Toarcian Oceanic Anoxic Event

{{Short description|Anoxic event in the Jurassic period}}

The '''Toarcian extinction event''', also called the '''Pliensbachian-Toarcian extinction event''',<ref name="MassOriginationVersusMassExtinction" /><ref name="PliensbachianToarcianExtinction" /> the '''Early Toarcian mass extinction''',<ref name="EarlyToarcianMassExtinction" /> the '''Early Toarcian palaeoenvironmental crisis''',<ref name="SuanEtAl2008" /> or the '''Jenkyns Event''',<ref name="KempEtAl2022EarthScienceReviews">{{cite journal |last1=Kemp |first1=David B. |last2=Suan |first2=Guillaume |last3=Fantasia |first3=Alicia |last4=Jin |first4=Simin |last5=Chen |first5=Wenhan |date=August 2022 |title=Global organic carbon burial during the Toarcian oceanic anoxic event: Patterns and controls |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825222001702 |journal=Earth-Science Reviews |volume=231 |article-number=104086 |doi=10.1016/j.earscirev.2022.104086 |bibcode=2022ESRv..23104086K |s2cid=249693286 |access-date=3 January 2023|url-access=subscription }}</ref><ref name=":36">{{Cite journal |last1=Reolid |first1=Matías |last2=Mattioli |first2=Emanuela |last3=Duarte |first3=Luís V. |last4=Ruebsam |first4=Wolfgang |date=2021-09-22 |title=The Toarcian Oceanic Anoxic Event: where do we stand? |url=https://sp.lyellcollection.org/content/early/2021/09/21/SP514-2021-74 |journal=Geological Society, London, Special Publications |language=en |volume=514 |issue=1 |pages=1–11 |bibcode=2021GSLSP.514....1R |doi=10.1144/SP514-2021-74 |issn=0305-8719 |s2cid=238683028|url-access=subscription }}</ref><ref>{{Cite journal |last1=Reolid |first1=Matias |last2=Mattioli |first2=Emanuela |last3=Duarte |first3=Luis V. |last4=Marok |first4=Abbas |date=1 June 2020 |title=The Toarcian Oceanic Anoxic Event and the Jenkyns Event (IGCP-655 final report) |journal=Episodes |language=en |volume=43 |issue=2 |pages=833–844 |doi=10.18814/epiiugs/2020/020051 |s2cid=216195656 |issn=0705-3797 |doi-access=free |bibcode=2020Episo..43..833R }}</ref> was an extinction event that occurred during the early part of the Toarcian age, approximately 183 million years ago, during the Early Jurassic. The extinction event had two main pulses,<ref name="SuanEtAl2008" /> the first being the '''Pliensbachian-Toarcian boundary event''' ('''PTo-E''').<ref name="KrenckerEtAl2014" /> The second, larger pulse, the '''Toarcian Oceanic Anoxic Event''' ('''TOAE'''), was a global oceanic anoxic event,<ref name="KempEtAl2022GPC" /> representing possibly the most extreme case of widespread ocean deoxygenation in the entire Phanerozoic eon.<ref name="BelemniteEcology">{{cite journal |last1=Ullmann |first1=Clemens Vinzenz |last2=Thibault |first2=Nicolas |last3=Ruhl |first3=Micha |last4=Hesselbo |first4=Stephen P. |last5=Korte |first5=Christoph |date=30 June 2014 |title=Effect of a Jurassic oceanic anoxic event on belemnite ecology and evolution |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=111 |issue=28 |pages=10073–10076 |doi=10.1073/pnas.1320156111 |pmid=24982187 |pmc=4104856 |doi-access=free }}</ref> In addition to the PTo-E and TOAE, there were multiple other, smaller extinction pulses within this span of time.<ref name="KrenckerEtAl2014" />

Occurring during the supergreenhouse climate of the Early Toarcian Thermal Maximum (ETTM),<ref name="ChristopherScotese">{{Cite journal |last1=Scotese |first1=Christopher R. |last2=Song |first2=Haijun |last3=Mills |first3=Benjamin J.W. |last4=van der Meer |first4=Douwe G. |date=April 2021 |title=Phanerozoic paleotemperatures: The earth's changing climate during the last 540 million years |url=https://www.researchgate.net/publication/348351275 |journal=Earth-Science Reviews |volume=215 |article-number=103503 |bibcode=2021ESRv..21503503S |doi=10.1016/j.earscirev.2021.103503 |issn=0012-8252 |archive-url=https://web.archive.org/web/20210108000000/http://dx.doi.org/10.1016/j.earscirev.2021.103503 |archive-date=8 January 2021 |s2cid=233579194 |access-date=17 July 2023}} [https://eprints.whiterose.ac.uk/169823/ Alt URL]</ref> the Early Toarcian extinction was associated with large igneous province volcanism,<ref name="SynchronyEarlyJurassicExtinctionOAE" /> which elevated global temperatures,<ref name="ChristopherScotese" /> acidified the oceans,<ref name="BoronEvidenceOfOceanAcid" /> and prompted the development of anoxia,<ref name="XiaMansour2022" /> leading to severe biodiversity loss.<ref name="JenkynsDinosaurs" /> The biogeochemical crisis is documented by a high amplitude negative carbon isotope excursions,<ref name="ThemEtAl">{{Cite journal |last1=Them |first1=T.R. |last2=Gill |first2=B.C. |last3=Caruthers |first3=A.H. |last4=Gröcke |first4=D.R. |last5=Tulsky |first5=E.T. |last6=Martindale |first6=R.C. |last7=Poulton |first7=T.P. |last8=Smith |first8=P.L. |date=February 2017 |title=High-resolution carbon isotope records of the Toarcian Oceanic Anoxic Event (Early Jurassic) from North America and implications for the global drivers of the Toarcian carbon cycle |journal=Earth and Planetary Science Letters |language=en |volume=459 |pages=118–126 |bibcode=2017E&PSL.459..118T |doi=10.1016/j.epsl.2016.11.021 |doi-access=free}}</ref><ref>{{cite journal |last1=Ros-Franch |first1=Sonia |last2=Echevarría |first2=Javier |last3=Damborenea |first3=Susana E. |last4=Manceñido |first4=Miguel O. |last5=Jenkyns |first5=Hugh C. |last6=Al-Suwaidi |first6=Aisha |last7=Hesselbo |first7=Stephen P. |last8=Riccardi |first8=Alberto C. |date=1 July 2019 |title=Population response during an Oceanic Anoxic Event: The case of Posidonotis (Bivalvia) from the Lower Jurassic of the Neuquén Basin, Argentina |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018219301415 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=525 |pages=57–67 |bibcode=2019PPP...525...57R |doi=10.1016/j.palaeo.2019.04.009 |access-date=23 November 2022 |hdl=11336/128130 |s2cid=146525666|hdl-access=free }}</ref> as well as black shale deposition.<ref name="BeaujolaisBlackShales" />

== Timing == The Early Toarcian extinction event occurred in two distinct pulses,<ref name="SuanEtAl2008">{{cite journal |last1=Suan |first1=Guillaume |last2=Mattioli |first2=Emanuela |last3=Pittet |first3=Bernard |last4=Mailliot |first4=Samuel |last5=Lécuyer |first5=Christophe |date=17 January 2008 |title=Evidence for major environmental perturbation prior to and during the Toarcian (Early Jurassic) oceanic anoxic event from the Lusitanian Basin, Portugal |journal=Paleoceanography and Paleoclimatology |volume=23 |issue=1 |pages=1–14 |article-number=2007PA001459 |doi=10.1029/2007PA001459 |bibcode=2008PalOc..23.1202S |s2cid=129137256 |doi-access=free }}</ref> with the first event being classified by some authors as its own event unrelated to the more extreme second event.<ref>{{cite journal |last1=Cecca |first1=Fabrizio |last2=Macchioni |first2=Francesco |date=2 January 2007 |title=The two Early Toarcian (Early Jurassic) extinction events in ammonoids |url=https://onlinelibrary.wiley.com/doi/abs/10.1080/00241160310008257 |journal=Lethaia |volume=37 |issue=1 |pages=35–56 |doi=10.1080/00241160310008257 |access-date=14 June 2023|url-access=subscription }}</ref> The first, more recently identified pulse occurred during the ''mirabile'' subzone of the ''tenuicostatum'' ammonite zone, coinciding with a slight drop in oxygen concentrations and the beginning of warming following a late Pliensbachian cool period.<ref name="Arias2013" /> This first pulse, occurring near the Pliensbachian-Toarcian boundary,<ref>{{cite journal |last1=Littler |first1=Kate |last2=Hesselbo |first2=Stephen P. |last3=Jenkyns |first3=Hugh C. |date=5 October 2009 |title=A carbon-isotope perturbation at the Pliensbachian–Toarcian boundary: evidence from the Lias Group, NE England |url=https://www.cambridge.org/core/journals/geological-magazine/article/abs/carbonisotope-perturbation-at-the-pliensbachiantoarcian-boundary-evidence-from-the-lias-group-ne-england/FC4BF10D9141FC91B7480399942A6EED |journal=Geological Magazine |volume=147 |issue=2 |pages=181–192 |doi=10.1017/S0016756809990458 |s2cid=129648354 |access-date=5 August 2023|url-access=subscription }}</ref> is referred to as the PTo-E.<ref name="KrenckerEtAl2014">{{cite journal |last1=Krencker |first1=F. N. |last2=Bodin |first2=S. |last3=Hoffmann |first3=R. |last4=Suan |first4=Guillaume |last5=Mattioli |first5=E. |last6=Kabiri |first6=L. |last7=Föllmi |first7=K. B. |last8=Immenhauser |first8=A. |date=June 2014 |title=The middle Toarcian cold snap: Trigger of mass extinction and carbonate factory demise |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818114000629 |journal=Global and Planetary Change |volume=117 |pages=64–78 |doi=10.1016/j.gloplacha.2014.03.008 |bibcode=2014GPC...117...64K |access-date=20 January 2023|url-access=subscription }}</ref><ref name="KempEtAl2022GPC">{{cite journal |last1=Kemp |first1=David B. |last2=Chen |first2=Wenhan |last3=Cho |first3=Tenichi |last4=Algeo |first4=Thomas J. |last5=Shen |first5=Jun |last6=Ikeda |first6=Masayuki |date=May 2022 |title=Deep-ocean anoxia across the Pliensbachian-Toarcian boundary and the Toarcian Oceanic Anoxic Event in the Panthalassic Ocean |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818122000492 |journal=Global and Planetary Change |volume=212 |article-number=103782 |doi=10.1016/j.gloplacha.2022.103782 |bibcode=2022GPC...21203782K |s2cid=247424412 |access-date=1 January 2023|url-access=subscription }}</ref> The TOAE itself occurred near the ''tenuicostatum''–''serpentinum'' ammonite biozonal boundary,<ref>{{cite journal |last1=Al-Suwaidi |first1=Aisha H. |last2=Ruhl |first2=Micha |last3=Jenkyns |first3=Hugh C. |last4=Damborenea |first4=Susana E. |last5=Manceñido |first5=Miguel O. |last6=Condon |first6=Daniel J. |last7=Angelozzi |first7=Gladys N. |last8=Kamo |first8=Sandra L. |last9=Storm |first9=Marisa |last10=Riccardi |first10=Alberto C. |last11=Hesselbo |first11=Stephen P. |date=23 March 2022 |title=New age constraints on the Lower Jurassic Pliensbachian–Toarcian Boundary at Chacay Melehue (Neuquén Basin, Argentina) |journal=Scientific Reports |volume=12 |issue=1 |page=4975 |doi=10.1038/s41598-022-07886-x |pmid=35322043 |pmc=8942990 |bibcode=2022NatSR..12.4975A }}</ref> specifically in the ''elegantulum'' subzone of the ''serpentinum'' ammonite zone, during a marked, pronounced warming interval.<ref name="Arias2013" /> The TOAE lasted for approximately 500,000 years,<ref>{{Cite journal |last1=Boulila |first1=Slah |last2=Galbrun |first2=Bruno |last3=Sadki |first3=Driss |last4=Gardin |first4=Silvia |last5=Bartolini |first5=Annachiara |date=1 April 2019 |title=Constraints on the duration of the early Toarcian T-OAE and evidence for carbon-reservoir change from the High Atlas (Morocco) |url=https://www.sciencedirect.com/science/article/pii/S092181811830403X |journal=Global and Planetary Change |volume=175 |pages=113–128 |doi=10.1016/j.gloplacha.2019.02.005 |bibcode=2019GPC...175..113B |s2cid=134411583 |issn=0921-8181 |access-date=26 November 2023}}</ref><ref name="BaileyEtAl2003GenesisOAE">{{cite journal |last1=Bailey |first1=T. M. |last2=Rosenthal |first2=Y. |last3=McArthur |first3=J. M. |last4=Van de Schootbrugge |first4=B. |last5=Thirlwall |first5=M. F. |date=25 July 2003 |title=Paleoceanographic changes of the Late Pliensbachian–Early Toarcian interval: a possible link to the genesis of an Oceanic Anoxic Event |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X03002784 |journal=Earth and Planetary Science Letters |volume=212 |issue=3–4 |pages=307–320 |bibcode=2003E&PSL.212..307B |doi=10.1016/S0012-821X(03)00278-4 |access-date=7 January 2023|url-access=subscription }}</ref><ref>{{cite journal |last1=McArthur |first1=J. M. |last2=Donovan |first2=D. T. |last3=Thirlwall |first3=M. F. |last4=Fouke |first4=B. W. |last5=Mattey |first5=D. |date=30 June 2000 |title=Strontium isotope profile of the early Toarcian (Jurassic) oceanic anoxic event, the duration of ammonite biozones, and belemnite palaeotemperatures |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X00001114 |journal=Earth and Planetary Science Letters |volume=179 |issue=2 |pages=269–285 |doi=10.1016/S0012-821X(00)00111-4 |bibcode=2000E&PSL.179..269M |access-date=5 August 2023|url-access=subscription }}</ref> though a range of estimates from 200,000 to 1,000,000 years have also been given.<ref name="SabatinoEtAl2009">{{cite journal |last1=Sabatino |first1=Nadia |last2=Neri |first2=Rodolfo |last3=Bellanca |first3=Adriana |last4=Jenkyns |first4=Hugh C. |last5=Baudin |first5=François |last6=Parisi |first6=Guido |last7=Masetti |first7=Daniele |date=13 July 2009 |title=Carbon-isotope records of the Early Jurassic (Toarcian) oceanic anoxic event from the Valdorbia (Umbria–Marche Apennines) and Monte Mangart (Julian Alps) sections: palaeoceanographic and stratigraphic implications |url=https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-3091.2008.01035.x |journal=Sedimentology |volume=56 |issue=5 |pages=1307–1328 |bibcode=2009Sedim..56.1307S |doi=10.1111/j.1365-3091.2008.01035.x |s2cid=140543701 |access-date=8 April 2023|url-access=subscription }}</ref> The PTo-E primarily affected shallow water biota, while the TOAE was the more severe event for organisms living in deep water.<ref name="CarbonateFactoryCollapse" />

