Permian
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225408242
2008-07-13T15:00:21Z
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/* Permian-Triassic extinction event */
{{two other uses||the language family|Permic languages|the high school|Permian High School}}
{{Geological period
|from=299
|middle=270
|to=241
|image=LatePermianGlobal.jpg
|o2=23
|co2=900
|temp=16
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The '''Permian'''<ref>The term "Permian" was introduced into [[geology]] in 1841 by Sir [[Roderick Murchison|Sir R. I. Murchison]], president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with [[Edouard de Verneuil]]; Murchison asserted in 1841 that he named his "Permian system" after the ancient kingdom of [[Great Perm|Permia]], and not after the small town of [[Perm]], as usually assumed; see [http://www.earthscape.org/r3/erwin/erwin10.html "Origin of the Permian"]</ref> is a [[geologic period|geologic period and system]] that extends from 299.0 ± 0.8 [[annum|Ma]] to 251.0 ± 0.4 Ma (million years before the present) {{ICS 2004}}. It is the last period of the [[Paleozoic]] Era. The Permian period was named after the city of [[Perm]], [[Russia]] by Scottish geologist [[Roderick Murchison]] in 1841.
==Subdivisions==
The three primary subdivisions of the Permian Period are given below from youngest to oldest, and include [[faunal stage]]s also from youngest to oldest. Additional age/stage equivalents or subdivisions are given in parentheses. ''Epoch'' and ''age'' refer to time, and equivalents ''series'' and ''stage'' refer to the rocks.
[[Lopingian]] Epoch
:[[Changhsingian]] Age (Djulfian/Ochoan/Dewey Lake/Zechstein)
:[[Wuchiapingian]] Age (Dorashamian/Ochoan/Longtanian/Rustler/Salado/Castile/Zechstein)
[[Guadalupian]] Epoch
:[[Capitanian]] Age (Kazanian/Zechstein)
:[[Wordian]] Age (Kazanian/Zechstein)
:[[Roadian]] Age (Ufimian/Zechstein)
[[Cisuralian]] Epoch
:[[Kungurian]] Age (Irenian/Filippovian/Leonard/Rotliegendes)
:[[Artinskian]] Age (Baigendzinian/Aktastinian/Rotliegendes)
:[[Sakmarian]] Age (Sterlitamakian/Tastubian/Leonard/Wolfcamp/Rotliegendes)
:[[Asselian]] Age (Krumaian/Uskalikian/Surenian/Wolfcamp/Rotliegendes)
==Oceans==
[[Sea level]]s in the Permian remained generally low, and near-shore environments were limited by the collection of almost all major [[landmass]]es into a single continent -- [[Pangaea]]. One continent, even a very large one, has a smaller shoreline than six to eight smaller ones with the same total area. This could have in part caused the widespread extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms.
==Paleogeography==
[[Image:280 Ma plate tectonic reconstruction.png|thumb|230px|left|Geography of the Permian world]]
During the Permian, all the [[Earth]]'s major land masses except portions of [[East Asia|East]] [[Asia]] were collected into a single supercontinent known as [[Pangaea]]. Pangaea straddled the [[equator]] and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean ("[[Panthalassa]]", the "universal sea"), and the Paleo-Tethys Ocean, a large ocean that was between Asia and Gondwana. The [[Cimmeria plate|Cimmeria]] continent [[rift]]ed away from [[Gondwana]] and drifted north to [[Laurasia]], causing the [[Paleo-Tethys]] to shrink. A new ocean was growing on its southern end, the [[Tethys Ocean]], an ocean that would dominate much of the [[Mesozoic]] Era. Large continental landmasses create climates with extreme variations of heat and cold ("[[continental climate]]") and [[monsoon]] conditions with highly seasonal rainfall patterns. [[Desert]]s seem to have been widespread on Pangaea. Such dry conditions favored [[gymnosperm]]s, plants with [[seed]]s enclosed in a protective cover, over plants such as [[fern]]s that disperse [[spore]]s. The first modern [[tree]]s ([[Pinophyta|conifers]], [[ginkgo]]s and [[cycad]]s) appeared in the Permian.
