We present the first continuous records from 0 to 5 Ma (in 0.333 m.y. integrated time steps) of paired boron/calcium (B/Ca) ratios and boron isotopes (δ11B) in the planktonic foraminifera Globogerinoides sacculifer (without sacc) from a site in the western equatorial Pacific Ocean (Ocean Drilling Program Site 806). These measurements, the first made in conjunction with calcification temperature (magnesium/calcium ratios) and average shell mass measurements, indicate that pH is not the sole environmental variable controlling B in planktonic foraminiferal calcite. Our data are consistent with calcification temperature exerting a primary control on B concentration and isotopic composition in planktonic foraminifera. If so, calcification temperature must be taken into account if pH for past oceans and atmospheric pCO2 are to be estimated from B isotope measurements in foraminiferal calcite. Doing so will substantially increase the uncertainty of pH estimates. Although this work was designed as a temporal study, its results define new aspects of calibrating the δ11B paleo-pH tracer.
CITATION STYLE
Wara, M. W., Delaney, M. L., Bullen, T. D., & Ravelo, A. C. (2003). Possible roles of pH, temperature, and partial dissolution in determining boron concentration and isotopic composition in planktonic foraminifera. Paleoceanography, 18(4). https://doi.org/10.1029/2002PA000797
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