OCEAN/ATMOSPHERE HISTORY AND CARBONATE PRECIPITATION RATES: A SOLUTION TO THE “DOLOMITE PROBLEM”?

Abstract

this paper, we consider how long-term tectonic conditions and their effecl on the surface environment of tlie earth interacted with the global carbonate cycle during tlie liothouse (greenhouscj-icehouse trailsition of the past 100 million years. Using the recalculated outl~ut of tlie Berncr, Lasaga, and Garrels (BLAG) geochemical liiodel as a template (Berncr et al., 1983; Lasaga et nl., 1985), we computed changes in seawater carbonate chemistry for tlie past 100 m.y. Experimenlal dolomile and calcite precipitation rate data as a function of environmental conditions were used lo calculate the ratio of rates of doloiiiitc ant1 calcite precipilatioli rates during this period of time. We conclude from these model calculations that the observed decrease in the ratio of dololiiite to calcite ill sedimentary carbonates deposited since tlic Late Cretaceous transgression was a ~.esult of changes in tlie ocean s;~turatioll state with respect to carbonate minerals and global sul-face temperature. Thus, the solutiou to the c1;lssical dolomite problenl (nay lie in relatively sriiall but coupled changes in the composition and temperature of tlie atmosphere and seawater.