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"The basic story had been worked out earlier by others, but our results have significantly refined the timing and duration of the 'event,' which is more of a transition actually," Chamberlain explains."With all the discussion of climate change in the present day, understanding how Earth responded and the effects on the atmosphere in the past may help us predict the future." Chamberlain points to a Wyoming connection in this research."It helps us understand the evolution of Earth and Earth's atmosphere, and evolution of life, for that matter." Chamberlain's contribution focuses on igneous rocks exposed in South Africa that record the existence of equatorial glaciers and contain chemical indicators for the rise of atmospheric oxygen.
"Isotopic dating of the Ongeluk large igneous province, South Africa, revealed that the first Paleoproterozoic global glaciation and the first significant step change in atmospheric oxygenation likely occurred between 2,460 and 2,426 million years ago, approximately 100 million years earlier than previous estimates," says Kevin Chamberlain, a UW research professor in the Department of Geology and Geophysics.
"The fact that these sediments were at the equator at 2.45 billion years ago comes from the paleomagnetic data from associated igneous rocks," Chamberlain says.
In the beginning, planet Earth was a very inhospitable place with no oxygen and only single-celled bacteria as inhabitants.
At 2.31 Ga, the first marine sulfate evaporites were deposited contemporaneously with C-enriched carbonates, indicating a direct link between perturbations of the carbon and sulfur cycles and rising atmospheric oxygen.
The appearance of “red beds” and oxidized palesols after the third glaciation signals a major increase in atmospheric oxygen levels, which culminated with the fourth glaciation between 2.26 and 2.22 Ga, after which the atmosphere remained irreversibly oxygenated.