# Weissert Event
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{{Short description|Hyperthermal event during the Early Cretaceous epoch}}
The '''Weissert Event''', also referred to as the '''Weissert Thermal Excursion''' ('''WTX'''),[{{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=1 April 2021 |title=Phanerozoic paleotemperatures: The earth's changing climate during the last 540 million years |url=https://www.sciencedirect.com/science/article/pii/S0012825221000027 |journal=[Earth-Science Reviews](/source/Earth-Science_Reviews) |volume=215 |article-number=103503 |doi=10.1016/j.earscirev.2021.103503 |bibcode=2021ESRv..21503503S |s2cid=233579194 |issn=0012-8252 |access-date=5 November 2023|url-access=subscription }}] was a [hyperthermal event](/source/hyperthermal_event) that occurred in the [Valanginian](/source/Valanginian) [stage](/source/stage_(geology)) of the [Early Cretaceous](/source/Early_Cretaceous) epoch.[{{Cite journal |last1=Martinez |first1=Mathieu |last2=Aguirre-Urreta |first2=Beatriz |last3=Dera |first3=Guillaume |last4=Lescano |first4=Marina |last5=Omarini |first5=Julieta |last6=Tunik |first6=Maisa |last7=O'Dogherty |first7=Luis |last8=Aguado |first8=Roque |last9=Company |first9=Miguel |last10=Bodin |first10=Stéphane |date=1 April 2023 |title=Synchrony of carbon cycle fluctuations, volcanism and orbital forcing during the Early Cretaceous |url=https://www.sciencedirect.com/science/article/pii/S0012825223000454 |journal=[Earth-Science Reviews](/source/Earth-Science_Reviews) |volume=239 |article-number=104356 |doi=10.1016/j.earscirev.2023.104356 |bibcode=2023ESRv..23904356M |s2cid=256880421 |issn=0012-8252 |access-date=5 November 2023}}] However, astrochronological studies of sediments in the Vocontian Basin have yielded a duration of 2.08 Myr, with the positive δ13C excursion being 0.94 Myr in duration and the δ13C plateau being 1.14 Myr.[{{Cite journal |last1=Charbonnier |first1=Guillaume |last2=Boulila |first2=Slah |last3=Gardin |first3=Silvia |last4=Duchamp-Alphonse |first4=Stéphanie |last5=Adatte |first5=Thierry |last6=Spangenberg |first6=Jorge E. |last7=Föllmi |first7=Karl B. |last8=Colin |first8=Christophe |last9=Galbrun |first9=Bruno |date=1 October 2013 |title=Astronomical calibration of the Valanginian "Weissert" episode: The Orpierre marl–limestone succession (Vocontian Basin, southeastern France) |url=https://www.sciencedirect.com/science/article/pii/S0195667113001122 |journal=[Cretaceous Research](/source/Cretaceous_Research) |volume=45 |pages=25–42 |doi=10.1016/j.cretres.2013.07.003 |bibcode=2013CrRes..45...25C |issn=0195-6671 |access-date=5 November 2023|url-access=subscription }}] A different study concludes the WTX lasted for about 1.4 million years (Myr) based on the chronological length of the high δ13C plateau observed over its course in the Bersek Marl Formation of [Hungary](/source/Hungary).[{{Cite journal |last1=Bajnai |first1=Dávid |last2=Pálfy |first2=József |last3=Martinez |first3=Mathieu |last4=Price |first4=Gregory D. |last5=Nyerges |first5=Anita |last6=Főzy |first6=István |date=1 July 2017 |title=Multi-proxy record of orbital-scale changes in climate and sedimentation during the Weissert Event in the Valanginian Bersek Marl Formation (Gerecse Mts., Hungary) |url=https://www.sciencedirect.com/science/article/pii/S0195667116302221 |journal=[Cretaceous Research](/source/Cretaceous_Research) |volume=75 |pages=45–60 |doi=10.1016/j.cretres.2017.02.021 |bibcode=2017CrRes..75...45B |issn=0195-6671 |access-date=5 November 2023|hdl=10026.1/8696 |hdl-access=free }}]
== Causes ==
