Editing Laurasia (section)

==Laurasia==
{{Multiple image | total_width = 600 | align = right
 | image1 = Uralian_orogeny_300Ma.jpg
 | image2 = Uralian_orogeny_280Ma.jpg
 | image3 = Uralian_orogeny_240Ma.jpg
 | footer = The Uralian orogeny and the formation of Laurasia 300, 280, and 240 Mya.<br />View centred on 25°N,35°E.
}}
During the Carboniferous to Permian periods,  Siberia, Kazakhstania, Baltica collided in the [[Uralian orogeny]] to form Laurasia.<ref name="Blakey-2003">{{Harvnb|Blakey|2003|loc=Assembly of Western Pangaea: Carboniferous–Permian, pp. 453–454; Assembly of Eastern Pangaea: Late Permian–Jurassic, p. 454; Fig. 10, p. 454}}</ref>

The Palaezoic-Mesozoic transition was marked by the reorganisation of Earth's tectonic plates which resulted in the assembly of Pangaea, and eventually its break-up. Caused by the detachment of subducted mantle slabs, this reorganisation resulted in rising [[mantle plume]]s that produced [[large igneous province]]s when they reached the crust. This tectonic activity also resulted in the [[Permian–Triassic extinction event]].  Tentional stresses across Eurasia developed into a large system of rift basins (Urengoy, East Uralian-Turgay, Khudosey) and [[flood basalt]]s in the [[West Siberian petroleum basin|West Siberian Basin]], the [[Pechora coal basin|Pechora Basin]], South China.<ref>{{Harvnb|Nikishin|Ziegler|Abbott|Brunet|2002|loc=Introduction, pp. 4–5; Fig. 4, p. 8}}</ref>

Laurasia and Gondwana were equal in size but had distinct geological histories. Gondwana was assembled before the formation of Pangaea, but the assembly of Laurasia occurred during and after the formation of the supercontinent. These differences resulted in different patterns of basin formation and transport of sediments. East Antarctica was the highest ground within Pangaea and produced sediments that were transported across eastern Gondwana but never reached Laurasia. During the Palaeozoic, c. 30–40% of Laurasia was covered by shallow marine water but only 10–20% of Gondwana was covered by shallow marine water.<ref>{{Harvnb|Rogers|Santosh|2004|loc=Differences Between Gondwana and Laurasia in Pangea, pp. 127, 130}}</ref>

===Asian blocks===
{{Multiple image | total_width = 400 | align = right | perrow = 2
 | image1 = Geology of Asia 450.Ma.jpg
 | image2 = Geology of Asia 350Ma.jpg
 | image3 = Geology of Asia 300Ma.jpg
 | image4 = Geology of Asia 200Ma.jpg
 | footer = Journey of the Asian blocks from Gondwana to Laurasia 450, 350, 300, and 200 Mya.<br />View centred on 0°S,105°E.
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During the assembly of Pangaea, Laurasia grew as continental blocks broke off Gondwana's northern margin; pulled by old closing oceans in front of them and pushed by new opening oceans behind them.<ref name="Zhao-etal2018-p14">{{Harvnb|Zhao|Wang|Huang|Dong|2018|loc=Closure of Paleo-Tethys Ocean and assembly of Pangea with East Asian blocks, pp. 14-16}}</ref> During the Neoproterozoic-Early Paleozoic break-up of Rodinia, the opening of the Proto-Tethys Ocean split the Asian blocks&nbsp;– Tarim, Qaidam, Alex, North China, South China&nbsp;– from the northern shores of Gondwana (north of India and Australia in modern coordinates) and the closure of the same ocean reassembled them along the same shores 500–460&nbsp;Mya resulting in Gondwana at its largest extent.<ref name="Zhao-etal-closure" />

