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

journal contribution
posted on 2023-05-19, 16:02 authored by Mulder, JA, Ronald BerryRonald Berry, Jacqueline HalpinJacqueline Halpin, Sebastien MeffreSebastien Meffre, Everard, JL
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.

History

Publication title

Australian Journal of Earth Sciences

Volume

65

Pagination

391-407

ISSN

0812-0099

Department/School

School of Natural Sciences

Publisher

Blackwell Publishing Asia

Place of publication

54 University St, P O Box 378, Carlton, Australia, Victoria, 3053

Rights statement

Copyright 2018 Geological Society of Australia

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

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