Great Oxygenation Period (~2.4 BYA)

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A Great Oxygenation Period (~2.4 BYA) was an mass extinction period and transition event commenced by the appearance of a photosynthesizing life forms.



References

2014

  • (Wikipedia, 2014) ⇒ http://en.wikipedia.org/wiki/Great_Oxygenation_Event Retrieved:2014-2-22.
    • The Great Oxygenation Event (GOE), also called the Oxygen Catastrophe, Oxygen Crisis, the Oxygen Revolution, or Great Oxidation, was the biologically induced appearance of free oxygen (O2) in Earth's atmosphere. Geological, isotopic, and chemical evidence suggest this major environmental change happened around 2.4 billion years ago (2.4 Ga).[1]

       Cyanobacteria, which appeared about 200 million years before the GOE,[2] began producing oxygen by photosynthesis. Before the GOE, any free oxygen they produced was chemically captured by dissolved iron or organic matter. The GOE was the point when these oxygen sinks became saturated and could not capture all of the oxygen that was produced by cyanobacterial photosynthesis. After the GOE the excess free oxygen started to accumulate in the atmosphere.

      Free oxygen is toxic to obligate anaerobic organisms and the rising concentrations may have wiped out most of the Earth's anaerobic inhabitants at the time. Cyanobacteria were therefore responsible for one of the most significant extinction events in Earth's history. Additionally the free oxygen reacted with the atmospheric methane, a greenhouse gas, reducing its concentration and thereby triggering the Huronian glaciation, possibly the longest snowball Earth episode. Free oxygen has been an important constituent of the atmosphere ever since.[3]

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  2. Flannery, D. T.; R.M. Walter (2012). "Archean tufted microbial mats and the Great Oxidation Event: new insights into an ancient problem". Australian Journal of Earth Sciences 59 (1): 1–11. Bibcode 2012AuJES..59....1F. doi:10.1080/08120099.2011.607849. 
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2014

  • Noah J. Planavsky, Christopher T. Reinhard, Xiangli Wang, Danielle Thomson, Peter McGoldrick, Robert H. Rainbird, Thomas Johnson, Woodward W. Fischer, and Timothy W. Lyons. (2014). “Low Mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals". In: Science, 346(6209) doi:10.1126/science.1258410
    • QUOTE: The oxygenation of Earth’s surface fundamentally altered global biogeochemical cycles and ultimately paved the way for the rise of metazoans at the end of the Proterozoic. However, current estimates for atmospheric oxygen (O2) levels during the billion years leading up to this time vary widely. On the basis of chromium (Cr) isotope data from a suite of Proterozoic sediments from China, Australia, and North America, interpreted in the context of data from similar depositional environments from Phanerozoic time, we find evidence for inhibited oxidation of Cr at Earth’s surface in the mid-Proterozoic (1.8 to 0.8 billion years ago). These data suggest that atmospheric O2 levels were at most 0.1% of present atmospheric levels. Direct evidence for such low O2 concentrations in the Proterozoic helps explain the late emergence and diversification of metazoans.