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OFR 151.pdf - CRC LEME

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4. TIME SLICE K-4<br />

Age Range: Turonian-Santonian [91-83 Ma]<br />

Zones: Phyllocladidites mawsonii to Tricolporites apoxyexinus Zones<br />

Palaeohystrichophora infusorioides to lower Nelsoniella aceras<br />

Zones<br />

4.1 Macrofloras<br />

Douglas (1994) has noted that an unidentified cuticle is a major component in microfossil<br />

preparations.<br />

4.2 Microfloras<br />

Marine and non-marine sediments preserving Turonian-Santonian palynofloras occur in<br />

offshore basins along the southern, western and northern margins. Dettmann (1973) reviewed<br />

records of angiosperm pollen and noted that, unlike earlier geological intervals, it is possible<br />

to assign a number of newly evolved or arrived gymnosperms and angiosperms to modern<br />

genera with a moderate to good degree of confidence. For example it is highly probable that<br />

Dilwynites represents the araucarian genera Agathis and/or Wollemia, whilst Lygistepollenites<br />

and Phyllocladidites represent the podocarp genera Dacrydium and Lagarostrobos,<br />

respectively.<br />

4.2.1 North-West Australia<br />

1. Bathurst Island<br />

Dinoflagellate evidence does not support the claim (Norvick and Burger 1975) that<br />

palynosequences from Bathurst Island range into Early Turonian time. However, exploration<br />

wells drilled on the North West Shelf occasionally intersect Turonian-Santonian,<br />

Phyllocladidites mawsonii Zone Equivalent units, which preserve significant numbers of<br />

pollen and spores. None of these have been systematically documented thus far.<br />

2. Bonaparte Basin<br />

Limited evidence from Jacaranda-1, in the Bonaparte Basin (Helby and Partridge 1985, M.K.<br />

Macphail unpubl. results) points to ferns (Cyatheaceae), podocarps (Podocarpus-<br />

Prumnopitys) and/or pteridosperms (Alisporites) being amongst the more common taxa<br />

during Santonian (Isabelidinium cretaceum Zone) time. Rare angiosperms include<br />

Callitrichaceae (Australopollis obscurus), Gunnera (Tricolpites reticulatus), Liliaceae<br />

(diverse), Ilex, Proteaceae and a probable palm (Dicolpopollis sp.) plus a range of extinct<br />

angiosperms producing small tricolpate and tricolporate pollen types.<br />

Inferred climate<br />

The combined data point to seasonally humid-perhumid and probably very warm (upper<br />

mesotherm) conditions along the palaeo-northern margin despite its palaeolatitude (~50 0 S).<br />

185

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