Australia: The Land Where Time Began

A biography of the Australian continent 

Early Oxidation - Great Oxidation Event

About 2.4 Ga the atmospheric concentrations of oxygen rose dramatically during the Great Oxidation Event. A flux of oxygen into the atmosphere about 300 My earlier is indicated by sulphur isotopes. Multiple isotopes of sulphur were measured in shale that was deposited 2.71 Ga in Ontario, Canada, by Florien Kurzweil of Westfälische Wilhelms-Universitat Münster and colleagues. The sulphur isotope values were added to a photochemical model of the Archaean atmosphere to simulate the transition from a hazy atmosphere with high levels of methane to one that was increasingly oxidative by 2.7 Ga, as the production was outpaced by the production of oxygen, thereby allowing oxygen to persist in the atmosphere, though at levels much lower than during the Great Oxidation Event about 300 My later. According to the authors of the original article there was a pronounced expansion of bacteria that were capable of producing oxygen by photosynthesis. As well as this weathering of fresh volcanic rock was enhanced which would have led to increased delivery of nutrients to the ocean that could then fuel photosynthesis.

Sources & Further reading

1. Newton, Alicia. "Atmospheric Chemistry: Early Oxidation." Nature Geosci 6, no. 4 (04//print 2013): 246-46.