A short article describing the outcomes of the Tasman Frontier Petroleum Industry Workshop held at Geoscience Australia on 8 and 9 March 2012.

The Tasman Frontier region includes c. 3,000,000 sq km of seabed that is thought to be underlain by crust with continental affinities: the Lord Howe Rise, Bellona Trough, Challenger Plateau, Dampier Ridge, Middleton Basin, Fairway Basin, New Caledonia Trough, Norfolk Ridge System, Reinga Basin, and deep-water parts of Taranaki and Northland basins. We have compiled and interpreted c. 100,000 line km of archival seismic reflection data. Using seismic stratigraphy tied to Deep Sea Drilling Project (DSDP) wells, we identify a tectonic and stratigraphic event that we refer to as the 'Tectonic Event of the Cenozoic Tasman Area' (TECTA). This Middle Eocene to Late Oligocene event involved regional uplift followed by 1-2 km of tectonic subsidence of topographic highs, and >2 km of tectonic subsidence in the New Caledonia Trough. Strata below the TECTA reflector (or seismic unit in some places) are locally folded or reverse faulted. We present seismic-stratigraphic evidence that numerous islands were transiently created by uplift on the Lord Howe Rise during the TECTA event. We suggest that the underlying cause of the TECTA event was initiation of the subduction system that has since evolved into the Tonga-Kermadec system. Note: Abstract for initial submission; acceptance to be confirmed.

In 2009, as part of its Onshore Energy Security Program, Geoscience Australia, in conjunction with the Northern Territory Geological Survey, acquired 373 km of vibroseis-source, deep seismic reflection, magnetotelluric and gravity data along a single north-south traverse from the Todd River in the south to nearly 30 km north of the Sandover Highway in the north. This traverse, 09GA-GA1, is referred to as the Georgina-Arunta seismic line, extends from the northeastern Amadeus Basin, across the Casey Inlier, Irindina and Aileron provinces of the Arunta Region and Georgina Basin to the southernmost Davenport Province. Here, we report the results of an initial geological interpretation of the seismic and magnetotelluric data, and discuss some preliminary geodynamic implications.

Extended abstract version of the abstract (Geocat#73747) submitted in March 2012 and accepted for an oral presentation at the symposium.

Geoscience Australia is currently conducting a study under the National CO2 Infrastructure Plan (NCIP) to assess suitability of the Vlaming Sub-basin for CO2 storage. It involves characterisation of the potential seal, the Early Cretaceous South Perth Shale (SPS), by integrating seismic and well log interpretation into a sequence stratigraphic framework. The SPS, conventionally described as a regional seal deposited during a post-rift thermal subsidence phase, consists of a series of prograding units deposited in a deltaic to shallow marine setting. Mapping of the SPS has revealed differences in the geometries of progradational sequences between the northern and southern areas, related to the type and distance to the sediment source as well as the seafloor morphology. In the northern area, deltaic progradation and aggradation occurred over a flat topography between the two uplifted blocks. The succession is composed of prograding sequences commonly exhibiting sigmoidal to oblique geometries, prograding from the north-east to south-west. In the southern area the topography is more complex due to the presence of several paleotopographic highs associated with pre-existing structures. These sequences are sigmoidal to oblique in cross section. They were deposited in fan shaped lobes, successively infilling paleotopographic lows. Direction of the progradation is from southwest to northeast. The thickness of the SPS varies from 200 m between topographic highs to 700 m in the lows. Sedimentary facies are interpreted to vary from sandy delta front to muddy slope and prodelta deposits. These findings will be used in a 3D geological model for assessing CO2 storage potential.

The Onshore Energy Security Program was funded by the Australian Government for five years (2006-2011) to provide geological information on some of the frontier onshore sedimentary basins in Australia, many of which are underexplored with respect to hydrocarbons. As part of the Onshore Energy Security Program, deep seismic reflection data have been acquired across several frontier sedimentary basins to stimulate petroleum exploration in onshore Australia. In 2009, Geoscience Australia, in conjunction with the Northern Territory Geological Survey, acquired a deep seismic transect 373 km long across (Figure 1) the Georgina Basin and northeast margin of the Amadeus Basin of the Northern Territory.

