Glaciation of Frenchmans Cap-National Park

Abstract

Mapping of glacial landforms of the Frenchmans Cap National Park shows that an independent system of cirque and valley glaciers accumulated upon and caused considerable modification of this area during the last Pleistocene glaciation. Clearest evidence of the sequence of advance and retreat is seen in the Vera Valley where, during the maximum phase, the ice reached the Vera Creek gorge and overspilled a series of diffluence passes further upstream. The history of subsequent retreat can be traced with reference to the post-maximum moraines. Some detailed work on the morphology of the lake basins makes possible a classification of lakes which shows clearly the nature of the glaciation and the influence of lithology. Careful consideration of the aspect, morphology, and elevation of the cirques in which many of these lakes occur provides interesting comment upon the factors governing accumulation and ablation in the maritime mountain environment of glacial and lateglacial times. Radiocarbon assay of leaf fragments in rock-flour below peat in a bedrock depression on the lip of one of the high discrete cirques gives a minimum age of 8720 ±220 years B.P. for the final deglaciation of the Frenchmans Cap area in particular and the western Tasmanian mountains in generaL The present study is discussed with reference to some of the chronological problems of the last glruciation. The possibility of a sequence of glacials and interglacials is recognized. As the Pleistocene climate changes of the southern hemisphere form the broad context of the present study attention is drawn to analogies in the New Zealand sequence

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