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

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.

Macroevolutionary dynamics in the early diversification of Asteraceae

“…Tubulifloridites lilliei type A pollen fossils are of dubious value in calibrating phylogenetic trees in Asterales and were not used in this study. Tubulifloridites lilliei circumscribes several fossilized pollen morphotypes that have been associated to angiosperms, possibly Asteraceae if exine characteristics are overlooked (Dettmann and Jarzen, 1988) or families outside of Asterales (Ranunculaceae as Tricolporites lilliei, Dettmann 1994; Euphorbiaceae as Tensucolpites lilliei, Macphail et al, 2014). When considering Tubulifloridites lilliei, Zavada and de Villiers (2000) and Zavada and Lowrey (2010) find these tricolporate, psilate to microechinate pollen grains with lalongate endoapertures could represent the ancestral pollen type of Asteraceae but are difficult to separate from those of other families.…”

Development of 15 nuclear EST microsatellite markers for the paleoendemic conifer Pherosphaera hookeriana (Podocarpaceae)

“…Pollen evidence suggests that the species was an important component of the Last Glacial vegetation, having a wider distribution than present and occurring at lower elevations down to near sea level (Colhoun, ). At the onset of postglacial warming, the species retreated to higher altitudes or, in some cases, became locally extinct (Macphail et al., ). The species is classified as Vulnerable under the Tasmanian Government Threatened Species Protection Act 1995 due to its limited range and its high sensitivity to fire and drought, which have intensified in recent decades (Threatened Species Section, ).…”