The Capel and Faust basins are located in a frontier part of offshore eastern Australia, about 800 km east of Brisbane in 1300-2500 m of water. Little is known of the basin structures and geological history of this area, which is a continental fragment separated from Australia during the Cretaceous rifting of the Tasman Sea. In 2007 Geoscience Australia acquired 6000km of 2D seismic reflection and refraction data, gravity and magnetics, to begin an assessment of the petroleum prospectivity of these basins. A workflow has been developed to assist the seismic interpreter with feedback from a coherent 3D geology model that is used to predict the gravity response of the basins. This response is harmonized with the observed gravity and modified geological horizons are then returned to the seismic interpreter. An interface between Geoframe and Geomodeller has been optimized to make it very easy to do many iterations of this process, as suits the changing needs of the interpretation team.

3D visualisation of the Mount Isa Crustal Seismic Survey

There is growing awareness of the scientific and intrinsic value of Antarctic geological features, including sites containing rare, and in some cases, globally unique mineral occurrences, mineral assemblages, and unusual rocks features (e.g. ventifacts) and rare fossils. However, the global economic value of the mineral and fossil trade is also considerable and growing, with prized specimens being sold for prices per gram equivalent to that of gold. Locations of geological value, once considered 'protected' by virtue of the logistical complexity and prohibitive cost involved in collection, are becoming increasingly vulnerable as the interest of collectors grows and the inaccessibility of Antarctica diminishes with more frequent visits by private and adventure travellers. Thus the need for proactive intervention, protection and management of 'geo-heritage' sites is becoming increasingly urgent. Wider recognition of the geological values of sites achieved by invoking the provisions for area management of the Madrid Protocol will also help mitigate casual souveniring and accidental or deliberate damage caused by ill-advised construction or other human activity, such as use of heavy machinery.

Abstract for SGA Townsville 2009

Receiver function studies of Northern Sumatra T. Volti and A. Gorbatov Geoscience Australia, GPO Box 378 Canberra ACT 2601 Australia The Northern Sumatra subduction zone is distinguished by the occurrence of the 2004 Sumatra-Andaman megathrust earthquake and has a peculiar subduction of two major bathymetric structures; the Investigator fracture zone and the Wharton fossil ridge. Four stations in Northern Sumatra (BSI, PSI, PPI, GSI) and two stations in Malaysia (KUM and KOM) have been selected to construct migrated images based on receiver functions (RF) in order to study Earth structure and subduction processes in the region. Waveforms from 304 teleseismic earthquakes with Mb >5.5 and a distance range of 30º to 95º recorded from April 2006 to December 2008 were used for the analysis. The number of RF for each station varies from 20 to 192 depending on the signal/noise ratio. The computed RF clearly show pS conversions at major seismic velocity discontinuities associated with the subduction process where the Moho is visible at 5.5, 4, 3.5, and 2 sec for BSI, PSI, PPI, and GSI, respectively. RF for KUM and KOM have only conversions at the Moho near ~4 sec. The subducted slab is visible below Sumatra as a positive amplitude conversion preceded by a negative one, which we interpret as a low-velocity structure above the subducted slab. RF for PSI located at Toba supervolcano reveal pockets of low-velocity zones extending from a ~50 km depth down to the subducted slab. Forward modellings of RF suggest that seismic velocity contrasts can reach ~18% that is in accordance with previous local tomographic studies.

Geoscience Australia has developed an interactive 3D viewer for three national datasets; the new Radiometric Map of Australia (Geoscience Australia 2009b), the Magnetic Anomaly Map of Australia (Geoscience Australia 2004), and the Gravity Anomaly Map of the Australian Region (Geoscience Australia 2008). The interactive virtual globe is based on NASA's open source World Wind Java Software Development Kit (SDK) and provides users with easy and rich access to these three national datasets. Users can view eight different representations of the radiometric map and compare these with the magnetic and gravity anomaly maps and satellite imagery; all draped over a digital elevation model. The full dataset for the three map sets is approximately 55GB (in ER Mapper format), while the compressed full resolution images used in the virtual globe total only 1.6GB and only the data for the geographic region being viewed is downloaded to users computers. This paper addresses the processes for selecting the World Wind application over other solutions, how the data was prepared for online delivery, the development of the 3D Viewer using the Java SDK, issues involving connecting to.

