Massive and rapid predominantly volcanic CO2 emission during the end-Permian mass extinction Ying Cuia,1, Mingsong Lib,1, Elsbeth E. van Soelenc, Francien Petersed, and Wolfram M. Kürschnerc,1 aDepartment of Earth and Environmental Studies, Montclair State University, Montclair, NJ 07043; bSchool of Earth and Space Sciences, Peking University, Beijing 100871, China; cDepartment of Geosciences, University of Oslo, Oslo 0371, Norway; and dDepartment of Earth Sciences, Utrecht University, 3584 CB Utrecht, The Netherlands Edited by Michael Manga, University of California, Berkeley, CA, and approved July 21, 2021 (received for review July 13, 2020) The end-Permian mass extinction event (∼252 Mya) is associated northern Norway on the Eastern Barents Sea shelf, hosting an with one of the largest global carbon cycle perturbations in the expanded shallow marine section (paleo-water depth roughly 50 Phanerozoic and is thought to be triggered by the Siberian Traps to 100 m) where two drill cores were collected (7128/12-U-01 volcanism. Sizable carbon isotope excursions (CIEs) have been found and 7129/10-U-01) spanning the Permian–Triassic transition (Fig. 1). 13 at numerous sites around the world, suggesting massive quantities A previously generated bulk organic carbon isotope record (δ Corg) 13 of C-depleted CO2 input into the ocean and atmosphere system. from the same core shows a two-step decline with a total carbon The exact magnitude and cause of the CIEs, the pace of CO2 emission, isotope excursion (CIE) magnitude of ∼4‰ (25). Although the and the total quantity of CO2, however, remain poorly known. Here, sedimentary organic carbon was considered primarily of terrestrial we quantify the CO2 emission in an Earth system model based on origin, small contributions from marine organic carbon production new compound-specific carbon isotope records from the Finnmark could not be excluded. Here, we use compound-specific carbon Platform and an astronomically tuned age model. By quantitatively isotope analysis of both long-chain and short-chain n-alkanes comparing the modeled surface ocean pH and boron isotope pH preserved in marine sediments in the Finnmark Platform to − proxy, a massive (∼36,000 Gt C) and rapid emission (∼5GtCyr 1) generate separate yet directly comparable records of δ13C for the ∼− of largely volcanic CO2 source ( 15%) is necessary to drive the terrestrial and the marine realm, respectively, across the EPME. observed pattern of CIE, the abrupt decline in surface ocean pH, Long-chain n-alkanes with a strong odd-over-even predominance and the extreme global temperature increase. This suggests that (n-C27 and n-C29) are produced by higher plant leaf waxes, and 13 the massive amount of greenhouse gases may have pushed the Earth their isotopic composition (δ Cwax) relates to their main carbon EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES system toward a critical tipping point, beyond which extreme changes source (i.e., atmospheric CO2) (26). On the other hand, short- in ocean pH and temperature led to irreversible mass extinction. The chain alkanes (n-C17 and n-C19) are derived from marine algae, 13 13 comparatively amplified CIE observed in higher plant leaf waxes sug- and their δ C values (δ Calgae) represent carbon in the marine gests that the surface waters of the Finnmark Platform were likely out realm (27, 28). To date, only a few EPME compound-specific car- of equilibrium with the initial massive centennial-scale release of bon isotope studies have been reported, all of which are limited by carbon from the massive Siberian Traps volcanism, supporting the unfavorable sedimentary facies or high thermal maturity of the or- rapidity of carbon injection. Our modeling work reveals that car- ganic matter (29, 30). In the present study, the exceptionally low bon emission pulses are accompanied by organic carbon burial, thermal maturity of the organic matter is evident from the yellow facilitated by widespread ocean anoxia. color of pollen and spores, indicating a color index 2 out of 7 on the thermal alteration scale of Batten (31), which is equivalent to a end-Permian mass extinction | compound specific carbon isotopes | CO2 | Earth system model Significance he end-Permian mass extinction (EPME) that occurred at The end-Permian mass extinction event (ca. 252 Mya) is the ± T251.941 0.037 Mya is considered the most severe biodi- most-severe biodiversity loss in Earth’s history and is globally versity loss in Earth history (1, 2). The EPME coincides with the recognized by a rapid negative carbon isotope excursion. The eruption of the Siberian Traps, a voluminous large igneous province trigger of this event, however, remains controversial. New paired 2 (LIP) that occupies 6 million square kilometers (km )inSiberia, terrestrial and marine compound-specific carbon isotope records Russia (3–5). The volcanic activity of this LIP is linked to SO2 and may provide clues for this enigma. By comparing observed data CO2 degassing generated by sill intrusion (6–10). The large amount to results