https://doi.org/10.1130/G48022.1

Manuscript received 13 June 2020 Revised manuscript received 3 September 2020 Manuscript accepted 6 September 2020

© 2020 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Published online 4 November 2020

Pulsed volcanic events coincident with the end- Permian terrestrial disturbance and the following global crisis Kunio Kaiho1*, Md. Aftabuzzaman1, David S. Jones2 and Li Tian3 1Department of Science, Tohoku University, Sendai 980-8578, Japan 2Department of Geology, Amherst College, 11 Barrett Hill Road, Amherst, Massachusetts 01002, USA 3State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China

ABSTRACT boundary; 31°04′47.28′′N, 119°42′20.88′′E), Eruption of the Siberian Traps large igneous province (LIP) is thought to have triggered Zhejiang Province, southern China; and Bul- the Permian-Triassic biological crisis, the largest of the Phanerozoic mass extinctions. Mer- la (46°33′52.16″N, 11°38′07.02″E), between cury concentration enrichments have been widely used as a proxy for volcanic inputs to the towns of Castelrotto and Ortisei, northern sediments, especially for ancient LIP eruptions. However, detailed correlations of magmatic Italy (Fig. 1). These sections are correlated by pulses with extinction events in the terrestrial and marine realms are not fully resolved. Here conodont zones and carbonate carbon isotopes we use paired coronene (a six-ring polycyclic aromatic hydrocarbon, a high-temperature (Chen et al., 2016; Kaiho et al., 2016a), and for combustion proxy) and mercury spikes as a refined proxy for LIP emplacement. In records Meishan, high-precision isotope dilution–ther- from stratigraphic sections in south China and Italy, we identify two sets of paired coronene- mal ionization mass spectrometry (ID-TIMS) mercury spikes accompanied by land plant biomarker spikes, followed by a rapid decrease U-Pb dating provides a highly-resolved age coinciding with terrestrial ecological disturbance and extinction of marine metazoans. Each model (Burgess et al., 2014; Yin et al., 2014). short-term episode is likely caused by high-temperature combustion of sedimentary hydro- Each studied sample covers 1–3 cm in height, carbons during initial sill emplacement of the Siberian Traps LIP. These data indicate that with no gaps between samples for the critical discrete volcanic eruptions could have caused the terrestrial ecosystem crisis followed by horizons (each bed was cut into several samples; the marine ecosystem crisis in ∼60 k.y., and that the terrestrial ecosystem was disrupted by see Tables S1–S3 in the Supplemental Material1). smaller global environmental changes than the marine ecosystem. We used five- to six-ring PAHs as (benzo[e] pyrene + benzo[ghi]perylene + coronene) / phen- INTRODUCTION centration in many marine and nonmarine set- anthrene (egc/phe), the coronene/phe ratio, and The Permian-Triassic (P-Tr) mass extinction tings (e.g., Wang et al., 2018; Shen et al., 2019b; the coronene index (coronene/egc) to estimate is composed of two separate global events: (1) Chu et al., 2020). Further, elevated mercury can combustion events, high-temperature combustion the end-Permian terrestrial ecological distur- be sourced from either direct atmospheric depo- events, and combustion temperature, respectively bance (EPTD); and (2) the sudden global end- sition from volcanic emissions or riverine inputs (Kaiho et al., 2016b; Fig. S1 in the Supplemen- Permian extinction (EPE), accompanied by soil from terrestrial organic-matter oxidation (Gras- tal Material); and the terrestrial plant index [n-

erosion and surface-water anoxia (Song et al., by et al., 2013, 2017, 2019; Wang et al., 2018; alkane ratio (n-C27+29+31)/(n-C17+19+21+27+29+31)] to 2013; Kaiho et al., 2016a). The EPTD predated Shen et al., 2019a; Dal Corso et al., 2020). Thus, investigate soil erosion and vegetation collapse the EPE by tens of thousands to hundreds of we use the concentration of coronene (a six- (long chain n-alkanes are widely used terrestrial thousands of years (Fielding et al., 2019). These ring polyaromatic hydrocarbon [PAH] formed plant biomarkers; Bush and McInerney, 2013). events are hypothesized outcomes of Siberian by high-temperature combustion) in conjunction Although total PAHs are usually used as combus- Traps (Shen et al., 2011; Bond and with mercury to identify P-Tr volcanic events. tion proxy, we used egc/phe and coronene/phe be- Grasby, 2017; Burgess et al., 2017). cause phenanthrene (a three-ring PAH, the most Sedimentary mercury enrichments, proxies GEOLOGIC SETTING AND METHODS common PAH) is also formed by diagenesis, and for massive volcanic events, have been detected We analyzed abundances of combustion- five- to six-ring PAHs are enriched in combustion in dozens of P-Tr boundary sections across the related and terrestrial plant–related biomark- materials. More detailed methods are provided in globe (e.g., Sanei et al., 2012; Wang et al., 2018; ers, mercury abundance, and total organic car- the Supplemental Material. Grasby et al., 2019; Shen et al., 2019a), but un- bon (TOC) in sedimentary rock samples from certainty remains in their interpretation. First, three low-latitude shallow marine sections: Li- RESULTS the EPE lagged the initial spike of mercury con- angfengya (29°30′29.65″N, 106°52′58.26″E), We measured biomarker concentrations 13 km west of the city of Chongqing, south- well above detection limits and blank sample

