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65-974: The Raibl Formation is an Upper Triassic geologic formation in the Northern and Southern Limestone mountain ranges of the Eastern Alps , in Central Europe . It preserves fossils dating back to the Norian Middle Triassic sub-period of the Triassic period , during the Mesozoic Era . Upper Triassic 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

130-463: A consequence of redox fluctuations. The ratio of mercury to organic carbon is stronger and occurs earlier in areas corresponding to open marine environments. Although the mercury spikes do not correlate with any indicators of terrestrial runoff, runoff could help maintain high mercury concentrations in the ocean through the CPE. The most parsimonious explanation is that the mercury was initially derived from

195-695: A pulse of volcanic activity, particularly the Wrangellia LIP. This further supports a volcanic cause of the Carnian pluvial episode. Mercury spikes are also found alongside carbon cycle disruptions in both marine and lake sediments in China. These mercury spikes have no trace of mass-independent fractionation , meaning that their isotope distribution is most consistent with fallout from volcanic eruptions. Conodonts , ammonoids , crinoids , bryozoa and green algae experienced high extinction rates during

260-412: A result of oceanic and/or volcanic instability related to the early rifting of Pangea, but at that time direct evidence of this was lacking. Simms and Ruffell published several more papers in the coming years, but their hypothesis was not widely accepted. A strong critique by Visscher et al. (1994) argued that aridity-adapted pollen stayed abundant through the entire Carnian of Germany, suggesting that

325-546: 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

390-455: 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. 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

455-476: 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

520-559: Is also divided into land-vertebrate faunachrons . These are, from oldest to youngest, 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

585-642: 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 . As of 2010 , the base of the Norian has not yet been established, but will likely be based on conodonts. The late Triassic

650-682: Is correlated with major ammonoid and conodont extinctions. Norwegian shale and Japanese chert from the Ladinian-Carnian boundary show a marked change in the ratio of seawater osmium isotopes. The relative abundance of osmium-187 over osmium-188 declines strongly through most of the Julian before rebounding and stabilizing in the Tuvalian. The decline is attributed to early phases of the Wrangellia large igneous province enriching

715-466: Is marked by disruptions to geochemical cycles, most notably the carbon cycle . Sediments corresponding to the base of the episode show a prominent –2 to –4‰ δ C excursion, indicating the release of a lightweight carbon isotope, carbon-12 , into the atmosphere. This excursion was first mentioned regarding carbonates in Israel, and was later reported in more detail from fragments of carbonized wood in

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780-500: Is one of the five major mass extinction events of the Earth. The Triassic was named in 1834 by Friedrich von Alberti , after 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

845-461: Is similar in age to the basalts of the Wrangellia large igneous province (LIP). In the geological record, LIP volcanism is often correlated to episodes of major climate changes and extinctions, which may be caused by pollution of ecosystems with massive release of volcanic gases such as CO 2 and SO 2 . Large release of CO 2 in the atmosphere-ocean system by Wrangellia can explain

910-488: Is very similar to the minimum age calculated for the CPE (≈230.9 million years ago). Ichnofossil comparisons of various tetrapods from before, during and after the CPE suggest an explosive radiation of dinosaurs due to the Carnian humid phase. However, while avemetatarsalian diversity, diversification rate, and size disparity does increase through the Carnian, it increases faster in the Ladinian and Norian, suggesting that

975-550: The Carnian pluvial event , was a period of major change in global climate that coincided with significant changes in Earth's biota both in the sea and on land. It occurred during the latter part of the Carnian Stage, a subdivision of the late Triassic period, and lasted for perhaps 1–2 million years (around 234–232 million years ago). The CPE corresponds to a significant episode in the evolution and diversification of many taxa that are important today, among them some of

1040-596: The Early Cretaceous for amber to occur in concentrations equivalent to or exceeding Carnian amber. Radiolarians increased in their diversity, likely as a result of increased continental weathering amidst the warmth and humidity of the CPE. The first planktonic calcifiers occurred just after the CPE and might have been calcareous dinocysts, i.e., calcareous cysts of dinoflagellates . Coastal ostracod communities in Hungary experienced major changes across

1105-486: 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. 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

