View source for Earth:Paleoproterozoic

{{short description|First era of the Proterozoic Eon}}
{{Infobox geologic timespan
| name                         = Paleoproterozoic
| color                        = Paleoproterozoic
| top_bar                      = all time
| time_start                   = 2500
| time_end                     = 1600
| image_map                    =Paleoproterozoic stromatolites Franceville.jpg
| caption_map                  =Paleoproterozoic stromatolites
| image_outcrop                =
| caption_outcrop              =
| image_art                    =
| caption_art                  =
<!--Chronology--> 
| timeline                     = Paleoproterozoic
| proposed_boundaries1         = 2420–1780 Ma
| proposed_boundaries1_ref     = Gradstein et al., 2012
| proposed_subdivision1        = Oxygenian Period, 2420–2250 Ma
| proposed_subdivision1_coined = Gradstein et al., 2012
| proposed_subdivision2        = Jatulian/Eukaryian Period, 2250–2060 Ma
| proposed_subdivision2_coined = Gradstein et al., 2012
| proposed_subdivision3        = Columbian Period, 2060–1780 Ma
| proposed_subdivision3_coined = Gradstein et al., 2012
<!--Etymology-->
| name_formality               = Formal
| name_accept_date             =
| alternate_spellings          = Palaeoproterozoic
<!--Usage Information-->
| celestial_body               = earth
| usage                        = Global ([[Organization:International Commission on Stratigraphy|ICS]])
| timescales_used              = ICS Time Scale
<!--Definition-->
| chrono_unit                  = Era
| strat_unit                   = Erathem
| proposed_by                  =
| timespan_formality           = Formal
| lower_boundary_def           = Defined Chronometrically
| lower_gssa_accept_date       = 1991<ref name=Plumb1991>{{cite journal |last=Plumb |first=K. A. |date=June 1, 1991 |title=New Precambrian time scale |journal=Episodes |doi=10.18814/epiiugs/1991/v14i2/005 |volume=14 |issue=2 |pages=139–140|doi-access=free }}</ref>
| upper_boundary_def           = Defined Chronometrically
| upper_gssa_accept_date       = 1991<ref name=Plumb1991/>
}}
The '''Paleoproterozoic Era'''{{refn|There are several ways of pronouncing ''Paleoproterozoic'', including  {{IPAc-en|ipa|ˌ|p|æ|l|i|oʊ|ˌ|p|r|oʊ|t|ər|ə|ˈ|z|oʊ|ɪ|k|,_|ˌ|p|eɪ|-|,_|-|l|i|ə|-|,_|-|ˌ|p|r|ɒ|t|-|,_|-|ər|oʊ|-|,_|-|t|r|ə|-|,_|-|t|r|oʊ|-}} {{respell|PAL|ee|oh|PROH|tər|ə|ZOH|ik|,_|PAY-|,_|-PROT-|,_|-ər|oh-|,_|-trə-|,_|-|troh-}}.{{refn|{{Cite dictionary |url=http://www.lexico.com/definition/palaeo- |archive-url=https://web.archive.org/web/20200618014529/https://www.lexico.com/definition/palaeo- |url-status=dead |archive-date=2020-06-18 |title=palaeo- |dictionary=Lexico UK English Dictionary |publisher=[[Organization:Oxford University Press|Oxford University Press]]}} {{Cite dictionary |url=http://www.lexico.com/definition/Proterozoic |archive-url=https://web.archive.org/web/20200617035944/https://www.lexico.com/definition/proterozoic |url-status=dead |archive-date=2020-06-17 |title=Proterozoic |dictionary=Lexico UK English Dictionary |publisher=[[Organization:Oxford University Press|Oxford University Press]]}}}}{{refn|{{MerriamWebsterDictionary|Proterozoic}}}}}} (also spelled '''Palaeoproterozoic''') is the first of the three sub-divisions ([[Earth:Era (geology)|eras]]) of the [[Earth:Proterozoic|Proterozoic]] [[Earth:Eon (geology)|eon]], and also the longest era of the Earth's [[Earth:Geological history of Earth|geological history]], spanning from {{Ma|Paleoproterozoic|Mesoproterozoic}} (2.5–1.6&nbsp;[[Year|Ga]]). It is further subdivided into four geologic periods, namely the [[Earth:Siderian|Siderian]], [[Earth:Rhyacian|Rhyacian]], [[Earth:Orosirian|Orosirian]] and [[Earth:Statherian|Statherian]].