== Causes == Geological, isotopic, and palaeobotanical evidence suggests the late Pliensbachian was an icehouse period.<ref>{{cite journal |last1=Ruebsam |first1=Wolfgang |last2=Reolid |first2=Matias |last3=Sabatino |first3=Nadia |last4=Masetti |first4=Daniele |last5=Schwark |first5=Lorenz |date=December 2020 |title=Molecular paleothermometry of the early Toarcian climate perturbation |journal=Global and Planetary Change |volume=195 |article-number=103351 |doi=10.1016/j.gloplacha.2020.103351 |bibcode=2020GPC...19503351R |s2cid=225109000 |doi-access=free }}</ref><ref>{{cite journal |last1=Ruebsam |first1=Wolfgang |last2=Al-Husseini |first2=Moujahed |date=1 September 2021 |title=Orbitally synchronized late Pliensbachian–early Toarcian glacio-eustatic and carbon-isotope cycles |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=577 |article-number=110562 |doi=10.1016/j.palaeo.2021.110562 |bibcode=2021PPP...57710562R |doi-access=free }}</ref><ref>{{cite journal |last1=Merkel |first1=Anna |last2=Munnecke |first2=Axel |date=18 May 2023 |title=Glendonite-bearing concretions from the upper Pliensbachian (Lower Jurassic) of South Germany: indicators for a massive cooling in the European epicontinental sea |journal=Facies |volume=69 |issue=3 |page=10 |doi=10.1007/s10347-023-00667-6 |doi-access=free |bibcode=2023Faci...69...10M }}</ref> These ice sheets are believed to have been thin and stretched into lower latitudes, making them extremely sensitive to temperature changes.<ref>{{cite journal |last1=Nordt |first1=Lee |last2=Breecker |first2=Daniel |last3=White |first3=Joseph |date=30 December 2021 |title=Jurassic greenhouse ice-sheet fluctuations sensitive to atmospheric CO2 dynamics |url=https://www.nature.com/articles/s41561-021-00858-2#citeas |journal=Nature Geoscience |volume=15 |issue=1 |pages=54–59 |doi=10.1038/s41561-021-00858-2 |s2cid=245569085 |access-date=16 August 2023|url-access=subscription }}</ref> A warming trend lasting from the latest Pliensbachian to the earliest Toarcian was interrupted by a "cold snap" in the middle ''polymorphum'' zone, equivalent to the ''tenuicostatum'' ammonite zone, which was then followed by the abrupt warming interval associated with the TOAE.<ref>{{cite journal |last1=Suan |first1=Guillaume |last2=Mattioli |first2=Emanuela |last3=Pittet |first3=Bernard |last4=Lécuyer |first4=Christophe |last5=Suchéras-Marx |first5=Baptiste |last6=Duarte |first6=Luís Vítor |last7=Philippe |first7=Marc |last8=Reggiani |first8=Letizia |last9=Martineau |first9=François |date=20 February 2010 |title=Secular environmental precursors to Early Toarcian (Jurassic) extreme climate changes |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X10000117 |journal=Earth and Planetary Science Letters |volume=290 |issue=3–4 |pages=448–458 |doi=10.1016/j.epsl.2009.12.047 |bibcode=2010E&PSL.290..448S |hdl=10316/20069 |access-date=19 August 2022|hdl-access=free }}</ref> This global warming, driven by rising atmospheric carbon dioxide, was the mainspring of the early Toarcian environmental crisis.<ref name="EarlyToarcianMassExtinction">{{cite journal |last1=Gómez |first1=Juan J. |last2=Comas-Rengifo |first2=María J. |last3=Goy |first3=Antonio |date=20 May 2016 |title=Palaeoclimatic oscillations in the Pliensbachian (Early Jurassic) of the Asturian Basin (Northern Spain) |url=https://cp.copernicus.org/articles/12/1199/2016/ |journal=Climate of the Past |volume=12 |issue=5 |pages=1199–1214 |doi=10.5194/cp-12-1199-2016 |bibcode=2016CliPa..12.1199G |access-date=14 May 2023|doi-access=free |hdl=10261/133460 |hdl-access=free }}</ref> Carbon dioxide levels rose from about 500 ppm to about 1,000 ppm.<ref>{{cite journal |last1=Ruebsam |first1=Wolfgang |last2=Reolid |first2=Matías |last3=Schwark |first3=Lorenz |date=10 January 2020 |title=δ13C of terrestrial vegetation records Toarcian CO2 and climate gradients |journal=Scientific Reports |volume=10 |issue=1 |page=117 |doi=10.1038/s41598-019-56710-6 |pmid=31924807 |pmc=6954244 |bibcode=2020NatSR..10..117R }}</ref> Seawater warmed by anywhere between 3&nbsp;°C and 7&nbsp;°C, depending on latitude.<ref>{{cite journal |last1=Piazza |first1=Veronica |last2=Ullmann |first2=Clemens Vinzenz |last3=Aberhan |first3=Martin |date=9 December 2020 |title=Ocean warming affected faunal dynamics of benthic invertebrate assemblages across the Toarcian Oceanic Anoxic Event in the Iberian Basin (Spain) |journal=PLOS ONE |volume=15 |issue=12 |article-number=e0242331 |doi=10.1371/journal.pone.0242331 |pmid=33296368 |pmc=7725388 |bibcode=2020PLoSO..1542331P |doi-access=free }}</ref> At the height of this supergreenhouse interval, global sea surface temperatures (SSTs) averaged about 21 °C.<ref name="EarlyToarcianMassExtinction" />

The eruption of the Karoo-Ferrar Large Igneous Province is generally attributed to have caused the surge in atmospheric carbon dioxide levels.<ref name="SynchronyEarlyJurassicExtinctionOAE">{{cite journal |last1=Pálfy |first1=József |last2=Smith |first2=Paul L. |date=1 August 2000 |title=Synchrony between Early Jurassic extinction, oceanic anoxic event, and the Karoo-Ferrar flood basalt volcanism |url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/28/8/747/191908/Synchrony-between-Early-Jurassic-extinction |journal=Geology |volume=28 |issue=8 |pages=747–750 |doi=10.1130/0091-7613(2000)28<747:SBEJEO>2.0.CO;2 |bibcode=2000Geo....28..747P |access-date=17 April 2023|url-access=subscription }}</ref><ref name=":36" /><ref>{{cite journal |last1=Font |first1=Eric |last2=Duarte |first2=Luís Vítor |last3=Dekkers |first3=Mark J. |last4=Remazeilles |first4=Celine |last5=Egli |first5=Ramon |last6=Spangenberg |first6=Jorge E. |last7=Fantasia |first7=Alicia |last8=Ribeiro |first8=Joana |last9=Gomes |first9=Elsa |last10=Mirão |first10=José |last11=Adatte |first11=Thierry |date=14 March 2022 |title=Rapid light carbon releases and increased aridity linked to Karoo-Ferrar magmatism during the early Toarcian oceanic anoxic event |journal=Scientific Reports |volume=12 |issue=1 |page=4342 |doi=10.1038/s41598-022-08269-y |pmid=35288615 |pmc=8921222 |bibcode=2022NatSR..12.4342F }}</ref> Argon-argon dating of Karoo-Ferrar rhyolites points to a link between Karoo-Ferrar volcanism and the extinction event,<ref>{{cite journal |last1=Riley |first1=T. R. |last2=Millar |first2=I. L. |last3=Watkeys |first3=M. K. |last4=Curtis |first4=M. L. |last5=Leat |first5=P. T. |last6=Klausen |first6=M. B. |last7=Fanning |first7=C. M. |date=1 July 2004 |title=U–Pb zircon (SHRIMP) ages for the Lebombo rhyolites, South Africa: refining the duration of Karoo volcanism |url=https://pubs.geoscienceworld.org/jgs/article-abstract/161/4/547/94306/U-Pb-zircon-SHRIMP-ages-for-the-Lebombo-rhyolites?redirectedFrom=fulltext |journal=Journal of the Geological Society |volume=161 |issue=4 |pages=547–550 |doi=10.1144/0016-764903-181 |bibcode=2004JGSoc.161..547R |s2cid=129916780 |access-date=17 April 2023|url-access=subscription }}</ref> a conclusion reinforced by uranium-lead dating<ref>{{cite journal |last1=Svensen |first1=Henrik |last2=Corfu |first2=Fernando |last3=Polteau |first3=Stéphane |last4=Hammer |first4=Øyvind |last5=Planke |first5=Sverre |date=1 April 2012 |title=Rapid magma emplacement in the Karoo Large Igneous Province |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X12000258 |journal=Earth and Planetary Science Letters |volume=325-326 |pages=1–9 |doi=10.1016/j.epsl.2012.01.015 |bibcode=2012E&PSL.325....1S |access-date=14 June 2023|url-access=subscription }}</ref><ref>{{Cite journal |last1=Sell |first1=Bryan |last2=Ovtcharova |first2=Maria |last3=Guex |first3=Jean |last4=Bartolini |first4=Annachiara |last5=Jourdan |first5=Fred |last6=Spangenberg |first6=Jorge E. |last7=Vicente |first7=Jean-Claude |last8=Schaltegger |first8=Urs |date=15 December 2014 |title=Evaluating the temporal link between the Karoo LIP and climatic–biologic events of the Toarcian Stage with high-precision U–Pb geochronology |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X14006293 |journal=Earth and Planetary Science Letters |language=en |volume=408 |pages=48–56 |doi=10.1016/j.epsl.2014.10.008 |bibcode=2014E&PSL.408...48S |access-date=31 January 2025 |via=Elsevier Science Direct|url-access=subscription }}</ref> and palaeomagnetism.<ref>{{Cite journal |last1=Moulin |first1=Maud |last2=Fluteau |first2=Frédéric |last3=Courtillot |first3=Vincent |last4=Marsh |first4=Julian |last5=Delpech |first5=Guillaume |last6=Quidelleur |first6=Xavier |last7=Gérard |first7=Martine |last8=Jay |first8=Anne E. |date=13 July 2011 |title=An attempt to constrain the age, duration, and eruptive history of the Karoo flood basalt: Naude's Nek section (South Africa) |journal=Journal of Geophysical Research |language=en |volume=116 |issue=B7 |pages=1–27 |article-number=B07403 |doi=10.1029/2011JB008210 |issn=0148-0227 |doi-access=free |bibcode=2011JGRB..116.7403M }}</ref> Dating of zircons suggests that the magmatic activity lasted for about 349 ± 49 kyr,<ref>{{cite journal |last1=Burgess |first1=S. D. |last2=Bowring |first2=S. A. |last3=Fleming |first3=T. H. |last4=Elliot |first4=D. H. |date=1 April 2015 |title=High-precision geochronology links the Ferrar large igneous province with early-Jurassic ocean anoxia and biotic crisis |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X15000655 |journal=Earth and Planetary Science Letters |volume=415 |pages=90–99 |bibcode=2015E&PSL.415...90B |doi=10.1016/j.epsl.2015.01.037 |access-date=14 June 2023|url-access=subscription }}</ref> although plagioclase dating suggests a duration of approximately 1.6 Myr.<ref>{{Cite journal |last1=Ware |first1=Bryant |last2=Jourdan |first2=Fred |last3=Timms |first3=Nicholas E. |date=15 November 2023 |title=The Ferrar Continental Flood Basalt: A ∼1.6 Ma long duration evidenced by high-precision 40Ar/39Ar ages suggest a potential role in the Pliensbachian-Toarcian extinction event |journal=Earth and Planetary Science Letters |language=en |volume=622 |article-number=118369 |doi=10.1016/j.epsl.2023.118369 |doi-access=free }}</ref> Occurring during a broader, gradual positive carbon isotope excursion as measured by δ¹³C values, the TOAE is preceded by a global negative δ¹³C excursion recognised in fossil wood, organic carbon, and carbonate carbon in the ''tenuicostatum'' ammonite zone of northwestern Europe,<ref>{{cite journal |last1=Hesselbo |first1=Stephen P. |last2=Jenkyns |first2=Hugh C. |last3=Duarte |first3=Luis V. |last4=Oliveira |first4=Luiz C. V. |date=30 January 2007 |title=Carbon-isotope record of the Early Jurassic (Toarcian) Oceanic Anoxic Event from fossil wood and marine carbonate (Lusitanian Basin, Portugal) |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X06007965 |journal=Earth and Planetary Science Letters |volume=253 |issue=3–4 |pages=455–470 |bibcode=2007E&PSL.253..455H |doi=10.1016/j.epsl.2006.11.009 |access-date=11 January 2023 |hdl-access=free |hdl=10316/3934|url-access=subscription }}</ref> with this negative δ¹³C shift being the result of volcanic discharge of light carbon.<ref name="ThemEtAl" /> The global ubiquity of this negative δ¹³C excursion has been called into question, however, due to its absence in certain deposits from the time, such as the Bächental bituminous marls,<ref>{{cite journal |last1=Neumeister |first1=S. |last2=Gratzer |first2=R. |last3=Algeo |first3=Thomas J. |last4=Bechtel |first4=A. |last5=Gawlick |first5=H.-J. |last6=Newton |first6=Robert J. |last7=Sachsenhofer |first7=R. F. |date=March 2015 |title=Oceanic response to Pliensbachian and Toarcian magmatic events: Implications from an organic-rich basinal succession in the NW Tethys |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818115000235 |journal=Global and Planetary Change |volume=126 |pages=62–83 |bibcode=2015GPC...126...62N |doi=10.1016/j.gloplacha.2015.01.007 |access-date=8 January 2023|url-access=subscription }}</ref> though its occurrence in areas like Greece has been cited as evidence of its global nature.<ref>{{cite journal |last1=Kafousia |first1=N. |last2=Karakitsios |first2=V. |last3=Jenkyns |first3=Hugh C. |last4=Mattioli |first4=E. |date=22 February 2011 |title=A global event with a regional character: the Early Toarcian Oceanic Anoxic Event in the Pindos Ocean (northern Peloponnese, Greece) |url=https://www.cambridge.org/core/journals/geological-magazine/article/abs/global-event-with-a-regional-character-the-early-toarcian-oceanic-anoxic-event-in-the-pindos-ocean-northern-peloponnese-greece/55263029D8279B48E4F3DC926587F0A4 |journal=Geological Magazine |volume=148 |issue=4 |pages=619–631 |bibcode=2011GeoM..148..619K |doi=10.1017/S0016756811000082 |s2cid=30165407 |access-date=13 March 2023}}</ref> The negative δ¹³C shift is also known from the Arabian Peninsula,<ref>{{cite journal |last1=Alnazghah |first1=Mahmoud |last2=Koeshidayatullah |first2=Ardiansyah |last3=Al-Hussaini |first3=Abdulkarim |last4=Amao |first4=Abduljamiu |last5=Song |first5=Haijun |last6=Al-Ramadan |first6=Khalid |date=27 October 2022 |title=Evidence for the early Toarcian Carbon Isotope Excursion (T-CIE) from the shallow marine siliciclastic red beds of Arabia |journal=Scientific Reports |volume=12 |issue=1 |page=18124 |bibcode=2022NatSR..1218124A |doi=10.1038/s41598-022-21716-0 |pmc=9613744 |pmid=36302804}}</ref> the Ordos Basin,<ref name="OrdosBasin" /> and the Neuquén Basin.<ref>{{cite journal |last1=Mazzini |first1=Adriano |last2=Svensen |first2=Henrik |last3=Leanza |first3=Héctor A. |last4=Corfu |first4=Fernando |last5=Planke |first5=Sverre |date=1 September 2010 |title=Early Jurassic shale chemostratigraphy and U–Pb ages from the Neuquén Basin (Argentina): Implications for the Toarcian Oceanic Anoxic Event |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X10004553 |journal=Earth and Planetary Science Letters |volume=297 |issue=3–4 |pages=633–645 |bibcode=2010E&PSL.297..633M |doi=10.1016/j.epsl.2010.07.017 |access-date=14 May 2023 |hdl-access=free |hdl=11336/69031|url-access=subscription }}</ref> The negative δ¹³C excursion has been found to be up to -8% in bulk organic and carbonate carbon, although analysis of compound specific biomarkers suggests a global value of around -3% to -4%. In addition, numerous smaller scale carbon isotope excursions are globally recorded on the falling limb of the larger negative δ¹³C excursion.<ref name="ThemEtAl" /> Although the PTo-E is not associated with a decrease in δ¹³C analogous to the TOAE's, volcanism is nonetheless believed to have been responsible for its onset as well, with the carbon injection most likely having an isotopically heavy, mantle-derived origin.<ref>{{Cite journal |last1=Bodin |first1=Stephane |last2=Krencker |first2=Francois-Nicolas |last3=Kothe |first3=Tim |last4=Hoffmann |first4=Rene |last5=Mattioli |first5=Emanuela |last6=Heimhofer |first6=Ulrich |last7=Kabiri |first7=Lahcen |date=19 December 2015 |title=Perturbation of the carbon cycle during the late Pliensbachian -- early Toarcian: New insight from high-resolution carbon isotope records in Morocco |url=https://www.sciencedirect.com/science/article/pii/S1464343X15301412 |journal=Journal of African Earth Sciences |volume=116 |pages=89–104 |doi=10.1016/j.jafrearsci.2015.12.018 |access-date=10 March 2024 |via=Elsevier Science Direct|url-access=subscription }}</ref> The Karoo-Ferrar magmatism released so much carbon dioxide that it disrupted the imprint of the 9 Myr long-term carbon cycle that was otherwise steady and stable during the Jurassic and Early Cretaceous.<ref>{{Cite journal |last1=Martinez |first1=Mathieu |last2=Dera |first2=Guillaume |date=13 October 2015 |title=Orbital pacing of carbon fluxes by a ∼9-My eccentricity cycle during the Mesozoic |journal=Proceedings of the National Academy of Sciences of the United States of America |language=en |volume=112 |issue=41 |pages=12604–12609 |doi=10.1073/pnas.1419946112 |issn=0027-8424 |pmc=4611626 |pmid=26417080 |doi-access=free|bibcode=2015PNAS..11212604M }}</ref> The values of ¹⁸⁷Os/¹⁸⁸Os rose from ~0.40 to ~0.53 during the PTo-E and from ~0.42 to ~0.68 during the TOAE, and many scholars conclude this change in osmium isotope ratios evidences the responsibility of this large igneous province for the biotic crises.<ref>{{cite journal |last1=Percival |first1=L. M. E. |last2=Cohen |first2=A. S. |last3=Davies |first3=M. K. |last4=Dickson |first4=A. J. |last5=Hesselbo |first5=Stephen P. |last6=Jenkyns |first6=Hugh C. |last7=Leng |first7=M. J. |last8=Mather |first8=Tamsin A. |last9=Storm |first9=M. S. |last10=Xu |first10=W. |date=1 September 2016 |title=Osmium isotope evidence for two pulses of increased continental weathering linked to Early Jurassic volcanism and climate change |journal=Geology |volume=44 |issue=9 |pages=759–762 |doi=10.1130/G37997.1 |bibcode=2016Geo....44..759P |s2cid=22328529 |doi-access=free |hdl=10871/22441 |hdl-access=free }}</ref> Mercury anomalies from the approximate time intervals corresponding to the PTo-E and TOAE have likewise been invoked as tell-tale evidence of the ecological calamity's cause being a large igneous province,<ref>{{Cite journal |last1=Fendley |first1=Isabel M. |last2=Frieling |first2=Joost |last3=Mather |first3=Tamsin A. |last4=Ruhl |first4=Micha |last5=Hesselbo |first5=Stephen P. |last6=Jenkyns |first6=Hugh C. |date=26 February 2024 |title=Early Jurassic large igneous province carbon emissions constrained by sedimentary mercury |journal=Nature Geoscience |language=en |volume=17 |issue=3 |pages=241–248 |doi=10.1038/s41561-024-01378-5 |bibcode=2024NatGe..17..241F |issn=1752-0894 |doi-access=free |hdl=10871/135668 |hdl-access=free }}</ref><ref>{{cite journal |last1=Percival |first1=Lawrence M. E. |last2=Witt |first2=M. L. I. |last3=Mather |first3=Tamsin A. |last4=Hermoso |first4=M. |last5=Jenkyns |first5=Hugh C. |last6=Hesselbo |first6=Stephen P. |last7=Al-Suwaidi |first7=A. H. |last8=Storm |first8=M. S. |last9=Xu |first9=W. |last10=Ruhl |first10=M. |date=15 October 2015 |title=Globally enhanced mercury deposition during the end-Pliensbachian extinction and Toarcian OAE: A link to the Karoo–Ferrar Large Igneous Province |url=https://www.sciencedirect.com/science/article/pii/S0012821X15004276 |journal=Earth and Planetary Science Letters |volume=428 |pages=267–280 |doi=10.1016/j.epsl.2015.06.064 |bibcode=2015E&PSL.428..267P |access-date=28 March 2023|hdl=10871/22245 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Kovács |first1=E.B. |last2=Ruhl |first2=M. |last3=Silva |first3=R.L. |last4=McElwain |first4=J.C. |last5=Reolid |first5=M. |last6=Korte |first6=C. |last7=Ruebsam |first7=W. |last8=Hesselbo |first8=S.P. |date=1 March 2024 |title=Mercury sequestration pathways under varying depositional conditions during Early Jurassic (Pliensbachian and Toarcian) Karoo-Ferrar volcanism |url=https://www.sciencedirect.com/science/article/pii/S0031018223005953 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=637 |article-number=111977 |doi=10.1016/j.palaeo.2023.111977 |bibcode=2024PPP...63711977K |access-date=25 October 2024 |via=Elsevier Science Direct|url-access=subscription }}</ref> although some researchers attribute these elevated mercury levels to increased terrigenous flux.<ref>{{cite journal |last1=Them II |first1=T. R. |last2=Jagoe |first2=C. H. |last3=Caruthers |first3=A. H. |last4=Gill |first4=B. C. |last5=Grasby |first5=Stephen E. |last6=Gröcke |first6=D. R. |last7=Yin |first7=R. |last8=Owens |first8=J. D. |date=1 February 2019 |title=Terrestrial sources as the primary delivery mechanism of mercury to the oceans across the Toarcian Oceanic Anoxic Event (Early Jurassic) |journal=Earth and Planetary Science Letters |volume=507 |pages=62–72 |doi=10.1016/j.epsl.2018.11.029 |bibcode=2019E&PSL.507...62T |s2cid=135426425 |doi-access=free }}</ref> There is evidence that the motion of the African Plate suddenly changed in velocity, shifting from mostly northward movement to southward movement. Such shifts in plate motion are associated with similar large igneous provinces emplaced in other time intervals.<ref>{{cite journal |last1=Ruhl |first1=Micha |last2=Hesselbo |first2=Stephen P. |last3=Jenkyns |first3=Hugh C. |last4=Xu |first4=Weimu |last5=Silva |first5=Ricardo L. |last6=Matthews |first6=Kara J. |last7=Mather |first7=Tamsin A. |last8=Niocaill |first8=Conall Mac |last9=Riding |first9=James B. |date=9 September 2022 |title=Reduced plate motion controlled timing of Early Jurassic Karoo-Ferrar large igneous province volcanism |journal=Science Advances |volume=8 |issue=36 |article-number=eabo0866 |doi=10.1126/sciadv.abo0866 |pmid=36083904 |pmc=9462690 |bibcode=2022SciA....8O.866R |hdl=10871/130801 }}</ref> A 2019 geochronological study found that the emplacement of the Karoo-Ferrar large igneous province and the TOAE were not causally linked, and simply happened to occur rather close in time, contradicting mainstream interpretations of the TOAE. The authors of the study conclude that the timeline of the TOAE does not match up with the course of activity of the Karoo-Ferrar magmatic event.<ref>{{cite journal |last1=De Lena |first1=Luis F. |last2=Taylor |first2=David |last3=Guex |first3=Jean |last4=Bartolini |first4=Annachiara |last5=Adatte |first5=Thierry |last6=Van Acken |first6=David |last7=Spangenberg |first7=Jorge E. |last8=Samankassou |first8=Elias |last9=Vennemann |first9=Torsten |last10=Schaltegger |first10=Urs |date=5 December 2019 |title=The driving mechanisms of the carbon cycle perturbations in the late Pliensbachian (Early Jurassic) |journal=Scientific Reports |volume=9 |issue=1 |page=18430 |doi=10.1038/s41598-019-54593-1 |pmid=31804521 |pmc=6895128 |s2cid=208622686 }}</ref>

