Evidence of vegetation change during the early Pleistocene is provided by a high resolution pollen record from the Stony Creek Basin, a palaeo-maar near Daylesford, in the western uplands of Victoria. A maximum age of 1.74 Ma is provided by detrital zircons intercalated within lake sediments. The 2.7 m long sequence shows changing proportions of tree taxa indicative of a continuously forested environment. The early part of the sequence is dominated by Eucalyptus forest including some mesotherm (warm temperate-subtropical) angiosperm rainforest taxa. Subsequently, regional drying is indicated by loss of rainforest taxa, increases in aquatic taxa reflecting lower water levels, and expansion of Callitris. Later, apparently in response to regional cooling, forests of Casuarina expanded at the expense of Eucalyptus and Callitris. Finally ferns, Podocarpaceae, and other rainforest angiosperms became important, indicating the expansion of microtherm (cool temperate) rainforest in response to increased moisture. The low representation of herbaceous taxa including the Pleistocene indicator taxon Cassinia arcuata type ( = Tubulifloridites pleistocenicus Martin) suggests that open-canopied vegetation was not so extensive on the southeastern Australian mainland by 1.74 Ma as has previously been proposed. Both mesotherm and microtherm rainforests were still present in western Victoria, at least in upland situations, around 1.74 Ma. Consistent trace quantities of Nothofagus (subgenus Brassospora) imply the regional persistence of this taxon in southeastern Australia during the early Pleistocene.

The Stony Creek Basin record suggests that the transition from ‘Tertiary’ to ‘Quaternary’ vegetation was more heterogenous, and longer lasting, than has previously been documented. The co-existence of diverse sclerophyll and rainforest taxa in the relatively cool and dry west Victorian uplands, now lacking rainforest and dominated by dry sclerophyll forests, may be best explained by lower climatic variability during the early Quaternary than during the late Quaternary. This suggests that modern ranges of rainforest taxa are truncated with regards to minimum rainfall requirements, and for some taxa, minimum temperature requirements. Palaeoclimate estimates based on modern taxon ranges may therefore be misleading.