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An extinction event is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from disagreement as to what constitutes a "major" extinction event,and the data chosen to measure past diversity.
Approximately 251.9 million years ago,the Permian–Triassicextinction event forms the boundary between the Permian and Triassic geologic periods,and with them the Paleozoic and Mesozoic eras. It is Earth's most severe known extinction event,with the extinction of 57% of biological families,83% of genera,81% of marine species and 70% of terrestrial vertebrate species. It is also the greatest known mass extinction of insects. It is the greatest of the "Big Five" mass extinctions of the Phanerozoic. There is evidence for one to three distinct pulses,or phases,of extinction.
The Triassic is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago (Mya),to the beginning of the Jurassic Period 201.4 Mya. The Triassic is the first and shortest period of the Mesozoic Era and the seventh period of the Phanerozoic Eon. 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.
The Triassic–Jurassic (Tr-J) extinction event (TJME),often called the end-Triassic extinction,marks 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,dinosaurs,and pterosaurs became extinct;some of 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 Late Ordovician mass extinction (LOME),sometimes known as the end-Ordovician mass extinction or the Ordovician-Silurian extinction,is the first of the "big five" major mass extinction events in Earth's history,occurring roughly 445 million years ago (Ma). It is often considered to be the second-largest known extinction event just behind the end-Permian mass extinction,in terms of the percentage of genera that became extinct. Extinction was global during this interval,eliminating 49–60% of marine genera and nearly 85% of marine species. Under most tabulations,only the Permian-Triassic mass extinction exceeds the Late Ordovician mass extinction in biodiversity loss. The extinction event abruptly affected all major taxonomic groups and caused the disappearance of one third of all brachiopod and bryozoan families,as well as numerous groups of conodonts,trilobites,echinoderms,corals,bivalves,and graptolites. Despite its taxonomic severity,the Late Ordovician mass extinction did not produce major changes to ecosystem structures compared to other mass extinctions,nor did it lead to any particular morphological innovations. Diversity gradually recovered to pre-extinction levels over the first 5 million years of the Silurian period.
The Siberian Traps are a large region of volcanic rock,known as a large igneous province,in Siberia,Russia. The massive eruptive event that formed the traps is one of the largest known volcanic events in the last 500 million years.
The Late Devonian extinction consisted of several extinction events in the Late Devonian Epoch,which collectively represent one of the five largest mass extinction events in the history of life on Earth. The term primarily refers to a major extinction,the Kellwasser event,also known as the Frasnian-Famennian extinction,which occurred around 372 million years ago,at the boundary between the Frasnian age and the Famennian age,the last age in the Devonian Period. Overall,19% of all families and 50% of all genera became extinct. A second mass extinction called the Hangenberg event,also known as the end-Devonian extinction,occurred 359 million years ago,bringing an end to the Famennian and Devonian,as the world transitioned into the Carboniferous Period.
The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas,and dates between 272.95 ±0.5 –259.1 ±0.4 Mya. The series saw the rise of the therapsids,a minor extinction event called Olson's Extinction and a significant mass extinction called the end-Capitanian extinction event. The Guadalupian was previously known as the Middle Permian.
The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.9 Ma and 247.2 Ma. Rocks from this epoch are collectively known as the Lower Triassic Series,which is a unit in chronostratigraphy. The Early Triassic is the oldest epoch of the Mesozoic Era. It is preceded by the Lopingian Epoch and followed by the Middle Triassic Epoch. The Early Triassic is divided into the Induan and Olenekian ages. The Induan is subdivided into the Griesbachian and Dienerian subages and the Olenekian is subdivided into the Smithian and Spathian subages.
In the geologic timescale,the Olenekian is an age in the Early Triassic epoch;in chronostratigraphy,it is a stage in the Lower Triassic series. It spans the time between 251.2 Ma and 247.2 Ma. The Olenekian is sometimes divided into the Smithian and the Spathian subages or substages. The Olenekian follows the Induan and is followed by the Anisian.
The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale,spanning the time between 237 Ma and 201.4 Ma. It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. The corresponding series of rock beds is known as the Upper Triassic. The Late Triassic is divided into the Carnian,Norian and Rhaetian ages.
