In this paper, we consider how long-term tectonic conditions and their effect on the surface environment of the earth interacted with the global carbonate cycle during the hothouse (greenhouse)–icehouse transition of the past 100 million years. Using the recalculated output of the Berner, Lasaga, and Garrels (BLAG) geochemical model as a template (Berner et al., 1983; Lasaga et al., 1985), we computed changes in seawater carbonate chemistry for the past 100 m.y. Experimental dolomite and calcite precipitation rate data as a function of environmental conditions were used to calculate the ratio of rates of dolomite and calcite precipitation rates during this period of time. We conclude from these model calculations that the observed decrease in the ratio of dolomite to calcite in sedimentary carbonates deposited since the Late Cretaceous transgression was a result of changes in the ocean saturation state with respect to carbonate minerals and global surface temperature. Thus, the solution to the classical “dolomite problem” may lie in relatively small but coupled changes in the composition and temperature of the atmosphere and seawater.