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  • This document describes a format of the AVNIR-2 (Advanced Bisible Near-Infrared Radiometer) products generaged by the ALOS Data Processing Subsystem.

  • Lithostratigraphy, grain sizes and down-hole logs of Site 1166 on the continental shelf, and Site 1167 on the upper slope, are analyzed to reconstruct glacial processes in eastern Prydz Bay and the development of the Prydz trough-mouth fan. In eastern Prydz Bay upper Pliocene-lower Pleistocene glaciomarine sediments occur interbedded with open-marine muds and grade upward into waterlaid tills and subglacial tills. Lower Pleistocene sediments of the trough-mouth fan consist of coarse-grained debrites interbedded with bottom-current deposits and hemipelagic muds, indicating repeated advances and retreats of the Lambert Glacier-Amery Ice Shelf system with respect to the shelf break. Systematic fluctuations in lithofacies and down-hole logs characterize the upper Pliocene-lower Pleistocene transition at Sites 1166 and 1167 and indicate that an ice stream advanced and retreated within the Prydz Channel until the mid Pleistocene. The record from Site 1167 shows that the grounding line of the Lambert Glacier did not extend to the shelf break after 0.78 Ma. Published ice-rafted debris records in the Southern Ocean show peak abundances in the Pliocene and the early Pleistocene, suggesting a link between the nature of the glacial drainage system as recorded by the trough-mouth fans and increased delivery of ice-rafted debris to the Southern Ocean.

  • A useful spin off of the soft photogrammetry is the opportunity to get one metre contours over the disturbed areas of the Island. For the north-east area of the Island 2km X 2km DEM contour tiles have been trialed in the CIGIS. Most are at a contour interval of 5 metres but tiles 2269 and 2469 have been done at a one metre contour interval. The DEM contours are surface contours. They pick up the reflective surface beneath the aircraft. The reflective surface may be the ground or it may be a dense vegetation canopy or rooftops etc. Further one metre contour coverage can be prepared on a cost recovered basis.

  • This dataset has been digitised from the 1:25000 vegetation map of Christmas Island (accompanying Mitchells 1985 report). The vector version was completed on behalf of Parks Australia Christmas Island. Geoscience Australia used ArcInfo to heads-up digitise a scanned version of the map. Once digitised the arcs were built into polygons and the map was attributed based on the Geoscience Australia data dictionary guidelines. All information relating to vegetation boundaries was extracted from the map and incorporated in the table. The fields that were used follow: Alias Type Width Decimal -----------------------------------------------Shape FIELD_SHAPEPOLY 80Ufi FIELD_DECIMAL 6 0 - unique numberArea FIELD_DECIMAL 18 5Perimeter FIELD_DECIMAL 18 5Code FIELD_CHAR 80 0 - Vegetation unit (map symbol)Descript FIELD_CHAR 64 0 - Description of unitCategories FIELD_CHAR 50 0 - vegetation categoriesFeature FIELD_CHAR 12 0 - (GA field)Plotrank FIELD_DECIMAL 1 0 - (GA field)

  • Laser DEM Grids consists of 27 digital elevation model grids. The Arcview grid files were constructed from the Airborne Laser Scanning shapefiles. The Laser DEM grid tiles cover the eastern portion of the Christmas Island. Each grid contains the height in metres of the ground surface with a value every one metre on the ground.

  • Product no longer exists, please refer to GeoCat #30413 for the data

  • Product no longer exists, please refer to GeoCat #30413 for the data

  • Mining lease boudaries were supplied to Geoscience Australia as many small polygons. Geoscience Australia merged all these polygons to form one theme of mine lease boundaries. This data shows areas where mining of phosphate has been approved. The mine lease theme is mineleases.shp and contains the following fields: Field Type Width Decimal ---------------------------------------------------Shape FIELD_SHAPEPOLY 8 0 Id_lease FIELD_CHAR 8 0 Leasnum FIELD_DECIMAL 5 1 Leasrdcd FIELD_DECIMAL 2 0 Area FIELD_DECIMAL 8 1 Perimeter FIELD_DECIMAL 7 2 Hectares FIELD_DECIMAL 16 3