1170-694: The United Kingdom 's Mercia Mudstone Group ) are intervals of river sediments enriched with kaolinitic clay and plant debris, despite having been deposited between more arid strata. Humidity-adapted palynomorphs in New Brunswick , karst topography in the U.K., and a carbon isotope excursion in Israel were all reported for the middle of the Carnian prior to 1989. The Julian-Tuvalian boundary experienced high extinction rates among many marine invertebrates, while an extinction among land vertebrates

1235-405: The carbonate compensation depth (CCD) and a crisis of carbonate precipitation (e.g. demise of carbonate platforms in the western Tethys ). On top of all that, the global warming brought on by the flood basalt event was likely exacerbated by the release of methane clathrates. According to an alternative hypothesis, the Carnian pluvial episode was a regional climatic perturbation mostly visible in

1300-480: The CPE was not a major influence on the rise of dinosaurs. The CPE had a profound effect on the diversity and morphological disparity of herbivorous tetrapods. This is exemplified in rhynchosaurs , a group of reptiles with strong shearing and grinding jaws. Rhynchosaur lineages which were common in the Middle Triassic went extinct, leaving only the specialized hyperodapedontines as representatives of

1365-540: The CPE which suggest that global warming was prevalent at the time. This climate change was probably linked to the eruption of extensive flood basalts as the Wrangellia Terrane was accreted onto the northwestern end of the North American Plate . Environmental disturbance and high extinction rates were observed for sediments of the Carnian stage long before a global climate perturbation

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1430-410: The CPE, as well as its relevance for understanding modern climate change. It also attempted to standardize the nomenclature of the CPE; rejecting descriptors such as "event" (typically applied to geological processes under a million years in duration) or "middle Carnian" (a nebulous term with no equivalent geological substage). The Carnian pluvial episode introduced markedly more humid conditions across

1495-508: The CPE, which show an approximately 1.5 ‰ negative shift in the stable isotope δ O , suggesting global warming of 3–4  °C during the CPE and/or a change in seawater salinity . This warming was probably related to extensive volcanic activity at the time, evidenced by carbon isotope trends across the CPE. This volcanic activity was in turn probably related to the formation of the Wrangellia Large igneous province around

1560-499: The CPE. Other organisms radiated and diversified during the interval, such as dinosaurs , calcareous nannofossils , corals and conifers . The CPE has been interpreted as a key geobiological event facilitating the radiation of dinosaurs. The oldest dinosaur-bearing fossil assemblage, the Ischigualasto Formation of Argentina , has been radiometrically dated back to 230.3 to 231.4 million years ago. This age

1625-511: The CPE. Through Julian 2, land-based sediments isolated and filled in marine basins, replacing carbonate-specialists such as bairdiids and healdiids with Bektasia , a platycopid tolerant of shallow siliciclastic seas. Further shallowing across the Julian-Tuvalian boundary left only a few aberrant limnocytherids ( Renngartenella , Simeonella ) and cytherurids ( Kerocythere ) which could manage severe salinity fluctuations in

1690-474: The Dolomites. It has been confirmed in various carbon-based sediments throughout Europe and Asia. More precise stratigraphic evaluation of European outcrops has resolved this excursion into three or possibly four major pulses, spanning the late Julian and early Tuvalian. Each pulse can be equated with an interval of abnormal sedimentation on land and sea. The third excursion, at the Julian-Tuvalian boundary,

1755-634: 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

1820-448: 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

1885-478: The Mercia Mudstone Group to Simms's research on crinoid extinction. A key aspect of their hypothesis was that the evidence used to demonstrate the climate change was entirely independent of the evidence for biotic change; fossils were not used in any way to infer climate change. Their hypothesized climatic disturbance, which they named the Carnian pluvial episode , was tentatively considered to be

1950-506: 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

2015-558: The Schilfsandstein was simply indicative of an invading river system rather than widespread climate change. Their critique also coined the term " Carnian pluvial event ", which would eventually become among the most widespread names for the climatic disturbance. The obscurity of Simms and Ruffell's hypothesis began to dissipate in the late 2000s, as further support accumulated from studies on Carnian sites in Italy . Interest in

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2080-538: 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 is described as semiarid. Semiarid is characterized by light rainfall, having up to 10–20 inches of precipitation

2145-454: 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

2210-503: 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

2275-588: 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. Carnian pluvial episode The Carnian pluvial episode (CPE), often called

