Editing Permian–Triassic extinction event (section)

==== Possible impact sites ====
Possible impact craters proposed as the site of an impact causing the P–Tr extinction include the {{convert|250|km|mi|abbr=on}} [[Bedout]] structure off the northwest coast of Australia<ref name="becker_etal_2004" /> and the hypothesized {{convert|480|km|mi|abbr=on}} [[Wilkes Land crater]] of East Antarctica.<ref name="vfp06">{{cite journal |last1=Frese |first1=Ralph R. B. von |author-link1=Ralph von Frese |last2=Potts |first2=Laramie V. |author-link2=Laramie Potts |last3=Wells |first3=Stuart B. |last4=Gaya-Piqué |first4=Luis-Ricardo |last5=Golynsky |first5=Alexander V. |last6=Hernandez |first6=Orlando |last7=Kim |first7=Jeong Woo |last8=Kim |first8=Hyung Rae |last9=Hwang |first9=Jong Sun |title=Permian–Triassic mascon in Antarctica |journal=American Geophysical Union, Fall Meeting 2007 |date=2006 |volume=2007 |pages=Abstract T41A–08 |bibcode=2006AGUSM.T41A..08V |url=https://www.researchgate.net/publication/241531088 }}</ref><ref name="vf09">{{cite journal |last1=Frese |first1=Ralph R. B. von |author-link1=Ralph von Frese |last2=Potts |first2=Laramie V. |author-link2=Laramie Potts |last3=Wells |first3=Stuart B. |last4=Leftwich |first4=Timothy E. |last5=Kim |first5=Hyung Rae |last6=Kim |first6=Jeong Woo |last7=Golynsky |first7=Alexander V. |last8=Hernandez |first8=Orlando |last9=Gaya-Piqué |first9=Luis-Ricardo |title=GRACE gravity evidence for an impact basin in Wilkes Land, Antarctica |journal=[[Geochemistry, Geophysics, Geosystems]] |volume=10 |number=2 |date=25 February 2009 |doi=10.1029/2008GC002149 |bibcode=2009GGG....10.2014V |issn=1525-2027 |url=https://www.researchgate.net/publication/241531088 |doi-access=free }}</ref> An impact has not been proved in either case, and the idea has been widely criticized. The Wilkes Land geophysical feature is of very uncertain age, possibly later than the Permian–Triassic extinction.

