OFR 151.pdf - CRC LEME

Data on Middle-Late Eocene microfloras are unavailable or the reports predate the
development of the Gippsland zonation. For example, Harris (1965c) has proposed a
microflora from Spring Bay near Triabunna on the east coast is Middle Eocene based on the
high relative abundance of Proteacidites pachypolus. If a related morphotype in the same
assemblage is P. asperopolus, then the sample will be Middle Eocene; if not, the sample
could be Late Eocene. Other taxa listed as common are ferns (Cyatheaceae), Ephedra and
Nothofagus (presumably Nothofagidites emarcidus-heterus). Comparable assemblages are
said to occur in the Longford area, near Launceston (Harris ibid).
Inferred Climate
The absence of Anacolosa and Triorites magnificus in Nothofagus (Brassospora) microfloras
is likely to indicate that conditions in the Bass basin and south-east Tasmania were as
uniformly wet (perhumid) but cooler (microtherm to lower mesotherm range) than the
Gippsland Basin during the Late Eocene.
3.3 Other Records
3.3.1 North-West Australia
1. North-West Shelf
Apthorpe (1988) notes that Late Eocene warming proposed, e.g. by McGowran and Beecroft
(1985) is consistent with the presence of ‘larger’ benthic foraminiferal faunas on the North
West Shelf and the presence of warm temperate faunas in the northern Canning Basin.
2. Carnarvon Basin
The progressive decline in clastic input to the northern Carnarvon Basin and enhanced
carbonate sedimentation implies rainfall had decreased relative to the early Eocene (Apthorpe
1988).
3.3.2 North-East Australia
Feary et al. (1991) have proposed low latitude regions underwent slight cooling.
3.3.3 South-West Australia
Cenozoic brachiopod assemblages in the Eucla Basin indicate relatively stable conditions
during the Late Eocene-Miocene or (preferred) that brachiopods are more influenced by
substrate than other environmental parameters.
3.3.4 South-East Australia
Planktonic foraminifera indicate sea surface temperatures cooled rapidly during the early
Middle Eocene (McGowran et al. 2000). An oxygen isotope stratigraphy based on planktonic
foraminifera from Browns Creek and Castle Cove in southwestern Victoria, indicates SSTs at
the eastern end of the Bight reached a maximum value of ~24 0 C during the Late Eocene (cf.
Kamp et al. 1990, Shafik 1996)
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