2340-399: The Triassic. Conversely, more versatile and generalist herbivores such as aetosaurs and sauropodomorph dinosaurs would diversify after the CPE. Conifers , ferns , and the now-extinct bennettitaleans all diversified greatly during and after the CPE, establishing themselves as mainstays of Mesozoic flora. Most areas show a higher proportion of hygrophytic (moisture-loving) plants during

2405-553: The atmosphere to a more normal state after the CPE. Though tiny amber traces can be found in rocks as old as the Carboniferous , the earliest widespread amber deposits date back to the CPE. Carnian amber droplets from Italian paleosols are the oldest amber deposits known to preserve arthropods and microorganisms . Amber would not reappear in the fossil record until the Late Jurassic , though it would take until

2470-549: The coming years supported a strong link between the Carnian climate disturbances and the Wrangellia large igneous province, but many questions remain unanswered. A geological workshop focusing on the CPE met in 2018 at the Hanse-Wissenschaftskolleg (HWK) Institute for Advanced Study in Delmenhorst, Germany . The workshop was intended to spur further research on the mechanisms, impact and stratigraphy of

2535-465: 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

2600-448: The earliest dinosaurs (which include the ancestors of birds), lepidosaurs (the ancestors of modern-day snakes and lizards) and mammaliaforms (ancestors of mammals). In the marine realm it saw the first appearance among the microplankton of coccoliths and dinoflagellates , with the latter linked to the rapid diversification of scleractinian corals through the establishment of symbiotic zooxanthellae within them. The CPE also saw

2665-406: The early Carnian, were replaced by low-relief carbonate platforms featuring low-angle slopes (i.e., ramps). This turnover is related to a major change in the biological community responsible for calcium carbonate precipitation (i.e. carbonate factory). The highly-productive, mainly bacterial-dominated biological community (M-factory) whose action led to the carbonate production on high-relief platforms

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2730-539: The episode compared to earlier parts of the Triassic. Spores of ferns and freshwater algae are frequently abundant in palynological samples. The Carnian saw the reestablishment of large inland lakes and peat swamps , ending the Early-Middle Triassic " coal gap " caused by the Permian-Triassic mass extinction. Increased plant growth and coal burial probably helped to draw down CO2, returning

2795-588: 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

2860-437: The extinction of many aquatic invertebrate species, especially among the ammonoids , bryozoa , and crinoids . Evidence for the CPE is observed in Carnian strata worldwide and in sediments of both terrestrial and marine environments. On land, the prevailing arid climate across much of the supercontinent Pangea shifted briefly to a hotter and more humid climate, with a significant increase in rainfall and runoff. In

2925-465: The globe, interrupting the otherwise arid climate of the Late Triassic period. This humidity was related to increased rainfall during the CPE evidence of which includes: This usually wet climate of the CPE was periodically interrupted by drier climates typical of the rest of the Late Triassic period. Global warming was also prevalent during the Carnian pluvial event. This is evidenced by oxygen isotope analyses performed on conodont apatite from

2990-546: The group. Immediately after the CPE, hyperodapedontines were widespread and abundant in the late Carnian world, suggesting that they benefited from the climate fluctuations or floral turnover. Hyperodapedontine abundance was not sustained for long, and they too would die out in the early Norian. By cutting rhynchosaurs off from a greater variety of niches, the CPE would have reduced their versatility and increased their vulnerability to extinction. Similar trends are observed in dicynodonts , though they would survive until much later in

3055-649: The hypothesis was greatly enhanced by a 2008 meeting and workshop on Triassic climate at the Museum of Nature South Tyrol in Bolzano, Italy . However, even as the global nature of the CPE became increasingly accepted, its ultimate cause was still hotly debated going into the 2010s. Even its nomenclature was not agreed upon, with various authors applying names such as the middle Carnian wet intermezzo , Carnian humid episode , Carnian pluvial phase , and Carnian crisis . Carbon and Osmium isotope records published over

3120-417: The increased supply of siliciclastic material into basins, as observed during the CPE. The increase of CO 2 in the atmosphere could have resulted in global warming and consequent acceleration of the hydrological cycle, thus strongly enhancing the continental weathering . Moreover, if rapid enough, a sudden rise of pCO 2 levels could have resulted in acidification of seawater with the consequent rise of

