Neogene environments in Australia, 1: Re-evaluation of microfloras associated with important Early Pliocene marsupial remains at Grange Burn, southwest Victoria

Abstract

One of the few independently dated (4.46 Ma) sites in Australia where an important assemblage of marsupial fossils is preserved in association with plant remains is at Grange Burn near Hamilton in southwest Victoria. The two lines of evidence concur that the Early Pliocene vegetation was a mosaic of araucarian (dry) rainforest and open-canopied sclerophyll formations, developed under mildly seasonal, humid climates. Species typical of wetter rainforest types growing in the region during the Oligocene to Middle Miocene had become rare or extinct at Grange Burn by 4.46 Ma although Nothofagus (Brassospora) may have survived on adjacent uplands such as the Grampian and Otway Ranges. Grasses were part of the regional flora, but there is no evidence for grasslands per se. The diversity of subcanopy species with mesophytic affinities appears to increase upsection, consistent with minor warming or increasing effective precipitation between 5.2 and 4.46 Ma.