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74-403: The Lunde Formation occurs in the northern part of a Late Triassic continental basin that covered most of the present North Sea area. Several thousands of meters of fluvial sediments were deposited in this basin during a thermal subsidence phase following Late Permian to Early Triassic rifting . With an approximate width of 400 kilometres (250 mi) between present mainland Norway and

148-411: A GSSP). A recent update of Newark stratigraphy by Kent, Olsen, & Muttoni (2017) combined magnetostratigraphy with astrochronology to form the longest astrochronostratigraphic polarity time scale (APTS) known in the fossil record. The Newark sequence was affected by astrochronological ( Milankovitch ) cycles as recorded by climate-induced changes in lake depth and geology, although depositional rate

222-432: 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

296-653: A mountain chain stretching over parts of eastern Switzerland , northern Italy and western Austria . The stage was introduced in scientific literature by Austrian geologist Eduard Suess and German paleontologist Albert Oppel in 1856. In 2010, the Triassic subcommission of the ICS voted that the base of the Rhaetian should be defined by the first appearance of the conodont Misikella posthernsteini . M. posthernsteini 's direct ancestor Misikella hernsteini first appears shortly before

370-656: A pair of Triassic sequences in northern Italy: the Norian-Rhaetian Brumano section and the Rhaetian-Hettangian Italcementi section . In Brumano, M. posthernsteini first appeared quite a distance below the oldest reported magnetozone, BIT1n, which was correlated with E20n at Newark. The opposite is true in Pizzo Mondello, where M. posthersteini appears above the youngest complete magnetozone, PM12n (equivalent to E17n at Newark). This suggests that

444-497: A part of the Black Bear Ridge section of British Columbia which is considered early Rhaetian based on its conodont fauna. Their estimated 205.2 ± 0.9 Ma date for this early Rhaetian section agrees with the results of Wotzlaw et al. (2014). This compromise between "short-Rhaetian" and "long-Rhaetian" hypotheses has been supported by other studies. Maron et al. (2015) elaborated on the dating of an upcoming GSSP candidate for

518-478: A succession of three distinct rock layers (Greek triás 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). The Late Triassic Series corresponds approximately to the middle and upper Keuper. On the geologic time scale , the Late Triassic is usually divided into

592-546: 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

666-758: Is a sequence of the Norian-Rhaetian Calcari con Selce (" Cherty limestone ") Formation named after two nearby towns. It preserves a diverse array of conodonts (including the Misikella hernsteini - posthernsteini morphocline) as well as pronounced radiolarian zones. The top of the Rhaetian (the base of the Hettangian Stage, the Lower Jurassic Series and the Jurassic System) is at the first appearance of ammonite genus Psiloceras . In

740-470: 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

814-463: Is associated with this impact. 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

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888-469: 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

962-507: 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. The Triassic was named in 1834 by Friedrich von Alberti , after

1036-486: Is remarkably consistent within the Newark basin. The most consistent and regular of these cycles are 405,000-year cycles known as McLaughlin cycles. By tracing McLaughlin cycles backwards from the radiometrically-dated CAMP basalts, the boundaries between each formation and magnetozone in the Newark sequence could be assigned a precise age. Magnetozone E20r.2r lasted from 206.03 to 204.65 Ma according to this method, suggesting that

1110-628: Is still much debate over the age of this boundary, as well as the evolution of M. posthernsteini . The most comprehensive source of precise age data for the Late Triassic comes from astrochronologically -constrained terrestrial strata of the Newark basin in the eastern United States. Correlating the Newark basin to marine sections encompassing the Norian-Rhaetian boundary is mainly achieved via magnetostratigraphy , though such correlations are subject to debate and revision. Some authors have suggested that

1184-812: Is the latest age of the Triassic Period (in geochronology ) or the uppermost stage of the Triassic System (in chronostratigraphy ). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest age of the Jurassic ). The base of the Rhaetian lacks a formal GSSP , though candidate sections include Steinbergkogel in Austria (since 2007) and Pignola-Abriola in Italy (since 2016). The end of

1258-596: The Berdyankian , Otischalkian , Adamanian , Revueltian and Apachean . 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

1332-538: The Shetland Platform , the continental post-rift basin contains the Teist , Lomvi and Lunde Formations, and lasted throughout the Triassic until the final depositional stages of the overlying latest Triassic to Early Jurassic Statfjord Formation , when the whole area was flooded during a marine transgression from the north and south in late Sinemurian to early Pliensbachian times. The climate during deposition of

