Towards a quantitative understanding of the late Neoproterozoic carbon cycle
Author Affiliations
aNordic Center for Earth Evolution (NordCEE) and Department of Geography and Geology, University of Copenhagen, Øster Voldgade, 10, DK-1350 København K., Denmark; and
bNordic Center for Earth Evolution (NordCEE) and Institute of Biology, University of Southern Denmark, Campusvej, 55, DK-5230 Odense M, Denmark
Contributed by Donald E. Canfield, February 1, 2011 (sent for review November 25, 2010)
Abstract
The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which do not conform to our normal understanding of the carbon cycle and carbon-oxygen coupling. We interpret these fluctuations with a new carbon cycle model and demonstrate that all of the main features of the carbonate and organic carbon isotope record can be explained by the release of methane hydrates from an anoxic dissolved organic carbon-rich ocean into an atmosphere containing oxygen levels considerably less than today.
carbon isotope excursion carbon monoxide Shuram-Wonoka anomaly earth evolution atmospheric chemistry
Footnotes
1To whom correspondence may be addressed. E-mail: cjb@geo.ku.dk or dec@biology.sdu.dk.
Author contributions: C.J.B. and D.E.C. designed research; C.J.B. and D.E.C. performed research; C.J.B. and D.E.C. analyzed data; and C.J.B. and D.E.C. wrote the paper.
The authors declare no conflict of interest.
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