The Bremer Sub-basin, which forms part of the Bight Basin off the southern coast of Western Australia, is a deep-water (100-4000 m water depth) frontier area for petroleum exploration. No wells have been drilled to test the sub-basin's petroleum potential, with company exploration limited to a regional seismic survey by Esso Australia Ltd in 1974. Early studies identified the Bremer Subbasin as a series of Middle Jurassic-Early Cretaceous half graben, which contain potentially prospective structures for trapping hydrocarbons. However, a lack of sub-surface geological data, along with the deep-water setting, discouraged exploration of this area for over 30 years. In 2003, the Bremer Sub-basin was identified as a key frontier area in Geoscience Australia's New Oil Program where new exploration opportunities might occur. Subsequently, Geoscience Australia's Bremer Sub-basin Study commenced in 2004 with an aim to determine if the sub-basin formed under suitable geological conditions to generate and trap large volumes of hydrocarbons.

Geological framework of the South Tasman Rise and East Tasman Plateau: structure, tectonics, basin development

This document will be posted on the GA and CSIRO-Marine websites. Dr. Neville Exon was Chief Scientist and Cruise Leader for this survey.

The seismic stacking velocity data in the Great Australian Bight are a useful dataset for calculating depths and sediment thicknesses. This work compares these data with P-wave velocities from sonobuoys and sonic logs from wells, and on this basis a depth over-estimate of at least 15% can be expected from the depths derived from stacking velocities. Megasequence boundary depths are calculated for the Ceduna Terrace to further illustrate data quality. The database makes avaliable the unfiltered stacking velocities using conventional and horizon-consistent formats.

The 4-10 km-thick Bangemall Supergroup, comprising the Edmund and Collier groups, was deposited between 1620 Ma and 1070 Ma in response to intracratonic extensional reactivation of the Paleoproterozoic Capricorn compressional orogen. The supergroup can be further divided into six depositional packages bounded by unconformities or major marine flooding surfaces. Samples of each of the major sandstone units within these packages have been collected for detrital zircon provenance analysis. U-Pb dating of over 1200 detrital zircon grains has failed to identify any syndepositional magmatism, but provides an extensive dataset for evaluating the provenance history of the Bangemall Supergroup and implications for the Mesoproterozoic paleogeography of the West Australian Craton. Integration of this detrital zircon data with palaeocurrent data indicates that all source areas were located within the Mesoproterozoic West Australian Craton, with the main source area for the northern Bangemall Supergroup being the Gascoyne Complex and southern Pilbara Craton. All samples have prominent age modes in the 1850-1600 Ma range, indicating significant contribution from the northern Gascoyne Complex and coeval sedimentary basins. Some samples also display prominent modes in the 2780-2450 Ma range, consistent with derivation from the Fortescue and Hamersley groups. The provenance history of the Edmund Group records unroofing of the underlying basement, from the Gascoyne Complex to the Archean granites and greenstones of the Pilbara Craton. This results in detrital age-spectra in which the dominant modes become older upwards. In contrast, the Collier Group records unroofing of the underlying Edmund Group, and is characterized by age-spectra in which the dominant modes become younger upwards. These data imply that the West Australian Craton remained intact throughout the Mesoproterozoic assembly of Rodinia, and was the only source of detritus for the Bangemall Supergroup. Keywords: Bangemall Supergroup, Edmund Group, Collier Group, paleocurrents, provenance, zircon

