Paleoproterozoic

The Paleoproterozoic Era ( /pælioʊˌproʊtərəˈzoʊɪk-/;[1][2], also spelled Palaeoproterozoic), spanning the time period from 2,500 to 1,600 million years ago (2.5–1.6 Ga), is the first of the three sub-divisions (eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's geological history. It was during this era that the continents first stabilized.

Paleoproterozoic
2500 – 1600 Ma Pha. Proterozoic Archean Had'n
Chronology
Periods of the Paleoproterozoic -2500 — – -2400 — – -2300 — – -2200 — – -2100 — – -2000 — – -1900 — – -1800 — – -1700 — – -1600 — – P r o t e r o z o i c A Neoarchean P a l a e o p r o t e r o z o i c Mesoproterozoic Siderian Rhyacian Orosirian Statherian   An approximate timescale of key Paleoproterozoic events. Axis scale: millions of years ago.
Proposed redefinition(s)	2420–541 Ma Gradstein et al., 2012
Proposed subdivisions	Oxygenian Period, 2420–2250 Ma Gradstein et al., 2012 Jatulian/Eukaryian Period, 2250–2060 Ma Gradstein et al., 2012 Columbian Period, 2060–1780 Ma Gradstein et al., 2012
Etymology
Name formality	Formal
Alternate spelling(s)	Palaeoproterozoic
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Era
Stratigraphic unit	Erathem
Time span formality	Formal
Lower boundary definition	Defined Chronometrically
Lower boundary GSSP	N/A
GSSP ratified	N/A
Upper boundary definition	Defined Chronometrically
Upper boundary GSSP	N/A
GSSP ratified	N/A

Paleontological evidence suggests that the Earth's rotational rate during this era resulted in 20-hour days ~1.8 billion years ago, implying a total of ~450 days per year.[3]

Paleoatmosphere

Before the enormous increase in atmospheric oxygen, almost all existing lifeforms were anaerobic organisms, whose metabolism was based upon a form of cellular respiration that did not require oxygen. Free oxygen in large amounts is toxic to most anaerobic organisms. Consequently, the majority of the anaerobic lifeforms on Earth died when the atmospheric free-oxygen levels soared in an extinction event called the Great Oxidation Event. The only lifeforms that survived were either those resistant to the oxidizing and poisonous effects of oxygen, or those sequestered in oxygen-free environments. The sudden increase of atmospheric free oxygen and the ensuing extinction of the vulnerable lifeforms is widely considered to be the one of the first and most significant mass extinctions in the history of the Earth.[4]

Emergence of Eukarya

Many crown node eukaryotes (from which the modern-day eukaryotic lineages would have arisen) have been approximately dated to around the time of the Paleoproterozoic era.[5][6] While there is some debate as to the exact time at which eukaryotes evolved,[7][8] current understanding places it somewhere in this era.[9][10]

Geological events

During this era, the earliest global-scale continent-continent collision belts developed. The associated continent and mountain building events are represented by the 2.1–2.0 Ga Trans-Amazonian 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 Nagssugtoqidian 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 collision belts are interpreted as having resulted from one or more 2.0–1.8 Ga global-scale collision events that then led to the assembly of a Proterozoic supercontinent named Columbia or Nuna.[11][12]

Felsic volcanism in what is now northern Sweden led to the formation of the Kiruna and Arvidsjaur porphyries.[13]

The lithospheric mantle of Patagonia's oldest blocks formed.[14]

See also

• Boring Billion
• Suavjärvi crater – 2.4 billion years old
• Francevillian biota - 2.1-billion-year-old macroscopic organisms
• Vredefort crater – 2.0 billion years old
• Sudbury Basin – 1.849 billion years old

