Pleistocene palaeoecology and environmental change on the Darling Downs, Southeastern Queensland, Australia

A diverse Pleistocene fossil assemblage was recovered from a site (QML1396) exposed in the southern banks of Kings Creek, Darling Downs, southeastern Queensland. The site includes both high-energy lateral channel deposits and low-energy vertical accretion deposits. The basal fossil-bearing unit is laterally extensive, fines upward and its geometry and sedimentary structures suggest deposition within a main channel. The coarse channel fill passes upward into overbank levee deposits made up of lenticular sandy-shelly strata alternating with muds. Several taphonomic biases relating to preservation of different faunal groups and skeletal elements was discerned. Biases may be related to fluvial sorting of the assemblage, but causes for differences between the preservation and accumulation of mammal versus non-mammal terrestrial vertebrates remain unclear. In general, the vertebrate material was accumulated and transported into the deposit from the surrounding proximal floodplain. The assemblage is composed of 44 species including molluscs, teleosts, anurans, chelids, squamates, and small and large-sized mammals. Palaeoenvironmental analysis suggests that a mosaic of habitats, including vine thickets, scrublands, open sclerophyllous woodlands interspersed with sparse grassy understories, and open grasslands, were present on the floodplain during the late Pleistocene. From sedimentological and ecological data, it is evident that increasing aridity during the late Pleistocene led to woodland and vine thicket habitat contraction, and grassland expansion on the floodplain. At present, there is no evidence to support the suggestion that the retraction of late Pleistocene Darling Downs habitats was due to anthropogenic factors.