A carbon isotope challenge to the snowball Earth

P. Sansjofre, M. Ader, R. I.F. Trindade, M. Elie, James Lyons, P. Cartigny, A. C.R. Nogueira

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Abstract

The snowball Earth hypothesis postulates that the planet was entirely covered by ice for millions of years in the Neoproterozoic era, in a self-enhanced glaciation caused by the high albedo of the ice-covered planet. In a hard-snowball picture, the subsequent rapid unfreezing resulted from an ultra-greenhouse event attributed to the buildup of volcanic carbon dioxide (CO2) during glaciation. High partial pressures of atmospheric CO2 (pco2; from 20,000 to 90,000 p.p.m.v.) in the aftermath of the Marinoan glaciation (∼635 Myr ago) have been inferred from both boron and triple oxygen isotopes. These pco2 values are 50 to 225 times higher than present-day levels. Here, we re-evaluate these estimates using paired carbon isotopic data for carbonate layers that cap Neoproterozoic glacial deposits and are considered to record post-glacial sea level rise. The new data reported here for Brazilian cap carbonates, together with previous ones for time-equivalent units, provide pco2 estimates lower than 3,200 p.p.m.v.-and possibly as low as the current value of ∼400 p.p.m.v. Our new constraint, and our re-interpretation of the boron and triple oxygen isotope data, provide a completely different picture of the late Neoproterozoic environment, with low atmospheric concentrations of carbon dioxide and oxygen that are inconsistent with a hard-snowball Earth.

Original languageEnglish (US)
Pages (from-to)93-96
Number of pages4
JournalNature
Volume478
Issue number7367
DOIs
StatePublished - Oct 6 2011
Externally publishedYes

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Sansjofre, P., Ader, M., Trindade, R. I. F., Elie, M., Lyons, J., Cartigny, P., & Nogueira, A. C. R. (2011). A carbon isotope challenge to the snowball Earth. Nature, 478(7367), 93-96. https://doi.org/10.1038/nature10499