Carbonate Lithification on the Sea Floor

Indurated Globigerina-rich sediments have been recorded from more than thirty localities on sea floors around the world, between depths of 200 and 3,500 m. Many are stained by iron and manganese minerals or are associated with manganese nodules or crusts, suggesting that such lithification occurs along profiles of sedimentational equilibrium. Samples from the eastern Mediterranean and from off Barbados, here described and illustrated with photomicrographs and electron micrographs, contain high-magnesian calcite and dolomite, and show recrystallization of the micritic matrix, as well as calcitic cavity fillings. We conclude, contrary to widespread opinion, that calcite can be precipitated chemically in seawater, and that carbonate sediments can become lithified on the sea floor.