OFR 151.pdf - CRC LEME

ange) than now. The overlying thick CID appears to have been ferruginised in the Neogene,
due to drawdown of the water table as climates became increasingly arid (Heim et al. 2006).
The Yallalie site preserves an unusually high resolution record of local climates, including
several aridity events, during the mid Pliocene warm period.
Central southern Australia
The tectonic and sedimentary histories of the eastern Eucla and Duntroon Basins have been
reviewed by geologists at Geoscience Australia (references in Bradshaw et al. 2003, Krassay
and Totterdell 2003, Blevin 2005). However, this has not resulted in drilling of offshore
prospects and almost all additional palaeobotanical evidence comes from onshore sections in
south-west South Australia. Examples are palaeobeach placer deposits (Clarke et al. 2003,
Hou et al. 2003a, Li et al. 2003) and Tertiary palaeochannel sequences on the Gawler Craton
(Hou et al. 2003b). A proposed correlation of Eocene sequences in the eastern Eucla Basin
with regional sea-level events (Hou et al. 2006) is weakened by the large number of apparent
anomalies in the palynostratigraphic dating (M.K. Macphail unpubl. comments). For
example, an interval in CRAE-2, dated as late Early Eocene Proteacidites asperopolus Zone,
includes species that first occur in the Gippsland Basin in the Early Oligocene (Cyatheacidites
annulatus) and late Early Miocene (Canthiumidites bellus, Symplocoipollenites austellus).
Whether these and other anomalies are due to downhole contamination, or reflect extended
species ranges – with radical palaeoclimatic implications – is unclear.
South-East Australia
The tectonic and sedimentary histories of the Bass, Gippsland and Otway Basins continue to
be reviewed by/for the earth resources industries (references in Bernecker and Partridge 2001,
Partridge 2002, Blevin 2003, Holdgate et al. 2003a, 2003b, 2006b, McGowran et al. 2004,
Paine 2005). The Ocean Drilling Program (ODP Leg 189) has significantly extended the
existing geological and biostratigraphic database for the offshore Sorell Basin in western
Tasmania, and the now deeply submerged South Tasman Rise and East Tasman Plateau
(references in Boreham et al. 2002, Macphail 2002, Exon et al. 2004a, 2004b, Hill and Exon
2004). Regolith and groundwater projects have provided new information on Early
Cretaceous and Late Tertiary environments in semi-arid to arid regions in eastern Australia,
e.g. Hill et al. (2003) and Macphail (2006b). In contrast, university and museum-based
research has tended to focus on lignitic deposits in Victoria and on the Southeastern
Highlands of New South Wales (references in Sharp 2004, Paine et al. 2004, Brown 2006,
Holdgate et al. 2006a). Piper et al. (2006) have reviewed Mesozoic-Cenozoic Local Faunas
found in Victoria. Four recent studies of particular significance are:
1. Revision of the Esso-BHP (spore-pollen) zonation for the Gippsland Basin and
correlation of the zone boundaries against the Gradstein and Ogg (2004) Time Scale by A.D.
Partridge (Monteil 2006). This project highlights difficulties in correlating 'local' zones
defined by presence/absence criteria against the International Time Scale although the
‘superzone’ boundaries in this schema almost certainly reflect abrupt changes in global
climate. For example the Forcipites longus/Lygistepollenites balmei Zone boundary, the
Lygistepollenites balmei/Malvacipollis diversus Zone boundary and Middle/Upper
Nothofagidites asperus Zone boundary correlate closely with the K/T Extinction Event at
about 65 Ma, the PETM at about 55 Ma and opening of the Tasmanian Gateway between
Australia and Antarctica at about 33 Ma, respectively (see Figure A). Studies of spore-pollen
successions in other southern margin basins indicate that many species have extended or, less
commonly, more restricted ranges compared to ranges recorded in the Gippsland Basin. For
this reason, it is premature to assume 'equivalent' zones in the Bass, Murray, Otway and Eucla
Basins have the same age limits as those inferred by A.D. Partridge (ibid) for the Gippsland
Basin zones.
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