Paleontological evidence suggests that the Earth's rotational rate ~1.8 billion years ago equated to 20-hour days, implying a total of ~450 days per year.<ref>{{cite journal | last1 = Pannella | first1 = Giorgio | year = 1972 | title = Paleontological evidence on the Earth's rotational history since early precambrian | journal = [[Physics:Astrophysics and Space Science|Astrophysics and Space Science]] | volume = 16 | issue = 2| page = 212 | doi=10.1007/BF00642735 | bibcode=1972Ap&SS..16..212P| s2cid = 122908383 }}</ref> It was during this era that the [[Earth:Continent|continent]]s first stabilized.{{clarify|date=September 2022}}

== Atmosphere ==
{{Main|Earth:Prebiotic atmosphere|Earth:Geological history of oxygen|Earth:Great Oxygenation Event}}
The Earth's atmosphere were originally a weakly [[Astronomy:Reducing atmosphere|reducing atmosphere]] consisting largely of [[Chemistry:Nitrogen|nitrogen]], [[Chemistry:Methane|methane]], [[Chemistry:Ammonia|ammonia]], [[Chemistry:Carbon dioxide|carbon dioxide]] and [[Physics:Inert gas|inert gas]]es,<ref name=Zahnle/> somewhat comparable to Titan's atmosphere.<ref name="Trainer Pavlov DeWitt Jimenez pp. 18035–18042">{{cite journal | last1=Trainer | first1=Melissa G. | last2=Pavlov | first2=Alexander A. | last3=DeWitt | first3=H. Langley | last4=Jimenez | first4=Jose L. | last5=McKay | first5=Christopher P. | last6=Toon | first6=Owen B. | last7=Tolbert | first7=Margaret A. | title=Organic haze on Titan and the early Earth | journal=Proceedings of the National Academy of Sciences | volume=103 | issue=48 | date=2006-11-28 | issn=0027-8424 | doi=10.1073/pnas.0608561103 | pages=18035–18042| pmid=17101962 | pmc=1838702 | doi-access=free }}</ref> When oxygenic photosynthesis evolved in [[Biology:Cyanobacteria|cyanobacteria]] during the [[Earth:Mesoarchean|Mesoarchean]], the increasing amount of byproduct [[Chemistry:Dioxygen|dioxygen]] began to deplete the reductants in the [[Earth:Ocean|ocean]], land surface and the atmosphere. Eventually all surface reductants (particularly ferrous iron, [[Chemistry:Sulfur|sulfur]] and [[Earth:Atmospheric methane|atmospheric methane]]) were exhausted, and the atmospheric free oxygen levels soared permanently during the Siderian and Rhyacian periods in an [[Earth:Atmospheric chemistry|aerochemical]] event called the [[Earth:Great Oxidation Event|Great Oxidation Event]], which brought atmospheric oxygen from near none to up to 10% of the modern level.<ref>{{cite journal |last1=Ossa Ossa |first1=Frantz |last2=Spangenberg |first2=Jorge E. |last3=Bekker |first3=Andrey |last4=König |first4=Stephan |last5=Stüeken |first5=Eva E. |last6=Hofmann |first6=Axel |last7=Poulton |first7=Simon W. |last8=Yierpan |first8=Aierken |last9=Varas-Reus |first9=Maria I. |last10=Eickmann |first10=Benjamin |last11=Andersen |first11=Morten B. |last12=Schoenberg |first12=Ronny |date=15 September 2022 |title=Moderate levels of oxygenation during the late stage of Earth's Great Oxidation Event |journal=[[Earth:Earth and Planetary Science Letters|Earth and Planetary Science Letters]] |volume=594 |page=117716 |doi=10.1016/j.epsl.2022.117716 |doi-access=free |hdl=10481/78482 |hdl-access=free }}</ref>

