Misplaced Pages

#667332

163-724: The start of the Jurassic was marked by the major Triassic–Jurassic extinction event , associated with the eruption of the Central Atlantic Magmatic Province (CAMP). The beginning of the Toarcian Age started around 183 million years ago and is marked by the Toarcian Oceanic Anoxic Event , a global episode of oceanic anoxia , ocean acidification , and elevated global temperatures associated with extinctions, likely caused by

326-444: A 'seed', such as a piece of a shell. Strong intertidal currents wash the 'seeds' around on the seabed, where they accumulate layers of chemically precipitated calcite from the supersaturated water. The oolites are commonly found in large current bedding structures that resemble sand dunes. The size of the oolites reflect the time that they were exposed to the water before they were covered with later sediment. Oolites are often used in

489-653: A 70 km diameter impact structure buried beneath the Kalahari desert in northern South Africa. The impact is dated to the Tithonian, approximately 146.06 ± 0.16 Mya. Another major structure is the Puchezh-Katunki crater , 40 kilometres in diameter, buried beneath Nizhny Novgorod Oblast in western Russia. The impact has been dated to the Sinemurian, 195.9 ± 1.0 Ma. At the beginning of the Jurassic, all of

652-576: A biological turnover where modern groups of fish started to supplant earlier groups. Pycnodontiform fish were insignificantly affected. Conodonts , which were prominent index fossils throughout the Paleozoic and Triassic, finally became extinct at the T-J boundary following declining diversity. Like fish, marine reptiles experienced a substantial drop in diversity between the Middle Triassic and

815-518: A bolide impact have been found in the late Rhaetian, though not at the Triassic-Jurassic boundary itself; the discoverers of these trace metal anomalies purport that such a bolide impact could only have been an indirect cause of the TJME. The discovery of seismites two to four metres thick coeval with the carbon isotope fluctuations associated with the TJME has been interpreted as evidence of

978-539: A cause of extinction events were dismissed as catastrophism. Consequently, gradual environmental changes were favoured as the cause of the extinction. In the 1980s, Jack Sepkoski identified the Triassic-Jurassic boundary drop in biodiversity as one of the "Big 5" mass extinction events. After the discovery that the Cretaceous-Palaeogene extinction event was caused by a bolide impact, the TJME has also been suggested to have been caused by such an impact in

1141-547: A clear trend towards increased aridification towards the end of the Triassic. Although high-latitude areas like Greenland and Australia actually became wetter, most of the world experienced more drastic changes in climate as indicated by geological evidence. This evidence includes an increase in carbonate and evaporite deposits (which are most abundant in dry climates) and a decrease in coal deposits (which primarily form in humid environments such as coal forests ). In addition,

1304-555: A collapse in the reef community, which was likely driven by ocean acidification resulting from CO 2 supplied to the atmosphere by the CAMP eruptions. Most evidence points to a relatively fast recovery from the mass extinction. Benthic ecosystems recovered far more rapidly after the TJME than they did after the PTME. British Early Jurassic benthic marine environments display a relatively rapid recovery that began almost immediately after

1467-497: A dominant component of Jurassic floras. The Late Triassic and Jurassic was a major time of diversification of conifers, with most modern conifer groups appearing in the fossil record by the end of the Jurassic, having evolved from voltzialean ancestors. Araucarian conifers have their first unambiguous records during the Early Jurassic, and members of the modern genus Araucaria were widespread across both hemispheres by

1630-459: A few sites, the TJME was associated with fully oxygenated waters. Positive δ N excursions have also been interpreted as evidence of anoxia concomitant with increased denitrification in marine sediments in the TJME's aftermath. In northeastern Panthalassa, episodes of anoxia and euxinia were already occurring during the Rhaetian before the TJME, making its marine ecosystems unstable even before

1793-645: A kink in one of the plate boundaries, resulting in the formation of the Pacific Plate at the centre of the junction. During the Middle to early Late Jurassic, the Sundance Seaway , a shallow epicontinental sea , covered much of northwest North America. The eustatic sea level is estimated to have been close to present levels during the Hettangian and Sinemurian, rising several tens of metres during

SECTION 10

#1732758187668

1956-875: A lot of surface area, which promotes high bacterial growth. Some exemplar oolitic limestone was formed in England during the Jurassic period, and forms the Cotswold Hills , the Isle of Portland with its famous Portland Stone , and part of the North York Moors . A particular type, Bath Stone , gives the buildings of the World Heritage City of Bath their distinctive appearance. Carboniferous Hunts Bay Oolite lies under much of south Wales . The Miami Rock Ridge of southeastern Florida,

2119-441: A positive feedback resulting from warming, which has been suggested as one possible cause of the PTME, the largest mass extinction of all time, may have exacerbated greenhouse conditions, although others suggest that methane hydrate release was temporally mismatched with the TJME and thus not a cause of it. Besides the carbon dioxide-driven long-term global warming, CAMP volcanism had shorter term cooling effects resulting from

2282-513: A possible bolide impact, although no definitive link between these seismites and any impact event has been found. On the other hand, the dissimilarity between the isotopic perturbations characterising the TJME and those characterising the end-Cretaceous mass extinction makes an extraterrestrial impact highly unlikely to have been the cause of the TJME, according to many researchers. Various trace metal ratios, including palladium/iridium, platinum/iridium, and platinum/rhodium, in rocks deposited during

2445-487: A pronounced negative δ U excursion, indicating a major decrease in marine oxygen availability. Isorenieratane concentration increase reveals that populations of green sulphur bacteria , which photosynthesise using hydrogen sulphide instead of water, grew significantly across the Triassic-Jurassic boundary; these findings indicate that euxinia , a form of anoxia defined by not just the absence of dissolved oxygen but high concentrations of hydrogen sulphide , also developed in

2608-452: A result of high ocean acidity and temperature inhibiting its mineralisation into apatite; the abundance of phosphorus in marine environments caused further eutrophication and consequent anoxia in a positive feedback loop. The end-Jurassic transition was originally considered one of eight mass extinctions, but is now considered to be a complex interval of faunal turnover, with the increase in diversity of some groups and decline in others, though

2771-522: A role in the ecological crisis. Geological formations in Europe and the Middle East seem to indicate a drop in sea levels at the end of the Triassic associated with the TJME. Although falling sea levels have sometimes been considered a culprit for marine extinctions, evidence is inconclusive since many sea level drops in geological history are not correlated with increased extinctions. However, there

2934-494: A sharp, very rapid decline followed by an adaptive radiation, a more gradual turnover in both fossil plants and spores with several intermediate stages is observed over the course of the extinction event. Extinction of plant species can in part be explained by the suspected increased carbon dioxide in the atmosphere as a result of CAMP volcanic activity, which would have created photoinhibition and decreased transpiration levels among species with low photosynthetic plasticity, such as

3097-491: A significant decrease of seawater pH known as ocean acidification , which is discussed as a relevant driver of marine extinction. Evidence for ocean acidification as an extinction mechanism comes from the preferential extinction of marine organisms with thick aragonitic skeletons and little biotic control of biocalcification (e.g., corals, hypercalcifying sponges), which resulted in a coral reef collapse and an early Hettangian "coral gap". The decline of megalodontoid bivalves

3260-594: A widespread effect on the planet; a 214-million-year-old ejecta blanket of shocked quartz has been found in rock layers as far away as England and Japan. There is still a possibility that the Manicouagan impact was responsible for a small extinction midway through the Late Triassic at the Carnian–Norian boundary, although the disputed age of this boundary (and whether an extinction actually occurred in

3423-491: Is Austrohamia minuta from the Early Jurassic (Pliensbachian) of Patagonia, known from many parts of the plant. The reproductive structures of Austrohamia have strong similarities to those of the primitive living cypress genera Taiwania and Cunninghamia . By the Middle to Late Jurassic Cupressaceae were abundant in warm temperate–tropical regions of the Northern Hemisphere, most abundantly represented by

