A carbon isotope challenge to the snowball Earth | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  A carbon isotope challenge to the snowball Earth

Publication Type:

Journal Article

Source:

Nature, Volume 478, Issue 7367 (2011)

ISBN:

0028-0836

Accession Number:

WOS:000295575400041

URL:

http://www.nature.com/nature/journal/v478/n7367/full/nature10499.html

Keywords:

UMR 7154 ; Physico-chimie des Fluides Géologiques ; Geology and geophysics

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 glaciation1. High partial pressures of atmospheric CO2 ( ; 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 isotopes2, 3. These 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 rise1. The new data reported here for Brazilian cap carbonates, together with previous ones for time-equivalent units4, 5, 6, 7, 8, provide 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.

Notes:

Times Cited: 1