The break-up of Rodinia also resulted in the opening of the long-lived Paleo-Asian Ocean between Baltica and Siberia in the north and Tarim and North China in the south. The closure of this ocean is preserved in the [[Central Asian Orogenic Belt]], the largest orogen on Earth.<ref name="Zhao-etal2018-p11">{{Harvnb|Zhao|Wang|Huang|Dong|2018|loc=Closure of Paleo-Asian Ocean: collision of Tarim, Alex and North China with East Europe and Siberia, pp. 11-14}}</ref>

North China, South China, Indochina, Tarim broke off from Gondwana during the Silurian to Devonian periods; as the Paleo-Tethys Ocean  opened behind them. Sibumasu and Qiantang and other Cimmerian continental fragments broke off in the Early Permian. [[Lhasa terrane|Lhasa]], [[Burma terrane|Burma]], Sikuleh, southwest Sumatra, West Sulawesi, and parts of Borneo, broke off during the Late Triassic-Late Jurassic.<ref>{{Harvnb|Metcalfe|1999|pp=15–16}}</ref>

During the Carboniferous and Permian, Baltica first collided with Kazakhstania and Siberia, then North China with Mongolia and Siberia. By the middle Carboniferous, however, South China had already been in contact with North China long enough to allow floral exchange between the two continents. The Cimmerian blocks rifted from Gondwana in the Late Carboniferous.<ref name="Blakey-2003" />

In the early Permian, the Neo-Tethys Ocean opened behind the Cimmerian terranes (Sibumasu, Qiantang, Lhasa) and, in the late Carboniferous, the Paleo-Tethys Ocean closed in front. The eastern branch of the Paleo-Tethys Ocean, however, remained opened while Siberia was added to Laurussia and Gondwana collided with Laurasia.<ref name="Zhao-etal2018-p14" />

When the eastern Palaeo-Tethys closed 250–230&nbsp;Mya, a series of Asian blocks&nbsp;– Sibumasu, Indochina, South China, Qiantang, Lhasa&nbsp;– formed a separate southern Asian continent.  This continent collided 240–220&nbsp;Mya with a northern continent&nbsp;– North China, Qinling, Qilian, Qaidam, Alex, Tarim&nbsp;– along the Central China orogen to form a combined East Asian continent.  The northern margins of the northern continent collided with Baltica and Siberia 310–250&nbsp;Ma, and thus the formation of the East Asian continent marked Pangaea at its greatest extent.<ref name="Zhao-etal2018-p14" /> By this time, the rifting of western Pangaea had already begun.<ref name="Blakey-2003" />

===Flora and fauna===
Pangaea split in two as the [[Tethys Ocean|Tethys Seaway]] opened between Gondwana and Laurasia in the Late Jurassic. The fossil record, however, suggests the intermittent presence of a Trans-Tethys land bridge, though the location and duration of such a land bridge remains enigmatic.<ref>{{Harvnb|Gheerbrant|Rage|2006|loc=Introduction, p. 225}}</ref>

[[Pinaceae|Pine trees]] evolved in the early Mesozoic c. 250&nbsp;Mya and the [[List of Pinus species|pine genus]] originated in Laurasia in the Early Cretaceous c. 130&nbsp;Mya in competition with faster growing [[Flowering plant|flowering plants]].  Pines adapted to cold and arid climates in environments where the growing season was shorter or wildfire common; this evolution limited pine range to between 31° and 50° north and resulted in a split into two subgenera: ''[[List of Pinus species|Strobus]]'' adapted to stressful environments and ''[[Pine|Pinus]]'' to fire-prone landscapes. By the end of the Cretaceous, pines were established across Laurasia, from North America to East Asia.<ref>{{Harvnb|Keeley|2012|loc=Introduction, pp. 445–446; Mesozoic origin and diversification, pp. 450–451}}</ref>