SECTION 20

#1732758187668

3586-424: Is also attributed to increased seawater acidity. Extensive fossil remains of malformed calcareous nannoplankton, a common sign of significant drops in pH, have also been extensively reported from the Triassic-Jurassic boundary. Global interruption of carbonate deposition at the Triassic-Jurassic boundary has been cited as additional evidence for catastrophic ocean acidification. Upwardly developing aragonite fans in

3749-996: Is also found in Indiana in the United States . The town of Oolitic, Indiana , was founded for the trade in limestone and bears its name. Quarries in Oolitic, Bedford , and Bloomington contributed the materials for such U.S. landmarks as the Empire State Building in New York and the Pentagon in Arlington, Virginia . Many of the buildings on the Indiana University campus in Bloomington are built with native oolitic limestone material, and

3912-513: Is believed to have resulted in increased storminess and lightning activity as a consequence of the more humid climate. The uptick in lightning activity is in turn implicated as a cause of an increase in wildfire activity. The combined presence of charcoal fragments and heightened levels of pyrolytic polycyclic aromatic hydrocarbons in Polish sedimentary facies straddling the Triassic-Jurassic boundary indicates wildfires were extremely commonplace during

4075-523: Is difficult, as the last stage of the Triassic, the Rhaetian, and the first stage of the Jurassic, the Hettangian , each have few records of large land animals; some paleontologists have considered only phytosaurs and procolophonids to have become extinct at the Triassic–Jurassic boundary, with other groups having become extinct earlier. However, it is likely that many other groups survived up until

4238-494: Is divided into three epochs : Early, Middle, and Late. Similarly, in stratigraphy , the Jurassic is divided into the Lower Jurassic , Middle Jurassic , and Upper Jurassic series . Geologists divide the rocks of the Jurassic into a stratigraphic set of units called stages , each formed during corresponding time intervals called ages. Stages can be defined globally or regionally. For global stratigraphic correlation,

4401-562: Is followed by the Kimmeridgian Warm Interval (KWI) between 164 and 150 million years ago. Based on fossil wood distribution, this was one of the wettest intervals of the Jurassic. The Pangaean interior had less severe seasonal swings than in previous warm periods as the expansion of the Central Atlantic and Western Indian Ocean provided new sources of moisture. A prominent drop in temperatures occurred during

4564-468: Is fourth order, with a periodicity of approximately 410,000 years. During the Early Jurassic the world's oceans transitioned from an aragonite sea to a calcite sea chemistry, favouring the dissolution of aragonite and precipitation of calcite . The rise of calcareous plankton during the Middle Jurassic profoundly altered ocean chemistry, with the deposition of biomineralized plankton on

4727-618: Is linked to the Jura Mountains , a forested mountain range that mainly follows the France–Switzerland border . The name "Jura" is derived from the Celtic root * jor via Gaulish *iuris "wooded mountain", which was borrowed into Latin as a name of a place and evolved into Juria and finally Jura . During a tour of the region in 1795, German naturalist Alexander von Humboldt recognized carbonate deposits within

4890-471: Is marked by a globally documented high amplitude negative carbon isotope excursion, as well as the deposition of black shales and the extinction and collapse of carbonate-producing marine organisms, associated with a major rise in global temperatures. The TOAE is often attributed to the eruption of the Karoo-Ferrar large igneous provinces and the associated increase of carbon dioxide concentration in

5053-577: Is named after the city of Oxford in England and was named by Alcide d'Orbigny in 1844 in reference to the Oxford Clay . The base of the Oxfordian lacks a defined GSSP. W. J. Arkell in studies in 1939 and 1946 placed the lower boundary of the Oxfordian as the first appearance of the ammonite Quenstedtoceras mariae (then placed in the genus Vertumniceras ). Subsequent proposals have suggested

Jurassic - Misplaced Pages Continue

5216-443: Is not universally accepted that even this local diversity drop was caused by sea level fall. A pronounced sea level change in latest Triassic records from Lake Williston in northeastern British Columbia , which was then the northeastern margin of Panthalassa, resulted in an extinction event of infaunal (sediment-dwelling) bivalves, though not epifaunal ones. Some have hypothesized that an impact from an asteroid or comet caused

5379-480: Is still some evidence that marine life was affected by secondary processes related to falling sea levels, such as decreased oxygenation (caused by sluggish circulation), or increased acidification. These processes do not seem to have been worldwide, with the sea level fall observed in European sediments believed to be not global but regional, but they may explain local extinctions in European marine fauna. However, it

5542-703: Is the setting of the world's largest oil reserves, including the Ghawar Field , the world's largest oil field. The Jurassic-aged Sargelu and Naokelekan formations are major source rocks for oil in Iraq . Over 1500 gigatons of Jurassic coal reserves are found in north-west China, primarily in the Turpan-Hami Basin and the Ordos Basin . Major impact structures include the Morokweng impact structure ,

5705-565: Is used to mark the beginnings of stages, as well as smaller timespans within stages, referred to as "ammonite zones"; these, in turn, are also sometimes subdivided further into subzones. Global stratigraphy is based on standard European ammonite zones, with other regions being calibrated to the European successions. The oldest part of the Jurassic Period has historically been referred to as the Lias or Liassic, roughly equivalent in extent to

5868-515: The Central Atlantic Magmatic Province (CAMP), the largest known large igneous province by area, and one of the most voluminous, with its flood basalts extending across parts of southwestern Europe, northwestern Africa, northeastern South America, and southeastern North America. The coincidence and synchrony of CAMP activity and the TJME is indicated by uranium-lead dating , argon-argon dating , and palaeomagnetism . The isotopic composition of fossil soils and marine sediments near

6031-618: The Central Atlantic Magmatic Province (CAMP), which released large amounts of carbon dioxide into the Earth's atmosphere, causing profound global warming along with ocean acidification . Older hypotheses have proposed that gradual climate or sea level change may be the culprit, or perhaps one or more asteroid strikes. The earliest research on the TJME was conducted in the mid-20th century, when events in earth history where widely assumed to have been gradual (a paradigm known as uniformitarianism ) and comparatively rapid cataclysms as

6194-479: The Industrial Revolution . The degassing rate of the first pulse of CAMP volcanism is estimated to have been around half of the rate of modern anthropogenic emissions. Palaeontologists studying the TJME and its impacts warn that a major reduction in humanity's carbon dioxide emissions to slow down climate change is of critical importance for preventing a catastrophe similar to the TJME from befalling

6357-511: The International Commission on Stratigraphy (ICS) ratify global stages based on a Global Boundary Stratotype Section and Point (GSSP) from a single formation (a stratotype ) identifying the lower boundary of the stage. The ages of the Jurassic from youngest to oldest are as follows: Jurassic stratigraphy is primarily based on the use of ammonites as index fossils . The first appearance datum of specific ammonite taxa

6520-548: The Middle Triassic . Though this may have been due to falling sea levels or the Carnian Pluvial Event , it may instead be a result of sampling bias considering that Middle Triassic fish have been more extensively studied than Late Triassic fish. Despite the apparent drop in diversity, neopterygiians (which include most modern bony fish) suffered less than more "primitive" actinopterygiians, indicating

6683-727: The Redcar Mudstone Formation , and was ratified in 2005. The beginning of the Pliensbachian is defined by the first appearance of the ammonite Bifericeras donovani . The village Thouars (Latin: Toarcium ), just south of Saumur in the Loire Valley of France , lends its name to the Toarcian Stage. The Toarcian was named by Alcide d'Orbigny in 1842, with the original locality being Vrines quarry around 2 km northwest of Thouars. The GSSP for

Jurassic - Misplaced Pages Continue

6846-769: The Sichuan Basin , relatively cool mixed forests in the late Rhaetian were replaced by hot, arid fernlands during the Triassic–Jurassic transition, which in turn later gave way to a cheirolepid-dominated flora in the Hettangian and Sinemurian. The abundance of ferns in China that were resistant to high levels of aridity increased significantly across the Triassic–Jurassic boundary, though ferns better adapted for moist, humid environments declined, indicating that plants experienced major environmental stress, albeit not an outright mass extinction. In some regions, however, major floral extinctions did occur, with some researchers challenging

