Jurassic

Last updated
Jurassic Period
201.3–145 million years ago
Scotese 170 ma.png

A map of the world as it appeared during the Middle Jurassic. (170 ma)

Contents

Mean atmospheric O
2
content over period duration
c. 26 vol %
(130 % of modern level)
Mean atmospheric CO
2
content over period duration
c. 1950 ppm
(7 times pre-industrial level)
Mean surface temperature over period durationc. 16.5 °C
(3 °C above modern level)
Key events in the Jurassic
-205 
-200 
-195 
-190 
-185 
-180 
-175 
-170 
-165 
-160 
-155 
-150 
-145 
how to approximate the timescale of key Jurassic events.
Vertical axis: millions of years ago.

The Jurassic ( /ʊˈræs.sɪk/ juu-RASS-ik; [1] from the Jura Mountains) is a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period 145 Mya. [note 1] The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, and the Tithonian event at the end; [4] neither event ranks among the "Big Five" mass extinctions, however.

The Jurassic period 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 of rock formations.

The Jurassic is named after the Jura Mountains in the European Alps, where limestone strata from the period were first identified. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, and many of the arid deserts of the Triassic were replaced by lush rainforests.

On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to an aquatic mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates.

Etymology

The name "Jura" is derived from the Celtic root *jor via Gaulish *iuris "wooded mountain", which, borrowed into Latin as a place name, evolved into Juria and finally Jura. [5] [6] [7]

The chronostratigraphic term "Jurassic" is directly linked to the Jura Mountains, a mountain range mainly following the course of the France–Switzerland border. During a tour of the region in 1795, [note 2] Alexander von Humboldt recognized the mainly limestone dominated mountain range of the Jura Mountains as a separate formation that had not been included in the established stratigraphic system defined by Abraham Gottlob Werner, and he named it "Jura-Kalkstein" ('Jura limestone') in 1799. [note 3] [5] [6] [10]

Thirty years later, in 1829, the French naturalist Alexandre Brongniart published a survey on the different terrains that constitute the crust of the Earth. In this book, Brongniart referred to the terrains of the Jura Mountains as terrains jurassiques, thus coining and publishing the term for the first time. [11]

Divisions

The Jurassic period 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 of rock formations, also known as Lias, Dogger and Malm in Europe. [12] The separation of the term Jurassic into three sections originated with Leopold von Buch. [10] The faunal stages from youngest to oldest are:

Upper/Late Jurassic
Tithonian (152.1± 4145± 4 Mya)
Kimmeridgian (157.3± 4152.1± 4 Mya)
Oxfordian (163.5± 4157.3± 4 Mya)
Middle Jurassic
Callovian (166.1± 4163.5± 4 Mya)
Bathonian (168.3± 3.5166.1± 4 Mya)
Bajocian (170.3± 3168.3± 3.5 Mya)
Aalenian (174.1± 2170.3± 3 Mya)
Lower/Early Jurassic
Toarcian (182.7± 1.5174.1± 2 Mya)
Pliensbachian (190.8± 1.5182.7± 1.5 Mya)
Sinemurian (199.3± 1190.8± 1.5 Mya)
Hettangian (201.3± 0.6199.3± 1 Mya)

Paleogeography and tectonics

Pangaea at the start of Jurassic Pangaea 200Ma.jpg
Pangaea at the start of Jurassic
Depiction of Early Jurassic environment preserved at the St. George Dinosaur Discovery Site at Johnson Farm, with Dilophosaurus wetherilli in bird-like resting pose Dilophosaurus wetherilli.jpg
Depiction of Early Jurassic environment preserved at the St. George Dinosaur Discovery Site at Johnson Farm, with Dilophosaurus wetherilli in bird-like resting pose
The breakup of Gondwanaland took place during the Late Jurassic, the Indian Ocean opened up as a result Opening of western Indian Ocean 150 Ma.png
The breakup of Gondwanaland took place during the Late Jurassic, the Indian Ocean opened up as a result

During the early Jurassic period, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Gulf of Mexico opened in the new rift between North America and what is now Mexico's Yucatán Peninsula. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous period, when Gondwana itself rifted apart. [13] The Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of a glacier having appeared. As in the Triassic, there was apparently no land over either pole, and no extensive ice caps existed.

