This is a compilation of all the bathymetry data that GA holds in its database for the area that covers the Diamantina Fracture Zone to the Naturaliste Plateau. This dataset consist of different 6X4 degrees tiles that are: Tiles SI48,SJ48,SK48,SL48, SI47,SJ47, SK47,SL47, SJ46,SK46,SL46, SK45 and SL45)

Legacy product - no abstract available

Compressional deformation is a common phase in the post-rift evolution of passive margins and rift systems. The central west Western Australian margin, between Geraldton and Karratha, provides an excellent example of strain partitioning between inverting passive margin crust and adjacent oceanic and continental crust. The distribution of contemporary seismicity in the region indicates a concentration of strain release within the basins diminishing eastward into the cratons. Very few data exist to quantify uplift or slip rates, however this pattern can be qualitatively demonstrated by tectonic landforms which indicate that the last century or so of seismicity is representative of patterns of Neogene and younger deformation. Pleistocene marine terraces on the western side of Cape Range indicate uplift rates of several tens of metres per million years, with similar deformation resulting in sub-aerial emergence of Miocene strata on Barrow Island and elsewhere. In the southern Carnarvon Basin, marine strandlines of unknown age are displaced by a few tens of metres, indicating uplift rates an order of magnitude lower than further west. Relief production rates in the western Yilgarn Craton are lower still - numerous scarps (e.g. Mt Narryer) appear to relate individually to <10 m of displacement across Neogene strata. The en echelon arrangement of such features distinguish them from those representing strain concentration in the craton proper, where scarps are isolated and typically <5 m high. Quantitative analysis of time-averaged deformation preserved in the aforementioned landforms, including study of scarp length as a proxy for earthquake magnitude, has the potential to provide useful constraint on seismic hazard assessments in a region which contains major population centres and nationally significant infrastructure.

Benthic habitats on the continental shelf are strongly influenced by exposure to the effects of surface ocean waves, and tidal, wind and density driven ocean currents. These processes combine to induce a combined flow bed shear stress upon the seabed which can mobilise sediments or directly influence organisms disturbing the benthic environment. Output from a suite of numerical models predicting these oceanic processes have been utilised to compute the combined flow bed shear stresses over the entire Australian continental shelf for an 8-year period (March 1997- February 2005 inclusive). To quantify the relative influence of extreme or catastrophic combined flow bed shear stress events and more frequent events of smaller magnitude, three methods of classifying the oceanographic levels of exposure are presented: 1. A spectral regionalisation method, 2. A method based on the shape of the probability distribution function, and 3. A method which assesses the balance between the amount of work a stress does on the seabed, and the frequency with which it occurs. Significant relationships occur between the three regionalisation maps indicating seabed exposure to oceanographic processes and physical sediment properties (mean grain size and bulk carbonate content), and water depth, particularly when distinction is made between regions dominated by high-frequency (diurnal or semi-diurnal) events and low-frequency (synoptic or annual) events. It is concluded that both magnitude and frequency of combined-flow bed shear stresses must be considered when characterising the benthic environment. The regionalisation outputs of the Australian continental shelf presented in this study are expected to be of benefit to quantifying exposure of seabed habitats on the continental shelf to oceanographic processes in future habitat classification schemes for marine planning and policy procedures.

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.

