Mapping of over 4000 block deposits and scree slopes in eastern Australia is used to determine the extent of past strong freeze-thaw activity. Freeze-thaw landforms are common in the high country as far north as 30˚S. There is a clear association between the locations of relict periglacial landforms and areas that receive more than 50 modern frost days. We infer about 10.5˚C cooling north of 35˚S in the Diving Range, about 9˚C in the Australian Alps and about 5˚C in Tasmania during the phases when the lowest block deposits were active. An unexpected observation is the importance of precipitation in the distribution of block deposits north of 35˚S. Here, the majority of block deposits have a southerly or westerly aspect, and lie in a narrow modern precipitation band of ca. 900-1050 mm. To the east, high-elevation areas appear to have weaker diurnal oscillations limiting freezethaw activity. To the west, block deposits are absent, probably due to insufficient moisture to drive freeze-thaw processes. We cannot define specific last glaciation precipitation but the maintenance of a strong east-west precipitation gradient during glacial times is consistent with the maintenance of onshore easterlies during cold periods.
Late Pleistocene and Early Holocene aeolian deposits in Tasmania are extensive in the present subhumid climate zone but also occur in areas receiving >1000 mm of rain annually. Thermoluminescence, optically stimulated luminescence, and radiocarbon ages indicate that most of the deposits formed during periods of cold climate. Some dunes are remnants of longitudinal desert dunes sourced from now-inundated continental shelves which were previously semi-arid. Others formed near source, often in the form of lunettes east of seasonally-dry lagoons in the previously semi-arid Midlands and southeast of Tasmania, or as accumulations close to floodplains of major rivers, or as sandsheets in exposed areas. Burning of vegetation by the Aboriginal population after 40 ka is likely to have influenced sediment supply. A key site for determining climate variability in southern Tasmania is Maynes Junction which records three periods of aeolian deposition (at ca. 90, 32 and 20 ka), interspersed with periods of hillslope instability. Whether wind speeds were higher than at present during the last glacial period is uncertain, but shells in the Mary Ann Bay sandsheet near Hobart and particle size analysis of the Ainslie dunes in northeast Tasmania suggest stronger winds during the last glacial period than at present.
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