Editing Triassic–Jurassic extinction event (section)

==== Anoxia and euxinia ====
Anoxia was another mechanism of extinction; the end-Triassic extinction was coeval with an uptick in black shale deposition and a pronounced negative δ<sup>238</sup>U excursion, indicating a major decrease in marine oxygen availability.<ref name="JostEtAl2017" /> Additional evidence for anoxia during the TJME comes from pyrite framboids, which grow in anoxic conditions.<ref>{{Cite journal |last=Hu |first=Fangzhi |last2=Fu |first2=Xiugen |last3=Wang |first3=Jian |last4=Wei |first4=Hengye |last5=Nie |first5=Ying |last6=Zhang |first6=Jian |last7=Tian |first7=Kangzhi |date=2 October 2023 |title=Biological extinction and photic-zone anoxia across the Triassic–Jurassic transition: insights from the Qiangtang Basin, eastern Tethys |url=https://www.lyellcollection.org/doi/10.1144/jgs2022-108 |journal=[[Journal of the Geological Society]] |language=en |volume=180 |issue=5 |doi=10.1144/jgs2022-108 |issn=0016-7649 |access-date=19 February 2025 |via=Lyell Collection Geological Society Publications}}</ref> Evidence of anoxia has been discovered at the Triassic-Jurassic boundary across the world's oceans; the western Tethys, eastern Tethys, and Panthalassa were all affected by a precipitous drop in seawater oxygen,<ref>{{cite journal |last1=Tang |first1=Wei |last2=Wang |first2=Jian |last3=Wei |first3=Hengye |last4=Fu |first4=Xiugen |last5=Ke |first5=Puyang |date=1 August 2023 |title=Sulfur isotopic evidence for global marine anoxia and low seawater sulfate concentration during the Late Triassic |url=https://www.sciencedirect.com/science/article/abs/pii/S1367912023001207 |journal=[[Journal of Asian Earth Sciences]] |volume=251 |page=105659 |doi=10.1016/j.jseaes.2023.105659 |bibcode=2023JAESc.25105659T |s2cid=258091074 |access-date=28 May 2023}}</ref> although at a few sites, the TJME was associated with fully oxygenated waters.<ref>{{cite journal |last1=Wignall |first1=Paul B. |last2=Bond |first2=David P. G. |last3=Kuwahara |first3=Kiyoko |last4=Kakuwa |first4=Yoshitaka |last5=Newton |first5=Robert J. |last6=Poulton |first6=Simon W. |date=March 2010 |title=An 80 million year oceanic redox history from Permian to Jurassic pelagic sediments of the Mino-Tamba terrane, SW Japan, and the origin of four mass extinctions |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818110000287 |journal=[[Global and Planetary Change]] |volume=71 |issue=1–2 |pages=109–123 |doi=10.1016/j.gloplacha.2010.01.022 |bibcode=2010GPC....71..109W |access-date=7 June 2023}}</ref> Positive [[δ15N|δ<sup>15</sup>N]] excursions have also been interpreted as evidence of anoxia concomitant with increased denitrification in marine sediments in the TJME's aftermath.<ref>{{cite journal |last1=Quan |first1=Tracy M. |last2=Van de Schootbrugge |first2=Bas |last3=Field |first3=M. Paul |last4=Rosenthal |first4=Yair |last5=Falkowski |first5=Paul G. |date=10 May 2008 |title=Nitrogen isotope and trace metal analyses from the Mingolsheim core (Germany): Evidence for redox variations across the Triassic-Jurassic boundary |journal=Global Biogeochemical Cycles |volume=22 |issue=2 |pages=1–14 |bibcode=2008GBioC..22.2014Q |doi=10.1029/2007GB002981 |s2cid=56002825 |doi-access=free }}</ref>

