MIDDLE MIOCENE PALEOTOPOGRAPHY AT LITTLE BAY, NEAR MAROUBRA, NEW-SOUTH-WALES

The Little Bay Shale is a poorly consolidated buff to pale grey shale whose estuarine nature is indicated by the presence of marine dinoflag ellate cysts, microforaminiferal liners and mangrove pollen in the mic roflora and the mangrove Bruguiera in the macroflora. Palynological ev idence places it in the Triporopollenites bellus Zone of latest Early to early Late Miocene age, with Middle Miocene being the most probable . Its occurrence is restricted to a narrow valley incised into Triassi c Hawkesbury Sandstone, situated in the southeastern Sydney suburb of Little Bay. The age of the deposit corresponds broadly with the maximu m Neogene eustatic event. though eustasy was not necessarily the prime or only cause. The reconstructed drainage pattern indicates a possibl e westerly drainage and therefore a possible pre-Middle Miocene age fo r the Botany Bay Basin. Palaeobotanical and plate tectonic evidence su ggest a climatic shift since the Middle Miocene of the equivalent of a t least 11 degrees of latitude. Implied local sea-level in the Middle Miocene was + 30 m. Lateritic weathering of the Hawkesbury Sandstone i s older than the deposition of the shale.