7009-493: The 1980s and 1990s. The theory that the TJME was caused by massive volcanism in the Central Atlantic Magmatic Province (CAMP) first emerged in the 1990s after similar research examining the Permian-Triassic extinction event found it to have been caused by volcanic activity. Despite some early objections, this paradigm remains the scientific consensus in the present day. The Triassic-Jurassic extinction completed

7172-413: The 21st century. In addition, the flood basalts intruded through sediments that were rich in organic matter and combusted it, which led to the degassing of volatiles that further enhanced volcanic warming of the climate. Thermogenic carbon release through such contact metamorphism of carbon-rich deposits has been found to be a sensible hypothesis providing a coherent explanation for the magnitude of

7335-579: The 9 km (6 mi) wide Red Wing Creek structure in North Dakota . Spray et al. (1998) noted an interesting phenomenon, that being how the Manicouagan, Rochechouart, and Saint Martin craters all seem to be at the same latitude, and that the Obolon' and Red Wing craters form parallel arcs with the Rochechouart and Saint Martin craters, respectively. Spray and his colleagues hypothesized that

7498-630: The Aalenian, precessionally forced climatic changes dictated peatland wildfire magnitude and frequency. The European climate appears to have become noticeably more humid at the Aalenian-Bajocian boundary but then became more arid during the middle Bajocian. A transient ice age possibly occurred in the late Bajocian. The Callovian-Oxfordian boundary at the end of the MJCI witnessed particularly notable global cooling, potentially even an ice age. This

7661-747: The Bajocian Stage after the town of Bayeux (Latin: Bajoce ) in Normandy, France. The GSSP for the base of the Bajocian is located in the Murtinheira section at Cabo Mondego , Portugal; it was ratified in 1997. The base of the Bajocian is defined by the first appearance of the ammonite Hyperlioceras mundum . The Bathonian is named after the city of Bath , England, introduced by Belgian geologist d'Omalius d'Halloy in 1843, after an incomplete section of oolitic limestones in several quarries in

7824-591: The Black Jurassic and the overlying clayey sandstone and ferruginous oolite of the Brown Jurassic sequences of southwestern Germany. The GSSP for the base of the Aalenian is located at Fuentelsaz in the Iberian range near Guadalajara, Spain , and was ratified in 2000. The base of the Aalenian is defined by the first appearance of the ammonite Leioceras opalinum . Alcide d'Orbigny in 1842 named

7987-560: The Black Jurassic in England by William Conybeare and William Phillips in 1822. William Phillips, the geologist, worked with William Conybeare to find out more about the Black Jurassic in England. The French palaeontologist Alcide d'Orbigny in papers between 1842 and 1852 divided the Jurassic into ten stages based on ammonite and other fossil assemblages in England and France, of which seven are still used, but none has retained its original definition. The German geologist and palaeontologist Friedrich August von Quenstedt in 1858 divided

8150-655: The Callovian–Oxfordian boundary, peaking possibly as high as 140 metres above present sea level at the Kimmeridgian–Tithonian boundary. The sea levels falls in the late Tithonian, perhaps to around 100 metres, before rebounding to around 110 metres at the Tithonian–Berriasian boundary. The sea level within the long-term trends across the Jurassic was cyclical, with 64 fluctuations, 15 of which were over 75 metres. The most noted cyclicity in Jurassic rocks

8313-463: The Early Jurassic, but also including part of the preceding Rhaetian . The Hettangian Stage was named by Swiss palaeontologist Eugène Renevier in 1864 after Hettange-Grande in north-eastern France. The GSSP for the base of the Hettangian is located at the Kuhjoch Pass, Karwendel Mountains , Northern Calcareous Alps , Austria; it was ratified in 2010. The beginning of the Hettangian, and thus

SECTION 50

#1732758187668

8476-613: The Eiberg Basin of the Northern Calcareous Alps , there was a very rapid palynomorph turnover. The palynological and palaeobotanical succession in Queensland shows a Classopolis bloom after the TJME. Polyploidy may have been an important factor that mitigated a conifer species' risk of going extinct. The leading and best evidenced explanation for the TJME is massive volcanic eruptions, specifically from

8639-473: The Eiberg Basin. The persistence of anoxia into the Hettangian age may have helped delay the recovery of marine life in the extinction's aftermath, and recurrent hydrogen sulphide poisoning likely had the same retarding effect on biotic rediversification. Research on the role of ozone shield deterioration during the Permian-Triassic mass extinction has suggested that it may have been a factor in

8802-517: The Greek goddess of dawn . His name was chosen by Albert Oppel for this stratigraphical stage because the Tithonian finds itself hand in hand with the dawn of the Cretaceous. The base of the Tithonian currently lacks a GSSP. The working definition for the base of the Tithonian is the first appearance of the ammonite genus Gravesia . The upper boundary of the Jurassic is currently undefined, and

8965-407: The Hettangian of Sweden, suggested to be closely related to the living Austrotaxus , while Marskea jurassica from the Middle Jurassic of Yorkshire, England and material from the Callovian–Oxfordian Daohugou Bed in China are thought to be closely related to Amentotaxus , with the latter material assigned to the modern genus, indicating that Taxaceae had substantially diversified by the end of

9128-402: The Jura Mountains as geologically distinct from the Triassic aged Muschelkalk of southern Germany , but he erroneously concluded that they were older. He then named them Jura-Kalkstein ('Jura limestone') in 1799. In 1829, the French naturalist Alexandre Brongniart published a book entitled Description of the Terrains that Constitute the Crust of the Earth or Essay on the Structure of

9291-411: The Jurassic as a whole, is marked by the first appearance of the ammonite Psiloceras spelae tirolicum in the Kendlbach Formation exposed at Kuhjoch. The base of the Jurassic was previously defined as the first appearance of Psiloceras planorbis by Albert Oppel in 1856–58, but this was changed as the appearance was seen as too localised an event for an international boundary. The Sinemurian Stage

9454-400: The Jurassic of Asia has strap-shaped ginkgo-like leaves with highly distinct reproductive structures with similarities to those of peltasperm and corystosperm seed ferns, has been suggested to be a member of Ginkgoales sensu lato. Triassic%E2%80%93Jurassic extinction event The Triassic–Jurassic ( Tr-J ) extinction event ( TJME ), often called the end-Triassic extinction , marks

9617-457: The Jurassic was warmer than the present, and there were no ice caps . Forests grew close to the poles, with large arid expanses in the lower latitudes. On land, the fauna transitioned from the Triassic fauna, dominated jointly by dinosauromorph and pseudosuchian archosaurs , to one dominated by dinosaurs alone. The first stem-group birds appeared during the Jurassic, evolving from a branch of theropod dinosaurs. Other major events include

9780-482: The Jurassic, both the North and South Pole were covered by oceans. Beginning in the Early Jurassic, the Boreal Ocean was connected to the proto-Atlantic by the "Viking corridor" or Transcontinental Laurasian Seaway, a passage between the Baltic Shield and Greenland several hundred kilometers wide. During the Callovian, the Turgai Epicontinental Sea formed, creating a marine barrier between Europe and Asia. Madagascar and Antarctica began to rift away from Africa during

9943-434: The Jurassic, the North Atlantic Ocean remained relatively narrow, while the South Atlantic did not open until the Cretaceous. The continents were surrounded by Panthalassa , with the Tethys Ocean between Gondwana and Asia. At the end of the Triassic, there was a marine transgression in Europe, flooding most parts of central and western Europe transforming it into an archipelago of islands surrounded by shallow seas. During

SECTION 60

#1732758187668

10106-603: The Jurassic. The oldest unambiguous members of Podocarpaceae are known from the Jurassic, found across both hemispheres, including Scarburgia and Harrisiocarpus from the Middle Jurassic of England, as well as unnamed species from the Middle-Late Jurassic of Patagonia. During the Early Jurassic, the flora of the mid-latitudes of Eastern Asia were dominated by the extinct deciduous broad leafed conifer Podozamites , which appears to not be closely related to any living family of conifer. Its range extended northwards into polar latitudes of Siberia and then contracted northward in

