OFR 151.pdf - CRC LEME

The lowest and possibly the oldest (possible Early Oligocene) Cethana flora is unique in
including cycads (Zamiaceae). Other taxa assigned to living genera include Blechnaceae (cf.
Blechnum), Gleicheniaceae (Gleichenia, Sticherus), Schizaeaceae (Lygodium), Araucariaceae
(Araucaria, Agathis), Cupressaceae (Papuacedrus), Podocarpaceae (Acmopyle, Dacrycarpus,
Dacrydium, Lagarostrobos, Phyllocladus, Podocarpus), Casuarinaceae (Gymnostoma),
Cunoniaceae (Callicoma, Cunonia-Weinmannia), Nothofagus (Brassospora, Fuscospora,
Lophozonia) and diverse Proteaceae (including Banksieaephyllum and Lomatia),
Elaeocarpaceae, Epacridaceae, Lauraceae, Myrtaceae and Sterculiaceae (Brachychiton). The
Banksieaephyllum specimens show scleromorphic and xeromorphic features.
The majority of these taxa are recorded at Lea River, Lemonthyme Creek and Little Rapid
River. Additional species include an extinct Dicksonia with close affinities to extant
subtropical and tropical species, and Eucryphia (Barnes and Jordan 2000). Conifers include
Libocedrus and Fitzroya (Cupressaceae), now confined to the South-west Pacific and South
America, respectively, and an extinct species of Athrotaxis (Taxodiaceae), now endemic to
Tasmania. An extinct genus of Taxodiaceae (Austrosequoia), previously known only from
the early Late Cretaceous Winton Formation, Queensland (Peters and Christophel 1978),
occurs at Little Rapid River.
The highest and probably youngest macroflora (Early Miocene) at Monpeelyata includes a
shrub podocarp that is virtually identical to the endemic species Microstrobos niphophilus,
found in the upper subalpine-alpine zone in Tasmania. The same flora includes Isoetes, and
Proteaceae whose leaves are similar to microphyll sclerophyll plants growing in the modern
subalpine vegetation, and by association a cool-adapted Araucariaceae.
Inferred climate
Foliar physiognomic analysis (Carpenter et al. 1994a) indicates mean annual temperatures at
moderate elevations (Cethana) were at the top of the upper microtherm range (~12 0 C) during
the Oligocene whilst temperatures at higher elevations (Monpeelyata) were much cooler
(~7.5 0 C) during the Early Miocene. High-grade (V) fungal germlings demonstrate conditions
were uniformly wet to very wet (>1400-1500 mm pa) despite sclerophyllous adaptations to
increasing seasonal stress.
4.2 Microfloras
Most of the macrofossil deposits also preserve diverse microfloras. Regions for which only
microfossil data are available include northwestern, southwestern and central Australia. The
index species of the Proteacidites tuberculatus Zone, Cyatheacidites annulatus, is found as
far north as southern Queensland but has not been recorded in central, northern or western
Australia (M.K. Macphail unpubl. observations). One Tasmanian site potentially preserves a
world-class record of the impact of abrupt cooling during the Eocene-Oligocene transition on
a high latitude flora (Macphail et al. 1993, Macphail and Hill 1994). However, the index
species of the Canthiumidites bellus Zone, C. bellus, has not been recorded in Tasmania,
making it difficult to distinguish between Early Oligocene-late Early Miocene and late Early-
Middle Miocene floras. Martin (1990) has demonstrated that reports of extensive grasslands
in central Australia during the Miocene (cf. Truswell and Harris 1982) are based on a
misidentification of fossil graminoid Restionaceae pollen (Milfordia homeopunctata) as
Poaceae (Graminidites).
247