Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

The breakup of Gondwana during the Mesozoic resulted in widespread basin formation along Australia's southern margin, of which the Bight Basin is a component. In contrast to many other extensional margins, the Australian southern margin has been classified as a non-volcanic rifted margin, despite the reported occurrence of scattered volcanic and intrusive rocks in the geological literature. Public release of the Flinders 2D seismic survey data in the Bight Basin has allowed the accurate mapping of widespread sills, dykes, lava flows and volcanoes.

A detailed sequence stratigraphic study has been undertaken on the three wells in the Houtman Sub-basin: Gun Island 1, Houtman 1 and Charon 1. The study focussed on the Early-Late Jurassic Cattamarra Coal Measures, Cadda Formation and Yarragadee Formation succession. Wireline log character, cuttings, sidewall core and conventional core lithologies and palynological data were used to identify facies and paleoenvironments. Palynology for all wells has been reviewed, including new data collected by Geoscience Australia for Gun Island 1. Facies stacking patterns were used to define systems tracts and subsequently ten third-order depositional sequences. At the second-order (supersequence) level, the Cattamarra Coal Measures record a transgression culminating in maximum flooding in the Cadda Formation followed by highstand aggradation and regression in the Yarragadee Formation. The third-order sequences characterised in this study overprint this supersequence and control the local distribution of facies. The relative dominance of a facies may be either enhanced or diminished depending upon its position within the larger second-order supersequence. For example, a number of transgressive systems tracts within the dominantly non-marine Yarragadee Formation and Cattamarra Coal Measures record multiple, dinocyst-bearing, minor marine incursions into the Houtman Sub-basin. These marine incursions are not evident in the Yarragadee Formation in Charon 1, indicating a lack of accommodation space or proximal sediment input in the north during the mid-late Jurassic. The combined influence of these third-order and second-order sequences on facies distribution has significant implications for the distribution of potential reservoirs and seals in the Houtman Sub-basin and for regional palaeogeographic reconstructions of the Perth Basin.

This report was Commissioned by Geoscience Australia for the Western Tasmania Regional Minerals Program (WTRMP). It was completed by SRK Consulting, and is listed as Report AG701. The report covers the interpretation of economic basement in the Bass Basin, and documents the production of a SEEBASE model.

Legacy product - no abstract available

Under the Australian Government's Offshore Energy Program, Geoscience Australia conducted a marine reconnaissance survey GA2476 from October 2008 to January 2009 using the German research vessel RV Sonne. The 90-day marine reconnaissance survey acquired geological and geophysical data over poorly known areas of the Zeewyck and Houtman sub-basins (Perth Basin); the southern Exmouth Sub-basin and Bernier Platform (southern parts of the Carnarvon Basin); and the Cuvier Plateau (also referred to as the Wallaby Plateau). A total of 68 sampling operations recovered rocks during the survey, including 19 over the Zeewyck Sub-basin, 19 over the Houtman Sub-basin, 15 over the southern Exmouth Sub-basin, 13 over the Cuvier Plateau and two over the Bernier Platform. Geological sampling operations were undertaken in water depths ranging from 1,000 to 5,000 m. Fifty-one dredge, 13 grab and three benthic sled hauls as well as one box core recovered several hundred individual rock samples. These rock samples represent the first successful recovery of rock dredges from the Houtman Sub-basin and supplement previous sparsely sampled rocks from frontier Zeewyck Sub-basin, southern Exmouth Sub-basin, Bernier Platform and Cuvier Plateau. The rock hauls yielded a diverse range of rock lithologies including sandstone, claystone, siltstone, mudstones, limestone and minor basalt. Initial micropalaeontological analyses (foraminifera, nannofossils and palynology) of rock samples from the Houtman, Zeewyck and Exmouth sub-basins and the Bernier Platform have shown that most samples fall within two broad stratigraphic intervals: early Cretaceous strata and middle Paleocene to late Eocene strata. For the first time, terrestrial marine sedimentary rocks have been recovered from the southwestern escarpment of the Cuvier Plateau. At least one sample is likely to be Upper Jurassic, making it the oldest known sedimentary sample from the Cuvier Platform.

Understanding of the depth of cover is poor across large areas of Australia. The spectral method is an efficient method of producing reliable depth to magnetic basement estimates across large regions of the continent. A semi-automated work-flow has been created that enables the generation of depth to magnetic source estimates from windowed magnetic data using the Spector and Grant method. The work-flow allows for the correction of the power spectra prior to the picking of straight-line segments to account for the fractal distribution of magnetic sources. The fractal parameter (ß) varies with depth and was determined by picking multiple depth estimates in regions of outcropping magnetic basement which have been upward continued to different levels in order to simulate different amounts of burial beneath non-magnetic sediments. A power law function best approximates the decay of ß with depth. An iterative schema has been incorporated into the workflow which is used to determine the optimum ß where the depths of magnetic sources are unknown. Preliminary testing in a region of known magnetic basement depth has produced encouraging results, although further testing is required. The decrease of ß with increasing depth suggests that the fractal distribution of magnetisation becomes more correlated over larger volumes of observation.

The Australian Southern Margin SEEBASE® Compilation represents many years of work by SRK in southern Australia in the petroleum, mineral and coal sectors. During this time SRK has undertaken numerous projects in southern Australia with both the private and government sectors. These projects have resulted in the development of a model of the geological evolution of southern Australia from Archean to Recent that is summarised in this GIS and report. The model is consistent with a wide range of datasets including airborne and satellite remote sensing, seismic, well and outcrop observations. The basins of Australia's Southern margin formed by the repeated reactivation of long-lived basement structures. By understanding the genesis and geometry of the old basement structures, we have produced a model for the evolution of the Southern Margin basins that explains their structural framework and architecture. This SEEBASE model and structural interpretation can now be used as the basis for a new understanding of the sequence stratigraphy and petroleum systems of the margin.