Though funding is an important issue, factors including lack of success and psychological stress play a greater role in influencing the decision to discontinue treatment. Better information and support are needed to improve the continuation rates.
Abstract:In situ cosmogenic 10 Be exposure dating, radiocarbon determinations, salt and sediment geochemistry, and rock weathering observations indicate that parts of Larsemann Hills, East Antarctica have been subaerially exposed throughout much of the last glacial cycle, with the last glaciation occurring prior to 100 ka BP. Salt-enhanced subaerial weathering, coupled with a paucity of glacial erratics, made exposure age dating challenging. Rapid subaerial surface lowering in some places means that some exposure ages may underestimate the true age of deglaciation. Despite this uncertainty, the data are consistent with the absence of overriding by a thick ice sheet during the Last Glacial Maximum ,20-18 ka BP.
The geomorphology of Heard Island± McDonald Island is primarily the product of close interplay between volcanism, glaciation, and vigorous marine processes in a stormy sub-Antarctic environment. The dominant landform is the strato-volcano Big Ben (2745 m), which is the highest mountain on Australian territory outside Antarctica. Other volcanic landforms include scoria cones, domes, open vertical volcanic conduits, lava ¯ows and lava tubes. Volcanic activity is ongoing from the summit of Big Ben, and from Samarang Hill on McDonald Island. Early, but unproven, glacial sediments may exist within the Late Miocene± Early Pliocene Drygalski Formation, which forms a 300 m high plateau along the northern coast of Heard Island. Growth of the present glaciers, some of which reach sea level, has been a response to progressive growth of the volcanoes. A variety of erosional and depositional glacial landforms is present, including major lateral moraines and extensive hummocky moraines. Vigorous longshore drift and an abundant sediment supply have produced a large spit at the downdrift end of the island, and formed bars from reworked glacigenic sediment that now impound proglacial estuarine lagoons, some of which have grown rapidly over recent decades as tidewater glaciers have retreated. Integrated study of the volcanic, glacial and coastal sequences offers the possibility of constructing a well-dated record of climate change. Research into the geomorphology, sur® cial sediments, and contemporary geomorphological processes, including glacio¯uvial sediment ¯ux, is also important as an aid to environmental management on land, and to management of the adjacent marine environment.
A Pliocene (2.6-3.5 Ma) age is determined from glacial sediments studied in a 20 m long, 4 m deep trench excavated in Heidemann Valley, Vestfold Hills, East Antarctica. The age determination is based on a combined study of amino acid racemization, diatoms, foraminifera, and magnetic polarity, and supports earlier estimates of the age of the sedimentary section; all are beyond 14 C range. Four till units are recognized and documented, and 16 subunits are identified. All are ascribed to deposition during a Late Pliocene glaciation that was probably the last time the entire Vestfold Hills was covered by an enlarged East Antarctic Ice Sheet (EAIS). Evidence for other more recent glacial events of the 'Vestfold Glaciation' may have been due to lateral expansion of the Sørsdal Glacier and limited expansion of the icesheet margin during the Last Glacial Maximum rather than a major expansion of the EAIS. The deposit appears to correlate with a marine deposition event recorded in Ocean Drilling Program Site 1166 in Prydz Bay, possibly with the Bardin Bluffs Formation of the Prince Charles Mountains and with part of the time represented in the ANDRILL AND-1B core in the Ross Sea.
The presence of glacial sediments across the Rauer Group indicates that the East Antarctic ice sheet formerly covered the entire archipelago and has since retreated at least 15 km from its maximum extent. The degree of weathering of these glacial sediments suggests that ice retreat from this maximum position occurred sometime during the latter half of the last glacial cycle. Following this phase of retreat, the ice sheet margin has not expanded more than ∼ 1 km seaward of its present position. This pattern of ice sheet change matches that recorded in Vestfold Hills, providing further evidence that the diminutive Marine Isotope Stage 2 ice sheet advance in the nearby Larsemann Hills may have been influenced by local factors rather than a regional ice-sheet response to climate and sea-level change.
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