3185-399: 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 is associated with this impact. The Rhaetian Age was the final age of the Late Triassic, following

3250-412: The middle and upper Keuper. 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

3315-527: The ocean and continent, and thus generating a monsoon . Summer monsoonal winds were thus intercepted by the Cimmerian mountain range and generated strong rain, thus explaining the switch to humid climate recognized in western Tethys sediments. Highstands in sea level and crises amongst marine organisms during the CPE are closely correlated to maxima in the 1.2-Myr obliquity modulation cycle, suggesting that this Milankovitch cycle regulated biotic turnovers in

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3380-458: The ocean with osmium-188. Osmium-188 is preferentially sourced directly from the mantle, while osmium-187 is a radiogenic isotope supplied from eroded land. In the Alps , moderate to high concentrations of mercury occur alongside carbon cycle disruptions, just prior to the sediment disruption which marks the CPE. These mercury spikes occur in well-oxygenated mudstones, meaning that they are not

3445-431: The oceans there was reduced deposition of carbonate minerals . This may reflect the extinction of many carbonate-forming organisms , but may also be due to a rise in the carbonate compensation depth , below which most carbonate shells dissolve and leave few carbonate particles on the ocean floor to form sediments. Climate change during the Carnian pluvial event is reflected in chemical changes in Carnian strata across

3510-459: 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 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

3575-401: The restricted coastal basins. Bairdiids returned in force at the end of the crisis when the basins deepened, reacquiring carbonate and better ventilation. The recent discovery of a prominent δ C negative shift in higher plants' n-alkanes suggests a massive CO 2 injection in the atmosphere - ocean system at the base of the CPE. The minimum radiometric age of the CPE (≈230.9 Ma)

3640-491: The same time, which created vast quantities of igneous (volcanic) rocks that were accreted onto the northwest end of the North American Plate (now the Wrangell Mountains , Alaska , and an estimated 6km thick layer underlying most of Vancouver Island) There is some evidence for seabed euxinia (no oxygen and high toxic sulfide concentrations) during the CPE. Limestones are enriched in manganese ions near

3705-482: 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

3770-588: The top of the Zhuganpo Formation of south China. Manganese ions are concentrated and soluble in deep euxinic waters, but precipitate in carbonates at the base of the oxygenated zone. Increasing manganese concentrations indicate a narrowing of the oxygenated zone and a corresponding expansion of euxinic water. At the onset of the CPE a sharp change in carbonate platform geometries is recorded in western Tethys . High-relief, mainly isolated, small carbonate platforms surrounded by steep slopes, typical of

3835-571: The western Tethys and related to the uplift of a new mountain range , the Cimmerian orogen , which resulted from the closing of a Tethyan northern branch, east of the present European continent. The new mountain range was forming on the southern side of Laurasia , and acted then as the Himalayas and Asia do today for the Indian Ocean , maintaining a strong pressure gradient between

3900-425: 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

3965-412: 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 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

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4030-445: 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

4095-719: Was proposed. Schlager & Schöllnberger (1974) drew attention to a dark siliciclastic layer which abruptly interrupted a long period of carbonate deposition in the Northern Limestone Alps . They termed this stratigraphic "wende" (turning point) the Reingrabener Wende, and it has also been called the Reingraben event or Raibl event . Several Carnian terrestrial formations (namely the Schilfsandstein of Germany and various members of

4160-514: Was substituted by a less productive mollusc-metazoan-dominated community (C-T factories). In the South China block, the demise of carbonate platforms is coupled with the deposition of sediments typical of anoxic environments (black shales ). Thanks to low oxygen levels, animal remains were often well-preserved in sedimentary deposits called Lagerstätten . These Lagerstätten are rich in crinoids and reptiles, such as ichthyosaurs . The CPE

4225-464: Was suggested to occur in the late Carnian. In 1989, a paper by Michael J. Simms and Alastair H. Ruffell combined these disparate observations into a new hypothesis, pointing to an episode of increased rainfall synchronous with significant ecological turnover in the mid-Carnian. The paper was inspired by a conversation between Simms and Ruffell, on 10 November 1987 at Birmingham University, that connected Ruffell's research on lithological changes in

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