The large igneous province also intruded into coal seams, releasing even more carbon dioxide and methane than it otherwise would have.<ref>{{cite book |last1=Svensen |first1=Henrik H. |last2=Hammer |first2=Øyvind |last3=Chevallier |first3=Luc |last4=Jerram |first4=Dougal A. |last5=Silkoset |first5=Petter |last6=Polteau |first6=Stephane |last7=Planke |first7=Sverre |editor-last1=Adatte |editor-first1=Thierry |editor-last2=Bond |editor-first2=David P. G. |editor-last3=Keller |editor-first3=Gerta |date=6 March 2020 |title=Mass Extinctions, Volcanism, and Impacts: New Developments |url=https://pubs.geoscienceworld.org/gsa/books/book/2205/Mass-Extinctions-Volcanism-and-Impacts-New |chapter=Understanding thermogenic degassing in large igneous provinces: Inferences from the geological and statistical characteristics of breccia pipes in the western parts of the Karoo Basin |chapter-url=https://pubs.geoscienceworld.org/gsa/books/book/2205/chapter-abstract/124998644/Understanding-thermogenic-degassing-in-large?redirectedFrom=fulltext |publisher=Geological Society of America |doi=10.1130/2020.2544(03) |isbn=978-0-8137-9544-7|s2cid=218829332 }}</ref><ref>{{cite journal |last1=McElwain |first1=Jennifer C. |last2=Wade-Murphy |first2=Jessica |last3=Hesselbo |first3=Stephen P. |date=26 May 2005 |title=Changes in carbon dioxide during an oceanic anoxic event linked to intrusion into Gondwana coals |url=https://www.nature.com/articles/nature03618?error=cookies_not_supported&code=2345c781-b851-4d01-bcef-5615f1252f11 |journal=Nature |volume=435 |issue=7041 |pages=479–482 |doi=10.1038/nature03618 |pmid=15917805 |bibcode=2005Natur.435..479M |s2cid=4339259 |access-date=7 January 2023|url-access=subscription }}</ref><ref name="ThemEtAl" /> Magmatic sills are also known to have intruded into shales rich in organic carbon, causing additional venting of carbon dioxide into the atmosphere.<ref>{{cite journal |last1=Svensen |first1=Henrik |last2=Planke |first2=Sverre |last3=Chevallier |first3=Luc |last4=Malthe-Sørenssen |first4=Anders |last5=Corfu |first5=Fernando |last6=Jamtveit |first6=Bjørn |date=30 April 2007 |title=Hydrothermal venting of greenhouse gases triggering Early Jurassic global warming |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X07000763 |journal=Earth and Planetary Science Letters |volume=256 |issue=3–4 |pages=554–566 |doi=10.1016/j.epsl.2007.02.013 |bibcode=2007E&PSL.256..554S |access-date=20 January 2023|url-access=subscription }}</ref> Carbon release via metamorphic heating of coal has been criticised as a major driver of the environmental perturbation, however, on the basis that coal transects themselves do not show the δ¹³C excursions that would be expected if significant quantities of thermogenic methane were released, suggesting that much of the degassed emissions were either condensed as pyrolytic carbon or trapped as coalbed methane.<ref>{{cite journal |last1=Gröcke |first1=Darren R. |last2=Rimmer |first2=Susan M. |last3=Yoksoulian |first3=Lois E. |last4=Cairncross |first4=Bruce |last5=Tsikos |first5=Harilaos |last6=Van Hunen |first6=Jaroen |date=15 January 2009 |title=No evidence for thermogenic methane release in coal from the Karoo-Ferrar large igneous province |url=https://www.sciencedirect.com/science/article/pii/S0012821X08006808 |journal=Earth and Planetary Science Letters |volume=277 |issue=1–2 |pages=204–212 |doi=10.1016/j.epsl.2008.10.022 |bibcode=2009E&PSL.277..204G |access-date=10 March 2024|url-access=subscription }}</ref>

In addition, possible associated release of deep sea methane clathrates has been potentially implicated as yet another cause of global warming.<ref>{{cite journal |last1=Hesselbo |first1=Stephen P. |last2=Gröcke |first2=Darren R. |last3=Jenkyns |first3=Hugh C. |last4=Bjerrum |first4=Christian J. |last5=Farrimond |first5=Paul |last6=Morgans-Bell |first6=Helen S. |last7=Green |first7=Owen R. |date=27 July 2000 |title=Massive dissociation of gas hydrate during a Jurassic oceanic anoxic event |url=https://www.nature.com/articles/35019044?error=cookies_not_supported&code=6443966f-d7bf-436b-89df-9beee4f58c77 |journal=Nature |volume=406 |issue=6794 |pages=392–395 |doi=10.1038/35019044 |pmid=10935632 |bibcode=2000Natur.406..392H |s2cid=4426788 |access-date=7 January 2023|url-access=subscription }}</ref><ref name="Cohen2007">{{cite journal |last1=Cohen |first1=Anthony S. |last2=Coe |first2=Angela L. |last3=Kemp |first3=David B. |date=15 October 2007 |title=The Late Palaeocene–Early Eocene and Toarcian (Early Jurassic) carbon isotope excursions: a comparison of their time scales, associated environmental changes, causes and consequences |url=https://www.lyellcollection.org/doi/10.1144/0016-76492006-123 |journal=Journal of the Geological Society |volume=163 |issue=6 |pages=1093–1108 |doi=10.1144/0016-76492006-123 |bibcode=2007JGSoc.164.1093C |s2cid=129509486 |access-date=20 January 2023|url-access=subscription }}</ref><ref>{{cite journal |last1=Remírez |first1=Mariano N. |last2=Algeo |first2=Thomas J. |date=October 2020 |title=Carbon-cycle changes during the Toarcian (Early Jurassic) and implications for regional versus global drivers of the Toarcian oceanic anoxic event |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825220303299 |journal=Earth-Science Reviews |volume=209 |article-number=103283 |doi=10.1016/j.earscirev.2020.103283 |bibcode=2020ESRv..20903283R |s2cid=225572000 |access-date=23 June 2023|url-access=subscription }}</ref> Episodic melting of methane clathrates dictated by Milankovitch cycles has been put forward as an explanation fitting the observed shifts in the carbon isotope record.<ref>{{Cite journal |last1=Kemp |first1=David B. |last2=Coe |first2=Angela L. |last3=Cohen |first3=Anthony S. |last4=Schwark |first4=Lorenz |date=15 September 2009 |title=Astronomical pacing of methane release in the Early Jurassic period |url=https://www.nature.com/articles/nature04037 |journal=Nature |language=en |volume=437 |issue=7057 |pages=396–399 |doi=10.1038/nature04037 |pmid=16163353 |issn=1476-4687 |access-date=22 February 2025|url-access=subscription }}</ref><ref>{{cite journal |last1=Ikeda |first1=Masayuki |last2=Hori |first2=Rie S. |last3=Ikehara |first3=Minoru |last4=Miyashita |first4=Ren |last5=Chino |first5=Masashi |last6=Yamada |first6=Kazuyoshi |date=November 2018 |title=Carbon cycle dynamics linked with Karoo-Ferrar volcanism and astronomical cycles during Pliensbachian-Toarcian (Early Jurassic) |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818118302698 |journal=Global and Planetary Change |volume=170 |pages=163–171 |doi=10.1016/j.gloplacha.2018.08.012 |bibcode=2018GPC...170..163I |s2cid=133856684 |access-date=14 June 2023|url-access=subscription }}</ref><ref>{{cite journal |last1=Kemp |first1=David B. |last2=Coe |first2=Angela L. |last3=Cohen |first3=Anthony S. |last4=Weedon |first4=Graham P. |date=1 November 2011 |title=Astronomical forcing and chronology of the early Toarcian (Early Jurassic) oceanic anoxic event in Yorkshire, UK |journal=Paleoceanography and Paleoclimatology |volume=26 |issue=4 |pages=1–17 |article-number=2011PA002122 |doi=10.1029/2011PA002122 |bibcode=2011PalOc..26.4210K |doi-access=free }}</ref> Other studies contradict and reject the methane hydrate hypothesis, however, concluding that the isotopic record is too incomplete to conclusively attribute the isotopic excursion to methane hydrate dissociation,<ref>{{cite journal |last1=McArthur |first1=J. M. |last2=Cohen |first2=A. S. |last3=Coe |first3=A. L. |last4=Kemp |first4=David B. |last5=Bailey |first5=R. J. |last6=Smith |first6=D. G. |date=5 June 2008 |title=Discussion on the Late Palaeocene–Early Eocene and Toarcian (Early Jurassic) carbon isotope excursions: a comparison of their time scales, associated environmental change, causes and consequencesJournal, Vol. 164, 2007, 1093–1108 |url=https://www.lyellcollection.org/doi/10.1144/0016-76492007-157 |journal=Journal of the Geological Society |volume=165 |issue=4 |pages=875–880 |doi=10.1144/0016-76492007-157 |bibcode=2008JGSoc.165..875M |s2cid=131586390 |access-date=20 January 2023|url-access=subscription }}</ref> that carbon isotope ratios in belemnites and bulk carbonates are incongruent with the isotopic signature expected from a massive release of methane clathrates,<ref>{{cite journal |last1=Van de Schootbrugge |first1=B. |last2=McArthur |first2=J. M. |last3=Bailey |first3=T. R. |last4=Rosenthal |first4=Y. |last5=Wright |first5=J. D. |last6=Miller |first6=K. G. |date=26 August 2005 |title=Toarcian oceanic anoxic event: An assessment of global causes using belemnite C isotope records |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2004PA001102 |journal=Paleoceanography and Paleoclimatology |volume=20 |issue=3 |pages=1–10 |article-number=2004PA001102 |doi=10.1029/2004PA001102 |bibcode=2005PalOc..20.3008V |access-date=7 January 2023|url-access=subscription }}</ref> that much of the methane released from ocean sediments was rapidly sequestered, buffering its ability to act as a major positive feedback,<ref>{{cite journal |last1=Beerling |first1=David J. |last2=Lomas |first2=M. R. |last3=Gröcke |first3=Darren R. |date=January 2002 |title=On the nature of methane gas-hydrate dissociation during the Toarcian and Aptian Oceanic anoxic events |url=https://www.ajsonline.org/content/302/1/28 |journal=American Journal of Science |volume=302 |issue=1 |pages=28–49 |doi=10.2475/ajs.302.1.28 |bibcode=2002AmJS..302...28B |access-date=7 January 2023|url-access=subscription }}</ref> and that methane clathrate dissociation occurred too late to have had an appreciable causal impact on the extinction event.<ref>{{cite journal |last1=Wignall |first1=Paul B. |last2=Newton |first2=Robert J. |last3=Little |first3=Crispin T. S. |date=December 2005 |title=The timing of paleoenvironmental change and cause-and-effect relationships during the early Jurassic mass extinction in Europe |url=https://www.ajsonline.org/content/305/10/1014 |journal=American Journal of Science |volume=305 |issue=10 |pages=1014–1032 |doi=10.2475/ajs.305.10.1014 |bibcode=2005AmJS..305.1014W |access-date=7 January 2023|url-access=subscription }}</ref> Hypothetical release of methane clathrates extremely depleted in heavy carbon isotopes has furthermore been considered unnecessary as an explanation for the carbon cycle disruption.<ref>{{cite journal |last1=Heimdal |first1=Thea H. |last2=Goddéris |first2=Yves |last3=Jones |first3=Morgan T. |last4=Svensen |first4=Henrik H. |date=28 October 2021 |title=Assessing the importance of thermogenic degassing from the Karoo Large Igneous Province (LIP) in driving Toarcian carbon cycle perturbations |journal=Nature Communications |volume=12 |issue=1 |page=6221 |pmid=34711826 |doi=10.1038/s41467-021-26467-6 |pmc=8553747 |bibcode=2021NatCo..12.6221H }}</ref>

