OFR 151.pdf - CRC LEME

3.2.2 North-East Australia
1. Carpentaria Basin
Microfloras recovered from the Late Albian possibly to Cenomanian marine Allaru Mudstone
(BMR Dobbyn-1) in northwestern Queensland (Playford et al. 1975) are dominated by
gymnosperms, in particular araucarians (including Araucaria), brachyphyll araucarians
(Hoegisporis) and podocarps (Microcachrys, Podocarpus-Prumnopitys), and ferns (chiefly
Gleicheniaceae). Angiosperms are relatively rare but include Chloranthaceae
(Clavatipollenites), Liliaceae (Liliacidites) and a diverse group of small tricolpate and
tricolporate types.
Inferred climate
The source vegetation appears to have been araucarian-podocarp Austral Conifer Forest
growing on uplands on the western margin of the basin. Climates were humid and probably
warm (mesotherm range) but neither the palynofloras nor the associated foraminifera include
taxa whose NLRs imply subtropical-tropical environments.
3.2.3 Central Australia
1. Eromanga Basin
Dettmann et al. (1992) note that the conifer/cycad woodlands and fern/angiosperm heath
surrounding freshwater lakes and swamps in the Eromanga Basin during the Albian survived
into Cenomanian time. Data from the Winton Formation (Martin 1998b) provide evidence
that some ferns (Blechnaceae, Cyatheaceae, Gleicheniaceae) remained abundant, but indicate
that araucarians may have been locally extinct whilst Anemia (Plicatella, Ruffordiaspora)
pteridosperms, podocarps (Microcachrys) and angiospermids had become uncommon to rare.
Inferred climate
The continuing high relative abundance of ferns such as Gleicheniaceae is likely to reflect an
expansion of fern heath into the depression formerly occupied by the Eromanga-Surat
Seaway. Other taxa imply that climates remained locally, or seasonally, humid. Nonetheless,
effectively drier climates and/or a rise in mean minimum temperatures (possibly to an upper
microtherm) best explain the contraction in range and/or relative abundance of both canopy
trees and ground ferns. The latter inference is supported by the absence of dropstones and
other evidence for ice (Frakes 1999).
3.2.4 South-West Australia
1. Carnarvon Basin
Ingram and Morgan (1988) note that spores and pollen becomes slightly more common in
marine sediments (5-10%) during the Late Cenomanian but the only named taxa are
dinoflagellates. Little can be interpreted from these data.
2. Perth and Eucla Basins
Balme (1964) lists brachyphyll araucarians (Balmeiopsis, Hoegisporis) and Gleicheniaceae as
one of the more commonly occurring types in Cenomanian microfloras from the Perth and
Eucla Basins (palaeolatitude ~60-65 0 S).
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