The first RSTT model for Australia has been developed based on the Australian Seismological Reference Model (AuSREM) that was released in late 2012. The densely-gridded P and S wave distributions of the crust and upper mantle of AuSREM have been simplified and translated into the 7 layer crustal and upper mantle RSTT model. Travel times computed with this RSTT model are evaluated against travel times computed in full 3D through the AuSREM model to assess the impact of the approximations used by RSTT. Location estimates of 5 ground truth earthquakes (GT1, GT2 and GT5) using the global ak135 reference model, the RSTT model and the full 3D travel times are compared. It is found that the RSTT model can reproduce the 3D travel times fairly accurately within its distance of applicability, thereby improving location estimates compared to using a global travel time model like ak135. However the benefit of using RSTT for locating Australian earthquakes is far less than using full 3D travel times, mainly because most stations tend to be further away from the source than the distance of RSTT applicability.

The Australian Government formally releases new offshore exploration areas at the annual APPEA conference. In 2012, twenty-eight areas in nine offshore basins are being released for work program bidding. Closing dates for bid submissions are either six or twelve months after the release date, i.e. 8 November 2012 and 9 May 2013, depending on the exploration status in these areas and on data availability.

Like many of the basins along Australia's eastern seaboard, there is currently only a limited understanding of the geothermal energy potential of the New South Wales extent of the Clarence-Moreton Basin. To date, no study has examined the existing geological information available to produce an estimate of subsurface temperatures throughout the region. Forward modelling of basin structure using its expected thermal properties is the process generally used in geothermal studies to estimate temperatures at depth in the Earth's crust. The process has seen increasing use in complex three-dimensional (3D) models, including in areas of sparse data. The overall uncertainties of 3D models, including the influence of the broad assumptions required to undertake them, are generally only poorly examined by their authors and sometimes completely ignored. New methods are presented in this study which will allow estimates and uncertainties to be addressed in a quantitative and justifiable way. Specifically, this study applies Monte Carlo Analysis to constrain uncertainties through random sampling of statistically congruent populations. Particular focus has been placed on the uncertainty in assigning thermal conductivity values to complex and spatially extensive geological formations using only limited data. As a case study these new methods are then applied to the New South Wales extent of the Clarence-Moreton Basin. The geological structure of the basin has been modelled using data from existing petroleum drill holes, surface mapping and information derived from previous studies. A range of possible lithological compositions was determined for each of the major geological layers through application of compositional data analysis. In turn, a range of possible thermal conductivity values was determined for the major lithology groups using rock samples held by the NSW Department of Primary Industries (DPI). These two populations of values were then randomly sampled to establish 120 different forward models, the results of which have been interpreted to present the best estimate of expected subsurface temperatures, and their uncertainties. These results suggest that the Clarence-Moreton Basin has a moderate geothermal energy potential within an economic drilling depth. This potential however, displays significant variability between different modelling runs, which is likely due to the limited data available for the region. While further work could improve these methods, it can be seen from this study that uncertainties can provide a means by which to add confidence to results, rather than undermine it.

The lower Darling Valley contains Cenozoic shallow marine, fluvial, lacustrine and aeolian sediments including a number of previously poorly dated Quaternary fluvial units associated with the Darling River and its anabranches. New geomorphic mapping of the Darling floodplain that utilises a high resolution LiDAR dataset and SPOT imagery, has revealed that the Late Quaternary sequence consists of scroll-plain tracts of different ages incised into a higher more featureless mud-dominated floodplain. Samples for OSL (Optically-Stimulated Luminescence) and radiocarbon dating were taken in tractor-excavated pits, from sonic drill cores and from hand-auger holes from a number of scroll-plain and older floodplain sediments in the Menindee region. The youngest, now inactive, scroll-plain phase, associated with the modern Darling River, was active in the period 5-2 ka. A previous anabranch scroll-plain phase has dates around 20ka. Indistinct scroll-plain tracts older than the anabranch system, are evident both upstream and downstream of Menindee and have ages around 30ka. These three scroll-plain tracts intersect just south of Menindee but are mostly separated upstream and downstream of that point. Older dates of 50 ka, 85 ka and >150 ka have been obtained from lateral-migration sediments present beneath the higher mud-dominated floodplain. Establishing a chronology for the Quaternary fluvial landscape has been important for groundwater investigations in the Darling River floodplain area. More specifically, this has assisted in constraining the 3D mapping of floodplain units, helped constrain conceptual models of surface-groundwater interaction, and aided in the assessment of managed aquifer recharge options.