OFR 151.pdf - CRC LEME

Inferred climate
The relatively good development of Sphagnum bog implies climates were cool-cold (possibly
upper microtherm) and probably wet (humid) with a strong seasonal bias. Since the
Carnarvon Basin was located at ‘mid’ (~60 0 S) rather than very high palaeolatitudes during
Campanian-Maastrichtian time, the preferred explanation is the cool conditions reflect cold
currents flowing along the western margin.
2. Pilbara region
A thin lignite recovered during exploration drilling (B. Balme pers. comm.) provides the only
known record of climates in the Pilbara region during the Late Campanian or Early
Maastrichtian (M.K. Macphail, unpubl. results). The age is based on Tricolporites cf. T. lilliei
in an assemblage lacking Stereisporites (Tripunctisporis) sp. An undescribed lycopod spore
previously recorded only in Late Cretaceous microfloras in central Australia is present in low
to frequent numbers.
Spores, in particular Sphagnum, Gleicheniaceae and the putative brackish to freshwater algal
cyst Amosopollis cruciformis dominate the microflora. Otherwise the only frequently
recorded taxa are Lagarostrobos and Proteaceae. The diversity of the latter is very low
relative to coastal assemblages. Rare taxa include Dacrydium (Lagarostrobos florinii)
Dacrycarpus-type (Trisaccites sp.) and Callitrichaceae. An unusual feature is the high
relative abundance of fully opaque black particles that appear to be carbonised wood. The
source vegetation is interpreted to be a spring or river-fed freshwater swamp surrounded by
Sphagnum bog and heath. Lagarostrobos was either a rare shrub or tree growing in the
swamp or on the banks of local streams.
Inferred climate
The assemblage broadly resembles microfloras found in central Australia during the
Maastrichtian. Local conditions were seasonally cool-cold (microtherm range) and prone to
droughts (and wildfires). Pollen data (Macphail et al. 1999) indicate peat mounds developed
under very wet (perhumid) climates at Port Davey in far southern Tasmania are analogous to
the Pilbara swamp in that these also dry out and are burnt during infrequent droughts.
6.2.5 Central southern Australia
1. Duntroon Basin
Late Campanian-Maastrichtian microfloras are preserved in nearshore to marginal marine
sediments intersected in Greenly-1 (Morgan and Hooker 1993d). Maastrichtian microfloras
are preserved in the Borda-1 well in the same basin (Morgan and Hooker 1993b) and also in
samples dredged from the seafloor in the Great Australian Bight (Alley and Clarke 1992).
Raw pollen counts indicate that a number of the taxa that were prominent in the
Nothofagidites senectus Zone microfloras had declined in relative abundance by the
Early/Late Campanian boundary. These include araucarians (Agathis/Wollemia), podocarps
(Microcachrys, Podosporites microsaccatus), Nothofagus, Callitrichaceae, ferns, fern allies
(Retitriletes) and peat moss (Sphagnum).
The only consistently common taxa found in the Late Campanian and Maastrichtian
microfloras in Greenly-1 are Proteaceae, possible pteridosperms (Alisporites) and ferns
(Cyatheaceae). Dacrydium (Lygistepollenites florinii), Lagarostrobos, Gambierina, ancestral
Nothofagus (Nothofagidites senectus), Gleicheniaceae and Osmundaceae and Sphagnum are
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