New Middle Permian - Early Triassic U-Pb zircon CA-IDTIMS isotopic ages of tuffs in the Sydney Basin, Australia: International calibration of stratigraphy and biostratigraphy

Abstract

The Middle Permian-Early Triassic (MP-ET) of Eastern Australia contains a predominantly endemic biota precluding precise correlation with standard international biozones and System/Stage boundaries. The Permian-Triassic boundary, other MP-ET stage boundary levels, and the major end-Guadalupian and end-Permian mass extinction levels in Australia remain poorly constrained. Attempts to calibrate the MP-ET of Australia using Sensitive High Resolution Ion Microprobe techniques have resulted in controversial radioisotopic ages with percent-level uncertainty and compromised accuracy due to the use of an unsuitable standard. We here report eighteen new high-precision (<±0.05 my) U-Pb CA-IDTIMS ages for tuffs in the Sydney Basin based on isotopic dating of chemically abraded individual zircons. These dates provide vital international timescale tie points for the MP-ET of Australia.