An Oligocene palynoflora from the middle Shoalhaven catchment N.S.W. and the Tertiary evolution of flora and climate in the southeast Australian highlands
Abstract Well preserved spores and pollen from a number of middle Oligocene sedimentary formations in the middle Shoalhaven catchment N.S.W. are correlated with the Upper Nothofagidites asperus -Lower Proteacidites tuberculatus Zones of the Gippsland Basin, Victoria. Further confirmation of this correlation comes from three sources: (a) the relative abundances of pollen component groups reveal the Nothofagidites, Proteacidites and Myrtaceidites groups within the Shoalhaven assemblage to be typical of Late Eocene to middle Oligocene sequences; (b) comparisons with the ratios of Phyllocladidites mawsonii to gymnosperms, Araucariacites to gymnosperms, N. flemingii to other Nothofagidites and Myrtaceae to Nothofagidites in the Murray Basin indicate at least an Upper N. asperus age; and (c) strong geomorphic and stratigraphic evidence reported elsewhere shows that the spore and pollen bearing sediments were deposited in a basalt dammed lake between 29–32 Ma. The mid-Oligocene Shoalhaven assemblage fills a significant gap in the spore-pollen record of the southeast Australian highlands and, as a consequence, there is now a continuous record of development of flora and climate for this region for nearly the entire Tertiary. Average annual temperature and thermal seasonality appear to have been the two most significant climatic parameters to have varied throughout the southeastern highlands from the Palaeocene to the Miocene after which progressively drier conditions ensued.