OFR 151.pdf - CRC LEME

troughs in the Bass and Gippsland Basins. Onset of seafloor spreading in the Tasman Sea at
about 80 Ma led to the separation of New Zealand and a number of other continental
fragments from the palaeo-eastern margin of Australia. Associated events included igneous
activity in southeastern Queensland and eastern New South Wales. An extensive river system
drained into the Indian Ocean via the Officer and Canning Basins. Elsewhere deep
weathering continued over much the continent.
6.6.2 Palaeobotany
Forests and woodlands remained dominated by gymnosperms although the diversity and
relative abundance of angiosperms continued to increase. Whether these angiosperms were
shrubs or trees is uncertain. In palynostratigraphic terms, the most prominent clade to migrate
into Australia at this time (at the Santonian/Campanian boundary) were ancestral species of
Nothofagus, represented by the fossil pollen species Nothofagidites endurus and N. senectus
(Dettmann et al. 1990). Fossil pollen representing the four extant subgenera of Nothofagus
(Hill and Read 1991) are not recorded earlier than the Late Campanian. Other newly arrived
taxa include horsetails (Ephedra), palms (Longapertites) and a fossil member of the
Didymelaceae, which now is confined to angiosperm rainforest in Madagascar (Schizocolpus
marlinensis).
6.6.3 Palaeoclimates
Assuming that ancestral Nothofagus has similar preferences to modern Nothofagus,
differences in relative abundance of Nothofagidites indicates strong contrasts in rainfall and
mean annual temperatures between the palaeo-northern and southern margins. The presence
of palms (Palmae) is assumed to indicate very warm to hot conditions.
Palaeo-northern Australia
Podocarp-dominated Austral Conifer Forest and fern heath remained the dominant vegetation
types in coastal regions throughout the Early Campanian. Conditions are likely to have been
wet to very wet (humid-perhumid) and very warm (upper mesotherm) based on the presence
of palms. Rare taxa in the offshore sequences include two probable temperate rainforest taxa,
Lophosoria and Nothofagus (Nothofagidites sp. cf. N. senectus), which may imply conditions
away from the coast were cooler with more uniform rainfall than in the Turonian-Santonian.
Palaeo-central Australia
No fossil evidence is available and it is uncertain whether temperate rainforest angiosperms
such as Nothofagus were present in central Australia at this time.
Palaeo-southern Australia
Austral Conifer Forest and fern heath remained the dominant vegetation types in the southern
margin basins although araucarians are less common than during the Turonian-Santonian,
possibly because of different depositional contexts (reduced Neves Effect), and ancestral
species of Nothofagus (Nothofagidites endurus, N. senectus) became frequent to common at
many sites in the late Early Campanian. The latter is consistent with increasingly wet
(perhumid) and/or more uniform conditions, although mean annual temperatures are likely to
have remained within the microtherm range due to the high palaeolatitude (~70 0 S).
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