GEOCHEMICAL RECORDS OF THE PERMIAN-TRIASSIC BOUNDARY INTERVAL IN A HIGH-LATITUDE, CONTINENTAL MARGIN SETTING (SYDNEY BASIN, AUSTRALIA)

The Permian-Triassic transition was marked by an ecological catastrophe involving rapid and severe environmental change that led to the largest mass extinction of the geological record. Most work on the continental record of this interval has focused on low-paleolatitude settings. As such, the extent to which terrestrial systems at high paleolatitudes were impacted remains relatively poorly constrained. The Upper Permian to Lower Triassic succession in the Sydney Basin, Australia, deposited along an ancient continental margin that stretched from polar to temperate paleolatitudes, comprises one of the best geochronologically calibrated terrestrial records for the time period. This work presents new carbon isotopic and elemental profiles generated from a suite of outcrop and drillcore sections positioned across the length and breadth of the Sydney Basin. Results are considered in a context of sedimentological, paleobotanical, and geochnronological data collected from the same sections and integrated into paleoclimate models for the region. Carbon isotope profiles derived from sedimentary organic matter in coal, mudrock, and fine-grained sandstone indicate a stable carbon cycle through the Lopingian. A series of negative excursions beginning at the putative Permo-Triassic boundary and continuing through the Induan postdate the major floral turnover. Elemental profiles from shales indicate that the vegetative turnover (EPME) occurred during a period of enhanced chemical weathering. Spikes in nickel concentrations at the EPME, interpreted as a signal of Siberian Trap volcanism, could provide a useful stratigraphic indicator and may suggest a role for nickel poisoning in terrestrial extinctions. These higher frequency fluctuations overprint a long term warming trend through the Wuchiapingian to mid-Olenekian. In this basin, the terrestrial turnover is recorded in mudrocks that overlie the uppermost coal seam. Downcutting and erosion by Triassic fluvial systems has led to variable preservation of the interval. In this regard, geochemical profiles are also useful for regional correlation between sites.