DETERMINATION OF THE PERMIAN-TRIASSIC BOUNDARY IN AUSTRALIA FROM CARBON ISOTOPE STRATIGRAPHY

Significant excursions in the carbon isotope composition of organic matter from sedimentary sections across the Permian/Triassic boundary are documented from the Bonaparte, Canning, Carnarvon, Perth, and Bowen Basins. The analysed sections represent a wide range of depositional environments from marine to non-marine, among which precise time correlation is uncertain. The sense and magnitude of the isotopic excursions are comparable to those found elsewhere around the world from marine carbonates at this time. Early Triassic sediments consistently bear carbon more depleted in the carbon-13 isotope than do latest Permian sediments. The isotope excursion provides an isochronous global datum in the sedimentary record at the palaeontologically determined Permian/Triassic boundary. This carbon isotope chemostratigraphic scheme has application for:correlation between different depositional environments, at scales ranging from intrabasinal to global;comparison of sedimentation rates; andrecognition of lacunas in the sedimentary record.