An addition of [carbon dioxide into the atmosphere](/source/Carbon_dioxide_in_Earth's_atmosphere) via the activity of the [Paraná-Etendeka Large Igneous Province](/source/Paran%C3%A1_and_Etendeka_traps) (PE-LIP) is generally accepted as the leading candidate for what sparked the WTX,[{{Cite journal |last1=Martinez |first1=Mathieu |last2=Deconinck |first2=Jean-François |last3=Pellenard |first3=Pierre |last4=Riquier |first4=Laurent |last5=Company |first5=Miguel |last6=Reboulet |first6=Stéphane |last7=Moiroud |first7=Mathieu |date=1 August 2015 |title=Astrochronology of the Valanginian–Hauterivian stages (Early Cretaceous): Chronological relationships between the Paraná–Etendeka large igneous province and the Weissert and the Faraoni events |url=https://www.sciencedirect.com/science/article/pii/S0921818115001113 |journal=[Global and Planetary Change](/source/Global_and_Planetary_Change) |volume=131 |pages=158–173 |doi=10.1016/j.gloplacha.2015.06.001 |bibcode=2015GPC...131..158M |issn=0921-8181 |access-date=5 November 2023|url-access=subscription }}] although this is not universally accepted, with some reconstructed geochronologies showing a lack of causality between the emplacement of the PE-LIP and the onset of the WTX.[{{Cite journal |last1=Martinez |first1=Mathieu |last2=Deconinck |first2=Jean-François |last3=Pellenard |first3=Pierre |last4=Reboulet |first4=Stéphane |last5=Riquier |first5=Laurent |date=15 April 2013 |title=Astrochronology of the Valanginian Stage from reference sections (Vocontian Basin, France) and palaeoenvironmental implications for the Weissert Event |url=https://www.sciencedirect.com/science/article/pii/S0031018213000977 |journal=[Palaeogeography, Palaeoclimatology, Palaeoecology](/source/Palaeogeography%2C_Palaeoclimatology%2C_Palaeoecology) |volume=376 |pages=91–102 |doi=10.1016/j.palaeo.2013.02.021 |bibcode=2013PPP...376...91M |issn=0031-0182 |access-date=5 November 2023|url-access=subscription }}] The prolonged, drawn out manner in which the PE-LIP erupted has been brought up as a further argument against its emplacement as the driving perturbation causing the WTX.[{{Cite journal |last1=Price |first1=Gregory D. |last2=Janssen |first2=Nico M. M. |last3=Martinez |first3=Mathieu |last4=Company |first4=Miguel |last5=Vandevelde |first5=Justin H. |last6=Grimes |first6=Stephen T. |date=8 October 2018 |title=A High-Resolution Belemnite Geochemical Analysis of Early Cretaceous (Valanginian-Hauterivian) Environmental and Climatic Perturbations |journal=[Geochemistry, Geophysics, Geosystems](/source/Geochemistry%2C_Geophysics%2C_Geosystems) |language=en |volume=19 |issue=10 |pages=3832–3843 |doi=10.1029/2018GC007676 |issn=1525-2027 |doi-access=free |bibcode=2018GGG....19.3832P |hdl=10026.1/12437 |hdl-access=free }}]
== Effects ==
The WTX resulted in a rapid global temperature increase during the otherwise mild TEBCI.[{{Cite journal |last1=Erba |first1=Elisabetta |last2=Bartolini |first2=Annachiara |last3=Larson |first3=Roger L. |date=1 February 2004 |title=Valanginian Weissert oceanic anoxic event |url=https://pubs.geoscienceworld.org/geology/article/32/2/149-152/103728 |journal=[Geology](/source/Geology_(journal)) |language=en |volume=32 |issue=2 |page=149 |doi=10.1130/G20008.1 |bibcode=2004Geo....32..149E |issn=0091-7613 |access-date=5 November 2023|url-access=subscription }}] However, unlike other oceanic anoxic events, the WTX is not associated with widespread [black shale](/source/Shale) deposits.[{{Cite journal |last1=Bornemann |first1=André |last2=Erbacher |first2=Jochen |last3=Blumenberg |first3=Martin |last4=Voigt |first4=Silke |date=15 June 2023 |title=A first high-resolution carbon isotope stratigraphy from the Boreal (NW Germany) for the Berriasian to Coniacian interval—implications for the timing of the Aptian–Albian boundary |journal=[Frontiers in Earth Science](/source/Frontiers_in_Earth_Science) |volume=11 |pages=1–14 |doi=10.3389/feart.2023.1173319 |issn=2296-6463 |doi-access=free |bibcode=2023FrEaS..1173319B }}] Nannoconids experienced a decline at the onset of the WTX resulting from [marine regression](/source/marine_regression), but bloomed in abundance later on in the event as ocean productivity skyrocketed.