It has also been hypothesised that the release of cryospheric methane trapped in permafrost amplified the warming and its detrimental effects on marine life.<ref>{{cite journal |last1=Krencker |first1=François-Nicolas |last2=Lindström |first2=Sofie |last3=Bodin |first3=Stéphane |date=29 August 2019 |title=A major sea-level drop briefly precedes the Toarcian oceanic anoxic event: implication for Early Jurassic climate and carbon cycle |journal=Scientific Reports |volume=9 |issue=1 |page=12518 |doi=10.1038/s41598-019-48956-x |pmid=31467345 |pmc=6715628 |bibcode=2019NatSR...912518K }}</ref><ref>{{cite journal |last1=Ruebsam |first1=Wolfgang |last2=Reolid |first2=Matías |last3=Schwark |first3=Lorenz |date=10 January 2020 |title=δ13C of terrestrial vegetation records Toarcian CO2 and climate gradients |journal=Scientific Reports |volume=10 |issue=1 |page=117 |doi=10.1038/s41598-019-56710-6 |pmid=31924807 |pmc=6954244 |bibcode=2020NatSR..10..117R }}</ref> Obliquity-paced carbon isotope excursions have been interpreted as some researchers as reflective of permafrost decline and consequent greenhouse gas release.<ref>{{cite journal |last1=Ruebsam |first1=Wolfgang |last2=Mayer |first2=Bernhard |last3=Schwark |first3=Lorenz |date=January 2019 |title=Cryosphere carbon dynamics control early Toarcian global warming and sea level evolution |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818118305009 |journal=Global and Planetary Change |volume=172 |pages=440–453 |doi=10.1016/j.gloplacha.2018.11.003 |bibcode=2019GPC...172..440R |s2cid=133660136 |access-date=7 January 2023|url-access=subscription }}</ref><ref>{{cite journal |last1=Ruebsam |first1=Wolfgang |last2=Münzberger |first2=Petra |last3=Schwark |first3=Lorenz |date=23 August 2014 |title=Chronology of the Early Toarcian environmental crisis in the Lorraine Sub-Basin (NE Paris Basin) |url=https://www.sciencedirect.com/science/article/pii/S0012821X14005032 |journal=Earth and Planetary Science Letters |volume=404 |pages=273–282 |doi=10.1016/j.epsl.2014.08.005 |bibcode=2014E&PSL.404..273R |access-date=10 March 2024|url-access=subscription }}</ref>

The TOAE is believed to be the second largest anoxic event of the last 300 Ma,<ref>{{Cite journal |last1=Remírez |first1=Mariano N. |last2=Gilleaudeau |first2=Geoffrey J. |last3=Gan |first3=Tian |last4=Kipp |first4=Michael A. |last5=Tissot |first5=François L. H. |last6=Kaufman |first6=Alan J. |last7=Parente |first7=Mariano |date=24 June 2024 |title=Carbonate uranium isotopes record global expansion of marine anoxia during the Toarcian Oceanic Anoxic Event |journal=Proceedings of the National Academy of Sciences of the United States of America |language=en |volume=121 |issue=27 |article-number=e2406032121 |doi=10.1073/pnas.2406032121 |doi-access=free |pmid=38913904 |pmc=11228476 |bibcode=2024PNAS..12106032R |issn=0027-8424 }}</ref> and possibly the largest of the Phanerozoic.<ref name="BelemniteEcology" /> A positive δ¹³C excursion, likely resulting from the mass burial of organic carbon during the anoxic event, is known from the ''falciferum'' ammonite zone, chemostratigraphically identifying the TOAE.<ref>{{cite journal |last1=Jenkyns |first1=Hugh C. |date=February 1998 |title=The early Toarcian ( Jurassic) anoxic event: stratigraphic, sedimentary, and geochemical evidence |url=https://www.researchgate.net/publication/277467795 |journal=American Journal of Science |volume=288 |issue=2 |pages=101–151 |doi=10.2475/ajs.288.2.101 |access-date=4 January 2023}}</ref> Large igneous province resulted in increased silicate weathering and an acceleration of the hydrological cycle,<ref>{{cite journal |last1=Kemp |first1=David B. |last2=Izumi |first2=Kentaro |date=15 November 2014 |title=Multiproxy geochemical analysis of a Panthalassic margin record of the early Toarcian oceanic anoxic event (Toyora area, Japan) |url=https://www.sciencedirect.com/science/article/pii/S003101821400474X |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=414 |pages=332–341 |doi=10.1016/j.palaeo.2014.09.019 |bibcode=2014PPP...414..332K |access-date=8 January 2023|hdl=2164/4381 |hdl-access=free }}</ref><ref>{{cite journal |last1=Tremolada |first1=Fabrizio |last2=Van de Schootbrugge |first2=Bas |last3=Erba |first3=Elisabetta |date=3 June 2005 |title=Early Jurassic schizosphaerellid crisis in Cantabria, Spain: Implications for calcification rates and phytoplankton evolution across the Toarcian oceanic anoxic event |journal=Paleoceanography and Paleoclimatology |volume=20 |issue=2 |pages=1–11 |article-number=2004PA001120 |doi=10.1029/2004PA001120 |bibcode=2005PalOc..20.2011T |doi-access=free }}</ref> as shown by an increased amount of terrestrially derived organic matter found in sedimentary rocks of marine origin during the TOAE.<ref>{{cite journal |last1=Rodrigues |first1=Bruno |last2=Duarte |first2=Luís V. |last3=Silva |first3=Ricardo L. |last4=Mendonça Filho |first4=João Graciano |date=15 September 2020 |title=Sedimentary organic matter and early Toarcian environmental changes in the Lusitanian Basin (Portugal) |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018220302261 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=554 |article-number=109781 |bibcode=2020PPP...55409781R |doi=10.1016/j.palaeo.2020.109781 |access-date=27 September 2022 |s2cid=219059687|url-access=subscription }}</ref><ref>{{cite journal |last1=Rodrigues |first1=Bruno |last2=Silva |first2=Ricardo L. |last3=Mendonça Filho |first3=João Graciano |last4=Comas-Rengifo |first4=María J. |last5=Goy |first5=Antonio |last6=Duarte |first6=Luís V. |date=1 September 2020 |title=Kerogen assemblages and δ13CKerogen of the uppermost Pliensbachian–lower Toarcian succession of the Asturian Basin (northern Spain) |url=https://www.sciencedirect.com/science/article/abs/pii/S0166516220305693 |journal=International Journal of Coal Geology |volume=229 |article-number=103573 |doi=10.1016/j.coal.2020.103573 |bibcode=2020IJCG..22903573R |s2cid=225331537 |access-date=14 May 2023|url-access=subscription }}</ref> Concentrations of phosphorus, magnesium, and manganese rose in the oceans.<ref>{{Cite journal |last1=Silva |first1=Ricardo L. |last2=Gómez |first2=Juan J. |last3=Fraguas |first3=Ángela |date=20 November 2024 |title=New insights on Late Pliensbachian-Early Toarcian seawater chemistry based on belemnite rostra element content |journal=Chemical Geology |language=en |volume=668 |article-number=122327 |doi=10.1016/j.chemgeo.2024.122327 |doi-access=free }}</ref> A -0.5% excursion in δ^44/40Ca provides further evidence of increased continental weathering.<ref>{{Cite journal |last1=Brazier |first1=Jean-Michel |last2=Suan |first2=Guillaume |last3=Tacail |first3=Théo |last4=Simon |first4=Laurent |last5=Martin |first5=Jeremy E. |last6=Mattioli |first6=Emanuela |last7=Balter |first7=Vincent |date=1 February 2015 |title=Calcium isotope evidence for dramatic increase of continental weathering during the Toarcian oceanic anoxic event (Early Jurassic) |url=https://www.sciencedirect.com/science/article/pii/S0012821X14007201 |journal=Earth and Planetary Science Letters |volume=411 |pages=164–176 |doi=10.1016/j.epsl.2014.11.028 |bibcode=2015E&PSL.411..164B |issn=0012-821X |access-date=26 November 2023|url-access=subscription }}</ref> Osmium isotope ratios confirm further still a major increase in weathering.<ref>{{Cite journal |last1=Them |first1=Theodore R. |last2=Gill |first2=Benjamin C. |last3=Selby |first3=David |last4=Gröcke |first4=Darren R. |last5=Friedman |first5=Richard M. |last6=Owens |first6=Jeremy D. |date=10 July 2017 |title=Evidence for rapid weathering response to climatic warming during the Toarcian Oceanic Anoxic Event |journal=Scientific Reports |language=en |volume=7 |issue=1 |page=5003 |doi=10.1038/s41598-017-05307-y |pmid=28694487 |pmc=5504049 |bibcode=2017NatSR...7.5003T |issn=2045-2322 |hdl=10919/81873 |hdl-access=free }}</ref> The enhanced continental weathering in turn led to increased eutrophication that helped drive the anoxic event in the oceans.<ref name="XiaMansour2022">{{cite journal |last1=Xia |first1=Guoqing |last2=Mansour |first2=Ahmed |date=1 October 2022 |title=Paleoenvironmental changes during the early Toarcian Oceanic Anoxic Event: Insights into organic carbon distribution and controlling mechanisms in the eastern Tethys |url=https://www.sciencedirect.com/science/article/abs/pii/S1367912022002759 |journal=Journal of Asian Earth Sciences |volume=237 |article-number=105344 |doi=10.1016/j.jseaes.2022.105344 |bibcode=2022JAESc.23705344X |s2cid=250976430 |access-date=8 January 2023|url-access=subscription }}</ref><ref name="SlaterTwitchettDaniseVajda2019">{{cite journal |last1=Slater |first1=Sam M. |last2=Twitchett |first2=Richard J. |last3=Danise |first3=Silvia |last4=Vajda |first4=Vivi |date=29 April 2019 |title=Substantial vegetation response to Early Jurassic global warming with impacts on oceanic anoxia |url=https://www.nature.com/articles/s41561-019-0349-z?error=cookies_not_supported&code=9b2cf5a2-6cd7-4d1f-be00-ee8b1c0e1073 |journal=Nature Geoscience |volume=12 |issue=6 |pages=462–467 |doi=10.1038/s41561-019-0349-z |bibcode=2019NatGe..12..462S |s2cid=155624907 |access-date=17 December 2022}}</ref><ref>{{Cite journal |last1=Montero-Serrano |first1=Jean-Carlos |last2=Föllmi |first2=Karl B. |last3=Adatte |first3=Thierry |last4=Spangenberg |first4=Jorge E. |last5=Tribovillard |first5=Nicolas |last6=Fantasia |first6=Alicia |last7=Suan |first7=Guillaume |date=16 April 2015 |title=Continental weathering and redox conditions during the early Toarcian Oceanic Anoxic Event in the northwestern Tethys: Insight from the Posidonia Shale section in the Swiss Jura Mountains |url=https://www.sciencedirect.com/science/article/pii/S0031018215001832 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=429 |pages=83–99 |doi=10.1016/j.palaeo.2015.03.043 |bibcode=2015PPP...429...83M |access-date=10 March 2024 |via=Elsevier Science Direct|url-access=subscription }}</ref> Waters underwent partial denitrification in conjunction with enhanced marine productivity.<ref>{{Cite journal |last1=Jenkyns |first1=Hugh C. |last2=Gröcke |first2=Darren R. |last3=Hesselbo |first3=Stephen P. |date=December 2001 |title=Nitrogen isotope evidence for water mass denitrification during the Early Toarcian (Jurassic) oceanic anoxic event |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2000PA000558 |journal=Paleoceanography and Paleoclimatology |language=en |volume=16 |issue=6 |pages=593–603 |doi=10.1029/2000PA000558 |bibcode=2001PalOc..16..593J |issn=0883-8305 |access-date=22 February 2025 |via=Wiley Online Library}}</ref> Continual transport of continentally weathered nutrients into the ocean enabled high levels of primary productivity to be maintained over the course of the TOAE.<ref name="BaileyEtAl2003GenesisOAE" /> Rising sea levels contributed to ocean deoxygenation;<ref>{{Cite journal |last1=Ruebsam |first1=Wolfgang |last2=Schwark |first2=Lorenz |date=5 May 2024 |title=Disparity between Toarcian Oceanic Anoxic Event and Toarcian carbon isotope excursion |journal=International Journal of Earth Sciences |volume=113 |issue=8 |pages=2065–2076 |language=en |doi=10.1007/s00531-024-02408-8 |issn=1437-3254 |doi-access=free |bibcode=2024IJEaS.113.2065R }}</ref> as rising sea levels inundated low-lying lands, organic plant matter was transported outwards into the ocean.<ref>{{cite journal |last1=Ruban |first1=Dmitry A. |year=2004 |title=Diversity dynamics of Early-Middle Jurassic brachiopods of Caucasus, and the Pliensbachian-Toarcian mass extinction |url=https://agro.icm.edu.pl/agro/element/bwmeta1.element.agro-article-5947f3c1-bfa8-4a98-a570-6bcde6300eaa |journal=Acta Palaeontologica Polonica |volume=49 |issue=2 |pages=275–282 |access-date=14 May 2023}}</ref> An alternate model for the development of anoxia is that epicontinental seaways became salinity stratified with strong haloclines, chemoclines, and thermoclines. This caused mineralised carbon on the seafloor to be recycled back into the photic zone, driving widespread primary productivity and in turn anoxia.<ref>{{cite journal |last1=Harazim |first1=Dario |last2=Van de Schootbrugge |first2=Bas |last3=Sorichter |first3=Katrin |last4=Fiebig |first4=Jens |last5=Weug |first5=Andries |last6=Suan |first6=Guillaume |last7=Oschmann |first7=Wolfgang |date=21 August 2012 |title=Spatial variability of watermass conditions within the European Epicontinental Seaway during the Early Jurassic (Pliensbachian–Toarcian) |url=https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-3091.2012.01344.x |journal=Sedimentology |volume=60 |issue=2 |pages=359–390 |doi=10.1111/j.1365-3091.2012.01344.x |s2cid=128946998 |access-date=8 April 2023|url-access=subscription }}</ref> The freshening of the Arctic Ocean by way of melting of Northern Hemisphere ice caps was a likely trigger of such stratification and a slowdown of global thermohaline circulation.<ref>{{cite journal |last1=Dera |first1=Guillaume |last2=Donnadieu |first2=Yannick |date=13 June 2012 |title=Modeling evidences for global warming, Arctic seawater freshening, and sluggish oceanic circulation during the Early Toarcian anoxic event |journal=Paleoceanography and Paleoclimatology |volume=27 |issue=2 |pages=1–15 |article-number=2012PA002283 |doi=10.1029/2012PA002283 |bibcode=2012PalOc..27.2211D |doi-access=free }}</ref> Stratification also occurred due to the freshening of surface water caused by an enhanced water cycle.<ref>{{Cite journal |last=Arias |first=Carmen |date=8 August 2007 |title=Pliensbachian–Toarcian ostracod biogeography in NW Europe: Evidence for water mass structure evolution |url=https://www.sciencedirect.com/science/article/pii/S0031018207002398 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=251 |issue=3 |pages=398–421 |doi=10.1016/j.palaeo.2007.04.014 |bibcode=2007PPP...251..398A |issn=0031-0182 |access-date=26 November 2023}}</ref><ref>{{Cite journal |last1=Baranyi |first1=Viktória |last2=Pálfy |first2=József |last3=Görög |first3=Ágnes |last4=Riding |first4=James B. |last5=Raucsik |first5=Béla |date=1 December 2016 |title=Multiphase response of palynomorphs to the Toarcian Oceanic Anoxic Event (Early Jurassic) in the Réka Valley section, Hungary |url=https://www.sciencedirect.com/science/article/pii/S0034666715300099 |journal=Review of Palaeobotany and Palynology |volume=235 |pages=51–70 |doi=10.1016/j.revpalbo.2016.09.011 |bibcode=2016RPaPa.235...51B |issn=0034-6667 |access-date=26 November 2023}}</ref> Rising seawater temperatures amidst a transition from icehouse to greenhouse conditions further retarded ocean circulation, aiding the establishment of anoxic conditions.<ref>{{cite journal |last1=Ruebsam |first1=Wolfgang |last2=Reolid |first2=Matías |last3=Marok |first3=Abbas |last4=Schwark |first4=Lorenz |date=April 2020 |title=Drivers of benthic extinction during the early Toarcian (Early Jurassic) at the northern Gondwana paleomargin: Implications for paleoceanographic conditions |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825219306841 |journal=Earth-Science Reviews |volume=203 |article-number=103117 |bibcode=2020ESRv..20303117R |doi=10.1016/j.earscirev.2020.103117 |s2cid=214230643 |access-date=14 May 2023|url-access=subscription }}</ref> Geochemical evidence from what was then the northwestern European epicontinental sea suggests that a shift from cooler, more saline water conditions to warmer, fresher conditions prompted the development of significant density stratification of the water column and induced anoxia.<ref name="BaileyEtAl2003GenesisOAE" /> The anoxia's intensity was mediated by orbital cycles.<ref>{{Cite journal |last1=Ikeda |first1=Masayuki |last2=Hori |first2=Rie S. |date=15 September 2014 |title=Effects of Karoo–Ferrar volcanism and astronomical cycles on the Toarcian Oceanic Anoxic Events (Early Jurassic) |url=https://www.sciencedirect.com/science/article/abs/pii/S003101821400282X |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=410 |pages=134–142 |doi=10.1016/j.palaeo.2014.05.026 |bibcode=2014PPP...410..134I |access-date=31 January 2025 |via=Elsevier Science Direct|url-access=subscription }}</ref> Extensive organic carbon burial induced by anoxia was a negative feedback loop retarding the otherwise pronounced warming and may have caused global cooling in the aftermath of the TOAE.<ref>{{cite journal |last1=Ruebsam |first1=Wolfgang |last2=Mattioli |first2=Emanuela |last3=Schwark |first3=Lorenz |date=October 2022 |title=Weakening of the biological pump induced by a biocalcification crisis during the early Toarcian Oceanic Anoxic Event |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818122002211 |journal=Global and Planetary Change |volume=217 |article-number=103954 |doi=10.1016/j.gloplacha.2022.103954 |bibcode=2022GPC...21703954R |s2cid=252571812 |access-date=5 August 2023|url-access=subscription }}</ref> In anoxic and euxinic marine basins in Europe, organic carbon burial rates increased by ~500%.<ref name="KempEtAl2022EarthScienceReviews" /> Furthermore, anoxia was not limited to oceans; large lakes also experienced oxygen depletion and black shale deposition.<ref>{{Cite journal |last1=Li |first1=Binbing |last2=Jin |first2=Xin |last3=Corso |first3=Jacopo Dal |last4=Ogg |first4=James G. |last5=Lang |first5=Xianguo |last6=Baranyi |first6=Viktória |last7=Preto |first7=Nereo |last8=Franceschi |first8=Marco |last9=Qiao |first9=Peijun |last10=Shi |first10=Zhiqiang |date=1 February 2023 |title=Complex pattern of environmental changes and organic matter preservation in the NE Ordos lacustrine depositional system (China) during the T-OAE (Early Jurassic) |url=https://www.sciencedirect.com/science/article/pii/S0921818123000188 |journal=Global and Planetary Change |volume=221 |article-number=104045 |doi=10.1016/j.gloplacha.2023.104045 |bibcode=2023GPC...22104045L |s2cid=256129000 |issn=0921-8181 |access-date=26 November 2023|url-access=subscription |hdl=11368/3046078 |hdl-access=free }}</ref><ref>{{cite book |last1=Xu |first1=Weimu |last2=Weijers |first2=Johan W. H. |last3=Ruhl |first3=Micha |last4=Idiz |first4=Erdem F. |last5=Jenkyns |first5=Hugh C. |last6=Riding |first6=James B. |last7=Gorbanenko |first7=Olga |last8=Hesselbo |first8=Stephen B. |editor-last1=Reolid |editor-first1=Matias |editor-last2=Duarte |editor-first2=Luis V. |editor-last3=Mattioli |editor-first3=Emanuela |editor-last4=Ruebsam |editor-first4=Wolfgang |date=3 November 2021 |title=Carbon Cycle and Ecosystem Response to the Jenkyns Event in the Early Toarcian (Jurassic) |url=https://pubs.geoscienceworld.org/gsl/books/edited-volume/2338/Carbon-Cycle-and-Ecosystem-Response-to-the-Jenkyns |chapter=Molecular and petrographical evidence for lacustrine environmental and biotic change in the palaeo-Sichuan mega-lake (China) during the Toarcian Oceanic Anoxic Event |series=Geological Society of London, Special Publications |volume=514 |issue=1 |page=335 |chapter-url=https://pubs.geoscienceworld.org/gsl/books/edited-volume/2338/chapter-abstract/132175319/Molecular-and-petrographical-evidence-for?redirectedFrom=fulltext |publisher=The Geological Society of London |doi=10.1144/SP514-2021-2 |bibcode=2021GSLSP.514..335X |isbn=978-1-78620-999-3 |s2cid=236377708 |access-date=26 November 2023}}</ref>

