carbonate compensation depth

Carbonate compensation depth (CCD) is a level in the oceans below which the rate of supply of calcium carbonate (calcite and aragonite) equals the rate of dissolution, such that no calcium carbonate is preserved. Calcium carbonate is essentially insoluble in sea surface waters today, shells of dead calcareous plankton sinking to deeper waters are practically unaltered until reaching the lysocline where the solubility increases dramatically, by the time the CCD is reached all calcium carbonate has dissolved.Calcareous plankton and sediment particles can be found in the water column above CCD and, if the sea bed is above the CCD, bottom sediments can consist of calcareous sediments called calcareous ooze which is essentially a type of limestone or chalk. If the sea bed is below the CCD tiny shells of CaCO3 will dissolve before reaching this level so there will be no carbonate sediment.
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