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Utilising U-PB zircon CA-IDTIMS dating to precisely recalibrate the Permian-Early Triassic palynozones of Australia

SES Seminar Series Presentation 7 July 2016

Daniel Mantle

Refined Chemical Abrasion-Isotope Dilution Thermal Ionisation Mass Spectrometry (CA-IDTIMS) provides unprecedented analytical precision for dating zircons recovered from air-fall tuffs. This allows chronometric anchor points to be established for fossil biotas recovered from these tuff-bearing sedimentary successions. Utilising this approach, numerous tuffs in the Permo-Triassic basins of eastern Australia and the Canning Basin of Western Australia have been sampled and the resultant high precision CA-IDTIMS dates provide a unique opportunity to tie the largely endemic fossil biotas to the international timescale. Traditionally palynology has been the key biostratigraphic tool employed to correlate among the thick, coal-bearing fluvial to shallow marine successions within these basins. However, the endemic nature of these palynofloras has restricted their use in pan-Australian or broader Gondwanan correlations and largely ruled out confident global ties below stage level. The new chronometric ages, ranging from the Cisuralian to Early Triassic have thus greatly enhanced the potential for accurate global correlations and have also shown that many of the Australian Permian and Early Triassic palynozones are significantly younger than currently accepted.