OFR 151.pdf - CRC LEME

4.3 Other Records
4.3.1 North-West Australia
The major regression at ~30 Ma (Early Oligocene) almost certainly reflects the development
of continental ice sheets in Antarctica. Subsequent eustatic events are overprinted with the
effects of tectonic downwarping along the western margin due to collision of the Australian
and Asian plates (Bradshaw et al. 1988, Apthorpe 1988).
4.3.2 North-East Australia
1. Coral Sea
Feary et al. (1991) estimate surface water temperatures off the north-east coast of Queensland
during the Oligo-Miocene time were between 9.5-13.0 0 C in the Early Oligocene, rising to
14.5-19.5 0 C and 17-20.5 0 C during the Early and Middle Miocene, respectively.
2. Riversleigh
Diverse vertebrate faunas preserved in freshwater limestones at Riversleigh are circumstantial
evidence that complex tropical rainforests lined some streams in northwestern Queensland
(Sige et al. 1982; Archer et al. 1989, Duncan et al. 1998, Hand 1998). This interpretation
may be overly simplistic, based on the rare occurrence of Allocasuarina/Casuarina and
Sapindaceae (Cupanieae) leaf impressions.
4.3.3 Central Australia
Faunal remains found at and near the surface in central Australia are difficult to date and/or
correlate with microfloras recovered from below the weathering front. In exceptional cases, a
combination of palaeomagnetic and palaeontological evidence allows local Land Mammal
biostratigraphies to be established, for example the Tirari-Sub-basin (Woodburne et al. 1993).
This schema potentially provides an independent record of evolving climates in the basin
during the Late Oligocene.
More generally however, the palaeontological and geological evidence of climates are
contradictory or reflect different local hydrologic regimes at different intervals within the Late
Oligocene-Miocene. For example, the remains of turtles, freshwater crocodiles, aquatic birds
and dolphins confirm that climates were sufficiently wet to support some permanent water
bodies in central Australia. Terrestrial vertebrate faunas are dominated by browsing
marsupials and include possums and a koala-like species that indicate sclerophyll trees (cf.
Woodburne 1967, Archer et al. 1994). Geological evidence indicates climates were strongly
seasonal with elevated (possible mesotherm) temperatures (Alley 1998).
4.4.4 South-East Australia
1. Northern Tablelands of New South Wales
Geological and palaeomagnetic analyses of bauxites developed on, and overlain by, mafic
volcanic flows indicate deep weathering over a significant period of time during mid
Oligocene to Early Miocene time on the New England Plateau (Acton and Kettles 1996).
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