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This study presents the first analysis of benthic megafauna and habitats on the Sabrina Coast shelf, East Antarctica, encompassing an area that has been proposed as a Marine Protected Area. Analysis of seabed images indicates that this shelf is comprised of a relatively abundant benthic fauna compared to other parts of the Antarctic shelf, and is dominated by brittle stars, polychaete tubeworms and a range of other sessile and mobile taxa. The distribution of taxa across this shelf is strongly related ( = 0.592) to variations in water depth, latitude, substrate type and the occurrence of phytodetritus. Areas with a high percent cover by phytodetritus are associated with muddy/sandy sediments, with relatively high abundances of mobile holothurians and amphipods, while harder substrates have high abundances of brachiopods, various forms of hard bryozoans, polychaete tubeworms, a range of massive and encrusting sponges and sea whips. Brittle stars, irregular urchins and anemones occur throughout. Variations in substrate type largely reflect the scattered distribution of dropstones, which creates habitat heterogeneity at fine-scales. Several taxa are found only on areas of hard substrate, with most of these taxa showing a broad distribution across the study area, indicating that the density of dropstones is sufficient for most sessile invertebrates to disperse across the region. A few taxa (the hexactinellid sponge Anoxycalyx joubini and branching hydrocorals) show a more restricted distribution. The distribution of hydrocorals may be influenced by their limited dispersal capability, while A. joubini is most likely restricted by water depth. The occurrence of dropstones is associated with significant increases in taxa diversity, abundance and percent biological cover, enhancing the overall diversity and biomass of this ecosystem.
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Early Archaean ( >3 b.y. old) metapelites from the Napier Complex of East Antarctica are enriched in MgO and depleted in K2O and Rb compared with late Archaean and Proterozoic metapelites, probably reflecting a higher proportion of mafic to ultramafic material and sodic (tonalitic to granodioritic) felsic igneous rocks in the source. A number of the more magnesian are strongly depleted in Cr, Ni, Cu, and V, and may have been formed by metamorphism of sediments derived from hydrothermally altered mafic or ultramafic igneous rocks. There is evidence for metamorphic depletion of Rb relative to K in these high-temperature granulite facies metapelites, many of which have high K/Rb ratios, and for depletion of U relative to Th in granulite-facies metapelites compared with those of amphibolite facies. The unique occurrence, on a regional scale, of assemblages containing sapphirine + quartz, and osumilite in metapelites of the Napier Complex may be due to their unusual chemical compositions, as well as to exceptionally high temperatures of metamorphism (900-950°C). Such assemblages are found only in the more magnesian rocks (mostly with mg > 0.6) in the Napier Complex, whereas younger metapelites are, with few exceptions, relatively iron-rich. Nevertheless, regional high-grade metamorphism with geothermal gradients sufficiently steep to allow formation of these rare assemblages is likely to have been confined to the Archaean.
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With improving accessibility to Antarctica, the need for proactive intervention, protection and management of sites of intrinsic scientific, historic, aesthetic or wilderness value is becoming increasingly important. Environmental protection and management in Antarctic is unique globally and is managed by provisions contained within the Antarctic Treaty. Whilst these provisions have been primarily utilised to protect sites of biological or cultural significance, sites of geological or geomorphological significance may also be considered. However, in general, sites of geological and geomorphological significance are underrepresented in conservation globally, and, particularly, in Antarctica. Wider recognition of sites of Antarctic geological significance can be achieved by development of a geo-conservation register, similar to geological themed inventories developed elsewhere globally, to promote and recognise intrinsically valuable geological and geomorphological sites. Features on the register that are especially fragile, or otherwise likely to be disturbed, threatened or become vulnerable by human activity, can be identified as such and area management protocols for conservation, under the Antarctic Treaty, can be more readily invoked, developed and substantiated. Area management should mitigate casual souveniring, oversampling and accidental or deliberate damage caused by ill-advised construction or other human activity.
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Video of the geo-heritage aspects of the rocks of Stornes Peninsula, Larsemann Hills
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This study tested and assessed several methods for identifying and describing physical and chemical characteristics of nearshore sediments in East Antarctica. The study emphasised non-destructive techniques that can be used with small volumes of sample. There were three key aims: 1. Provide information about analytical techniques that are non-destructive and can be used on small-volume samples, 2. Apply these techniques to a set of samples where sufficient material is available and compare the results with the outcomes of traditional geochemical techniques, and, 3. Gain additional information on sedimentary processes in the nearshore environment in East Antarctica. Sediment samples from the Antarctic region are especially difficult to collect because of large logistical requirements and are thus highly valuable. Sediment traps are an example of samples with typically small volumes. Such samples provide valuable information about the nature and quantity of marine sediment in the water column and are highly sought after by researchers. By testing characterisation methods on larger samples, this scoping study provides recommendations for analysing small-volume samples, using non-destructive techniques and techniques that can provide additional information to traditional analysis. In this study, laser Raman spectroscopy and infrared spectroscopy were used to provide qualitative mineralogy for calcite, aragonite, and biogenic silica. Microtextural analysis of quartz grains was undertaken with a scanning electron microscope to provide information on the physical transport processes that the sediment has undergone. With this technique we were also able to identify chemical weathering features. Raman spectroscopy is a relatively rapid technique and has simple sample preparation requirements. The technique can target individual grains but can also measure bulk mineralogy. It is a promising technique for distinguishing mineral polymorphs but scope for quantification is limited for multi-component mixtures compared to traditional mineralogical methods like x-ray diffraction (XRD). Infrared spectroscopy is also quick and sample preparation is minimal. The technique requires more sample than will probably be recovered from sediment traps or sediment cores, at least 15 grams. For samples with large proportions of terrigenous sediment, distinguishing biogenic minerals is difficult because of low concentrations. Acquisition of more reference spectra for minerals of interest in marine substrates (particularly biogenic minerals) would be useful for comparing with sample spectra. Microtextural analysis provides detailed information about potential transport processes but sample preparation and analysis is time-consuming when compared to geochemical analysis. The technique is also somewhat destructive as quartz grains need to be cleaned and mounted. We recommend that an absolute minimum of 20 quartz grains is required for microtextural analysis. Microtextural analysis of sediments from near Davis Station suggests reworking of sediments in a subaqueous environment and minimal aeolian transport. There is also evidence of secondary silica precipitation and minor dissolution of quartz grains.
