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Science 6 July 1990:
Vol. 249. no. 4964, pp. 51 - 55
DOI: 10.1126/science.249.4964.51
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Articles

Seawater Strontium Isotopic Variations from 2.5 Million Years Ago to the Present

R. C. Capo 1 and D. J. DePaolo 2

1 Berkeley Center for Isotope Geochemistry, Department of Geology and Geophysics, University of California and Earth Sciênce Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720, and Department of Earth and Space Sciences, University of California, Los Angeles, CA 90024
2 Berkeley Center for Isotope Geochemistry, Department of Geology and Geophysics, University of California, and Earth Science Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720

Measurements of marine carbonate samples indicate that during the past 2.5 million years the 87Sr/86Sr ratio of seawater has increased by 14 x 10-5. The high average rate of increase of 87Sr/86Sr indicates that continental weathering rates were exceptionally high. Nonuniformity in the rate of increase suggests that weathering rates fluctuated by as much as ±30 percent of present-day values. Some of the observed shifts in weathering rates are contemporaneous with climatic changes inferred from records of oxygen isotopes and carbonate preservation in deep sea sediments.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Science. ISSN 0036-8075 (print), 1095-9203 (online)