Fig. 4.

Model steady states at 1,000 Ma as a function of relative solar flux. Line type shows choices for the dependency of seafloor weathering rate on atmospheric CO₂ concentration. Rates of silicate and seafloor weathering (A), relative ocean phosphate concentration (B), organic carbon burial rate (C), the fraction of carbon buried organically (D), relative atmospheric oxygen (E), and CO₂ concentrations (F). Gray vertical line denotes assumed solar flux at 1,000 Ma (38). We assume a relative terrestrial weatherability and spreading rate of 1/4 (12) and 1.83 (37), respectively.