Calcareous rock also refers to sediments derived near land. The carbon content is high due to life-derived sediments. The farther from land sediments fall, the less calcareous they are, usually. There are of course exceptions. Some areas can have inter bedded calcareous sediments due to storms or changes in ocean currents.
Calcareous coatings, or calcareous deposits, are mixtures of calcium carbonate and magnesium hydroxide that are deposited on cathodically protected surfaces because of the increased pH adjacent to the surface.
Calcareous ooze (also calcium carbinate) accumulates due to a higher sea elevation. The CCD or calcium carbinate compensation depth is the depth at which calcium carbinate begins to dissolve in the ocean. Anything lower than the CCD and the only thing accumulating is Siliceous ooze or red clay.