In northeastern Panthalassa, episodes of anoxia were already occurring during the Rhaetian before the TJME, making its marine ecosystems unstable even before the main crisis began.<ref>{{cite journal |last1=Larina |first1=Ekaterina |last2=Bottjer |first2=David P. |last3=Corsetti |first3=Frank A. |last4=Zonneveld |first4=John-Paul |last5=Celestian |first5=Aaron J. |last6=Bailey |first6=Jake V. |date=11 December 2019 |title=Uppermost Triassic phosphorites from Williston Lake, Canada: link to fluctuating euxinic-anoxic conditions in northeastern Panthalassa before the end-Triassic mass extinction |journal=[[Scientific Reports]] |volume=9 |issue=1 |page=18790 |doi=10.1038/s41598-019-55162-2 |pmid=31827166 |pmc=6906467 |bibcode=2019NatSR...918790L }}</ref><ref>{{Cite journal |last1=Clement |first1=Annaka M. |last2=Tackett |first2=Lydia S. |last3=Marolt |first3=Samuel |date=15 March 2024 |title=Biosediment assemblages reveal disrupted silica cycling and redox conditions throughout the Rhaetian Stage: Evidence for a precursor event to the end-Triassic mass extinction |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |language=en |volume=638 |pages=112034 |doi=10.1016/j.palaeo.2024.112034 |doi-access=free }}</ref> This early phase of [[environmental degradation]] in eastern Panthalassa may have been caused by an early phase of CAMP activity.<ref>{{cite journal |last1=Larina |first1=Ekaterina |last2=Bottjer |first2=David P. |last3=Corsetti |first3=Frank A. |last4=Thibodeau |first4=Alyson M. |last5=Berelson |first5=William M. |last6=West |first6=A. Joshua |last7=Yager |first7=Joyce A. |date=15 December 2021 |title=Ecosystem change and carbon cycle perturbation preceded the end-Triassic mass extinction |journal=[[Earth and Planetary Science Letters]] |volume=576 |page=117180 |doi=10.1016/j.epsl.2021.117180 |bibcode=2021E&PSL.57617180L |s2cid=244179806 |doi-access=free }}</ref> Anoxic, reducing conditions were likewise present in western Panthalassa off the coast of what is now Japan for about a million years prior to the TJME.<ref>{{Cite journal |last1=Schoepfer |first1=Shane D. |last2=Shen |first2=Jun |last3=Sano |first3=Hiroyoshi |last4=Algeo |first4=Thomas J. |date=January 2022 |title=Onset of environmental disturbances in the Panthalassic Ocean over one million years prior to the Triassic-Jurassic boundary mass extinction |url=https://linkinghub.elsevier.com/retrieve/pii/S0012825221003718 |journal=[[Earth-Science Reviews]] |language=en |volume=224 |pages=103870 |doi=10.1016/j.earscirev.2021.103870 |bibcode=2022ESRv..22403870S |s2cid=244473296 |access-date=22 November 2023}}</ref> During the TJME, the rapid warming led to the stagnation of ocean circulation in many ocean regions, enabling the development of catastrophic anoxia; in what is now northwestern Europe, shallow seas became salinity stratified, enabling easy development of anoxia.<ref name="OrganicWalledDisasterSpecies">{{cite journal |last1=Van de Schootbrugge |first1=Bas |last2=Tremolada |first2=F. |last3=Rosenthal |first3=Y. |last4=Bailey |first4=T. R. |last5=Feist-Burkhardt |first5=S. |last6=Brinkhuis |first6=Henk |last7=Pross |first7=J. |last8=Kent |first8=D. V. |last9=Falkowski |first9=P. G. |date=9 February 2007 |title=End-Triassic calcification crisis and blooms of organic-walled 'disaster species' |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018206004457 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=244 |issue=1–4 |pages=126–141 |bibcode=2007PPP...244..126V |doi=10.1016/j.palaeo.2006.06.026 |access-date=30 May 2023}}</ref> Another factor contributing to anoxia was the increase in continental weathering driven by intense warming that delivered vast quantities of nutrients to the ocean surface and engendered eutrophication; this uptick in weathering is evidenced by positive δ<sup>56</sup>Fe excursions.