OFR 151.pdf - CRC LEME

5.2.7 Tasmania
Late Neogene sediments are extremely rare in Tasmania due to glacial erosion and periglacial
activity during the Pleistocene. The one exception is a thin unit of carbonaceous silts and
sands preserved below glacial outwash at ~300 m elevation in the Linda Valley, near
Queenstown (Macphail et al. 1995). The associated microfloras are dominated by one or
more of Dacrydium, Lagarostrobos, Microstrobos, Nothofagus (Brassospora) spp., and
Restionaceae. Nothofagidites asperus, the fossil equivalent of pollen produced by the
dominant temperate rainforest tree in western Tasmania (Nothofagus cunninghamii), is
uncommon relative to fossil types representing N. (Brassospora) spp. Rare taxa also include
genera that are extinct in Tasmania but survive in mainland Australia or landmasses to the
north, e.g. Austromyrtus-type, Beauprea, Cassinia arcuata-type (Tubulifloridites
pleistocenicus) and Eucalyptus spathulata-type (Myrtaceidites lipsis). Cyclic changes in
pollen dominance, which appear to represent depositional rather than climatic events, imply
the vegetation was altitudinally zoned, with Microstrobos-Restionaceae wet heath occupying
the upper slopes and Nothofagus-Lagarostrobos-Dacrydium rainforest the lower (possibly
swampy) ground.
Inferred climate
Local climates were seasonally cold (lower microtherm) and uniformly wet to very wet
(perhumid).
5.3 Other Records
1. North-West Australia
An impoverished Pliocene fauna is preserved at Quanbun in the Kimberley region (Flannery
1984). Conditions were sufficiently wet to support crocodiles.
2. North-East Australia
A Pliocene vertebrate fauna is preserved at Bluff Downs in northern Queensland (Archer and
Wade 1968, Archer et al. 1994). The high percentage of extant mammalian genera indicates
that essentially modern conditions were in existence at the time of deposition. Wroe and
Mackness (2000) suggest that the presence of dasyurids in the mid Pliocene Chinchilla Fauna
imply conditions in south-eastern Queensland were relatively dry (subhumid) and strongly
seasonal.
3. Central Australia
Late Miocene vertebrate remains in the Alcoota Local Fauna (Waite Basin, Alice Springs
district) are dominated by browsing herbivores and lacks arboreal and grazing mammals
(Woodburne 1967). The vegetation is likely to have been open sclerophyll woodland or
shrubland which lacked a ground cover of abrasive grasses such as Spinifex and Triodia.
Lacustrine gastropods and crocodile gastroliths are evidence that climates in this now arid
region were sufficiently wet (possibly subhumid) to maintain freshwater ponds.
4. South-East Australia
Lacustrine sediments infilling Palaeolake Bunyan, in the Murrumbidgee River Valley
between Bredbo and Cooma on the Southeastern Highlands, are capped by a diatomite unit
which is provisionally dated as Late Miocene (Taylor et al. 1990). Cyclic bedding within the
diatomite is interpreted as evidence for (1) strong seasonal variation in air water temperatures
and photoperiod and (2) on a longer time scale, climatic instability with a periodicity less than
or equal to 8000 years.
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