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Osmium isotope evidence for the regulation of atmospheric CO2 by continental weathering

Cohen, Anthony S.; Coe, Angela L.; Harding, Stephen M. and Schwark, Lorenz (2004). Osmium isotope evidence for the regulation of atmospheric CO2 by continental weathering. Geology, 32(2) pp. 157–160.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1130/G20158.1
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Abstract

The long-term stability of Earth's climate throughout the Phanerozoic stands in marked contrast to the dramatic fluctuations that have taken place on time scales as short as a few years, reflecting the high efficiency of longer-term climate regulation through negative feedbacks. A fundamental mechanism is thought to involve control of CO2 in the ocean- atmosphere system through continental weathering, although unambiguous, high-resolution data supporting this hypothesis have hitherto not been available. Organic-rich mud rocks from Yorkshire, England, which were deposited during the Toarcian oceanic anoxic event (ca. 181 Ma, Early Jurassic), contain evidence of an exceptionally large excursion in the 187Os/188Os ratio of contemporaneous seawater, from 0.4 to 1.0. The most likely explanation for this excursion is that it resulted from a transient increase in global continental weathering rates of 400%–800%. The Os isotope excursion coincided with a well-documented global 13C excursion of –6 that affected all the major biospheric reservoirs of the time. Higher mean global temperatures caused global chemical weathering rates to increase substantially, while, in turn, chemical weathering was very effective in reducing the elevated levels of atmospheric CO2 and the high temperatures to preexcursion levels.

Item Type: Journal Article
ISSN: 0091-7613
Extra Information: Some of the symbols may not have transferred correctly into this bibliographic record and/or abstract.
Academic Unit/Department: Science > Environment, Earth and Ecosystems
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 6247
Depositing User: Users 2315 not found.
Date Deposited: 19 Jan 2007
Last Modified: 02 Dec 2010 19:56
URI: http://oro.open.ac.uk/id/eprint/6247
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