Paleoproterozoic

Paleoproterozoic era
2500 - 1600 million years ago
Key events in the Paleoproterozoic
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An approximate timescale of key Paleoproterozoic events.
Axis scale: millions of years ago.

The Paleoproterozoic ( /ˌpeɪlɪ.oʊˌproʊtərɵˈzoʊ.ɨk/; also Palaeoproterozoic) is the first of the three sub-divisions (eras) of the Proterozoic occurring between 2,500 to 1,600 million years ago. This is when the continents first stabilized. This is also when cyanobacteria evolved, a type of bacteria which uses the biochemical process of photosynthesis to produce energy and oxygen.

Before the significant increase in atmospheric oxygen almost all life that existed was anaerobic, that is, the metabolism of life depended on a form of cellular respiration that did not require oxygen. Free oxygen in large amounts is poisonous to most anaerobic bacteria, and at this time most life on Earth vanished. The only life that remained was either resistant to the oxidizing and poisonous effects of oxygen, or spent its life-cycle in an oxygen-free environment. This main event is called the oxygen catastrophe. Also the Francevillian Group and Grypania fossils and the first eukaryotes appeared during this time.

Paleontological evidence on the Earth's rotational history suggests that ~1.8 billion years ago, there were about 450 days in a year, implying 20 hour days.[1]

The crown eukaryotes, from which all modern day eukaryotic lineages have arisen, date back to the paleoproterozoic sub-division. Also, during this time (~1 bya), the latest common ancestors between the ciliate and flagellate lineages probably diverged .

During this era the earliest global-scale continent-continent collisional belts developed, represented by the 2.1-2.0 Ga (Ga = billion year) Transamazonian and Eburnean Orogens in South America and West Africa; the ~2.0 Ga Limpopo Belt in southern Africa; the 1.9–1.8 Ga Trans-Hudson, Penokean, Taltson–Thelon, Wopmay, Ungava and Torngat orogens in North America, the 1.9–1.8 Ga Nagssugtoqidain Orogen in Greenland; the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volhyn-Central Russian, and Pachelma Orogens in Baltica (Eastern Europe); the 1.9–1.8 Ga Akitkan Orogen in Siberia; the ~1.95 Ga Khondalite Belt and ~1.85 Ga Trans-North China Orogen in North China. These continental collisional belts are interpreted as having resulted from 2.0-1.8 Ga global-scale collisional events that led to the assembly of a Paleo-Mesoproterozoic supercontinent named "Columbia" or "Nuna".[2][3]

See also

(Impact events)

References

  1. ^ Giorgio Pannella Paleontological evidence on the Earth's rotational history since early precambrian Astrophysics and Space Science 16.2 (1972): 212
  2. ^ Zhao, Guochun; Cawood, Peter A.; Wilde, Simon A.; Sun, M. (2002). "Review of global 2.1–1.8 Ga orogens: implications for a pre-Rodinia supercontinent". Earth-Science Reviews 59: 125–162. doi:10.1016/S0012-8252(02)00073-9. 
  3. ^ Zhao, Guochun; Sun, M.; Wilde, Simon A.; Li, S.Z. (2004). "A Paleo-Mesoproterozoic supercontinent: assembly, growth and breakup". Earth-Science Reviews 67: 91–123. doi:10.1016/j.earscirev.2004.02.003. 

External links

Preceded by Archean Eon 2.5 Ga - Proterozoic Eon - 542 Ma Followed by Phanerozoic Eon
2.5 Ga - Paleoproterozoic Era - 1.6 Ga 1.6 Ga - Mesoproterozoic Era - 1.0 Ga 1.0 Ga - Neoproterozoic Era - 542 Ma
Siderian Rhyacian Orosirian Statherian Calymmian Ectasian Stenian Tonian Cryogenian Ediacaran
 
In left column are eons; right column: bold are eras; not bold are periods:
Hadean
(4.57 – 4 Gya)
(informal)
Archean
(4 – 2.5 Gya)
Proterozoic
(2.5 Gya – 542 Mya)
Mya = millions years ago. Gya = billions years ago.