[{{Cite journal |last1=Shmeit |first1=M. |last2=Giraud |first2=F. |last3=Jaillard |first3=E. |last4=Reboulet |first4=S. |last5=Masrour |first5=M. |last6=Spangenberg |first6=J. E. |last7=El-Samrani |first7=A. |date=1 August 2022 |title=The Valanginian Weissert Event on the south Tethyan margin: A dynamic paleoceanographic evolution based on the study of calcareous nannofossils |url=https://www.sciencedirect.com/science/article/pii/S0377839822000500 |journal=Marine Micropaleontology |volume=175 |article-number=102134 |doi=10.1016/j.marmicro.2022.102134 |s2cid=249325228 |issn=0377-8398 |access-date=5 November 2023|doi-access=free }}] In the Vocontian Basin, the WTX is associated with an increase in [marlstones](/source/Marl).[{{Cite journal |last1=Martinez |first1=Mathieu |last2=Guillois |first2=Landry |last3=Boulvais |first3=Philippe |last4=Deconinck |first4=Jean-François |date=8 May 2020 |title=Inverted Responses of the Carbon Cycle to Orbital Forcing in Mesozoic Periplatform Marginal Basins: Implications for Astrochronology |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019PA003705 |journal=[Paleoceanography and Paleoclimatology](/source/Paleoceanography_and_Paleoclimatology) |language=en |volume=35 |issue=6 |pages=1–19 |doi=10.1029/2019PA003705 |bibcode=2020PaPa...35.3705M |s2cid=218939500 |issn=2572-4517 |access-date=5 November 2023}}] At the end of the WTX, temperatures cooled by ~1–2 °C based on the results of [palaeothermometry](/source/Paleothermometer) done in southern France, whereas the Boreal Ocean and its surroundings cooled by as much as 4 °C.[{{Cite journal |last1=Cavalheiro |first1=Liyenne |last2=Wagner |first2=Thomas |last3=Steinig |first3=Sebastian |last4=Bottini |first4=Cinzia |last5=Dummann |first5=Wolf |last6=Esegbue |first6=Onoriode |last7=Gambacorta |first7=Gabriele |last8=Giraldo-Gómez |first8=Victor |last9=Farnsworth |first9=Alexander |last10=Flögel |first10=Sascha |last11=Hofmann |first11=Peter |last12=Lunt |first12=Daniel J. |last13=Rethemeyer |first13=Janet |last14=Torricelli |first14=Stefano |last15=Erba |first15=Elisabetta |date=13 September 2021 |title=Impact of global cooling on Early Cretaceous high pCO2 world during the Weissert Event |journal=[Nature Communications](/source/Nature_Communications) |language=en |volume=12 |issue=1 |page=5411 |doi=10.1038/s41467-021-25706-0 |pmid=34518550 |pmc=8437947 |issn=2041-1723 |doi-access=free }}] Geochemical records of 187Os/188Os point to an increase in unradiogenic osmium flux into the ocean, suggesting the occurrence of [silicate weathering](/source/Carbonate%E2%80%93silicate_cycle) of PE-LIP basalts during this slice of time, providing the most likely explanation for the temperature drop.[{{Cite journal |last1=Percival |first1=Lawrence M. E. |last2=Ownsworth |first2=E. |last3=Robinson |first3=S. A. |last4=Selby |first4=D. |last5=Goderis |first5=S. |last6=Claeys |first6=P. |date=1 August 2023 |title=Valanginian climate cooling and environmental change driven by Paraná-Etendeka basalt erosion |url=https://pubs.geoscienceworld.org/gsa/geology/article/51/8/753/623905/Valanginian-climate-cooling-and-environmental |journal=[Geology](/source/Geology_(journal)) |language=en |volume=51 |issue=8 |pages=753–757 |doi=10.1130/G51202.1 |bibcode=2023Geo....51..753P |issn=0091-7613 |access-date=22 December 2023 |via=GeoScienceWorld}}] Some studies have suggested that a transient ice age with limited but significant [polar ice caps](/source/Polar_ice_cap) occurred in the aftermath of the WTX,[{{Cite journal |last1=Gröcke |first1=Darren R. |last2=Price |first2=Gregory D. |last3=Robinson |first3=Stuart A. |last4=Baraboshkin |first4=Evgenij Y. |last5=Mutterlose |first5=Jörg |last6=Ruffell |first6=Alastair H. |date=1 December 2005 |title=The Upper Valanginian (Early Cretaceous) positive carbon–isotope event recorded in terrestrial plants |url=https://www.sciencedirect.com/science/article/pii/S0012821X05005546 |journal=[Earth and Planetary Science Letters](/source/Earth_and_Planetary_Science_Letters) |volume=240 |issue=2 |pages=495–509 |doi=10.1016/j.epsl.2005.09.001 |issn=0012-821X |access-date=5 November 2023|url-access=subscription }}] although the lack of a positive [δ18Oseawater](/source/%CE%9418O) excursion during the latest Valanginian interval of cooling and the presence instead of a very slightly negative excursion calls into question the existence of any significant polar ice growth.