The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of that future landmass was submerged under shallow tropical seas; famous locales include the Jurassic Coast World Heritage Site in southern England and the renowned late Jurassic lagerstätten of Holzmaden and Solnhofen in Germany. [14] In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface. [15] Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation.

The Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, and invertebrate faunas with dominantly calcitic skeletons. [16]

The first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. [17] Important Jurassic exposures are also found in Russia, India, South America, Japan, Australasia and the United Kingdom.

In Africa, Early Jurassic strata are distributed in a similar fashion to Late Triassic beds, with more common outcrops in the south and less common fossil beds which are predominated by tracks to the north. [18] As the Jurassic proceeded, larger and more iconic groups of dinosaurs like sauropods and ornithopods proliferated in Africa. [18] Middle Jurassic strata are neither well represented nor well studied in Africa. [18] Late Jurassic strata are also poorly represented apart from the spectacular Tendaguru fauna in Tanzania. [18] The Late Jurassic life of Tendaguru is very similar to that found in western North America's Morrison Formation. [18]

Fauna

Aquatic and marine

During the Jurassic period, the primary vertebrates living in the sea were fish and marine reptiles. The latter include ichthyosaurs, which were at the peak of their diversity, plesiosaurs, pliosaurs, and marine crocodiles of the families Teleosauridae and Metriorhynchidae. [19] Numerous turtles could be found in lakes and rivers. [20] [21]

In the invertebrate world, several new groups appeared, including rudists (a reef-forming variety of bivalves) and belemnites. Calcareous sabellids ( Glomerula ) appeared in the Early Jurassic. [22] [23] The Jurassic also had diverse encrusting and boring (sclerobiont) communities, and it saw a significant rise in the bioerosion of carbonate shells and hardgrounds. Especially common is the ichnogenus (trace fossil) Gastrochaenolites . [24]

During the Jurassic period, about four or five of the twelve clades of planktonic organisms that exist in the fossil record either experienced a massive evolutionary radiation or appeared for the first time. [12]

Terrestrial

Terrestrial environment of the Toarcian of Leczna (Ciechocinek Formation, Lublin, Poland), based on the Bogdanka Coal Mine Flora. Dinosaurs are based on material found on various locations of the formation Ciechocinek Formation Reconstruction.jpg
Terrestrial environment of the Toarcian of Łęczna (Ciechocinek Formation, Lublin, Poland), based on the Bogdanka Coal Mine Flora. Dinosaurs are based on material found on various locations of the formation

On land, various archosaurian reptiles remained dominant. The Jurassic was a golden age for the large herbivorous dinosaurs known as the sauropods Camarasaurus , Apatosaurus , Diplodocus , Brachiosaurus , and many others—that roamed the land late in the period; their foraging grounds were either the prairies of ferns, palm-like cycads and bennettitales, or the higher coniferous growth, according to their adaptations. The smaller Ornithischian herbivore dinosaurs, like stegosaurs and small ornithopods were less predominant, but played important roles. They were preyed upon by large theropods, such as Ceratosaurus , Megalosaurus , Torvosaurus and Allosaurus , all these belong to the 'lizard hipped' or saurischian branch of the dinosaurs. [25]

During the Late Jurassic, the first avialans, like Archaeopteryx , evolved from small coelurosaurian dinosaurs. In the air, pterosaurs were common; they ruled the skies, filling many ecological roles now taken by birds, [26] and may have already produced some of the largest flying animals of all time. [27] [28] Within the undergrowth were various types of early mammals, as well as tritylodonts , lizard-like sphenodonts, and early lissamphibians. The rest of the Lissamphibia evolved in this period, introducing the first salamanders and caecilians. [29]

Flora

Conifers were the dominant land plants of the Jurassic Douglas fir leaves and bud.jpg
Conifers were the dominant land plants of the Jurassic
Various dinosaurs roamed forests of similarly large conifers during the Jurassic period. Europasaurus holgeri Scene 2.jpg
Various dinosaurs roamed forests of similarly large conifers during the Jurassic period.

