THE “CARBONATE FACTORY” REVISITED: A REEXAMINATION OF SEDIMENT PRODUCTION FUNCTIONS USED TO MODEL DEPOSITION ON CARBONATE PLATFORMS

There are two models of sediment production on carbonate shelves that are widely used in computer models of carbonate platform sedimentation: (1) production varying with depth, and (2) production as a function of depth and distance from the platform margin. We have recalculated carbonate production on Great Bahama Bank west and northwest of Andros Island using Broecker and Takahashi's (1966) pioneering geochemical study. In the calculations, residence time and depth were used to calculate yearly carbonate production based on equilibrium thermodynamics of CaCO₃ loss from water over the banks. Whereas Broecker and Takahashi assumed a uniform depth of 4.5 m in their work, we used realistic depths and residence times interpolated over the bank. Our results suggest that sediment production is on the order of 4 - 5 kg/m2/y on the bank margins and that production rapidly drops off into the platform, approaching zero in the shallowest, innermost parts of the platform. Thus, for a large platform such as Great Bahama Bank with long residence times, the shallowest areas of the platform become sinks, not sources, of sediment contrary to the sediment production regimes of most computer models of carbonate platform sedimentation.