<ref>{{Cite journal |last=Wan |first=Ruoqi |last2=Yuan |first2=Chengshuai |last3=Liu |first3=Sheng-Ao |last4=Fang |first4=Linhao |last5=Shen |first5=Jun |last6=Wang |first6=Xiaomei |date=17 October 2024 |title=Intensified continental weathering and reductive surface runoff during the Triassic–Jurassic transition |url=https://pubs.geoscienceworld.org/geology/article/53/1/13/649334/Intensified-continental-weathering-and-reductive |journal=Geology |language=en |volume=53 |issue=1 |pages=13–17 |doi=10.1130/G52551.1 |issn=0091-7613 |access-date=18 February 2025 |via=GeoScienceWorld}}</ref> A combination of negative δ<sup>66</sup>Zn excursions, positive δ<sup>26</sup>Mg excursions, and a lack of significant change in δ<sup>65</sup>Cu provides further evidence of increased chemical weathering resulting from increased temperature and humidity on land at high latitudes.<ref>{{Cite journal |last=Xing |first=Kai-Chen |last2=Wang |first2=Feng |last3=Teng |first3=Fang-Zhen |last4=Xu |first4=Wen-Liang |last5=Li |first5=Ming |last6=Sun |first6=Yue-Wu |last7=Yang |first7=De-Bin |date=5 November 2022 |title=High-latitude climatic response across the Triassic-Jurassic boundary recorded by Mg-Cu-Zn isotopes |url=https://www.sciencedirect.com/science/article/pii/S0009254122003795 |journal=[[Chemical Geology]] |language=en |volume=610 |pages=121085 |doi=10.1016/j.chemgeo.2022.121085 |access-date=19 February 2025 |via=Elsevier Science Direct}}</ref> Increased influx of terrestrial organic matter, in conjunction with reduced salinity, has been directly shown to have enkindled anoxia in the Eiberg Basin.<ref>{{Cite journal |last1=Bonis |first1=N.R. |last2=Ruhl |first2=M. |last3=Kürschner |first3=W.M. |date=15 April 2010 |title=Climate change driven black shale deposition during the end-Triassic in the western Tethys |url=https://linkinghub.elsevier.com/retrieve/pii/S0031018209002326 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |language=en |volume=290 |issue=1–4 |pages=151–159 |doi=10.1016/j.palaeo.2009.06.016 |bibcode=2010PPP...290..151B |access-date=22 November 2023}}</ref> Persistent low δ<sup>238</sup>U ratios indicate prolonged global oxygen depletion continued into the Hettangian,<ref>{{Cite journal |last=Somlyay |first=Anna |last2=Palcsu |first2=László |last3=Kiss |first3=Gabriella Ilona |last4=Clarkson |first4=Matthew O. |last5=Kovács |first5=Emma Blanka |last6=Vallner |first6=Zsolt |last7=Zajzon |first7=Norbert |last8=Pálfy |first8=József |date=15 July 2023 |title=Uranium isotope evidence for extensive seafloor anoxia after the end-Triassic mass extinction |url=https://www.sciencedirect.com/science/article/pii/S0012821X23002030 |journal=[[Earth and Planetary Science Letters]] |language=en |volume=614 |pages=118190 |doi=10.1016/j.epsl.2023.118190 |access-date=18 February 2025 |via=Elsevier Science Direct|hdl=10831/107736 |hdl-access=free }}</ref> with <sup>87</sup>Sr/<sup>86</sup>Sr values showing that high influxes of terrestrial nutrients likely continued to eutrophicate the oceans well after the Triassic-Jurassic boundary.