Euxinia occurred in the northwestern Tethys Ocean during the TOAE, as shown by a positive δ³⁴S excursion in carbonate-associated sulphate occurs synchronously with the positive δ¹³C excursion in carbonate carbon during the ''falciferum'' ammonite zone. This positive δ³⁴S excursion has been attributed to the depletion of isotopically light sulphur in the marine sulphate reservoir that resulted from microbial sulphur reduction in anoxic waters.<ref>{{cite journal |last1=Gill |first1=Benjamin C. |last2=Lyons |first2=Timothy W. |last3=Jenkyns |first3=Hugh C. |date=15 December 2011 |title=A global perturbation to the sulfur cycle during the Toarcian Oceanic Anoxic Event |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X1100625X |journal=Earth and Planetary Science Letters |volume=312 |issue=3–4 |pages=484–496 |bibcode=2011E&PSL.312..484G |doi=10.1016/j.epsl.2011.10.030 |access-date=4 January 2023|url-access=subscription }}</ref> Similar positive δ³⁴S excursions corresponding to the onset of TOAE are known from pyrites in the Sakahogi and Sakuraguchi-dani localities in Japan, with the Sakahogi site displaying a less extreme but still significant pyritic positive δ³⁴S excursion during the PTo-E.<ref>{{cite journal |last1=Chen |first1=Wenhan |last2=Kemp |first2=David B. |last3=Newton |first3=Robert J. |last4=He |first4=Tianchen |last5=Wang |first5=Chunju |last6=Cho |first6=Tenichi |last7=Izumi |first7=Kentaro |date=August 2022 |title=Major sulfur cycle perturbations in the Panthalassic Ocean across the Pliensbachian-Toarcian boundary and the Toarcian Oceanic Anoxic Event |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818122001515 |journal=Global and Planetary Change |volume=215 |article-number=103884 |bibcode=2022GPC...21503884C |doi=10.1016/j.gloplacha.2022.103884 |s2cid=250239852 |access-date=25 March 2023|url-access=subscription }}</ref> Euxinia is further evidenced by enhanced pyrite burial in Zázrivá, Slovakia,<ref>{{cite journal |last1=Suan |first1=Guillaume |last2=Schöllhorn |first2=Iris |last3=Schlögl |first3=Ján |last4=Segit |first4=Tomasz |last5=Mattioli |first5=Emanuela |last6=Lécuyer |first6=Christophe |last7=Fourel |first7=François |date=November 2018 |title=Euxinic conditions and high sulfur burial near the European shelf margin (Pieniny Klippen Belt, Slovakia) during the Toarcian oceanic anoxic event |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818118302017 |journal=Global and Planetary Change |language=en |volume=170 |pages=246–259 |doi=10.1016/j.gloplacha.2018.09.003 |bibcode=2018GPC...170..246S |s2cid=134096973 |access-date=26 March 2023|url-access=subscription }}</ref> enhanced molybdenum burial totalling about 41 Gt of molybdenum,<ref>{{cite journal |last1=Them II |first1=T. R. |last2=Owens |first2=J. D. |last3=Marroquín |first3=S. M. |last4=Caruthers |first4=Andrew H. |last5=Trabucho Alexandre |first5=J. P. |last6=Gill |first6=B. C. |date=22 November 2022 |title=Reduced Marine Molybdenum Inventory Related to Enhanced Organic Carbon Burial and an Expansion of Reducing Environments in the Toarcian (Early Jurassic) Oceans |url=https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022AV000671 |journal=AGU Advances |volume=3 |issue=6 |article-number=e2022AV000671 |doi=10.1029/2022AV000671 |bibcode=2022AGUA....300671T |access-date=16 August 2023|hdl=10919/112946 |s2cid=253829543 |hdl-access=free }}</ref> and δ^98/95Mo excursions observed in sites in the Cleveland, West Netherlands, and South German Basins.<ref>{{cite journal |last1=Gibson |first1=Alexander J. |last2=Gill |first2=Benjamin C. |last3=Ruhl |first3=Micha |last4=Jenkyns |first4=Hugh C. |last5=Porcelli |first5=Donald |last6=Idiz |first6=Erdem |last7=Lyons |first7=Timothy W. |last8=Van den Boorn |first8=Sander H. J. M. |date=27 June 2017 |title=Molybdenum-isotope chemostratigraphy and paleoceanography of the Toarcian Oceanic Anoxic Event (Early Jurassic) |journal=Paleoceanography and Paleoclimatology |volume=32 |issue=8 |pages=813–829 |doi=10.1002/2016PA003048 |bibcode=2017PalOc..32..813D |s2cid=134242946 |doi-access=free }}</ref> Valdorbia, a site in the Umbria-Marche Apennines, also exhibited euxinia during the anoxic event.<ref name="SabatinoEtAl2009" /> There is less evidence of euxinia outside the northwestern Tethys, and it likely only occurred transiently in basins in Panthalassa and the southwestern Tethys.<ref>{{cite journal |last1=Fernández-Martínez |first1=Javier |last2=Martínez Ruíz |first2=Francisca |last3=Rodríguez-Tovar |first3=Francisco J. |last4=Piñuela |first4=Laura |last5=García-Ramos |first5=José C. |last6=Algeo |first6=Thomas J. |date=February 2023 |title=Euxinia and hydrographic restriction in the Tethys Ocean: Reassessing global oceanic anoxia during the early Toarcian |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818122002934 |journal=Global and Planetary Change |volume=221 |article-number=104026 |doi=10.1016/j.gloplacha.2022.104026 |bibcode=2023GPC...22104026F |s2cid=255324488 |access-date=2 April 2023|url-access=subscription |hdl=10261/343374 |hdl-access=free }}</ref> Due to the clockwise circulation of the oceanic gyre in the western Tethys and the rough, uneven bathymetry in the northward limb of this gyre, oxic bottom waters had relatively few impediments to diffuse into the southwestern Tethys, which spared it from the far greater prevalence of anoxia and euxinia that characterised the northern Tethys.<ref>{{cite journal |last1=Baroni |first1=Itzel Ruvalcaba |last2=Pohl |first2=Alexandre |last3=Van Helmond |first3=Niels A. G. M. |last4=Papadomanolaki |first4=Nina M. |last5=Coe |first5=Angela L. |last6=Cohen |first6=Anthony S. |last7=Van de Schootbrugge |first7=Bas |last8=Donnadieu |first8=Yannick |last9=Slomp |first9=Caroline P. |date=25 August 2018 |title=Ocean Circulation in the Toarcian (Early Jurassic): A Key Control on Deoxygenation and Carbon Burial on the European Shelf |journal=Paleoceanography and Paleoclimatology |volume=33 |issue=9 |pages=994–1012 |doi=10.1029/2018PA003394 |bibcode=2018PaPa...33..994R |s2cid=133780455 |doi-access=free }}</ref> The Panthalassan deep water site of Sakahogi was mainly anoxic-ferruginous across the interval spanning the late Pliensbachian to the TOAE, but transient sulphidic conditions did occur during the PTo-E and TOAE.<ref>{{cite journal |last1=Chen |first1=Wenhan |last2=Kemp |first2=David B. |last3=He |first3=Tianchen |last4=Newton |first4=Robert J. |last5=Xiong |first5=Yijun |last6=Jenkyns |first6=Hugh C. |last7=Izumi |first7=Kentaro |last8=Cho |first8=Tenichi |last9=Huang |first9=Chunju |last10=Poulton |first10=Simon W. |date=15 January 2023 |title=Shallow- and deep-ocean Fe cycling and redox evolution across the Pliensbachian–Toarcian boundary and Toarcian Oceanic Anoxic Event in Panthalassa |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X22005957 |journal=Earth and Planetary Science Letters |volume=602 |article-number=117959 |bibcode=2023E&PSL.60217959C |doi=10.1016/j.epsl.2022.117959 |s2cid=254963615 |archive-url=https://web.archive.org/web/20230515060611/https://www.sciencedirect.com/science/article/abs/pii/S0012821X22005957 |archive-date=15 May 2023 |access-date=14 May 2023 |url-status=bot: unknown |url-access=subscription }}</ref> In northeastern Panthalassa, in what is now British Columbia, euxinia dominated anoxic bottom waters.<ref>{{cite journal |last1=Kunert |first1=Alexandra |last2=Kendall |first2=Brian |date=13 February 2023 |title=Global ocean redox changes before and during the Toarcian Oceanic Anoxic Event |url=https://www.researchgate.net/publication/368472355 |journal=Nature Communications |volume=14 |issue=1 |page=815 |doi=10.1038/s41467-023-36516-x |pmid=36781894 |pmc=9925726 |bibcode=2023NatCo..14..815K |access-date=23 June 2023}}</ref>

The early stages of the TOAE were accompanied by a decrease in the acidity of seawater following a substantial decrease prior to the TOAE. Seawater pH then dropped close to the middle of the event, strongly acidifying the oceans.<ref name="BoronEvidenceOfOceanAcid">{{Cite journal |last1=Müller |first1=Tamás |last2=Jurikova |first2=Hana |last3=Gutjahr |first3=Marcus |last4=Tomašových |first4=Adam |last5=Schlögl |first5=Jan |last6=Liebetrau |first6=Volker |last7=Duarte |first7=Luís v. |last8=Milovský |first8=Rastislav |last9=Suan |first9=Guillaume |last10=Mattioli |first10=Emanuela |last11=Pittet |first11=Bernard |date=2020-12-01 |title=Ocean acidification during the early Toarcian extinction event: Evidence from boron isotopes in brachiopods |journal=Geology |language=en |volume=48 |issue=12 |pages=1184–1188 |bibcode=2020Geo....48.1184M |doi=10.1130/G47781.1 |issn=0091-7613 |doi-access=free|hdl=10023/20595 |hdl-access=free }}</ref> The sudden decline of carbonate production during the TOAE is widely believed to be the result of this abrupt episode of ocean acidification.<ref>{{cite journal |last1=Mattioli |first1=Emanuela |last2=Pittet |first2=Bernard |last3=Palliani |first3=Raffaella Bucefalo |last4=Röhl |first4=Hans-Joachim |last5=Schmid-Röhl |first5=Annette |last6=Morettini |first6=Elena |date=1 July 2004 |title=Phytoplankton evidence for the timing and correlation of palaeoceanographical changes during the early Toarcian oceanic anoxic event (Early Jurassic) |url=https://pubs.geoscienceworld.org/jgs/article-abstract/161/4/685/94337/Phytoplankton-evidence-for-the-timing-and |journal=Journal of the Geological Society |volume=161 |issue=4 |pages=685–693 |doi=10.1144/0016-764903-074 |bibcode=2004JGSoc.161..685M |s2cid=128901793 |access-date=29 March 2023|url-access=subscription }}</ref><ref>{{Cite journal |last1=Trecalli |first1=Alberto |last2=Spangenberg |first2=Jorge |last3=Adatte |first3=Thierry |last4=Föllmi |first4=Karl B. |last5=Parente |first5=Mariano |date=December 2012 |title=Carbonate platform evidence of ocean acidification at the onset of the early Toarcian oceanic anoxic event |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X12005390 |journal=Earth and Planetary Science Letters |language=en |volume=357-358 |pages=214–225 |bibcode=2012E&PSL.357..214T |doi=10.1016/j.epsl.2012.09.043|url-access=subscription }}</ref><ref>{{Cite journal |last1=Ettinger |first1=Nicholas P. |last2=Larson |first2=Toti E. |last3=Kerans |first3=Charles |last4=Thibodeau |first4=Alyson M. |last5=Hattori |first5=Kelly E. |last6=Kacur |first6=Sean M. |last7=Martindale |first7=Rowan C. |date=23 September 2020 |editor-last=Eberli |editor-first=Gregor |title=Ocean acidification and photic-zone anoxia at the Toarcian Oceanic Anoxic Event: Insights from the Adriatic Carbonate Platform |url=https://onlinelibrary.wiley.com/doi/10.1111/sed.12786 |journal=Sedimentology |language=en |volume=68 |pages=63–107 |doi=10.1111/sed.12786 |issn=0037-0746 |s2cid=224870464|url-access=subscription }}</ref> Additionally, the enhanced recycling of phosphorus back into seawater as a result of high temperatures and low seawater pH inhibited its mineralisation into apatite, helping contribute to oceanic anoxia. The abundance of phosphorus in marine environments created a positive feedback loop whose consequence was the further exacerbation of eutrophication and anoxia.<ref>{{cite journal |last1=Papadomanolaki |first1=Nina M. |last2=Lenstra |first2=Wytze K. |last3=Wolthers |first3=Mariette |last4=Slomp |first4=Caroline P. |author-link4=Caroline Slomp|date=1 July 2022 |title=Enhanced phosphorus recycling during past oceanic anoxia amplified by low rates of apatite authigenesis |journal=Science Advances |volume=8 |issue=26 |article-number=eabn2370 |bibcode=2022SciA....8N2370P |doi=10.1126/sciadv.abn2370 |pmid=35776794 |hdl=1874/421467 |s2cid=250218660|doi-access=free |pmc=10883373 |hdl-access=free }}</ref>

