KEY PERIODS IN THE EVOLUTION OF THE CENOZOIC VEGETATION AND FLORA IN WESTERN TASMANIA - THE LATE PLIOCENE

Fossil pollen and spores in organic-rich sediments in a side gully in the Linda Valley, western Tasmania, preserve one of the most detailed records of a Late Pliocene flora and vegetation available to date in A ustralia. This includes Araucariaceae, Beauprea Brongn. & Gris. and a number of sub-canopy broadleaf trees now confined to warm temperate-tr opical habitats. Changes in community dominance are interpreted in ter ms of alluvial events and point to the existence of altitudinally zone d plant communities in western Tasmania-Microstrobos J. Garden & L. Jo hnson heathland on the higher slopes and Nothofagus (Brassospora) Hill & Read-Lagarostrobos franklinii (J.D.Hook.) Quinn evergreen rainfores t with or without Dacrydium Sol. ex Lamb. emmend. de Laub. at lower el evations. The evidence demonstrates the survival of Nothofagus (Brasso spora) spp in western Tasmania at a time when other published data imp ly the taxon was virtually eliminated from the south-eastern mainland. It is proposed that increasingly seasonal climates drove an 'ecologic al wedge' into a former continuum of wet forest types along the east c oast of Australia, with Plio-Pleistocene glaciation being ultimately r esponsible for the demise, of what had become relict populations, of B rassospora spp. in western Tasmania.