10269-461: The Jurassic. However, their extinction rate at the Triassic–Jurassic boundary was not elevated. The highest extinction rates experienced by Mesozoic marine reptiles actually occurred at the end of the Ladinian stage, which corresponds to the end of the Middle Triassic. The only marine reptile families which became extinct at or slightly before the Triassic–Jurassic boundary were the placochelyids (the last family of placodonts ), making plesiosaurs

10432-510: The Jurassic–Cretaceous boundary is currently the only system boundary to lack a defined GSSP. Placing a GSSP for this boundary has been difficult because of the strong regionality of most biostratigraphic markers, and lack of any chemostratigraphic events, such as isotope excursions (large sudden changes in ratios of isotopes ), that could be used to define or correlate a boundary. Calpionellids , an enigmatic group of planktonic protists with urn-shaped calcitic tests briefly abundant during

10595-532: The Known Lands of the Earth. In this book, Brongniart used the phrase terrains jurassiques when correlating the "Jura-Kalkstein" of Humboldt with similarly aged oolitic limestones in Britain, thus coining and publishing the term "Jurassic". The German geologist Leopold von Buch in 1839 established the three-fold division of the Jurassic, originally named from oldest to the youngest: the Black Jurassic , Brown Jurassic , and White Jurassic . The term " Lias " had previously been used for strata of equivalent age to

10758-407: The Manicouagan and Rochechouart craters were formed in eras of different magnetic polarity, and radiometric dating of the individual craters has shown that the impacts occurred millions of years apart. Shocked quartz has been found in Rhaetian deposits from the Northern Apennines of Italy, providing possible evidence of an end-Triassic extraterrestrial impact. Certain trace metals indicative of

10921-402: The Manicouagan reservoir. The eroded Rochechouart impact structure in France has most recently been dated to 201 ± 2 million years ago, but at 25 km (16 mi) across (possibly up to 50 km (30 mi) across originally), it appears to be too small to have affected the ecosystem, although it has been speculated to have played a role in an alleged much smaller extinction event at

11084-412: The Middle Jurassic. Also abundant during the Jurassic is the extinct family Cheirolepidiaceae , often recognised through their highly distinctive Classopolis pollen. Jurassic representatives include the pollen cone Classostrobus and the seed cone Pararaucaria . Araucarian and Cheirolepidiaceae conifers often occur in association. The oldest definitive record of the cypress family ( Cupressaceae )

11247-443: The Middle to Late Jurassic, corresponding to the increasing aridity of the region. Ginkgoales , of which the sole living species is Ginkgo biloba , were more diverse during the Jurassic: they were among the most important components of Eurasian Jurassic floras and were adapted to a wide variety of climatic conditions. The earliest representatives of the genus Ginkgo , represented by ovulate and pollen organs similar to those of

11410-409: The Norian and suffered further losses in the TJME. Conulariids seemingly completely died out at the end of the Triassic. Around 96% of coral genera died out, with integrated corals being especially devastated. Corals practically disappeared from the Tethys Ocean at the end of the Triassic except for its northernmost reaches, resulting in an early Hettangian "coral gap". There is good evidence for

11573-449: The Norian-Rhaetian boundary. The 40 km (25 mi) wide Saint Martin crater in Manitoba has been proposed as a candidate for a possible TJME-causing impact, but its has since been dated to be Carnian. Other putative or confirmed Triassic craters include the 80 km (50 mi) wide Puchezh-Katunki crater in Eastern Russia (though it may be Jurassic in age), the 15 km (9 mi) wide Obolon' crater in Ukraine , and

11736-650: The North Atlantic Ocean with eastern Panthalassa. Palaeontological data suggest that the seaway had been open since the Early Jurassic. As part of the Nevadan orogeny , which began during the Triassic, the Cache Creek Ocean closed, and various terranes including the large Wrangellia Terrane accreted onto the western margin of North America. By the Middle Jurassic the Siberian plate and

11899-718: The North China-Amuria block had collided, resulting in the closure of the Mongol-Okhotsk Ocean . During the Early Jurassic, around 190 million years ago, the Pacific Plate originated at the triple junction of the Farallon , Phoenix , and Izanagi tectonic plates , the three main oceanic plates of Panthalassa. The previously stable triple junction had converted to an unstable arrangement surrounded on all sides by transform faults because of

12062-496: The Plain formed the bed of Lake Idaho . Wave action in the lake washed sediments back and forth in the shallows on the southwestern shore, forming ooids and depositing them on steeper benches near the shore in 2- to 40-foot thicknesses. When the lake drained (2 to 4 million years ago), the oolite was left behind, along with siltstone , volcanic tuffs and alluvium from adjacent mountain slopes. The other sediments eroded away, while

12225-409: The TJME as well. A spike in the abundance of unseparated tetrads of Kraeuselisporites reissingerii has been interpreted as evidence of increased ultraviolet radiation flux resulting from ozone layer damage caused by volcanic aerosols. The extinctions at the end of the Triassic were initially attributed to gradually changing environments. Within his 1958 study recognizing biological turnover between

12388-547: The TJME coincides with mercury anomalies and is thus believed by researchers to have been caused by mercury poisoning . δ Hg and Δ Hg evidence suggests that volcanism caused the mercury loading directly at the Triassic-Jurassic boundary, but that there were later bouts of elevated mercury in the environment during the Early Jurassic caused by eccentricity-forced enhancement of hydrological cycling and erosion that resulted in remobilisation of volcanically injected mercury that had been deposited in wetlands. The intense, rapid warming

12551-482: The TJME have numerical values very different from what would be expected in an extraterrestrial impact scenario, providing further evidence against this hypothesis. The Triassic-Jurassic boundary furthermore lacks a fern spore spike akin to that observed at the terminus of the Cretaceous, inconsistent with an asteroid impact. The extremely rapid, centuries-long timescale of carbon emissions and global warming caused by pulses of CAMP volcanism has drawn comparisons between

12714-549: The TJME, mobile bivalve taxa outnumbered stationary bivalve taxa. Gastropod diversity was barely affected at the Triassic-Jurassic boundary, although gastropods gradually suffered numerous losses over the late Norian and Rhaetian, during the leadup to the TJME. Brachiopods declined in diversity at the end of the Triassic before rediversifying in the Sinemurian and Pliensbachian . Bryozoans , particularly taxa that lived in offshore settings, had already been in decline since

12877-669: The TOAE represented one of the most severe extinctions in their evolutionary history. While the event had significant impact on marine invertebrates, it had little effect on marine reptiles. During the TOAE, the Sichuan Basin was transformed into a giant lake , probably three times the size of modern-day Lake Superior , represented by the Da'anzhai Member of the Ziliujing Formation . The lake likely sequestered ~460 gigatons (Gt) of organic carbon and ~1,200 Gt of inorganic carbon during

13040-768: The Tithonian, known as the Early Tithonian Cooling Event (ETCE). The end of the Jurassic was marked by the Tithonian–early Barremian Cool Interval (TBCI), beginning 150 million years ago and continuing into the Early Cretaceous . The Toarcian Oceanic Anoxic Event (TOAE), also known as the Jenkyns Event, was an episode of widespread oceanic anoxia during the early part of the Toarcian Age, c. 183 Mya. It

13203-740: The Toarcian around 174 million years ago. During the Toarcian Warm Interval, ocean surface temperatures likely exceeded 30 °C (86 °F), and equatorial and subtropical (30°N–30°S) regions are likely to have been extremely arid, with temperatures in the interior of Pangea likely in excess of 40 °C (104 °F).The Toarcian Warm Interval is followed by the Middle Jurassic Cool Interval (MJCI) between 174 and 164 million years ago, which may have been punctuated by brief, ephemeral icehouse intervals. During

