Possible roles of pH, temperature, and partial dissolution in determining boron concentration and isotopic composition in planktonic foraminifera

Paleoceanography - Tập 18 Số 4 - 2003
Michael W. Wara1, M. L. Delaney2, Thomas D. Bullen3, Ana Christina Ravelo2
1Department of Ocean Sciences, University of California, Santa Cruz, California, USA
2Department of Ocean Sciences and Institute of Marine Sciences, University of California, Santa Cruz, California, USA
3U.S. Geological Survey, Menlo Park, California USA

Tóm tắt

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.

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Paleoceanography

Tập 18 Số 4

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