Age and Paleoenvironmental Significance of the Frazer Beach Member—A New Lithostratigraphic Unit Overlying the End-Permian Extinction Horizon in the Sydney Basin, Australia

The newly defined Frazer Beach Member of the Moon Island Formation is identified widely across Sydney Basin in both outcrop and exploration wells. This thin unit was deposited immediately after extinction Glossopteris flora (defining terrestrial end-Permian event). rests conformably on uppermost Permian coal seam most places. A distinctive granule-microbreccia bed locally represented at base member. otherwise consists dark gray to black siltstone, shale, mudstone and, locally, lenses fine-grained sandstone tuff. member represents topmost Newcastle Coal Measures overlain gradationally by Dooralong Shale or with a scoured (disconformable) contact coarse-grained sandstones conglomerates Cliff Sandstone, Munmorah Conglomerate laterally equivalent units. characterized palynological “dead zone” high proportion degraded wood fragments, charcoal, amorphous organic matter fungal spores. Abundant freshwater algal remains initial stages vascular plant recovery are low-diversity spore-pollen suites upper part some areas. These assemblages referable Playfordiaspora crenulata Palynozone interpreted as latest age basis precision Chemical Abrasion Isotope Dilution Thermal Ionization Mass Spectrometry (CA-IDTIMS) dating volcanic ash beds within stratigraphically bracketing unit. Plant macrofossils recovered from succeeding strata dominated Lepidopteris (Peltaspermaceae) Voltziopsis (Voltziales) subsidiary pleuromeian lycopsids, sphenophytes, ferns. Sparse vertebrate invertebrate ichnofossils also overlying this correlative, part, interval organic-rich mudrocks, commonly known “marker mudstone” capping succession further north Bowen, Galilee Cooper basins. broad geographic distribution generally <5-m-thick mudrock highlights development eastern Gondwana extensive, short-lived, shallow lacustrine systems impoverished biotas alluvial plain settings immediate aftermath biotic crisis.