Research Doctorate - Doctor of Philosophy (PhD) / The northern Central Highlands region of Tasmania extending north from Cradle Mountain to the Middlesex Plains shows evidence of three glacial stages, with the final stage consisting of several ice advance phases. From oldest to youngest these have been named the Middlesex Glaciation, the Sunshine Glaciation and the Cradle Glaciation. Cosmogenic exposure-age dating of boulders and ice-abraded bedrock, radiocarbon dating of post-glacial organic deposits, and relative dating techniques have resulted in assignment of the following ages for the events: Middlesex Glaciation, MIS 10; Sunshine Glaciation, MIS 6 and the Cradle Glaciation having MIS 3 and MIS 2 phases. The Cradle Glaciation correlates with the global Last Glaciation. Exposure-age dating of three of the Cradle Glaciation ice advance phases indicates that the Pencil Pine Phase predates 38.9±4.0 ka, the Dove Phase occurred ca. 29.2±1.4 ka, and the Cradle Valley Phase occurred between >19.7±1.1 – 17.6±1.0 ka. At least two undated retreat/readvance phases followed the Cradle Valley Phase. Deglaciation of the area was probably complete considerably before 11.2 ka. The recognised glacial events decreased in areal extent in each successive advance. Using the 0°C summer mean isotherm as the base for the altitude of the equilibrium line altitude, the regional snowline, regional snowline depression and temperature depression for each of the events were: Middlesex Glaciation, 942 m/1616 m/10.5°C; Sunshine Glaciation, 984 m/1574 m/10.23°C; Pencil Pine Phase, 1010 m/1548 m/10.06°C; Dove Phase, 1050 m/1508 m/9.8°C; and the Cradle Valley Phase, 1060 m/1498 m/9.74°C. The geomorphic evidence and dating of several phases of the Cradle Glaciation indicates a complex history of ice advances for Tasmania during the Last Glaciation.
| Identifer | oai:union.ndltd.org:ADTP/280667 |
| Date | January 2008 |
| Creators | Thrush, Michael |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
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