Variability in sulfur isotope records of Phanerozoic seawater sulfate

Abstract

Key Points  6710 measurements of δ 34 S of sulfate in Phanerozoic sedimentary rocks were compiled and systematically updated to a consistent time scale  Records derived from evaporites, barite, and carbonate-associated sulfate are similar, but also contain dramatic short-term discrepancies  Variation created by diagenetic and depositional processes increases with age in all records, obscuring temporal trends in marine sulfate Plain Language Summary Sedimentary rocks deposited in ancient marine basins preserve a record of seawater composition. We compare the sulfur isotopic composition of three sedimentary materials that contain sulfatea major ion in seawater important for carbon and oxygen cycling. Evaporite salts, the mineral barite, and trace sulfate in limestone each reveal the same first-order trends over the last 541 million years, but also display substantial shorter order discrepancies that reflect how the materials capture and store paleooceanographic information. These discrepancies partially obscure understanding of the relationship between life, ocean chemistry, and climate.