Late Triassic Explained

Late/Upper Triassic
Color:Late Triassic
Time Start:237
Time Start Prefix:~
Time End:201.4
Time End Uncertainty:0.2
Caption Map:Map of Earth as it appeared 220 million years ago during the Late Triassic, Norian stage
Timeline:Triassic
Chrono Name:Late Triassic
Strat Name:Upper Triassic
Name Formality:Formal
Celestial Body:Earth
Usage:Global (ICS)
Timescales Used:ICS Time Scale
Chrono Unit:Epoch
Strat Unit:Series
Timespan Formality:Formal
Lower Boundary Def:FAD of the Ammonite Daxatina canadensis
Lower Gssp Location:Prati di Stuores, Dolomites, Italy
Lower Gssp Accept Date:2008[1]
Upper Boundary Def:FAD of the Ammonite Psiloceras spelae tirolicum
Upper Gssp Location:Kuhjoch section, Karwendel mountains, Northern Calcareous Alps, Austria
Upper Gssp Accept Date:2010[2]

The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. The corresponding series of rock beds is known as the Upper Triassic. The Late Triassic is divided into the Carnian, Norian and Rhaetian ages.

Many of the first dinosaurs evolved during the Late Triassic, including Plateosaurus, Coelophysis, Herrerasaurus, and Eoraptor. The Triassic–Jurassic extinction event began during this epoch and is one of the five major mass extinction events of the Earth.[3]

Etymology

The Triassic was named in 1834 by Friedrich von Alberti, after a succession of three distinct rock layers (Greek meaning 'triad') that are widespread in southern Germany: the lower Buntsandstein (colourful sandstone), the middle Muschelkalk (shell-bearing limestone) and the upper Keuper (coloured clay).[4] The Late Triassic Series corresponds approximately to the middle and upper Keuper.[5]

Dating and subdivisions

On the geologic time scale, the Late Triassic is usually divided into the Carnian, Norian, and Rhaetian ages, and the corresponding rocks are referred to as the Carnian, Norian, and Rhaetian stages.

Triassic chronostratigraphy was originally based on ammonite fossils, beginning with the work of Edmund von Mojsisovics in the 1860s. The base of the Late Triassic (which is also the base of the Carnian) is set at the first appearance of an ammonite, Daxatina canadensis. In the 1990s, conodonts became increasingly important in the Triassic timescale, and the base of the Rhaetian is now set at the first appearance of a conodont, Misikella posthernsteini., the base of the Norian has not yet been established, but will likely be based on conodonts.[6]

The late Triassic is also divided into land-vertebrate faunachrons. These are, from oldest to youngest, the Berdyankian, Otischalkian, Adamanian, Revueltian and Apachean.[7]

Late Triassic life

Following the Permian–Triassic extinction event, surviving organisms diversified. On land, archosauriforms, most notably the dinosaurs became an important faunal component in the Late Triassic. Likewise, bony fishes diversified in aquatic environments, most notably the Neopterygii, to which nearly all extant species of fish belong. Among the neopterygians, stem-group teleosts and the now extinct Pycnodontiformes became more abundant in the Late Triassic.[8]

Carnian Age

See main article: Carnian. The Carnian is the first age of the Late Triassic, covering the time interval from 237 to 227 million years ago. The earliest true dinosaurs likely appeared during the Carnian and rapidly diversified.[9] [10] They emerged in a world dominated by crurotarsan archosaurs (ancestors of crocodiles), predatory phytosaurs, herbivorous armored aetosaurs, and giant carnivorous rauisuchians, which the dinosaurs gradually began to displace.[11]

The emergence of the first dinosaurs came at about the same time as the Carnian pluvial episode, at 234 to 232 Ma. This was a humid interval in the generally arid Triassic. It was marked by high extinction rates in marine organisms, but may have opened niches for the radiation of the dinosaurs.[12] [13]

Norian Age

See main article: Norian. The Norian is the second age of the Late Triassic, covering the time interval from about 227 to 208.5 million years ago. During this age, herbiverous sauropodomorphs diversified and began to displace the large herbivorous therapsids, perhaps because they were better able to adapt to the increasingly arid climate.[14] However crurotarsans continued to occupy more ecological niches than dinosaurs.[11] In the oceans, neopterygian fish proliferated at the expense of ceratitid ammonites.[15]

The Manicouagan impact event occurred 214 million years ago. However, no extinction event is associated with this impact.[16] [17]

Rhaetian Age

See main article: Rhaetian. The Rhaetian Age was the final age of the Late Triassic, following the Norian Age, and it included the last major disruption of life until the end-Cretaceous mass extinction. This age of the Triassic is known for its extinction of marine reptiles, such as nothosaurs and shastasaurs with the ichthyosaurs, similar to today's dolphin. This age was concluded with the disappearance of many species that removed types of plankton from the ocean, as well as some organisms known for reef-building, and the pelagic conodonts. In addition to these species that became extinct, the straight-shelled nautiloids, placodonts, bivalves, and many types of reptiles did not survive through this age.

