Extended Data Fig. 1: Open-system diagenetic evolution fluid–rock interaction model.

a–c, Fluid–rock alteration models showing the relative order of alteration for CAP, CAS, Fe, Mn, IO₃, δ¹³C, δ³⁴S_CAS, δ²³⁸U, δ^44/40Ca and ⁸⁷Sr/⁸⁶Sr. Several curves are presented for δ¹³C and δ³⁴S_CAS under varying DIC and sulfate concentrations in the diagenetic fluid. d, Fluid–rock alteration model showing the predicted trends between CAP and δ¹³C. Grey points are CAP and δ¹³C data from all study sections. Solid and dashed lines represent different pore-water DIC concentration and δ¹³C compositions. Dotted line is trendline through data points with R value. See Supplementary Information for model description. Yellow stars mark the point at which 50% of the CAP value has been altered. Red stars mark the point at which 50% of the element of interest has been altered.