Three general areas are especially noted for their Permian deposits- the [[Ural Mountains]] (where Perm itself is located), China, and the southwest of North America, where the [[Permian Basin]] in the [[United States|U.S.]] state of [[Texas]] is so named because it has one of the thickest deposits of Permian rocks in the world.
==Climate==
As the Permian opened, the [[Earth]] was still in the grip of an [[ice age]], so the polar regions were covered with deep layers of ice. [[Glacier]]s continued to cover much of [[Gondwanaland]], as they had during the late [[Carboniferous]].
The Permian Period, at the end of the Paleozoic era, marked a great changes in the Earth's climate and appearance. Towards the middle of the period the climate became warmer and milder, the glaciers receded, and the continental interiors became drier. Much of the interior of Pangaea was probably arid, with great seasonal fluctuations (wet and dry seasons), because of the lack of the moderating effect of nearby bodies of water. This drying tendency continued through to the late Permian, along with alternating warming and cooling periods.
==Life==
[[Image:Dimetr eryopsDB.jpg|thumb|''[[Dimetrodon]]'' and ''[[Eryops]]''- Early Permian, North America]]
[[Image:EdaphosaurusDB.jpg|thumb|left|''[[Edaphosaurus]] pogonias'' - Early Permian]]
[[Image:Ocher fauna DB.jpg|thumb|Ocher fauna - Early Middle Permian, Ural Region]]
[[Image:Titanophoneus 3.jpg|thumb|''[[Titanophoneus]]'' and ''[[Ulemosaurus]]'' - Ural Region]]
===Marine biota===
Permian marine deposits are rich in [[fossil]] [[mollusk]]s, [[echinoderm]]s, and [[brachiopod]]s. Fossilized shells of two kinds of [[invertebrate]]s are widely used to identify Permian strata and correlate them between sites: [[fusulinid]]s, a kind of shelled amoeba-like [[protist]] that is one of the [[foraminifera]]ns, and [[Ammonite|ammonoids]], shelled [[cephalopod]]s that are distant relatives of the modern [[nautilus]]. By the close of the Permian, [[trilobites]] and a host of other marine groups became extinct
===Terrestrial biota===
Terrestrial life in the Permian included diverse [[plant]]s, [[fungi]], [[arthropod]]s, and various types of [[Permian tetrapods|tetrapods]]. The period saw a massive [[desert]] covering the interior of the [[Pangaea]]. The warm zone spread in the northern hemisphere, where extensive dry desert appeared. The rock formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. A number of older types of plants and animals died out or became marginal elements.
The Permian began with the Carboniferous flora still flourishing. About the middle of the Permian there was a major transition in vegetation. The swamp-loving [[lycopod]] trees of the Carboniferous, such as ''[[Lepidodendron]]'' and ''[[Sigillaria]]'', were replaced by the more advanced [[conifers]], which were better adapted to the changing climatic conditions. The Permian saw the radiation of many important conifer groups, including the ancestors of many present-day families. Lycopods and [[swamp]] [[forest]]s still dominated the [[South China (continent)|South China]] continent because it was an isolated continent and it sat near or at the equator. Oxygen levels were probably high there. The [[ginkgo]]s and [[cycad]]s also appeared during this period. Rich forests were present in many areas, with a diverse mix of plant groups.
