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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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Gravity data are presented for 220 sites covering 180 000 square kilometres in the Prince Charles Mountains area of eastern Antarctica. Bouguer anomalies range from +60 m Gal over the Amery Ice Shelf (near sea level) to -120 m Gal at altitudes above 2000 m on the Antarctic ice cap. Bouguer anomalies correlate with the mass per unit area above sea level in the relation expected for a region in isostatic equilibrium. Smoothed free air anomalies range from +60 to -60 mGal. North-south trending anomalies over the Lambert Glacier and Amery Ice Shelf are thought to be due to a major fault along the Lambert Glacier, and a rift structure under the Amery Ice Shelf. To the west of these structures the free air anomalies trend mainly east-west.
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Upper Permian silicified gymnospenn woods from the Bainmedart Coal Measures (Amery Group) near Beaver Lake, East Antarctica, are described as two new species, Australoxylon bainii and A. mondii, on the basis of morphometric and qualitative characters - including ray anatomy, tracheid shape, and cross-field pit structure. Australoxylon mondii has two forms, one of which is characterised by a distinctive ray architecture comprising semidetached rows of ray cells with intervening gaps bridged by sporadic joins. Wood of Vertebraria could not be distinguished from Australoxylon mondii on microanatomical characters, which suggests that these two organ taxa may represent different parts of the same glossopterid plant. Many characters used traditionally in wood taxonomy could not be applied owing to substantial variation or preservational differences both within and between specimens. Three types of presumed biogenic cavities occur in the woods. Coprolite-containing cavities distributed in seasonal bands represent rare evidence for Permian wood-boring arthropods. Other, irregularly distributed cavities and appositions were probably fonned by pathogenic fungi. Growth-ring analysis indicates a markedly seasonal climate with low to moderate interseasonal variation in wood production. Significant intraseasonal influences on growth are also evidenced by numerous false rings.
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A well-preserved Late Triassic palynoflora from the upper Flagstone Bench Formation, Prince Charles Mountains, East Antarctica, contains taxa that are also widely distributed in coeval Tethyan Laurasian assemblages. The most common and distinctive of these elements in the present assemblage are: Enzonalasporites vigens, E. densus, cf. Ellipsovelatisporites sp., Minutosaccus crenulatus, cf. Rimaesporites aquilonalis, Ovalipollis ovalis, Samaropollenites speciosus, and Duplicisporites scurrilis. The assemblage is assigned to the Australian Minutosaccus crenulatus Zone, and considered to be of Norian age. Gondwanan palynofloras containing these Laurasian elements are assigned to the Onslow Microflora, which is represented by Middle and Late Triassic palynomorph assemblages from Madagascar, western and northern Australia, East Africa, and Peninsular India. Occurrences of the Onslow Microflora appear to be confined to sediments deposited in palaeolatitudes between about 40o-30oS. As well as climatic controls, we suggest that other factors influenced the distribution of the parent floral communities. In particular, availability of migration pathways along Tethyan coastal plains, that were exposed during periods of sealevel regression, was an important factor controlling the rapid dispersal of certain Triassic plants. Marine influence on the present assemblage is evident by the rare spinose acritarchs, and one specimen of a dinocyst of the Shublikodinium-Rhaetogonyaulax plexus; this is the first record of a Triassic dinocyst from Antarctica.
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In its first three years, the Antarctic CRC s Natural Variability Program has focussed research effort on understanding changes in the extent of the East Antarctic ice sheet, the sedimentary processes and biogeochemical cycles affecting shelf sedimentation, and the palaeoceanography of the Southern Ocean. Seismic data from the Prydz trough-mouth fan indicate that it contains a high-resolution time series of the Plio-Pleistocene activity of the Lambert Glacier system. The fan has been prograding from the eastern side of Prydz Bay at least since the Miocene and it contains Plio-Pleistocene sediments, which are 0.8- 1.2 s TWT thick beneath the current shelf break. Radiocarbon dating of shelf sediments indicates that deposition of a Holocene siliceous mud and ooze layer was initiated at about 10 ka BP on the Mac. Robertson Shelf, which is interpreted as coinciding with the retreat of an expanded ice sheet from the shelf break. Geochemical analyses of sediment cores from the Mac. Robertson Shelf suggest significant differences in sediment accumulation between the inner and outer shelf during the Holocene. A core from the outer shelf suggests three episodes of intense diatom production separated by periods of around 1500 years, although long-term average sediment accumulation rates appear to be rather uniform for this location during the middle and late Holocene. In contrast, results for a core from the inner shelf suggest an approximately 7-fold increase in average sediment accumulation rate from the mid to late Holocene, with roughly comparable increases in the accumulation of both biogenic and lithogenic material. Palaeoceanographic studies of the Southern Ocean, using planktonic foraminifera, diatoms and alkenone unsaturation ratios, indicate larger sea surface temperature amplitudes over wider areas of the Southern Ocean during the last glacial maximum than previously suggested by CLIMAP. Our studies offer the possibility of improvements to reconstructed glacial boundary conditions, with wider areal coverage, greater reliability of estimates , and the opportunity for estimation of seasonal dynamics.
