As Australia separated from Antarctica and drifted northward the Tasmanian Gateway opened, allowing the Antarctic Circumpolar Current to develop. This current began to isolate Antarctica from the influence of warm surface currents from the north, and an ice cap started to form. Eventually, deepwater conduits led to deepwater circulation between the southern Indian and Pacific Oceans. The existence of these conduits ultimately allowed ocean conveyor circulation. Continuing Antarctic thermal isolation, caused by the continental separation, contributed to the evolution of global climate from relatively warm early Cenozoic ?Greenhouse? to late Cenozoic ?Icehouse? climates. ODP Leg 189 addressed the interrelationships of plate tectonics in the gateway, circum-polar current circulation, climate and sedimentation, and global climatic changes. DSDP drilling had led to a basic framework of paleoenvironmental changes associated with gateway opening, but was not a full test of the various interrelationships. Using the DSDP results, Kennett, Houtz et al. (1975) proposed that climatic cooling and an Antarctic ice sheet (cryosphere) developed from ~33.5 Ma as the ACC progressively isolated Antarctica thermally. They suggested that development of the Antarctic cryosphere led to the formation of the cold deep ocean and intensified thermohaline circulation. Leg 189 gathered data that support this hypothesis. Leg 189 continuously cored sediments in the gateway, which was once part of a Tasmanian land bridge between Australia and Antarctica. The bridge separated the Australo-Antarctic Gulf in the west from the proto-Pacific Ocean to the east. This region is one of the few in the Southern Ocean where almost complete Cenozoic marine sequences could be drilled in paleo-water depths that were shallow enough to allow preservation of calcareous micro-organisms for isotopic studies. The Leg 189 sequences described by Exon, Kennett, Malone et al. (2001) reflect the evolution of a tightly integrated and dynamically evolving system over the past 70 million years, involving the lithosphere, hydrosphere, atmosphere, cryosphere and biosphere. The most conspicuous changes in the region occurred over the Eocene-Oligocene transition (Figure 1) when Australia and Antarctica finally separated. Before the separation, the combination of a warm climate, nearby continental highlands, and considerable rainfall and erosion, flooded the region with siliciclastic debris. Deposition kept up with subsidence. After separation, a cool climate, smaller more distant landmasses, and little rainfall and erosion, cut off the siliciclastic supply. Pelagic carbonate deposition could not keep up with subsidence. Leg 189 confirmed that Cenozoic Antarctic-Australia separation brought many changes. The regional changes included: warm to cool climate, shallow to deep water deposition, poorly ventilated basins to well-ventilated open ocean, dark deltaic mudstone to light pelagic carbonate deposition, microfossil assemblages dominated by dinoflagellates to ones dominated by calcareous pelagic microfossils, and sediments rich in organic carbon to ones poor in organic carbon.

The Arunta Region of central Australia exposes the southern margin of the North Australian Craton and contains a record of multiple Proterozoic craton margin processes over a 1500 million year period. The place of mafic magmatism in this evolution is constrained by SHRIMP U-Pb dating of zircon, which is a primary igneous phase in the evolved sectors of mafic-ultramafic plutons across the region. The earliest mafic magmatism was in the 1800-1810 Ma Stafford Event, which is the first thermal system recognised in the region. Mafic plutons from this event may correlate with other expressions of mafic magmatism northwards within the craton. A second episode of mafic magmatism is recognised at 1770-1790 Ma (Yambah Event) and lacks correlatives elsewhere in the craton, as do all subsequent Arunta Region mafic magmatic events. Zircon overgrowths in Stafford- and Yambah-age plutons record conversion of these early intrusions into granulite grade metamorphic complexes during the Strangways Event, a regionally pervasive metamorphic system whose termination at ca. 1690 Ma coincided with local intrusion of dolerite dykes. Gabbro intrusion at ca. 1640 Ma in the Liebig Event is restricted within the Warumpi Province which is recognised as a separate terrane in the south of the region. There is no record of a mafic magmatic component to the ca. 1590 Ma Chewings event and most of the earlier intrusions do not record metamorphism at this time. Later mafic magmatic systems include pyroxenite intruded as part of the Mordor Complex at ca 1130 Ma (Teapot Event); and both erupted and intruded basaltic magma are components of the fault-bound Irindina Province which experienced high grade metamorphism during the Ordovician (Larapinta Event). The dating establishes that each of these craton margin event systems includes a mafic magmatic component, which suggests that repeated extensional systems are an important component of the tectonic evolution.