from an isotope-enabled Earth system model, we find of CO2 injected into the atmosphere is thought to have led to that a massive and rapid, predominantly volcanic CO2 emission severe global warming (11–14), catastrophic ocean anoxia (15, 16), during the Siberian Traps volcanism is likely the trigger for the and extreme ocean and terrestrial acidification (17–21) being lethal carbon isotope excursion and the severe mass extinction. Our for life on land and in the sea (22). To date, no agreement has findings provide quantitative constraints of how a massive and 13 been reached regarding the source of the C-depleted carbon rapid increase in CO2 may have influenced the marine ecosystem that triggered the global carbon cycle perturbation, the decrease 252 Mya. in ocean pH, and the global warming across the EPME. Addition- Author contributions: W.M.K. designed research; Y.C., M.L., and E.E.v.S. performed re- ally, atmospheric CO2 levels following the initial pulse of Siberian search; Y.C., M.L., E.E.v.S., F.P., and W.M.K. analyzed data; and Y.C., M.L., E.E.v.S., F.P., and Traps volcanism and across the EPME remain poorly known (23, W.M.K. wrote the paper. 24), limiting our understanding of the climate feedbacks that occur The authors declare no competing interest. upon greenhouse gas release during this time. This article is a PNAS Direct Submission. To address this critical gap in our knowledge, we constrain the This open access article is distributed under Creative Commons Attribution License 4.0 source, pace and total amount of CO2 emissions using an Earth (CC BY). system model of intermediate complexity (i.e., carbon centric-Grid 1To whom correspondence may be addressed. Email: [email protected], cuiy@ Enabled Integrated Earth system model [cGENIE]; SI Appendix) montclair.edu, or [email protected]. 13 forced by new astronomically tuned δ C records from well- This article contains supporting information online at https://www.pnas.org/lookup/suppl/ preserved lipid biomarkers preserved in sediments from the Finn- doi:10.1073/pnas.2014701118/-/DCSupplemental. mark Platform, Norway. The Finnmark Platform is located offshore Published September 7, 2021. PNAS 2021 Vol. 118 No. 37 e2014701118 https://doi.org/10.1073/pnas.2014701118 | 1of11 Downloaded by guest on September 27, 2021 A 60° 1 30° 2 Paleo -Tethys 3 4 0° Panthalassic Ocean Pangaea Neo-Tethys 30° 60° B 90o N Siberian Traps LIP 60o N 1 2 30o N Paleo-Tethys 3 0o Panthalassic Ocean 4 Pangaea o 30 S Neo-Tethys 60o S 90o S Ocean depth (m) 0 538 1075 1613 2150 2688 3225 3763 4300 Fig. 1. (A) Paleogeographical map of the Late Permian, with former and current coastlines. Indicated are 1) the location of Finnmark cores 7128/12-U-01 and 7129/10-U-01, 2) the East Greenland site at Kap Stosch discussed in ref. 52, 3) the GSSP site for the base of the Triassic at Meishan, China, and 4) the Kuh-e-Ali Bashi site of Iran (66, 107). The map was modified after ref. 61. (B) Paleogeography and paleobathymetry of the Late Permian used in cGENIE. vitrinite reflectance R0 of 0.3%. Moreover, the high sedimentation Results and Discussion 13 13 rate (discussed in Carbon Cycle Quantification Using Astrochro- Fidelity of the δ Calgae and δ Cwax Records. The long-chain n-alkanes nology and Earth System Model) of the siliciclastic sediments at in the Finnmark core show a strong odd-over-even predominance the study site allows for studying both marine and terrestrial CIE as evidenced by a carbon preference index well above 2 (Fig. 2B across the EPME in unprecedented detail. Taken together, the and SI Appendix), supporting the presumed low thermal maturity Finnmark sedimentary records enable the reconstruction of in- of the sediments (34). The average chain length (ACLC25-C33) dividual yet directly comparable carbon isotope records for the varies between 27.5 and 29.5 and shows an increasing trend up- terrestrial and the marine realm that can be astronomically tuned core (Fig. 2C), in which higher ACL values correspond to high and used to quantitatively assess the source, pace, and total numbers of conifer pollen counts in the same core (e.g., at 110- to amount of 13C-depleted carbon released during the Siberian Traps 95-m core depth), and low ACL values are associated with the eruption that led to the EPME. Using our new compound-specific pteridosperm (seed fern)-dominated ecosystem that existed prior carbon isotope records, rather than marine carbonates, has several to the EPME (Fig. 2A). The interval with intermediate ACL (116- advantages: 1) new astrochronology enables a 104-year temporal to 108-m core depth) is linked to a spore peak and the first neg- ative excursion in the δ13C record of sedimentary organic matter resolution for our paired marine and terrestrial carbon isotope (δ13C )(Fig.2F), suggesting that local terrestrial ecosystem re- records; 2) we do not need to assume a constant sedimentation org organization may have modified the original δ13C signal across rate between tie point or using diachronous biozones to compare org the EPME at this site (25, 35).