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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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Continued research In late Palaeozoic palynological biostratigraphy In Australia since about 1970 permits the delineation of a series of informally defined palynostratigraphic units In both Western and eastern Australia. The units include both informal assemblage zones and taxon-range-zones. In the older, pre-glacial (and periglacial) part of the Carboniferous, two palynofloras, designated the Granulatisporite. frustulentus and the Secarisporites Microfloras are recognised. The Granulatisporites frustulentus Microflora is subdivided Into the Grandispora spiculifera Assemblage, of Tournaisian age, and the Anapiculatisporites largus Assemblage, which spans the early to late Visean Interval. The succeeding Secarisporites Microflora, the contents of which are incompletely described, is subdivided into three: the Grandispora maculosa, Anabaculites yberti, and Potonieisporites Assemblages. The Secarisporites Microflora characterises strata ranging in age from late Visean to perhaps Missourian. The preglacial palynofloras are best known from the Canning and Bonaparte Gulf Basins in Western Australia, but are known in eastern Australia from scattered localities in the Drummond Basin and the New England Block. For the later Carboniferous and Permian, palynostratigraphic schemes have developed independently in Western and eastern Australia. In Western Australia, the Canning Basin interval commencing with the glacials of the Grant Formation at the base, and extending to the top of the Liveringa Formation, has provided the stratigraphic standard for the definition of eight informal palynological assemblages, designated Units I to VIII. These span a time Interval approximately equivalent to the Missourian to late Guadalupian. In eastern Australia, the palynostratigraphic schemes currently in use represent modifications of the palynological Stages synthesised by Evans (1969). Subdivisions within these stages are based in most cases on the first appearances of individual form-species; two subdivisions have been described within both Stages 2 and 3, three within Stage 4, and four within Stage 5. Correlation of these new units with the assemblage units described from Western Australia is tentative at present. The subdivisions of Evans scheme have been identified within, inter alia, the Bowen, Cooper, Galilee, Sydney, and Tasmania Basins. Recent studies in Antarctica have compared palynological assemblages from the central Transantarctic Mountains and south Victoria Land with eastern Australian palynofloras: Stages 2, 4, and 5 have been identified from these areas. Assemblages from the Prince Charles Mountains have been referred to Stage 5.
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Highly magnesian (mg about 98) granulites, containing sapphirine, enstatite, spinel, phlogopite, and cordierite, occur as xenoliths in Precambrian orthopyroxene-bearing granitic rocks at Mawson and Gage Ridge, East Antarctica. At Mawson, a marginal reaction zone is considerably enriched in Fe, K, and volatiles H2O and F, largely at the expense of Mg, with the development of sapphirine + phlogopite-rich assemblages. At gage ridge, marginal gain of Fe and to some extent Ca and Na, and loss of Mg are indicated, but there was no significant gain of K or H2O, possibly because very low P(H2O) did not allow crystallisation of phlogopite. (Auth.)
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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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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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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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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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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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The Brattstrand Paragneiss, a highly deformed Neoproterozoic granulite-facies metasedimentary sequence, is cut by three generations of ~500 Ma pegmatite. The earliest recognizable pegmatite generation, synchronous with D2-3, forms irregular pods and veins up to a meter thick, which are either roughly concordant or crosscut S2 and S3 fabrics and are locally folded. Pegmatites of the second generation, D4, form planar, discordant veins up to 20-30 cm thick, whereas the youngest generation, post-D4, form discordant veins and pods. The D2-3 and D4 pegmatites are abyssal class (BBe subclass) characterized by tourmaline + quartz intergrowths and boralsilite (Al16B6Si2O37); the borosilicates prismatine, grandidierite, werdingite and dumortierite are locally present. In contrast, post-D4 pegmatites host tourmaline (no symplectite), beryl and primary muscovite and are assigned to the beryl subclass of the rare-element class. Spatial correlations between B-bearing pegmatites and B-rich units in the host Brattstrand Paragneiss are strongest for the D2-3 pegmatites and weakest for the post-D4 pegmatites, suggesting that D2-3 pegmatites may be closer to their source. Initial 87Sr/86Sr (at 500 Ma) is high and variable (0.7479-0.7870), while -Nd500 tends to be least evolved in the D2-3 pegmatites (-8.1 to -10.7) and most evolved in the post-D4 pegmatites (-11.8 to -13.0). Initial 206Pb/204Pb and 207Pb/204Pb and 208Pb/204Pb ratios, measured in acid-leached alkali feldspar separates with low U/Pb and Th/Pb ratios, vary considerably (17.71-19.97, 15.67-15.91, 38.63-42.84), forming broadly linear arrays well above global Pb growth curves. The D2-3 pegmatites contain the most radiogenic Pb while the post-D4 pegmatites have the least radiogenic Pb; data for D4 pegmatites overlap with both groups. Broad positive correlations for Pb and Nd isotope ratios could reflect source rock compositions controlled two components. Component 1 (206Pb/204Pb-20, 208Pb/204-43, Nd -8) most likely represents old upper crust with high U/Pb and very high Th/Pb. Component 2 (206Pb/204Pb -18, 208Pb/204Pb~38.5, -Nd500 -12 to -14) has a distinctive high-207Pb/206Pb signature which evolved through dramatic lowering of U/Pb in crustal protoliths during the Neoproterozoic granulite-facies metamorphism. Component 1, represented in the locally-derived D2-3 pegmatites, could reside within the Brattstrand Paragneiss, which contains detrital zircons up to 2.1 Ga old and has a wide range of U/Pb and Th/Pb ratios. The Pb isotope signature of component 2, represented in the 'far-from-source' post-D4 pegmatites, resembles feldspar Pb isotope ratios in Cambrian granites intrusive into the Brattstrand Paragneiss. However, given their much higher 87Sr/86Sr, the post-D4 pegmatite melts are unlikely to be direct magmatic differentiates of the granites, although they may have broadly similar crustal sources. Correlation of structural timing with isotopic signatures, with a general sense of deeper sources in the younger pegmatite generations, may reflect cooling of the crust after Cambrian metamorphism.
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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.