13366-463: The Triassic and Jurassic, Edwin H. Colbert 's proposal was that this extinction was a result of geological processes decreasing the diversity of land biomes. He considered the Triassic period to be an era of the world experiencing a variety of environments, from towering highlands to arid deserts to tropical marshes. In contrast, the Jurassic period was much more uniform both in climate and elevation due to excursions by shallow seas. Later studies noted

13529-408: The Triassic experienced a "multiple impact event", a large fragmented asteroid or comet which broke up and impacted the earth in several places at the same time. Such an impact has been observed in the present day, when Comet Shoemaker-Levy 9 broke up and hit Jupiter in 1992. However, the "multiple impact event" hypothesis for Triassic impact craters has not been well-supported; Kent (1998) noted that

13692-425: The Triassic, or instead more gradual. During the Triassic, amphibians were mainly represented by large, crocodile-like members of the order Temnospondyli . Although the earliest lissamphibians (modern amphibians like frogs and salamanders ) did appear during the Triassic, they would become more common in the Jurassic while the temnospondyls diminished in diversity past the Triassic–Jurassic boundary. Although

13855-652: The Triassic-Jurassic extinction and were nearly wiped out. Ceratitidans , the most prominent group of ammonites in the Triassic, became extinct at the end of the Rhaetian after having their diversity reduced significantly in the Norian , while other ammonite groups such as the Ammonitina , Lytoceratina , and Phylloceratina diversified from the Early Jurassic onward. Bivalves suffered heavy losses, although

14018-550: The Triassic-Jurassic mass extinction and anthropogenic global warming , currently causing the Holocene extinction . The current rate of carbon dioxide emissions is around 50 gigatonnes per year, hundreds of times faster than during the latest Triassic, although the lack of extremely detailed stratigraphic resolution and pulsed nature of CAMP volcanism means that individual pulses of greenhouse gas emissions likely occurred on comparable timescales to human release of warming gases since

14181-488: The Triassic–Jurassic boundary. The boundary between the Adamanian and Revueltian land vertebrate faunal zones, which involved extinctions and faunal changes in tetrapods and plants, was possibly also caused by the Manicouagan impact, although discrepancies between magnetochronological and isotopic dating lead to some uncertainty. Other Triassic craters are closer to the Triassic–Jurassic boundary but also much smaller than

14344-593: The Triassic–Jurassic extinction, similar to the extraterrestrial object which was the main factor in the Cretaceous–Paleogene extinction about 66 million years ago, as evidenced by the Chicxulub crater in Mexico. However, so far no impact crater of sufficient size has been dated to precisely coincide with the Triassic–Jurassic boundary. Nevertheless, the Late Triassic did experience several impacts, including

14507-543: The abruptness of this transition and the relative abundances of given spore types both before and after the boundary are highly variable from one region to another, pointing to a global ecological restructuring rather than a mass extinction of plants. Overall, plants suffered minor diversity losses on a global scale as a result of the extinction, but species turnover rates were high and substantial changes occurred in terms of relative abundance and growth distribution among taxa. Evidence from Central Europe suggests that rather than

14670-462: The amount of carbon dioxide emitted was only around 250 ppm, not enough to generate a mass extinction. In addition, at some sites, changes in carbon isotope ratios have been attributed to diagenesis and not any primary environmental changes. The flood basalts of the CAMP released gigantic quantities of carbon dioxide , a potent greenhouse gas causing intense global warming. Before the TJME, carbon dioxide levels were around 1,000 ppm as measured by

14833-489: The appearance of the earliest crabs and modern frogs , salamanders and lizards . Mammaliaformes , one of the few cynodont lineages to survive the end of the Triassic, continued to diversify throughout the period, with the Jurassic seeing the emergence of the first crown group mammals . Crocodylomorphs made the transition from a terrestrial to an aquatic life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs , while pterosaurs were

14996-417: The atmosphere, as well as the possible associated release of methane clathrates . This likely accelerated the hydrological cycle and increased silicate weathering , as evidenced by an increased amount of organic matter of terrestrial origin found in marine deposits during the TOAE. Groups affected include ammonites, ostracods , foraminifera , bivalves , cnidarians , and especially brachiopods , for which

15159-461: The base of the Toarcian is located at Peniche, Portugal , and was ratified in 2014. The boundary is defined by the first appearance of ammonites belonging to the subgenus Dactylioceras ( Eodactylites ) . The Aalenian is named after the city of Aalen in Germany. The Aalenian was defined by Swiss geologist Karl Mayer-Eymar in 1864. The lower boundary was originally between the dark clays of

15322-433: The boundary according to British fissure deposits from the Rhaetian. Aetosaurs, kuehneosaurids , drepanosaurs, thecodontosaurids , "saltoposuchids" (like Terrestrisuchus ), trilophosaurids, and various non- crocodylomorph pseudosuchians are all examples of Rhaetian reptiles which may have become extinct at the Triassic–Jurassic boundary. In the TJME's aftermath, dinosaurs experienced a major radiation, filling some of

15485-493: The boundary between the Triassic and Jurassic periods, 201.4  million years ago . It is one of five major extinction events , profoundly affecting life on land and in the oceans. In the seas, about 23–34% of marine genera disappeared. On land, all archosauromorph reptiles other than crocodylomorphs (the lineage leading to modern crocodilians), dinosaurs , and pterosaurs (flying reptiles) became extinct; some of

15648-402: The boundary between the Late Triassic and Early Jurassic has been tied to a large negative δ C excursion, with values as low as -2.8%. Carbon isotopes of hydrocarbons ( n -alkanes ) derived from leaf wax and lignin , and total organic carbon from two sections of lake sediments interbedded with the CAMP in eastern North America have shown carbon isotope excursions similar to those found in

15811-647: The broad leaved Ginkgoales which declined to near extinction across the Tr–J boundary. Ferns and other species with dissected leaves displayed greater adaptability to atmosphere conditions of the extinction event, and in some instances were able to proliferate across the boundary and into the Jurassic. In the Jiyuan Basin of North China, Classopolis content increased drastically in concordance with warming, drying, wildfire activity, enrichments in isotopically light carbon, and an overall reduction in floral diversity. In

15974-458: The carbon cycle was so disrupted that it did not stabilise until the Sinemurian . Mercury anomalies from deposits in various parts of the world have further bolstered the volcanic cause hypothesis, as have anomalies from various platinum-group elements. Nickel enrichments are also observed at the Triassic-Jurassic boundary coevally with light carbon enrichments, providing yet more evidence of massive volcanism. Some scientists initially rejected

16137-508: The carbon isotopic excursions are shown in the same places, making the case for a volcanic cause of a mass extinction. The observed negative carbon isotope excursion is lower in some sites that correspond to what was then eastern Panthalassa because of the extreme aridity of western Pangaea limiting weathering and erosion there. The negative δ C excursion associated with CAMP volcanism lasted for approximately 20,000 to 40,000 years, or about one or two of Earth's axial precession cycles, although

16300-460: The climate may have become much more seasonal, with long droughts interrupted by severe monsoons . The world gradually got warmer over this time as well; from the late Norian to the Rhaetian, mean annual temperatures rose by 7 to 9 °C. The site of Hochalm in Austria preserves evidence of carbon cycle perturbations during the Rhaetian preceding the Triassic-Jurassic boundary, potentially having

16463-462: The decline of temnospondyls did send shockwaves through freshwater ecosystems, it was probably not as abrupt as some authors have suggested. Brachyopoids , for example, survived until the Cretaceous according to new discoveries in the 1990s. Several temnospondyl groups did become extinct near the end of the Triassic despite earlier abundance, but it is uncertain how close their extinctions were to

16626-447: The dominant flying vertebrates . Modern sharks and rays first appeared and diversified during the period, while the first known crown-group teleost fish appeared near the end of the period. The flora was dominated by ferns and gymnosperms , including conifers , of which many modern groups made their first appearance during the period, as well as other groups like the extinct Bennettitales . The chronostratigraphic term "Jurassic"

