Protérozoïque

On the geological time scale, the Protérozoïque is the last éon Précambrien. It precedes the complex appearance of forms of life on Ground. It only covers with him more half of time of existence of planet, between the Archéen and the Phanérozoïque. Divided into three era S, it is marked by several relatively well-known precise events Paléontologue S and Géologue S.

Classically, this éon finishes at the beginning of the Cambrien, as from the moment when the first fossils of animals known under the names of Trilobite S appear. In second half of the 20th century of the fossils of trilobites were discovered in rocks dating from the Précambrien but the end of protérozoïque remained fixed at the beginning of the cambrien, currently towards 540 million years before the Christian era.

The events best identified are:

• the transition to a atmosphere oxygenated, which probably occurred during Mésoprotérozoïque;
• several glaciations, of which most severe occurred during Néoprotérozoïque;
• the period of the Édiacarien, where the evolution of organizations to soft body accelerates.

During this éon, the continental cores, also called shields Unintermitting with, and appeared during the Archaean , show a strong growth. At the end of Protérozoïque, the volume of the continental mass (emerged grounds) is stabilized.

Subdivisions

Three eras constitute the protérozoïque one:

• the Paléoprotérozoïque (of -2  500 with -1  600 My);
• the Mésoprotérozoïque (of -1  600 with -1  000 My);
• the Néoprotérozoïque (of -1  000 to -542 My).

See too

Related articles

• geological Time scale

External bonds

• Card on GeoWhen Database

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