Another impact hypothesis postulates that the impact event that formed the [[Araguainha crater]], whose formation has been dated to {{nowrap|254.7 ± 2.5 million}}, a possible temporal range overlapping with the end-Permian extinction,<ref name="Tohver2012">{{cite journal |title=Geochronological constraints on the age of a Permo–Triassic impact event: U–Pb and {{sup|40}}Ar ''/'' {{sup|39}}Ar results for the 40&nbsp;km Araguainha structure of central Brazil |author1=Tohver, Eric |author2=Lana, Cris |author3=Cawood, P.A. |author4=Fletcher, I.R. |author5=Jourdan, F. |author6=Sherlock, S. |author7=Rasmussen, B. |author8=Trindade, R.I.F. |author9=Yokoyama, E. |author10=Souza Filho, C.R. |author11=Marangoni, Y. |display-authors=6 |journal=[[Geochimica et Cosmochimica Acta]] |volume=86 |date=1 June 2012 |pages=214–227 |doi=10.1016/j.gca.2012.03.005 |bibcode=2012GeCoA..86..214T}}</ref> precipitated the mass extinction.<ref name="UWAPressRelease">{{cite press release |title=Biggest extinction in history caused by climate-changing meteor |publisher=University of Western Australia |newspaper=University News |date=31 July 2013 |url=http://www.news.uwa.edu.au/201307315921/international/biggest-extinction-history-caused-climate-changing-meteor}}</ref> The impact occurred around extensive deposits of oil shale in the shallow marine Paraná–Karoo Basin, whose perturbation by the seismicity resulting from impact likely discharged about 1.6 teratonnes of methane into Earth's atmosphere, buttressing the already rapid warming caused by hydrocarbon release due to the Siberian Traps.<ref name="Tohver2013">{{cite journal |last1=Tohver |first1=Eric |last2=Cawood |first2=P. A. |last3=Riccomini |first3=Claudio |last4=Lana |first4=Cris |last5=Trindade |first5=R. I. F. |date=1 October 2013 |title=Shaking a methane fizz: Seismicity from the Araguainha impact event and the Permian–Triassic global carbon isotope record |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018213003313 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=387 |pages=66–75 |doi=10.1016/j.palaeo.2013.07.010 |bibcode=2013PPP...387...66T |access-date=2024-03-26}}</ref> The large earthquakes generated by the impact would have additionally generated massive tsunamis across much of the globe.<ref name="UWAPressRelease" /><ref name="Tohver2018">{{cite journal |last1=Tohver |first1=Eric |last2=Schmieder |first2=Martin |last3=Lana |first3=Cris |last4=Mendes |first4=Pedro S. T. |last5=Jourdan |first5=Fred |last6=Warren |first6=Lucas |last7=Riccomini |first7=Claudio |date=2 January 2018 |title=End-Permian impactogenic earthquake and tsunami deposits in the intracratonic Paraná Basin of Brazil |url=https://pubs.geoscienceworld.org/gsa/gsabulletin/article/130/7-8/1099/525698/End-Permian-impactogenic-earthquake-and-tsunami |journal=[[Geological Society of America Bulletin]] |volume=130 |issue=7–8 |pages=1099–1120 |doi=10.1130/B31626.1 |bibcode=2018GSAB..130.1099T |access-date=2024-03-26|url-access=subscription }}</ref> Despite this, most palaeontologists reject the impact as being a significant driver of the extinction, citing the relatively low energy (equivalent to 10<sup>5</sup> to 10<sup>6</sup> of TNT, around two orders of magnitude lower than the impact energy believed to be required to induce mass extinctions) released by the impact.<ref name="Tohver2013" />

A 2017 paper noted the discovery of a circular gravity anomaly near the [[Falkland Islands]] that might correspond to an impact crater with a diameter of {{convert|250|km|mi|abbr=on}},<ref name="rocca">{{cite journal |author1=Rocca, M. |author2=Rampino, M. |author3=Baez Presser, J. |year=2017 |title=Geophysical evidence for a la impact structure on the Falkland (Malvinas) Plateau|journal=[[Terra Nova (journal)|Terra Nova]] |volume=29 |issue=4 |pages=233–237 |bibcode=2017TeNov..29..233R |doi=10.1111/ter.12269 |s2cid=134484465 }}</ref> as supported by seismic and magnetic evidence. Estimates for the age of the structure range up to 250&nbsp;million years old. This would be substantially larger than the well-known {{convert|180|km|mi|abbr=on}} [[Chicxulub crater|Chicxulub impact crater]] associated with a later extinction. However, Dave McCarthy and colleagues from the British Geological Survey illustrated that the gravity anomaly is not circular and also that the seismic data presented by Rocca, Rampino and Baez Presser did not cross the proposed crater or provide any evidence for an impact crater.<ref>{{Cite journal |last1=McCarthy |first1=Dave |last2=Aldiss |first2=Don |last3=Arsenikos |first3=Stavros |last4=Stone |first4=Phil |last5=Richards |first5=Phil |date=24 August 2017 |title=Comment on "Geophysical evidence for a large impact structure on the Falkland (Malvinas) Plateau" |journal=[[Terra Nova (journal)|Terra Nova]] |language=en |volume=29 |issue=6 |pages=411–415 |doi=10.1111/ter.12285 |issn=0954-4879 |bibcode=2017TeNov..29..411M |s2cid=133781924 |url=http://nora.nerc.ac.uk/id/eprint/525290/1/McCarthy%20et%20al%20Terra_Nova%202017.pdf |access-date=26 March 2023}}</ref>