The extreme and rapid global warming at the start of the Toarcian promoted intensification of tropical storms across the globe.<ref>{{Cite journal |last1=Chen |first1=Wenhan |last2=Kemp |first2=David B. |last3=He |first3=Tianchen |last4=Huang |first4=Chunju |last5=Jin |first5=Simin |last6=Xiong |first6=Yijun |last7=Newton |first7=Robert J. |date=1 December 2021 |title=First record of the early Toarcian Oceanic Anoxic Event in the Hebrides Basin (UK) and implications for redox and weathering changes |url=https://www.sciencedirect.com/science/article/pii/S0921818121002708 |journal=Global and Planetary Change |volume=207 |article-number=103685 |doi=10.1016/j.gloplacha.2021.103685 |bibcode=2021GPC...20703685C |s2cid=240111632 |issn=0921-8181 |access-date=26 November 2023|url-access=subscription }}</ref><ref name=":0" /> Enhanced storm activity may have buffered the spread of oxygen-minimum zones in some regions by intensifying vertical water column mixing.<ref>{{Cite journal |last1=Ge |first1=Yuzhu |last2=Han |first2=Zhong |last3=Algeo |first3=Thomas J. |last4=Kemp |first4=David B. |last5=Wu |first5=Luya |date=November 2024 |title=Heterogeneous marine response during the Toarcian Oceanic Anoxic Event (TOAE): The potential role of storminess |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818124001802 |journal=Global and Planetary Change |language=en |volume=242 |article-number=104533 |doi=10.1016/j.gloplacha.2024.104533 |bibcode=2024GPC...24204533G |access-date=22 February 2025 |via=Elsevier Science Direct|url-access=subscription }}</ref>

== Effects on life ==

=== Marine invertebrates === The extinction event associated with the TOAE primarily affected marine life as a result the collapse of the carbonate factory.<ref>{{cite journal |last1=Krencker |first1=Francois-Nicolas |last2=Fantasia |first2=Alicia |last3=Danisch |first3=Jan |last4=Martindale |first4=Rowan |last5=Kabiri |first5=Lahcen |last6=El Ouali |first6=Mohamed |last7=Bodin |first7=Stéphane |title=Two-phased collapse of the shallow-water carbonate factory during the late Pliensbachian–Toarcian driven by changing climate and enhanced continental weathering in the Northwestern Gondwana Margin |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825220303007 |journal=Earth-Science Reviews |year=2020 |volume=208 |article-number=103254 |doi=10.1016/j.earscirev.2020.103254 |bibcode=2020ESRv..20803254K |s2cid=225669068 |access-date=17 December 2022|url-access=subscription }}</ref> Brachiopods were particularly severely hit,<ref>{{cite journal |last1=Danise |first1=Silvia |last2=Clémence |first2=Marie-Emilie |last3=Price |first3=Gregory D. |last4=Murphy |first4=Daniel P. |last5=Gómez |first5=Juan J. |last6=Twitchett |first6=Richard J. |date=15 June 2019 |title=Stratigraphic and environmental control on marine benthic community change through the early Toarcian extinction event (Iberian Range, Spain) |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018218309258 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=524 |pages=183–200 |bibcode=2019PPP...524..183D |doi=10.1016/j.palaeo.2019.03.039 |access-date=23 November 2022 |hdl=10026.1/13668 |s2cid=134835736|hdl-access=free |url-access=subscription }}</ref><ref name="PliensbachianToarcianExtinction">{{Cite journal |last1=Caruthers |first1=Andrew H. |last2=Smith |first2=Paul L. |last3=Gröcke |first3=Darren R. |date=September 2013 |title=The Pliensbachian–Toarcian (Early Jurassic) extinction, a global multi-phased event |url=https://linkinghub.elsevier.com/retrieve/pii/S0031018213002344 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=386 |pages=104–118 |bibcode=2013PPP...386..104C |doi=10.1016/j.palaeo.2013.05.010|url-access=subscription }}</ref><ref name="VörösKocsisPálfy2016">{{cite journal |last1=Vörös |first1=Attila |last2=Kocsis |first2=Ádám |last3=Pálfy |first3=József |date=1 September 2016 |title=Demise of the last two spire-bearing brachiopod orders (Spiriferinida and Athyridida) at the Toarcian (Early Jurassic) extinction event |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018216302140#! |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=457 |pages=233–241 |bibcode=2016PPP...457..233V |doi=10.1016/j.palaeo.2016.06.022 |access-date=29 October 2022|url-access=subscription }}</ref> with the TOAE representing one of the most dire crises in their evolutionary history.<ref name="JoranBaeza-CarrataláGoy2018">{{cite journal |last1=Joran |first1=Fernando García |last2=Baeza-Carratalá |first2=José Francisco |last3=Goy |first3=Antonio |date=1 October 2018 |title=Changes in brachiopod body size prior to the Early Toarcian (Jurassic) Mass Extinction |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018218304644#! |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=506 |pages=242–249 |bibcode=2018PPP...506..242G |doi=10.1016/j.palaeo.2018.06.045 |access-date=29 October 2022 |hdl=10045/77781 |s2cid=135368506|hdl-access=free }}</ref> Brachiopod taxa of large size declined significantly in abundance.<ref>{{cite journal |last1=Piazza |first1=Veronica |last2=Duarte |first2=Luís Vítor |last3=Renaudie |first3=Johan |last4=Aberhan |first4=Martin |date=29 March 2019 |title=Reductions in body size of benthic macroinvertebrates as a precursor of the early Toarcian (Early Jurassic) extinction event in the Lusitanian Basin, Portugal |journal=Paleobiology |volume=45 |issue=2 |pages=296–316 |doi=10.1017/pab.2019.11 |bibcode=2019Pbio...45..296P |s2cid=132593370 |doi-access=free }}</ref><ref>{{Cite journal |last1=Piazza |first1=Veronica |last2=Ullmann |first2=Clemens V. |last3=Aberhan |first3=Martin |date=13 March 2020 |title=Temperature-related body size change of marine benthic macroinvertebrates across the Early Toarcian Anoxic Event |journal=Scientific Reports |language=en |volume=10 |issue=1 |page=4675 |doi=10.1038/s41598-020-61393-5 |pmid=32170120 |issn=2045-2322 |pmc=7069967 |bibcode=2020NatSR..10.4675P }}</ref> Uniquely, the brachiopod genus ''Soaresirhynchia'' thrived during the later stages of the TOAE due to its low metabolic rate and slow rate of growth, making it a disaster taxon.<ref>{{cite journal |last1=Ullmann |first1=C. V. |last2=Boyle |first2=R. |last3=Duarte |first3=Luís Vítor |last4=Hesselbo |first4=Stephen P. |last5=Kasemann |first5=S. A. |last6=Klein |first6=T. |last7=Lenton |first7=T. M. |last8=Piazza |first8=Veronica |last9=Aberhan |first9=Martin |date=16 April 2020 |title=Warm afterglow from the Toarcian Oceanic Anoxic Event drives the success of deep-adapted brachiopods |journal=Scientific Reports |volume=10 |issue=1 |page=6549 |doi=10.1038/s41598-020-63487-6 |pmid=32300235 |pmc=7162941 |bibcode=2020NatSR..10.6549U }}</ref> The species ''S. bouchardi'' is known to have been a pioneer species that colonised areas denuded of brachiopods in the northwestern Tethyan region.<ref>{{cite journal |last1=García Joral |first1=Fernando |last2=Goy |first2=Antonio |last3=Rosales |first3=Idoia |last4=Barnolas |first4=Antonio |last5=Sevillano |first5=Ana |last6=López-García |first6=José María |date=5 September 2022 |title=Early Toarcian (Jurassic) brachiopods from the Balearic Islands (Spain) and their paleobiogeographic context |journal=Journal of Iberian Geology |volume=48 |issue=4 |pages=445–460 |doi=10.1007/s41513-022-00197-0 |s2cid=252072648 |doi-access=free |bibcode=2022JIbG...48..445G }}</ref> Ostracods also suffered a major diversity loss,<ref name="ZakharovEtAl2006" /><ref name="WignallAndBond2008">{{cite journal |last1=Wignall |first1=Paul B. |last2=Bond |first2=David P. G. |date=2008 |title=The end-Triassic and Early Jurassic mass extinction records in the British Isles |url=https://www.sciencedirect.com/science/article/abs/pii/S0016787808802593 |journal=Proceedings of the Geologists' Association |volume=119 |issue=1 |pages=73–84 |doi=10.1016/S0016-7878(08)80259-3 |bibcode=2008PrGA..119...73W |access-date=23 November 2022|url-access=subscription }}</ref> with almost all ostracod clades' distributions during the time interval corresponding to the ''serpentinum'' zone shifting towards higher latitudes to escape intolerably hot conditions near the Equator.<ref name="Arias2013">{{cite journal |last1=Arias |first1=Carmen |date=1 October 2013 |title=The early Toarcian (early Jurassic) ostracod extinction events in the Iberian Range: The effect of temperature changes and prolonged exposure to low dissolved oxygen concentrations |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018213003258 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=387 |pages=40–55 |bibcode=2013PPP...387...40A |doi=10.1016/j.palaeo.2013.07.004 |access-date=23 November 2022}}</ref> Bivalves likewise experienced a significant turnover.<ref name="WignallAndBond2008" /> The decline of bivalves exhibiting high endemism with narrow geographic ranges was particularly severe,<ref name="MassOriginationVersusMassExtinction">{{cite journal |last1=Aberhan |first1=M. |last2=Fürsich |first2=Franz T. |date=January 2000 |title=Mass origination versus mass extinction: the biological contribution to the Pliensbachian–Toarcian extinction event |url=https://www.lyellcollection.org/doi/abs/10.1144/jgs.157.1.55 |journal=Journal of the Geological Society |volume=157 |issue=1 |pages=55–60 |doi=10.1144/jgs.157.1.55 |bibcode=2000JGSoc.157...55A |s2cid=129652851 |access-date=14 May 2023|url-access=subscription }}</ref> as was the decline of bivalves with large, thick shells and high annual growth rates.<ref>{{Cite journal |last1=Posenato |first1=Renato |last2=Crippa |first2=Gaia |last3=De Winter |first3=Niels J. |last4=Claeys |first4=Philippe |last5=Goderis |first5=Steven |last6=Frijia |first6=Gianluca |last7=Brombin |first7=Valentina |date=1 September 2024 |title=Microstructures and sclerochronology of the Lithiotis Facies bivalves (Lower Jurassic): Paleobiological and paleoclimatic significance and their resilience to the early Toarcian extinction |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018224003183 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=649 |article-number=112329 |doi=10.1016/j.palaeo.2024.112329 |bibcode=2024PPP...64912329P |access-date=22 February 2025 |via=Elsevier Science Direct|url-access=subscription |hdl=1871.1/02a09c9b-02e8-47d9-9194-bfecad53eace |hdl-access=free }}</ref> At Ya Ha Tinda, a replacement of the pre-TOAE bivalve assemblage by a smaller, post-TOAE assemblage occurred,<ref>{{cite journal |last1=Martindale |first1=Rowan C. |last2=Aberhan |first2=Martin |date=15 July 2017 |title=Response of macrobenthic communities to the Toarcian Oceanic Anoxic Event in northeastern Panthalassa (Ya Ha Tinda, Alberta, Canada) |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018217300160 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=478 |pages=103–120 |doi=10.1016/j.palaeo.2017.01.009 |bibcode=2017PPP...478..103M |access-date=8 April 2023|url-access=subscription }}</ref> while in the Cleveland Basin, the inoceramid ''Pseudomytiloides dubius'' experienced the Lilliput effect.<ref>{{cite journal |last1=Morten |first1=Simon D. |last2=Twitchett |first2=Richard J. |date=20 December 2009 |title=Fluctuations in the body size of marine invertebrates through the Pliensbachian–Toarcian extinction event |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018209003472 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=284 |issue=1–2 |pages=29–38 |doi=10.1016/j.palaeo.2009.08.023 |bibcode=2009PPP...284...29M |access-date=14 June 2023|url-access=subscription }}</ref> Ammonoids, having already experienced a major morphological bottleneck thanks to the Gibbosus Event,<ref>{{cite journal |last1=Guex |first1=Jean |last2=Bartolini |first2=Annachiara |last3=Spangenberg |first3=Jorge E. |last4=Vicente |first4=J.-C. |last5=Schaltegger |first5=Urs |date=19 September 2012 |title=Ammonoid multi-extinction crises during the Late Pliensbachian - Toarcian and carbon cycle instabilities |url=https://www.researchgate.net/publication/258723336 |journal=Solid Earth |volume=4 |issue=2 |pages=1205–1228 |doi=10.5194/sed-4-1205-2012 |access-date=26 November 2023 |doi-access=free |bibcode=2012SolED...4.1205G }}</ref> about a million years before the Toarcian extinction, suffered further losses in the Early Toarcian diversity collapse.<ref>{{Cite journal |last1=Dera |first1=Guillaume |last2=Neige |first2=Pascal |last3=Dommergues |first3=Jean-Louis |last4=Fara |first4=Emmanuel |last5=Laffont |first5=Rémi |last6=Pellenard |first6=Pierre |date=January 2010 |title=High-resolution dynamics of Early Jurassic marine extinctions: the case of Pliensbachian–Toarcian ammonites (Cephalopoda) |url=http://jgs.lyellcollection.org/lookup/doi/10.1144/0016-76492009-068 |journal=Journal of the Geological Society |language=en |volume=167 |issue=1 |pages=21–33 |bibcode=2010JGSoc.167...21D |doi=10.1144/0016-76492009-068 |issn=0016-7649 |s2cid=128908746|url-access=subscription }}</ref> Belemnite richness in the northwestern Tethys dropped during the PTo-E but slightly increased across the TOAE.<ref name="DeBaetsEtAl2021">{{cite journal |last1=De Baets |first1=Kenneth |last2=Nätscher |first2=Paulina S. |last3=Rita |first3=Patricia |last4=Fara |first4=Emmanuel |last5=Neige |first5=Pascal |last6=Bardin |first6=Jérémie |last7=Dera |first7=Guillaume |last8=Duarte |first8=Luís Vítor |last9=Hughes |first9=Zoe |last10=Laschinger |first10=Peter |last11=García-Ramos |first11=José Carlos |last12=Piñuela |first12=Laura |last13=Übelacker |first13=Christof |last14=Weis |first14=Robert |date=20 December 2021 |title=The impact of the Pliensbachian–Toarcian crisis on belemnite assemblages and size distribution |journal=Swiss Journal of Palaeontology |volume=140 |issue=25 |pages=1–14 |article-number=25 |doi=10.1186/s13358-021-00242-y |hdl=10316/96856 |hdl-access=free |doi-access=free |bibcode=2021SwJP..140...25D }}</ref> Belemnites underwent a major change in habitat preference from cold, deep waters to warm, shallow waters.<ref name="BelemniteEcology" /> Their average rostrum size also increased, though this trend heavily varied depending on the lineage of belemnites.<ref name="DeBaetsEtAl2021" /> The Toarcian extinction was unbelievably catastrophic for corals; 90.9% of all Tethyan coral species and 49% of all genera were wiped out.<ref>{{cite journal |last1=Vasseur |first1=R. |last2=Lathuilière |first2=B. |last3=Lazăr |first3=I. |last4=Martindale |first4=Rowan C. |last5=Bodin |first5=S. |last6=Durlet |first6=C. |date=December 2021 |title=Major coral extinctions during the early Toarcian global warming event |journal=Global and Planetary Change |volume=207 |article-number=103647 |doi=10.1016/j.gloplacha.2021.103647 |bibcode=2021GPC...20703647V |s2cid=240513784 |doi-access=free }}</ref> Calcareous nannoplankton that lived in the deep photic zone suffered, with the decrease in abundance of the taxon ''Mitrolithus jansae'' used as an indicator of shoaling of the oxygen minimum zone in the Tethys and the Hispanic Corridor.<ref>{{Cite journal |last1=Reolid |first1=Matías |last2=Emanuela |first2=Mattioli |last3=Nieto |first3=Luis M. |last4=Rodríguez-Tovar |first4=Francisco J. |date=1 October 2014 |title=The Early Toarcian Oceanic Anoxic Event in the External Subbetic (Southiberian Palaeomargin, Westernmost Tethys): Geochemistry, nannofossils and ichnology |url=https://www.sciencedirect.com/science/article/pii/S0031018214003356 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=411 |pages=79–94 |doi=10.1016/j.palaeo.2014.06.023 |bibcode=2014PPP...411...79R |issn=0031-0182 |access-date=30 December 2023 |via=Elsevier Science Direct|url-access=subscription }}</ref> The biota of the Paris Basin suffered a particularly severe nannofossil crisis.<ref>{{Cite journal |last1=Clémence |first1=Marie-Emilie |last2=Gardin |first2=Silvia |last3=Bartolini |first3=Annachiara |date=1 June 2015 |title=New insights in the pattern and timing of the Early Jurassic calcareous nannofossil crisis |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018215001558 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=427 |pages=100–108 |doi=10.1016/j.palaeo.2015.03.024 |bibcode=2015PPP...427..100C |access-date=31 January 2025 |via=Elsevier Science Direct|url-access=subscription }}</ref> Other affected invertebrate groups included echinoderms,<ref name="ReolidDuarteRita2019">{{cite journal |last1=Reolid |first1=M. |last2=Duarte |first2=L. V. |last3=Rita |first3=P. |date=15 April 2019 |title=Changes in foraminiferal assemblages and environmental conditions during the T-OAE (Early Jurassic) in the northern Lusitanian Basin, Portugal |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018218308307 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=520 |pages=30–43 |doi=10.1016/j.palaeo.2019.01.022 |bibcode=2019PPP...520...30R |s2cid=135143670 |access-date=17 December 2022|url-access=subscription }}</ref> radiolarians,<ref>{{cite journal |last1=Goričan |first1=Špela |last2=Carter |first2=Elizabeth S. |last3=Guex |first3=Jean |last4=O'Dogherty |first4=Luis |last5=De Wever |first5=Patrick |last6=Dumitrica |first6=Paulian |last7=Hori |first7=Rie S. |last8=Matsuoka |first8=Atsushi |last9=Whalen |first9=Patricia A. |date=15 September 2013 |title=Evolutionary patterns and palaeobiogeography of Pliensbachian and Toarcian (Early Jurassic) Radiolaria |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018213003052 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=386 |pages=620–636 |doi=10.1016/j.palaeo.2013.06.028 |bibcode=2013PPP...386..620G |access-date=17 December 2022|url-access=subscription }}</ref> dinoflagellates,<ref name="ReolidDuarteRita2019" /> and foraminifera.<ref>{{cite journal |last1=Hess |first1=Silvia |last2=Nagy |first2=Jenő |last3=Laursen |first3=Gitte Vestergaard |date=28 January 2014 |title=Benthic foraminifera from the Lower Jurassic transgressive mudstones of the south-western Barents Sea—a possible high-latitude expression of the global Pliensbachian–Toarcian turnover? |journal=Polar Research |volume=33 |issue=1 |article-number=20206 |doi=10.3402/polar.v33.20206 |s2cid=128492520|doi-access=free |bibcode=2014PolRe..3320206H }}</ref><ref>{{cite journal |last1=Reolid |first1=Matías |last2=Copestake |first2=Philip |last3=Johnson |first3=Ben |date=15 October 2019 |title=Foraminiferal assemblages, extinctions and appearances associated with the Early Toarcian Oceanic Anoxic Event in the Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, United Kingdom |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018219303980 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=532 |article-number=109277 |bibcode=2019PPP...53209277R |doi=10.1016/j.palaeo.2019.109277 |access-date=23 November 2022 |s2cid=200072488|url-access=subscription }}</ref><ref name="ZakharovEtAl2006">{{cite journal |last1=Zakharov |first1=V. A. |last2=Shurygin |first2=B. N. |last3=Il'ina |first3=V. I. |last4=Nikitenko |first4=B. L. |date=July 2006 |title=Pliensbachian-Toarcian biotic turnover in north Siberia and the Arctic region |url=https://link.springer.com/article/10.1134/S0869593806040046?error=cookies_not_supported&code=d5ba4f95-176d-405e-8904-7d3cf0ec6db5 |journal=Stratigraphy and Geological Correlation |volume=14 |issue=4 |pages=399–417 |doi=10.1134/S0869593806040046 |bibcode=2006SGC....14..399Z |s2cid=129785254 |access-date=14 June 2023|url-access=subscription }}</ref> Trace fossils, an indicator of bioturbation and ecological diversity, became highly undiverse following the TOAE.<ref>{{cite journal |last1=Müller |first1=Tamás |last2=Karancz |first2=Szabina |last3=Mattioli |first3=Emanuela |last4=Milovský |first4=Rastislav |last5=Pálfy |first5=József |last6=Schlögl |first6=Jan |last7=Segit |first7=Tomasz |last8=Šimo |first8=Vladimír |last9=Tomašových |first9=Adam |date=December 2020 |title=Assessing anoxia, recovery and carbonate production setback in a hemipelagic Tethyan basin during the Toarcian Oceanic Anoxic Event (Western Carpathians) |journal=Global and Planetary Change |volume=195 |article-number=103366 |doi=10.1016/j.gloplacha.2020.103366 |bibcode=2020GPC...19503366M |s2cid=228834948 |doi-access=free }}</ref>

