The coral content of Quaternary reef limestones provides a useful calibration of the preserved record of modern reefs. Estimates of the percentage of corals in outcrops range from 32 to 46% for the Key Largo limestones of south Florida; 18 to 46% for Pleistocene limestones of the Kenya coast; and up to 60% for Pleistocene reef limestones of Barbados. Core borings from the Great Barrier Reef have an even wider range in the percentage of coral, with only localized areas of more than one-third massive or branched coral.

Simulated core borings made on photographs of outcrops call attention to the wide range of variations to be expected. The average standard deviation of coral percentages in simulated core borings is ± 13% as compared with percentages of their respective outcrops.

These results further support the view that percentage of coral in Quaternary reef limestones is highly variable and is often less than one-third of the total biomass. Furthermore, they give a useful baseline for comparing Quaternary and more ancient reef limestones.

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