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The Geology of the Northern Jetty Peninsula GIS dataset contains the shapefiles and tables of the basement geology of the Northern Jetty Peninsula in East Antarctica. This dataset is derived from the map product ‘Geology of Northern Jetty Peninsula, Mac.Robertson Land, Antarctica'. Northern Jetty Peninsula, incorporating Else Platform (~140 km2) and Kamenistaja Platform (~15 km2), represents a mostly ice-free low-lying region located on the western flanks of the Lambert Graben. The region is underlain by granulite-facies Proterozoic gneisses and unmetamorphosed Permian sediments.
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With improving accessibility to Antarctica, the need for proactive protection and management of sites of intrinsic scientific, historic, aesthetic or wilderness value is becoming increasingly important. Environmental protection and conservation practise in the Antarctic is globally unique and is managed by provisions contained within the Antarctic Treaty. Whilst these provisions have been primarily utilised to protect sites of biological or cultural significance, sites of geological or geomorphological significance may also be considered. However, in general, sites of geological and geomorphological significance are underrepresented in conservation globally, and, particularly, in Antarctica. Wider recognition of sites of geological significance in Antarctica can be achieved by development of a geo-conservation register, similar to geological themed inventories developed elsewhere in the world, to promote and recognise intrinsically valuable geological and geomorphological sites. Features on the register that are especially fragile, or otherwise likely to be disturbed, threatened or become vulnerable by human activity, can be identified as such and area management protocols for conservation, under the Antarctic Treaty, can be more readily invoked, developed and substantiated. Area management should mitigate casual souveniring, oversampling and accidental or deliberate damage caused by ill-advised construction or other human activity. The recognition of significant geological and geomorphological features within the Antarctic, and their protection, is identified under the current Australian Antarctic Science Strategic plan (under Stream 2.2; Vulnerability and spatial protection)
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Data from surveys along the East Antarctic margin will be presented to provide insights into the diversity and distribution of benthic communities on the continental shelf and slope, and their relationship to physical processes. Seabed video and still imagery collected from the George V shelf and slope and the sub-ice shelf environment of the Amery Ice Shelf indicate that the benthic communities in these regions are highly diverse, and are strongly associated with the physical environment. Variations in seafloor morphology, depth, sediment type and bottom circulation create distinct seabed habitats, such as muddy basins, rugged slope canyons and scoured sandy shelf banks, which are, in turn, inhabited by discrete seabed communities. The infauna dominated muddy basins contrast sharply with the diverse range of filter-feeding communities that occur in productive canyons and rugged inner shelf banks and channels. In the sub-ice shelf environment, differences in organic supply, linked to the circulation patterns, cause distinct differences in the seabed communities. The strong association between benthic communities and seafloor characteristics allows physical parameters to be used to extend our knowledge of the nature of benthic habitats into areas with little or no biological data. Comprehensive biological surveys of benthic communities in the East Antarctic region are sparse, while physical datasets for bathymetry, morphology and sediment composition are considerably more extensive. Physical data compiled within the proposed network of East Antarctic Marine Protected Areas (MPAs) is used to aid our understanding of the nature of the benthic communities. The diversity of physical environments within the proposed MPAs suggests that they likely support a diverse range of benthic communities.
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A review, mainly of East Antarctic late Cainozoic (post 40 Ma) geological and geomorphological evidence, supports the hypothesis of the continuous presence of an ice sheet, of about the present size, since the late Miocene. Evidence is presented and the view advanced that, during the late Wisconsin maximum of isotope stage 2, ice was not nearly as thick or extensive over the continental shelf as required by the model of maximum Antarctic glaciation, Some of the factors influencing the contribution of Antarctica to post-glacial sea-level rise are discussed. It is considered that Antarcticas contribution was probably considerably less than previously estimated.
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A helicopter survey has mapped gravity and magnetic anomalies and ice thickness over a 100 km by 100 km ice cap area, inland from coastal outcrops of Archaean and Late Proterozoic rocks of the Princess Elizabeth Land coast. The gravity and magnetic anomalies indicate that there is no major change in crustal structure across the boundary between Archaean and Lake Proterozoic rocks. The Archaean rocks of the Vestfold Hills do not extend further inland, but they may extend under Prydz Bay or as a narrow coastal strip under ice inland from the West Ice Shelf, 150 km to the northeast of the Vestfold Hills. Late Proterozoic rocks probably underlie most of the ice cap along the coast.