1406-574: The "short-Rhaetian" hypothesis have been revived by radiometric dating of Peruvian bivalve extinctions and magnetostratigraphy at the Pignola-Abriola GSSP candidate. These studies suggest that the base of the Rhaetian was close to 205.5 Ma. During the Rhaetian, Pangaea began to break up, though the Atlantic Ocean was not yet formed. The Rhaetian is named after the Rhaetian Alps ,

1480-451: 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 . As of 2010 , the base of the Norian has not yet been established, but will likely be based on conodonts. The late Triassic is also divided into land-vertebrate faunachrons . These are, from oldest to youngest,

1554-516: 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

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1628-520: The ICS Triassic subcommission had already voted in 2010 to certify the first appearance of M. posthernsteini as the defining event for the base of the Rhaetian. Partially inspired by the work of Hüsing et al . (2011), the ICS's 2012 Geologic Time Scale utilized a tentative 208.5 Ma date for the Norian-Rhaetian boundary. This date has been retained in ICS time scales as of 2020. The Norian-Rhaetian boundary

1702-683: The Kiritehere section of New Zealand). It was construed to be related to the same event responsible for the Norian-Rhaetian extinction, which heavily impacted ammonoids, bivalves, conodonts, and radiolarians. The Norian-Rhaetian extinction may have been caused by the eruption of the Angayucham large igneous province in Alaska , or the asteroid responsible for the Rochechouart impact structure in France . However,

1776-625: 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

1850-469: The Lunde Formation was semiarid and highly seasonal, typical for the contemporary palaeogeographic position at 40-50 degrees North paleolatitude. The basin was linked to a marine borealic seaway, probably located some tens to hundreds of kilometers to the north and to provenance areas composed of Archean gneisses , Caledonian metamorphic rocks and Devonian sandstones . These sources located on

1924-568: The Lunde Formation. The mudstone is composed of dominantly compound and cumulative paleosols that formed in distal to fluvial channels in a floodplain forming the uppermost part of the upper member of the Lunde Formation. The paleosols are characterized by carbonate nodules, pedogenic mud aggregates and slickensides , mottling, root traces and mud cracks . The paleosol type is similar to modern vertisols forming in semi-arid areas with seasonal precipitation, commonly with dry periods lasting 4–8 months. The presence of root traces suggests that

1998-412: The Norian-Rhaetian boundary lies in the range of Newark magnetozones E17r to E19r, or 207-210 Ma. The authors expressed skepticism towards the substantial overlap between Oyuklu and Pizzo Mondello proposed by Gallet et al. (2007). Hounslow & Muttoni (2010) elaborated on this sentiment and correlated section A+ of Oyuklu with PM12n of Pizzo Mondello, indicating that the overlap between the two sections

2072-566: The Norian-Rhaetian boundary occurred somewhere between these ash beds, 205.50 ± 0.35 Ma. This date corresponds to "short-Rhaetian" predictions, but Wotzlaw et al. (2014) also agreed with "long-Rhaetian" proponents who argued that there was no good evidence for a hiatus in the Newark Basin sequence. Wotzlaw et al . (2014) estimated that the Norian-Rhaetian boundary was concurrent with a lengthy reverse polarity section (E20r.2r) of Newark magnetozone E20. Golding et al . (2016) utilized U-Pb dating at

2146-419: The Rhaetian (and the base of the overlying Hettangian Stage) is more well-defined. According to the current ICS (International Commission on Stratigraphy) system, the Rhaetian ended 201.4 ± 0.2 Ma ( million years ago ). In 2010, the base of the Rhaetian (i.e. the Norian-Rhaetian boundary) was voted to be defined based on the first appearance of Misikella posthernsteini , a marine conodont . However, there

2220-515: The Rhaetian began ~205.5 Ma. This agrees with the dates for the Norian-Rhaetian boundary obtained by Wotzlaw et al. (2014) and Maron et al. (2015). The accuracy of the Newark APTS has been supported by Li et al. (2017), who found astrochronological and magnetostratigraphic signatures in the Xujiahe Formation of China practically identical to those of the Newark sequence. The end date of

2294-516: The Rhaetian currently in use by the ICS (201.3 ±0.2 Ma) is based on a study by Schoene et al . (2010) involving ammonite -bearing strata in Peru . They used CA-ID-TIMS Uranium-Lead dating to date ash beds slightly below and slightly above the first appearance of Psiloceras in the Pucará Basin . The overlying ash bed was dated to 201.29 ±0.16 Ma while the underlying was 201.36 ±0.13 Ma. This allowed