Climate and environment during the Triassic Period

During the beginning of the Triassic Period, the Earth consisted of a giant landmass known as Pangea, which covered about a quarter of Earth's surface. Towards the end of the period, continental drift occurred which separated Pangea. At this time, polar ice was not present because of the large differences between the equator and the poles. A single, large landmass similar to Pangea would be expected to have extreme seasons; however, evidence offers contradictions. Evidence suggests that there is arid climate as well as proof of strong precipitation. The planet's atmosphere and temperature components were mainly warm and dry, with other seasonal changes in certain ranges.

The Middle Triassic was known to have consistent intervals of high levels of humidity. The circulation and movement of these humidity patterns, geographically, are not known however. The major Carnian Pluvial Event stands as one focus point of many studies. Different hypotheses of the events occurrence include eruptions, monsoonal effects, and changes caused by plate tectonics. Continental deposits also support certain ideas relative to the Triassic Period. Sediments that include red beds, which are sandstones and shales of color, may suggest seasonal precipitation. Rocks also included dinosaur tracks, mudcracks, and fossils of crustaceans and fish, which provide climate evidence, since animals and plants can only live during periods of which they can survive through.

Evidence of environmental disruption and climate change

The Late Triassic is described as semiarid. Semiarid is characterized by light rainfall, having up to 10–20 inches of precipitation a year. The epoch had a fluctuating, warm climate in which it was occasionally marked by instances of powerful heat. Different basins in certain areas of Europe provided evidence of the emergence of the "Middle Carnian Pluvial Event." For example, the Western Tethys and German Basin was defined by the theory of a middle Carnian wet climate phase. This event stands as the most distinctive climate change within the Triassic Period. Propositions for its cause include:

Theories and concepts are supported universally, due to extensive areal proof of Carnian siliciclastic sediments. The physical positions as well as comparisons of that location to surrounding sediments and layers stood as basis for recording data. Multiple resourced and recurring patterns in results of evaluations allowed for the satisfactory clarification of facts and common conceptions on the Late Triassic. Conclusions summarized that the correlation of these sediments led to the modified version of the new map of Central Eastern Pangea, as well as that the sediment's relation to the "Carnian Pluvial Event" is greater than expected.

Triassic–Jurassic extinction event

See main article: Triassic–Jurassic extinction event. The extinction event that began during the Late Triassic resulted in the disappearance of about 76% of all terrestrial and marine life species, as well as almost 20% of taxonomic families. Although the Late Triassic Epoch did not prove to be as destructive as the preceding Permian Period, which took place approximately 50 million years earlier and destroyed about 70% of land species, 57% of insect families as well as 95% of marine life, it resulted in great decreases in population sizes of many living organism populations.

The environment of the Late Triassic had negative effects on the conodonts and ammonoid groups. These groups once served as vital index fossils, which made it possible to identify feasible life span to multiple strata of the Triassic strata. These groups were severely affected during the epoch, and conodonts became extinct soon after (in the earliest Jurassic). Despite the large populations that withered away with the coming of the Late Triassic, many families, such as the pterosaurs, crocodiles, mammals and fish were very minimally affected. However, such families as the bivalves, gastropods, marine reptiles and brachiopods were greatly affected and many species became extinct during this time.

Causes of the extinction

Most of the evidence suggests the increase of volcanic activity was the main cause of the extinction. As a result of the rifting of the super continent Pangea, there was an increase in widespread volcanic activity which released large amounts of carbon dioxide. At the end of the Triassic Period, massive eruptions occurred along the rift zone, known as the Central Atlantic Magmatic Province, for about 500,000 years. These intense eruptions were classified as flood basalt eruptions, which are a type of large scale volcanic activity that releases a huge volume of lava in addition to sulfur dioxide and carbon dioxide. The sudden increase in carbon dioxide levels is believed to have enhanced the greenhouse effect, which acidified the oceans and raised average air temperature. As a result of the change in biological conditions in the oceans, 22% of marine families became extinct. In addition, 53% of marine genera and about 76–86% of all species became extinct, which vacated ecological niches; thus, enabling dinosaurs to become the dominant presence in the Jurassic Period. While the majority of the scientists agree that volcanic activity was the main cause of the extinction, other theories suggest the extinction was triggered by the impact of an asteroid, climate change, or rising sea levels.

