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79-476: See text Perisphinctoidea , formerly Perisphinctaceae , is a superfamily of Middle Jurassic (Bajocian) to Lower Cretaceous (Barremian) ammonites , commonly with evolute shells with strong ribbing that typically divides about mid flank before crossing the venter. Some 16 families have been recognized in the Perisphinctoidea. The following is based on Donovan et al. 1981 with modification from

158-711: 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

237-499: 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

316-647: 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

395-453: 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

474-492: 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

553-743: Is a stub . You can help Misplaced Pages by expanding it . Jurassic 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

632-604: Is a group of mountain ranges with similarity in form, structure, and alignment that have arisen from the same cause, usually an orogeny . Mountain ranges are formed by a variety of geological processes, but most of the significant ones on Earth are the result of plate tectonics . Mountain ranges are also found on many planetary mass objects in the Solar System and are likely a feature of most terrestrial planets . Mountain ranges are usually segmented by highlands or mountain passes and valleys . Individual mountains within

711-538: Is at work while the mountains are being uplifted until the mountains are reduced to low hills and plains. The early Cenozoic uplift of the Rocky Mountains of Colorado provides an example. As the uplift was occurring some 10,000 feet (3,000 m) of mostly Mesozoic sedimentary strata were removed by erosion over the core of the mountain range and spread as sand and clays across the Great Plains to

790-494: 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,

869-565: 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

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948-470: 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

1027-618: 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

1106-475: 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

1185-577: 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

1264-707: 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 ,

1343-622: 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

1422-865: The Alpide belt . The Pacific Ring of Fire includes the Andes of South America, extends through the North American Cordillera , the Aleutian Range , on through Kamchatka Peninsula , Japan , Taiwan , the Philippines , Papua New Guinea , to New Zealand . The Andes is 7,000 kilometres (4,350 mi) long and is often considered the world's longest mountain system. The Alpide belt stretches 15,000 km across southern Eurasia , from Java in Maritime Southeast Asia to

1501-551: The Annamite Range . If the definition of a mountain range is stretched to include underwater mountains, then the Ocean Ridge forms the longest continuous mountain system on Earth, with a length of 65,000 kilometres (40,400 mi). The position of mountain ranges influences climate, such as rain or snow. When air masses move up and over mountains, the air cools, producing orographic precipitation (rain or snow). As

1580-804: The Iberian Peninsula in Western Europe , including the ranges of the Himalayas , Karakoram , Hindu Kush , Alborz , Caucasus , and the Alps . The Himalayas contain the highest mountains in the world, including Mount Everest , which is 8,848 metres (29,029 ft) high. Mountain ranges outside these two systems include the Arctic Cordillera , Appalachians , Great Dividing Range , East Siberians , Altais , Scandinavians , Qinling , Western Ghats , Vindhyas , Byrrangas , and

1659-513: 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

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1738-728: 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

1817-622: The Treatise on Invertebrate Paleontology, Part L (1957) (Middle Jurassic direct derivatives of the Perisphinctidae) (early Upper Jurassic (Oxfordian) derivatives of Perisphinctidae) (mid Upper Jurassic (Kimmeridgian) derivatives of the Ataxioceratidae) (late Upper Jurassic (Tithonian) derivatives of Perisphinctidae) (Lower Cretaceous Perisphinctoidea (Berriasan - Hauterivien) This Ammonitina -related article

1896-636: 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

1975-748: 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

2054-593: 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

2133-560: 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

2212-655: 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

2291-464: 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

2370-519: 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

2449-792: 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

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2528-483: 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

2607-420: 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. Mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt

2686-513: 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

2765-797: 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

2844-686: 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

2923-572: 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

3002-713: 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

3081-526: The Late Jurassic (Kimmeridgian) of Scotland, which remains 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

3160-416: 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 )

3239-501: 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

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3318-653: 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

3397-462: 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

3476-502: 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

3555-414: 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

3634-529: 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

3713-575: The air descends on the leeward side, it warms again (following the adiabatic lapse rate ) and is drier, having been stripped of much of its moisture. Often, a rain shadow will affect the leeward side of a range. As a consequence, large mountain ranges, such as the Andes, compartmentalize continents into distinct climate regions . Mountain ranges are constantly subjected to erosional forces which work to tear them down. The basins adjacent to an eroding mountain range are then filled with sediments that are buried and turned into sedimentary rock . Erosion

3792-489: 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

3871-428: 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

3950-407: 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

4029-447: 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"

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4108-485: The east. This mass of rock was removed as the range was actively undergoing uplift. The removal of such a mass from the core of the range most likely caused further uplift as the region adjusted isostatically in response to the removed weight. Rivers are traditionally believed to be the principal cause of mountain range erosion, by cutting into bedrock and transporting sediment. Computer simulation has shown that as mountain belts change from tectonically active to inactive,

4187-616: The end of 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

4266-413: 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

4345-405: 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

4424-417: 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

4503-449: 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

4582-403: 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

4661-409: 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,

4740-402: 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

4819-410: 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

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4898-416: 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

4977-403: 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

5056-428: 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

5135-422: 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

5214-404: 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

5293-559: 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

5372-516: The rate of erosion drops because there are fewer abrasive particles in the water and fewer landslides. Mountains on other planets and natural satellites of the Solar System, including the Moon , are often isolated and formed mainly by processes such as impacts, though there are examples of mountain ranges (or "Montes") somewhat similar to those on Earth. Saturn 's moon Titan and Pluto , in particular, exhibit large mountain ranges in chains composed mainly of ices rather than rock. Examples include

5451-420: 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

5530-419: The same mountain range do not necessarily have the same geologic structure or petrology . They may be a mix of different orogenic expressions and terranes , for example thrust sheets , uplifted blocks , fold mountains, and volcanic landforms resulting in a variety of rock types . Most geologically young mountain ranges on the Earth's land surface are associated with either the Pacific Ring of Fire or

5609-457: 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

5688-407: 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

5767-585: The yew family ( Taxaceae ) is Palaeotaxus rediviva , from 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

5846-474: 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

5925-629: 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

6004-639: 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

6083-546: 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

6162-687: 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

6241-430: 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 ,

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