The southern Australian margin is unique as it is the only known passive margin that formed over and orthogonal to a Mesozoic subducted slab in the mantle. The tectonic subsidence pattern observed along the southern Australian margin primarily reflects the extensional processes that were associated with the development of the divergent continental margins of Australia and Antarctica, coupled with Cretaceous mantle dynamics and the influence of intra-plate stress on the Australian plate in the Late Tertiary.

This cross agency report, highlights the areas of the central NSW continental slope prone to sediment mass wasting over time. It includes the critical factors which contribute to slope failure including basement geometry, angle of slope and thickness of overlying sediments. Evidence of slope failure are observed through: surficial tension cracks; creep features; faulting; redistribution of sediments, multiple relict slides on the sea floor and erosional surface scars.

Flexural backstripping applied to 5 seismic reflection lines has been used to constrain the distribution of lithosphere thinning, crustal structure and the location of the ocean-continent transition (OCT) of the southern Australian Bight Basin rifted margin. The amplitude of the anomalous subsidence in the southern margin of Australia was determined for each seismic line by means of residual depth anomalies (RDA) and included in all models. Sensitivity tests of predicted syn-breakup melt generated during lithosphere thinning and breakup were investigated assuming a magma-poor and a normal non-volcanic margin. The Bight Basin shows an apparent crustal segmentation between the Eyre-Recherche and the Ceduna-Recherche sub-basins. Whilst the lateral variation of lithosphere thinning in the Ceduna-Recherche sub-basin is gradual, in the Eyre-Recherche it is abrupt, predicting a highly extended continental crust underneath the Recherche sub-basin. Predicted ocean-continent transition (OCT) widths for the Bight Basin range from approximately 100 km to a maximum of 200 km, although the structure of the OCT itself is unclear. The predicted OCT determined from flexural backstripping compared with independent estimates of basement thickness derived from gravity inversion are in general agreement. Linear marine magnetic anomalies appear to be lying within the predicted OCT of the Bight Basin. If the magnetic anomalies are due to the presence of highly serpentinized peridotites and mafic bodies, the magnetic lineations cannot be used to constrain conventional seafloor spreading.

Legacy product - no abstract available

Legacy product - no abstract available

This abstract describes the pre-breakup structures and history of the conjugate margins of southwest Australia (Naturaliste Plateau) and East Antarctica (Bruce Rise) and the subsequent formation of oceanic crust.

This abstract describes the results of integrated potential firld modelling and deep-seismic interpretation from the Enderby Land and Wilkes Land margins of East Antarctica. The interpretation is based on data acquired under the Australian Antarctic and Southern Ocean Profiling Project.

This record is a report of the operations carried out during Geoscience Australia Survey 229 off the Australian Antarctic Territory from January-April 2002. The survey acquired deep-seismic and potential field data along 8600 km of profiles as a part of the Australian Antarctic and Southern Ocean Profiling Project.

This Record contains a shipboard interpretation of the data acquired on Geoscience Australia Survey 229 off the Australian Antarctic Territory from January-April 2002. The survey acquired deep-seismic and potential field data along 8600 km of profiles as part of the Australian Antarctic and Southern Profiling Project.

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.