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2368-651: The Rhaetian in the form of the Pignola-Abriola section in Southern Italy. This section recorded the Norian-Rhaetian boundary as tracked by the first occurrence of Misikella posthernsteini , the base of the Proparvicingula moniliformis radiolarian zone, and a prominent negative δ C anomaly. Magnetostratigraphy correlated MPA5r (the Pignola-Abriola magnetozone surrounding the Norian-Rhaetian boundary) with

2442-484: The Rhaetian lasted less than 5 million years using magnetostratigraphy from Turkish strata and a presumed gap or unconformity in Newark strata. However, both of these lines of evidence have been met with skepticism. A commonly cited approximation of 208.5 Ma (used by the ICS since 2012) is based on a "long-Rhaetian" hypothesis reconstructed from the Steinbergkogel GSSP candidate. Most recently, aspects of

2516-465: The Rhaetian lasts under 5 million years) based on the Oyuklu section , a sequence from Turkey . This sequence was largely normal-polarity dominated, and presented two potential Norian-Rhaetian boundaries (since the defining biostratigraphy of the Rhaetian was not resolved at the time). Defining the boundary based on the appearance of Misikella posthernsteini placed it in a reverse-polarity section (B−) near

2590-626: The Shetland Platform and in the southwestern area of Norway and deposited into a vast alluvial plain in the Triassic of what is now the North Sea. The bone slice of Plateosaurus was discovered during the description of a core retrieved in February 1997 from well 34/4-9S in the north-western part of the Snorre Field . It occurs in a reddish-brown, mudstone interval referred to as the upper member of

2664-732: The Tethyan domain, the Rhaetian contains two ammonite biozones. The highest ammonite biozone is that of Choristoceras marshi , the lower one that of Rhabdoceras suesii . The end of this period is marked by the Triassic-Jurassic extinction event . The GSSP marking the beginning of the Hettangian (and the end of the Rhaetian) is located at Kuhjoch, a geological section near the base of the Kendelbach Formation in Austria . This site records

2738-503: 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. Most of

2812-530: 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. Rhaetian The Rhaetian

2886-468: The base of Oyuklu. Defining the boundary based on the extinction of Epigondolella bidentata placed it at magnetozone G+, the first of several major normal-polarity sections. The early reverse-polarity zones (B− to D−) were correlated with PM11r, a reverse-polarity section at the top of Pizzo Mondello , a similar Carnian-Norian sequence in Sicily . The inferred overlap between these reverse-polarity sections

2960-510: The base of the Rhaetian. In the boreal domain (i.e. the area of the Northern ocean), the base of the Cochloceras (Paracochloceras) amoenum biozone is used instead. Extinctions at the beginning of the Rhaetian include the ammonite Metasibirites and almost all species of the large bivalve Monotis , which was abundant throughout the world in the Norian but only persisted into the Rhaetian in

3034-607: The biostratigraphers who argue in favor of a Newark hiatus use similar techniques to support a "long Tuvalian" hypothesis, in which the Tuvalian (late Carnian) extends into a period of time commonly believed to be early Norian. When the International Commission on Stratigraphy updated their Geologic Time Scale in 2012, the "short Rhaetian" and "long Tuvalian" hypotheses were equated with each other. The combined "short Rhaetian/long Tuvalian" hypothesis as described by Ogg (2012)

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3108-587: The boundary. Around the same time is the first occurrence of the more extravagant conodont species Epigondolella mosheri ( also called Mockina mosheri), which may be used as a proxy in areas where M. posthernsteini is uncommon or occurs later in time than it does elsewhere. In the Tethyan domain (i.e. the area of the Tethys ocean), the Sagenites reticulatus and Paracochloceras suessi ammonite biozones begin at

3182-434: The conodonts Misikella hernsteini and M. posthernsteini (sensu lato) and the ammonoid Paracochloceras suessi . It also record the extinction of large Monotis bivalves and the disappearance of ammonoids including Metasibirites and some Sagenites forms with lateral nodes. A second formal GSSP candidate was not provided until Rigo et al. (2015) proposed the Pignola-Abriola section of southern Italy . This

3256-473: The dating of these geological events and their effects on life are uncertain at best. The Rhaetian does not yet have an official GSSP, but two candidates have been formally proposed. Krystyn et al. (2007) proposed the Austrian Steinbergkogel section, a Norian-Rhaetian limestone sequence near Hallstatt . It records many potential Norian-Rhaetian biostratigraphic events, such as the appearance of

3330-407: The dinosaurs gradually began to displace. 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. The Norian is the second age of the Late Triassic, covering

