Néoprotérozoïque

The Néoprotérozoïque is the third and last era of the Protérozoïque. It extends from -1.000 My with -540 My. The exact terminals can vary somewhat according to the authors and the seniority of the publications. This era covers one period of time during which one finds fossils of Métazoaire S, but only of the Algue S and sponges can be recognized starting from their modern forms.

In addition, this era being the last of the Protérozoïque, it closes time known as “Précambrien S.”

Subdivisions

Three systems or periods constitute Néoprotérozoïque:

the Tonien (from -1.000 to -850 My);
the Cryogénien (from -850 to -650 My);
the Édiacarien (from -650 to -545 My).

Paleogeography

The data remain vague, but it is considered that this era is the continental object of displacement complexes. The Supercontinent Rodinia split up in probably (at least) eight distinct parts, beginning an active phase of Plate tectonics.

A glaciation severe, known as Varanger, occurs during the Cryogénien. The Banquise goes down until the equator, bringing the sphere in a state known under the name of Ground snowball . A debate susbsist as for knowing if the ice-barrier is really descended to the equator or if a free zone of sea remained there.

Biotopes

The idea of the era of Néoprotérozoïque occurred during the the Sixties. The paleontologists of the 19th century thought that the first Métazoaire S appear at the beginning of the Cambrien, with the Trilobite S and the Archéocyathidés. At the beginning of the 20th century, one discovers métazoaires in the south of the Africa but those then were incorrectly dated. Others are discovered in Australia towards 1940, but are not examined in detail before the end of the Années 1950. Other potential fossils are found in Germany, Arizona, Ontario…

Some of these fossils are recognized as being Pseudo-fossil S, but of others prove to be members of a complex fauna which remains badly included/understood nowadays. One finds in at least twenty areas of the fossils of métazoaires preceding those by Cambrien.

Some animals seem possible ancestors of the modern animals, but the majority of the fossils are difficult to classify - as these mineralized discs, which were perhaps used as protection against the predatory ones, or these animals with plates of unknown source, etc they are named in general animal édiacarien S or vendiens. The majority are with soft body. Certain paleontologists connect much or the majority of these forms of life to modern forms of life, tandis of others seldom make such connections and consider that the majority of these animals are representatives of unknown species nowadays.

Denomination

The Nomenclature for Néoprotérozoïque changed during the last decades: were successively used the terms of Édicar (I) in, of Vendien, Varangien, Precambrian, Proto-cambrien and Éocambrien. Some authors included besides Néoprotérozoïque in the Cambrien.

In 2004, IUGS ratified the name Édiacarien like a geological system of Néoprotérozoïque, extending from -640 to -544 My.

See too

External bonds

Card on GeoWhen Database

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