Many of the onshore sedimentary basins in Australia are underexplored with respect to hydrocarbons. The Onshore Energy Security Program was funded by the Australian Government over five years (2006-2011) for Geoscience Australia to provide precompetitive geoscience data and assessments of the potential of some frontier onshore sedimentary basins for energy resources, including hydrocarbons, uranium, thorium and geothermal energy. The basins studied in this project include the Burke River Structural Zone of the Georgina Basin (northwest Queensland), the Yathong Trough in the eastern Darling Basin (western New South Wales), and the Arrowie Basin (South Australia). The interpretation of deep seismic reflection profiles and petroleum systems maturation modelling was undertaken in these basins to increase the understanding of their petroleum potential. The Arrowie Basin seismic data shows an asymmetrical basin architecture, with the basin fill being ~3800 m at its thickest. Several sequence boundaries are mapped in this seismic section, and are correlated with the sequence boundaries between the major Neoproterozoic stratigraphic groups in the Adelaide Rift System. In the easternmost part of the seismic section, a series of east-dipping thrust faults disrupt the stratigraphic section. The petroleum systems maturation modelling shows that potential Cambrian source rocks are likely immature to mature for oil generation. In contrast, potential Neoproterozoic source rocks are likely to be mature to overmature for oil generation, and immature to mature for gas generation. With hydrocarbon systems clearly present in the Arrowie Basin as shown by bitumen in shallow exploration wells drilled in the 1950's, future work, possibly with a focus on unconventional hydrocarbons, would be warranted. The Burke River Structural Zone of the Georgina Basin seismic data shows the basin is ~65 km wide, with a half-graben geometry, being bounded in the west by a rift border fault. The succession in the basin has a maximum thickness of ~2800 m, with the stratigraphy being relatively flat lying, and thickening towards the west. The petroleum systems maturation modelling shows potential Cambrian source rocks are likely to be oil mature. Significant generation and expulsion probably occurred early in the burial history, in response to Cambrian-Ordovician loading. Expulsion occurred after trap formation in the Neoproterozoic-Cambrian, but before later trap formation in the Devonian. The required long preservation time and unroofing are the major risk factors within the basin. The Yathong Trough of the Darling Basin seismic data interpretation shows that the basin fill consists of a thick succession characterised by alternating high and low amplitude seismic reflections, interpreted to represent the expected Devonian succession mudstones and sandstones. The basement units below the Yathong Trough are interpreted to be Ordovician turbidites and Ordovician-Silurian granites, considered to be part of the Lachlan Orogen. The petroleum systems maturation modelling shows that potential Lower and Middle Devonian source rocks are likely to be overmature for oil generation and mature for gas generation. Generation and expulsion from Lower and Middle Devonian potential marine source rocks occurred early during their burial history, prior to Carboniferous uplift and erosion, and thus, major trap formation. Later burial during the Permian and/or Cretaceous may have resulted in minor gas generation and expulsion from a Middle Devonian potential source rock.

The Onshore Energy Security Program, funded by the Australian Government and conducted by Geoscience Australia, has acquired deep seismic reflection data, in conjunction with State and Territory geological surveys, across several frontier sedimentary basins to stimulate petroleum exploration in onshore Australia. Here, we present data from two seismic lines collected in South Australia and the Northern Territory. Seismic line 08GA-OM1 crossed the Carboniferous to Permian Arckaringa Basin is imaged as a series of depocentres forming the Phillipson and Penrhyn Troughs, with a much thinner succession connecting the depocentres, and extending well to the north. Seismic line 08GA-OM1 also crosses the Neoproterozoic to Devonian eastern Officer Basin. The basin is structurally complex in this area, being dominated by south-directed thrust faults and fault-related folds, providing potential for underthrust petroleum plays. Seismic line 08GA-OM1 also images the southern margin of the Amadeus Basin Seismic line 09GA-GA1 crossed the northeastern part of the Amadeus Basin and the complete width of the southern Georgina Basin in the Northern Territory. Structural and sequence stratigraphic interpretations of the seismic lines will be presented here, to be followed by an assessment of the petroleum potential of the basins. In the northeast, seismic line 09GA-GA1 crosses two parts of the basin separated by the Paleoproteroozic to Mesoproterozoic Casey Inlier. Seismic line 09GA-GA1 was positioned to cross that part of the southern Georgina Basin where the basin has a complex southern margin, with Neoproterozoic stratigraphy being thrust interleaved with basement rocks of the Arunta Region.

The Bureau of Mineral Resources, Geology and Geophysics (BMR) conducted a seismic survey in the Denison Trough, in the western part of the Bowen Basin in Queensland in 1979. The survey continued work commenced in 1978 aimed at delineating the configuration of the trough and providing stratigraphic information from the Permian sequence which, in conjunction with current Geological Survey of Queensland stratigraphic studies, would enable reliable stratigraphic correlations to be made throughout the trough. The survey obtained 265 km of digitally recorded mainly six-fold Common-Depth-Point seismic reflection data.

Australian Governments over the past decade have acquired thousands of kilometres of high-quality deep-seismic reflection data. The deep-seismic reflection method is unique among imaging techniques in giving textural information as well as a cross sectional view of the overall crust, including the character of the middle crust, lower crust, Moho, and any upper mantle features. Seismic reflection data can be readily integrated with other geophysical and geological data to provide an unsurpassed understanding of a region's geological history as well as the mineral and energy resource potential. Continental Australia is made up of four main elements (blocks), separated by orogens. Most boundaries between the elements are deeply rooted in the lithosphere, and formed during amalgamation of Australia. Major boundaries within the elements attest to their individual amalgamation, mostly prior to the final construction of the continent. Many of Australia's mineral and energy resources are linked to these deep boundaries, with modern seismic reflection providing excellent images of the boundaries. All of the seismic surveys have provided new geological insights. These insights have significantly advanced the understanding of Australian tectonics. Examples include: preservation of extensional architecture in an otherwise highly shortened terrane (Arunta, Yilgarn, Mt Isa and Tanami), unknown deep structures associated with giant mineral deposits (Olympic Dam, Yilgarn, Gawler-Curnamona), as well as the discovery of unknown basins, sutures and possible subduction zones (Arunta, North Queensland, Gawler-Curnamona). These new insights provide not only an improved tectonic understanding, but also new concepts and target areas for mineral and energy resources.