continental shelf
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Submerged relict reef systems and modern coral communities discovered around the Balls Pyramid shelf are presented as new evidence of extensive carbonate production at the boundary of reef-forming seas. Balls Pyramid is the southernmost island in a chain of island-reefs in the southwest Pacific Ocean, 24 km south of the southernmost known coral reef in the Pacific Ocean at Lord Howe Island. This paper explores the detailed geomorphic structure of the shelf through the production of a high resolution bathymetric model from multibeam echosounder data and depth estimates from satellite imagery. Key seafloor features identified include a large, mid shelf reef dominating the shelf landscape in 20 - 60 m water depth, mid shelf basins and channels, and shelf margin terrace sequences in 50 - 100 m depth. Sub-bottom profiles, backscatter, drill core and vibro-core data are used to investigate the seafloor composition. Drill cores extracted from the submerged reef surface confirm coral, coralline algae and cemented sands composition, and vibro-core material extracted from unconsolidated areas demonstrate substantial accumulation of carbonates shed from the reef surface. Underwater video imagery reveals abundant modern mesophotic reef communities, including hard corals, colonising the relict reef surface. This paper reveals prolific past reef growth and abundant modern coral growth on what was previously considered to be a planated volcanic shelf outside of reef-forming seas, thus extending understanding of reef evolution at, and beyond, the limits of growth.
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Abstract to appear in conference proceedings as part of GA Record
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Physical and biological characteristics of benthic communities are analysed from underwater video footage collected across the George V Shelf during the 2007/2008 CEAMARC voyage. Benthic habitats are strongly structured by physical processes operating over a range of temporal and spatial scales. Iceberg scouring recurs over timescales of years to centuries along shallower parts of the shelf, creating communities in various stages of maturity and recolonisation. Upwelling of modified circumpolar deep water (MCDW) onto the outer shelf, and cross-shelf flow of high salinity shelf water (HSSW) create spatial contrasts in nutrient and sediment supply, which are largely reflected in the distribution of deposit and filter feeding communities. Long term cycles in the advance and retreat of icesheets (over millennial scales) and subsequent focussing of sediments in troughs such as the Mertz Drift create patches of consolidated and soft sediments, which also provide distinct habitats for colonisation by different biota. These physical processes of iceberg scouring, current regimes and depositional environments, in addition to water depth, are shown to be important factors in the structure of benthic communities across the George V Shelf. The modern shelf communities mapped in this study largely represent colonisation over the past 8-12ka, following retreat of the icesheet and glaciers at the end of the last glaciation (Harris et al., 2001; Ingólfsson et al., 1998). Recolonisation on this shelf may have occurred from two sources: deep-sea environments, and possible shelf refugia on the Mertz and Adélie Banks. However, any open shelf area would have been subject to intense iceberg scouring (Beaman and Harris, 2003). Understanding the timescales over which shelf communities have evolved and the physical factors which shape them, will allow better prediction of the distribution of Antarctic shelf communities and their vulnerability to change. This knowledge can aid better management regimes for the Antarctic margin.
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The EM300 Sea Trials survey GA-2354, was acquired by Geoscience Australia after the installation of the new multibeam bathymetry acquisition system EM300 onboard the RV Southern Survey during the 16 to 18th of December 2003. The survey location was offshore Fremantle around the Perth Canyon. The aim of the survey was to test the bathymetry system installed on the vessel. The bathymetry grids consists of 10 and 40m resolution grids projected in Easting and Northing WGS84 UTM 50S.<p><p>This dataset is not to be used for navigational purposes.
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Vlaming Shelf reef polygons were manually digitized from multibeam echosounder datasets collected on marine survey GA0334 in March/April 2012. Reef areas were defined as exposed, hard substrate that are often raised above the surrounding seafloor. They were mapped using bathymetry and backscatter data along with bathymetric derivatives including; slope, hillshaded bathymetry and contours. Features were mapped at a scale of 1:10 000. This dataset is published with the permission of the CEO, Geoscience Australia.
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A nationally-consistent wave resource assessment is presented for Australian shelf (<300 m) waters. Wave energy and power were derived from significant wave height and period, and wave direction hindcast using the AusWAM model for the period 1 March 1997 to 29 February 2008 inclusive. The spatial distribution of wave energy and power is available on a 0.1° grid covering 110'156° longitude and 7'46° latitude. Total instantaneous wave energy on the entire Australian shelf is on average 3.47 PJ. Wave power is greatest on the 3,000 km-long southern Australian shelf (Tasmania/Victoria, southern Western Australia and South Australia), where it widely attains a time-average value of 25-35 kW m-1 (90th percentile of 60-78 kW m-1), delivering 800-1100 GJ m-1 of energy in an average year. New South Wales and southern Queensland shelves, with moderate levels of wave power (time-average: 10-20 kW m-1; 90th percentile: 20-30 kW m-1), are also potential sites for electricity generation due to them having a similar reliability in resource delivery to the southern margin. Time-average wave power for most of the northern Australian shelf is <10 kW m-1. Seasonal variations in wave power are consistent with regional weather patterns, which are characterised by winter SE trade winds/summer monsoon in the north and winter temperate storms/summer sea breezes in the south. The nationally-consistent wave resource assessment for Australian shelf waters can be used to inform policy development and site-selection decisions by industry.