16789-712: The earliest Jurassic, immediately after the Triassic-Jurassic transition. Elevated wildfire activity is also known from the Junggar Basin . In the Jiyuan Basin, two distinct pulses of drastically elevated wildfire activity are known: the first mainly affected canopies and occurred amidst relatively humid conditions while the second predominantly affected ground cover and was associated with aridity. Frequent wildfires, combined with increased seismic activity from CAMP emplacement, led to apocalyptic soil degradation . In addition to these climatic effects, oceanic uptake of volcanogenic carbon and sulphur dioxide would have led to

16952-571: The emission of sulphur dioxide aerosols. A 2022 study shows that high latitudes had colder climates with evidence of mild glaciation. The authors propose that cold periods ("ice ages") induced by volcanic ejecta clouding the atmosphere might have favoured endothermic animals, with dinosaurs, pterosaurs, and mammals being more capable at enduring these conditions than large pseudosuchians due to insulation. CAMP volcanism released enormous amounts of toxic mercury . The appearance of high rates of mutaganesis of varying severity in fossil spores during

17115-591: The end of the Triassic, the Peltaspermaceae became extinct in most parts of the world, with Lepidopteris persisting into the Early Jurassic in Patagonia. Dicroidium , a corystosperm seed fern that was a dominant part of Gondwanan floral communities during the Triassic, also declined at the Triassic–Jurassic boundary, surviving as a relict in Antarctica into the Early Jurassic. Conifers formed

17278-413: The end of the Triassic, with both dominant herbivorous subgroups (such as aetosaurs ) and carnivorous ones ( rauisuchids ) having died out. Phytosaurs, drepanosaurs , trilophosaurids , tanystropheids , and procolophonids , which were other common reptiles in the Late Triassic, had also become extinct by the start of the Jurassic. However, pinpointing the extinction of these different land reptile groups

17441-569: The end of the Triassic. The last known metoposaurids (" Apachesaurus ") were from the Redonda Formation , which may have been early Rhaetian or late Norian . Gerrothorax , the last known plagiosaurid , has been found in rocks which are probably (but not certainly) Rhaetian, while a capitosaur humerus was found in Rhaetian-age deposits in 2018. Therefore, plagiosaurids and capitosaurs were likely victims of an extinction at

17604-494: The end of the mass extinction despite numerous relapses into anoxic conditions during the earliest Jurassic. In the Neuquén Basin , recovery began in the late early Hettangian and lasted until a new biodiversity equilibrium in the late Hettangian. Also despite recurrent anoxic episodes, large bivalves began to reappear shortly after the extinction event. Siliceous sponges dominated the immediate aftermath interval thanks to

17767-434: The enormous influx of silica into the oceans from the weathering of the CAMP's aerially extensive basalts. Some clades recovered more slowly than others, however, as exemplified by corals and their disappearance in the early Hettangian. Fish did not suffer a mass extinction at the end of the Triassic. The Late Triassic in general did experience a gradual drop in actinopterygiian diversity after an evolutionary explosion in

17930-465: The eruption of the Karoo-Ferrar large igneous provinces . The end of the Jurassic, however, has no clear, definitive boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north and Gondwana to the south. The climate of

18093-413: The event. Seawater pH , which had already substantially decreased prior to the event, increased slightly during the early stages of the TOAE, before dropping to its lowest point around the middle of the event. This ocean acidification is the probable cause of the collapse of carbonate production. Additionally, anoxic conditions were exacerbated by enhanced recycling of phosphorus back into ocean water as

18256-502: The evidence for this is primarily European, probably controlled by changes in eustatic sea level. There is no evidence of a mass extinction of plants at the Triassic–Jurassic boundary. At the Triassic–Jurassic boundary in Greenland, the sporomorph (pollen and spores) record suggests a complete floral turnover. An analysis of macrofossil floral communities in Europe suggests that changes were mainly due to local ecological succession . At

18419-530: The extinction was highly selective, with some bivalve clades escaping substantial diversity losses. The Lilliput effect affected megalodontid bivalves, whereas file shell bivalves experienced the Brobdingnag effect, the reverse of the Lilliput effect, as a result of the mass extinction event. There is some evidence of a bivalve cosmopolitanism event during the mass extinction. Additionally, following

18582-608: The extinction. The site of St. Audrie's Bay displays a shift from diverse gymnosperm-dominated forests to Cheirolepidiaceae-dominated monocultures. The Danish Basin saw 34% of its Rhaetian spore-pollen assemblage, including Cingulizonates rhaeticus , Limbosporites lundbladiae , Polypodiisporites polymicroforatus , and Ricciisporites tuberculatus , disappear, with the post-extinction plant community being dominated by pinacean conifers such as Pinuspollenites minimus and tree ferns such as Deltoidospora , with ginkgos, cycads, cypresses, and corystospermous seed ferns also represented. Along

18745-633: The first appearance of Cardioceras redcliffense as the lower boundary. The village of Kimmeridge on the coast of Dorset , England, is the origin of the name of the Kimmeridgian. The stage was named by Alcide d'Orbigny in 1842 in reference to the Kimmeridge Clay . The GSSP for the base of the Kimmeridgian is the Flodigarry section at Staffin Bay on the Isle of Skye , Scotland , which

18908-463: The first appearance of the ammonite Strambergella jacobi , formerly placed in the genus Berriasella , but its use as a stratigraphic indicator has been questioned, as its first appearance does not correlate with that of C. alpina . The Kimmeridge Clay and equivalents are the major source rock for the North Sea oil . The Arabian Intrashelf Basin, deposited during the Middle and Late Jurassic,

19071-498: The first place) makes it difficult to correlate the impact with extinction. Onoue et al. (2016) alternatively proposed that the Manicouagan impact was responsible for a marine extinction in the middle of the Norian which affected radiolarians, sponges, conodonts, and Triassic ammonoids. Thus, the Manicouagan impact may have been partially responsible for the gradual decline in the latter two groups which culminated in their extinction at

19234-399: The floristic turnover by exploiting newly abundant plants. Odonates suffered highly selective losses, and their morphospace was heavily restructured as a result. The extinction event marks a floral turnover as well, with estimates of the percentage of Rhaetian pre-extinction plants being lost ranging from 17% to 73%. Though spore turnovers are observed across the Triassic-Jurassic boundary,

19397-521: The genus Elatides . The Jurassic also saw the first appearances of some modern genera of cypresses, such as Sequoia . Members of the extinct genus Schizolepidopsis which likely represent a stem-group to the pine family ( Pinaceae ), were widely distributed across Eurasia during the Jurassic. The oldest unambiguous record of Pinaceae is the pine cone Eathiestrobus , known from the Late Jurassic (Kimmeridgian) of Scotland, which remains

19560-462: The groups which died out were previously abundant, such as aetosaurs , phytosaurs , and rauisuchids . Plants , crocodylomorphs, dinosaurs, pterosaurs and mammals were left largely untouched, allowing the dinosaurs, pterosaurs, and crocodylomorphs to become the dominant land animals for the next 135 million years. The cause of the Tr-J extinction event may have been extensive volcanic eruptions in

19723-470: The home aquarium industry because their small grain size (0.2 to 1.22 mm) is ideal for shallow static beds and bottom covering of up to 1" in depth. Also known as "oolitic" sand, the sugar-sized round grains of this sand pass easily through the gills of gobies and other sand-sifting organisms. This unusually smooth sand promotes the growth of bacteria, which are important biofilters in home aquaria. Because of its extremely small grain size, oolitic sand has

19886-566: The hypothesis of there being no significant floral mass extinction on this basis. In the Newark Supergroup of the United States East Coast , about 60% of the diverse monosaccate and bisaccate pollen assemblages disappear at the Tr–J boundary, indicating a major extinction of plant genera. Early Jurassic pollen assemblages are dominated by Corollina , a new genus that took advantage of the empty niches left by

20049-751: The islands of the Lower Florida Keys , and much of the Everglades , are underlain by Miami Oolite . This limestone was formed by deposition when shallow seas covered the area between periods of glaciation . The material consolidated and eroded during later exposure above the ocean surface. One of the world's largest freshwater lakebed oolites is the Shoofly Oolite, a section of the Glenns Ferry Formation on southwestern Idaho 's Snake River Plain . 10 million years ago,

