Foraminiferal boron isotope ratios as a proxy for surface ocean pH over the past 21 Myr (original) (raw)

Nature volume 363, pages 149–151 (1993)Cite this article

Abstract

THE pH of the surface ocean is a sensitive function of its alkalinity and total inorganic carbon concentration, properties which also control the partial pressure of atmospheric carbon dioxide17. Thus, an accurate proxy for past ocean pH could yield information about variations in atmospheric CO2. Recently, it has been suggested that the boron isotopic composition of foraminiferal tests depends on the pH of sea water as well as its isotopic composition1,2. Here we present boron isotope and elemental data for sedimentary pore fluids and isotope data for bulk foraminiferal samples from a deep-sea sediment core. The composition of the pore waters implies that sea water boron concentrations and isotopic composition have been constant during the past 21 Myr, allowing us to reconstruct past ocean pH directly from the foraminiferal isotope data. We find that 21 Myr ago, surface ocean pH was only 7.4 ±0.2, but it then increased to 8.2 ±0.2 (roughly the present value) about 7.5 Myr ago. This is consistent with suggestions3–5 that atmospheric CO2 concentrations may have been much higher 21 Myr ago than today.

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References

  1. Vengosh, A. et al. Geochim. cosmochim. Acta 55, 1689–1696 (1991).
    Article ADS CAS Google Scholar
  2. Hemming, N. G. & Hanson, G. N. Geochim. cosmochim. Acta 56, 537–544 (1992).
    Article ADS CAS Google Scholar
  3. Popp, B. N., Takigiku, R., Hayes, J. M., Louda, J. W. & Baker, E. W. Am. J. Sci. 289, 436–454 (1989).
    Article ADS CAS Google Scholar
  4. Cerling, T. Am. J. Sci. 291, 377–400 (1991).
    Article ADS CAS Google Scholar
  5. Arthur, M. et al. Eos, 259, 166 (1991).
    Google Scholar
  6. Kroenke, L. W. et al. Proc. ODP Init. Rep. 130, 101–176 (Ocean Drilling Program, 1991).
    Google Scholar
  7. Spivack, A. J., Palmer, M. R. & Edmond, J. M. Geochim. cosmochim. Acta 51, 1939–1949 (1987).
    Article ADS CAS Google Scholar
  8. Berner, R. A. Early Diagenesis. 241 (Princeton Univ. Press, Princeton, New Jersey, 1980).
    Google Scholar
  9. McDuff, R. E. Geochim. cosmochim. Acta 45, 1705–1714 (1981).
    Article ADS CAS Google Scholar
  10. Delaney, M. L. et al. Proc. ODP Init. Rep. 130, 549–552 (Ocean Drilling Program, 1991).
    Google Scholar
  11. McDuff, R. E. & Gieskes, J. M. Earth planet. Sci. Lett. 33, 1–10 (1976).
    Article ADS CAS Google Scholar
  12. Spivack, A. J. & Edmond, J. M. Geochim. cosmochim. Acta 51, 1033–1043 (1987).
    Article ADS CAS Google Scholar
  13. You, C.-F., Spivack, A. J., Smith, H. J. & Gieskes, J. M. Geology (in the press).
  14. Spivack, A. J. thesis, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution (1986).
  15. Kakihana, H. et al. Bull. chem. Soc. Jpn 50, 158–163 (1977).
    Article CAS Google Scholar
  16. Palmer, M. R., Spivack, A. J. & Edmond, J. M. Geochim. cosmochim. Acta 51, 2319–2323 (1987).
    Article ADS CAS Google Scholar
  17. Broecker, W. S. & Peng, T.-H. Tracers in the Sea (Lamont-Doherty Geological Observatory, Palisades, New York, 1982).
    Google Scholar
  18. Berner, R. A., Lasaga, A. C. & Garrels, R. M. Am. J. Sci. 283, 641–683 (1983).
    Article ADS CAS Google Scholar
  19. Raymo, M. E. & Ruddiman, W. F. Nature 359, 117–122 (1992).
    Article ADS CAS Google Scholar
  20. Caldeira, K., Arthur, M. A., Berner, R. A. & Lasaga, A. C. Nature 361, 123 (1993).
    Article ADS Google Scholar
  21. L. M. Francois & Walker, J. C. G. Am. J. Sci. 292, 81–135 (1992).
    Article ADS CAS Google Scholar
  22. Manheim, F. T. & Sayles, F. L. The Sea, Vol. 5, 527–568 (Wiley Interscience, New York, (1974).
    Google Scholar
  23. Grinstead, R. R. & Snider, S. Analyst 92, 532–533 (1967).
    Article ADS CAS Google Scholar

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  1. Scripps Institution of Oceanography, University of California, San Diego, 9500 Oilman Drive, La Jolla, California, 92093, USA
    Arthur J. Spivack, Chen-Feng You & H. Jesse Smith

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  1. Arthur J. Spivack
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  2. Chen-Feng You
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  3. H. Jesse Smith
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Spivack, A., You, CF. & Smith, H. Foraminiferal boron isotope ratios as a proxy for surface ocean pH over the past 21 Myr.Nature 363, 149–151 (1993). https://doi.org/10.1038/363149a0

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