U-Pb (CA-TIMS) zircon geochronology of the late permian of Australia: Constraining the time scale between two major extinctions

Abstract

The Bowen and Sydney Basins make up a ca. 600 km long, NNW-trending series of basins in eastern Australia, filled with terrestrial sediments of late Paleozoic to early Mesozoic age. The basins are also important sedimentary archives of evolutionary events in eastern Gondwana during times that are characterized by two major extinctions (end Middle Permian and Permian-Triassic extinctions). We present new U-Pb (CA-TIMS) zircon ages for several tuffs interbedded within the sediments, with the purpose of creating a time scale of the Upper Permian as recorded in eastern Australia that allows correlations with different parts of the world. Currently, these correlations mostly depend on carbon-isotope records as well as biostratigraphy and lithostratigraphy that are deemed unsuitable for constructing high-resolution chronostratigraphic framework in absence of robust and precise radio-isotopic ages. The existing SHRIMP U-Pb ages on zircon have been shown to be compromised by inaccuracy and low precision when compared to what is achievable with the CA-TIMS method.