OFR 151.pdf - CRC LEME

Araucaria (4-13%; av. 8%) and Nothofagus (Lophozonia) spp. (1-3%) are slightly higher.
However the interval can be distinguished by consistent occurrences of mostly thermophilous
taxa that were rare or absent in the P. tuberculatus Zone Equivalent, e.g. Cyathea, Pteris,
Acacia, Aquifoliaceae (Ilex, Sphenostemon), Palmae (Dicolpopollis), Caesalpinaceae,
Convolvulaceae (Merremia-type), Ericales, Haloragaceae (Gonocarpus/Haloragis),
Quintinia, Rubiaceae (Gardenia, Randia) and Winteraceae. Nothofagus (Lophozonia) spp.
and Phyllocladus become rare, and Trimeniaceae and Lagarostrobos are absent during the
zone.
Inferred climate
The pollen data confirm that climates in western Murray Basin were sub-optimal (possibly
seasonally too dry) for the extensive development of either Nothofagus or Araucariaceaedominated
rainforest although conditions were markedly wetter (humid) and overall warmer
(mesotherm range) than at present. Trends in rare taxa suggest mean temperatures reached a
maximum during the late Early to Middle Miocene. Araucaria and Lagarostrobos values
imply climates became effectively drier/more strongly seasonal at about the same time. The
prominence of Poaceae suggests marine flooding favoured the expansion of grasslands around
the shoreline at a time when grasses were relatively rare in the interfluve vegetation.
b. Central Murray Basin
Much of the detailed information comes from four fully cored drill holes, Hatfield-1, Manilla-
1, Piangil West-2 and Woodlands-1 (Macphail and Truswell 1989), augmented by a much
larger number of boreholes, which have been sampled by cuttings only (Macphail 1999).
Unlike the western sector, the central (depocentre) region appears to preserve correlatives of
the earliest Oligocene Upper Nothofagidites asperus Zone deposits of the Gippsland Basin,
e.g. Hatfield-1, located near the present confluence of the Lachlan and Murrumbidgee Rivers.
These are defined by the first appearance of cf. Epilobium (Onagraceae) and Archidendrontype
(Mimosaceae) in Nothofagus (Brassospora) dominated microfloras, which lack
Lophosoria.
Relative pollen abundance in these earliest Oligocene (Upper Nothofagidites asperus Zone
Equivalent) microfloras show little change. Araucariaceae values are intermediate between
values recorded in the Late Eocene and Middle N. asperus Zone Equivalent (see Figure 8 in
Macphail and Truswell 1989). Nothofagus (Brassospora) values tend to be lower/more
irregular than during the Late Eocene and commonly occurring types include Casuarinaceae
and non-eucalypt Myrtaceae. Pollen dominance in Early Oligocene-early Late Miocene
(Proteacidites tuberculatus Zone Equivalent) microfloras is similar but Nothofagus
(Brassospora) values are even more variable whilst those of Araucariaceae, Casuarinaceae
and Myrtaceae increase towards the top of the zone. These trends are variably maintained
during the Canthiumidites bellus Zone Equivalent, leading to Casuarinaceae and/or
Araucariaceae being as common as or more abundant than Nothofagus (Brassospora) at the
top of the Canthiumidites bellus Zone Equivalent in the Manilla-1, Piangil West-2 and
Woodlands-1 boreholes. Araucariaceae reaches maximum values within this zone.
Cyperaceae, Restionaceae and Sparganiaceae are more abundant in microfloras recovered
from the marginal marine Geera Clay than in the underlying (fluvio-lacustrine) Renmark
Formation. This implies these wetland taxa formed specialised shoreline and strand
communities. Probable Early Miocene microfloras from marine sediments in the Balranald
area (Pickett and McMinn 1983) are dominated by Nothofagus (Brassospora), Casuarinaceae
and Myrtaceae (total ~90-95%). Rare taxa include Araucaria, Dacrydium, Cupanieae, and
Quintinia.
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