Nordic Center for Earth Evolution and Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, DK-1350 København K, Denmark.
Proc Natl Acad Sci U S A. 2011 Apr 5;108(14):5542-7. doi: 10.1073/pnas.1101755108. Epub 2011 Mar 21.
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.
地球表面的碳和氧循环密切相关，其中有机碳在沉积物中的埋藏代表了向地表环境提供氧气的来源。这种耦合通常通过有机碳和无机碳的同位素记录来量化。然而，在新元古代末期，即动物首次进化的时期，经历了与我们对碳循环和碳-氧耦合的正常理解不符的剧烈同位素波动。我们使用一个新的碳循环模型来解释这些波动，并证明碳酸盐和有机碳同位素记录的所有主要特征都可以用缺氧富溶解有机碳的海洋中甲烷水合物的释放来解释，释放到的大气中氧气含量远低于今天的水平。
