Friday, January 05, 2007

O2 & The Rise of Life

Late-Neoproterozoic Deep-Ocean Oxygenation and the Rise of Animal Life. 2007. D. E. Canfield et al. Science 315: 92–95.
A record based on iron species in minerals implies that the deep ocean only became oxygenated after the last major Precambrian glaciation, just before the rise of metazoans.
Abstract: Because animals require oxygen, an increase in late-Neoproterozoic oxygen concentrations has been suggested as a stimulus for their evolution. The iron content of deep-sea sediments shows that the deep ocean was anoxic and ferruginous before and during the Gaskiers glaciation 580 million years ago and that it became oxic afterward. The first known members of the Ediacara biota arose shortly after the Gaskiers glaciation, suggesting a causal link between their evolution and this oxygenation event. A prolonged stable oxic environment may have permitted the emergence of bilateral motile animals some 25 million years later.