OFR 151.pdf - CRC LEME

Microfloras preserved in the Lower Lygistepollenites balmei Zone interval (Pebble Point Fm.)
are dominated by Podocarpaceae (Podocarpus-Prumnopitys, Lagarostrobos) with lesser
amounts (3-8%) of Araucariaceae (Agathis/Wollemia), Dacrydium, Microcachrys,
Phyllocladus, Blechnaceae-type, Gleicheniaceae and Sphagnum. Nothofagus (Brassospora,
Fuscospora) increases from ~1% to 4% up-section. Other angiosperms are uncommon except
for Proteaceae (up to 8%) and Callitrichaceae (3-4%) but rare types include Casuarinaceae,
Austrobuxus-type, Gambierina, and Xylomelum occidentale-type.
Microfloras from the overlying Upper L. balmei Zone (Dilwyn Clay) are dominated by
gymnosperms and cryptogams but are more diverse due to the increasing angiosperm
component. Species first appearing in this interval include Anacolosa (Anacolosidites
acutullus) and Tiliaceae (Intratriporopollenites notabilis). Nothofagus and Callitrichaceae
become rare whilst Myrtaceae (M. eugeniioides) comprises up to 17% of the total pollen
count. Nothofagus is uncommon in a similar Proteaceae and Myrtaceae-dominated Late
Paleocene microflora in the Latrobe-1 well in the Port Campbell Embayment.
Microfloras from the onshore Torquay Sub-basin to the east of Princetown include
correlatives of the Lower and Upper Lygistepollenites balmei Zones (M.K. Macphail unpubl.
data). The earlier zone is dominated by ancestral Nothofagus and Proteaceae spp., with
frequent Araucariaceae (Araucaria, Agathis/Wollemia) but Casuarinaceae and Gambierina
are rare. The younger zone is dominated by Araucariaceae (Araucaria, Agathis/Wollemia),
Podocarpaceae (Podocarpus-Prumnopitys) and Gleicheniaceae, associated with Cyatheaceae,
Matoniaceae, Dicksoniaceae, Dacrycarpus, Dacrydium, Halocarpus, Lagarostrobos,
Anacolosa (Anacolosidites acutullus, A. sp. nov.) and an undescribed member of the Northern
Hemisphere Triprojectites group (Integricorpus).
Inferred climate
The Lower Lygistepollenites balmei Zone assemblages represent a form of Austral Conifer
Forest growing under relatively cool (lower mesotherm) and uniform to weakly seasonal and
wet (humid) conditions. The expansion of angiosperms during Upper L. balmei Zone time is
consistent with warming temperatures although the absence of palms indicates mean values
remained within the mesotherm range.
5. Gippsland Basin
Paleocene sediments reach thicknesses of up to 950 m in the offshore Gippsland Basin and
have been intersected in some 650 wells. A review of the well data (Macphail et al. 1994,
A.D. Partridge pers. comm.) indicates that Lygistepollenites balmei Zone microfloras
primarily are dominated by podocarps (Podocarpus-Prumnopitys, Lagarostrobos) and
Proteaceae, with lower, but still high, relative abundances of Dacrydium (including L.
balmei), ancestral Nothofagus (Nothofagidites endurus) and Callitrichaceae. Araucariaceae
(predominantly Dilwynites) are most abundant in distal marine facies, due to the Neves
Effect.
Comparisons of Lower and Upper L. balmei Zone sequences, for example in the Tuna Field
wells (I.R. Sluiter and M.K. Macphail unpubl. data), indicate that angiosperms such as
Gambierina, Peninsulapollis gillii and Tetracolporites verrucosus are more common in the
Early Danian than in younger (Late Danian-Early Thanetian) assemblages. The reverse is
true of ancestral Nothofagus, Callitrichaceae and several extinct Proteaceae. By Late
Thanetian, Gleicheniaceae, Cyatheaceae, Proteaceae and ancestral Nothofagus had replaced
Lagarostrobos, Dacrydium and Callitrichaceae as the most common taxa.
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