The arid, continental conditions characteristic of the Triassic steadily eased during the Jurassic period, especially at higher latitudes; the warm, humid climate allowed lush jungles to cover much of the landscape. [30] Gymnosperms were relatively diverse during the Jurassic period. [12] The Conifers in particular dominated the flora, as during the Triassic; they were the most diverse group and constituted the majority of large trees.

Extant conifer families that flourished during the Jurassic included the Araucariaceae, Cephalotaxaceae, Pinaceae, Podocarpaceae, Taxaceae and Taxodiaceae. [31] The extinct Mesozoic conifer family Cheirolepidiaceae dominated low latitude vegetation, as did the shrubby Bennettitales. [32] Cycads, similar to palm trees, were also common, as were ginkgos and Dicksoniaceous tree ferns in the forest. [12] Smaller ferns were probably the dominant undergrowth. Caytoniaceous seed ferns were another group of important plants during this time and are thought to have been shrub to small-tree sized. [33] Ginkgo plants were particularly common in the mid- to high northern latitudes. [12] In the Southern Hemisphere, podocarps were especially successful, while Ginkgos and Czekanowskiales were rare. [30] [32]

In the oceans, modern coralline algae appeared for the first time. [12] However, they were a part of another major extinction that happened within the next major time period.

Since the early 1990s, the term Jurassic has been popularised by the Jurassic Park franchise, which started in 1990 with Michael Crichton's novel of the same title and its film adaptation, first released in 1993.

See also

Related Research Articles

Cretaceous Third and last period of the Mesozoic Era 145-66 million years ago

The Cretaceous is a geological period that lasted from about 145 to 66 million years ago (mya). It is the third and final period of the Mesozoic Era, as well as the longest. At nearly 80 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, 'chalk', which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation Kreide.

The Mesozoic Era is an interval of geological time from about 252 to 66 million years ago. It is also called the Age of Reptiles and the Age of Conifers.

Permian Sixth and last period of the Paleozoic Era 299-252 million years ago

The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous period 298.9 million years ago (Mya), to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic era; the following Triassic period belongs to the Mesozoic era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the region of Perm in Russia.

The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 541 million years to the present, and it began with the Cambrian Period when animals first developed hard shells preserved in the fossil record. The time before the Phanerozoic, called the Precambrian, is now divided into the Hadean, Archaean and Proterozoic eons.

Triassic First period of the Mesozoic Era 252-201 million years ago

The Triassic is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first and shortest period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic period is subdivided into three epochs: Early Triassic, Middle Triassic and Late Triassic.

Tethys Ocean Mesozoic ocean between Gondwana and Laurasia

The Tethys Ocean, also called the Tethys Sea or the Neotethys, was an ocean during much of the Mesozoic Era located between the ancient continents of Gondwana and Laurasia, before the opening of the Indian and Atlantic oceans during the Cretaceous Period.

Panthalassa Prehistoric superocean that surrounded Pangaea

Panthalassa, also known as the Panthalassic Ocean or Panthalassan Ocean, was the superocean that surrounded the supercontinent Pangaea. During the Paleozoic–Mesozoic transition c. 250 Ma it occupied almost 70% of Earth's surface. Its ocean floor has completely disappeared because of the continuous subduction along the continental margins on its circumference. Panthalassa is also referred to as the Paleo-Pacific or Proto-Pacific because the Pacific Ocean developed from its centre in the Mesozoic to the present.

Solnhofen Limestone

The Solnhofen Plattenkalk, or Solnhofen Limestone, geologically known as the Altmühltal Formation, is a Jurassic Konservat-Lagerstätte that preserves a rare assemblage of fossilized organisms, including highly detailed imprints of soft bodied organisms such as sea jellies. The most familiar fossils of the Solnhofen Plattenkalk include the early feathered theropod dinosaur Archaeopteryx preserved in such detail that they are among the most famous and most beautiful fossils in the world. The Solnhofen beds lie in the German state of Bavaria (Bayern), halfway between Nuremberg (Nürnberg) and Munich (München) and were originally quarried as a source of lithographic limestone. The Jura Museum situated in Eichstätt, Germany has an extensive exhibit of Jurassic fossils from the quarries of Solnhofen and surroundings, including marine reptiles, pterosaurs, and one specimen of the early bird Archaeopteryx.

