Paléoprotérozoïque

The Paléoprotérozoïque is the first era of the Protérozoïque. It extends from -2.500 to -1.600 My. It at that time that the rate of oxygen increased, is produced by Cyanobactérie S.

Subdivisions

Four systems or periods constitute Paléoprotérozoïque:

the Sidérien (from -2.500 to -2.300 My): Glaciation and chemical conversion of the oceans;
the Rhyacien (from -2.300 to -2.050 My);
the Orosirien (from -2.050 to -1.800 My);
the Stathérien (from -1.800 to -1.600 My).

Major events

The significant growth of the rate of oxygen in the atmosphere poisoned the majority of forms of life of this time. Indeed, these were Anaérobique S and did not resist the increase in the oxygen rate. The only survivors are those which resist the oxidizing effects of oxygen, or pass the greatest part or the totality of their life cycle in a free environment of its presence. One speaks thus about Catastrophe of oxygen.

American scientists recently highlighted an oxygen content quite higher than that awaited. At that time, indeed, the terrestrial atmosphere, supposed one, was still very low in oxygen, as it had always been since the beginning of the history of the Earth there is 4,56 billion years. It is known that, brutally, between 2,4 and 2,3 billion years behind, the oxygen concentration quickly increased, reaching the 21% current.

See too

geological Time scale

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