THE PERMIAN STABLE ISOTOPE RECORD FROM ICE-PROXIMAL LOCALITIES IN EASTERN AUSTRALIA: A PROXY FOR LATE PALEOZOIC CLIMATE CHANGE

Most stable isotope records that span the late Paleozoic ice age are based on brachiopod calcite collected from paleoequatorial marine deposits in North America, Europe, and the Russian Platform. Correlation of these records has revealed global variations in the δ¹³C value of marine carbonate, which have been attributed to variations in pCO₂, changes in rates of silicate weathering, and/or a restructuring of oceanic circulation patterns that led to periods of global cooling and glaciation. By contrast, the ice-proximal record of Gondwana has long been undervalued despite its potential to provide information that can be directly correlated with glacially influenced strata. Here we present a new high-latitude isotope record and interpret it within the framework of a recent sedimentological and stratigraphic re-evaluation of the late Paleozoic record in eastern Australia. Calcareous climate-sensitive components and sedimentary organic matter were collected from both glacially influenced and distinctly nonglacial facies in the early Permian Yessabah Limestone, Wandrawandian Siltstone, and the Lower Pebbley Beach, Beckers, and Billy Brook Formations. Positive shifts in the carbon isotope curve correspond to multiple, short-lived intervals of glaciation that have been identified independently using sedimentological indicators. Isotopic data from these proximal locations thus provide support for a cause-and-effect relationship between pCO₂ and glaciation a notion that has been challenged in recent years.