== Emergence of eukaryotes and complex life ==
{{see|Symbiogenesis}}
At the beginning of the preceding [[Earth:Archean|Archean]] eon, almost all existing lifeforms were single-cell prokaryotic [[Biology:Anaerobic organism|anaerobic organism]]s whose [[Biology:Metabolism|metabolism]] was based on a form of [[Biology:Cellular respiration|cellular respiration]] that did not require oxygen, and [[Biology:Autotroph|autotroph]]s were either chemosynthetic or relied upon [[Biology:Anoxygenic photosynthesis|anoxygenic photosynthesis]]. After the Great Oxygenation Event, the then mainly [[Biology:Archaea|archaea]]-dominated anaerobic [[Biology:Microbial mat|microbial mat]]s were devastated as free oxygen is highly reactive and biologically toxic to cellular structures. This was compounded by a 300-million-year-long global icehouse event known as the [[Earth:Huronian glaciation|Huronian glaciation]] — at least partly due to the depletion of atmospheric methane, a powerful [[Chemistry:Greenhouse gas|greenhouse gas]] — resulted in what is widely considered one of the first and most significant mass extinctions on Earth.<ref>{{cite journal |last1=Hodgskiss |first1=Malcolm S. W. |last2= Crockford |first2=Peter W. |last3=Peng |first3=Yongbo |last4=Wing |first4=Boswell A. |last5=Horner |first5= Tristan J. |date=27 August 2019 |title=A productivity collapse to end Earth's Great Oxidation |journal=Proceedings of the National Academy of Sciences of the United States of America |df=dmy-all |volume=116 |issue=35 |pages=17207–17212 |doi=10.1073/pnas.1900325116 |doi-access=free |pmid=31405980 |pmc=6717284 |bibcode=2019PNAS..11617207H}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=eo_sMMRxgAUC&q=oxygen+holocaust&pg=PA99 |title=Microcosmos: Four Billion Years of Microbial Evolution |last1=Margulis |first1=Lynn |last2=Sagan |first2=Dorion |date=1997-05-29 |publisher=University of California Press |isbn=9780520210646 |language=en }}</ref> The organisms that thrived after the extinction were mainly aerobes that evolved [[Biology:Antioxidant#Oxidative challenge in biology|bioactive antioxidant]]s and eventually aerobic respiration, and surviving anaerobes were forced to live symbiotically alongside aerobes in hybrid colonies, which enabled the evolution of [[Biology:Mitochondria|mitochondria]] in eukaryotic organisms.