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Comprising 28 maps depicting areas of Australia's maritime jurisdiction,continental shelf, treaties and various maritime zones. Australia's Maritime Jurisdiction - wall map - A0 size, (GeoCat 70362) Australia's Maritime Jurisdiction around Australia, (GeoCat 69122) Australia's Maritime Jurisdiction in the Torres Strait, (GeoCat 68226) Australia's Maritime Jurisdiction in the Timor Sea, (GeoCat 68796) Australia's Maritime Jurisdiction off the Northwest Shelf, (GeoCat 69341) Australia's Maritime Jurisdiction off Central Western Australia, (GeoCat 69488) Australia's Maritime Jurisdiction off Southwestern Western Australia, (GeoCat 69507) Australia's Maritime Jurisdiction in the Arafura and Coral Seas, (GeoCat 69123) Australia's Maritime Jurisdiction in the Coral Sea (North), (GeoCat 69717) Australia's Maritime Jurisdiction in the Coral Sea (South), (GeoCat 69718) Australia's Maritime Jurisdiction in the Tasman Sea, (GeoCat 69721) Australia's Maritime Jurisdiction in the Coral and Tasman Seas, (GeoCat 69738) Australia's Maritime Jurisdiction off South Australia, (GeoCat 69739) Australia's Maritime Jurisdiction around Tasmania - lambert projection, (GeoCat 69863) Australia's Maritime Jurisdiction around Tasmania - mercator projection, (GeoCat 69737) Australia's Maritime Jurisdiction around the State of Tasmania, (GeoCat 70315) Australia's Maritime Jurisdiction around Macquarie Island - lambert projection, (GeoCat 69864) Australia's Maritime Jurisdiction around Macquarie Island - mercator projection, (GeoCat 69740) Australia's Maritime Jurisdiction around Heard Island and McDonald Islands - mercator projection, (GeoCat 69749) Australia's Maritime Jurisdiction around Heard Island and McDonald Islands - lambert projection, (GeoCat 69865) Australia's Maritime Jurisdiction in Bass Strait, (GeoCat 69821) Australia's Maritime Jurisdiction off the Australian Antarctic Territory (East), (GeoCat 69792) Australia's Maritime Jurisdiction off the Australian Antarctic Territory (Centre), (GeoCat 69790) Australia's Maritime Jurisdiction off the Australian Antarctic Territory (West), (GeoCat 69789) Australia's Maritime Jurisdiction around Cocos (Keeling) Islands and Christmas Island, (GeoCat 70099) Australia's Maritime Jurisdiction off Northern Australia, (GeoCat 70183) Australia's Maritime Jurisdiction North of 25°S Australia, (GeoCat 71985) Australia's Maritime Jurisdiction off the Australian Antarctic Territory, (GeoCat 70368) Digital files (.pdf format) downloadable from the web.
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Benthic sediment sampling of Inner Darwin Harbour (GA0358) and shallow water areas in and around Bynoe Harbour (GA0359) was undertaken between May 29 and June 19, 2017. Partners involved in the surveys included Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and the Department of Environment and Natural Resources within the Northern Territory Government (NT DENR) (formerly the Department of Land and Resource Management (DLRM)). These surveys form part of a four year (2014-2018) science program aimed at improving knowledge about the marine environments in the regions around Darwin and Bynoe Harbour’s through the collection and collation of baseline data that will enable the creation of thematic habitat maps to underpin marine resource management decisions. This project is being led by the Northern Territory Government and is supported by the INPEX-led Ichthys LNG Project, in collaboration with - and co-investment from GA and AIMS. This dataset comprises total chlorin and chlorin index measurements made on seabed sediments.
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Australia has developed as a maritime nation, from the reliance on coastal seas for transport and trade to the present day where most of the nation's population, industry, tourism and recreation are located along its coasts. In `A Geology of Australia', we discuss how coastal geological features and processes have strongly influenced the pattern of post-colonial settlement and development of Australia, and how our experience of the coast varies radically depending on our location on the continental margin. Examples are provided of the influence of coastal geology on society as well as the impacts people have had on coastal systems.
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Flythrough movie showing the bathymetry, seabed habitats and biota of the outer continental shelf within the Flinders Commonwealth Marine Reserve (CMR), offshore from Flinders Island northeast Tasmania. The bathymetric image is derived from multibeam sonar collected by Geoscience Australia in 2012 using a 30 kHz Simrad EM3002 system on RV Challenger. Videos and seabed images were collected by the University of Tasmania and CSIRO as part of the same field program. Key features on the shelf bathymetry include low profile reefs, flat sandy seabed and the heads of two submarine canyons. The reefs provide hard substrate for sponge gardens whereas the sand flats are mostly barren. The two submarine canyons are sites of local upwelling, and attract large schools of Tasmanian Striped Trumpeter. The Flinders CMR is a study site for the Marine Biodiversity Research Hub, funded through the National Environmental Research Program (NERP). ..