Coastal erosion reveals a potentially unqiue Oligocene and possible periglacial sequence at present-day sea level in Port Davey, remote South-West Tasmania
Macphail, M and Sharples, C and Bowman, D and Wood, S and Haberle, S, Coastal erosion reveals a potentially unqiue Oligocene and possible periglacial sequence at present-day sea level in Port Davey, remote South-West Tasmania, Papers and Proceedings of the Royal Society of Tasmania, 148 pp. 43-59. ISSN 0080-4703 (2014) [Refereed Article]
Cut-back of a sea-cliff at Hannant Inlet in remote South-West Tasmania has exposed Oligocene clays buried under Late Pleistocene "colluvium"
from which abundant wood fragments protrude. The two units are separated by a transitional interval defined by mixed Oligocene and
Pleistocene microfloras. Microfloras preserved in situ in the clay provide a link between floras in Tasmania and other Southern Hemisphere
landmasses following onset of major glaciation in East Antarctica during the Eocene-Oligocene transition (c. 34 Ma). The Late Pleistocene
"colluvium" preserves abundant fossil pollen of the shrub conifer genus Pherosphaera (al. Microstrobos). Assuming the parent plants had the
same upper subalpine-alpine ecology as living Pherosphaera hookeriana, the microflora provides evidence for cold, wet conditions in the
Port Davey lowlands during a low sea-level stand. The same data highlight the failure of Pherosphaera to regain its Pleistocene distribution
during the Postglacial period. Our data are inconclusive whether Late Pleistocene conditions in Hannant Inlet were periglacial, i.e., the
Oligocene 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 quartzite
gravels of presumed Last Glacial Stage age.