western China; Meishan (the Global Strato- values. The 22S/(22S + 22R) ratio of C31 ho- *E-mail: [email protected] type Section and Point [GSSP] for the P-Tr mohopanes and computed vitrinite reflectance

1Supplemental Material. Methods, geochemical data, and supplemental figures. Please visithttps://doi.org/10.1130/GEOL.S.13076138 to access the supplemental material, and contact [email protected] with any questions.

CITATION: Kaiho, K., et al., 2021, Pulsed volcanic combustion events coincident with the end-Permian terrestrial disturbance and the following global crisis: Geology, v. 49, p. 289–293, https://doi.org/10.1130/G48022.1

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Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/49/3/289/5236761/289.pdf by guest on 29 September 2021 ter coincident with volcanism and extinction. Coronene is a highly condensed six-ring PAH Figure 1. Global paleo- and a stable molecule in Earth surface environ- geographic map showing ments and can be preserved across geological location of sections stud- time. It requires abnormally high energy to ied () and referenced form coronene from hydrocarbons compared to (squares), as well as the related Siberian Traps smaller PAHs, as evidenced by heating experi- large igneous province. ments and thermodynamic simulations (Nori- Base map is after Ziegler naga et al., 2009). combustion occurs et al. (1998). at 700–1000 °C (Pyne et al., 1996) and produces coronene indices ∼0.1, which correspond to the background values for mass extinctions (Kaiho et al., 2016b). The ∼0.1 value is also formed by (Rc) (­methylphenanthrene ratio, MPR) values High correlation between Hg and Hg/TOC 900–1000 °C in shorter-duration (a few seconds) in the three sections studied indicate that all the beginning below the events and continuing to heating, and the high coronene indices (>0.3) samples are “mature” at the stage of early to Event 2 (r = +0.83; Fig. 3D) indicates that there observed in Events 1 and 2, and the third spike peak oil generation, indicating no contamina- is little influence of the low TOC on the spikes of coronene, require combustion temperatures tion by modern hydrocarbon (Tables S1–S3). in Hg/TOC during the events in Liangfengya. >∼1200 °C (estimated from data of Norinaga Ten TOC measurements of a limestone from Here, low TOC (<0.2%) does not produce ar- et al. [2009]). Such high-temperature combus- Liangfengya with very low TOC yield a mean of tificial spikes in Hg/TOC for the two events. tion of organic matter to form coronene can oc- 0.03577% with standard deviation of 0.00053%, The correlation coefficient between Hg/TOC cur with large-scale volcanic activity or aster- with measured mass of carbon in all studied rock and coronene/phe and between Hg and coro- oid or comet impacts causing high-temperature samples more than five times the lowest detec- nene/phe is high during the pre-events to Event combustion of sedimentary hydrocarbon and ter- tion limit; the results indicate the reliability of 2 (r = +0.47 and +0.32, respectively) and low restrial plants in the emplacement or target ar- the TOC data despite their low concentrations after the Event 2 (r = –0.16 and –0.32, respec- eas. Five- to six-ring PAHs, including coronene (Tables S4–S6). tively; Figs. 3B and 3C). These correlation varia- enrichment, have been found associated with This study identifies coincidental high values tions imply that the sources of Hg subsequent to three mass extinctions (Late Devonian, end- of coronene/phe and Hg/TOC as volcanic events Event 2 differed from those for the lower beds. Permian, and Cretaceous-Paleogene boundary) because terrestrial biomass oxidation does not The relatively high TOC in samples predating but are absent from strata immediately below cause enrichment of the five- to six-ring PAHs. Event 1 at Bulla causes low correlation between and above the mass-extinction horizons (Kaiho At Liangfengya, the first volcanic event (Event Hg and the other proxies (Figs. 3H–3J) because et al., 2013, 2016b; this study). 