3404-465: 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 reptile did not survive through this age. During the beginning of the Triassic Period, the Earth consisted of

3478-465: 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 . 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

3552-480: The early M. posthernsteini specimens present at Steinbergkogel are actually an older transitional form ( M. posthernsteini sensu lato) which lies between M. hernsteini and M. posthernsteini in the evolution of Triassic conodonts. The Pignola-Abriola form ( M. posthernsteini sensu stricto) is considered morphologically more similar to the original fossils of the species, described from Slovakia in 1974. This debate has led some biostratigraphers to suggest avoiding

3626-414: The early part of Newark's E20. This provided an estimated date of 205.7 Ma for the Norian-Rhaetian boundary, very similar to Wotzlaw et al. (2014)'s estimate. Some controversy over the date of the Norian-Rhaetian boundary has resulted from differing interpretations of the conodont used to define it, Misikella posthernsteini . Paleontologists working on the Pignola-Abriola GSSP candidate have argued that

3700-519: 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. The Late Triassic

3774-574: 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

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3848-760: The first CAMP eruptions. However, the lithology and astrochronology of Newark seem to be continuous and this precludes any assumed unconformity. In addition, the magnetic signature of at the end of Newark basin has been found worldwide, with sequences in Morocco, Nova Scotia, Italy, the U.K., and possibly Turkey all preserving E23r-equivalent magnetozones underlying the Rhaetian-Hettangian boundary. It would be very improbable for all of these sites of varying geology and deposition rates to experience an unconformity erasing an equivalent amount of time. Kent, Olsen, & Muttoni (2017) additionally found convincing correlations between

3922-647: The first appearance of Misikella posthernsteini (sensu stricto) and the Proparvicingula moniliformis radiolarian zone. Rigo et al. (2020) found this same pattern in the nearby Mt Volturino and Madonna del Sirino sections, as well as the Kastelli section of Greece. They also found it in East Panthalassan sediments (Kennecott Point of British Columbia and New York Canyon of Nevada) and West Panthalassan sediments (Wombat and northern Carnarvon Basins of Australia and

3996-449: The first appearance of Psiloceras to be given a date of 201.31 ±0.18/0.43 Ma (assuming minimum/maximum uncertainty). Blackburn et al . (2013) instead estimated a slightly older end date. They used a combination of radiometric dates and astrochronology (via Triassic Milankovitch cycles ) to constrain the end-Triassic extinction to 201.564 ±0.015/0.22 Ma. The biostratigraphically-defined Triassic-Jurassic (Rhaetian-Hettangian) boundary

4070-472: The first appearance of Psiloceras spelae , Cerebropollenites thiergartii (a palynomorph ), Praegubkinella turgescens (a foraminifer ), Cytherelloidea buisensis (an ostracod ), and a positive δ C spike marking a recovery from the underlying large negative δ C spike which marks the Triassic-Jurassic extinction event. Gallet et al . (2007) argued in support of a "short Rhaetian" (where

4144-403: The floodplain was covered with small trees and bushes, vegetation suitable for herbivorous animals living on the alluvial plain. Beds containing the bone specimen belong to the younger of two palynomorph assemblages containing the spore Kreuselisporites reissingeri thought to indicate an early Rhaetian rather than a Norian age, corresponding approximately to an age of 203-202 Ma according to

4218-430: The form of a few miniaturized species endemic to the Tethys ocean. The Norian-Rhaetian boundary also experienced an overturn in radiolarian species, with the beginning of the Proparvicingula moniliformis biozone. Maron et al. (2015) provided a chemostratigraphic option for defining the base of the Rhaetian at the Pignola-Abriola section. This sequence records a pronounced negative spike in δ C just before

4292-483: The hiatus. Estimating the duration of Oyuklu by comparing Pizzo Mondello with equivalent sections of Newark led Gallet et al . (2007) to the conclusion that the Rhaetian lasted only 2 million years (if the boundary was at G+) or 4.5 million years (if it was at B−). Some biostratigraphic studies have also supported a hiatus at Newark. The conchostracan Shipingia olseni , which in Europe is found in Norian rocks, occurs in

4366-534: The magnetozones of the upper Passaic Formation and Rhaetian strata in England. They suggest that the apparent delay between Newark and Europe fauna and flora may instead be biogeographic differences due to climatic variation over time and latitude, a factor which has manifested at other points in the Triassic. Various studies have supported a "long Rhaetian" hypothesis (where the Rhaetian lasts 5–10 million years) based on magnetostratigraphy. Muttoni et al. (2010) studied

