From 1 - 10 / 20184
  • produced from a 250dpi scanned image of original out-of-print 1966 ed map Available as a product from NT Geological Survey or as a resource from GA Library

  • Milingimbi is situated in the northwest of the Arnhem Land Aboriginal Reserve. The map sheet extends from the northern coast and coastal plains, inland to low undulating country and spectacular escarpment plateau. Milingimbi lies at the northern extent of the McArthur Basin and includes parts of the Pine Creek Inlier in the northwest and the Arafura Basin in the north and east. The oldest rocks exposed are part of the Pine Creek Inlier, comprising Palaeoproterozoic (Orosirian) granite and gneiss of the Nimbuwah Complex. The Pine Creek Inlier was affected by a major tectonic event, the 1870-1850 Ma Barramundi Orogeny, which involved multiple fold generations, regional metamorphism and emplacement of the Nimbuwah Complex intrusives. These units form the basement to the Palaeoproterozoic to Mesoproterozoic McArthur Basin succesion. The oldest unit of the McArthur Basin is the Katherine River Group, which consists of fluviatile, shallow-marine, and minor aeolian units as well as volcanics. The extensive sheet-like sill of the Oenpelli Dolerite intruded at ~1688 Ma. Deposition of the Mt Rigg Group in a post-rifting sag basin extended across the Arnhem Shelf and Walker Trough to the east. The McArthur Basin underwent predominantly brittle deformation during the Proterozoic. 'Post-Nathan Shortening' involving west-northwest-east-southeast compression, resulted in north-northeast-directed thrusting, northeast- and northwest-trending conjugate faulting, and joint development. 'Post-Roper Extension' was characterised by east-west extension and emplacement of dolerite dykes at ~1324 Ma. 'Post-Roper Inversion' involved northeast-southwest compression reactivating northeast- and northwest-trending faults, north-directed thrusting and north-trending dextral strike-slip faulting. Undeformed, shallow-marine sediments of the Neoproterozoic to Middle Cambrian Arafura Basin unconformably overlie the McArthur Basin. A thin cover of Cretaceous shallow-marine sandstone and mudstone mantles the older rocks. Cainozoic alluvium, coastal deposits, laterite and soil cover a large proportion of Milingimbi. Exploration for uranium, bauxite and diamonds has been unsuccessful in locating economic prospects.

  • The Southern Thomson Orogen airborne electromagnetic (AEM) Survey was flown in 2014 using the Geotech VTEMplus® AEM system. The AEM survey was designed by Geoscience Australia, and its partners the geological surveys of New South Wales and Queensland, to help solve geological problems in the Southern Thomson Orogen as part of the UNCOVER Initiative of the National Mineral Exploration Strategy. Survey results indicate variable depth of penetration governed by conductive cover, primarily the Cretaceous Rolling Downs Group, and saline groundwater in broad ephemeral drainage systems including salt lakes and channel country around the Paroo River. The unconformity between the Paleozoic rocks of the Eulo Ridge (a partially-exposed palaeotopographic high) and the overlying Mesozoic and Cenozoic cover is well mapped in the central part of the survey area. The survey data reduce risk to explorers in the area by decreasing uncertainty regarding depth of cover for drilling activities and advising where ground and airborne electromagnetic methods can be expected to produce reliable results. Key words: airborne electromagnetics, depth to basement, cover thickness, UNCOVER.

  • Geoscience Australia (GA) has been developing the National Exposure Information System (NEXIS), a national database of exposure information to identify elements in both the built environment and community that are at risk from natural disasters. A key component of NEXIS is the description of each building including footprint area and height; these geometric characteristics can be derived from LiDAR. This investigation is an assessment of the current abilities of GA and industry partners to provide this data. GA holds LiDAR data representing 70% of the places Australians live, however most of these dataset have not been processed to identify buildings. Five software methods and five industry partners were assessed for their ability to do two main tasks: identify or classify buildings in the LiDAR point clouds, and extract geometric characteristics of buildings. The extracted features were assessed using an urban LiDAR point cloud that has good accuracy and a high data density. Feature-based and area-based assessment methods were developed to assess the output of software packages against a reference building dataset provided by the Launceston Council. The various methods achieved a producer's accuracy between 80% and 90%, user's accuracy between 70% and 90%, and overall accuracy between 90% and 95%.

  • Joining Geoscience Australia's Graduate Program is an exciting opportunity to learn about the diverse earth science disciplines work for the nation's leading government geoscience research and information agency. Posters and Flyers.

  • This report provides a detailed account of several important aspects relating to the organic geochemical analyses of oil, gas and source rocks in the AGSO - Geoscience Australia laboratory. It focuses on the main methods used for the molecular analysis of the sterane, hopane and alkylaromatic biomarkers as well as the stable carbon isotopic (bulk and CSIA) analysis of these materials. In the following description of these methods the areas of sample preparation, instrumental analysis and data processing/reporting are separately addressed.

  • New mapping by Geoscience Australia has identified 713 submarine canyons on the Australian margin and an additional 40 within external territorial seas. Ninety-five canyons are classified as shelf-incising and the remainders are located on the continental slope and classed as blind canyons. A range of metrics were derived to describe canyon form and distribution and used to identify morphologically unique canyons. This poster illustrates this dataset in the context of the national network of Commonwealth Marine Reserves.