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Simple, conceptual geomorphic models can assist environmental managers in making informed decisions regarding management of the coast at continental and regional scales. This basic information, detected from aerial photographs and/or satellite images, can be used to ascertain the relative significance of several common environmental issues, including: sediment trapping efficiency, turbidity, water circulation, and habitat change due to sedimentation for different types of clastic coastal depositional environments.
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Seascapes describing a layer of ecologically meaningful biophysical variable that spatially represent potential seabed habitats have been derived for the Australian margin and adjacent seabed in a new analysis of existing biophysical data. A total of 13 seascapes were derived for the continental shelf and nine seascapes for regions beyond the continental shelf using the unsupervised ISOCLASS classification in the software package ERMapper. The ecological significance of the seascapes is assessed at the national, regional and local scale using existing biological data. Options and avenues for future development are also described.
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The benthic (sea floor) component of the National Marine Bioregionalisation covers the 80% of Australia's Exclusive Economic Zone that lies beyond the continental shelf break. It provides a description of patterns of biological distributions and physical habitats on the seafloor. The Benthic Bioregionalisation Report is a technical document describing how the benthic bioregions were created. It includes descriptions of all the datasets used, details of each bioregion, and examples of how the physical data may be used to sub-divide the marine bioregions for management. An evaluation of the benthic bioregionalisation including strengths, weaknesses and future work is also contained in the report.
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Several gravity cores from the west (3), south (3) and east (5) Australian continental margin have been sampled and analysed for magnetic susceptibility, percent calcium carbonate, Fe203, Al203 and Si02 (% wt) and other trace element contents. Thecores sampled from the west Australian continental margin were from the Exmouth Plateau, and the Carnarvon Terrace. Sampling from the south Australian continental margin was from the west Ceduna Terrace and the Eyre Terrace and the cores sampled from the east Australian continental margin were collected offshore Evans Head. 8180 isotope data on planktonic foraminifera have been used to provide a chronological control on those cores collected from the western margin, to determine sediment accumulation rates and identify Late Quaternary isotopic stages, includingthe last glacial maximum (LGM) and the last interglacial (LIG). These same data are not available from other areas surveyed although sedimentation rates of about 1cm/kyr have been estimated from 14C data from the eastern continental margin sediments offshore Evans Head. The down-core total magnetic susceptibility profiles generally show similar patterns within each survey area. The magnetic susceptibility profiles for those cores from thewestern margin (Exmouth Plateau and Carnarvon Terrace) show relatively high valuesin the Holocene and around the LIG, and relatively low values during the LGM. Patterns of down-core variations in magnetic susceptibility could also be recognised in gravity cores from the eastern margin offshore Evans Head. Here, magnetic susceptibilities were relatively high around the LIG (similar to the western margin), but magnetic susceptibility were low in Holocene sediments, perhaps because of diagenetic remobilisation of iron in the core-tops. In general no distinct patterns are recognisable in the down-core magnetic susceptibility profiles from the southern margin. The down-core profiles of calcium carbonate from the west Australian continental margin show high values during the LGM, and minima in the Holocene and also during the LIG.Similarly, the down-core profile of calcium carbonate shows minimum values during the inferred LIG in eastern margin cores, although this interpretation is based on an approximate sedimentation rate. In general, total magnetic susceptibility is correlated with Al203, Si02 and Fe203, concentrations in sediments, indicating a control on magnetic susceptibility by terrigenous material contents. Calcium carbonate was found tobe a diluent for magnetic susceptibility in these continental margin sediments.
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Management of the marine environment in Australia's Exclusive Economic Zone is addressed by an Oceans Policy that was put forward by the government in 1998. The policy is being implemented through Regional Marine Plans, including the development of a network of representative Marine Protected Areas. The southeast region of Australia has been the first part of the Exclusive Economic Zone to undergo regional marine planning (in 2003) and Marine Protected Area development processes are currently in progress. This article can be found in Geological Association of Canada
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Hydrogeological map data for research and analysis applications, most commonly in GIS systems. Georeferenced, attributed, GIS vector format data of hydrogeological map information at all scales.
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A number of physical properties (water content, porosity, wet and dry bulk densities, andgrain size) and the bulk chemical composition (percent calcium carbonate) of several corescollected from the Australian continental shelf and slope have been determined. Thecontinental shelf sediments were collected from water depths <200m in the Torquay Sub-basin and Vulcan Graben. Continental slope sediments were collected from water depthsof between 500 m and >4000 m offshore Evans Head (NSW), the Exmouth Plateau, thePerth Basin and the Ceduna Terrace in The Great Australian Bight. Trends between physical properties and the bulk chemical composition have beencompared and contrasted for continental shelf and slope sediments. Increasing carbonatecontent for sediments from the continental slope are associated with increasing wet bulkdensities. A second order polynomial fit to the data was similar to that found for deep-sea,southeast Pacific cores examined by Lyle and Dymond (1969). In contrast, the continentalshelf sediments show that with increasing carbonate content there is a decrease in wet bulkdensity, although the data are very scattered and the trend is poorly defined. Data from continental shelf sediments show that with increasing proportions of 'fine-grained' (<631.1m) sediment fraction, there is an increase in porosity. Continental slopesediments show no clear relationship between the porosity of the sediments and thepercentage of 'fine-grained' (< 6311m) sediment fraction. For continental shelf sediments, increasing carbonate content is associated with a decreasein the 'fine-grained' (<63 rim) sediment fraction. The continental slope sediments show norelationship between carbonate content and the percent < 63 gm sediment fraction.
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Australia's near-pristine estuaries are some of our most valuable natural assets, with many natural and cultural heritage values. They are important as undisturbed habitat for native plants and animals, for biodiversity conservation, as Indigenous lands and for tourism. They also support near-shore fisheries. In addition, by studying near-pristine estuaries, scientists can learn more about the way humans have changed natural systems. This information then feeds into natural resource management because it constitutes benchmark or baseline information against which similar information from more modified estuaries can be compared.
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Selected geomorphic features and sedimentary facies were mapped in 283 of Australia's wave- and tide-dominated estuaries and deltas to quantitatively evaluate established evolutionary facies models that depict the evolution of estuaries into deltas during stable sea level conditions. While diagnostic facies for wave- and tide-dominated estuaries and deltas approximate those specified by the models, statistical analyses of the data also reveal two additional insights regarding the evolution of estuaries to deltas. First, there is an offshore shift in the locus of sand accumulation between tide-dominated estuaries and deltas, associated with the onset of delta development. Second, the mean surface area of intertidal environments (i.e., intertidal flats, mangroves/melaleuca, saltmarsh/salt flat facies) is greater in wave-dominated deltas than in wave-dominated estuaries. Tidal penetration associated with the river establishing a more direct and permanent connection to the sea during late-stage development presents a natural impediment to continued formation of an alluvial plain and full development of the 'classic' wave-dominated delta morphology. A notional evolutionary pathway for wave-dominated estuaries is developed from the distribution of facies that predicts the rate and susceptibility of geomorphic and habitat changes. The 'classic' deltaic geomorphology may be unattainable for wave-dominated systems, except those with significant terrigenous sediment inputs. Our study is the first published example of geomorphic and sedimentary data assembled from a large number of wave- and tide-dominated estuaries and deltas across an entire continent.
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Pitcher, C.R., P.J., Doherty, and T.J. Anderson. (2008). Seabed environments, habitats and biological assemblages. pages 51-58. In: Hutchings, P.A., M.J. Kingsford, and O. Hoegh-Guldberg (eds.). The Great Barrier Reef: Biological, Environment and Management. CSIRO Publishing, Springer.