1) occurred in the upper part of bed 14 to basal the main host of the Hg is TOC. We normalized The coronene indices of the two events bed 17, from the uppermost part of the Clarkina Hg by TOC, resulting in high correlation be- identified here are indicative of temperatures changxingensis to the basal C. yini zone, asso- tween Hg/TOC and coronene/phe and between produced by sill intrusion (Aarnes et al., 2010; ciated with the start of gradual negative carbon Hg/TOC and the coronene index (r = +0.59 and French and Romanowicz, 2015), and the age of isotope shift at level C (Kaiho et al., 2016a), +0.72, respectively; Figs. 3F and 3G). the events overlaps with the dates of Siberian which is correlative to a spike in coronene/phe The coronene/phe and Hg/TOC values indi- Traps sill emplacement (Burgess et al., 2017). and Hg/TOC in the lower part of bed 8 at Bulla cate that Event 1 was a smaller environmental Fly ash loading Events I and III of Grasby et al. and the middle of bed 23 in the C. changxingen- change than Event 2 in the three sections. High (2011) and Hg/TOC spikes at nonmarine sites sis zone at Meishan, ∼60 k.y. before the EPE coronene indices occurred globally only during (Chu et al., 2020; Fig. 4) are correlated to events (Fig. 2). A major Hg/TOC spike occurred in the Events 1–2, and in the third spike (0.3–0.8 rela- 1 and 2 recognized in this study based on carbon ash of bed 16 and in the basal part of the su- tive to background average value of 0.04–0.15) isotope (CI) correlations (CI levels C and D of perjacent limestone (twice background values) (Fig. 2; Tables S1–S3). The correlation between Kaiho et al. [2016a]). at Liangfengya. At Meishan, Hg/TOC reaches Hg and the terrestrial plant index is high dur- The synchronous occurrence of elevated three times background values, coinciding with ing the events (r = +0.61, +0.44) but low in the coronene index and elevated Hg requires vol- high coronene/phe in middle of bed 23 in Event other samples (r = –0.08, –0.21) at Liangfengya canic injections into the stratosphere, rather the 1. A significant spike in coronene/phe occurred and Bulla, respectively (Figs. 3E and 3J). These weathering on land. Therefore, the two events in all three sections. This event corresponds to findings imply that the terrestrial input due to reported here are associated with pulsed volca- the EPTD, identified by a concurrent spike in the plant crisis contributed to the Hg enrich- nic emissions, with the second event larger in the terrestrial plant index followed by a drastic ment in shallow marine sediments. Events 1 and magnitude. These data link the EPTD and EPE decrease. Volcanic Event 2 (beds 18–20 at Li- 2 coincided with high values of the terrestrial to volcanic eruptions. The Hg could have been angfengya) corresponds to the marine EPE iden- plant index followed by a significant decrease, sourced from gas formed in the contact aureole tified by a drastic decrease in species richness showing plant organic-matter influx and terres- of sedimentary rocks, , and wildfire and disappearance of fossils in thin sections, trial ecosystem devastation (Figs. 2A and 2B). ash deposited by flow, ejected together by which is correlative to a spike in coronene/phe The long-lasting high values of the coronene eruptions of high-pressure gas forming in the and Hg/TOC at the EPE the upper part of bed index compared to the short durations of Events aureole, resulting in global distribution of Hg. 8 at Bulla and at the top of bed 24, black marl 1 and 2 observed in the Liangfengya and Bulla Additional Hg was supplied from soil oxidation. (Kaiho et al., 2006), at Meishan within the same sections suggest that low-magnitude volcanic The third spike of coronene/phe in the three sec- conodont zone (C. yini zone; Fig. 2). A third eruptions persisted during the events. tions studied is correlated to the largest spike of spike in coronene/phe, with no corresponding Hg/TOC in the Chinahe area (Fig. 1) between spike in Hg/TOC, occurred in the Hindeodus DISCUSSION the CI levels E and F, which may be the third praeparvus zone or the equivalent zone of the Our coronene record demonstrates very volcanic event coinciding with a ∼10 °C global 18 three sections at ∼30 k.y. after the EPE. high-temperature combustion of organic mat- warming detected by δ Oapatite in several sections

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Figure 2. Stratigraphic changes in Hg, Hg/TOC (TOC—total organic carbon), and organic geochemical indices of combustion, temperature, and terrestrial plants, 13 with δ Ccarbonate data. 1,2—global volcanic combustion events; 3,4— events supported by only B coronene or only Hg; 5—nonevent. Blue let- ters A-F indicate carbon isotope levels (modified from Kaiho et al., 2016a). Vertical red dashed lines indicate the boundary between low-temperature combustion background values and high-temper- ature combustion values. 18 δ Oapatite is after Chen et al. (2016). Meishan data are from Jin et al. (2000), Shen et al. (2011), Burgess et al. (2017), Grasby et al. (2017), Wang et al. (2018), Shen et al. (2019a), and this study (light gray dots and blue C dots [Hg and Hg/TOC]). C. ch.—Clarkina changx- ingensis; C. me.—C. meishanensis; H.—Hindeo- dus. I.—Isarcicella­ ; VPDB—Vienna Peedee belemnite; phe—phenan- threne; VSMOW—Vienna standard mean ocean water; EPE—end-Permian extinction; EPTD— end-Permian terrestrial ecological disturbance.