Biological impact

The impacts that the Late Triassic had on surrounding environments and organisms were wildfire destruction of habitats and prevention of photosynthesis. Climatic cooling also occurred due to the soot in the atmosphere. Studies also show that 103 families of marine invertebrates became extinct at the end of the Triassic, but another 175 families lived on into the Jurassic. Marine and extant species were hit fairly hard by extinctions during this epoch. Almost 20% of 300 extant families became extinct; bivalves, cephalopods, and brachiopods suffered greatly. 92% of bivalves were wiped out episodically throughout the Triassic.

The end of the Triassic also brought about the decline of corals and reef builders during what is called a "reef gap". The changes in sea levels brought this decline upon corals, particularly the calcisponges and scleractinian corals. However, some corals would make a resurgence during the Jurassic Period. 17 brachiopod species were also wiped out by the end of the Triassic. Furthermore, conulariids became extinct.

Sources

Further reading

Notes and References

  1. Mietto . Paolo . Manfrin . Stefano . Preto . Nereo . Rigo . Manuel . Roghi . Guido . Furin . Stefano . Gianolla . Piero . Posenato . Renato . Muttoni . Giovanni . Nicora . Alda . Buratti . Nicoletta . Cirilli . Simonetta . Spötl . Christoph . Ramezani . Jahandar . Bowring . Samuel . The Global Boundary Stratotype Section and Point (GSSP) of the Carnian Stage (Late Triassic) at Prati Di Stuores/Stuores Wiesen Section (Southern Alps, NE Italy) . Episodes . September 2012 . 35 . 3 . 414–430 . 10.18814/epiiugs/2012/v35i3/003 . 13 December 2020.
  2. Hillebrandt . A.v. . Krystyn . L. . Kürschner . W.M. . Bonis . N.R. . Ruhl . M. . Richoz . S. . Schobben . M. A. N. . Urlichs . M. . Bown . P.R. . Kment . K. . McRoberts . C.A. . Simms . M. . Tomãsových . A . The Global Stratotype Sections and Point (GSSP) for the base of the Jurassic System at Kuhjoch (Karwendel Mountains, Northern Calcareous Alps, Tyrol, Austria) . Episodes . September 2013 . 36 . 3 . 162–198 . 10.18814/epiiugs/2013/v36i3/001 . 10.1.1.736.9905 . 128552062 .
  3. Blackburn. Terrence J.. Olsen. Paul E.. Bowring. Samuel A.. McLean. Noah M.. Kent. Dennis V. Puffer. John. McHone. Greg. Rasbury. Troy. Et-Touhami7. Mohammed. 2013. Zircon U-Pb Geochronology Links the End-Triassic Extinction with the Central Atlantic Magmatic Province. Science. 340. 6135. 941–945. 2013Sci...340..941B. 10.1.1.1019.4042. 10.1126/science.1234204. 23519213. 15895416.
  4. Friedrich von Alberti, Beitrag zu einer Monographie des bunten Sandsteins, Muschelkalks und Keupers, und die Verbindung dieser Gebilde zu einer Formation [Contribution to a monograph on the colored sandstone, shell limestone and mudstone, and the joining of these structures into one formation] (Stuttgart and Tübingen, (Germany): J. G. Cotta, 1834). Alberti coined the term "Trias" on page 324 :
    "… bunter Sandstein, Muschelkalk und Keuper das Resultat einer Periode, ihre Versteinerungen, um mich der Worte E. de Beaumont’s zu bedeinen, die Thermometer einer geologischen Epoche seyen, … also die bis jezt beobachtete Trennung dieser Gebilde in 3 Formationen nicht angemessen, und es mehr dem Begriffe Formation entsprechend sey, sie zu einer Formation, welche ich vorläufig Trias nennen will, zu verbinden."
    (… colored sandstone, shell limestone, and mudstone are the result of a period; their fossils are, to avail myself of the words of E. de Beaumont, the thermometer of a geologic epoch; … thus the separation of these structures into 3 formations, which has been maintained until now, isn't appropriate, and it is more consistent with the concept of "formation" to join them into one formation, which for now I will name "trias".)
