Tundra environments in the Neogene Sirius Group, Antarctica: evidence from the geological record and coupled atmosphere–vegetation models

The Neogene Meyer Desert Formation, Sirius Group, at Oliver Bluffs in the Transantarctic Mountains, contains a sequence of glacial deposits formed under a wet-based glacial regime. Within this sequence fluvial deposits have yielded fossil plants that, along with evidence from fossil insects, invertebrates and palaeosols, indicate the existence of tundra conditions at 85°S during the Neogene. Mean annual temperatures of c. –12 °C are estimated, with short summer seasons with temperatures up to +5 °C. The current published date for this formation is Pliocene, although this is hotly debated. Reconstructions produced by the TRIFFID and BIOME 4 vegetation models, utilizing a Pliocene climatology derived from the HadAM3 General Circulation Model (running with prescribed boundary conditions from the US Geological Survey PRISM2 dataset), also predict tundra-type vegetation in Antarctica. The consistency of the model outputs with geological evidence demonstrates that a Pliocene age for the Meyer Desert Formation is consistent with proxy environmental reconstructions and numerical model reconstructions for the mid-Pliocene. If so, the East Antarctic Ice Sheet has behaved in a dynamic manner in the recent geological past.