Selli Event

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The Selli Event, also known as OAE1a, was an oceanic anoxic event (OAE) of global scale that occurred during the Aptian stage of the Early Cretaceous, about 120.5 million years ago (Ma).[1] The OAE is associated with large igneous province volcanism and an extinction event of marine organisms driven by global warming, ocean acidification, and anoxia.[2]

Timing[edit]

The negative carbon isotope excursion (CIE) representing the onset of OAE1a was rapid, taking only 22,000-47,000 years.[3] The recovery of the global climate from the injection of large amounts of isotopically light carbon lasted for over a million years.[4] The OAE lasted for about 1.1 to 1.3 Myr in total;[5] one high-precision estimate put the length of OAE1a at 1.157 Myr.[6]

Causes[edit]

Global warming[edit]

OAE1a ensued during a hot climatic interval, with the global average temperature being around 21.5 °C.[7] The Tethys Ocean experienced an increase in humidity at the beginning of OAE1a, while conditions around the Boreal Ocean were initially dry and only humidified later on during the OAE.[8]

The increase in global temperatures that caused OAE1a was most likely driven by large igneous province (LIP) volcanism.[2] The negative δ13C excursion preceding the OAE, occurring in the C3 isotopic interval,[9] is believed to reflect volcanic release of carbon dioxide into the atmosphere and its consequent warming of the Earth.[10] Enrichments in unradiogenic osmium, which is primarily derived from alteration of oceanic crust by hydrothermal volcanism, further bolster volcanism as the driver of OAE1a.[11][12] Multiple LIPs have been implicated as causes of the rapid global warming responsible for the onset of OAE1a, including the High Arctic Large Igneous Province (HALIP),[13] the Kerguelen Plateau,[2] and the Ontong Java Plateau.[10][14][15] The rate of greenhouse gas emissions leading up to OAE1a was relatively slow, causing the anoxic event to only generate a minor extinction event, in contrast to the severe LIP-induced Capitanian, Permian-Triassic, and Triassic-Jurassic mass extinctions and the ongoing Holocene extinction caused in part by anthropogenic greenhouse gas release, each of which were or are characterised by a very high rate of carbon dioxide discharge.[2] Despite a much smaller methane clathrate reservoir relative to the present day, the degassing of methane clathrate deposits may have nonetheless significantly exacerbated volcanic warming.[14] Following OAE1a, δ18O values increased, indicating a drop in temperatures that coincided with a δ13Corg decline,[16] which began in the C4 isotopic phase of the interval.[9]

Enhanced phosphorus recycling[edit]

OAE1a coincided with a peak in a 5-6 Myr periodicity cycle in the accumulation of phosphorus in marine sediments. During such peaks, the short-term positive feedback loop of increased biological productivity caused by an abundance of phosphorus that caused decreased oxygenation of seawater that then caused increased regeneration of phosphorus from marine sediments dominated, but it was eventually mitigated by a long-term negative feedback loop caused by an increase in atmospheric oxygen that resulted in enhanced wildfire activity and diminished phosphorus input into the oceans.[17] An increase in the ratios of organic carbon to reactive phosphorus species and of total nitrogen to reactive phosphorus confirms leakage of sedimentary phosphorus back into the water column occurred during OAE1a, with this process likely being accelerated by the increased global temperatures of the time.[18]

Effects[edit]

Marine productivity increased. The productivity spike was likely driven by an increase in iron availability.[1] Increased sulphate flux from volcanism caused an increase in hydrogen sulphide production, which in turn increased phosphorus availability in the water column by inhibiting its burial on the seafloor and enabled the development of anoxia.[19]

The large-scale volcanic release of carbon dioxide caused a drop in the pH of seawater at the start of OAE1a, as much of this excess carbon dioxide was absorbed by the ocean and dissolved as carbonic acid.[20] Seawater carbonate-saturation was severely reduced.[21] Ocean acidification began shortly after the negative δ13C excursion and lasted for approximately 0.85 Myr.[22] The drop in seawater pH was associated with the acme of the carbonate crisis.[23]

δ7Li measurements indicate an enrichment in isotopically light lithium coeval with the negative δ13C excursion, signifying an increase in silicate weathering amidst the volcanically induced global warming of OAE1a. A second negative δ7Li excursion occurred synchronously with a strontium isotope minimum, demarcating another peak in silicate weathering. This weathering may have buffered the warming effects of large igneous province volcanism and helped to cool the Earth back to its pre-OAE1a state.[24]

OAE1a, as with other OAEs, exhibited widespread deposition of black shales rich in organic matter incapable of being decomposed on the seabed, as the anoxic conditions prohibited habitation of most microbial decomposers.[1] Black shale deposition begins during the C6 stage of OAE1a and lasted for around 0.4 Myr.[22]

Overall, the biotic effects of OAE1a were comparatively minor relative to other LIP-driven extinction events.[2][25] Nannoconids that were highly calcified suffered significant decline during OAE1a, likely as a consequence of ocean acidification,[20] although this causal relationship is disputed by other authors.[26]

See also[edit]

References[edit]

