A revised seawater sulfate S-isotope curve for the Eocene

• Published in: Chemical geology Vol. 532; p. 119382
• Main Authors: Yao, Weiqi, Paytan, Adina, Griffith, Elizabeth M., Martínez-Ruiz, Francisca, Markovic, Stefan, Wortmann, Ulrich G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20.01.2020
• Subjects: Barite; Marine diagenesis; Sulfate; Sulfur isotope; Marine diagenesis; Sulfate; Barite; Sulfur isotope
• ISSN: 0009-2541; 1872-6836
• DOI: 10.1016/j.chemgeo.2019.119382

The sulfur isotope ratio (δ34S) recorded in marine barite is commonly used to estimate secular changes in the sulfur isotopic composition of seawater sulfate (δ34SSO4) throughout Earth's history. The Cenozoic record demonstrates a drastic 5‰ increase in seawater δ34SSO4 during the Early Eocene. However, the gradient of this excursion is based on only a few data points. Taking advantage of a much improved biostratigraphic framework, we redefine the Eocene δ34SSO4 data with a new high-resolution barite based δ34S record between 60 and 30 Ma. Our results show that the rise of δ34SSO4 starts about 3 million years later (~53 Ma) and lasts about 9 million years longer (until 38 Ma) than previously depicted. As such, the gradient of the δ34S curve is ~0.4‰/Myr. The radiogenic strontium isotopic ratio in barite suggests that some of the samples used for the original barite record are affected by diagenetic alteration. •Significantly improved data density for the most prominent feature of the Cenozoic marine S-isotope record, the 5‰ rise during the Eocene.•The duration of the S-isotope rise increases from 9 to 15 million years (38-53 vs. 47-56 Ma).•S and Sr isotope ratios recorded in barite are sensitive to cryptic diagenesis that is not detectable by SEM imaging.•Marine barite and CAS data track each other with astounding fidelity, recording the actual seawater S-isotope ratio.