OFR 151.pdf - CRC LEME

PREAMBLE TO 2007 EDITION
Since this monograph was submitted to CRC LEME in September 2000, Climatic Change has
achieved a media prominence in Australia rarely if ever equalled in the past. Compelling
reasons are the general acceptance of global warming as a key threat to the global community
and, more locally, the impact of socially ‘catastrophic’ events such as Cyclone Larry (northeast)
and prolonged drought (south-east), even if the nexus to global warming is unproven.
Not surprisingly, research into the predicted social and economic impact of global warming
has been accompanied by renewed interest in apparently analogous warm intervals in the
more recent geologic past - in particular the mid Pliocene ‘warm period’ some 2.5 million
years ago and, more recently, the Paleocene-Eocene Thermal Maximum (PETM) about 55
million years ago. A second major stimulus has been the ‘resources boom’ generated by the
rapid expansion of the Chinese and Indian economies.
Time constraints do not allow the text (or conclusions) of the 2000 monograph to be revised.
As a compromise, this Preamble provides a selection of papers published since 2000, which in
the author’s opinion have the potential to improve our understanding of Cretaceous and
Tertiary palaeoclimates in Australia as well as their correlation to global events (Table A).
These studies range from the revision of the International Geological Timescale by Gradstein
and Ogg (2004) and the biostratigraphies used to date and correlate Mesozoic-Cenozoic
sequences in the marginal basins around the continent, e.g. Helby et al. (2004), Partridge
(1999) and Monteil (2006), to 'spot samples’ that provide the first detailed information on the
role of Tertiary climatic change in the genesis of valuable placer deposits, e.g. de Broekert
(2003), Hou et al. (2003a), Macphail and Stone (2004) and Paine (2005).
As in 2000, much palaeobotanical evidence continues to be generated as a by-product of
hydrocarbon, mineral and groundwater exploration and the data remain ‘concealed’ in
confidential (closed file) industry reports. Equally limiting as regards the reconstruction of
terrestrial environments is the strong petroleum industries focus on marine microfossils,
especially in western and northern Australia. One predictable consequence is that Tertiary
spore-pollen sequences in inland northern Australia are, and will continue to be, difficult to
date to a Geological Stage let alone to shorter intervals of geological time unless the host
deposit is amenable to isotopic dating (discussion in Macphail and Stone 2004). The same is
true of Tertiary non-marine sequences in Queensland and Plio-Pleistocene sequences in
southern Australia (Dettmann and Clifford 2003, Macphail 2004a, 2006a)
North-West Australia
Micropalaeontological research, e.g. Collins et al. (2006), can help refine palaeotemperature
trends for the northwestern margin, but virtually no additional palaeobotanical data have been
formally published since 2000. Unpublished industry data indicate that Late Cretaceous
floras on the North West Shelf include a significant number of angiosperm and cryptogam
taxa that have not been recorded in correlative deposits in southern Australia (R. Helby and
M.K. Macphail pers. observations). These, and independently dated microfloras preserved in
Tertiary marine sequences, potentially provide a way to synthesize a pollen and spore-based
palynostratigraphy for continental northwestern Australia.
North-East Australia
Regolith studies and marine sequences are a potential source of palaeoclimatic information,
e.g. Forsyth and Nott (2003) and Conesa et al. (2005), but palaeobotanical reconstructions of
Mesozoic-Tertiary climates continue to be constrained by limited access to proprietary data
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