Editing Triassic (section)

==Paleogeography==
[[File:230 Ma plate tectonic reconstruction.png|thumb|upright=1.5|350px|View of the Tethys area during the Ladinian stage (230&nbsp;Ma)]]
[[File:Pangaea (230 million years ago).png|thumb|350px|230&nbsp;Ma continental reconstruction]]During the Triassic, almost all the Earth's land mass was concentrated into a single [[supercontinent]], [[Pangaea]] ({{lit|entire land}}).<ref name="ForteKustatscherPreto">{{cite journal |last1=Forte |first1=Giuseppa |last2=Kustatscher |first2=Evelyn |last3=Preto |first3=Nereo |date=1 September 2022 |title=Carbon (δ13C) isotope variations indicate climate shifts and reflect plant habitats in the Middle Triassic (Anisian, Pelsonian) succession at Kühwiesenkopf / Monte Prà della Vacca (Dolomites, Northeast Italy) |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=601 |page=111098 |doi=10.1016/j.palaeo.2022.111098 |bibcode=2022PPP...60111098F |s2cid=249483335 |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018222002681 |access-date=1 December 2022|url-access=subscription }}</ref> This supercontinent was more-or-less centered on the equator and extended between the poles, though it did drift northwards as the period progressed. Southern Pangea, also known as [[Gondwana]], was made up by closely-appressed cratons corresponding to modern [[South America]], [[Africa]], [[Madagascar]], [[India]], [[Antarctica]], and [[Australia]]. North Pangea, also known as Laurussia or [[Laurasia]], corresponds to modern-day [[North America]] and the fragmented predecessors of [[Eurasia]].{{Citation needed|date=June 2024}} The [[Triassic Boreal Ocean Delta Plain]], the largest known delta plain in [[Geological history of Earth|Earth's geological history]] formed during this period in Northern Pangea.<ref>{{Cite journal |last=Tore Grane Klausen, Björn Nyberg, William Helland-Hansen |date=2019-03-22 |title=The largest delta plain in Earth's history |url=https://pubs.geoscienceworld.org/gsa/geology/article/47/5/470/569564/The-largest-delta-plain-in-Earth-s-history |journal=Geology |volume=47 |issue=5 |pages=470–474 |bibcode=2019Geo....47..470K |doi=10.1130/G45507.1 |access-date=2025-05-25}}</ref><ref>{{Cite journal |last=Klausen Tore, Suslova Anna, Nyberg Björn, Paterson Niall, Helland-Hansen, William |date=April 2018 |title=The largest delta plain in Earth's history and its implications for life in the Triassic |url=https://ui.adsabs.harvard.edu/abs/2018EGUGA..20..646K/abstract |journal=Egu General Assembly Conference Abstracts |page=646 |bibcode=2018EGUGA..20..646K |access-date=2025-05-25}}</ref>

The western edge of Pangea lay at the margin of an enormous ocean, [[Panthalassa]] ({{lit|entire sea}}), which roughly corresponds to the modern [[Pacific Ocean]]. Practically all deep-ocean crust present during the Triassic has been recycled through the [[subduction]] of oceanic plates, so very little is known about the open ocean from this time period. Most information on Panthalassan geology and marine life is derived from [[island arc]]s and rare seafloor sediments [[Accretion (geology)|accreted]] onto surrounding land masses, such as present-day Japan and western North America.{{Citation needed|date=June 2024}}