  • The North West Australian Margin, which has a large hydrocarbon potential, has been studied by combined ocean-bottom seismograph (OBS) and deep reflection profiling along five regional transects which have crossed all major structural elements of this region. Average spacing between the OBSs of 30 km and shot spacing of 100 m with data recording to maximum offsets of 300 km enabled development of accurate crustal-scale seismic velocity models. The thorough wave field analysis, a distinctive feature of our approach to the interpretation of the OBS data, provided realistic starting models for subsequent travel-time inversion by iterative forward modelling. Deep reflection data along the coincident profiles were recorded as part of AGSO's 35,000 km regional grid of seismic lines. Consistent interpretation of several key horizons tied to over 100 petroleum exploration wells through the entire grid created the basis for co-interpretation of the OBS and deep reflection data. Due to the effects of fine seismic stratification of the crust, prominent seismic reflectors and changes in reflectivity patterns imaged by reflection data do not necessarily correspond to significant bulk velocity changes. Velocity variation estimated from the OBS data along the interpreted reflection horizons shows no single simple trend. A number of factors affect this velocity variation and it has to be interpreted individually for individual horizons in different basins. Velocity models improved definition of the basement on the Carnarvon and Canning transects, but it remains problematic in the Vulcan and Petrel sub-basins. Carnarvon Basin is the only one at the NW Australian Margin where the crustal extension is associated with decrease of seismic velocity in the lower crust. Reduction in total crustal thickness beneath the Browse Basin is achieved mostly due to the thinning of the lower crust. Underplating, which is often associated with large-scale extension of the crust, was not a major crustal forming event in the region. It appears to have been restricted only to the offshore Canning Basin and the outer, western part of the Carnarvon Basin. Moho, a difficult target for deep reflection profiling, is imaged by the OBS data quite well. Transition from continental crust to oceanic is accompanied by the non-uniform reduction of crustal thickness from 28-36 km to 8-14 km. The steepest Moho was found next to the continent-ocean boundary in the Canning Basin, where crustal thickness reduces from 34 to 13 km over a distance of ~100 km. On some transects (most of the Canning, Vulcan and Petrel) depth to Moho increases with depth to basement increase, although conventional models of crustal extension suggest otherwise. On the Canning and Petrel transects local Moho highs correspond to the steepest slopes of the basement. These observations have to be accounted for by models of crustal extension. Crust adjacent to the outer boundary of the NWAM studied by the outer parts of the Carnarvon, Browse and, to a lesser degree, Canning transects is not purely oceanic but rather transitional.

  • The technique of reaction-gas chromatography-mass spectrometry (R-GCMS) has been used to characterise the polar fractions of sediment extracts and crude oils. R-GCMS was shown to be rapid, to require only small quantities of sample for analysis and the products formed during analysis were readily identified. To undertake R-GCMS, glass liners for split vaporising injection containing the catalyst, palladium black, were placed into the injection port of a gas chromatograph. Hydrogen gas was used both as an effective reactant for gas phase hydrogenation/hydrogenolysis and as the carrier gas for the subsequent separation. The reaction products were mostly hydrocarbons, which were swept on to the column and readily resolved by the non-polar stationary phase and then identified by mass spectrometry. The fully active catalyst was effective in hydrogenating and isomerising alkenes and partially hydrogenating aromatic moieties. Desulphurisation of thiols, sulphides, and thiophenes also readily occurred. Primary alcohols, acids, esters and ethers were transformed into a hydrocarbon of one carbon atom less, while secondary alcohols were reduced to the parent hydrocarbon. Polar fractions, isolated by column chromatography from the bitumen extracts of the Heartbreak Ridge lignite (Bremer Basin, Western Australia; Eocene age) and the Monterey Formation shale (Naples Beach, USA; Miocene age), reacted to produce compound distributions that were characteristic of the organic matter sources. In contrast, polar fractions from crude oils of the Exxon Program release low to minuscule quantities of hydrocarbons during R-GCMS, and their distributions were remarkably similar to each other and thus not diagnostic of organic matter sources. R-GCMS experiments also demonstrate that asphaltenes, even when redissolved and reprecipitated repeatedly, contain a proportion of functionalised material of low molecular weight.