Numerous authors have treated the CaCO₃ compensation level in deep-sea sediments as an immutable boundary fixed by temperature and pressure. Some have gone so far as to use it as a paleodepth indicator. This concept is totally invalid. Actually the depth at which calcite solution becomes important is controlled by a delicate balance between carbon supply to the ocean and carbon removal by organisms. The fact that organisms precipitate CaCO₃ from seawater far faster than it is being supplied by rivers demands that solution take place. The proportion of the sea floor bathed in calcite undersaturated water is such that the precipitate in excess of supply is returned to solution. In such a system changes in supply rate of carbon, productivity of carbonat producing organisms, and mixing regime of the oceans will upset the delicate balance between supply and demand and lead to fluctuations in the level of compensation. That such changes can occur on a short time scale is demonstrated by the fact that the compensation level was lower during glacial than during interglacial times. It is not at all surprising that the JOIDES cores show evidence of large fluctuations in this level through Tertiary time.

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