The eastern edge of Pangea was encroached upon by a pair of extensive oceanic basins: The [[Neotethys|Neo-Tethys]] (or simply Tethys) and [[Paleo-Tethys Ocean]]s. These extended from China to Iberia, hosting abundant marine life along their shallow tropical peripheries. They were divided from each other by a long string of microcontinents known as the [[Cimmerian terranes]]. Cimmerian crust had detached from Gondwana in the early Permian and drifted northwards during the Triassic, enlarging the Neo-Tethys Ocean which formed in their wake. At the same time, they forced the Paleo-Tethys Ocean to shrink as it was being subducted under Asia. By the end of the Triassic, the Paleo-Tethys Ocean occupied a small area and the Cimmerian terranes began to collide with southern Asia. This collision, known as the [[Cimmerian Orogeny]], continued into the Jurassic and [[Cretaceous]] to produce a chain of mountain ranges stretching from [[Turkey]] to [[Malaysia]].<ref>{{cite journal |last1=Mazaheri-Johari |first1=Mina |last2=Roghi |first2=Guido |last3=Caggiati |first3=Marcello |last4=Kustatscher |first4=Evelyn |last5=Ghasemi-Nejad |first5=Ebrahim |last6=Zanchi |first6=Andrea |last7=Gianolla |first7=Piero |date=15 January 2022 |title=Disentangling climate signal from tectonic forcing: The Triassic Aghdarband Basin (Turan Domain, Iran) |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018221005629 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=586 |page=110777 |doi=10.1016/j.palaeo.2021.110777 |bibcode=2022PPP...58610777M |s2cid=244696034 |access-date=10 January 2023|hdl=10281/338795 |hdl-access=free }}</ref><ref name="Cocks-2016-2016">{{cite book |editor1-last=Cocks |editor1-first=L. Robin M. |editor2-last=Torsvik |editor2-first=Trond H. |name-list-style=amp |date=2016 |section=Triassic |title=Earth History and Palaeogeography |pages=195–207 |place=Cambridge, UK |publisher=Cambridge University Press |doi=10.1017/9781316225523.012 |isbn=978-1-316-22552-3 |section-url=https://www.cambridge.org/core/books/earth-history-and-palaeogeography/triassic/CC5A8AA76EEAC6E2C5AD989F7B5F661C |access-date=2022-05-16}}</ref>[[File:(1)Saunders Quarry-1.jpg|thumb|left|[[Sydney]], [[Australia]] lies on Triassic [[shale]]s and sandstones. Almost all of the exposed rocks around Sydney belong to the Triassic [[Sydney sandstone]].<ref>{{cite book |last1=Herbert |first1=Chris |last2=Helby |first2=Robin |year=1980 |title=A Guide to the Sydney basin |publisher=Geological Survey of NSW |pages=582 |location=Maitland, NSW |isbn=978-0-7240-1250-3}}</ref>]]Pangaea was fractured by widespread faulting and rift basins during the Triassic—especially late in that period—but had not yet separated. The first nonmarine sediments in the [[rift]] that marks the initial break-up of Pangaea, which separated eastern North America from [[Morocco]], are of Late Triassic age; in the [[United States]], these thick sediments comprise the [[Newark Supergroup]].<ref>{{cite web |title=Lecture&nbsp;10 – Triassic: Newark, Chinle |website=rainbow.ldeo.columbia.edu |url=http://rainbow.ldeo.columbia.edu/courses/v1001/10.html}}</ref> Rift basins are also common in South America, Europe, and Africa. Terrestrial environments are particularly well-represented in the South Africa,<ref name="dinopedia-african">{{cite book |author=Jacobs, Louis L. |year=1997 |section=African Dinosaurs |editor1=Currie, Phillip J. |editor2=Padian, Kevin |title=Encyclopedia of Dinosaurs |publisher=Academic Press |pages=2–4}}</ref> Russia, central Europe, and the southwest United States. Terrestrial Triassic [[biostratigraphy]] is mostly based on terrestrial and freshwater tetrapods, as well as [[conchostracans]] ("clam shrimps"), a type of fast-breeding crustacean which lived in lakes and hypersaline environments.

Because a supercontinent has less shoreline compared to a series of smaller continents, Triassic marine deposits are relatively uncommon on a global scale. A major exception is in [[Western Europe]], where the Triassic was first studied. The northeastern margin of Gondwana was a stable [[passive margin]] along the Neo-Tethys Ocean, and marine sediments have been preserved in parts of northern India and [[Arabian Peninsula|Arabia]].<ref name="Cocks-2016-2016"/> In [[North America]], marine deposits are limited to a few exposures in the west.