Geoscience Australia contributes to a greater understanding of natural hazard and disaster exposure through observations of water from space. This supports Australia's capability to reduce the economic, social and environmental impacts of flood events.

No abstract available - Retired at request of Fellows, M. Incomplete record

The benthic silicate and oxygen fluxes from Moreton Bay sediments were positively correlated (R2 =0.99) and the silicate to organic carbon flux ratio of 0.14 was similar to that for marine diatoms (0.13). The majority (about 75%) of the benthic silicate flux was attributed to the degradation of fresh diatomaceous detritus and the remainder could be contributed from clay (smectite) dissolution in the warm waters (30oC) during these summer months. Biogenic silica in the upper 2 cm of Moreton Bay sediments was enriched (Si:C = 0.35 +/- 0.25) with respect to the Si:C ratio (0.13 +/- 0.04) of dominant diatom populations, and we suggest that this enrichment is the result of the deposition of Si-enriched faecal pellets and diatom aggregates to the sediments. Combined hydrodynamic and biogeochemical processes resulted in distributions of biogenic silica and total organic carbon in the surface sediments that were spatially coincident. A silicate budget for Moreton Bay indicated the following. 1. The benthic input of silicate was balanced approximately by the silicate load to the sediments from primary productivity. 2. Silicate was recycled through diatomaceous phytoplankton about 18 times before it was lost to the ocean. 3. The export of silicate to the Pacific Ocean was about the same as the terrestrial input.

The Australian continent is actively deforming at a range of scales in response to far-field stresses associated with plate margins, and buoyancy forces associated with mantle dynamics. On the smallest scale (101 km), fault-related deformation associated with far-field stress partitioning has modified surface topography at rates of up to ~100 m/Myr. This deformation is evidenced in the record of historical earthquakes, and in the pre-historic record in the landscape. Paleoseismological studies indicate that few places in Australia have experienced a maximum magnitude earthquake since European settlement, and that faults in most areas are capable of hosting potentially catastrophic earthquakes with magnitudes in excess of 7.0. South Australia is well represented in terms of its pre-historic earthquake record. Seismogenic faulting in the last 5-10 million years is thought to be responsible for generating more than 30-50% of the contemporary topographic relief separating the highlands of the Flinders and Mt Lofty Ranges from adjacent plains, and perhaps as much as a third of the strain budget of the entire continent is accommodated there. Adelaide itself straddles several faults which are arguably some Australia's most active. Decisions relating to the siting and construction of the built environment should therefore be informed with knowledge of the local neotectonics.

A new Geoscience Australia Magnetic Anomaly Grid Database of Australia (MAGDA) has been developed. This database contains publicly available airborne magnetic grid data for on- and near-offshore Australia. Flight-line magnetic data for each survey have been optimally gridded and the grids matched in one inverse process. New composite grids at 250 m and 400 m grid spacing form the basis of the new fourth edition of the Magnetic Anomaly Map of Australia. Aeromagnetic traverses flown around Australia during 1990 and 1994 are used in both quality control of the grids they intersect, and also to constrain grid merging by forcing grid data, where intersected, to the level of the traverse data. Although matching and merging of many grids into a seamless compilation produces a pleasing result, without obvious short-wavelength artefacts, accurate long wavelength components of crustal origin are more difficult to obtain. Errors in the ?tilt? of individual surveys, due either to older instrumentation, errors in processing, or incomplete core-field removal, can lead to large long wavelength errors when hundreds of surveys are combined across thousands of kilometres. Quantification of the accuracy of long-wavelength components is only possible by comparison with independent datasets. A low-pass filtered composite grid of the Australian region has been compared with CHAMP satellite magnetic data, and shows a considerable improvement in the correlation of long wavelength components compared with the previous edition

This is an article written as a contribution to the IEA GHG R&D Programme's quarterly newsletter (for publication in the June 2009 edition), at the invitation on the IEA GHG R&D Programme. It describes the release of Australia's offshore acreage for greenhouse gas storage.