Coelurosauria

Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.

The Carnian is the lowermost stage of the Upper Triassic series. It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by the Norian. Its boundaries are not characterized by major extinctions or biotic turnovers, but a climatic event occurred during the Carnian and seems to be associated with important extinctions or biotic radiations.

.

The Newark Supergroup, also known as the Newark Group, is an assemblage of Upper Triassic and Lower Jurassic sedimentary rocks which outcrop intermittently along the United States East Coast. They were deposited in a series of Triassic basins approximately 190 million years ago as North America separated from Africa. The exposures extend from Nova Scotia to North Carolina. Related basins are also found underwater in the Bay of Fundy. The group is named for the city of Newark, New Jersey.

Cimmeria (continent) An ancient string of microcontinents that rifted from Gondwana

Cimmeria was an ancient continent, or, rather, a string of microcontinents or terranes, that rifted from Gondwana in the Southern Hemisphere and was accreted to Eurasia in the Northern Hemisphere. It consisted of parts of what is today Turkey, Iran, Afghanistan, Tibet, Shan–Thai, and Malay Peninsula. Cimmeria rifted from the Gondwanan shores of the Paleo-Tethys Ocean during the Carboniferous-earliest Permian and as the Neo-Tethys Ocean opened behind it, during the Permian, the Paleo-Tethys closed in front of it. Cimmeria rifted off Gondwana from east to west, from Australia to the eastern Mediterranean. It stretched across several latitudes and spanned a wide range of climatic zones.

Geological history of Earth The sequence of major geological events in Earths past

The geological history of Earth follows the major events in Earth's past based on the geological time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System.

Gondwana Neoproterozoic to Carboniferous supercontinent

Gondwana or Gondwanaland was a supercontinent that existed from the Neoproterozoic until the Jurassic. Gondwana was not considered a supercontinent by the earliest definition, since the landmasses of Baltica, Laurentia, and Siberia were separate from it.

Dryolestoidea is an extinct clade of Mesozoic mammals that only contains two orders. It has been suggested that this group is closely related to modern therian mammals.

South German Scarplands

The South German Scarplands is a geological and geomorphological natural region or landscape in Switzerland and the south German states of Bavaria and Baden-Württemberg. The landscape is characterised by escarpments.

<i>Kayentavenator</i>

Kayentavenator is a genus of small carnivorous dinosaur that lived during the Early Jurassic Period; fossils were recovered from the Kayenta Formation of northeastern Arizona and were described in 2010.

Prehistory of the United States US History from the formation of the Earth to history in written form

The prehistory of the United States comprises the occurrences within regions now part of the United States of America during the interval of time spanning from the formation of the Earth to the documentation of local history in written form. At the start of the Paleozoic era, what is now "North" America was actually in the southern hemisphere. Marine life flourished in the country's many seas, although terrestrial life had not yet evolved. During the latter part of the Paleozoic, seas were largely replaced by swamps home to amphibians and early reptiles. When the continents had assembled into Pangaea drier conditions prevailed. The evolutionary precursors to mammals dominated the country until a mass extinction event ended their reign.

Lhasa terrane A fragment of crustal material, sutured to the Eurasian Plate during the Cretaceous that forms present-day southern Tibet

The Lhasa terrane is a terrane, or fragment of crustal material, sutured to the Eurasian Plate during the Cretaceous that forms present-day southern Tibet. It takes its name from the city of Lhasa in the Tibet Autonomous Region, China. The northern part may have originated in the East African Orogeny, while the southern part appears to have once been part of Australia. The two parts joined, were later attached to Asia, and then were impacted by the collision of the Indian Plate that formed the Himalayas.

