UTILISING U-PB ZIRCON CA-IDTIMS DATING TO PRECISELY RECALIBRATE THE PERMIAN-EARLY TRIASSIC PALYNOZONES OF EASTERN AUSTRALIA

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 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. Furthermore as the key Permian correlative fossil groups - conodonts, fusulinid and benthic foraminifera, and ammonites - are also extremely rare or absent from the cold water marine realms of eastern Australia during this period, there are no alternative fossil tie-points. Therefore the new chronometric ages, ranging from the Cisuralian to Early Triassic, that tie the local spore-pollen zones to the Geologic Timescale have 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.