Geomorphology and Geomorphologists
Tasmania is distinguished from mainland Australia by its insularity, cool climate and former extensive glaciation. Separated from Antarctica during the last 100 million years, erosion has produced numerous extensive landscape surfaces of low relief that occur at various altitudes throughout the state. These surfaces have been described by Jack Davies. The rift with Antarctica produced a steep western margin that has allowed the rivers of western Tasmania to carve deeply incised valleys and gorges through the mountain ranges. Episodic volcanic eruptions mostly between 64 and 8.5 million years ago resulted in basalt lava flows and ash showers in northern and central Tasmania, with occasional flows in the south-east valleys. Lin Sutherland and John Everard have studied the volcanic rocks.
Moraines providing evidence for former glaciation were found in the Cuvier Valley by Charles Gould in 1860. During the late nineteenth century, geological surveyors made miscellaneous records of ice action before the Hobart lawyer Arndell Lewis proposed a three-fold model of glaciation in 1945. Lewis suggested an initial stage of extensive ice sheet glaciation for much of western Tasmania, followed by a period when valley glaciers were dominant and another when cirque glaciers were characteristic. The advent of aerial photographs permitted Edward Derbyshire, Maxwell Banks and others to assess the extent of former ice cover. They found it to be much less than advocated by Lewis. The first radiocarbon date obtained in 1956 suggested the glacial deposits were all less than 26,480 +/-800 years old and thus belonged only to the last major period of glaciation. However, later investigations by Sep Paterson in the Mersey and Forth valleys in 1965 provided clear evidence for two periods of glaciation.
In 1972 Eric Colhoun formed a school of Quaternary geomorphology in the Geography Department of the University of Tasmania at a time when extensive investigation and construction work was being undertaken by the HEC in western Tasmania. Mapping of glacial landforms and deposits was undertaken by Paul Augustinus, Adrian Bowden, Sean Fitzsimons, Kevin Kiernan and others, and extended to northern Tasmania by David Hannan. The deposits have been dated using weathering, soil development, radiocarbon, palaeomagnetic, uranium series and cosmogenic isotope methods. The results have provided evidence for many periods of glaciation during the last million years. Through the work of this group the story of Tasmanian glaciation has become known internationally.
The modern beaches of Tasmania have been studied by Jack Davies and raised beaches of Pleistocene age by Adrian Bowden and Eric Colhoun. The most extensive raised beaches have been dated to the last interglacial period by Colin Murray-Wallace and Albert Goede using the amino-acid racemisation and electron spin resonance methods. Nel Caine has studied the effects of frost action on the alpine landscapes of north-eastern Tasmania. Adrian Bowden has examined the terrestrial dunes of north-east Tasmania and Paul Augustinus has dated some to the last glacial period using the optically stimulated luminescence method. Wayne Sigleo found that many of the dunes of the Midlands and south-east were Aboriginal occupation sites.
A wealth of information has been obtained from caves. Albert Goede examined changes of climate using oxygen isotope data from stalagmites, and with Peter Murray found abundant fossils of marsupials, including extinct species of megafauna. They also found human artefacts of glacial age at several localities, while Kevin Kiernan found the most important Aboriginal occupation site of Kutikina Cave in the Franklin Valley. Evidence from this site that people occupied south-west Tasmania during the peak of the last glaciation has transformed our understanding of human history in Tasmania and the south-west Pacific.
Further reading: N Caine, The mountains of northeastern Tasmania, Rotterdam, 1983; E Colhoun, 'Quaternary', Geology and mineral resources of Tasmania, Geological Society of Australian Special Publication 15, 1989; E Colhoun & S Fitzsimons, 'Late Cainozoic glaciation in western Tasmania, Australia', Quaternary Science Reviews 9, 1990; K Kiernan, R Jones & D Ranson, 'New evidence from Fraser Cave for glacial age man in southwest Tasmania', Nature 301, 1983.