text: δS records have been used to infer changes in seawater sulfate concentrations. Because the δS values of carbonate-associated sulfate are thought to be sensitive to seawater sulfate levels, these measurements have been used to reconstruct the history of seawater sulfate. δS values of pyrite have also been applied to reconstruct the concentration of seawater sulfate, based on expected biological fractionations at low sulfate concentrations. Both of these methods rely on assumptions about the depositional environment or the biological community, creating some uncertainty in the resulting reconstructions.