20212-543: The late Early Jurassic in association with the eruption of the Karoo-Ferrar large igneous provinces , opening the western Indian Ocean and beginning the fragmentation of Gondwana. At the beginning of the Jurassic, North and South America remained connected, but by the beginning of the Late Jurassic they had rifted apart to form the Caribbean Seaway, also known as the Hispanic Corridor, which connected

20375-416: The late Sinemurian–Pliensbachian before regressing to near present levels by the late Pliensbachian. There seems to have been a gradual rise to a peak of ~75 m above present sea level during the Toarcian. During the latest part of the Toarcian, the sea level again dropped by several tens of metres. It progressively rose from the Aalenian onwards, aside from dips of a few tens of metres in the Bajocian and around

20538-463: The latest Jurassic to earliest Cretaceous, have been suggested to represent the most promising candidates for fixing the Jurassic–Cretaceous boundary In particular, the first appearance Calpionella alpina , co-inciding with the base of the eponymous Alpina subzone, has been proposed as the definition of the base of the Cretaceous. The working definition for the boundary has often been placed as

20701-575: The main crisis began. This early phase of environmental degradation in eastern Panthalassa may have been caused by an early phase of CAMP activity. Anoxic, reducing conditions were likewise present in western Panthalassa off the coast of what is now Japan for about a million years prior to the TJME. During the TJME, the rapid warming and increase in continental weathering led to the stagnation of ocean circulation and deoxygenation of seawater in many ocean regions, causing catastrophic marine environmental effects in conjunction with ocean acidification, which

20864-626: The margins of the European Epicontinental Sea and the European shores of the Tethys, coastal and near-coastal mires fell victim to an abrupt sea level rise. These mires were replaced by a pioneering opportunistic flora after an abrupt sea level fall, although its heyday was short lived and it died out shortly after its rise. The opportunists that established themselves along the Tethyan coastline were primarily spore-producers. In

21027-430: The modern biosphere. If human-induced climate change persists as is, predictions can be made as to how various aspects of the biosphere will respond based on records of the TJME. For example, current conditions such the increased carbon dioxide levels, ocean acidification , and ocean deoxygenation create a similar climate to that of the Triassic-Jurassic boundary for marine life, so it is the common assumption that should

21190-425: The modern species, are known from the Middle Jurassic in the Northern Hemisphere. Several other lineages of ginkgoaleans are known from Jurassic rocks, including Yimaia , Grenana , Nagrenia and Karkenia . These lineages are associated with Ginkgo- like leaves, but are distinguished from living and fossil representatives of Ginkgo by having differently arranged reproductive structures. Umaltolepis from

21353-517: The more resistant oolite weathered into hummocks, small arches and other natural "sculptures". The Shoofly Oolite lies on public land west of Bruneau, Idaho managed by the Bureau of Land Management (BLM). The physical and chemical properties of the Shoofly Oolite are the setting for a suite of rare plants, which the BLM protects through land use management and on-site interpretation. This type of limestone

21516-478: The mostly marine St. Audrie's Bay section, Somerset, England; the correlation suggests that the TJME began at the same time in marine and terrestrial environments, slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco, with both a critical CO 2 greenhouse and a marine biocalcification crisis. Contemporaneous CAMP eruptions, mass extinction, and

21679-457: The negative carbon isotope excursions at the terminus of the Triassic. Global temperatures rose sharply by 3 to 4 °C. In some regions, the temperature rise was as great as 10 °C. Kaolinite-dominated clay mineral spectra reflect the extremely hot and humid greenhouse conditions engendered by the CAMP. Soil erosion occurred as the hydrological cycle was accelerated by the extreme global heat. The catastrophic dissociation of gas hydrates as

21842-408: The niches of more ancient groups of amphibians and reptiles which were extinct by the start of the Jurassic. Olsen (1987) estimated that 42% of all terrestrial tetrapods became extinct at the end of the Triassic, based on his studies of faunal changes in the Newark Supergroup of eastern North America. More modern studies have debated whether the turnover in Triassic tetrapods was abrupt at the end of

22005-463: The niches vacated by the victims of the extinction. Crocodylomorphs likewise underwent a very rapid and major adaptive radiation. Surviving non-mammalian synapsid clades similarly played a role in the post-TJME adaptive radiation during the Early Jurassic. Herbivorous insects were minimally affected by the TJME; evidence from the Sichuan Basin shows they were overall able to quickly adapt to

22168-420: The ocean floor acting as a buffer against large CO 2 emissions. The climate of the Jurassic was generally warmer than that of present, by around 5–10 °C (9–18 °F), with atmospheric carbon dioxide likely about four times higher. Intermittent "cold snap" intervals are known to have occurred during this time period, however, interrupting the otherwise warm greenhouse climate. Forests likely grew near

22331-458: The oceans, resulting in large areas of desert and scrubland in the lower latitudes between 40° N and S of the equator. Tropical rainforest and tundra biomes are likely to have been rare or absent. The Jurassic also witnessed the decline of the Pangaean megamonsoon that had characterised the preceding Permian and Triassic periods. Variation in the frequency of wildfire activity in the Jurassic

22494-399: The oceans. A meteoric shift towards positive sulphur isotope ratios in reduced sulphur species indicates a complete utilisation of sulphate by sulphate reducing bacteria. Evidence of anoxia has been discovered at the Triassic-Jurassic boundary across the world's oceans; the western Tethys, eastern Tethys, and Panthalassa were all affected by a precipitous drop in seawater oxygen, although at

22657-462: The only known unequivocal fossil of the group before the Cretaceous. Despite being the earliest known member of the Pinaceae, Eathiestrobus appears to be a member of the pinoid clade of the family, suggesting that the initial diversification of Pinaceae occurred earlier than has been found in the fossil record. The earliest record of the yew family ( Taxaceae ) is Palaeotaxus rediviva , from

22820-484: The only surviving sauropterygians , and giant ichthyosaurs such as shastasaurids . Nevertheless, some authors have argued that the end of the Triassic acted as a genetic " bottleneck " for ichthyosaurs, which never regained the level of anatomical diversity and disparity which they possessed during the Triassic. The high diversity of rhomaelosaurids immediately after the TJME points to a gradual extinction of marine reptiles rather than an abrupt one. Terrestrial fauna

22983-609: The poles, where they experienced warm summers and cold, sometimes snowy winters; there were unlikely to have been ice sheets given the high summer temperatures that prevented the accumulation of snow, though there may have been mountain glaciers. Dropstones and glendonites in northeastern Siberia during the Early to Middle Jurassic indicate cold winters. The ocean depths were likely 8 °C (14 °F) warmer than present, and coral reefs grew 10° of latitude further north and south. The Intertropical Convergence Zone likely existed over

23146-647: The region. The GSSP for the base of the Bathonian is Ravin du Bès, Bas-Auran area, Alpes de Haute Provence , France; it was ratified in 2009. The base of the Bathonian is defined by the first appearance of the ammonite Gonolkites convergens , at the base of the Zigzagiceras zigzag ammonite zone . The Callovian is derived from the Latinized name of the village of Kellaways in Wiltshire , England, and

23309-399: The result of the replacement of the original texture in limestone. Oolitic hematite occurs at Red Mountain near Birmingham, Alabama , along with oolitic limestone. They are usually formed in warm, supersaturated, shallow, highly agitated marine water intertidal environments, though some are formed in inland lakes. The mechanism of formation starts with a small fragment of sediment acting as

23472-676: The second-largest confirmed impact in the Mesozoic. The Manicouagan Reservoir in Quebec is one of the most visible large impact craters on Earth, and at 100 km (62 mi) in diameter it is tied with the Eocene Popigai impact structure in Siberia as the fourth-largest impact crater on Earth. Olsen et al. (1987) were the first scientists to link the Manicouagan crater to the Triassic–Jurassic extinction, citing its age which at