The northern Pedirka Basin in the Northern Territory is sparsely explored compared with its southern counterpart in South Australia. Only seven wells and 2500 km of seismic data occur over a prospective area of 73,000 km2. In this basin three petroleum systems have potential related to important source intervals in the basal Jurassic (Poolowanna Formation), Triassic (Peera Peera Formation) and Early Permian (Purni Formation). They are variably developed in three prospective depocentres, the Eringa Trough, the Madigan Trough and the northern Poolowanna Trough. New basin modelling techniques indicate oil and gas expulsion responded to increasing early Late Cretaceous temperatures in part due to sediment loading (Winton Formation). Using a composite kinetic model, oil and gas expulsion from coal rich source rocks were largely coincident at this time when source rocks entered the wet gas maturation window. The Purni Formation coals provide the richest source rocks and equate to the lower Patchawarra Formation in the Cooper Basin. Widespread well intersections indicate that glacial outwash sandstones at the base of the Purni Formation, herein referred to as the Tirrawarra Sandstone, have regional extent and are an important exploration target as well as providing a direct correlation with the prolific Patchawarra/ Tirrawarra petroleum system found in the Cooper Basin. An integrated investigation into the hydrocarbon charge and migration history of Colson-1 was carried out using CSIRO Petroleum's OMI (Oil Migration Intervals), QGF (Quantitative Grain Fluorescence) and GOI (Grains with Oil Inclusions) technologies. In the basal Jurassic Poolowanna Formation between 1984 and 2054 mRT, elevated QGF intensities, evidence of oil inclusions and abundant fluorescencing material trapped in quartz grains and low displacement pressure measurements collectively indicate the presence of palaeo-oil and gas accumulation over this 70 m interval. This is consistent with the current oil show indications such as staining, cut fluorescence, mud gas and surface solvent extraction within this reservoir interval. Multiple hydrocarbon migration pathways are also indicated in sandstones of the lower Algebuckina Sandstone, basal Poolowanna Formation and Tirrawarra Sandstone. This is a significant upgrade in hydrocarbon prospectivity, given previous perceptions of relatively poor quality and largely immature source rocks in the Basin. Conventional structural targets are numerous but the timing of hydrocarbon expulsion dictates that those with an ?older? drape and compaction component will be more prospective than those dominated by Tertiary reactivation which may have resulted in remigration or leakage. Preference should also apply to those structures adjacent to generative source ?kitchens? on relatively short migration pathways. Early formed Tirrawarra Sandstone and Poolowanna Formation stratigraphic traps are also attractive targets. Cyclic sedimentation in the Poolowanna Formation results in two upward fining cycles which compartmentalise the sequence into two reservoir ? seal configurations. Basal fluvial sandstone reservoirs grade upwards into topset shale/ coal lithologies which form effective semi-regional seals. Onlap of the basal cycle onto the Late Triassic unconformity offers opportunities for stratigraphic entrapment.

For more than 30 years, deep seismic reflection profiles have been acquired routinely across Australia to better understand the crustal architecture and geodynamic evolution of key geological provinces and basins. Major crustal-scale breaks have been interpreted in some of the profiles, and are often inferred to be relict sutures between different crustal blocks, as well as sometimes being important conduits for mineralising fluids to reach the upper crust. The widespread coverage of the seismic profiles now provides the opportunity to construct a map of major crustal boundaries across Australia, which will allow a better understanding of how the Australian continent was constructed from the Mesoarchean through to the Phanerozoic, and how this evolution and these boundaries have controlled metallogenesis. Starting with the locations of the crustal breaks identified in the seismic profiles, geological (e.g. outcrop mapping, drill hole, geochronology, isotope) and geophysical (e.g. gravity, aeromagnetic, magnetotelluric) data are used to map the crustal boundaries, in plan view, away from the seismic profiles. For some of these boundaries, a high level of confidence can be placed on the location, whereas the location of other boundaries can only be considered to have medium or low confidence. In other areas, especially in regions covered by thick sedimentary successions, the locations of some crustal boundaries are essentially unconstrained. From the Mesoarchean to the Phanerozoic, the continent formed by the amalgamation of many smaller crustal blocks over a period of nearly 3 billion years. The development of the map of crustal boundaries of Australia will help to constrain tectonic models and plate reconstructions for the geological evolution of Australia, will provide constraints on the three dimensional architecture of Australia, and will suggest regions of higher potential for future mineral exploration.