References

Notes

  1. A 140 Ma age for the Jurassic-Cretaceous instead of the usually accepted 145 Ma was proposed in 2014 based on a stratigraphic study of Vaca Muerta Formation in Neuquén Basin, Argentina. [2] Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age, sees the study as a "first step" toward formally changing the age in the International Union of Geological Sciences. [3]
  2. "Ich hatte mich auf einer geognostischen Reise, die ich 1795 durch das südliche Franken, die westliche Schweiz und Ober-Italien machte, davon überzeugt, daß der Jura-Kalkstein, welchen Werner zu seinem Muschelkalk rechnete, eine eigne Formation bildete. In meiner Schrift über die unterirdischen Gasarten, welche mein Bruder Wilhelm von Humboldt 1799 während meines Aufenthalts in Südamerika herausgab, wird der Formation, die ich vorläufig mit dem Namen Jura-Kalkstein bezeichnete, zuerst gedacht." ('On a geological tour that I made in 1795 through southern France, western Switzerland and upper Italy, I convinced myself that the Jura limestone, which Werner included in his shell limestone, constituted a separate formation. In my paper about subterranean types of gases, which my brother Wilhelm von Humboldt published in 1799 during my stay in South America, the formation, which I provisionally designated with the name "Jura limestone", is first conceived.') [8]
  3. "[…] die ausgebreitete Formation, welche zwischen dem alten Gips und neueren Sandstein liegt, und welchen ich vorläufig mit dem Nahmen Jura-Kalkstein bezeichne." '… the widespread formation which lies between the old gypsum and the more recent sandstone and which I provisionally designate with the name "Jura limestone".' [9]

Citations

  1. "Jurassic". Dictionary.com Unabridged. Random House.
  2. Vennari et al. 2014, pp. 374-385.
  3. Jaramillo 2014.
  4. Hallam 1986, pp. 765-768.
  5. 1 2 Hölder 1964.
  6. 1 2 Arkell 1956.
  7. Rollier 1903.
  8. von Humboldt 1858, p. 632.
  9. von Humboldt 1799, p. 39.
  10. 1 2 Pieńkowski et al. 2008, pp. 823–922.
  11. Brongniart 1829.
  12. 1 2 3 4 5 6 Kazlev 2002.
  13. Scotese 2003.
  14. "Land and sea during the Jurassic". urweltmuseum.de. Archived from the original on 2007-07-14.
  15. "The North American Tapestry of Time and Terrain: Jurassic Rocks - 208 to 146 million years ago". nationalatlas.gov. Archived from the original on 2007-07-15.
  16. Stanley & Hardie 1998.
  17. Monroe & Wicander 1997, p. 607.
  18. 1 2 3 4 5 Jacobs 1997, pp. 2-4.
  19. Motani 2000.
  20. Wings et al. 2012, pp. 925-935.
  21. Gannon 2012.
  22. Vinn & Mutvei 2009, pp. 286-296.
  23. Vinn, ten Hove & Mutvei 2008, pp. 295–301.
  24. Taylor & Wilson 2003, pp. 1-103.
  25. Haines 2000.
  26. Feduccia 1996.
  27. Witton, Martill & Loveridge 2010, pp. 79-81.
  28. Witton 2016.
  29. Carroll 1988.
  30. 1 2 Haines 2000, p. 65.
  31. Behrensmeyer et al. 1992, p. 349.
  32. 1 2 Behrensmeyer et al. 1992, p. 352.
  33. Behrensmeyer et al. 1992, p. 353.

Sources

Further reading

  • Mader, Sylvia (2004). Biology (eighth ed.).CS1 maint: ref=harv (link)
  • Ogg, Jim (June 2004). Overview of Global Boundary Stratotype Sections and Points (GSSP's). International Commission on Stratigraphy. p. 17.CS1 maint: ref=harv (link)
  • Stanley, S.M.; Hardie, L.A. (1999). "Hypercalcification; paleontology links plate tectonics and geochemistry to sedimentology". GSA Today. 9: 1–7.CS1 maint: ref=harv (link)