Donald E. Canfield of the Nordic Center for Earth Evolution at the Institute of Biology at the University of Southern Denmark and eight of France’s top geologists and geochemists have proposed a new explanation of the variability of oxygen levels before and after the Great Oxidation Event in the Sept. 30, 2013, edition of the Proceedings of the National Academy of Sciences.
The new results are based on core samples taken from ancient ocean sediments in the Republic of Gabon that date to periods before and after the Great Oxidation Event. These samples are one of the few physical realities that theories about events leading up to and after the Great Oxidation Event can be based on.
The earliest samples date from 2.15 billion years ago and show a high level of oxygenation in deep water. The youngest layers date from 2.08 billion years ago and show lower levels of oxygen than exist in the present day. The depletion of oxygen is attributed to high levels of carbon and iron. The oxygen reacted with both carbon and iron to form oxides that can be found in the sediments. The carbon came from organic matter that was probably plant based. The oxygen depletion lasted 200 million years.
The researchers conclude that oxygenation on Earth has been and probably will continue to be a dynamic system based on basic chemistry.