  5. Mohr . Markus . Warren . John K. . Kukla . Peter A. . Urai . Janos L. . Irmen . Anton . Subsurface seismic record of salt glaciers in an extensional intracontinental setting (Late Triassic of northwestern Germany) . Geology . 2007 . 35 . 11 . 10.1130/G23378A.1 . Page 963; figure 1A.
  6. Lucas . Spencer G. . Spencer G. Lucas . The Triassic chronostratigraphic scale: history and status . Geological Society, London, Special Publications . 2010 . 334 . 1 . 17–39 . 10.1144/SP334.2. 129648527 .
  7. Book: Lucas . Spencer G. . The Late Triassic World . Late Triassic Terrestrial Tetrapods: Biostratigraphy, Biochronology and Biotic Events . Topics in Geobiology . 2018 . 46 . 351–405 . 10.1007/978-3-319-68009-5_10. 978-3-319-68008-8 .
  8. Romano . Carlo . Koot . Martha B. . Kogan . Ilja . Brayard . Arnaud . Minikh . Alla V. . Brinkmann . Winand . Bucher . Hugo . Kriwet . Jürgen . Permian-Triassic Osteichthyes (bony fishes): diversity dynamics and body size evolution . Biological Reviews . February 2016 . 91 . 1 . 106–147 . 10.1111/brv.12161 . 25431138 . 5332637.
  9. Alcober . Oscar A.. Martinez . Ricardo N. . 2010 . A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina . . . . 63 . 55–81 . 10.3897/zookeys.63.550 . 3088398 . 1313-2989 . 21594020. free.
  10. Langer . Max C.. Ramezani . Jahandar . Da Rosa . Átila A.S. . U-Pb age constraints on dinosaur rise from south Brazil . May 2018 . . Amsterdam . Elsevier . 57 . 133–140 . 10.1016/j.gr.2018.01.005 . 2018GondR..57..133L . 1342-937X.
  11. Brusatte . Stephen L. . Stephen L. Brusatte . Benton . Michael J. . Ruta . Marcello . Marcello Ruta . Lloyd . Graeme T. . 2008 . Superiority, Competition, and Opportunism in the Evolutionary Radiation of Dinosaurs . Science . Washington, D.C. . American Association for the Advancement of Science . 321 . 5895 . 1485–1488 . 10.1126/science.1161833 . 2008Sci...321.1485B . 0036-8075 . 18787166 . October 22, 2019. 20.500.11820/00556baf-6575-44d9-af39-bdd0b072ad2b . 13393888 .
  12. Simms, M. J. . Ruffell, A. H. . 1989 . Synchroneity of climatic change and extinctions in the Late Triassic . . 17 . 3 . 265–268 . 10.1130/0091-7613(1989)017<0265:soccae>2.3.co;2 .
  13. Furin, S. . Preto, N. . Rigo, M. . Roghi, G. . Gianolla, P. . Crowley, J.L. . Bowring, S.A. . 2006 . High-precision U-Pb zircon age from the Triassic of Italy: Implications for the Triassic time scale and the Carnian origin of calcareous nanoplankton, lepidosaurs, and dinosaurs . . 34 . 12 . 1009–1012 . 10.1130/g22967a.1.
  14. Olsen . P.E. . Schneider . V. . Sues . H.-D. . Peyer . K.M. . Carter . J.G. . 2001 . Biotic provinciality of the Late Triassic equatorial humid zone . Geological Society of America, Abstracts with Programs . 33 . 2 . A-27.
  15. Book: Curt . Teichert . 1988 . Main Features of Cehalopod Evolution . 12 . Paleontology and Neontology of Cephalopods . 22 October 2013 . M.R. . Clarke . E.R. . Trueman . Academic Press, Harcourt Brace Jovanovich . 9781483275529 . https://books.google.com/books?id=YorgBAAAQBAJ&dq=Curt%20Teichert%201988%2C%20%20Main%20Features%20of%20Cehalopod%20Evolution%20%2C%20in%20The%20Mollusca%20vol.12%2C%20Paleontology%20and%20Neontology%20of%20Cephalopods%2C%20ed.%20by%20M.R.%20Clarke%20%26%20E.R.%20Trueman%2C%20Academic%20Press%2C%20Harcourt%20Brace%20Jovanovich%2C&pg=PP1 . 23 November 2021.
  16. J.P.. Hodych. G.R.Dunning. Did the Manicouagan impact trigger end-of-Triassic mass extinction?. Geology. 20. 1. 1992. 51.54. 10.1130/0091-7613(1992)020<0051:DTMITE>2.3.CO;2. 1992Geo....20...51H .
  17. Ramezani, J., S. A. Bowring, M. S. Pringle, F. D. Winslow, III, and E. T. Rasbury (2005). "The Manicouagan impact melt rock: a proposed standard for intercalibration of U-Pb and 40Ar/39Ar isotopic systems". 15th V.M. Goldsmidt Conference Abstract Volume, p. A321.

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