23635-409: The shallow subseafloor may also reflect decreased pH, these structures being speculated to have precipitated concomitantly with acidification. In some studied sections, the TJME biocalcification crisis is masked by emersion of carbonate platforms induced by marine regression. Anoxia was another mechanism of extinction; the end-Triassic extinction was coeval with an uptick in black shale deposition and

23798-403: The stomatal index of Lepidopteris ottonis , but this quantity jumped to 1,300 ppm at the onset of the extinction event. During the TJME, carbon dioxide concentrations increased fourfold. The record of CAMP degassing shows several distinct pulses of carbon dioxide immediately following each major pulse of magmatism, at least two of which amount to a doubling of atmospheric CO 2 . Carbon dioxide

23961-572: The three series of von Buch in the Swabian Jura into six subdivisions defined by ammonites and other fossils. The German palaeontologist Albert Oppel in his studies between 1856 and 1858 altered d'Orbigny's original scheme and further subdivided the stages into biostratigraphic zones, based primarily on ammonites. Most of the modern stages of the Jurassic were formalized at the Colloque du Jurassique à Luxembourg in 1962. The Jurassic Period

24124-412: The time was roughly considered to be Late Triassic. More precise radiometric dating by Hodych & Dunning (1992) has shown that the Manicouagan impact occurred about 214 million years ago, about 13 million years before the Triassic–Jurassic boundary. Therefore, it could not have been responsible for an extinction precisely at the Triassic–Jurassic boundary. Nevertheless, the Manicouagan impact did have

24287-628: The transition from the Palaeozoic evolutionary fauna to the Modern evolutionary fauna, a change that began in the aftermath of the end-Guadalupian extinction and continued following the Permian-Triassic extinction event (PTME). Between 23% and 34.1% of marine genera went extinct. Plankton diversity dropped suddenly, but it was relatively mildly impacted at the Triassic-Jurassic boundary, although extinction rates among radiolarians rose significantly. Ammonites were affected substantially by

24450-903: The trends continue, modern reef-building taxa and skeletal benthic organisms will be preferentially impacted. The end-Triassic reef crisis has been specifically cited as a possible analogue for the fate of present coral reefs should anthropogenic global warming continue. Oolite Oolite or oölite (from Ancient Greek ᾠόν (ōión)  'egg stone') is a sedimentary rock formed from ooids , spherical grains composed of concentric layers. Strictly, oolites consist of ooids of diameter 0.25–2 millimetres; rocks composed of ooids larger than 2 mm are called pisolites . The term oolith can refer to oolite or individual ooids. Ooids are most commonly composed of calcium carbonate ( calcite or aragonite ), but can be composed of phosphate, clays, chert , dolomite or iron minerals, including hematite . Dolomitic and chert ooids are most likely

24613-570: The very end of the Triassic, while most other temnospondyls were already extinct. Terrestrial reptile faunas were dominated by archosauromorphs during the Triassic, particularly phytosaurs and members of Pseudosuchia (the reptile lineage which leads to modern crocodilians ). In the Early Jurassic and onwards, dinosaurs and pterosaurs became the most common land reptiles, while small reptiles were mostly represented by lepidosauromorphs (such as lizards and tuatara relatives). Among pseudosuchians, only small crocodylomorphs did not become extinct by

24776-415: The volcanic eruption theory because the Newark Supergroup , a section of rock in eastern North America that records the Triassic–Jurassic boundary, contains no ash-fall horizons and because its oldest basalt flows were estimated to lie around 10 m above the transition zone, which they estimated to have occurred 610 kyr after the TJME. Also among their objections was that the Triassic-Jurassic boundary

24939-405: The world's major landmasses were coalesced into the supercontinent Pangaea , which during the Early Jurassic began to break up into northern supercontinent Laurasia and the southern supercontinent Gondwana . The rifting between North America and Africa was the first to initiate, beginning in the early Jurassic, associated with the emplacement of the Central Atlantic Magmatic Province . During

25102-514: Was affected by the TJME much more severely than marine fauna. One of the earliest pieces of evidence for a Late Triassic extinction was a major turnover in terrestrial tetrapods such as amphibians, reptiles, and synapsids. Edwin H. Colbert drew parallels between the system of extinction and adaptation between the Triassic–Jurassic and Cretaceous–Paleogene boundaries. He recognized how dinosaurs, lepidosaurs ( lizards and their relatives), and crocodyliforms ( crocodilians and their relatives) filled

25265-412: Was emitted quickly and in enormous quantities compared to other periods of Earth's history, rate of carbon dioxide emissions was one of the most meteoric rises in carbon dioxide levels in Earth's entire history. It is estimated that a single volcanic pulse from the large igneous province would have emitted an amount of carbon dioxide roughly equivalent to projected anthropogenic carbon dioxide emissions for

25428-645: Was enhanced and exacerbated by widespread photic zone euxinia through organic matter respiration and carbon dioxide release. Off the shores of the Wrangellia Terrane, the onset of photic zone euxinia was preceded by an interval of limited nitrogen availability and increased nitrogen fixation in surface waters while euxinia developed in bottom waters. In what is now northwestern Europe, shallow seas became salinity stratified, enabling easy development of anoxia. Reduced salinity, in conjunction with increased influx of terrestrial organic matter, enkindled anoxia in

25591-527: Was first defined and introduced into scientific literature by Alcide d'Orbigny in 1842. It takes its name from the French town of Semur-en-Auxois , near Dijon . The original definition of Sinemurian included what is now the Hettangian. The GSSP of the Sinemurian is located at a cliff face north of the hamlet of East Quantoxhead , 6 kilometres east of Watchet , Somerset , England , within the Blue Lias , and

25754-566: Was governed by the 405 kyr eccentricity cycle. Thanks to the breakup of Pangaea, the hydrological cycle during the Jurassic was significantly enhanced. The beginning of the Jurassic was likely marked by a thermal spike corresponding to the Triassic–Jurassic extinction and eruption of the Central Atlantic magmatic province. The first part of the Jurassic was marked by the Early Jurassic Cool Interval between 199 and 183 million years ago. It has been proposed that glaciation

25917-637: Was named by Alcide d'Orbigny in 1852, originally the base at the contact between the Forest Marble Formation and the Cornbrash Formation . However, this boundary was later found to be within the upper part of the Bathonian. The base of the Callovian does not yet have a certified GSSP. The working definition for the base of the Callovian is the first appearance of ammonites belonging to the genus Kepplerites . The Oxfordian

26080-589: Was poorly defined and the CAMP eruptions poorly constrained temporally. However, updated dating protocol and wider sampling has confirmed that the CAMP eruptions started in Morocco only a few thousand years before the extinction, preceding their onset in Nova Scotia and New Jersey , and that they continued in several more pulses for the next 600,000 years. Volcanic global warming has also been criticised as an explanation because some estimates have found that

26243-487: Was present in the Northern Hemisphere during both the early Pliensbachian and the latest Pliensbachian. There was a spike in global temperatures of around 4–8 °C (7–14 °F) during the early part of the Toarcian corresponding to the Toarcian Oceanic Anoxic Event and the eruption of the Karoo-Ferrar large igneous provinces in southern Gondwana, with the warm interval extending to the end of

26406-685: Was ratified in 2000. The beginning of the Sinemurian is defined by the first appearance of the ammonite Vermiceras quantoxense . Albert Oppel in 1858 named the Pliensbachian Stage after the hamlet of Pliensbach in the community of Zell unter Aichelberg in the Swabian Alb , near Stuttgart , Germany. The GSSP for the base of the Pliensbachian is found at the Wine Haven locality in Robin Hood's Bay , Yorkshire , England, in

26569-429: Was ratified in 2021. The boundary is defined by the first appearance of ammonites marking the boreal Bauhini Zone and the subboreal Baylei Zone. The Tithonian was introduced in scientific literature by Albert Oppel in 1865. The name Tithonian is unusual in geological stage names because it is derived from Greek mythology rather than a place name. Tithonus was the son of Laomedon of Troy and fell in love with Eos ,

#667332