Fig. 1.

Different model predictions for the burial proportion of pyrite sulfur f_py into marine sediments through most of Phanerozoic time. All model results are derived from the isotopic compositions of marine sulfate and pyrite sulfur through time as shown in Fig. 2, but with different assumptions. The δ_in-constrained mass balance model is determined by assuming that the sulfur input flux j_in and its isotopic composition δ_in have remained constant through time. The “j_e-constrained mass balance” model results have been computed with constraints on the burial rates of evaporite sulfur from a macrostratigraphic database, and with various assumptions about the burial rates of pyrite sulfur j_py through time. In this model, the isotopic composition of input sulfur δ_in is adjusted to achieve mass balance (Fig. 2). The results for both model outputs are redrawn from ref. 12 with permission from AAAS. Also shown are calculations assuming δ_in-values of between 11 and 12 per mil for the time window of 160–220 Ma as indicated by the coal sulfur isotope record in coal as shown in Fig. 2.