Negative carbon isotope anomalies in carbonate rocks bracketing Neoproterozoic glacial deposits in Namibia, combined with estimates of thermal subsidence history, suggest that biological productivity in the surface ocean collapsed for millions of years. This collapse can be explained by a global glaciation (that is, a snowball Earth), which ended abruptly when subaerial volcanic outgassing raised atmospheric carbon dioxide to about 350 times the modern level. The rapid termination would have resulted in a warming of the snowball Earth to extreme greenhouse conditions. The transfer of atmospheric carbon dioxide to the ocean would result in the rapid precipitation of calcium carbonate in warm surface waters, producing the cap carbonate rocks observed globally.
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Volume 281 | Issue 5381
28 August 1998

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Received: 21 April 1998
Accepted: 21 July 1998
Published in print: 28 August 1998


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Paul F. Hoffman*
P. F. Hoffman, G. P. Halverson, D. P. Schrag, Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA. A. J. Kaufman, Department of Geology, University of Maryland, College Park, MD 20742, USA.
Alan J. Kaufman
P. F. Hoffman, G. P. Halverson, D. P. Schrag, Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA. A. J. Kaufman, Department of Geology, University of Maryland, College Park, MD 20742, USA.
Galen P. Halverson
P. F. Hoffman, G. P. Halverson, D. P. Schrag, Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA. A. J. Kaufman, Department of Geology, University of Maryland, College Park, MD 20742, USA.
Daniel P. Schrag
P. F. Hoffman, G. P. Halverson, D. P. Schrag, Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA. A. J. Kaufman, Department of Geology, University of Maryland, College Park, MD 20742, USA.


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