Proterozoic
From Freepedia
| Proterozoic eon |
|---|
| Geologic timescale of the Precambrian |
| (millions of years ago) |
|
<timeline> ImageSize = width:175 height:355 PlotArea = left:40 right:5 bottom:100 top:60 AlignBars = justify Period = from:542 till:2500 TimeAxis = orientation:vertical ScaleMajor = unit:year increment:500 start:1000 ScaleMinor = unit:year increment:100 start:600 Colors = id:eon value:rgb(1,0.7,1) legend:Proterozoic_eon # light purple id:era value:rgb(1,1,0.7) legend:Era # light yellow id:black value:black Legend = left:15 top:40 BarData = bar:eon bar:era PlotData= width:100 align:center textcolor:black mark:(line,black) bar:eon color:eon from:542 till:2500 # text:Proterozoic~(542-2500) bar:era color:era from:542 till:1000 text:Neoproterozoic~(542-1000) from:1000 till:1600 text:Mesoproterozoic~(1000-1600) from:1600 till:2500 text:Paleoproterozoic~(1600-2500) TextData = tabs:(25-left) pos:(15,350) text:"Preceded by:" text:^Archaean eon text:^and Neoarchean era pos:(15,90) text:"Followed by:" text:^Phanerozoic eon text:^and Paleozoic era </timeline> (expand) |
In geology, the Proterozoic is an eon prior to the first abundant complex life on Earth. The Proterozoic Eon extended from 2400 Ma to 545 Ma (million years ago).
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 Precambrian rocks, but the boundary of the Proterozoic has remained fixed at the base of the Cambrian -- currently thought to be around 542 Ma.
Proterozoic consists of 3 geologic periods (eras) called, from oldest to youngest:
The major well identified events were the transition to an Oxygenated atmosphere that probably occurred in the Mesoproterozoic and several glaciations the most severe of which took place in the late Neoproterozoic.
| Precambrian | |||
|---|---|---|---|
| Hadean eon | Archean eon | Proterozoic eon | Phanerozoic eon |
| Proterozoic eon | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Paleoproterozoic era | Mesoproterozoic era | Neoproterozoic era | |||||||
| Siderian | Rhyacian | Orosirian | Statherian | Calymmian | Ectasian | Stenian | Tonian | Cryogenian | Ediacaran |