The clathrate gun hypothesis is a proposed explanation for the periods of rapid warming during the Quaternary. The hypothesis is that changes in fluxes in upper intermediate waters in the ocean caused temperature fluctuations that alternately accumulated and occasionally released methane clathrate on upper continental slopes. This would have had an immediate impact on the global temperature,as methane is a much more powerful greenhouse gas than carbon dioxide. Despite its atmospheric lifetime of around 12 years,methane's global warming potential is 72 times greater than that of carbon dioxide over 20 years,and 25 times over 100 years. It is further proposed that these warming events caused the Bond Cycles and individual interstadial events,such as the Dansgaard–Oeschger interstadials.
The Daptocephalus Assemblage Zone is a tetrapod assemblage zone or biozone found in the Adelaide Subgroup of the Beaufort Group,a majorly fossiliferous and geologically important Group of the Karoo Supergroup in South Africa. This biozone has outcrops located in the upper Teekloof Formation west of 24°E,the majority of the Balfour Formation east of 24°E,and the Normandien Formation in the north. It has numerous localities which are spread out from Colesberg in the Northern Cape,Graaff-Reniet to Mthatha in the Eastern Cape,and from Bloemfontein to Harrismith in the Free State. The Daptocephalus Assemblage Zone is one of eight biozones found in the Beaufort Group and is considered Late Permian (Lopingian) in age. Its contact with the overlying Lystrosaurus Assemblage Zone marks the Permian-Triassic boundary.
The Emeishan Traps constitute a flood basalt volcanic province,or large igneous province,in south-western China,centred in Sichuan province. It is sometimes referred to as the Permian Emeishan Large Igneous Province or Emeishan Flood Basalts. Like other volcanic provinces or "traps",the Emeishan Traps are multiple layers of igneous rock laid down by large mantle plume volcanic eruptions. The Emeishan Traps eruptions were serious enough to have global ecological and paleontological impact.
The end-Botomian mass extinction event,also known as the late early Cambrian extinctions,refer to two extinction intervals that occurred during Stages 4 and 5 of the Cambrian Period,approximately 513 to 509 million years ago. Estimates for the decline in global diversity over these events range from 50% of marine genera up to 80%. Among the organisms affected by this event were the small shelly fossils,archaeocyathids,trilobites,brachiopods,hyoliths,and mollusks.
Olson's Extinction was a mass extinction that occurred 273 million years ago in the late Cisuralian or early Guadalupian epoch of the Permian period,predating the much larger Permian–Triassic extinction event. The event is named after American paleontologist Everett C. Olson,who first identified the gap in fossil record indicating a sudden change between the early Permian and middle/late Permian faunas. Some authors also place a hiatus in the continental fossil record around that time,but others disagree. This event has been argued by some authors to have affected many taxa,including embryophytes,marine metazoans,and tetrapods.
The Carnian pluvial episode (CPE),often called the Carnian pluvial event,was a period of major change in global climate that coincided with significant changes in Earth's biota both in the sea and on land. It occurred during the latter part of the Carnian Stage,a subdivision of the late Triassic period,and lasted for perhaps 1–2 million years.
The Capitanian mass extinction event,also known as the end-Guadalupian extinction event,the Guadalupian-Lopingian boundary mass extinction,the pre-Lopingian crisis,or the Middle Permian extinction,was an extinction event that predated the end-Permian extinction event. The mass extinction occurred during a period of decreased species richness and increased extinction rates near the end of the Middle Permian,also known as the Guadalupian epoch. It is often called the end-Guadalupian extinction event because of its initial recognition between the Guadalupian and Lopingian series;however,more refined stratigraphic study suggests that extinction peaks in many taxonomic groups occurred within the Guadalupian,in the latter half of the Capitanian age. The extinction event has been argued to have begun around 262 million years ago with the Late Guadalupian crisis,though its most intense pulse occurred 259 million years ago in what is known as the Guadalupian-Lopingian boundary event.
The Balfour Formation is a geological formation that is found in the Beaufort Group,a major geological group that forms part of the greater Karoo Supergroup in South Africa. The Balfour Formation is the uppermost formation of the Adelaide Subgroup which contains all the Late Permian - Early Triassic aged biozones of the Beaufort Group. Outcrops and exposures of the Balfour Formation are found from east of 24 degrees in the highest mountainous escarpments between Beaufort West and Fraserburg,but most notably in the Winterberg and Sneeuberg mountain ranges near Cradock,the Baviaanskloof river valley,Graaff-Reniet and Nieu Bethesda in the Eastern Cape,and in the southern Free State province.
