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Permian–Triassic Extinction Event

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Permian–Triassic Extinction Event Permian–Triassic extinction event The Permian–Triassic extinction event, also [2] known as the P–Tr extinction, the P–T % Marine extinction intensity during the Phanerozoic extinction,[3] the End-Permian Extinction,[4] and colloquially as the Great Dying,[5] formed P–Tr the boundary between the Permian and Triassic geologic periods, as well as between the Cap K–Pg Paleozoic and Mesozoic eras, approximately O–S Tr–J Late D 252 million years ago. It is the Earth's most (H) severe known extinction event, with up to 96% of all marine species[6][7] and 70% of terrestrial vertebrate species becoming extinct.[8] It was the largest known mass extinction of insects. Millions of years ago Some 57% of all biological families and 83% of all genera became extinct. Plot of extinction intensity (percentage of marine genera that are present in each interval of time but do not exist [1] There is evidence for one to three distinct in the following interval) vs time in the past. Geological [8][9][10][11] periods are annotated (by abbreviation and colour) pulses, or phases, of extinction. above. The Permian–Triassic extinction event is the Potential causes for those pulses include one or most significant event for marine genera, with just over more large meteor impact events, massive 50% (according to this source) perishing. (source and volcanic eruptions (such as the Siberian image info) Traps[12]), and climate change brought on by large releases of underwater methane or methane-producing microbes.[13] The speed of the recovery from the extinction is disputed. Some scientists estimate that it took 10 million years (until the Middle Triassic), due both to the severity of the extinction and because grim conditons returned periodically for another 5 million years.[14] However, studies in Bear Lake County, near Paris, Idaho, showed a relatively quick rebound in a localized Early Triassic marine ecosystem, taking around 2 million years to recover,[15] suggesting that the impact of the extinction may have been felt less severely in some areas than others. Contents Dating Extinction patterns Marine organisms Terrestrial invertebrates Terrestrial plants Plant ecosystem response Coal gap Terrestrial vertebrates Possible explanations Biotic recovery Changes in marine ecosystems Land vertebrates Theories about cause Impact event Possible impact sites Volcanism Methane hydrate gasification Anoxia Hydrogen sulfide emissions Supercontinent Pangaea Encounter with spiral arm Microbes Combination of causes See also References Further reading External links Dating Until 2000, it was thought that rock sequences spanning the Permian–Triassic boundary were too Permian–Triassic extinction few and contained too many gaps for scientists to -238 — [19] reliably determine its details. However, it is now – possible to date the extinction with millennial Scleractinian -240 — T Ladinian ← precision. U–Pb zircon dates from five volcanic ash corals & calcified r sponges[16] beds from the Global Stratotype Section and Point –M i e M for the Permian–Triassic boundary at Meishan, -242 — a i s s d China, establish a high-resolution age model for the –o s d ←Corals return[18] z l extinction – allowing exploration of the links i e 13 -244 —o δ C stabilises at between global environmental perturbation, carbon c Anisian +2 ‰. Calcified – i ← cycle disruption, mass extinction, and recovery at c green algae -246 — ← millennial timescales. The extinction occurred Freutlul rrne.c[o16v]ery of [17] between 251.941 ± 0.037 and 251.880 ± 0.031 Ma – woody trees [20] -248 — ago, a duration of 60 ± 48 ka. A large E – a (approximately 0.9%), abrupt global decrease in the r Olenekian 13 12 l ratio of the stable isotope C to that of C, -250 — y [17][21][22][23][24] coincides with this extinction, and – is sometimes used to identify the Permian–Triassic ←Extinction event -252 — Induan boundary in rocks that are unsuitable for – radiometric dating.[25] Further evidence for Changhsingian -254 —P environmental change around the P–Tr boundary L a o suggests an 8 °C (14 °F) rise in temperature,[17] and – p l i n -256 —e P g 256 e P g an increase in CO levels by 2000 ppm (for o e i 2 – a Wuchiapingian comparison, the concentration immediately before z r n -258 —o m the industrial revolution was 280 ppm,[17] and the – i i amount today is about 410 ppm[26]). There is also c a -260 — nG evidence of increased ultraviolet radiation reaching u the earth, causing the mutation of plant spores.[17] – a da Capitanian -262 — ul It has been suggested that the Permian–Triassic boundary is associated with a sharp increase in the An approximate timescale of events around abundance of marine and terrestrial fungi, caused by the P–Tr boundary. Axis scale: millions of years ago. the sharp increase in the amount of dead plants and animals fed upon by the fungi.