<ref>{{Cite journal |last=Heszler |first=Bernát |last2=Katchinoff |first2=Joachim |last3=Palcsu |first3=László |last4=Horváth |first4=Anikó |last5=Vallner |first5=Zsolt |last6=Kovács |first6=Emma Blanka |last7=Planavsky |first7=Noah J. |last8=Pálfy |first8=József |date=19 March 2024 |title=Marine Strontium Isotope Evolution at the Triassic‐Jurassic Transition Links Transient Changes in Continental Weathering to Volcanism of the Central Atlantic Magmatic Province |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GC011464 |journal=[[Geochemistry, Geophysics, Geosystems]] |language=en |volume=25 |issue=3 |doi=10.1029/2024GC011464 |issn=1525-2027 |access-date=18 February 2025 |via=Wiley Online Library|doi-access=free }}</ref> The persistence of anoxia into the Hettangian age may have helped delay the recovery of marine life in the extinction's aftermath.<ref name="JostEtAl2017">{{cite journal |last1=Jost |first1=Adam B. |last2=Bacham |first2=Aviv |last3=Van de Schootbrugge |first3=Bas |last4=Lau |first4=Kimberly V. |last5=Weaver |first5=Karrie L. |last6=Maher |first6=Kate |last7=Payne |first7=Jonathan L. |date=26 July 2017 |title=Uranium isotope evidence for an expansion of marine anoxia during the end-Triassic extinction |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2017GC006941 |journal=[[Geochemistry, Geophysics, Geosystems]] |volume=18 |issue=8 |pages=3093–3108 |doi=10.1002/2017GC006941 |bibcode=2017GGG....18.3093J |hdl=1874/362214 |s2cid=133679444 |access-date=11 March 2023|hdl-access=free }}</ref><ref>{{Cite journal |last1=Luo |first1=Genming |last2=Richoz |first2=Sylvain |last3=van de Schootbrugge |first3=Bas |last4=Algeo |first4=Thomas J. |last5=Xie |first5=Shucheng |last6=Ono |first6=Shuhei |last7=Summons |first7=Roger E. |date=15 June 2018 |title=Multiple sulfur-isotopic evidence for a shallowly stratified ocean following the Triassic-Jurassic boundary mass extinction |url=https://linkinghub.elsevier.com/retrieve/pii/S0016703718302126 |journal=[[Geochimica et Cosmochimica Acta]] |language=en |volume=231 |pages=73–87 |doi=10.1016/j.gca.2018.04.015 |bibcode=2018GeCoA.231...73L |hdl=1874/366656 |s2cid=134614697 |access-date=22 November 2023|hdl-access=free }}</ref><ref>{{Cite journal |last=Prow-Fleischer |first=Ashley N. |last2=Lu |first2=Zunli |last3=Blättler |first3=Clara L. |last4=He |first4=Tianchen |last5=Singh |first5=Pulkit |last6=Kemeny |first6=Preston Cosslett |last7=Todes |first7=Jordan P. |last8=Pohl |first8=Alexandre |last9=Bhattacharya |first9=Tripti |last10=van de Schootbrugge |first10=Bas |last11=Wignall |first11=Paul B. |last12=Todaro |first12=Simona |last13=Payne |first13=Jonathan L. |date=5 February 2025 |title=Calcium isotopes support spatial redox gradients on the Tethys European margin across the Triassic-Jurassic boundary |url=https://www.sciencedirect.com/science/article/abs/pii/S0009254124006107 |journal=[[Chemical Geology]] |language=en |volume=673 |pages=122530 |doi=10.1016/j.chemgeo.2024.122530 |access-date=18 February 2025 |via=Elsevier Science Direct}}</ref>

[[Euxinia]], a form of anoxia defined by not just the absence of dissolved oxygen but high concentrations of [[hydrogen sulphide]], also developed in the oceans, as indicated by findings of increased isorenieratane. The increase in concentration of this substance reveals that populations of [[green sulfur bacteria|green sulphur bacteria]], which photosynthesise using [[hydrogen sulphide]] instead of water, grew significantly across the Triassic-Jurassic boundary.