This report (Record 2009/38) contains the description and preliminary analysis of datasets acquired during Geoscience Australia marine reconnaissance survey GA2476 to the west Australian margin. The survey, completed as part of the Federal Government's Offshore Energy Program, was undertaken between 25 October 2008 and 19 January 2009 using the German research vessel RV Sonne. The survey acquired geological, geophysical, oceanographic and biological data over poorly known areas of Australia's western continental margin. Data from the marine reconnaissance survey (GA2476) and the concordant regional seismic survey (GA0310) will improve knowledge of frontier sedimentary basins and marginal plateaus and allow assessment of their petroleum prospectivity and environmental significance. These data will be used to improve resource management and underpin decisions regarding future acreage release in offshore Western Australia and marine zone management. Four key areas were targeted: the Zeewyck and Houtman sub-basins (Perth Basin), the Cuvier margin (northwest of the Southern Carnarvon Basin), and the Cuvier Plateau (a sub-feature of the Wallaby Plateau). Over the duration of the survey a total of 229,000 km2 (26,500 line-km) of seabed was mapped with the multi-beam sonar, 25,000 line-km of digital shallow seismic reflection data and 25,000 line-km of gravity and magnetic data. A variety of sampling equipment was deployed over the duration of the survey, including ocean floor observation systems (OFOS), deep-sea TV controlled grab (BODO), boxcores, rock dredges, conductivity-temperature-depth profilers (CTD) and epibenthic sleds. A total of 62 stations were examined throughout the survey, including 16 over the Houtman Sub-basin, 16 over the Zeewyck Sub-basin, 13 in the Cuvier margin, 12 over the Cuvier Plateau and four in the Indian Ocean. This report is intended to provide a comprehensive overview of the survey activities, equipment used and preliminary results form survey GA2476.

The investigation of the Fitzroy Basin and adjacent areas was commenced in 1948 when a detailed survey was made of the Nerrima Structure and a widespread reconnaissance by land, sea and air was completed. The Fitzroy Basin survey was completed in 1952 and during this period 24 months were spent in the field and the remainder in office preparation. Approximately 40,000 square miles were examined during the survey and detailed maps covering an area of 28,000 square miles have been prepared at 1 inch = 1 miles, 1 inch = 2 miles and 1 inch = 10 miles. The area has been examined in the past in varying detail by three geological parties on behalf of local and overseas oil companies. The purpose of this survey was to examine the complete sedimentary sequence in sufficient detail to solve the problems encountered by previous surveys and eventually to be in a position to assess to a reliable degree the petroleum prospects of the area based on the examination of surface outcrop. The assessment of the petroleum prospects of the area has very definite limitations in that the potential source rocks (Devonian and Ordovician) are limited to the extreme eastern margin of the basin and nothing is known about their distribution or facies elsewhere under the cover of Permian and Mesozoic sediments. The aerial photography of the area, which was conducted by the Survey Squadron of the Royal Australian Air Force, has been the basis of all mapping, as reliable topographic maps of the area were not available.

No abstract available

Geoscience Australia's Bremer Sub-basin Study is providing the first new frontier exploration opportunity under the Commonwealth Government's New Oil program.

Geodynamic modelling of selected aspects of the Bowen, Gunnedah, Surat and Eromanga basins constrains the mechanisms that were operating during their formation. For the Bowen and Gunnedah basins, a quantitative analysis of the early Late Permian to Middle Triassic foreland loading phase examined the relative roles of static loading versus dynamic loading associated with the convergent plate margin. Subsidence in the initial foreland phase in the early Late Permian is consistent with platform tilting due to corner flow in the mantle associated with west-directed subduction. Later in the Late Permian, platform tilting probably continued to be the dominant cause of subsidence, but increasing amounts of subsidence due to foreland loading occurred as the thrust front in the New England Orogen migrated westward. In the latest Permian and Early Triassic, static flexural loading due to foreland loads is dominant and may be the sole cause for basin subsidence. For the Surat and Eromanga basins, the tectonic subsidence across an east-west transect is modelled to assess the contribution of dynamically-induced platform tilting, due to viscous mantle corner flow, in basin subsidence. The modelling suggests that subsidence was again controlled by dynamic platform tilting, which provides a mechanism for both the nearfield and farfield effects. Uplift of the Eastern Highlands in the mid-Cretaceous may also be related to viscous corner flow driven by west-directed subduction beneath eastern Australia, with the uplift being due to rebound of the lithosphere after the cessation of subduction.