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A carbon isotope challenge to the snowball Earth

SANSJOFRE, P ; ADER, M ; TRINDADE, R. I. F ; ELIE, M ; LYONS, J ; CARTIGNY, P ; NOGUEIRA, A. C. R

Nature (London), 2011-10, Vol.478 (7367), p.93-96 [Periódico revisado por pares]

London: Nature Publishing Group

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  • Título:
    A carbon isotope challenge to the snowball Earth
  • Autor: SANSJOFRE, P ; ADER, M ; TRINDADE, R. I. F ; ELIE, M ; LYONS, J ; CARTIGNY, P ; NOGUEIRA, A. C. R
  • Assuntos: Carbon ; Carbon dioxide ; Earth sciences ; Earth, ocean, space ; Exact sciences and technology ; Geology ; Grain size ; Isotope geochemistry ; Isotope geochemistry. Geochronology ; Isotopes ; Sciences of the Universe ; Stratigraphy ; Surface water
  • É parte de: Nature (London), 2011-10, Vol.478 (7367), p.93-96
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
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  • Descrição: 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 (CO(2)) during glaciation. High partial pressures of atmospheric CO(2) (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 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.
  • Editor: London: Nature Publishing Group
  • Idioma: Inglês
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