OFR 151.pdf - CRC LEME

(Dacrycarpus, Dacrydium with locally common Phyllocladus), Araucariaceae (Agathis with
locally common Araucaria), Casuarinaceae (Gymnostoma), Elaeocarpaceae, Lauraceae and
Oleaceae. Myrtaceae (Acmena, Syzygium, Tristania) are widely distributed and cycads
(Zamiaceae) are an uncommon but persistent element.
The Oligo-Miocene associations are suggested to represent swamp rainforests with emergent
Araucariaceae and Myrtaceae and a shrubby understorey of ferns, Podocarpaceae, Proteaceae,
Oleaceae and other small trees and shrubs. Major controls on plant community composition
included variations in the water-table, saltwater incursions and fire.
Inferred climate
Increases in Araucariaceae and Myrtaceae genera with warm temperate to subtropical
rainforest NLRs is consistent with warm (mesotherm range) temperatures and/or low soil
nutrient levels associated with seasonally high humidity. The increased wildfire frequency
may reflect increasingly dry summers during the Middle Miocene but are just as likely to be a
consequence of higher fuel loads accumulating under sclerophyll-dominated communities.
4.1.7 Tasmania
1. Northern Tasmania
Fern pinnules which are identical to living South American fern Lophosoria quadrapinnata
and bearing intact sporangia containing Cyatheacidites annulatus spores are preserved in
Oligo-Miocene lignites at Balfour on the north-west coast (R.S. Hill pers. comm.). A
probable Oligocene (Proteacidites tuberculatus Zone) macroflora is preserved at Pioneer at
about 90 m elevation in northeastern Tasmania. This flora is dominated by the leaves of an
extinct Nothofagus (Lophozonia) species and an unidentified angiosperm characterized by
entire-margined notophylls (Hill and Macphail 1983). Less common taxa include
Cupressaceae (Athrotaxis), Podocarpaceae (Dacrydium, Phyllocladus), Myrtaceae and
Proteaceae (Banksieaephyllum).
Inferred climate
Lophosoria and high relative abundances of Nothofagus (Lophozonia) dominance indicate
cool (upper microtherm) temperatures and uniform high humidity in northern Tasmania.
2. Central Plateau
Six Oligocene to possible late Early Miocene (Proteacidites tuberculatus Zone) macrofloras
have been described from Bells Plains (~600 m elevation), Cethana (~300 m elevation), Lea
River, (~800 m elevation), Lemonthyme Creek (~350 m elevation), Little Rapid River (~350
m elevation) and Monpeelyata (~920 m elevation) (Hill and Gibson 1986, Hill 1987,
Carpenter and Hill 1988, Wells and Hill 1989, Hill and Carpenter 1989, Carpenter 1991b,
Carpenter and Buchanan 1993, Hill et al. 1993, Carpenter et al. 1994a, Jordan 1995, Jordan
and Hill 1996, Jordan et al. 1996, Hill and Whang 1996).
In most cases the focus is on the taxonomic relationships of fossil species rather than the
source vegetation (inferred to be gymnosperm-Nothofagus temperate rainforest). For
example, at least 20 conifer and up to 60 angiosperm species are present at Cethana and Little
Rapid River. Mean leaf sizes fall within the microphyll and nanophyll classes. Unlike Oligo-
Miocene sites on the mainland, foliage of the typically microtherm subgenus Nothofagus
Lophozonia is common to abundant in most assemblages.
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