===Scandinavia===
During the Triassic [[peneplain]]s are thought to have formed in what is now Norway and southern Sweden.<ref name=Karna1993>{{cite journal |last1=Lidmar-Bergström |first1=Karna |author-link=Karna Lidmar-Bergström |year=1993 |title=Denudation surfaces and tectonics in the southernmost part of the Baltic Shield |journal=[[Precambrian Research]] |volume=64 |issue=1–4 |pages=337–345 |doi=10.1016/0301-9268(93)90086-h |bibcode=1993PreR...64..337L}}</ref><ref name=Odleivetal2013>{{cite journal |last1=Olesen |first1=Odleiv |last2=Kierulf |first2=Halfdan Pascal |last3=Brönner |first3=Marco |last4=Dalsegg |first4=Einar |last5=Fredin |first5=Ola |last6=Solbakk |first6=Terje |date=2013 |title=Deep weathering, neotectonics and strandflat formation in Nordland, northern Norway |journal=[[Norwegian Journal of Geology]] |volume=93 |pages=189–213}}</ref><ref>{{cite journal |last1=Japsen |first1=Peter |last2=Green |first2=Paul F |last3=Bonow |first3=Johan M |last4=Erlström |first4=Mikael |year=2016 |title=Episodic burial and exhumation of the southern Baltic Shield: Epeirogenic uplifts during and after break-up of Pangaea |journal=[[Gondwana Research]] |volume=35 |pages=357–77 |bibcode=2016GondR..35..357J |doi=10.1016/j.gr.2015.06.005}}</ref> Remnants of this peneplain can be traced as a tilted [[summit accordance]] in the [[Swedish West Coast]].<ref name=Karna1993/> In northern Norway Triassic peneplains may have been buried in sediments to be then [[exhumation (geology)|re-exposed]] as coastal plains called [[strandflat]]s.<ref name=Odleivetal2013/> Dating of [[illite|illite clay]] from a strandflat of [[Bømlo]], southern Norway, have shown that landscape there became weathered in Late Triassic times ({{circa}} 210 million years ago) with the landscape likely also being shaped during that time.<ref name=Fredinetal2017>{{cite journal |last1=Fredin |first1=Ola |last2=Viola |first2=Giulio |last3=Zwingmann |first3=Horst |last4=Sørlie |first4=Ronald |last5=Brönner |first5=Marco |last6=Lie |first6=Jan-Erik |last7=Margrethe Grandal |first7=Else |last8=Müller |first8=Axel |last9=Margeth |first9=Annina |last10=Vogt |first10=Christoph |last11=Knies |first11=Jochen |display-authors=6 |year=2017 |title=The inheritance of a Mesozoic landscape in western Scandinavia |journal=Nature |volume=8 |page=14879 |doi=10.1038/ncomms14879 |pmid=28452366 |pmc=5477494 |bibcode=2017NatCo...814879F}}</ref>

=== Paleooceanography ===
[[Eustatic sea level]] in the Triassic was consistently low compared to the other geological periods. The beginning of the Triassic was around present sea level, rising to about {{convert|10|–|20|m|0}} above present-day sea level during the Early and Middle Triassic. Sea level rise accelerated in the Ladinian, culminating with a sea level up to {{convert|50|m|0}} above present-day levels during the Carnian. Sea level began to decline in the Norian, reaching a low of {{convert|50|m|0}} below present sea level during the mid-Rhaetian. Low global sea levels persisted into the earliest Jurassic. The long-term sea level trend is superimposed by 22 sea level drop events widespread in the geologic record, mostly of minor (less than {{convert|25|m|0|adj=on}}) and medium ({{convert|25|–|75|m|0|adj=on}}) magnitudes. A lack of evidence for Triassic continental ice sheets suggest that glacial eustasy is unlikely to be the cause of these changes.<ref name="Eustatic">{{Cite journal|last=Haq |first=Bilal U. |author-link=Bilal U. Haq |date=December 2018 |title=Triassic eustatic variations reexamined |journal=GSA Today |publisher=[[Geological Society of America]] |volume=28 |issue=12 |pages=4–9 |doi=10.1130/GSATG381A.1 |bibcode=2018GSAT...28l...4H |s2cid=134477691 |url=https://www.geosociety.org/gsatoday/science/G381A/article.htm|doi-access=free }}</ref> It has generally been assumed that the cause was changes in volume of the global ocean basin due to variations in oceanic volcanism, with largest volumes occurring in volcanism's absence when the ocean basins were subsiding.<ref>{{cite conference|editor-first1=Cheryl K.|editor-last1=Wilgus|editor-first2=Bruce S.|editor-last2=Hastings|editor-first3=Henry|editor-last3=Posamentier|editor-first4=John|editor-last4=van Wagoner|editor-first5=Charles A.|editor-last5=Ross|editor-first6=Christopher G. St. C.|editor-last6=Kendall |last=Embry |first=Ashton F. |chapter=Triassic Sea-Level Changes: Evidence from the Canadian Arctic Archipelago |title=Sea-Level Changes: An Integrated Approach|pages=249–259|publisher=Geological Survey of Canada|year=1985|location=[[Calgary]], [[Alberta]]}}</ref> Variation in water and sediment delivery to the oceans, with higher sea levels during pluvial eras lasting up to four million years, is also hypothesised to be behind these sea level variations.<ref name="Eustatic"/>