Proterozoic
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Template:Proterozoic Infobox In geology, the Proterozoic is an eon prior to the first abundant complex life on Earth. The Proterozoic Eon extended from 2500 Ma to 542 Ma (million years ago). The Proterozoic is the most recent portion of the old informal Precambrian time.
During the Protoerozoic Era, there was an oxygen build-up on Earth. The first multi-cellular life was also formed. Classically, the boundary between the Proterozoic and the Paleozoic was set at the base of the Cambrian period when the first fossils of animals known as trilobites and archeocyathids appeared. In the second half of the 20th century, a number of fossil forms have been found in Proterozoic rocks, but the boundary of the Proterozoic has remained fixed at the base of the Cambrian -- currently placed at 542 Ma.
Proterozoic consists of 3 geologic eras called, from oldest to youngest:
The major well identified events were the transition to an oxygenated atmosphere during the Mesoproterozoic and several glaciations including the hypothesized Snowball Earth during the Cryogenian period which took place in the late Neoproterozoic. This was followed by the Ediacaran Period (635 to 542 Ma) which is characterized by the evolution of abundant soft bodied, multicellular organisms.
Template:Proterozoic Footerde:Proterozoikum et:Proterosoikum es:Era Proterozoica eo:Proterozoiko fr:Protérozoïque gl:Proterozoico it:Proterozoico he:פרוטרוזואיקון lt:Proterozojus nl:Proterozoïcum ja:原生代 pl:Proterozoik pt:Proterozóico sh:Proterozoik fi:Proterotsooinen eoni sv:Proterozoikum zh:元古宙