Temperature and salinity variations in surface seawater off the coast of eastern Tasmania are caused by influxes of different waters, the relative proportions of which vary throughout the year. The Tasmanian carbonates consist mainly of reworked calcitic fauna with variable intragranular CaCO 3 cements. The δ 1 8 O and δ 1 3 C isotope fields of eastern Tasmanian bulk carbonates, bryozoans, benthic foraminifera and brachiopods overlap and all grade into the field typical of deep-sea carbonates. The trend lines of seafloor diagenesis and upwelling water past through fields of temperate skeletons and bulk carbonates because they are in equilibrium with mixed seawaters having δ 1 8 O values of -1 to 0‰ and δ 1 3 C values of 0 to 1‰. They form at a slower rate than tropical water carbonates.