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Depositional age and correlation of the Oonah Formation: refining the timing of Neoproterozoic basin formation in Tasmania


Mulder, JA and Berry, RF and Halpin, JA and Meffre, S and Everard, JL, Depositional age and correlation of the Oonah Formation: refining the timing of Neoproterozoic basin formation in Tasmania, Australian Journal of Earth Sciences, 65, (3) pp. 391-407. ISSN 0812-0099 (2018) [Refereed Article]

Copyright Statement

Copyright 2018 Geological Society of Australia

DOI: doi:10.1080/08120099.2018.1426629


The Proterozoic Oonah Formation comprises a thick sequence of turbidites and mafic rocks that is widely exposed in western and northern Tasmania. The regional significance of the Oonah Formation is poorly understood as its contacts are faulted and estimates of its depositional age range from 1450 Ma to 700 Ma. Here we refine the depositional age of the Oonah Formation and clarify its relationship to other Proterozoic sequences in Tasmania. Magmatic apatite from the syn-sedimentary Cooee Dolerite has a 207Pb-corrected 238U/206Pb age of 733 ± 9 Ma that provides a robust estimate of the depositional age of the Oonah Formation. The Oonah Formation contains abundant 750 Ma detrital monazite and has detrital zircon age populations at 1800–1700 Ma, 1590 Ma, and 1450 Ma. The new age and provenance data support the interpretation that the Oonah Formation is a lateral equivalent of the base of the Togari Group and correlatives in Tasmania. We demonstrate that the stratigraphy and provenance of Neoproterozoic strata in Tasmania differ from time-equivalent sequences in Adelaide Rift Complex but are similar to the Pahrump Group (Death Valley, California) and the Cobham Formation (Transantarctic Mountains), which supports a southwest Laurentia—Tasmania—East Antarctica connection within supercontinent Rodinia.

Item Details

Item Type:Refereed Article
Keywords:Oonah Formation, Togari Group, detrital monazite, detrital zircon, Tasmania, southeast Australia, Rodinia, Neoproterozoic, rifting
Research Division:Earth Sciences
Research Group:Geology
Research Field:Structural geology and tectonics
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Mulder, JA (Mr Jacob Mulder)
UTAS Author:Berry, RF (Associate Professor Ron Berry)
UTAS Author:Halpin, JA (Dr Jacqueline Halpin)
UTAS Author:Meffre, S (Dr Sebastien Meffre)
ID Code:124306
Year Published:2018
Web of Science® Times Cited:5
Deposited By:Oceans and Cryosphere
Deposited On:2018-02-16
Last Modified:2018-11-26

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