SULFUR ISOTOPIC COMPOSITION OF CENOZOIC SEAWATER SULFATE

A continuous seawater sulfate sulfur isotope curve for the Cenozoic wi th a resolution of similar to 1 million years was generated using mari ne barite, The sulfur isotopic composition decreased from 19 to 17 per mil between 65 and 55 million years ago, increased abruptly from 17 t o 22 per mil between 55 and 45 million years ago, remained nearly cons tant from 35 to similar to 2 million years ago, and has decreased by 0 .8 per mil during the past 2 million years. A comparison between seawa ter sulfate and marine carbonate carbon isotope records reveals no cle ar systematic coupling between the sulfur and carbon cycles over one t o several millions of years, indicating that changes in the burial rat e of pyrite sulfur and organic carbon did not singularly control the a tmospheric oxygen content over short time intervals in the Cenozoic. T his finding has implications for the modeling of controls on atmospher ic oxygen concentration.