  1. ^ a b c Leckie, R. Mark; Bralower, Timothy J.; Cashman, Richard (23 August 2002). "Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid-Cretaceous". Paleoceanography and Paleoclimatology. 17 (3): 13-1–13-29. Bibcode:2002PalOc..17.1041L. doi:10.1029/2001PA000623. Retrieved 20 May 2023.
  2. ^ a b c d e Jiang, Qiang; Jourdan, Fred; Olierook, Hugo K. H.; Merle, Renaud E.; Bourdet, Julien; Fougerouse, Denis; Godel, Belinda; Walker, Alex T. (25 July 2022). "Volume and rate of volcanic CO2 emissions governed the severity of past environmental crises". Proceedings of the National Academy of Sciences of the United States of America. 119 (31): e2202039119. Bibcode:2022PNAS..11902039J. doi:10.1073/pnas.2202039119. PMC 9351498. PMID 35878029.
  3. ^ Malinverno, A.; Erba, Elisabetta; Herbert, Timothy D. (4 May 2010). "Orbital tuning as an inverse problem: Chronology of the early Aptian oceanic anoxic event 1a (Selli Level) in the Cismon APTICORE". Paleoceanography and Paleoclimatology. 25 (2): 1–16. Bibcode:2010PalOc..25.2203M. doi:10.1029/2009PA001769.
  4. ^ Li, Yong-Xiang; Bralower, Timothy J.; Montañez, Isabel P.; Osleger, David A.; Arthur, Michael A.; Bice, David M.; Herbert, Timothy D.; Erba, Elisabetta; Premoli Silva, Isabella (15 July 2007). "Toward an orbital chronology for the early Aptian Oceanic Anoxic Event (OAE1a, ~ 120 Ma)". Earth and Planetary Science Letters. 271 (1–4): 88–100. Bibcode:2008E&PSL.271...88L. doi:10.1016/j.epsl.2008.03.055. Retrieved 20 May 2023.
  5. ^ Hu, Xiumian; Zhao, Kuidong; Yilmaz, Ismail Omer; Li, Yongxiang (December 2012). "Stratigraphic transition and palaeoenvironmental changes from the Aptian oceanic anoxic event 1a (OAE1a) to the oceanic red bed 1 (ORB1) in the Yenicesihlar section, central Turkey". Cretaceous Research. 38: 40–51. Bibcode:2012CrRes..38...40H. doi:10.1016/j.cretres.2012.01.007. Retrieved 20 May 2023.
  6. ^ Moullade, Michel; Tranchetti, Guy; Granier, Bruno; Bornemann, André; Kuhnt, Wolfgang; Lorenzen, Janne (September–December 2015). "High-resolution integrated stratigraphy of the OAE1a and enclosing strata from core drillings in the Bedoulian stratotype (Roquefort-La Bédoule, SE France)". Cretaceous Research. 56: 119–140. Bibcode:2015CrRes..56..119M. doi:10.1016/j.cretres.2015.03.004. Retrieved 20 May 2023.
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  8. ^ Blok, C. N.; Ineson, J.; Anderskouv, K.; Fantasia, A.; Sheldon, E.; Thibault, N.; Jelby, M. E.; Adatte, T.; Bodin, S. (1 September 2022). "Latitude-dependant climate changes across the Aptian Oceanic Anoxic Event 1a". Palaeogeography, Palaeoclimatology, Palaeoecology. 601: 111085. Bibcode:2022PPP...601k1085B. doi:10.1016/j.palaeo.2022.111085. S2CID 249328937.
  9. ^ a b Chen, Xi; Idakieva, Vyara; Stoykova, Kristalina; Liang, Huiming; Yao, Hanwei; Wang, Chengshan (November 2017). "Ammonite biostratigraphy and organic carbon isotope chemostratigraphy of the early Aptian oceanic anoxic event (OAE 1a) in the Tethyan Himalaya of southern Tibet". Palaeogeography, Palaeoclimatology, Palaeoecology. 485: 531–542. doi:10.1016/j.palaeo.2017.07.010. Retrieved 12 April 2024 – via Elsevier Science Direct.
  10. ^ a b Keller, Christina E.; Hochuli, Peter A.; Weissert, Helmut; Bernasconi, Stefano M.; Giorgioni, Martino; Garcia, Therese I. (15 May 2011). "A volcanically induced climate warming and floral change preceded the onset of OAE1a (Early Cretaceous)". Palaeogeography, Palaeoclimatology, Palaeoecology. 305 (1–4): 43–49. Bibcode:2011PPP...305...43K. doi:10.1016/j.palaeo.2011.02.011. Retrieved 20 May 2023.
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  12. ^ Matsumoto, Hironao; Coccioni, Rodolfo; Frontalini, Fabrizio; Shirai, Kotaro; Jovane, Luigi; Trindade, Ricardo; Savian, Jairo F.; Koroda, Junichiro (11 January 2022). "Mid-Cretaceous marine Os isotope evidence for heterogeneous cause of oceanic anoxic events". Nature Communications. 13 (1): 239. Bibcode:2022NatCo..13..239M. doi:10.1038/s41467-021-27817-0. PMC 8752794. PMID 35017487. Retrieved 13 June 2023.