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The Mac. Robertson Shelf and western Prydz Bay, on the continental shelf of East Antarctica, were the sites of seismic/coring programs in February- March 1995 and 1997, and of an opportunistic sampling in 1993. Seismic data indicate a prograding sequence, about 200 m thick, dominated by clinoforms, in Palaeogene sediment. Core sampling was accompanied by deployment of a conductivity/temperature/depth probe (CTD), bottom camera and bottom-sediment grab. The Palaeogene sediments overlie Jurassic-Cretaceous sediments or Precambrian basement, and are overlain by thin, olive-green Quaternary diatomaceous ooze and sand. Sampling from the walls and floors of valleys crossing the shelf was on targets defined seismically, and recovered: Weakly lithified black carbonaceous or brown mudstone and siltstone with Paleocene (P4 and Paleocene undifferentiated), Middle Eocene with Globigerinatheka, and other Palaeogene foraminiferid faunas; Paleocene and Eocene pollen, spores and dinoflagellates; Sediments containing a mixture of Palaeogene fossils and Pliocene to Late Pleistocene/ Holocene diatoms and foraminifera; and Evidence of recycling from Permian, Jurassic and Cretaceous sequences. The Palaeogene sediments from the Neilsen Basin and Iceberg Alley contain glauconite and pyrite (the former often, and the latter rarely, pseudomorphic after radiolaria) and, in places, abundant carbonised wood. Radiolaria, teeth and bone fragments are rare. Foraminifera are rare and very dominantly small and calcareous with very few planktonics. The rocks appear to be part of a coastal plain sediment sequence, all weakly lithified, which includes red muddy sandstone and the fossil-bearing lithologies. It is not clear if all the fossil material and enclosing sediments are in situ or have been reworked as fragments into later glacial sediments. The faunas all appear to have accumulated in an inner continental shelf, fully marine environment with temperate-climate water temperature, and where sediment input was high compared with biogenic carbonate production. Several depositional models meet these criteria. Palynology helps define Paleocene and mid-Late Eocene depositional events, the latter marked by the Transantarctic dinocyst flora. The marine Palaeogene can be related to depositional cycles well documented from other parts of the world.
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Magnetic observatories capable of providing long-period results in absolute measures have been operated in Australia and its territories on and off since 1840. As the first such observatory (that at Gottingen, built by Gauss) was erected only eight years earlier, a long tradition has been established in the observational aspects of the science. In 1979 six observatories are operating: one in Papua New Guinea (recently transferred to that countrys Geological Survey), three in Australia, one in the sub-Antarctic, and one in Antarctica. The number and disposition of continental observatories is inadequate. The factors which should be considered in planning any future network are outlined.
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Can you help the Geoscience Australia Library? We are seeking the field notebooks of any geologists who worked for the Bureau of Mineral Resources (BMR) in Antarctica, especially those from the 1950s-80s, to include in our digitisation project. Tucked away in archive boxes in the basement compactus of the Geoscience Australia Library in Canberra, lie over 3500 geol ogical field notebooks. These notebooks contain the observations of BMR geologists from the 1940s onwards as they worked their way across Australia, parts of Papua New Guinea and Pakistan, and the Australian Antarctic Territory. Around 100 Antarctic field notebooks are the focus of a pilot digitisation project to improve access to the rich data they contain and ensure they are preserved for future generations to use.
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A short article as a side bar in the Australian Antarctic Magazine published by the Australian Antarctic Division. The sidebar article will accompany a longer article by Lt Peter Waring of the Royal Australian Navy survey team that conducted a multibeam survey in Casey Harbour during season 2013-14
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Video of the geo-heritage aspects of the rocks of Stornes Peninsula, Larsemann Hills