OFR 151.pdf - CRC LEME

index species of the Middle N. asperus Zone, Triorites magnificus (cf. Lindsay and Harris
1964, McGowran et al. 1970, Alley and Broadbridge 1992). Examples occur in the North
Maslin Sand, Maslin Beach, and outliers at Golden Grove (Alley 1987) and One Tree Hill
(Alley and Broadbridge 1992) in the Willunga Embayment. Correlative formations are
routinely intersected on the northern Adelaide Plain, e.g. Harris (1964a, 1965b).
Microfloras recovered from the North Maslin Sand (Noarlunga sandpit) are dominated by
Proteaceae (abundant, diverse), Casuarinaceae and Nothofagus (Brassospora) spp. (common)
and Cupanieae (frequent) (M.K. Macphail unpubl. data). Rare taxa include Podocarpaceae
(Dacrycarpus, Dacrydium, Lagarostrobos, Podosporites sp. cf. Microstrobos), Anacolosa
(Anacolosidites luteoides, A. sectus), Palmae (Arecipites), Caesalpinaceae, Didymelaceae,
Euphorbiaceae (Austrobuxus-type, Micrantheum), Ilex, Loranthaceae, Nothofagus
(Fuscospora, Lophozonia, Nothofagus), Pandanaceae (Freycinetia), Polygalaceae,
Restionaceae (Milfordia homeopunctata), Santalum, Sapotaceae and Trimeniaceae.
Cryptogams are uncommon.
Conversely, cryptogams are common at Golden Grove and One Tree Hill where fern spores
(Blechnaceae, Calochlaena/Culcita, Cyathidites, Gleicheniaceae, Osmundaceae,
Polypodiaceae) comprise up to 52% of some assemblages. Podocarpus-Prumnopitys is
frequent (up to 8%). Otherwise, pollen dominance and species composition is similar to the
Noarlunga sandpit microfloras. Rare taxa not recorded at Noarlunga include Araucariaceae
(Araucaria, Agathis/Wollemia), Podocarpaceae (Halocarpus), Ascarina, Triorites magnificus
and a plethora of undescribed tricolporate types. Triorites magnificus is recorded at One Tree
Hill and is present in other boreholes drilled ca. 3-4 km east of Maslin Bay (Harris 1964a,
1974) where it is associated with Dicksonia, Podocarpaceae (Dacrycarpus, Dacrydium,
Lagarostrobos, Podocarpus-Prumnopitys) Anacolosa (Anacolosidites acutullus, A. luteoides),
Ascarina, Cupanieae, Euphorbiaceae, Ilex, Loranthaceae, diverse Proteaceae, Santalum and
Sapotaceae.
Correlative microfloras (with Triorites magnificus) from the northern Adelaide Plains are
dominated by Nothofagus (Brassospora) and Proteaceae. Rare taxa include Cyatheaceae,
Anacolosa (Anacolosidites acutullus), Cupanieae, Loranthaceae, Myrtaceae (including
Eucalyptus), Nothofagus (Fuscospora, Lophozonia), Proteaceae (including
Banksia/Dryandra, Beauprea, Isopogon and extinct species such as Proteacidites reticulatus)
and Santalum.
Inferred Climate
The presence of both Nypa and Nothofagus (Brassospora)-Lagarostrobos rainforest in the
Polda Basin is difficult to reconcile given the former imply very warm-hot (upper mesothermmegatherm)
conditions whilst the latter indicate mean annual temperatures were within the
lower mesotherm range. Assuming that Nypa pollen are in situ, i.e. not reworked from Early
Eocene deposits, the most likely explanation is that sea surface temperatures within sheltered
embayments in the Bight were warm relative to air temperatures. The record is an important
one as it supports other data for existence of a warm water gyre within the Bight during Late
Eocene. Conversely, the high relative abundance of Nothofagus at Tarcoola implies relatively
cool (lower mesotherm) and uniformly wet (perhumid) conditions on the margins of the
Gawler Craton.
The Maslin Bay Sand microfloras closely resemble those found in the Eucla and Gippsland
Basins during the Late Eocene and almost certainly represent similar relatively warm
(mesotherm range) and uniformly wet (perhumid) climates. This may reflect the local
influence of, for example, warm SSTs within the St. Vincents Gulf. Support for this is
provided by the possibly early, widespread presence of thermophilous taxa such as
Anacolosidites sectus and Triorites magnificus. If correct, then again the most probable
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