séminaire – mercredi 25 janvier 2017

atmospheric oxygenOxygen-17 and the search for the earliest direct evidence of atmospheric oxygen

Bryan Killingsworth (IUEM)

mercredi 25 janvier 2017 à 11 heures, amphi Courtois

 

 

 

The emerging view of Earth’s oxygenation is of two major increases in atmospheric oxygen, at 2.5 Gyr and 635 Myr, which were prefaced by unstable oxygen levels that changed on short (Myrs) time scales. This understanding of the history of Earth oxygenation is complicated by the use of sedimentary and geochemical proxies that are indirect. However, the possibility of direct evidence of atmospheric oxygen exists in the stable isotope oxygen-17 record in sedimentary sulfates. The way in which atmospheric oxygen-17 signals can be preserved in the sulfate record, and the search for this record around the time of the Earth’s “Great Oxygenation Event” after 2.5 Gyr will be discussed.