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

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Macphail, MK and Sharples, C and Bowman, DMJS and Wood, S and Haberle, S (2014) Coastal erosion reveals a potentially unique 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

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Abstract

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.

Item Type: Article
Keywords: Cenozoic palynostratigraphy, Tasmania, Antarctica, South America, Oligocene, Pleistocene, Lophosoria, Embothrium, Pherosphaera, trans-oceanic migration, The Royal Society of Tasmania, natural history, science, papers & proceedings, Australia
Journal or Publication Title: Papers and Proceedings of the Royal Society of Tasmania
Page Range: pp. 43-59
ISSN: 0080-4703
Copyright Information:

Copyright The Royal Society of Tasmania

Collections: Royal Society Collection > Papers & Proceedings of the Royal Society of Tasmania
Date Deposited: 18 Nov 2016 02:01
Last Modified: 05 Jan 2017 16:00
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