South Maria Ridge (34°S) is a 1500 km2submarine ridge and bank system, less than 500 m deep, slowly accumulating photic and sub‐photic, clean skeletal carbonate gravels and sands having over 80%, and generally over 95%, CaCO3, mainly calcite. Contributing factors include the negligible supply of terrigenous sediment, the availability of stable rocky substrates for colonisation by epibenthos, and the prominent upwelling of nutrient‐rich waters, stimulating organic growth. Sediments comprise fragmental remains of diverse bryozoan colonies (10–74%), with lesser amounts of mainly infaunal bivalves (2–20%), gastropods (2–10%), ahermatypic corals (0–18%), calcareous red algae (1–16%), and benthic foraminifers (3–15%), and small contributions from serpulids, barnacles, echinoids, brachiopods, sponges, and pteropods. Major species are identified. The distribution of skeletal types is controlled initially by substrate, bathymetry, and energy level, and subsequently by topographically influenced tidal flow dispersal. However, the present sediment distribution pattern has been complicated by eustatic sea level changes. Modern zones of carbonate production are centred mainly on the shallower portions of the ridge, in the vicinity of Three Kings and Middlesex Banks. Below 150–200 m depth the skeletal sediments become increasingly relict. A rough bathymetric zonation of faunal types remains, but their depths are on average 100–150 m below their modern counterparts, supporting emplacement during the low sea level of the Last (Otiran) Glaciation. The skeletal deposits are temperate‐latitude limestones in the making, with properties significantly different from their better known tropical counterparts but closely analogous to many Cenozoic limestones in New Zealand.