feasible to model the frequency and magnitude of seabed disturbance in relation to the dominant energy source (wave-dominated shelf, tide-dominated shelf or tropical cyclone dominated shelf). Areas are mapped where the recurrence interval of disturbance events is comparable to the rate of ecological succession, which meets criteria defined for a disturbance regime. We focus our attention on high-energy, patch-clearing events defined as exceeding the Shields (bed shear stress) parameter value of 0.25. Using known rates of ecological succession for different substrate types (gravel, sand, mud), predictions are made of the spatial distribution of a dimensionless ecological disturbance index (ED), given as: ED = FA (ES/RI), where ES is the ecological succession rate for different substrates, RI is the recurrence interval of disturbance events and FA is the fraction of the frame of reference (surface area) disturbed. Maps for the Australian continental shelf show small patches of ED-seafloor distributed around the continent, on both the inner and outer shelf. The patterns are different for wave-dominated (patches on the outer shelf trending parallel to the coast), tide-dominated (patches crossing the middle-shelf trending normal to the coast) and cyclone-dominated (large oval-shaped patches crossing all depths). Only a small portion of the shelf (perhaps ~10%) is characterised by a disturbance regime as defined here. To our knowledge, this is the first time such an analysis has been attempted for any continental shelf on the earth.

We present a probabilistic tectonic hazard analysis of a site in the Otway Basin,Victoria, Australia, as part of the CO2CRC Otway Project for CO2 storage risk. The study involves estimating the likelihood of future strong earthquake shaking and associated fault displacements from natural tectonic processes that could adversely impact the storage process at the site. Three datasets are used to quantify the tectonic hazards at the site: (1) active faults; (2) historical seismicity, and; (3) GPS surface velocities. Our analysis of GPS data reveals strain rates at the limit of detectability and not significantly different from zero. Consequently, we do not develop a GPS-based source model for this Otway Basin model. We construct logic trees to capture epistemic uncertainty in both the fault and seismicity source parameters, and in the ground motion prediction. A new feature for seismic hazard modelling in Australia, and rarely dealt with in low-seismicity regions elsewhere, is the treatment of fault episodicity (long-term activity versus inactivity) in the Otway model. Seismic hazard curves for the combined (fault and distributed seismicity) source model show that hazard is generally low, with peak ground acceleration estimates of less than 0.1g at annual probabilities of 10-3-10-4/yr. The annual probability for tectonic displacements of greater than or equal to 1m at the site is even lower, in the vicinity of 10-8-10-9/yr. The low hazard is consistent with the intraplate tectonic setting of the region, and unlikely to pose a significant hazard for CO2 containment and infrastructure.

Detrital zircon from sandstone bodies intersected in three recent exploration wells on the North West Shelf were analysed and dated using the SHRIMP (Sensitive High Resolution Ion Microprobe) at Geoscience Australia to test the technique as a tool for understanding the provenance and sediment transport pathways of reservoir facies in the region. Chevron, Hess and Santos, the operating companies for exploration permits WA- 365-P, WA-390-P and WA-281-P respectively, collected 3-5 kg of cuttings from the wells Guardian-1 and Hijinx-1 (Triassic Mungaroo Formation on the Exmouth Plateau of the Carnarvon Basin) and Burnside-1 (Jurassic Brewster Sands from the Browse Basin). All three wells were drilled in 2009-2010. Samples were prepared at Geoscience Australia with 70-80 zircon grains randomly selected for analysis following standard data acquisition and processing procedures to provide a statistically meaningful representation of detrital ages in each sample.

One of the primary requirements of managing our water resources sustainably is an understanding of the water balance. Key components of a water balance model are inputs of recharge and outputs or discharge. Rates of recharge and discharge change in response to climate, landscape morphology, geology, soil/regolith, native vegetation and landuse (including landuse history). The variable nature of these parameters results in a high degree of local variability when determining recharge and discharge fluxes both spatially and temporally. Water managers deal with this complexity in a variety of ways. Where detailed information on key parameters influencing recharge and discharge are available, comprehensive, fully distributed groundwater models are used. However, in most cases this information is not available (e.g. data poor areas) and typically a crude estimation of recharge (2-10% of average annual rainfall) is given. In these cases, discharge is often assumed to be zero. A collaborative project, funded by NWC and involving CSIRO Land and Water and Geoscience Australia, has developed a new national framework for estimating recharge and discharge in data poor areas. The approach consists of excel-based models that allow the user to populate key input fields (e.g. rainfall, soil and regolith texture, bedrock type, vegetation) to generate estimates of recharge and discharge. These excel models have been coupled with a complementary national-scale GIS dataset to assist the user in populating model input fields. In combination, the models and the GIS datasets allow the user to rapidly estimate recharge and/or discharge anywhere in Australia. The national-scale GIS datasets are available through a WEB-based interface. This presentation will focus on the development of the input datasets and will provide a brief demonstration of the WEB-based interface.

Dense coral-sponge communities on the upper continental slope (570 - 950 m) off George V Land, east Antarctica have been identified as Vulnerable Marine Ecosystems. We propose three main factors governing their distribution on this margin: 1) their depth in relation to iceberg scouring; 2) the flow of organic-rich bottom waters; and 3) their location at the head of shelf cutting canyons. Icebergs scour to 500 m in this region and the lack of such disturbance is a likely factor allowing the growth of rich benthic ecosystems. In addition, the richest communities are found in the heads of canyons which receive descending plumes of Antarctic Bottom Water formed on the George V shelf, which could entrain abundant food for the benthos. The canyons harbouring rich benthos are also those that cut the shelf break. Such canyons are known sites of high productivity in other areas due to strong current flow and increased mixing with shelf waters, and the abrupt, complex topography.

Report on operational activities with data, analysis and interpretation for the Gawler - Eucla demonstration study site in South Australia