FACIES AND ALLOSTRATIGRAPHY OF HIGH-LATITUDE, GLACIALLY INFLUENCED MARINE STRATA OF THE EARLY PERMIAN SOUTHERN SYDNEY BASIN, AUSTRALIA

The Sydney Basin of New South Wales, Australia is a foreland basin con taining a thick (up to 10 km) Permo-Triassic succession. The southern margin of the basin exposes strata deposited during Late Palaeozoic gl aciation of south-eastern Gondwana. The Early Permian Wasp Head, Pebbl ey Beach, Snapper Point Formations and Wandrawandian Siltstone were de posited between 277 and 258 Ma on a polar, glacially influenced contin ental margin adjacent to ice sheets located over East Antarctica and e astern Australia. Sedimentary facies, together with related ichnofacie s and fauna, can be grouped into six facies associations that record m arine sub-environments ranging from high energy, storm-dominated inner shelf to turbidite-dominated upper slope settings. Cold marine condit ions, with near-freezing bottom water temperatures, are recorded by gl endonites. Ice-rafted debris, most likely deposited by icebergs, occur s in almost all facies associations. An allostratigraphic approach, em phasizing the recognition of bounding discontinuities (i.e, erosion su rfaces and marine flooding surfaces), is used to subdivide the Early P ermian stratigraphy into facies successions. Three types of succession can be identified and record changes in the relative influence of all ocyclic controls such as basin tectonics, sediment supply and glacio-e ustatic sea level variation. Together, sedimentological and allostrati graphic data allow reconstruction of the depositional history of the s outh-western margin of the Sydney Basin. Initial marine sedimentation, characterized by sediment gravity flows and storm-deposited sandstone s of the lower Wasp Head Formation, occurred adjacent to a faulted bas in margin. Overlying successions within the upper Wasp Head, Pebbley B each and Snapper Point Formations, record aggradation in inner to oute r shelf settings along a storm-and glacially influenced continental ma rgin. Tectonic subsidence and basin flooding is recorded by deeper wat er turbidites of the Wandrawandian Siltstone.