A 35-million-year record of seawater stable Sr isotopes reveals a fluctuating global carbon cycle
Un enregistrement de 35 millions d'années des isotopes stables de Sr de l'eau de mer révèle un cycle global fluctuant du carbone
Paytan, Adina ; Griffith, Elizabeth M. ; Hain, Mathis P. ; Wallmann, Klaus ; Eisenhauer, Anton ; Ridgwell, Andrew
<br>Changes in the concentration and isotopic composition of the major constituents in seawater reflect changes in their sources and sinks. Because many of the processes controlling these sources and sinks are tied to the cycling of carbon, such records can provide insights into what drives past changes in atmospheric carbon dioxide and climate. Here, we present a stable strontium (Sr) isotope record derived from pelagic marine barite. Our ?88/86Sr record exhibits a complex pattern, first declining between 35 and 15 million years ago (Ma), then increasing from 15 to 5 Ma, before declining again from ~5 Ma to the present. Numerical modeling reveals that the associated fluctuations in seawater Sr concentrations are about ±25% relative to present-day seawater. We interpret the ?88/86Sr data as reflecting changes in the mineralogy and burial location of biogenic carbonates.<br></p>
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