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.<ref>{{cite journal |last1=Mänd |first1=Kaarel |last2=Planavsky |first2=Noah J. |last3=Porter |first3=Susannah M. |last4=Robbins |first4=Leslie J. |last5=Wang |first5=Changle |last6=Kraitsmann |first6=Timmu |last7=Paiste |first7=Kärt |last8=Paiste |first8=Päärn |last9=Romashkin |first9=Alexander E. |last10=Deines |first10=Yulia E. |last11=Kirsimäe |first11=Kalle |last12=Lepland |first12=Aivo |last13=Konhauser |first13=Kurt O. |date=15 April 2022 |title=Chromium evidence for protracted oxygenation during the Paleoproterozoic |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X22001376 |journal=[[Earth:Earth and Planetary Science Letters|Earth and Planetary Science Letters]] |volume=584 |page=117501 |doi=10.1016/j.epsl.2022.117501 |access-date=15 December 2022|hdl=10037/24808 |hdl-access=free }}</ref><ref name=":0">{{Cite journal|last1=Hedges|first1=S Blair|last2=Chen|first2=Hsiong|last3=Kumar|first3=Sudhir|last4=Wang|first4=Daniel YC|last5=Thompson|first5=Amanda S|last6=Watanabe|first6=Hidemi|date=2001-09-12|title=A genomic timescale for the origin of eukaryotes|journal=BMC Evolutionary Biology|volume=1|pages=4|doi=10.1186/1471-2148-1-4|issn=1471-2148|pmid=11580860|pmc=56995 |doi-access=free }}</ref><ref name=":2">{{Cite journal|last1=Hedges|first1=S Blair|last2=Blair|first2=Jaime E|last3=Venturi|first3=Maria L|last4=Shoe|first4=Jason L|date=2004-01-28|title=A molecular timescale of eukaryote evolution and the rise of complex multicellular life|journal=BMC Evolutionary Biology|volume=4|pages=2|doi=10.1186/1471-2148-4-2|issn=1471-2148|pmid=15005799|pmc=341452 |doi-access=free }}</ref>
While there is some debate as to the exact time at which eukaryotes evolved,<ref>{{Cite journal|last1=Rodríguez-Trelles|first1=Francisco|last2=Tarrío|first2=Rosa|last3=Ayala|first3=Francisco J.|date=2002-06-11|title=A methodological bias toward overestimation of molecular evolutionary time scales|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=99|issue=12|pages=8112–8115|doi=10.1073/pnas.122231299|issn=0027-8424|pmid=12060757|pmc=123029|bibcode=2002PNAS...99.8112R|doi-access=free}}</ref><ref>{{Cite journal|last1=Stechmann|first1=Alexandra|last2=Cavalier-Smith|first2=Thomas|date=2002-07-05|title=Rooting the eukaryote tree by using a derived gene fusion|journal=Science|volume=297|issue=5578|pages=89–91|doi=10.1126/science.1071196|issn=1095-9203|pmid=12098695|bibcode=2002Sci...297...89S|s2cid=21064445}}</ref>
current understanding places it somewhere in this era.<ref>{{Cite journal|last1=Ayala|first1=Francisco José|last2=Rzhetsky|first2=Andrey|last3=Ayala|first3=Francisco J.|date=1998-01-20|title=Origin of the metazoan phyla: Molecular clocks confirm paleontological estimates|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=95|issue=2|pages=606–611|issn=0027-8424|pmid=9435239|pmc=18467|doi=10.1073/pnas.95.2.606|bibcode=1998PNAS...95..606J|doi-access=free}}</ref><ref>{{Cite journal|last1=Wang|first1=D Y|last2=Kumar|first2=S|last3=Hedges|first3=S B|date=1999-01-22|title=Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi.|journal=Proceedings of the Royal Society B: Biological Sciences|volume=266|issue=1415|pages=163–171|pmc=1689654|pmid=10097391|doi=10.1098/rspb.1999.0617}}</ref><ref>{{cite journal |last1=Javaux |first1=Emmanuelle J. |last2=Lepot |first2=Kevin |date=January 2018 |title=The Paleoproterozoic fossil record: Implications for the evolution of the biosphere during Earth's middle-age |journal=[[Earth:Earth-Science Reviews|Earth-Science Reviews]] |volume=176 |pages=68–86 |doi=10.1016/j.earscirev.2017.10.001 |doi-access=free |hdl=20.500.12210/62416 |hdl-access=free }}</ref> Statherian fossils from the [[Earth:Changcheng System|Changcheng Group]] in North China provide evidence that eukaryotic life was already diverse by the late Palaeoproterozoic.<ref>{{cite journal |last1=Miao |first1=Lanyun |last2=Moczydłowska |first2=Małgorzata |last3=Zhu |first3=Shixing |last4=Zhu |first4=Maoyan |date=February 2019 |title=New record of organic-walled, morphologically distinct microfossils from the late Paleoproterozoic Changcheng Group in the Yanshan Range, North China |url=https://www.sciencedirect.com/science/article/abs/pii/S0301926818301827 |journal=Precambrian Research |volume=321 |pages=172–198 |doi=10.1016/j.precamres.2018.11.019 |s2cid=134362289 |access-date=29 December 2022}}</ref>

== 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&nbsp;Ga Trans-Amazonian and Eburnean [[Physics:Orogeny|orogens]] in South America and West Africa; the ~2.0&nbsp;Ga [[Earth:Limpopo Belt|Limpopo Belt]] in southern Africa; the 1.9–1.8&nbsp;Ga [[Earth:Trans-Hudson orogeny|Trans-Hudson]], Penokean, Taltson–Thelon, Wopmay, Ungava and Torngat orogens in North America, the 1.9–1.8&nbsp;Ga Nagssugtoqidian Orogen in Greenland; the 1.9–1.8&nbsp;Ga Kola–Karelia, Svecofennian, Volhyn-Central Russian, and Pachelma orogens in Baltica (Eastern Europe); the 1.9–1.8&nbsp;Ga Akitkan Orogen in Siberia; the ~1.95&nbsp;Ga Khondalite Belt; the ~1.85&nbsp;Ga Trans-North China Orogen in North China; and the 1.8-1.6&nbsp;Ga Yavapai and Mazatzal orogenies in southern North America.

