Cretaceous coccoliths in the middle Eocene of the western and southern margins of Australia: evidence of a significant reworking episode  

Authors / CoAuthors

Shafik, S.

Abstract

A reworking episode is indicated by occurrences of upper Cretaceous coccoliths among middle Eocene assemblages in four basins (Carnarvon, Perth, Eucla, and Otway Basins) along the Australian western and southern margins. The episode falls within the coccolith biostratigraphic interval from the lowest occurrence of Cyclicargolithus reticulatus to the highest occurrence of Daktylethra punctulata, which correlates with the foraminiferal zonal interval P.12-P,13. At the time of the episode (about 45-44 Ma) the sea advanced along the southern margin from the west, causing a transgression in the Eucla Basin and an ingression in the Otway Basin. Coincident with this sea-level rise, and probably the cause of it, was a major acceleration in the spreading rate south of Australia. In the absence of known in-situ occurrences of upper Cretaceous coccoliths on the southern margin or offshore to the south, the Naturaliste Plateau is thought to have been the most likely provenance for the reworked taxa in the Eocene of the Eucla and Otway Basins - short-lived strong currents stripped off coccolith-rich upper Cretaceous sediments on the plateau and transported them eastward. In the Perth Basin a local source, the upper Cretaceous coccolith-rich Gingin Chalk/ Lancelin Beds, is suggested for the reworked taxa, whereas in the Carnarvon Basin a distant source is more likely.

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document

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81198

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• GA PublicationJournal

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_External

Publication Date

1984-01-01T00:00:00

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Australian Government Security ClassificationSystem    

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Creative Commons Attribution 4.0 International Licence    

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geoscientificInformation

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BMR Journal of Australian Geology and Geophysics 9:4:353-359

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