4440-527: The neopterygians, stem-group teleosts and the now extinct Pycnodontiformes became more abundant in the Late Triassic. 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. They emerged in a world dominated by crurotarsan archosaurs (ancestors of crocodiles ), predatory phytosaurs , herbivorous armored aetosaurs , and giant carnivorous rauisuchians , which

4514-514: 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. 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

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4588-477: 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

4662-502: 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

4736-525: 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. However crurotarsans continued to occupy more ecological niches than dinosaurs. In the oceans, neopterygian fish proliferated at the expense of ceratitid ammonites. The Manicouagan impact event occurred 214 million years ago. However, no extinction event

4810-608: The time scale of Gradstein et al. (2005). Late Triassic The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale , spanning the time between 237 Ma and 201.4 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

4884-437: The top of a normal-polarity section while M. posthernsteini (sensu lato) first appeared at the base of a shorter overlying reverse-polarity section. These sections were correlated with magnetozones E16n and E16r of the Newark Basin. Hüsing et al . (2011) preferred to define the Rhaetian based on M. hernsteini , and estimated a date for the Norian-Rhaetian boundary of 209.8 Ma based on that of Newark's magnetozone E16n. However,

4958-666: The upper portion of the Passaic Formation , the last pre- CAMP section of the Newark basin. Typical Rhaetian conchostracans such as Euestheria brodieana only appear in the last few layers of the Catharpin Creek Formation , a late Triassic unit in the Culpeper Basin which is likely equivalent to the upper Passaic formation. Palynomorph turnovers and changes in tetrapod faunas similar to Norian events in Europe have also been used to support this hypothesis. Many of

5032-415: The use of conodonts in Triassic chronostratigraphy altogether, a proposal which itself has been criticized by Triassic conodont specialists. Writing on behalf of the ICS, Ogg (2016) stated that there were two possible dates for the Norian-Rhaetian boundary: 209.5 Ma (using M. posthernsteini sensu lato and Steinbergkogel as a GSSP) or 205.8 Ma (using M. posthernsteini sensu stricto and Pignola-Abriola as

5106-426: Was a missing period of time or "hiatus" at the end of the Newark sequence, which would have resembled part of Oyuklu had it not been eroded away. If the base of Oyuklu (A+) was equivalent to E21n, then the upper half of Oyuklu would be equivalent to the Newark "hiatus", B− was equivalent to E21r, and G+ was equivalent to E23n. If A+ was instead equivalent to E23n, then practically all of Oyuklu (B− and up) would represent

5180-572: Was a prominent study arguing in favor of a long Rhaetian. This was based on biostratigraphy and magnetostratigraphy of the Steinbergkogel section in Austria, which is a candidate GSSP for the base of the Rhaetian. They proposed two options for defining the base of the Rhaetian, either at the first occurrence of Misikella hernsteini or the first appearance datum of Misikella posthernsteini (sensu lato) . At Steinbergkogel, M. hernsteini first occurred at

5254-514: Was finally provided with radiometric dating in a study by Wotzlaw et al. (2014). They studied a sequence of the Aramachay Formation in Peru which records the extinction of large Monotis bivalves . This prominent biotic event is closely associated with the Norian-Rhaetian boundary. The last Monotis specimens lie between ash beds which are Uranium-Lead dated to 205.70 ± 0.15 Ma and 205.30 ± 0.14 Ma. This allowed them to conclude that

5328-571: Was located above a normal-polarity section (A+ in Oyuklu and PM11n in Pizzo Mondello). This underlying normal-polarity section was correlated with either magnetozone E21n or E23n of the Newark sequence. Although the upper portion of Oyuklu was mostly normal, it did have a few reverse sections (H− and J−) which were at odds with the almost entirely-normal last few Triassic magnetozones of Newark. Gallet et al. (2007) explained this by suggesting that there

5402-407: Was ultimately not chosen by the ICS when compared to its competition, which was supported by a more diverse array of methods. The "short Rhaetian" hypothesis has been criticized for its reliance on the assumption that a hiatus existed at Newark. This hiatus was presumed to lie within the normal polarity-dominated end of the Rhaetian, after a very short reverse polarity section (E23r) and just before

5476-486: Was very narrow. They also noted that a thrust fault at Oyuklu artificially lengthens B−, the magnetozone containing the Norian-Rhaetian boundary at that section. Ikeda & Tada (2014) provided an astrochronologically -constrained chert sequence in Japan which suggested that the Norian-Rhaetian boundary occurred 208.5 ± 0.3 Ma, based on the extinction of the Norian radiolarian Betraccium deweveri . Hüsing et al . (2011)

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