Carbonate platforms collapsed during both the PTo-E and the TOAE. Enhanced continental weathering and nutrient runoff was the dominant driver of carbonate platform decline in the PTo-E, while the biggest culprits during the TOAE were heightened storm activity and a decrease in the pH of seawater.<ref name="CarbonateFactoryCollapse">{{cite journal |last1=Krencker |first1=Francois-Nicolas |last2=Fantasia |first2=Alicia |last3=Danisch |first3=Jan |last4=Martindale |first4=Rowan |last5=Kabiri |first5=Lahcen |last6=El Ouali |first6=Mohamed |last7=Bodin |first7=Stéphane |date=September 2020 |title=Two-phased collapse of the shallow-water carbonate factory during the late Pliensbachian–Toarcian driven by changing climate and enhanced continental weathering in the Northwestern Gondwana Margin |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825220303007 |journal=Earth-Science Reviews |volume=208 |article-number=103254 |doi=10.1016/j.earscirev.2020.103254 |bibcode=2020ESRv..20803254K |s2cid=225669068 |access-date=14 May 2023|url-access=subscription }}</ref>

The recovery from the mass extinction among benthos commenced with the recolonisation of barren locales by opportunistic pioneer taxa. Benthic recovery was slow and sluggish, being regularly set back thanks to recurrent episodes of oxygen depletion, which continued for hundreds of thousands of years after the main extinction interval.<ref>{{cite journal |last1=Danise |first1=Silvia |last2=Twitchett |first2=Richard J. |last3=Little |first3=Crispin T. S. |last4=Clémence |first4=Marie-Emilie |date=14 February 2013 |title=The Impact of Global Warming and Anoxia on Marine Benthic Community Dynamics: an Example from the Toarcian (Early Jurassic) |journal=PLoS ONE |volume=8 |issue=2 |article-number=e56255 |doi=10.1371/journal.pone.0056255 |pmid=23457537 |pmc=3572952 |bibcode=2013PLoSO...856255D |doi-access=free }}</ref> Evidence from the Cleveland Basin suggests it took ~7 Myr for the marine benthos to recover, on par with the Permian-Triassic extinction event.<ref>{{Cite journal |last1=Atkinson |first1=Jed W. |last2=Little |first2=Crispin T. S. |last3=Dunhill |first3=Alexander M. |date=3 March 2023 |title=Long duration of benthic ecological recovery from the early Toarcian (Early Jurassic) mass extinction event in the Cleveland Basin, UK |journal=Journal of the Geological Society |language=en |volume=180 |issue=2 |article-number=jgs2022-126 |doi=10.1144/jgs2022-126 |bibcode=2023JGSoc.180..126A |issn=0016-7649 |doi-access=free }}</ref><ref>{{Cite journal |last1=Dunhill |first1=Alexander M. |last2=Zarzyczny |first2=Karolina |last3=Shaw |first3=Jack O. |last4=Atkinson |first4=Jed W. |last5=Little |first5=Crispin T. S. |last6=Beckerman |first6=Andrew P. |date=4 October 2024 |title=Extinction cascades, community collapse, and recovery across a Mesozoic hyperthermal event |journal=Nature Communications |language=en |volume=15 |issue=1 |page=8599 |doi=10.1038/s41467-024-53000-2 |issn=2041-1723 |pmc=11452722 |pmid=39366971 |bibcode=2024NatCo..15.8599D }}</ref> Many marine invertebrate taxa found in South America migrated through the Hispanic Corridor into European seas after the extinction event, aided in their dispersal by higher sea levels.<ref>{{cite journal |last1=Hallam |first1=A. |date=4 April 1996 |title=Recovery of the marine fauna in Europe after the end-Triassic and Early Toarcian mass Extinctions |url=https://www.lyellcollection.org/doi/abs/10.1144/GSL.SP.1996.001.01.16 |journal=Geological Society, London, Special Publications |volume=102 |issue=1 |pages=231–236 |doi=10.1144/GSL.SP.1996.001.01.16 |bibcode=1996GSLSP.102..231H |s2cid=128878485 |access-date=14 May 2023|url-access=subscription }}</ref>

=== Marine vertebrates === The TOAE had relatively minor effects on marine reptiles, in stark contrast to the major impact it had on many clades of marine invertebrates. In fact, in the Southwest German Basin, ichthyosaur diversity was higher after the extinction interval, although this may be in part a sampling artefact resulting from a sparse Pliensbachian marine vertebrate fossil record.<ref>{{Cite journal |last1=Maxwell |first1=Erin E. |last2=Vincent |first2=Peggy |date=2015-11-06 |title=Effects of the early Toarcian Oceanic Anoxic Event on ichthyosaur body size and faunal composition in the Southwest German Basin |journal=Paleobiology |volume=42 |issue=1 |pages=117–126 |doi=10.1017/pab.2015.34 |issn=0094-8373 |s2cid=131623205}}</ref> However, amidst the hyperthermal warmth of the latter half of the Toarcian in the TOAE's aftermath, plesiosaurids, microcleidids, leptonectids, temnodontosaurids, and basal parvipelvians vanished.<ref>{{Cite journal |last1=Reolid |first1=Matías |last2=Ruebsam |first2=Wolfgang |last3=Reolid |first3=Jesús |last4=Benton |first4=Michael J. |date=December 2024 |title=Impact of early Toarcian climatic changes on marine reptiles: Extinction and recovery |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825224002939 |journal=Earth-Science Reviews |language=en |volume=259 |article-number=104965 |doi=10.1016/j.earscirev.2024.104965 |bibcode=2024ESRv..25904965R |access-date=31 January 2025 |via=Elsevier Science Direct|url-access=subscription }}</ref> Thalattosuchians appear to have rapidly radiated after the TOAE.<ref>{{cite thesis |last1=Breeden |first1=Benjamin Thomas |date=August 2022 |title=Reptile Diversification in the Aftermath of the Toarcian Ocean Anoxic Event: Evidence from Southern Japan |url=https://www.proquest.com/docview/2774892594 |degree=PhD |publisher=University of Utah Department of Geology and Geophysics |access-date=31 January 2025 |id={{ProQuest|2774892594}} }}</ref>

=== Terrestrial animals === The TOAE is suggested to have caused the extinction of various clades of dinosaurs, including coelophysids, dilophosaurids, and many basal sauropodomorph clades, as a consequence of the remodelling of terrestrial ecosystems caused by global climate change.<ref name="JenkynsDinosaurs" /> Some heterodontosaurids and thyreophorans also perished in the extinction event.<ref>{{cite journal |last1=Reolid |first1=Matias |last2=Ruebsam |first2=Wolfgang |last3=Benton |first3=Michael James |date=22 December 2022 |title=Dinosaur extinctions related to the Jenkyns Event (early Toarcian, Jurassic) |url=https://revistas.uv.es/index.php/sjpalaeontology/article/view/25683 |journal=Spanish Journal of Palaeontology |volume=37 |issue=2 |pages=123–140 |doi=10.7203/sjp.25683 |s2cid=255022626 |access-date=2 April 2023|doi-access=free }}</ref> In the wake of the extinction event, many derived clades of ornithischians, sauropods, and theropods emerged, with most of these post-extinction clades greatly increasing in size relative to dinosaurs before the TOAE.<ref name="JenkynsDinosaurs">{{cite journal |last1=Reolid |first1=M. |last2=Ruebsam |first2=W. |last3=Benton |first3=Michael James |date=November 2022 |title=Impact of the Jenkyns Event (early Toarcian) on dinosaurs: Comparison with the Triassic/Jurassic transition |journal=Earth-Science Reviews |volume=234 |article-number=104196 |doi=10.1016/j.earscirev.2022.104196 |bibcode=2022ESRv..23404196R |s2cid=252608726 |doi-access=free }}</ref> Eusauropods were propelled to ecological dominance after their survival of the Toarcian cataclysm.<ref>{{Cite journal |last1=Pol |first1=D. |last2=Ramezani |first2=J. |last3=Gomez |first3=K. |last4=Carballido |first4=J. L. |last5=Carabajal |first5=A. Paulina |last6=Rauhut |first6=O. W. M. |last7=Escapa |first7=I. H. |last8=Cúneo |first8=N. R. |date=25 November 2020 |title=Extinction of herbivorous dinosaurs linked to Early Jurassic global warming event |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=287 |issue=1939 |article-number=20202310 |doi=10.1098/rspb.2020.2310 |issn=0962-8452 |pmc=7739499 |pmid=33203331 |bibcode=2020PBioS.28702310P }}</ref> Megalosaurids experienced a diversification event in the latter part of the Toarcian that was possibly a post-extinction radiation that filled niches vacated by the mass death of the Early Toarcian extinction.<ref name="TheWorstOfTimes">{{cite book |last1=Wignall |first1=Paul B. |date=29 September 2015 |title=The Worst of Times: How Life on Earth Survived Eighty Million Years of Mass Extinctions |chapter=Pangea's Final Blow |location=Princeton |publisher=Princeton University Press |pages=137–153 |isbn=978-0-691-14209-8}}</ref> Insects may have experienced blooms as fish moved en masse to surface waters to escape anoxia and then died in droves due to limited resources.<ref>{{Cite journal |last1=Swaby |first1=Emily J. |last2=Coe |first2=Angela L. |last3=Ansorge |first3=Jörg |last4=Caswell |first4=Bryony A. |last5=Hayward |first5=Scott A. L. |last6=Mander |first6=Luke |last7=Stevens |first7=Liadan G. |last8=McArdle |first8=Aimee |date=17 April 2024 |editor-last=Thuy |editor-first=Ben |title=The fossil insect assemblage associated with the Toarcian (Lower Jurassic) oceanic anoxic event from Alderton Hill, Gloucestershire, UK |journal=PLOS ONE |language=en |volume=19 |issue=4 |article-number=e0299551 |doi=10.1371/journal.pone.0299551 |doi-access=free |issn=1932-6203 |pmc=11023202 |pmid=38630753 |bibcode=2024PLoSO..1999551S }}</ref>

=== Terrestrial plants === The volcanogenic extinction event initially impacted terrestrial ecosystems more severely than marine ones. A shift towards a low diversity assemblage of cheirolepid conifers, cycads, and ''Cerebropollenites''-producers adapted for high aridity from a higher diversity ecological assemblage of lycophytes, conifers, seed ferns, and wet-adapted ferns is observed in the palaeobotanical and palynological record over the course of the TOAE.<ref name="SlaterTwitchettDaniseVajda2019" /> The coincidence of the zenith of ''Classopolis'' and the decline of seed ferns and spore producing plants with increased mercury loading implicates heavy metal poisoning as a key contributor to the floristic crisis during the Toarcian mass extinction.<ref>{{cite journal |last1=Jin |first1=Xin |last2=Zhang |first2=Fei |last3=Baranyi |first3=Viktória |last4=Kemp |first4=David B. |last5=Feng |first5=Xinbin |last6=Grasby |first6=Stephen E. |last7=Sun |first7=Guangyi |last8=Shi |first8=Zhiqiang |last9=Chen |first9=Wenhan |last10=Dal Corso |first10=Jacopo |date=15 November 2022 |title=Early Jurassic massive release of terrestrial mercury linked to floral crisis |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X22004782 |journal=Earth and Planetary Science Letters |volume=598 |article-number=117842 |doi=10.1016/j.epsl.2022.117842 |bibcode=2022E&PSL.59817842J |s2cid=252794071 |access-date=14 June 2023|url-access=subscription }}</ref> Poisoning by mercury, along with chromium, copper, cadmium, arsenic, and lead is speculated to be responsible for heightened rates of spore malformation and dwarfism concomitant with enrichments in all these toxic metals.<ref>{{cite journal |last1=Baranyi |first1=Viktória |last2=Jin |first2=Xin |last3=Dal Corso |first3=Jacopo |last4=Shi |first4=Zhiqiang |last5=Grasby |first5=Stephen E. |last6=Kemp |first6=David B. |date=8 May 2023 |title=Collapse of terrestrial ecosystems linked to heavy metal poisoning during the Toarcian oceanic anoxic event |url=https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51037.1/623294/Collapse-of-terrestrial-ecosystems-linked-to-heavy |journal=Geology |volume=51 |issue=7 |pages=652–656 |doi=10.1130/G51037.1 |bibcode=2023Geo....51..652B |s2cid=258580509 |access-date=14 June 2023|url-access=subscription }}</ref>

== Geologic effects == The TOAE was associated with widespread phosphatisation of marine fossils believed to result from the warming-induced increase in weathering that increased phosphate flux into the ocean. This produced exquisitely preserved lagerstätten across the world, such as Ya Ha Tinda, Strawberry Bank, and the Posidonia Shale.<ref>{{cite journal |last1=Sinha |first1=Sinjini |last2=Muscente |first2=A. D. |last3=Schiffbauer |first3=James D. |last4=Williams |first4=Matt |last5=Schweigert |first5=Günter |last6=Martindale |first6=Rowan C. |date=16 December 2021 |title=Global controls on phosphatization of fossils during the Toarcian Oceanic Anoxic Event |url=https://www.researchgate.net/publication/357093726 |journal=Scientific Reports |volume=11 |issue=1 |page=24087 |doi=10.1038/s41598-021-03482-7 |pmid=34916533 |pmc=8677819 |bibcode=2021NatSR..1124087S |access-date=17 July 2023}}</ref>