That pattern of collision belts supports the formation of a Proterozoic supercontinent named [[Earth:Columbia (supercontinent)|Columbia]] or Nuna.<ref name="Zhao1">{{Cite journal |last1=Zhao|first1=Guochun|last2=Cawood|first2=Peter A|last3=Wilde|first3=Simon A|last4=Sun|first4=Min|year=2002|title=Review of global 2.1–1.8 Ga orogens: implications for a pre-Rodinia supercontinent |journal=Earth-Science Reviews |volume=59 |issue=1–4|pages=125–162|doi=10.1016/S0012-8252(02)00073-9|bibcode = 2002ESRv...59..125Z }}</ref><ref name="Zhao2">{{Cite journal |first=Guochun |last=Zhao |author2=Sun, M. |author3=Wilde, Simon A. |author4= Li, S.Z.  |year=2004|title=A Paleo-Mesoproterozoic supercontinent: assembly, growth and breakup |journal=Earth-Science Reviews |volume=67 |issue=1–2 |pages=91–123|doi=10.1016/j.earscirev.2004.02.003|bibcode = 2004ESRv...67...91Z |url=http://www.gt-crust.ru/jour/article/view/518 }}</ref> That continental collisions suddenly led to mountain building at large scale is interpreted as having resulted from increased biomass and carbon burial during and after the Great Oxidation Event: Subducted carbonaceous sediments are hypothesized to have lubricated compressive deformation and led to crustal thickening.<ref>John Parnell, Connor Brolly: ''Increased biomass and carbon burial 2 billion years ago triggered mountain building.'' Nature Communications Earth & Environment, 2021, doi:10.1038/s43247-021-00313-5 (Open Access).</ref>

[[Earth:Felsic|Felsic]] volcanism in what is now northern Sweden led to the formation of the Kiruna and Arvidsjaur [[Earth:Porphyry (geology)|porphyries]].<ref name=Lundqvist_2009>{{cite book |last1=Lundqvist |first1=Thomas|date=2009 |title=Porfyr i Sverige: En geologisk översikt |isbn=978-91-7158-960-6 |language=sv |pages=24–27|publisher=Sveriges geologiska undersökning }}</ref>

The [[Earth:Subcontinental lithospheric mantle|lithospheric mantle]] of [[Earth:Tectonic evolution of Patagonia|Patagonia's oldest blocks]] formed.<ref>{{cite journal |last1=Schilling |first1=Manuel Enrique |last2=Carlson |first2=Richard Walter|last3=Tassara |first3=Andrés|last4=Conceição |first4=Rommulo Viveira|last5=Berotto |first5=Gustavo Walter|last6=Vásquez |first6=Manuel|last7= Muñoz|first7=Daniel |last8=Jalowitzki |first8=Tiago|last9=Gervasoni |first9=Fernanda|last10=Morata |first10=Diego |date=2017 |title=The origin of Patagonia revealed by Re-Os systematics of mantle xenoliths |journal=Precambrian Research |volume=294 |pages=15–32 |doi= 10.1016/j.precamres.2017.03.008|bibcode=2017PreR..294...15S}}</ref>


==See also==
* {{annotated link|Earth:Boring Billion}}
* {{annotated link|Earth:Suavjärvi|Suavjärvi impact structure}}
* {{annotated link|Earth:Francevillian biota}}
* {{annotated link|Earth:Vredefort impact structure}}
* {{annotated link|Earth:Sudbury Basin}}
* {{annotated link|Earth:Neoarchean}}, which immediately preceded the Paleoproterozoic

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20110903070338/http://essayweb.net/geology/timeline/paleoproterozoic.shtml EssayWeb Paleoproterozoic Era]
* [https://www.newscientist.com/article/mg20527461.100-first-breath-earths-billionyear-struggle-for-oxygen.html 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 [[Earth:Great Oxygenation Event|Great Oxygenation Event]].
* The information on eukaryotic lineage diversification was gathered from a {{wipe|New York Times}} opinion blog by [[Biography:Olivia Judson|Olivia Judson]]. See the text here: [http://opinionator.blogs.nytimes.com/2010/02/09/unorthodox/?ex=1281416400&en=973ef10b73da1c59&ei=5087&WT.mc_id=OP-D-I-NYT-MOD-MOD-M136-ROS-0210-L2&WT.mc_ev=click].
* [https://ghkclass.com/ghkC.html?paleoproterozoic Paleoproterozoic (chronostratigraphy scale)]

{{Geological history|c|state=collapsed}}

[[Category:Paleoproterozoic| ]]
[[Category:Geological eras]]

{{Sourceattribution|Paleoproterozoic}}