text: Calcareous sediments are typically deposited in shallow water closer to land, as marine organisms that precipitate calcium carbonate primarily reside within shallow water ecosystems due to an inability to precipitate calcium carbonate at depth (see carbonate compensation depth). Generally speaking, the farther from land sediments fall, the less calcareous they are, and deviations from this expectation arise if (a) the ocean floor is shallower than the CCD or (b) storms/ocean currents transport calcareous sediments away from their origin point, leading to the interbedding of calcareous sediments in alternative locations.
  An additional form of calcareous marine sediment consists of calcareous ooze, which is a form of calcium carbonate sediment that consists of >30% biogenous material predominantly consisting of organisms such as coccolithophores and foraminifera. These oozes form slowly under low-energy environments, and necessitate higher seawater saturation states or a deeper CCD (see supersaturation and precipitation vs. undersaturation and dissolution). Therefore, in shallow CCD conditions (i.e., undersaturation of calcium carbonate at depth), stable, non-calcareous sediments such as siliceous ooze or pelagic red clay will prevail in marine sediment records.