View source for Arctica

{{other uses|Arctica (disambiguation)}}
{{Distinguish|Arctic}}
{{short description|Ancient continent in the Neoarchean era}}
{{Infobox historical continent
| name               = Arctica
| image              = File:2400_Ma_paleoglobe.png
| caption            = Arctica, 2400 Ma ([[Siderian]])
| formation_year     = 2565 Ma
| type               = [[Paleocontinent]]
| today              = {{plainlist|
* [[Siberia (continent)|Siberian craton]]
* [[Slave craton|Slave Craton]]
* [[Wyoming craton|Wyoming Craton]]
* [[Superior craton|Superior Craton]]
* [[North Atlantic craton|North Atlantic Craton]]
}}
| smaller_continents = 
| plate              = 
| footnotes          = 
}}
'''Arctica,''' or '''Arctida'''<ref name="VerniDobre-2015-p206">{{Harvnb|Vernikovsky|Dobretsov|2015|p=206}}</ref> is a hypothetical ancient [[continent]] which formed approximately 2.565&nbsp;[[billion years ago]] in the [[Neoarchean]] era.  It was made of Archaean [[craton]]s, including the [[Siberian Craton]], with its [[Anabar Shield|Anabar]]/[[Aldan Shield|Aldan shield]]s in [[Siberia]],<ref>[http://rjes.wdcb.ru/v04/tje02090/tje02090.htm Siberian craton - a fragment of a Paleoproterozoic supercontinent]</ref> and the [[Slave craton|Slave]], [[Wyoming craton|Wyoming]], [[Superior craton|Superior]], and [[North Atlantic craton|North Atlantic]] cratons in North America.<ref>{{Harvnb|Rogers|1996|loc=Fig. 4, p. 97}}</ref>  Arctica was named by {{Harvnb|Rogers|1996}} because the [[Arctic Ocean]] formed by the separation of the [[North American Craton|North American]] and [[Siberia (continent)|Siberian]] cratons.<ref>{{Harvnb|Rogers|1996|p=97}}</ref>  Russian geologists writing in English call the continent "Arctida" since it was given that name in 1987,<ref name="VerniDobre-2015-p206" /> alternatively the '''Hyperborean craton''',<ref>E.g. {{Harvnb|Khain|Polyakova|Filatova|2009|loc=Tectonic units and their history, p. 335}}</ref> in reference to the [[hyperborea]]ns in [[Greek mythology]].

[[Nikolay Shatsky]] ({{Harvnb|Shatsky|1935}}) was the first to assume that the crust in the Arctic region was of continental origin.<ref>{{Harvnb|Khain|Filatova|2009|p=1076}}</ref>  Shatsky, however, was a "fixist" and, erroneously, explained the presence of Precambrian and Paleozoic metamorphic rocks on the New Siberian, Wrangel, and De Long Islands with [[subduction]].  "Mobilists", on the other hand, also erroneously, proposed that North America had rifted from Eurasia and that the Arctic basins had opened behind a retreating Alaska.<ref>{{Harvnb|Zonenshain|Natapov|1987|loc=Introduction, p. 829}}</ref>

==Precambrian continent==
In his reconstruction of the [[supercontinent cycle]], Rogers proposed that the continent [[Ur (continent)|Ur]] formed at about 3&nbsp;[[Gigaannum|Ga]] and formed East [[Gondwana]] in the Middle Proterozoic by accretion to [[East Antarctica]]; Arctica formed around 2.5–2&nbsp;Ga by the amalgamation of the [[Canadian Shield|Canadian]] and Siberian shields plus Greenland; and [[Atlantica]] formed around 2&nbsp; Ga by the amalgamation of the [[West African craton|West African Craton]] and eastern South America.  Arctica then grew around 1.5&nbsp; Ga by accretion of East Antarctica and [[Baltica]] to form the supercontinent [[Nena (supercontinent)|Nena]].  Around 1&nbsp; Ga Nena, Ur, and Atlantica collided to form the supercontinent [[Rodinia]].<ref>{{Harvnb|Rogers|1996|loc=Abstract}}</ref>

