Census-based estimates of Mediterranean Oligocene–Miocene reef carbonate production

Census-based approaches to reefal carbonate budgets are increasingly being used to project the near-future fate of tropical coral reefs. Some of the census parameters are difficult to achieve in fossil reef systems, which may be the reason why no census-based estimates of fossil reef carbonate production have been published until now. Here, we apply a census-based estimate of gross carbonate production in two reef systems from southeastern Italy to (1) test if reasonable estimates are possible and (2) assess the variability of carbonate production rates over time and reef environment. We confirm that estimates of late Oligocene and late Miocene reef gross carbonate production are within the range of modern coral reefs with the late Oligocene reef front showing the greatest carbonate production (6.1 ± 1.3 kg CaCO3 m−2 year−1) and the late Miocene reef front exhibiting the lowest production (1.7 ± 0.5 kg CaCO3 m−2 year−1). The decline of reef carbonate production from the Oligocene to the Miocene is accompanied by a decline of reef builder biodiversity but driven by the lower coral cover and coral growth rates in the Miocene. The decline of reefal carbonate production may be related to late Cenozoic cooling.