References

1. "palaeo-". Oxford Dictionaries UK Dictionary. Oxford University Press. Retrieved 2016-01-20. "Proterozoic". Oxford Dictionaries UK Dictionary. Oxford University Press. Retrieved 2016-01-20.
2. "Proterozoic". Merriam-Webster Dictionary.
3. Pannella, Giorgio (1972). "Paleontological evidence on the Earth's rotational history since early precambrian". Astrophysics and Space Science. 16 (2): 212. Bibcode:1972Ap&SS..16..212P. doi:10.1007/BF00642735. S2CID 122908383.
4. Margulis, Lynn; Sagan, Dorion (1997-05-29). Microcosmos: Four Billion Years of Microbial Evolution. University of California Press. ISBN 9780520210646.
5. Hedges, S Blair; Chen, Hsiong; Kumar, Sudhir; Wang, Daniel YC; Thompson, Amanda S; Watanabe, Hidemi (2001-09-12). "A genomic timescale for the origin of eukaryotes". BMC Evolutionary Biology. 1: 4. doi:10.1186/1471-2148-1-4. ISSN 1471-2148. PMC 56995. PMID 11580860.
6. Hedges, S Blair; Blair, Jaime E; Venturi, Maria L; Shoe, Jason L (2004-01-28). "A molecular timescale of eukaryote evolution and the rise of complex multicellular life". BMC Evolutionary Biology. 4: 2. doi:10.1186/1471-2148-4-2. ISSN 1471-2148. PMC 341452. PMID 15005799.
7. Rodríguez-Trelles, Francisco; Tarrío, Rosa; Ayala, Francisco J. (2002-06-11). "A methodological bias toward overestimation of molecular evolutionary time scales". Proceedings of the National Academy of Sciences of the United States of America. 99 (12): 8112–8115. Bibcode:2002PNAS...99.8112R. doi:10.1073/pnas.122231299. ISSN 0027-8424. PMC 123029. PMID 12060757.
8. Stechmann, Alexandra; Cavalier-Smith, Thomas (2002-07-05). "Rooting the eukaryote tree by using a derived gene fusion". Science. 297 (5578): 89–91. Bibcode:2002Sci...297...89S. doi:10.1126/science.1071196. ISSN 1095-9203. PMID 12098695. S2CID 21064445.
9. Ayala, Francisco José; Rzhetsky, Andrey; Ayala, Francisco J. (1998-01-20). "Origin of the metazoan phyla: Molecular clocks confirm paleontological estimates". Proceedings of the National Academy of Sciences of the United States of America. 95 (2): 606–611. Bibcode:1998PNAS...95..606J. doi:10.1073/pnas.95.2.606. ISSN 0027-8424. PMC 18467. PMID 9435239.
10. Wang, D Y; Kumar, S; Hedges, S B (1999-01-22). "Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi". Proceedings of the Royal Society B: Biological Sciences. 266 (1415): 163–171. doi:10.1098/rspb.1999.0617. PMC 1689654. PMID 10097391.
11. Zhao, Guochun; Cawood, Peter A; Wilde, Simon A; Sun, Min (2002). "Review of global 2.1–1.8 Ga orogens: implications for a pre-Rodinia supercontinent". Earth-Science Reviews. 59 (1–4): 125–162. Bibcode:2002ESRv...59..125Z. doi:10.1016/S0012-8252(02)00073-9.
12. Zhao, Guochun; Sun, M.; Wilde, Simon A.; Li, S.Z. (2004). "A Paleo-Mesoproterozoic supercontinent: assembly, growth and breakup". Earth-Science Reviews. 67 (1–2): 91–123. Bibcode:2004ESRv...67...91Z. doi:10.1016/j.earscirev.2004.02.003.
13. Lundqvist, Thomas (2009). Porfyr i Sverige: En geologisk översikt (in Swedish). pp. 24–27. ISBN 978-91-7158-960-6.
14. Schilling, Manuel Enrique; Carlson, Richard Walter; Tassara, Andrés; Conceição, Rommulo Viveira; Berotto, Gustavo Walter; Vásquez, Manuel; Muñoz, Daniel; Jalowitzki, Tiago; Gervasoni, Fernanda; Morata, Diego (2017). "The origin of Patagonia revealed by Re-Os systematics of mantle xenoliths". Precambrian Research. 294: 15–32. Bibcode:2017PreR..294...15S. doi:10.1016/j.precamres.2017.03.008.

External links

• EssayWeb Paleoproterozoic Era
• First breath: Earth's billion-year struggle for oxygen New Scientist, #2746, 5 February 2010 by Nick Lane. Posits an earlier much longer snowball period, c2.4 - c2.0 Gya, triggered by the Great Oxygenation Event.
• The information on eukaryotic lineage diversification was gathered from a New York Times opinion blog by Olivia Judson. See the text here: .
• Paleoproterozoic (chronostratigraphy scale)