OFR 151.pdf - CRC LEME

(possibly upper mesotherm) and drier (humid) to the south where meandering river systems
were bordered by sedge and burr-reed swamps and brackish to freshwater lakes.
3.3.4 South-West Australia
Except for three samples from the offshore Carnarvon Basin and adjacent Pilbara region, the
microfossil data come from coastal and palaeochannel deposits in southern south-west
Australia, e.g. the Officer and Eucla Basins and southern margin of the Yilgarn Craton. The
majority of described and undescribed species are found in Late Eocene microfloras in
southeastern Australia (cf. Stover and Partridge 1982).
1. Carnarvon Basin
Basal to early Middle Eocene microfloras recovered from Alpha North-1 in the Carnarvon
Basin are dominated by dinoflagellates but two cuttings samples (1060-1105 m) yielded
statistically significant numbers of spores and pollen (M.K. Macphail unpubl. data). These
imply the coastal plain vegetation was dominated by Casuarinaceae, Proteaceae (diverse,
including Proteacidites pachypolus) and unidentified tricolporate types, with a variable
presence of ferns (Cyathidites), gymnosperms (Araucaria, Agathis/Wollemia, Dacrydium,
Podocarpus-Prumnopitys) and sclerophyll angiosperms such as Euphorbiaceae (Austrobuxus)
and Myrtaceae (Myrtaceidites parvus-mesonesus but also including a possible Eucalyptus).
Rare taxa include Cyathea, Gleicheniaceae, Pteris, Ephedra, Dicksoniaceae, Anacolosa
(Anacolosidites acutullus), Palmae (Arecipites), Banksia/Dryandra, Cupanieae, Liliaceae
(Liliacidites bainii), Nothofagus (Brassospora), N. (Fuscospora), Restionaceae (Milfordia
homeopunctata), Sapindaceae (Dodonaea), and Stylidiaceae (Tricolpites stylidioides).
2. Pilbara region
A possible Late Eocene palynoflora is preserved at Glenflorrie on the lowland plain between
the Hamersley Ranges and the Exmouth Gulf in the Pilbara region (Truswell 1987b). The
microflora is dominated by Nothofagus (Brassospora) spp. (47%), Casuarinaceae (25%),
Proteaceae (~7%) and a periporate type that may represent Trimeniaceae (3%). Rare taxa
include Gleicheniaceae, Podocarpaceae (Dacrydium, Lagarostrobos, Microcachrys),
Agavaceae (Phormium), Palmae (Arecipites), Cupanieae, Ericales, Escalloniaceae
(Quintinia), Euphorbiaceae, Gyrostemonaceae (Gyropollis psilatus), Restionaceae (Milfordia
spp.), and Santalaceae (Santalumidites cainozoicus). The association of Santalumidites
cainozoicus (Santalaceae) and Proteacidites reticulatus (Ungeria) makes it improbable that
the flora is older than Middle Eocene although it could be as young as Oligo-Miocene if these
taxa survived into Neogene time in northwestern Australia. For example, Santalum spp. are
widespread in the present-day floras of Western and South Australia and the Northern
Territory. The Glenflorrie assemblage appears to mark the northwestern limit reached by
Nothofagus during the Tertiary in Australia.
Inferred Climate
Rainfall was adequate (humid) to support wetland communities but the mixture of sclerophyll
and rainforest trees suggests precipitation in the northern Carnarvon Basin was high
(perhumid) but strongly seasonal. Since palms such as Nypa are no longer recorded, mean
temperatures were cooler (lower mesotherm) than in northwestern Australia.
Microflora from the adjacent Pilbara region is likely to represent at least two geographically
distinct vegetation types: Nothofagus temperate rainforest communities growing at higher
elevations on the Hamersley Ranges (max. elevation 700-950 m) and warm temperatesubtropical
rainforest communities lining rivers on the coastal plain. If correct, conditions in
the uplands were relatively cool (lower mesotherm) and uniformly wet (perhumid) possibly
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