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  14. ^ a b Méhay, Sabine; Keller, Christian E.; Bernasconi, Stefano M.; Weissert, Helmut; Erba, Elisabetta; Bottini, Cinzia; Hochuli, Peter A. (1 September 2009). "A volcanic CO2 pulse triggered the Cretaceous Oceanic Anoxic Event 1a and a biocalcification crisis". Geology. 37 (9): 819–822. Bibcode:2009Geo....37..819M. doi:10.1130/G30100A.1. Retrieved 13 June 2023.
  15. ^ Benigno, Ana Paula A.; Saraiva, Antônio Á. F.; Sial, Alcides N.; Lacerda, Luiz D. (April 2021). "Mercury chemostratigraphy as a proxy of volcanic-driven environmental changes in the Aptian-Albian transition, Araripe Basin, northeastern Brazil". Journal of South American Earth Sciences. 107: 1–30. doi:10.1016/j.jsames.2020.103020. S2CID 228919907. Retrieved 2 September 2023.
  16. ^ Price, Gregory D. (September 2003). "New constraints upon isotope variation during the early Cretaceous (Barremian–Cenomanian) from the Pacific Ocean". Geological Magazine. 140 (5): 513–522. doi:10.1017/S0016756803008100. S2CID 129629420. Retrieved 8 August 2023.
  17. ^ Handoh, Itsuki C.; Lenton, Timothy M. (8 October 2003). "Periodic mid-Cretaceous oceanic anoxic events linked by oscillations of the phosphorus and oxygen biogeochemical cycles". Global Biogeochemical Cycles. 17 (4): 3-1–3-11. Bibcode:2003GBioC..17.1092H. doi:10.1029/2003GB002039. S2CID 140194325. Retrieved 14 June 2023.
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  19. ^ Gomes, Maya L.; Hurtgen, Matthew T.; Sageman, Bradley B. (21 December 2015). "Biogeochemical sulfur cycling during Cretaceous oceanic anoxic events: A comparison of OAE1a and OAE2". Paleoceanography and Paleoclimatology. 31 (2): 233–251. doi:10.1002/2015PA002869. Retrieved 19 December 2022.
  20. ^ a b Erba, Elisabetta; Bottini, Cinzia; Weissert, Helmut J.; Keller, Christina E. (23 July 2010). "Calcareous Nannoplankton Response to Surface-Water Acidification Around Oceanic Anoxic Event 1a". Science. 329 (5990): 428–432. Bibcode:2010Sci...329..428E. doi:10.1126/science.1188886. PMID 20651148. S2CID 19498439. Retrieved 24 January 2023.
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  22. ^ a b Li, Juan; Hu, Xiumian; Zhao, Kuidong; Cai, Yuanfeng; Sun, Tao (November 2016). "Paleoceanographic evolution and chronostratigraphy of the Aptian Oceanic Anoxic Event 1a (OAE1a) to oceanic red bed 1 (ORB1) in the Gorgo a Cerbara section (central Italy)". Cretaceous Research. 66: 115–128. Bibcode:2016CrRes..66..115L. doi:10.1016/j.cretres.2016.04.016. Retrieved 21 May 2023.
  23. ^ Giraud, Fabienne; Pittet, Bernard; Grosheny, Danièle; Baudin, François; Lécuyer, Christophe; Sakamoto, Tatsuhiko (15 December 2018). "The palaeoceanographic crisis of the Early Aptian (OAE 1a) in the Vocontian Basin (SE France)". Palaeogeography, Palaeoclimatology, Palaeoecology. 511: 483–505. doi:10.1016/j.palaeo.2018.09.014. Retrieved 12 April 2024 – via Elsevier Science Direct.
  24. ^ Lechler, Maria; Von Strandmann, Philip A.E. Pogge; Jenkyns, Hugh C.; Prosser, Giacomo; Parente, Mariano (15 December 2015). "Lithium-isotope evidence for enhanced silicate weathering during OAE 1a (Early Aptian Selli event)". Earth and Planetary Science Letters. 432: 210–222. Bibcode:2015E&PSL.432..210L. doi:10.1016/j.epsl.2015.09.052. Retrieved 20 May 2023.
  25. ^ Wignall, Paul B. (29 September 2015). "Pangea's Death and the Rise of Resilience". The Worst of Times: How Life on Earth Survived Eighty Million Years of Extinctions. Princeton: Princeton University Press. p. 158. ISBN 978-0-691-14209-8.
  26. ^ Gibbs, Samantha J.; Robinson, Stuart A.; Bown, Paul R.; Jones, Tom Dunkley; Henderiks, Jorijntje (8 April 2011). "Comment on "Calcareous Nannoplankton Response to Surface-Water Acidification Around Oceanic Anoxic Event 1a"". Science. 332 (6026): 175. Bibcode:2011Sci...332..175G. doi:10.1126/science.1199459. PMID 21474738. S2CID 42860173. Retrieved 21 May 2023.
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