Tracking oxygen’s rise
SEP 11, 2009
DOI: 10.1063/PT.5.023676
Nature News : How quickly did oxygen build up in Earth’s early atmosphere? An analysis using chromium isotopes trapped in ancient ocean deposits has provided an unexpected clue.A team led by Robert Frei of the University of Copenhagen, Denmark, sampled banded iron formations—an iron-rich sedimentary rock—dating from around and in between the two main periods of intense oxygen increases. They show that oxygen snuck into surface ocean waters 2.8-2.6 billion years ago—at least 200 million years earlier than predictions based on analyses of other metal isotopes.More surprisingly, they also claim that around 1.9 billion years ago, oxygen levels actually dipped back down to almost where they were before the Great Oxidation Event, at less than 1% of today’s levels. Related Link Fluctuations in Precambrian atmospheric oxygenation recorded by chromium isotopes
© 2009 American Institute of Physics
