OFR 151.pdf - CRC LEME

4. Northern New South Wales
Microfloras from the Northern Tablelands and adjacent slopes indicate that mean annual
rainfall was sub-optimal (humid) for Nothofagus except where orographic uplift of moist air
from the Tasman Sea maintained uniformly wet (perhumid) conditions. The upslope increase
in the relative abundance of Nothofagus (Lophozonia) spp. and other cool temperate rainforest
taxa indicates mean annual temperatures decreased from lower mesotherm on the western
slopes of the Northern Tablelands to upper microtherm in deeper valleys and on the summit
plateaux. Conditions on the coastal plain near Taree to the south are likely to have been
warmer (upper mesotherm) and more seasonal although summer rainfall was adequate to
support palms in a form of araucarian (dry) rainforest.
5. Southern New South Wales
Rainforest communities in sheltered areas at high elevations on the Southeastern Highlands
were dominated by Nothofagus (Brassospora) spp. throughout the Oligo-Miocene despite a
variable, but overall increasing sclerophyll component. Conditions here and at lower
elevations on the southwestern flanks of the highlands and the coastal plain to the east
remained wet to very wet (humid-perhumid) during the Oligocene-Early Miocene but became
too dry to support extensive Nothofagus (Brassospora) stands in the Middle Miocene.
Temperatures remained possibly within the lower mesotherm range but may have become less
equable over the same period. A late Early to early Late Miocene (Canthiumidites bellus
Zone) sequence at Little Bay near Sydney preserves a fossil leaf of a subtropical mangrove
(Brugiera) as well as marine dinoflagellates and abundant Nothofagus pollen. If correctly
interpreted (Pickett et al. 1997), the site provides compelling evidence that conditions on the
central coast of New South Wales were warm (upper mesotherm) and uniformly wet
(perhumid) during the Middle Miocene thermal maximum although it is recognised that this
interpretation also requires that some Brassospora and Lophozonia ecotypes were able to
tolerate atypically warm conditions.
6. Northern Tasmania
Macrofossils and microfossils provide a discontinuous record of the flora and vegetation
lining rivers flowing onto and across the Bassian Plain during the Oligo-Miocene. Only one
site (Fossil Bluff) possesses independent age control (Early Miocene). Cryptogam and
gymnosperm floras are diverse, but the Nothofagus-dominated angiosperm component is
distinctly impoverished, and taxa with warm temperate to subtropical NLRs are rare,
compared to correlative microfloras in mainland southeastern Australia. Common
macrofossils include Cunoniaceae and Lauraceae leaves. The combined data indicates
conditions were relatively cool (upper microtherm) and possibly uniformly wet (perhumid).
7. Central Plateau of Tasmania
Microfloras preserved in palaeochannel deposits on and below the northwestern margin of the
Central Plateau are unique in Tasmania in that their ages can be constrained by K/Ar dating of
associated basalt flows. The oldest Oligo-Miocene flora found so far is associated with till
deposited possibly during the earliest Oligocene Lemonthyme Glaciation. Despite the glacial
context, the only palaeobotanical evidence for cold (lower microtherm) conditions is the high
diversity of cryptogams and gymnosperms relative to angiosperms, and virtual absence of
microfossil taxa with warm temperate to subtropical NLRs. Palynological dominance and
foliar physiognomic analysis (Carpenter et al. 1994a) indicate mean annual temperatures at
Cethana on northwestern margin of the Plateau were within the upper microtherm range
(~12 0 C) during the Oligocene. Conversely temperatures at Monpeelyata on the eastern
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