The glacial history of Tasmania from mid-pleistocene to the last glacial maximum – new challenges and new ideas for hemispheric glacial climate correlations.
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Date
2010-02-01
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Publisher
Centro De Estudios Cientificos
Abstract
The study of the Quaternary glacial history of Tasmania using various relative dating methods (weathering, geomagnetic stratigraphy, U-Th series and radiocarbon) has resulted in the identification of a complex system of multiple glaciations and isolated ice caps active over the past one million years. The application of cosmogenic nuclides 10Be and 26Al for the exposure age dating of glacial landforms, such as terminal and lateral moraines, recessional moraine sequences, erratics and exposed polished bedrock throughout the Western and Central regions of Tasmania during the midlate Pleistocene up to the LGM has forced a re-examination of the existing glacial chronology. This new chronology indicates a very different mode of glacial climate change in the high Southern Hemisphere latitudes – in both timing and extent- compared to that in the Northern Hemisphere. Moraines in the Pieman River valley and Tyndall Ranges of the west coast region, previously attributed to marine isotope-18O Stage (MIS) 6 and 8 are now considered more likely to have been deposited during MIS 10-12. Glacial advances from MIS 2 to 6 appear to have been restricted and are much less extensive than suggested previously. 10Be and 26Al exposure age dating of LGM moraines from a range of sites in western Tasmania indicates that the sequence is more complex than hitherto considered. Significantly, there is no evidence for a Younger Dryas glacier re-advance in western Tasmania which supports palynological evidence for no significant regional cooling at this time. Our general conclusions based on over 150 exposure ages from multiple valley sites containing cirque and retreat phase moraines are: (1) MIS-8 (~240 ka) to MIS-16 (~660) glacial cycles are extensive in the lowlying plains of the west coast ranges and northern outlet valleys for the Central Plateau. 2) Stadials within the Last Glacial Cycle, i.e. <120 ka (MIS-2 to 6), are weakly represented throughout all regions studied. 3) The onset of the local LGM period is variable and appears to range from 24-28 ka and deglaciation appears to commence at ~19-22 ka. 4) Valley glacial systems were ice-free by at most 14-16 ka and no YD-chron readvance is apparent.
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Keywords
Tasmania, Quaternary period, Ice caps, Isotope dating, Climatic change, Moraines
Citation
Fink, D., & Augustinus, P. (2010). The glacial history of Tasmania from mid-pleistocene to the last glacial maximum – new challenges and new ideas for hemispheric glacial climate correlations. Poster presented to the International Glaciological Conference (VICC 2010) - "Ice and Climate Change: A View from the South", 1st - 3rd February 2010. Valdivia, Chile: Centro de Estudios Científicos (CECS), (pp. 11).