Cool-temperate riparian floras in the Early Cretaceous rift valley of Victoria, Australia

To better understand the riparian floras associated with Early Cretaceous vertebrate localities in Victoria, Australia, we studied 291 palynological samples from 48 sites in the Otway and Gippsland basins. Podocarpaceae represent the major component of the open canopy forests of the Barremian–Aptian, whereas Araucariaceae are increasingly prolific in the Albian. Ferns, particularly Cyatheaceae, represent large components of the understorey flora through the Barremian–Aptian, whereas Schizaeaceae and Gleicheniaceae ferns and angiosperms are more common in the Albian. Notably, all recorded palynofloras imply a high-rainfall regime, despite the high palaeolatitude (70–85°S), through the Barremian, Aptian and Albian in Victoria. The increasingly warm conditions globally, from the Barremian to Albian, likely drove the prominent floral turnover observed, including numerous extinctions, and the rapid diversification of angiosperms. Increased competition may also have contributed to the decline in lycophyte richness and abundance, with angiosperms outcompeting lycophytes in rapidly colonizing newly available braidplain sites after flooding events. These inferences, also consistent with geochemical and palaeobotanical proxies, suggest that cool-temperate climates supported dynamic and forested floodplain environments in the Early Cretaceous rift valley of Victoria. <i>Vera A. Korasidis* [[e-mail]], School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Parkville, VIC 3010, Australia; Barbara E. Wagstaff [[e-mail]], School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Parkville, VIC 3010, Australia.</i>