ACCUMULATION RATES OF CARBONATE PLATFORMS

The growth potential of carbonate platforms, i.e., the maximum rate at which they can aggrade vertically, is difficult to assess. To estimate the growth potential from the conservative side and search for variations with time, we have compiled published accumulation rates from the Phanerozoic. Accumulation rates vary in a pattern, with maximum rates up to 200 m/Ma or more (not corrected for compaction) in the late Devonian, Permian, late Triassic, late Jurassic and mid-Cretaceous, separated by intervals of reduced rates (e.g., Carboniferous, early Jurassic and late Cretaceous). The most dramatic drop occurs at the Permo-Triassic boundary, after which there is no documented platform growth. This pattern resembles the evolutionary rhythm of bloom and demise of reefs and reef-builders. The observed maximum accumulation rate of 200 m/Ma (over 10(6)-10(7) yr), is probably imposed by the maximum rate of long-term relative sea level rise on passive margins, the most favorable site for carbonate platform development. When the trend of decreasing rates with increasing interval duration was corrected for by normalizing all the rates to a 1 Ma interval duration, these variations remained. Biological factors may explain much of the observed variations.