Legacy product - no abstract available

Many aspects of the evolution and overall architecture of the Australian southern rifted margin are consistent with current models for the development of non-volcanic rifted margins. However, when examined in detail, several key features of the southern margin provide useful points of comparison with the Atlantic and Alpine Tethyan margins from which these models derive. Extensive petroleum industry and government seismic and geophysical data sets have enabled detailed mapping of the basins of the southern margin and an improved understanding of its tectonostratigraphic evolution. Australia's southern rifted continental margin extends for over 4000 km, from the structurally complex margin south of the Naturaliste Plateau in the west, to the transform plate boundary adjacent to the South Tasman Rise in the east. The margin contains a series of Middle Jurassic to Cenozoic basins-the Bight, Otway, Sorell, Gippsland and Bass basins, and smaller depocentres on the South Tasman Rise (STR). These basins, and the architecture of the margin, evolved through repeated episodes of extension and thermal subsidence leading up to, and following, the commencement of sea-floor spreading between Australia and Antarctica. Break-up took place diachronously along the margin, commencing in the west at ~83 Ma and concluding in the east at ~ 34 Ma. In general, break-up was not accompanied by significant magmatism and the margin is classified as 'non-volcanic' (or magma-poor). Initial NW-SE ultra-slow to slow seafloor spreading (latest Santonian-Early Eocene), followed by N-S directed fast spreading (Middle Eocene-present), resulted in: (1) an E-W oriented obliquely- to normally-rifted marginal segment extending from the westernmost Bight Basin to the central Otway Basin; (2) an approximately N-S oriented transform continental margin in the east (western Tasmania-STR), and (3) a transitional zone between those end-members (southern Otway-Sorell basins).

The interpretation of two regional seismic reflection profiles and the construction of a balanced cross section through the southern Australian margin (Bight Basin) are designed to analyze the influence of the Australia-Antarctica continental breakup process on the kinematic evolution of the Cretaceous Ceduna delta system. The data shows that the structural architecture of this delta system consists of two stacked sub-delta systems. The lower White Pointer delta system (Late Albian-Santonian) is an unstable tectonic wedge, regionally detached seaward above Late Albian ductile shales. Sequential restorations suggest that the overall gravitational sliding behavior of the White Pointer delta wedge (~45 km of seaward extension, i.e., ~25%) is partially balanced by the tectonic denudation of the subcontinental mantle. We are able to estimate the horizontal stretching rate of the mantle exhumation between ~2 km Ma-1and 5 km Ma-1. The associated uplift of the distal part of the margin and associated flexural subsidence in the proximal part of the basin are partially responsible for the decrease of the gravitational sliding of the White Pointer delta system. Lithospheric failure occurs at ~84 Ma through the rapid exhumation of the mantle. The upper Hammerhead delta system (Late Santonian-Maastrichtian) forms a stable tectonic wedge developed during initial, slow seafloor spreading and sag basin evolution of the Australian side margin. Lateral variation of basin slope (related to the geometry of the underlying White Pointer delta wedge) is associated with distal raft tectonic structures sustained by high sedimentation rates. Finally, we propose a conceptual low-angle detachment fault model for the evolution of the Australian-Antarctica conjugate margins, in which the Antarctica margin corresponds to the upper plate and the Australian margin to the lower plate.

Under the Australian Government's Energy Security Program, Geoscience Australia conducted a seismic survey and a marine reconnaissance survey to acquire new geophysical data and obtain geological samples in frontier basins along the southwest Australian continental margin. Specific areas of interest include the Mentelle Basin, northern Perth Basin, Wallaby Plateau and southern Carnarvon Basin. The regional seismic survey acquired 7300 km of industry-standard 2D reflection seismic data using an 8 km solid streamer and 12 second record length, together with gravity and magnetic data. These new geophysical datasets, together with over 7000 km of re-processed open-file seismic data, will facilitate more detailed mapping of the regional geology, determination of total sediment thickness, interpretation of the nature and thickness of crust beneath the major depocentres, modelling of the tectonic evolution, and an assessment of the petroleum prospectivity of frontier basins along the southwest margin. The scientific aim of the marine reconnaissance survey was to collect swath bathymetry, potential field data, geological samples and biophysical data. Together with the new seismic data, samples recovered from frontier basins will assist in understanding the geological setting and petroleum prospectivity of these underexplored areas.

This paper gives an interpretation of the continental margin off Willkes Land and Terre Adelie, East Antarctica, concentrating on the transition from continental to oceanic crust. The interpretation is based on the deep-seismic and potential field data acquired under the Australian Antarctic and Southern Ocean Profiling Project in 2001 and 2002.