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  • Speculation is increasing that Proterozoic eastern Australia and western Laurentia represent conjugate rift margins formed during breakup of the NUNA supercontinent and thus share a common history of rift-related basin formation and magmatism. In Australia, this history is preserved within three stacked superbasins formed over 200 Myr in the Mount Isa region (1800-1750 Ma Leichhardt, 1730-1670 Ma Calvert and 1670-1575 Ma Isa), elements of which extend as far east as Georgetown. The Mount Isa basins developed on crystalline basement of comparable (~1840 Ma) age to that underlying the Paleoproterozoic Wernecke Supergroup and Hornby Bay Basin in NW Canada which share a similar tripartite sequence stratigraphy. Sedimentation in both regions was accompanied by magmatism at 1710 Ma, further supporting the notion of a common history. Basin formation in NW Canada and Mount Isa both concluded with contractional orogenesis at ~1600 Ma. Basins along the eastern edge of Proterozoic Australia are characterised by a major influx of sediment derived from juvenile volcanic rocks at ~1655 Ma and a significant Archean input, as indicated by Nd isotopic and detrital zircon data. A source for both these modes is currently not known in Australia although similar detrital zircon populations are documented in the Hornby Bay Basin, and in the Wernecke Supergroup, and juvenile 1660-1620 Ma volcanism occurs within Hornby Bay basin NW Canada. These new data are most consistent with a northern SWEAT-like tectonic reconstruction in a NUNA assembly thus giving an important constraint on continental reconstructions that predate Rodinia.

  • The Ord Valley Airborne Electromagnetics (AEM) Interpretation Project was undertaken to provide information in relation to salinity and groundwater management in the Ord River Irrigation Area (ORIA), and to guide its future expansion. The project included the acquisition of 5,936 line km of AEM data acquired using the SKYTEM time domain system, the acquisition of a Light Ranging and Detection (LiDAR) survey, and complementary drilling, borehole geophysics, laboratory analysis and interpretation services. Within the limits of available bore data and the scales of airborne data acquisition, this study provided greater spatial detail on critical elements of the hydrostratigraphy in the sedimentary alluvial aquifer systems. This included the indicative 3D extent and thickness of gravel, sand, silt, clay units as well as salt stores and groundwater quality. It also produced first generation of salinity hazard maps. The AEM mapping identified discrete palaeochannels, interpreted as elements of the palaeo-Ord drainage system. Overall, the amount and extent of gravel and sand aquifers present in the study area was significantly less than previously thought, with gravel aquifers present in laterally confined palaeochannel systems. There was also several buried bedrock ridges and shallow pediments that were interpreted to reduce aquifer storage and throughflow. In the Mantinea Plain-Carlton Hill-Parry's Lagoon area, the presence of a marine sand aquifer containing very saline groundwater was confirmed. The 3D mapping provided an important framework for hydrodynamic analysis and hydrogeochemical process studies. In summary, the project demonstrated the potential for 'calibrated' AEM systems and iTEM Fast Approximate Inversion software to shorten project timelines for studies that involve the analysis and interpretation of AEM data.

  • Out of Gondwana Marita Bradshaw, Jennie Totterdell, George Gibson, irina Borissova, John Kennard 'Out of Gondwana' is a chapter of the new book on Australia's geology being published by Geoscience Australia for the 34th International Geological Congress (IGC) to be held in Brisbane in 2012. As part of this book, Shaping a continent-building a nation: a geology of Australia, this chapter will tell the story of the break up and creation of Australia as the island continent, and how this unique geology has impacted the Australian people. Geoffrey Blainey recognises climate and distance as the two major influences on the historical development of Australia and Australians; and the 'tyranny of distance' was established with the separation from Gondwana. But the Gondwanan history has also bestowed resource riches - coal, gas and oil - which power the Australian economy today.

  • Multibeam sonar mapping, drill cores and underwater video data have confirmed the existence of a previously unknown reef province in the Gulf of Carpentaria, Australia. Seven reefs, comprised of coral limestone that support living corals have been mapped so far and as many as 50 other reefs may exist in the region. U/Th ages show that reef growth commenced shortly after limestone pedestals were submerged by rising sea level around 10.5 kyr BP, making them the oldest reefs known in Australia. Reef growth persisted for ~2.0 kyr but it had ceased at most locations by ~8.0 kyr BP. Measurements of reef growth rates (0.95 to 4 m kyr-1), indicate that the reefs were unable to keep pace with contemporaneous rapid sea level rise (>10 m kyr-1), which is consistent with a 'give up' reef growth history. Core samples from reef platforms demonstrate that Pleistocene limestone is exposed in depths of 27 and 30 m below present mean sea level. These depths represent regionally significant phases of reef growth during a prolonged sea level still stand. We conclude that the reefs are therefore mostly relict features, whose major phase of growth and development relates to an earlier, pre-Holocene sea level stillstand.

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  • Previously undated post Devonian sediments are shown by plant macro- and microfossils to be Early Cretaceous, and thus part of the Eromanga Basin. Modern landscape in the northern Barrier Ranges results from differential erosion following post-Early Cretaceous deformation that folded these and underlying rocks, most probably in response to reverse movements on faults at the western margin of the Bancannia Trough.

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