As is common during anoxic events, black shale deposition was widespread during the deoxygenation events of the Toarcian.<ref>{{cite journal |last1=Lézin |first1=Carine |last2=Andreu |first2=Bernard |last3=Pellenard |first3=Pierre |last4=Buchez |first4=Jean-Luc |last5=Emmanuel |first5=Laurent |last6=Fauré |first6=Philippe |last7=Landrein |first7=Philippe |date=11 March 2013 |title=Geochemical disturbance and paleoenvironmental changes during the Early Toarcian in NW Europe |url=https://www.sciencedirect.com/science/article/abs/pii/S0009254113000314 |journal=Chemical Geology |volume=341 |pages=1–15 |doi=10.1016/j.chemgeo.2013.01.003 |bibcode=2013ChGeo.341....1L |access-date=17 December 2022|url-access=subscription }}</ref><ref name="BeaujolaisBlackShales">{{cite journal |last1=Suan |first1=Guillaume |last2=Rulleau |first2=Louis |last3=Mattioli |first3=Emanuela |last4=Suchéras-Marx |first4=Baptiste |last5=Rouselle |first5=Bruno |last6=Pittet |first6=Bernard |last7=Vincent |first7=Peggy |last8=Martin |first8=Jeremy E. |last9=Léna |first9=Alex |last10=Spangenberg |first10=Jorge E. |last11=Föllmi |first11=Karl B. |date=7 February 2013 |title=Palaeoenvironmental significance of Toarcian black shales and event deposits from southern Beaujolais, France |url=https://www.cambridge.org/core/journals/geological-magazine/article/abs/palaeoenvironmental-significance-of-toarcian-black-shales-and-event-deposits-from-southern-beaujolais-france/790F9CA08A69DE03518736FDE7F5C9BB |journal=Geological Magazine |volume=150 |issue=4 |pages=728–742 |doi=10.1017/S0016756812000970 |bibcode=2013GeoM..150..728S |s2cid=53574804 |access-date=13 March 2023}}</ref><ref>{{cite journal |last1=Fernández-Martínez |first1=Javier |last2=Rodríguez-Tovar |first2=Francisco J. |last3=Piñuela |first3=Laura |last4=Martínez-Ruiz |first4=Francisca |last5=García-Ramos |first5=José C. |date=15 June 2021 |title=Bottom- and pore-water oxygenation during the early Toarcian Oceanic Anoxic Event (T-OAE) in the Asturian Basin (N Spain): Ichnological information to improve facies analysis |url=https://www.sciencedirect.com/science/article/abs/pii/S0037073821000610 |journal=Sedimentary Geology |volume=419 |article-number=105909 |doi=10.1016/j.sedgeo.2021.105909 |bibcode=2021SedG..41905909F |s2cid=234855326 |access-date=2 April 2023|url-access=subscription }}</ref> Toarcian anoxia was responsible for the deposition of commercially extracted oil shales,<ref>{{cite journal |last1=Jones |first1=Charles E. |last2=Jenkyns |first2=Hugh C. |date=February 2001 |title=Seawater Strontium Isotopes, Oceanic Anoxic Events, and Seafloor Hydrothermal Activity in the Jurassic and Cretaceous |url=https://www.ajsonline.org/content/301/2/112.short |journal=American Journal of Science |volume=301 |issue=2 |pages=112–149 |doi=10.2475/ajs.301.2.112 |bibcode=2001AmJS..301..112J |s2cid=123838 |access-date=8 April 2023|url-access=subscription }}</ref> particularly in China.<ref>{{cite journal |last1=Yi |first1=Fan |last2=Yi |first2=Haisheng |last3=Xia |first3=Guoqing |last4=Wu |first4=Chihua |last5=Li |first5=Gaojie |last6=Cai |first6=Zhanhu |last7=Li |first7=Na |date=November 2021 |title=Factors controlling the organic matter accumulation across the Pliensbachian-Toarcian transition in the Qiangtang Basin, Tibetan Plateau |url=https://www.sciencedirect.com/science/article/abs/pii/S0264817221004074 |journal=Marine and Petroleum Geology |volume=133 |article-number=105304 |doi=10.1016/j.marpetgeo.2021.105304 |bibcode=2021MarPG.13305304Y |access-date=8 January 2023|url-access=subscription }}</ref><ref>{{cite journal |last1=Qiu |first1=Zhen |last2=He |first2=Jianglin |date=1 July 2022 |title=Depositional environment changes and organic matter accumulation of Pliensbachian-Toarcian lacustrine shales in the Sichuan basin, SW China |url=https://www.sciencedirect.com/science/article/abs/pii/S1367912021003734 |journal=Journal of Asian Earth Sciences |volume=232 |article-number=105035 |doi=10.1016/j.jseaes.2021.105035 |bibcode=2022JAESc.23205035Q |s2cid=245038615 |access-date=5 August 2023|url-access=subscription }}</ref>

Enhanced hydrological cycling caused clastic sedimentation to accelerate during the TOAE; the increase in clastic sedimentation was synchronous with excursions in ¹⁸⁷Os/¹⁸⁸Os, ⁸⁷Sr/⁸⁶Sr, and δ^44/40Ca.<ref>{{Cite journal |last1=Xu |first1=Weimu |last2=Ruhl |first2=Micha |last3=Jenkyns |first3=Hugh C. |last4=Leng |first4=Melanie J. |last5=Huggett |first5=Jennifer M. |last6=Minisini |first6=Daniel |last7=Ullmann |first7=Clemens V. |last8=Riding |first8=James B. |last9=Weijers |first9=Johan W. H. |last10=Storm |first10=Marisa S. |last11=Percival |first11=Lawrence M. E. |last12=Tosca |first12=Nicholas J. |last13=Idiz |first13=Erdem F. |last14=Tegelaar |first14=Erik W. |last15=Hesselbo |first15=Stephen P. |date=15 February 2018 |title=Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK) |journal=Earth and Planetary Science Letters |volume=484 |pages=396–411 |doi=10.1016/j.epsl.2017.12.037 |s2cid=55022954 |issn=0012-821X |doi-access=free |bibcode=2018E&PSL.484..396X |hdl=10871/30888 |hdl-access=free }}</ref>

Additionally, the Toarcian was punctuated by intervals of extensive kaolinite enrichment.<ref>{{cite journal |last1=Fantasia |first1=Alicia |last2=Adatte |first2=Thierry |last3=Spangenberg |first3=Jorge E. |last4=Font |first4=Eric |last5=Duarte |first5=Luís V. |last6=Föllmi |first6=Karl B. |date=November 2019 |title=Global versus local processes during the Pliensbachian–Toarcian transition at the Peniche GSSP, Portugal: A multi-proxy record |url=https://www.sciencedirect.com/science/article/abs/pii/S0012825219303289 |journal=Earth-Science Reviews |volume=198 |article-number=102932 |bibcode=2019ESRv..19802932F |doi=10.1016/j.earscirev.2019.102932 |s2cid=202179439 |access-date=29 March 2023|url-access=subscription }}</ref> These kaolinites correspond to negative oxygen isotope excursions and high Mg/Ca ratios and are thus reflective of climatic warming events that characterised much of the Toarcian.<ref>{{cite journal |last1=Dera |first1=Guillaume |last2=Pellenard |first2=Pierre |last3=Neige |first3=Pascal |last4=Deconinck |first4=Jean-François |last5=Pucéat |first5=Emmanuelle |last6=Dommergues |first6=Jean-Louis |date=1 January 2009 |title=Distribution of clay minerals in Early Jurassic Peritethyan seas: Palaeoclimatic significance inferred from multiproxy comparisons |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018208005269 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=271 |issue=1–2 |pages=39–51 |doi=10.1016/j.palaeo.2008.09.010 |bibcode=2009PPP...271...39D |access-date=17 July 2023|url-access=subscription }}</ref> Likewise, illitic/smectitic clays were also common during this hyperthermal perturbation.<ref>{{cite journal |last1=Müller |first1=Tamás |last2=Price |first2=Gregory D. |last3=Bajnai |first3=Dávid |last4=Nyerges |first4=Anita |last5=Kesjár |first5=Dóra |last6=Raucsik |first6=Béla |last7=Varga |first7=Andrea |last8=Judik |first8=Katalin |last9=Fekete |first9=József |last10=May |first10=Zoltán |last11=Pálfy |first11=József |date=7 October 2016 |title=New multiproxy record of the Jenkyns Event (also known as the Toarcian Oceanic Anoxic Event) from the Mecsek Mountains (Hungary): Differences, duration and drivers |url=https://onlinelibrary.wiley.com/doi/abs/10.1111/sed.12332 |journal=Sedimentology |volume=64 |issue=1 |pages=66–86 |doi=10.1111/sed.12332 |s2cid=133481660 |access-date=8 April 2023|hdl=10026.1/8649 |hdl-access=free |url-access=subscription }}</ref>

== Palaeogeographic changes == The Intertropical Convergence Zone (ITCZ) migrated southwards across southern Gondwana, turning much of the region more arid. This aridification was interrupted, however, in the ''spinatus'' ammonite biozone and across the Pliensbachian-Toarcian boundary itself.<ref name="FantasiaEtAl2018">{{cite journal |last1=Fantasia |first1=Alicia |last2=Föllmi |first2=Karl B. |last3=Adatte |first3=Thierry |last4=Bernárdez |first4=Enrique |last5=Spangenberg |first5=Jorge E. |last6=Mattioli |first6=Emanuela |date=10 August 2018 |title=The Toarcian Oceanic Anoxic Event in southwestern Gondwana: an example from the Andean Basin, northern Chile |url=https://pubs.geoscienceworld.org/jgs/article-abstract/175/6/883/536768/The-Toarcian-Oceanic-Anoxic-Event-in-southwestern |journal=Journal of the Geological Society |volume=175 |issue=6 |pages=883–902 |bibcode=2018JGSoc.175..883F |doi=10.1144/jgs2018-008 |s2cid=134669817 |access-date=29 March 2023|url-access=subscription }}</ref>

The large rise in sea levels resulting from the intense global warming led to the formation of the Laurasian Seaway, which enabled the flow of cool water low in salt content to flow into the Tethys Ocean from the Arctic Ocean. The opening of this seaway may have potentially acted as a mitigating factor that ameliorated to a degree the oppressively anoxic conditions that were widespread across much of the Tethys.<ref>{{cite journal |last1=Mattioli |first1=Emanuela |last2=Pittet |first2=Bernard |last3=Suan |first3=Guillaume |last4=Mailliot |first4=Samuel |date=23 July 2008 |title=Calcareous nannoplankton changes across the early Toarcian oceanic anoxic event in the western Tethys |journal=Paleoceanography and Paleoclimatology |volume=23 |issue=3 |pages=1–17 |article-number=2007PA001435 |doi=10.1029/2007PA001435 |bibcode=2008PalOc..23.3208M |doi-access=free }}</ref>

The enhanced hydrological cycle during early Toarcian warming caused lakes to grow in size.<ref name="OrdosBasin">{{cite journal |last1=Jin |first1=Xin |last2=Shi |first2=Zhiqiang |last3=Baranyi |first3=Viktória |last4=Kemp |first4=David B. |last5=Han |first5=Zhong |last6=Luo |first6=Genming |last7=Hu |first7=Jianfang |last8=He |first8=Feng |last9=Chen |first9=Lan |last10=Preto |first10=Nereo |date=October 2020 |title=The Jenkyns Event (early Toarcian OAE) in the Ordos Basin, North China |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818120301648 |journal=Global and Planetary Change |volume=193 |article-number=103273 |doi=10.1016/j.gloplacha.2020.103273 |bibcode=2020GPC...19303273J |s2cid=224876498 |access-date=14 May 2023|url-access=subscription }}</ref> During the anoxic event, the Sichuan Basin was transformed into a giant lake,<ref>{{cite journal |last1=Liu |first1=Jinchao |last2=Cao |first2=Jian |last3=He |first3=Tianchen |last4=Liang |first4=Feng |last5=Pu |first5=Jing |last6=Wang |first6=Yan |date=August 2022 |title=Lacustrine redox variations in the Toarcian Sichuan Basin across the Jenkyns Event |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818122001278 |journal=Global and Planetary Change |volume=215 |article-number=103860 |bibcode=2022GPC...21503860L |doi=10.1016/j.gloplacha.2022.103860 |s2cid=249558555 |archive-url=https://web.archive.org/web/20221218090004/https://www.sciencedirect.com/science/article/abs/pii/S0921818122001278 |archive-date=18 December 2022 |access-date=17 December 2022 |url-status=bot: unknown |url-access=subscription }}</ref><ref>{{cite journal |last1=Xu |first1=Weimu |last2=Weijers |first2=Johan W. H. |last3=Ruhl |first3=Micha |last4=Idiz |first4=Erdem F. |last5=Jenkyns |first5=Hugh C. |last6=Riding |first6=James B. |last7=Gorbanenko |first7=Olga |last8=Hesselbo |first8=Stephen P. |date=2 July 2021 |title=Molecular and petrographical evidence for lacustrine environmental and biotic change in the palaeo-Sichuan mega-lake (China) during the Toarcian Oceanic Anoxic Event |url=https://www.lyellcollection.org/doi/abs/10.1144/SP514-2021-2 |journal=Geological Society Special Publications |volume=514 |issue=1 |pages=335–357 |doi=10.1144/SP514-2021-2 |bibcode=2021GSLSP.514..335X |s2cid=236377708 |access-date=2 April 2023}}</ref> which was believed to be approximately thrice as large as modern-day Lake Superior.<ref name="ExpandedLakeSystem" /> Lacustrine sediments deposited as a result of this lake's existence are represented by the Da'anzhai Member of the Ziliujing Formation.<ref>{{cite journal |last1=Liu |first1=Renping |last2=Hu |first2=Guang |last3=Cao |first3=Jian |last4=Yang |first4=Ruofei |last5=Liao |first5=Zhiwei |last6=Hu |first6=Chaowei |last7=Pang |first7=Qian |last8=Pang |first8=Peng |date=September 2022 |title=Enhanced hydrological cycling and continental weathering during the Jenkyns Event in a lake system in the Sichuan Basin, China |url=https://www.sciencedirect.com/science/article/abs/pii/S0921818122001825 |journal=Global and Planetary Change |volume=216 |article-number=103915 |doi=10.1016/j.gloplacha.2022.103915 |bibcode=2022GPC...21603915L |s2cid=251560158 |access-date=16 August 2023|url-access=subscription }}</ref> Roughly ~460 gigatons (Gt) of organic carbon and ~1,200 Gt of inorganic carbon were likely sequestered by this lake over the course of the TOAE.<ref name="ExpandedLakeSystem">{{Cite journal |last1=Xu |first1=Weimu |last2=Ruhl |first2=Micha |last3=Jenkyns |first3=Hugh C. |last4=Hesselbo |first4=Stephen P. |last5=Riding |first5=James B. |last6=Selby |first6=David |last7=Naafs |first7=B. David A. |last8=Weijers |first8=Johan W. H. |last9=Pancost |first9=Richard D. |last10=Tegelaar |first10=Erik W. |last11=Idiz |first11=Erdem F. |date=February 2017 |title=Carbon sequestration in an expanded lake system during the Toarcian oceanic anoxic event |url=http://www.nature.com/articles/ngeo2871 |journal=Nature Geoscience |language=en |volume=10 |issue=2 |pages=129–134 |bibcode=2017NatGe..10..129X |doi=10.1038/ngeo2871 |issn=1752-0894|hdl=10871/24965 |hdl-access=free }}</ref>

== Comparison with present global warming ==

The TOAE and the Palaeocene-Eocene Thermal Maximum have been proposed as analogues to modern anthropogenic global warming based on the comparable quantity of greenhouse gases released into the atmosphere in all three events.<ref name="Cohen2007" /> Some researchers argue that evidence for a major increase in Tethyan tropical cyclone intensity during the TOAE suggests that a similar increase in magnitude of tropical storms is bound to occur as a consequence of present climate change.<ref name=":0">{{cite journal |last1=Krencker |first1=François-Nicolas |last2=Bodin |first2=Stéphane |last3=Suan |first3=Guillaume |last4=Heimhofer |first4=Ulrich |last5=Kabiri |first5=Lahcen |last6=Immenhauser |first6=Adrian |date=1 September 2015 |title=Toarcian extreme warmth led to tropical cyclone intensification |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X15003532 |journal=Earth and Planetary Science Letters |volume=425 |pages=120–130 |doi=10.1016/j.epsl.2015.06.003 |bibcode=2015E&PSL.425..120K |access-date=20 January 2023|url-access=subscription }}</ref>

== See also ==

* Weissert Event * Selli Event * Bonarelli Event

== References == {{reflist}}

Category:Extinction events Category:Toarcian Stage Category:Isotope excursions