The skeletal banding observed in vertical cross-sections of two species of coral, Montastrea annularis from Jamaica and Diploria labrynthiformis from Bermuda, has been confirmed to be annual by ingrowth of 228Th towards radioactive equilibrium with 228Ra taken up from seawater. In addition the Bermuda coral is shown to have incorporated 210Pb at essentially constant specific activity over at least the last thirty years.

The individual annual patterns of growth banding in a suite of specimens of D. Labrynthiformis from Bermuda are shown to be correlative. The mass of CaCO3 accumulated each year is positively correlated with the band width for the corresponding year.