International timescale calibration of the Late Permian - Early Triassic of Australia

Abstract

The Late Permian - Early Triassic interval of Australia contains a predominantly endemic biota. A paucity of international marine index fossils, in particular conodonts and ammonoids, has previously precluded precise correlation with standard northern hemisphere marine sequences and internationally established System and Stage Global Stratotype Sections and Points (GSSPs). The Permian-Triassic boundary and other Late Permian and Early Triassic stage boundary levels, and the major end-Guadalupian and latest Changhsingian (end-Permian) mass extinction levels in Australia remain poorly constrained. Attempts to calibrate the Late Permian - Early Triassic of Australia using U-Pb analyses on of zircons from volcanic products using micro-beam Sensitive High Resolution Ion Microprobe (SHRIMP) techniques have resulted in controversial radio-isotopic ages with per cent-level uncertainty and accuracy that may be compromised due to the use of a standard which is now deemed unsuitable. We will present new high-precision biostratigraphic, isoptopic geochronologic (U-Pb IDTIMS ages on chemically abraded individual zircons with permil-level resolution) and chemostratigraphic data that provide important international timescale calibration points in the Late Permian - Early Triassic of Australia. We expect that through integration of U-Pb and 40Ar/39Ar geochronology with chemo- and biostratigraphy, that the time scale of the Late Permian - Early Triassic of Australia will be greatly improved and will lead to more realistic evaluation of high-latitude end-Guadalupian and end-Permian biotic crises and their aftermaths and greater understanding of climate change in Australia and globally during this economically important time period.