Windward reef slopes of the Capricorn-Bunker Group, southern Great Barrier reef, are the sites of extensive submarine lithification. Both crystalline (aragonite and bladed Mg-calcite spar) and microcrystalline (micrite and peloids) cements occur within skeletal pores and chambers, whereas interskeletal cements are mainly microcrystalline. These cements are considered to be contemporaneous with reef growth and have developed in an environment characterized by slow accretion rates. Continuous precipitation of aragonite cement has, in some places, been inhibited by the formation of Mg-calcite micrite. Apparent dissolution of some of the Mg-calcite cements was observed, but the processes involved are unknown.