Coastal erosion reveals a potentially unqiue Oligocene and possible periglacial sequence at present-day sea level in Port Davey, remote South-West Tasmania

• Main Authors: Macphail, M, Sharples, C, Bowman, D, Wood, S, Haberle, S
• Format: Article in Journal/Newspaper
• Language: English
• Published: Royal Society of Tasmania 2014
• Subjects: Earth Sciences; Physical Geography and Environmental Geoscience; Physical Geography and Environmental Geoscience not elsewhere classified; Davey; East Antarctica; Antarc*; Antarctica
• Online Access: http://rst.org.au/publications/papers-and-proceedings/; http://ecite.utas.edu.au/97479

Cut-back of a sea-cliff at Hannant Inlet in remote South-West Tasmania has exposed Oligocene clays buried under Late Pleistocene colluviumfrom which abundant wood fragments protrude. The two units are separated by a transitional interval defined by mixed Oligocene andPleistocene microfloras. Microfloras preserved in situ in the clay provide a link between floras in Tasmania and other Southern Hemispherelandmasses following onset of major glaciation in East Antarctica during the Eocene-Oligocene transition (c. 34 Ma). The Late Pleistocenecolluvium preserves abundant fossil pollen of the shrub conifer genus Pherosphaera (al. Microstrobos ). Assuming the parent plants had thesame upper subalpine-alpine ecology as living Pherosphaera hookeriana , the microflora provides evidence for cold, wet conditions in thePort Davey lowlands during a low sea-level stand. The same data highlight the failure of Pherosphaera to regain its Pleistocene distributionduring the Postglacial period. Our data are inconclusive whether Late Pleistocene conditions in Hannant Inlet were periglacial, i.e., theOligocene sediments were turbated by freeze-thaw processes, or have been reworked by fluvial processes into the Pleistocene colluvium.Nevertheless, the inferred cold-climate is consistent with the former hypothesis. The sequence is sealed under cross-bedded coarse quartzitegravels of presumed Last Glacial Stage age.