Palaeovegetation and environment at Cethana, Tasmania

The Oligocene (ca 35 Ma) Cethana fossil deposit in northern Tasmania is investigated, with the aim of reconstructing the vegetation and environment. Aspects of the geology, palynology and particularly the macrofossil component of the flora are considered. The flora is discussed in the context of the development of the Australasian vegetation. The sediments are believed to have been deposited in a lake situated in a topographically diverse region. In particular, perturbations to the facies by siliceous debris suggests the lake was proximal to a steep slope. The macrofossils are represented by impressions or carbonised compressions from which fragments of cuticle can be recovered. Scanning electron microscopy is an important technique used to examine and compare fossil and extant cuticles. Pteridophyte macrofossils identified include specimens of Hymenophyllaceae, Lygodium (Schizaeaceae) and Sticherus and Gleichenia (Gleicheniaceae). Gymnosperm macrofossils identified are the extinct cycad Pterostoma, Macrozamia (Zamiaceae), Acmopyle, Dacrycamus, Dacrydium, Phyllocladus, Lagarostrobos and Podocarpus (Podocatpaceae), Agathis and Araucaria (Araucariaceae) and Libocedrus and Papuacedrus (Cupressaceae). Angiosperm macrofossils have affinity to three of the four subgenera of Nothofagus (Fagaceae), Gymnostoma (Casuarinaceae), Lomatia, Banksia/Dryandra and other genera (Proteaceae), Callicoma, Vesselowskya and Weinmannia/Cunonia (Cunoniaceae), Brachychiton (Sterculiaceae), Elaeocarpaceae, Lauraceae and Myrtaceae. Detailed taxonomic descriptions are provided for some of the macrofossils.