===Insects of the Permian===
By the [[Pennsylvanian]] and well into the Permian, by far the most successful were primitive [[Blattoptera|relatives of cockroaches]]. Six fast legs, two well developed folding wings, fairly good eyes, long, well developed antennae (olfactory), an omnivorous digestive system, a receptacle for storing sperm, a [[chitin]] skeleton that could support and protect, as well as form a gizzard and efficient mouth parts, gave it formidable advantages over other herbivorous animals. About 90% of insects were cockroach-like insects ("Blattopterans").<ref>Zimmerman EC (1948) Insects of Hawaii, Vol. II. Univ. Hawaii Press</ref>
The [[dragonflies]] ''Odonata'' were the dominant aerial predator and probably dominated terrestrial insect predation as well. True Odonata appeared in the Permian<ref>Grzimek HC Bernhard (1975) Grzimek's Animal Life Encyclopedia Vol 22 Insects. Van Nostrand Reinhold Co. NY.</ref><ref> Riek EF Kukalova-Peck J (1984) A new interpretation of dragonfly wing venation based on early Upper Carboniferous fossils from Argentina (Insecta: Odonatoida and basic character states in Pterygote wings.) Can. J. Zool. 62; 1150-1160.</ref> and all are [[amphibious]]. Their prototypes are the oldest winged fossils,<ref> Wakeling JM Ellington CP (1997) Dragonfly flight III lift and power requirements. Journal of Experimental Biology 200; 583-600, on p589</ref> go back to the [[Devonian]], and are different from other wings in every way.<ref> Matsuda R (1970) Morphology and evolution of the insect thorax. Mem. Ent. Soc. Can. 76; 1-431.</ref> Their prototypes may have had the beginnings of many modern attributes even by late [[Carboniferous]] and it is possible that they even captured small vertebrates, for some species had a wing span of 71 cm.<ref> Riek EF Kukalova-Peck J (1984) A new interpretation of dragonfly wing venation based on early Upper Carboniferous fossils from Argentina (Insecta: Odonatoida and basic character states in Pterygote wings.) Can. J. Zool. 62; 1150-1160</ref> A number of important new insect groups appeared at this time, including the [[Coleoptera]] (beetles) and [[Diptera]] (flies).
===Reptile and amphibian fauna===
Early Permian terrestrial faunas were dominated by [[pelycosaurs]] and [[amphibians]], the middle Permian by primitive [[therapsids]] such as the [[dinocephalia]], and the late Permian by more advanced therapsids such as [[gorgonopsia]]ns and [[dicynodont]]s. Towards the very end of the Permian the first [[Archosauriformes|archosaurs]] appeared, a group that would give rise to the [[dinosaur]]s in the [[Triassic|following period]]. Also appearing at the end of the Permian were the first [[cynodont]]s, which would go on to evolve into [[mammal]]s during the Triassic. Another group of therapsids, the [[therocephalia]]ns (such as ''[[Trochosaurus]]''), arose in the Middle Permian. There were no aerial vertebrates.
The Permian period saw the development of a fully terrestrial fauna and the appearance of the first [[megafauna|large]] [[herbivore]]s and [[carnivore]]s. It was the high tide of the [[anapsid]]es in the form of the massive [[Pareiasaur]]s and host of smaller, generally lizzard-like groups. A group of small reptiles, the [[diapsids]] started to abound. These were the ancestors to most modern reptiles and the ruling dinosaurs as well as pterosaurs and crocodiles.
Thriving also, were the early ancestors to mammals, the [[synapsid]]a, which included some large reptiles such as ''[[Dimetrodon]]''. Reptiles grew to dominance among vertebrates, because their special adaptations enabled them to flourish in the drier climate.
Permian amphibians consisted of [[temnospondyli]], [[lepospondyli]] and [[Batrachosauria|batrachosaurs]].
==Permian-Triassic extinction event==
[[Image:Extinction Intensity.svg|thumb|300px|right|The Permian–Triassic extinction event, labeled "End P" here, is the most significant extinction event in this plot for marine [[genus|genera]] which produce large numbers of [[fossils]].]]
{{Main|Permian–Triassic extinction event}}
The Permian ended with the most extensive [[extinction event]] recorded in [[paleontology]]: the [[Permian-Triassic extinction event]]. 90% to 95% of marine species became [[Extinction|extinct]], as well as 70% of all land organisms. On an individual level, perhaps as many as 99.5% of separate organisms died as a result of the event.<ref>http://www.historyfiles.co.uk/FeaturesAfrica/Permian_Extinction1.htm</ref>
There is also significant evidence that massive [[flood basalt]] eruptions from magma output lasting thousands of years in what is now the [[Siberian Traps]] contributed to environmental stress leading to mass extinction. The reduced coastal habitat and highly increased aridity probably also contributed. Based on the amount of lava estimated to have been produced during this period, the worst case scenario is an expulsion of enough carbon dioxide from the eruptions to raise world temperatures five degrees Celsius, not enough to kill off 95% of life.
Another hypothesis involves ocean venting of [[hydrogen sulfide]] gas. Portions of deep ocean will periodically lose all of its dissolved oxygen allowing bacteria that live without oxygen to flourish and produce hydrogen sulfide gas. If enough hydrogen sulfide accumulates in an [[Anoxic event|anoxic zone]], the gas can rise into the atmosphere.
