The distribution and climatic implications of periglacial landforms in eastern Australia

Abstract

ABSTRACT 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 freeze–thaw 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.