Proterozoic
| Supereon | Eon | Era | Period | Start Million years ago |
|---|---|---|---|---|
| Phanerozoic | Palaeozoic | Cambrian | 0541 | |
| Precambrian | Proterozoic | Neoproterozoic | Ediacaran | 0635 |
| Cryogenian | 0850 | |||
| Tonian | 1000 | |||
| Mesoproterozoic | 1600 | |||
| Palaeoproterozoic | 2500 | |||
| Archaean | 4000 | |||
| Hadean | 4567 | |||
The Proterozoic eon comes before the Phanerozoic. It was a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life". The Proterozoic Eon extended from 2500 million years ago to 541 mya,[1] and is the most recent part of the former Precambrian.
The Proterozoic consists of 3 geologic eras, from oldest to youngest:
- Palaeoproterozoic: 2500 to 1600 million years ago
- Mesoproterozoic: 1600 to 1000 mya
- Neoproterozoic: 1000 to 542 mya
The well-identified events were:
- Rapid crustal segments collect into continents. Supercontinents Laurentia (Palaeoproterozoic) and Rodinia (Neoproterozoic) form.
- Early plate tectonics.
- First eukaryote fossil at 2.1 billion years.[2]p57
- Clean (unchanged by metamorphosis) sand and carbonate deposits occur for the first time.
- Oxygenation of the atmosphere, the Great Oxygenation Event.
- Several glaciations, including the Snowball Earth during the Cryogenian period in the late Neoproterozoic.
- The Ediacaran period (635 to 542mya) which is characterized by the evolution of abundant soft-bodied multicellular organisms.[3]
Study of these rocks shows that the eon featured massive, rapid continental accretion (unique to the Proterozoic), supercontinent cycles, and mountain building.[4]
Subdivisions [change]
Below is a table of subdivisions recognized by the International Commission on Stratigraphy.
| Eon | Era | Period | Start |
|---|---|---|---|
| Proterozoic | Palaeoproterozoic | Siderian | 2.5 - 2.25 billion years ago |
| Rhyacian | 2.25 - 2 billion years ago | ||
| Orosirian | 2 - 1.8 billion years ago | ||
| Statherian | 1.8 - 1.6 billion years ago | ||
| Mesoproterozoic | Calymmian | 1.6 - 1.4 billion years ago | |
| Ectasian | 1.4 - 1.2 billion years ago | ||
| Stenian | 1.2 - 1 billion years ago | ||
| Neoproterozoic | Tonian | 1 - 0.85 billion years ago | |
| Cryogenian | 0.85 - 0.635 billion years ago | ||
| Ediacaran | 0.635 - 0.54 billion years ago |
References [change]
- ↑ International Chronostratigraphic Chart. [1]
- ↑ Clarkson E.N.K. 1998. Invertbrate palaeontology and evolution. Blackwell, Oxford.
- ↑ Levin, Harold L. 2005. The Earth through time. 8th ed, Wiley, N.Y. Chapter 9: The Proterozoic: dawn of a more modern world.
- ↑ Stanley, Steven M. 1999. Earth system history. Freeman, N.Y.. ISBN 0-7167-2882-6.
| Precambrian (4.567 gya – 541 mya) | |
|---|---|
| In the left column are Eons, bold are Eras, not bold are Periods. gya = billion years ago, mya = million years ago | |
| Hadean (4.567 gya – 4 gya) | |
| Archaean (4 gya – 2.5 gya) | |
| Proterozoic (4 gya – 2.5 gya) | Palaeoproterozoic (2.5 gya – 1.6 gya)
Mesoproterozoic (1.6 gya – 1 gya) Neoproterozoic (1 gya - 541 mya) Tonian (1 gya – 850 mya) Cryogenian (850 mya – 635 mya) Ediacaran (635 mya – 541 mya) |
| Source | International Chronostratigraphic Chart 2013. International Commission on Stratigraphy, retrieved 8 April 2013. Divisions of geologic time – major chronostratigraphic and geochronologic units USGS, retrieved 8 April 2013. |