Oxidizing gases in the atmosphere would destroy the toxic gas, but the hydrogen sulfide would soon consume all of the atmospheric gas available to change it. Hydrogen sulfide levels would increase dramatically over a few hundred years.
Modeling of such an event indicates that the gas would destroy [[ozone]] in the upper atmosphere allowing [[ultraviolet]] radiation to kill off species that had survived the toxic gas (Kump, ''et al'', 2005). Of course, there are species that can metabolize hydrogen sulfide.
Another hypothesis builds on the flood basalt eruption theory. Five degrees Celsius would not be enough increase in world temperatures to explain the death of 95% of life. But such warming could slowly raise ocean temperatures until frozen methane reservoirs below the ocean floor near coastlines (a current target for a new energy source) melted, expelling enough methane, among the most potent greenhouse gases, into the atmosphere to raise world temperatures an additional five degrees Celsius. The frozen methane hypothesis helps explain the increase in carbon-12 levels midway into the Permian-Triassic boundary layer. It also helps explain why the first phase of the layer's extinctions was land-based, the second was marine-based (and starting right after the increase in C-12 levels), and the third land-based again.
An even more speculative hypothesis is that intense radiation from a nearby [[supernova]] was responsible for the extinctions.
[[Trilobite]]s, which had thrived since [[Cambrian]] times, finally became extinct before the end of the Permian.
In [[2006]], a group of American scientists from [[Ohio State University]] reported evidence for a possible huge [[meteorite]] [[Impact crater|crater]] ([[Wilkes Land crater]]) with a diameter of around 500 kilometers in [[Antarctica]]. The crater is located at a depth of 1.6 kilometers beneath the ice of Wilkes Land in eastern Antarctica. The scientists speculate that this impact may have caused the Permian-Triassic extinction event, although its age is bracketed only between 100 million and 500 million years ago. They also speculate that it may have contributed in some way to the separation of [[Australia]] from the Antarctic landmass, which were both part of a [[supercontinent]] called [[Gondwana]]. Levels of iridium and quartz fracturing in the Permian-Triassic layer do not approach those of the [[K–T boundary|Cretaceous-Tertiary boundary layer]]. Given that a far greater proportion of species and individual organisms became extinct during the former, doubt is cast on the significance of a meteor impact in creating the latter. Further doubt has been cast on this theory based on fossils in Greenland showing the extinction to have been gradual, lasting about eighty thousand years, with three distinct phases.
The warm zone spread in the northern hemisphere, where extensive dry desert appeared. The rock formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. The old types of plants and animals died out.
Many scientists believe that the Permian-Triassic extinction event was caused by a combination of some or all of the hypotheses above and other factors; the formation of [[Pangaea]] decreased the number of coastal habitats and may have contributed to the extinction of many [[clades]].
==See also==
* [[List of fossil sites]] ''(with link directory)''
* [[Permian tetrapods]]
==Notes==
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{{reflist}}
==References==
* Ogg, Jim; June, 2004, ''Overview of Global Boundary Stratotype Sections and Points (GSSP's)'' http://www.stratigraphy.org/gssp.htm Accessed [[April 30]], [[2006]].
* {{cite journal
| author=Kump, L.R., A. Pavlov, and M.A. Arthur
| title=Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia
| journal=Geology
| volume=33 | issue=May | year=2005 | pages=397–400
| doi= 10.1130/G21295.1
}}
==External links==
{{Commonscat|Permian}}
*[http://www.ucmp.berkeley.edu/permian/permstrat.html University of California offers a more modern Permian stratigraphy]
*[http://www.ucmp.berkeley.edu/permian/glassmts.html Classic Permian strata in the Glass Mountains of the Permian Basin]
* {{cite web | title=International Commission on Stratigraphy (ICS)| work=Geologic Time Scale 2004| url=http://www.stratigraphy.org/ | accessmonthday=September 19 | accessyear=2005}}
* [http://www.geo-lieven.com/erdzeitalter/perm/perm.htm Examples of Permian Fossils]
{{Permian Footer}}
{{Paleozoic Footer}}
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