Topographic and microclimatic impacts on glaciation of the Denison Range, southwest Tasmania

Morphostratigraphic relationships between landforms and sediments, comparative boulder weathering status, and paired 10Be and 26Al exposure ages indicate the occurrence of at least three separate glaciations that are interpreted as dating from MIS 2, 6 and possibly 8. The Rhona Glacier remained at or close to its greatest LGM extent until ∼17.6 ka due to a very favourable micro-climate that resulted from local topography. That these factors were sufficient to over-power relatively subtle zonal temperature shifts that caused significant changes in more exposed Tasmanian glaciers implies a need for caution in correlating between glacier systems in markedly different topographic settings when environmental conditions are only marginally supportive of glaciation. No evidence was detected for any greater ice extent during MIS 3 or MIS 4 than during MIS 2, but much more extensive glaciations occurred during earlier glacial climatic cycles. Reduced local precipitation in parallel with increasing aridity of the Australian continent may account for the progressively diminishing maximum extent of glaciers during the latter part of the Pleistocene, and it would have emphasized the importance of local topography and microclimate for the glaciers of southwest Tasmania.