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Science 15 August 1997:
Vol. 277. no. 5328, pp. 913 - 918
DOI: 10.1126/science.277.5328.913
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Research Articles

Climate and Ocean Dynamics and the Lead Isotopic Records in Pacific Ferromanganese Crusts

John N. Christensen, Alex N. Halliday, Linda V. Godfrey, James R. Hein, David K. Rea

As hydrogenous iron-manganese crusts grow, at rates of millimeters per million years, they record changes in the lead isotopic composition of ambient seawater. Time-resolved lead isotopic data for cut slabs of two central Pacific iron-manganese crusts that have been growing since about 50 million years ago were measured in situ by laser ablation, multiple-collector, inductively coupled plasma mass spectrometry. The lead isotopic compositions have remained remarkably uniform over the past 30 million years, but the record of small variations corresponds with other paleoceanographic indicators of climate change, including weathering and glaciation. This implies that despite the short residence time of lead in the oceans, global mechanisms may influence lead isotopic compositions in the central Pacific, far from continental inputs, because of changes in weathering, ocean circulation, and degree of mixing. Thus lead isotopic data could be used to probe climate-driven changes in ocean circulation through time.

J. N. Christensen, A. N. Halliday, and D. K. Rea are at the Department of Geological Sciences, University of Michigan, 2534 C. C. Little Building, Ann Arbor, MI 48109, USA. L. V. Godfrey is at the Department of Geological Sciences, Cornell University, Ithaca, NY 14853, USA. J. R. Hein is with the U.S. Geological Survey, 345 Middlefield Road, MS999, Menlo Park, CA 94025, USA.

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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X. Zhu, R. K. O'Nions, Y. Guo, and B. C. Reynolds (2000)
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Hafnium Isotope Stratigraphy of Ferromanganese Crusts.
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Oceanic minerals: Their origin, nature of their environment, and significance.
M. Kastner (1999)
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