STRATIGRAPHY AND SEDIMENTOLOGY OF THE PERMIAN TALATERANG AND SHOALHAVEN GROUPS IN THE SOUTHERNMOST SYDNEY BASIN, NEW-SOUTH-WALES

The Permian (Sakmarian-Artinskian) Talaterang and Shoalhaven Groups fo rm the basal part of the Sydney Basin succession at its southernmost o nshore extremity. A new stratigraphic model is proposed for the southe rn Sydney Basin and, although the previous group division is retained, considerable rearrangement of formations within and between the group s has been necessary as a result of recent field work. The Talaterang Group now includes the Clyde Coal Measures (incorporating the previous Pigeon House Creek Siltstone) and the Wasp Head Formation. The lower units in the overlying Shoalhaven Group are the Yadboro and Tallong Co nglomerates, Pebbley Beach Formation, Yarrunga Coal Measures and Snapp er Point Formation. Within the Talaterang Group, north-directed sedime nt dispersal in the mud-rich alluvial Clyde Coal Measures sequence and high energy east-directed debris flows in the Wasp Head Formation sug gest axial and transverse drainage related to possible north-trending extensional (rift) sub-basins similar to those in the Gunnedah and Bow en Basins. A succeeding phase of passive thermal subsidence initiated deposition of the Shoalhaven Group comprising a high energy alluvial b raidplain succession (Yadboro and Tallong Conglomerate), a fluvial to transgressive marine sandstone succession (Snapper Point Formation) an d laterally equivalent coastal and protected embayment deposits repres ented by the Yarrunga Coal Measures and Pebbley Beach Formation. An ov erall rise in relative sea-level during the deposition of the lower Sh oalhaven Group led to the fluvial facies giving way both laterally and vertically to shallow marine (Snapper Point Formation) and then the d eeper shelf facies of the Wandrawandian Siltstone.