OFR 151.pdf - CRC LEME

Australian assemblages, located on the palaeo-northern margin. This provincialism is likely
to reflect latitudinal gradients in climate.
Zone B macrofloras (Necomian-Barremian) are defined by the first appearance of Ginkgoites
although the climatic significance of this, if any, is unclear. Associated fossils suggest
ginkgophytes were a sub-canopy tree in podocarp-dominated forests. Other understorey and
ground taxa included corystosperms, cycads, cycadeoids and pteridosperms/Pentoxylales.
One of the latter (Taeniopteris daintreei) was deciduous, and its leaves are the most
commonly preserved Early Cretaceous macrofossils in Victoria (Douglas 1986). Their large
leaf size (average length 15 cm) implies high rainfall. Fossil wood displays distinct growth
rings.
Inferred climate
Until relatively recently, Early and Late Necomian climates were inferred to have been
subtropical (humid, stormy) and warm temperate, respectively (Douglas 1986, 1994). These
reconstructions have been challenged by Rich et al. (1988) who argue that the plant (and
faunal) assemblages are more consistent with seasonally cool-cold (lower mesotherm) and
humid conditions due to the high palaeolatitude (~70 0 S).
1.2 Microfloras
Relative abundance data supports the macrofossil evidence that the Berriasian-Barremian
vegetation was a form of Austral Conifer Forest dominated by araucarians (Araucariacites,
Balmeiopsis) and podocarps (Microcachrydites, Podocarpidites). Cheirolepidaceae conifers
appear to have been restricted to areas adjacent to the coasts.
Understorey taxa included pteridosperms (Alisporites, Vitreisporites), cycadophytes,
ginkgophytes and bennettitaleans. Prominent ferns are Osmundaceae (Baculatisporites,
Osmundacites), Cyatheaceae (Cyathidites, Dictyophyllidites), Dicksoniaceae and/or
Matoniaceae (Matonisporites, Dictyophyllidites). Fern allies (sphenopsids, isoetaleans) are
considered to have formed reed-beds along streams (references in Dettmann et al. 1992,
Dettmann 1994). Some of these cryptogams were sclerophyllous and/or deciduous and
appear to have been adapted to seasonally very cold and/or dry habitats.
1.2.1 North-West Australia
1. North West Shelf
Changes in the lithology of sediments dredged from the continental shelf reflect an increasing
marine influence on the northwestern margin during the Late Triassic and Early Cretaceous.
However the associated Valanginian-Aptian palynofloras preserve little information on the
terrestrial flora except to confirm the presence of schizaeaceous ferns (Anemia) and
brachyphyll araucarians (Burger 1994).
Inferred climate
The limited data hint at humid conditions in coastal districts but provide no evidence of
temperature regimes.
1.2.2 North-East Australia
No known record.
171