<ref name="RichozEtAl2012">{{cite journal |last1=Richoz |first1=Sylvain |last2=Van de Schootbrugge |first2=Bas |last3=Pross |first3=Jörg |last4=Püttmann |first4=Wilhelm |last5=Quan |first5=Tracy M. |last6=Lindström |first6=Sofie |last7=Heunisch |first7=Carmen |last8=Fiebig |first8=Jens |last9=Maquil |first9=Robert |last10=Schouten |first10=Stefan |last11=Hauzenberger |first11=Christoph A. |last12=Wignall |first12=Paul B. |date=12 August 2012 |title=Hydrogen sulphide poisoning of shallow seas following the end-Triassic extinction |url=https://www.nature.com/articles/ngeo1539 |journal=[[Nature Geoscience]] |volume=5 |issue=1 |pages=662–667 |bibcode=2012NatGe...5..662R |doi=10.1038/ngeo1539 |s2cid=128759882 |access-date=22 May 2023}}</ref><ref>{{cite journal |last1=Jaraula |first1=Caroline M. B. |last2=Grice |first2=Kliti |last3=Twitchett |first3=Richard J. |last4=Böttcher |first4=Michael E. |last5=LeMetayer |first5=Pierre |last6=Dastidar |first6=Apratim G. |last7=Opazo |first7=L. Felipe |date=1 September 2013 |title=Elevated pCO2 leading to Late Triassic extinction, persistent photic zone euxinia, and rising sea levels |url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/41/9/955/131334/Elevated-pCO2-leading-to-Late-Triassic-extinction |journal=[[Geology (journal)|Geology]] |volume=41 |issue=9 |pages=955–958 |bibcode=2013Geo....41..955J |doi=10.1130/G34183.1 |access-date=30 May 2023}}</ref> A meteoric shift towards positive sulphur isotope ratios in reduced sulphur species indicates a complete utilisation of sulphate by sulphate reducing bacteria.<ref>{{cite journal |last1=Williford |first1=Kenneth H. |last2=Foriel |first2=Juliet |last3=Ward |first3=Peter D. |last4=Steig |first4=Eric J. |date=1 September 2009 |title=Major perturbation in sulfur cycling at the Triassic-Jurassic boundary |url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/37/9/835/30031/Major-perturbation-in-sulfur-cycling-at-the |journal=[[Geology (journal)|Geology]] |volume=37 |issue=9 |pages=835–838 |bibcode=2009Geo....37..835W |doi=10.1130/G30054A.1 |access-date=7 June 2023}}</ref> Off the shores of the Wrangellia Terrane, the onset of photic zone euxinia was preceded by an interval of limited nitrogen availability and increased nitrogen fixation in surface waters while euxinia developed in bottom waters.<ref>{{Cite journal |last1=Schoepfer |first1=Shane D. |last2=Algeo |first2=Thomas J. |last3=Ward |first3=Peter Douglas |last4=Williford |first4=Kenneth H. |last5=Haggart |first5=James W. |date=1 October 2016 |title=Testing the limits in a greenhouse ocean: Did low nitrogen availability limit marine productivity during the end-Triassic mass extinction? |journal=[[Earth and Planetary Science Letters]] |volume=451 |pages=138–148 |bibcode=2016E&PSL.451..138S |doi=10.1016/j.epsl.2016.06.050 |issn=0012-821X |doi-access=free}}</ref> Recurrent hydrogen sulphide poisoning following the TJME had retarding effects on biotic rediversification.<ref>{{cite journal |last1=Beith |first1=Sarah J. |last2=Fox |first2=Calum P. |last3=Marshall |first3=John E. A. |last4=Whiteside |first4=Jessica H. |date=15 December 2021 |title=Recurring photic zone euxinia in the northwest Tethys impinged end-Triassic extinction recovery |url=https://www.sciencedirect.com/science/article/abs/pii/S003101822100465X |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=584 |page=110680 |doi=10.1016/j.palaeo.2021.110680 |bibcode=2021PPP...58410680B |s2cid=244263152 |access-date=28 May 2023}}</ref><ref name="RichozEtAl2012" />