[27] For a while this ↓ PreЄ Є O S D C P T J K Pg N "fungal spike" was used by some paleontologists to identify the Permian–Triassic boundary in rocks that are unsuitable for radiometric dating or lack suitable index fossils, but even the proposers of the fungal spike hypothesis pointed out that "fungal spikes" may have been a repeating phenomenon created by the post-extinction ecosystem in the earliest Triassic.[27] The very idea of a fungal spike has been criticized on several grounds, including: Reduviasporonites, the most common supposed fungal spore, may be a fossilized alga;[17][28] the spike did not appear worldwide;[29][30] and in many places it did not fall on the Permian–Triassic boundary.[31] The reduviasporonites may even represent a transition to a lake- dominated Triassic world rather than an earliest Triassic zone of death and decay in some terrestrial fossil beds.[32] Newer chemical evidence agrees better with a fungal origin for Reduviasporonites, diluting these critiques.[33] Uncertainty exists regarding the duration of the overall extinction and about the timing and duration of various groups' extinctions within the greater process. Some evidence suggests that there were multiple extinction pulses[8] or that the extinction was spread out over a few million years, with a sharp peak in the last million years of the Permian.[31][34] Statistical analyses of some highly fossiliferous strata in Meishan, Zhejiang Province in southeastern China, suggest that the main extinction was clustered around one peak.[9] Recent research shows that different groups became extinct at different times; for example, while difficult to date absolutely, ostracod and brachiopod extinctions were separated by 670,000 to 1.17 million years.[35] In a well-preserved sequence in east Greenland, the decline of animals is concentrated in a period 10,000 to 60,000 years long, with plants taking an additional several hundred thousand years to show the full impact of the event.[36] An older theory, still supported in some recent papers,[8][37] is that there were two major extinction pulses 9.4 million years apart, separated by a period of extinctions well above the background level, and that the final extinction killed off only about 80% of marine species alive at that time while the other losses occurred during the first pulse or the interval between pulses. According to this theory one of these extinction pulses occurred at the end of the Guadalupian epoch of the Permian.[8][38] For example, all but one of the surviving dinocephalian genera died out at the end of the Guadalupian,[37] as did the Verbeekinidae, a family of large-size fusuline foraminifera.[39] The impact of the end-Guadalupian extinction on marine organisms appears to have varied between locations and between taxonomic groups — brachiopods and corals had severe losses.[40][41] Extinction patterns Marine Genera Marine organisms Notes extinctions extinct Marine invertebrates suffered the greatest losses during the P–Tr extinction. Evidence of this was Arthropoda found in samples from south China sections at May have become the P–Tr boundary. Here, 286 out of 329 marine Eurypterids 100% extinct shortly before the P–Tr boundary invertebrate genera disappear within the final two sedimentary zones containing conodonts Ostracods 59% [9] from the Permian. The decrease in diversity In decline since the Devonian; only 2 genera was probably caused by a sharp increase in Trilobites 100% extinctions, rather than a decrease in living before the extinction speciation.[43] Brachiopoda The extinction primarily affected organisms Orthids and productids Brachiopods 96% with calcium carbonate skeletons, especially died out those reliant on stable CO2 levels to produce Bryozoa their skeletons.[44] These organisms were Fenestrates, susceptible to the effects of the ocean Bryozoans 79% trepostomes, and acidification that resulted from increased cryptostomes died out atmospheric CO2. Chordata Among benthic organisms the extinction event In decline since the Acanthodians 100% Devonian, with only one multiplied background extinction rates, and living family therefore caused maximum species loss to taxa Cnidaria that had a high background extinction rate (by [45][46] Tabulate and rugose implication, taxa with a high turnover). Anthozoans 96% The extinction rate of marine organisms was corals died out catastrophic.[9][47][48][49] Echinodermata May have become Surviving marine invertebrate groups included Blastoids 100% extinct shortly before articulate brachiopods (those with a hinge),[50] the P–Tr boundary which had undergone a slow decline in numbers Inadunates and Crinoids 98% since the P–Tr extinction; the Ceratitida order of camerates
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