Browsing by Author "McKelvey, BC"

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    Cenozoic landscape evolution of an East Antarctic oasis (Radok Lake area, northern Prince Charles Mountains), and its implications for the glacial and climatic history of Antarctica
    (Elsevier, 2007-03) Hambrey, MJ; Glasser, NF; McKelvey, BC; Sugden, DE; Fink, D
    Ice-free areas Antarctica reveal a multi-million year history of landscape evolution, but most attention up to now has focused on the Transantarctic Mountains. The Amery Oasis in the northern Prince Charles Mountains borders the Lambert Glacier-Amery Ice Shelf System that drains 1 million km(2) of the East Antarctic Ice Sheet, and therefore provides a record of fluctuations of both local and regional ice since the ice sheet first formed in early Oligocene time. This glacial record has been deciphered by (i) geomorphological mapping from aerial photographs and on the ground, (ii) documenting the relationship between thick well-dated, uplifted glaciomarine strata and the underlying palaeolandscape, (iii) examining surficial sediment facies, and (iv) surface-exposure dating using Be-10 and Al-26. The SE Amery Oasis records at least 10 million years of landscape evolution beginning with a pre-late Miocene phase of glacial erosion, followed by deposition of glaciomarine strata of the Battye Glacier Formation (Pagodroma Group) in late Miocene time. A wet-based ice sheet next expanded over the SE Amery Oasis, following which deposition of the glaciomarine Pliocene Bardin Bluffs Formation (Pagodroma Group) took place. Both formations were uplifted;, by at least 500 and 200m, respectively. Their tops are characterised by geomorphological surfaces upon which intensive periglacial activity took place. Higher-level bedrock areas were subjected to deep weathering and torformation. Early Pleistocene time was characterised by expansion of a cold-based ice sheet across the whole area, but it left little more than patches of sandy gravel and erratic blocks. Late Pleistocene expansion of local ice (the Battye Glacier) saw deposition of moraine-mound complexes on low ground around Radok Lake and ice-dammed lake phenomena. Subglacial drainage of the lake escaped to the east exhuming the sediment-filled gorges. Holocene landscape modification has been relatively superficial. Overall, the landscape of the Amery Oasis evolved primarily under the influence of wet-based (probably polythermal) glaciers in Miocene and Pliocene times, whereas the Quaternary Period was characterised mainly by cold-based glaciers that had comparatively little impact on the landscape. © 2007, Elsevier Ltd.
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    Cold rocks, hot sands: in-situ cosmogenic applications in Australia at ANTARES
    (Elsevier, 2000-10) Fink, D; McKelvey, BC; Hannan, D; Newsome, D
    The ANTARES AMS facility at ANSTO is conducting a comprehensive program in the application of in-situ cosmogenic radionuclides based on strong university collaborations in the earth sciences. The program targets two major objectives: (1) to determine and improve the Quaternary glacial chronology of the Southern Hemisphere in support of global climate change studies; (2) to characterise the processes of surface weathering and landscape evolution in semi-arid regions of the Australian continent. An overview of the program is presented with preliminary results from the first phase of these studies. © 2000 Elsevier Science B.V.
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    Pleistocene deglaciation chronology of the Amery Oasis and Radok Lake, northern Prince Charles Mountains, Antarctica
    (Elsevier, 2006-03-15) Fink, D; McKelvey, BC; Hambrey, M. J; Fabel, D; Brown, R
    The East Antarctic Ice Sheet is the largest ice mass on Earth with a capacity to raise global sea level by up to 65 m. As the Lambert Glacier–Amery Ice Shelf drainage system is the largest to reach the coast of Antarctica, quantifying its evolution over the Quaternary is a vital component in developing an understanding of the Antarctic response to future climate change. Here we present a deglaciation chronology based on 10Be and 26Al in situ cosmogenic exposure ages of the northern Prince Charles Mountains, which flank the Lambert Glacier–Amery system, and that records the progressive emergence of McLeod Massif and Radok Lake basin from beneath the Mac.Robertson Land lobe of the East Antarctic Ice Sheet. The exposure ages monotonically decrease with both decreasing altitude and increasing proximity to the Amery Ice Shelf at the Antarctic coast. Exposure ages from the crests of McLeod Massif near the edge the Amery Ice Shelf and from Fisher Massif, 75 km further inland, each at ∼1200 m above sea level, are 2.2 ± 0.3 and 1.9 ± 0.2 Ma, respectively, suggesting their continuous exposure above the ice sheet at least since close to the Plio–Pleistocene boundary. An extensive plateau at ∼800 m altitude on McLeod Massif above Battye Glacier records the massif's increased emergence above the ice sheet surface at about between 880 and 930 ka ago indicating 400 m of ice volume reduction in the mid Pleistocene. Correcting these apparent ages for a reasonable choice in erosion rate would extend this event to ∼1.15 Ma — a period identified from Prydz Bay ODP core-1167 when sedimentation composition alters and rates decrease 10-fold. Exposure ages from boulder-mantled erosional surfaces above and beyond the northern end of Radok Lake at 220 m, range from 28 to 121 ka. Independent of choice of model interpretation to explain this age spread, the most recent major reoccupation of Radok Lake by Battye Glacier ice occurred during the last glacial cycle. Moraine ridges at the lower altitude of 70–125 m were deposited during the final withdrawal of Battye Glacier ice from the lake basin between 11 and 20 ka ago. This new chronology indicates that the highest Amery Oasis peaks have not been overridden by the Mac.Robertson Land lobe of the East Antarctic Ice Sheet for at least the past 2 Ma. Since this time we document 3 major periods of regional reduction in ice sheet volume at ∼1.1 Ma, during the last glacial cycle (120 to 30 ka) and through the Last Glacial Maximum (20 to 10 ka) that resulted in an overall 1000 m of ice lowering in the Battye Glacier–Radok Lake region. © 2005 Elsevier B.V.