References
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{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ Wignall, Paul B. (1994). Black Shales. Oxford University Press. ISBN 0-19-854038-8. OCLC 29469074.
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- ↑ Wignall, P. B.; Newton, R. (1998-09-01). "Pyrite framboid diameter as a measure of oxygen deficiency in ancient mudrocks". American Journal of Science. 298 (7): 537–552. Bibcode:1998AmJS..298..537W. doi: 10.2475/ajs.298.7.537 . ISSN 0002-9599.
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{{cite book}}: CS1 maint: others (link) - ↑ Wignall, Paul B.; Benton, Michael J. (May 1999). "Lazarus taxa and fossil abundance at times of biotic crisis". Journal of the Geological Society. 156 (3): 453–456. Bibcode:1999JGSoc.156..453W. doi:10.1144/gsjgs.156.3.0453. ISSN 0016-7649. S2CID 130746408.
- ↑ "The Permian Extinction—When Life Nearly Came to an End | National Geographic Society". education.nationalgeographic.org. Retrieved 2022-07-07.
- ↑ Twitchett, Richard J.; Looy, Cindy V.; Morante, Ric; Visscher, Henk; Wignall, Paul B. (2001-04-01). "Rapid and synchronous collapse of marine and terrestrial ecosystems during the end-Permian biotic crisis". Geology. 29 (4): 351–354. Bibcode:2001Geo....29..351T. doi:10.1130/0091-7613(2001)029<0351:RASCOM>2.0.CO;2. ISSN 0091-7613.
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- ↑ Wignall, Paul B., Twitchett, Richard J. (2002). "Extent, duration, and nature of the Permian-Triassic superanoxic event". Geological Society of America Special Papers. 356: 395–413.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ↑ Sun, Yadong; Joachimski, Michael M.; Wignall, Paul B.; Yan, Chunbo; Chen, Yanlong; Jiang, Haishui; Wang, Lina; Lai, Xulong (2012-10-19). "Lethally Hot Temperatures During the Early Triassic Greenhouse". Science. 338 (6105): 366–370. Bibcode:2012Sci...338..366S. doi:10.1126/science.1224126. ISSN 0036-8075. PMID 23087244. S2CID 41302171.
- ↑ Song, Haijun; Wignall, Paul B.; Chu, Daoliang; Tong, Jinnan; Sun, Yadong; Song, Huyue; He, Weihong; Tian, Li (May 2015). "Anoxia/high temperature double whammy during the Permian-Triassic marine crisis and its aftermath". Scientific Reports. 4 (1): 4132. doi:10.1038/srep04132. ISSN 2045-2322. PMC 3928575 . PMID 24549265.
- 1 2 Wignall, Paul B. (2017). The Worst of Times: How Life on Earth Survived Eighty Million Years of Extinctions. Princeton University Press. pp. 1–224. ISBN 978-0691176024.
- ↑ Bond, David P.G.; Wignall, Paul B. (2014), "Large igneous provinces and mass extinctions: An update", Volcanism, Impacts, and Mass Extinctions: Causes and Effects, Geological Society of America, doi:10.1130/2014.2505(02), ISBN 978-0-8137-2505-5 , retrieved 2022-07-18
- ↑ Wignall, P. (2005-12-01). "The Link between Large Igneous Province Eruptions and Mass Extinctions". Elements. 1 (5): 293–297. doi:10.2113/gselements.1.5.293. ISSN 1811-5209.
- ↑ Hallam, Anthony; Wignall, Paul B. (1997). Mass Extinctions and Their Aftermath. Oxford University Press. ISBN 978-0198549161.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ↑ Wignall, Paul B. (2019). Extinction: A Very Short Introduction. Oxford University Press. pp. 1–144. ISBN 978-0198807285.
- ↑ "BBC - Science & Nature - Horizon - The Day The Earth Nearly Died". www.bbc.co.uk. Retrieved 2022-07-07.
- ↑ "Yorkshire Geological Society: Medals, Honours and Grants" (PDF).
- ↑ "The Geological Society of London - President's Awards". www.geolsoc.org.uk. Retrieved 2022-07-06.
- ↑ "Geology Awards - The Clough Medal and Clough Memorial Award Winners". Edinburgh Geological Society. Retrieved 2022-07-06.
- ↑ "Past Science Awards Winners". sepm.org. Retrieved 2022-07-07.
- ↑ "Yorkshire Geological Society: Past Presidents" (PDF).