From the Triassic to the Early Jurassic, before the break-up of Pangaea, [[archosaur]]s (crurotarsans, pterosaurs and dinosaurs including birds) had a global distribution, especially crurotarsans, the group ancestral to the [[Crocodilia|crocodilians]].  This cosmopolitanism ended as Gondwana fragmented and Laurasia was assembled.  [[Pterosaur]] diversity reach a maximum in the Late Jurassic—Early Cretaceous and plate tectonic didn't affect the distribution of these flying reptiles. Crocodilian ancestors also diversified during the Early Cretaceous but were divided into Laurasian and Gondwanan populations; true crocodilians evolved from the former. The distribution of the three major groups of [[dinosaur]]s&nbsp;– the [[Sauropoda|sauropods]], [[Theropoda|theropods]], and [[ornithischia]]ns&nbsp;– was similar to that of the crocodilians. East Asia remained isolated with endemic species including [[Psittacosaurus|psittacosaurs]] (horned dinosaurs) and [[Ankylosauridae]] (club-tailed, armoured dinosaurs).<ref>{{Harvnb|Milner|Milner|Evans|2000|p=319}}</ref>

Meanwhile, [[Mammal|mammals]] slowly settled in Laurasia from Gondwana in the Triassic, the latter of which was the living area of their Permian [[Therapsida|ancestors]]. They split in two groups, with [[australosphenida|one]] returning to Gondwana (and stayed there after Pangaea split) while [[Tribosphenida|the other]] staying in Laurasia (until further descendants switched to Gondwana starting from the [[Jurassic]]).

In the early Eocene, a peak in global warming led to a pan-Arctic fauna with alligators and amphibians present north of the Arctic Circle. In the early Paleogene, landbridges still connected continents, allowing land animals to migrate between them. On the other hand, submerged areas occasionally divided continents: the [[Turgai Strait]] separated Europe and Asia from the Middle Jurassic to the Oligocene and as this strait dried out, a massive faunal interchange took place and the resulting extinction event in Europe is known as the ''[[Eocene–Oligocene extinction event|Grande Coupure]]''.<ref>{{Harvnb|Milner|Milner|Evans|2000|p=328}}</ref>

The [[Coraciiformes]] (an order of birds including kingfishers) evolved in Laurasia. While this group now has a mostly tropical distribution, they originated in the Arctic in the late Eocene c. 35&nbsp;Mya from where they diversified across Laurasia and further south across the Equator.<ref>{{Harvnb|McCullough|Moyle|Smith|Andersen|2019|loc=Conclusion, p. 7}}</ref>

The placental mammal group of [[Laurasiatheria]] is named after Laurasia.

===Final split===
{{Multiple image | total_width = 600 | align = right | perrow = 3
 | image1 = Opening of North Atlantic 090Ma.jpg
 | image2 = Opening of North Atlantic 050Ma.jpg
 | image3 = Opening of North Atlantic 030Ma.jpg
 | footer = Opening of the North Atlantic Ocean at 90, 50, and 30 Mya
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In the Triassic–Early Jurassic (c. 200&nbsp;Mya), the opening of the Central [[Atlantic Ocean]] was preceded by the formation of a series of large rift basins, such as the [[Newark Basin]], between eastern North America, from what is today the Gulf of Mexico to Nova Scotia, and in Africa and Europe, from Morocco to Greenland.<ref>{{Harvnb|Olsen|1997|loc=Introduction, p. 338}}</ref>

By c. 83&nbsp;Mya spreading had begun in the North Atlantic between the [[Rockall Basin]], a continental fragment sitting on top of the Eurasian Plate, and North America. By 56&nbsp;Mya, Greenland had become an independent plate, separated from North America by the [[Canadian Arctic Rift System|Labrador Sea-Baffin Bay Rift]]. By 33&nbsp;Mya, spreading had ceased in the Labrador Sea and relocated to the Mid-Atlantic Ridge.<ref>{{Harvnb|Seton|Müller|Zahirovic|Gaina|2012|loc=Rockall–North America/Greenland, p. 222}}</ref> The [[opening of the North Atlantic Ocean]] had effectively broken Laurasia in two.