Secular Control of Saturation State on Carbonate Precipitation Rates in The Oceans: New Insights from Ancient Carbonate Platforms

We estimate the mass of carbonate precipitated per unit area per unit time (G) for 9 carbonate platforms ranging from the Devonian to the Miocene in age, characterized by different dominant carbonate factories. This estimate, despite the caveats due to the intrinsic incompleteness of the sedimentary record, is more comparable to the precipitation rates calculated for modern platforms, than accumulation rates expressed as thickness per unit time. We compare such G estimates to modeled saturation state (Ω) with respect to carbonate and seawater temperatures in the geological time and try to explore the relative influence of these two factors on carbonate precipitation by utilizing a Generalized Linear Model (GLM) for the analysis of a comprehensive dataset of 250 observations including fossil examples, modern case studies, and laboratory experiments. Results suggest a dominance of Ω in controlling carbonate precipitation rates and that the dependance between G and Ω in modern and fossil case studies can be well fit by logarithmic relationships that do not appear to differ significantly. These findings seem to imply that Ω - at least in shallow water environments - exerts a significant control on biocalcification, regardless the dominant calcification mode. This not only sheds light on the role of Ω in driving calcification process in the oceans through geological time, but may foster future research into understanding the modification of carbonate-producing systems under climate change.