{{Harvnb|Rogers|Santosh|2003}} argued that most cratons that were around at 2.5&nbsp;Ga most likely formed in a single region simply because they were located in a single region in Pangaea, which is the reason Rogers argued for the existence of Arctica.
The core of Arctica was the Canadian Shield, which {{Harvnb|Williams|Hoffman|Lewry|Monger|1991}} named [[Kenorland]]. They argued that this continent formed around 2.5&nbsp; Ga and then rifted before reassembling along the 1.8&nbsp; Ga [[Trans-Hudson orogeny|Trans-Hudson]] and [[Taltson-Thelon orogeny|Taltson-Thelon]] orogenies.  These two orogenies are derived from continental crust (not oceanic crust) and were probably intracontinental, leaving Kenorland intact from 2.5&nbsp; Ga to the present.  Correlations between orogenies in Canada and Siberia remain more controversial.<ref>{{Harvnb|Rogers|Santosh|2003|loc=Arctica and Kenorland (~2500&nbsp; Ma), pp.&nbsp;360–361}}</ref>

[[Laurentia]] and Baltica were connected during the Late Palaeoproterzoic (1.7–1.74&nbsp; Ga) and Siberia later joined them.  Paleomagnetic reconstructions indicate that they formed a single supercontinent during the Mesoproterozoic (1.5–1.45&nbsp; Ga) but paleomagnetic data and geological pieces of evidence also suggest a considerable spatial gap between Siberia and Laurentia and Arctica is thought to be the missing link.<ref>{{Harvnb|Tait|Pisarevsky|2009|p=37}}</ref>

==Phanerozoic microcontinent==
The current geological structure of the Arctic Region is the result of tectonic processes during the Mesozoic and Cenozoic (250&nbsp;[[Megaannum|Ma]] to present) when the [[Amerasian Basin|Amerasian]] and [[Eurasian Basin|Eurasian]] basins formed, but the presence of Precambrian metamorphic complexes discovered in the 1980s indicated a continent once existed between [[Laurentia]], [[Baltica]], and [[Siberia (continent)|Siberia]].<ref name="Vernikovsky-2014-intro">{{Harvnb|Vernikovsky|Metelkin|Vernikovskaya|Matushkin|2014|loc=Introduction, pp. 265–266}}</ref>

In the reconstruction of {{Harvnb|Metelkin|Vernikovsky|Matushkin|2015}}, Arctica originally formed as a continent during the [[Tonian]] 950&nbsp;Ma and became part of the supercontinent [[Rodinia]].  It reformed during the Permian-Triassic 255&nbsp;Ma and became part of [[Pangaea]].  During this period the configuration of Arctica changed and the continent moved from near the Equator to near the North Pole while keeping its position between three major cratons: Laurentia, Baltica, and Siberia.<ref name="VerniDobre-2015-p206" /><ref>{{Harvnb|Vernikovsky|Dobretsov|2015|loc=Fig. 2, p. 208}}</ref>
An extended magmatic event, the [[High Arctic Large Igneous Province]], broke Arctica in part 130–90&nbsp;Ma, opened the [[Arctic Ocean]], and left radiating [[dyke swarm]]s across the Arctic.<ref>{{Harvnb|Ernst|Bleeker|2010|loc=90–130 Ma: northern Canada, initiation of the Arctic Ocean, p. 701, fig. 6b, p.705}}</ref>

Fragments of this continent include the [[Kara Sea|Kara Shelf]], [[New Siberian Islands]], northern [[Alaska]], [[Chukotka Peninsula]], Inuit Fold Belt in northern Greenland, and two Arctic underwater ridges, the [[Lomonosov Ridge|Lomonosov]] and [[Alpha Ridge|Alpha]]-[[Mendeleev Ridge]]s.  More recent reconstructions also include Barentsia (including [[Svalbard]] and Timan-Pechora Plates).<ref name="Vernikovsky-2014-intro" />
Remains of the last continent are now located on the [[Kara Sea]] Shelf, [[New Siberian Islands]] and adjacent shelf, [[Alaska]] north of [[Brooks Range|Brooks Ridge]], [[Chukchi Peninsula]] in easternmost Siberia, and fragments in northern [[Greenland]] and [[Northern Canada]] and in the submerged [[Lomonosov Ridge]].<ref>{{Harvnb|Metelkin|Vernikovsky|Matushkin|2015|loc=Introduction, p. 114; Fig. 1, p. 115}}</ref>

== See also ==
* {{Annotated link|Arctic Alaska-Chukotka terrane}}
* {{annotated link|Penokean orogeny}}
* {{annotated link|Timanide Orogen}}

== References ==

===Notes===
{{Reflist|30em}}

===Sources===
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{{Refend}}

{{Continents of the world}}

[[Category:Historical continents]]
[[Category:Archean]]
[[Category:Proterozoic]]
[[Category:Natural history of Asia]]
[[Category:Natural history of North America]]
[[Category:Prehistory of the Arctic]]
[[Category:Former supercontinents]]