Extent of the Late Cainozoic periglacial domain in southwest Tasmania, Australia

Abstract

Examination of colluvium mantles and associated alluvial fans along a low altitude transect extending 65 km through western and south-western Tasmania indicates there to have heen negligible development of these features inside the ice limits attained during the most recent glacier advance, but that progressively thicker accumulations occur inside successively older glacial limits. This juxtaposition of moraines and slope mantles suggests that most slope instability occurred during episodes of cold climate in response to periglacial processes. The origin of some of the oldest glacigenic sediment has been masked almost entirely by this periglacial reworking. Angular rock rubble is abundant in extraglacial slope deposits and attests to vigorous mechanical weathering of bedrock that is not occurring under the present climate. Similar rock rubble in the entrances to some extraglacial karst caves is not explicable by fire-induced bedrock spalling, gypsum wedging, salt weathering or hydration shattering, and it is interpreted as the product of periglacial frost action. Two such cave rubble accumulations dated to MIS 2 indicate that frost action processes were effective to as low as 40 m altitude.