Por um entendimento quantitativo do ciclo de carbono no período final do neoproterozoico

terça-feira, abril 05, 2011

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) 


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


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. 

This article contains supporting information online at 

Freely available online through the PNAS open access option.