including Liangfengya and Meishan (Chu et al., Basin, South Africa, predates the northern low- magma intrusion (sills) regionally heated To- 2020; Chen et al., 2016; Figs. 2 and 4). latitude EPTD by ∼240 k.y. based on U-Pb zir- nian–Cambrian oil, Permian coal, and hydro- The terrestrial ecological disturbance is con dating (Figs. 1 and 4; Fielding et al., 2019; carbons in the ∼3-km-thick sedimentary rock supported by spikes in dibenzofuran/phe ratios Gastaldo et al., 2020). succession to generate high-pressure volatile

in Bulla and Meishan during Event 1 and in Based on our correlations, the ages of the gases (e.g., CH4, CO2, SO2, halogen; Svensen many sections (Italy, south China, Japan) during two events correspond to ages of the initial et al., 2009) along with coronene and mercury. Event 2 (Kaiho et al., 2016a). In high southern stage of laterally extensive sill emplacement A series of short intense eruptions distributed latitudes, the last occurrence of coal and Glos- and pyroclastic eruptions in the Siberian Traps their volatile load and combustion products to sopteris and initiation of chemical weathering LIP (Burgess et al., 2017; Fig. 4). The presence the stratosphere; these were globally distribut- (recorded by the extent of feldspar alteration of several thousand volcanic pipes, remnants ed, resulting in climate changes (Svensen et al., to clay) reported in the Sydney core, Australia, of eruptions, in the eastern Siberian Tunguska 2009; Grasby, et al., 2017; Black et al., 2018). and a terrestrial vertebrate turnover in the Karoo Basin imply that the laterally extensive basaltic These products accumulated in both terrestrial

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F G H I J

Figure 3. Cross plots of Hg and total organic carbon (TOC) (A), data at Liangfengya (LFY, southwestern China; B–E), and data at Bulla (Italy; F–J), showing correlation coefficients (r). In B–J: red circles—before and during volcanic combustion events at Liangfengya (beds 14–20; see Fig. 2) and during and after events at Bulla (because of high TOC before the events; beds 7–12); blue squares—other beds. phe—phenanthrene. Blue arrow shows where high TOC of pre-event strata produces high Hg content.

and marine environments and produced the two climate change mainly in high latitudes, causing bance; (2) after ∼240 k.y., Siberian Traps sill- short-term coronene-mercury events identified the localized and earlier terrestrial ecological complex growth, represented here by sedimen- here. Terrestrial ecological disturbance in the disturbance. tary coronene-mercury anomalies, led to global high southern latitudes coincided with initial The temporal correlations between biotic devegetation on land and a decrease in global flood of Siberian Traps at 252.27 Ma based changes and volcanism-driven environmental marine δ13C (CI levels C to E); (3) after anoth- on U-Pb zircon dating (Fig. 4; Burgess et al., devastation likely unfolded as follows (Fig. 4): er ∼60 k.y., the largest volcanic eruptions pro- 2017; Fielding et al., 2019; Mays et al., 2020). (1) Siberian Traps flood-lava eruptions caused duced huge amounts of coronene and mercury The huge flood-lava eruptions may have caused high-latitude local terrestrial ecological distur- and caused the second terrestrial devastation,

Figure 4. Correlation between volcanic and biotic events in marine and nonmarine sections (see Fig. 1 for locations) and magmatic phases of the Siberian Traps large igneous province (LIP) based on conodont zones (red lowercase letters), carbon isotope stratigraphy (red uppercase letters; [Kaiho et al., 2016a]), and U-Pb zircon dates (red “U-Pb” [Burgess et al., 2014; Fielding et al., 2019; Gastaldo et al., 2020]). Hexagonal marks show chemical structure of coronene. Orange bands with blue numbers show volcanic events 1 and 2. Pale orange band with 3 shows the third spike of coronene. Meishan data are from same references as in Figure 2. Chinahe data are from Chu et al. (2020). High-southern- latitude data are after Fielding et al. (2019) and Gastaldo et al. (2020). Siberian Traps LIP events are after Burgess et al. (2017). Pale colors in the Siberian Traps LIP show ranges including measurement errors. a—Clarkina changxingensis; b—C. yini; c—C. meishanensis; d—Hindeodus changxingensis; e—C. taylorae; f—H. parvus; g—Isarcicella staeschei; h—I. isarcica; Ni—Ni spike; TOC—total organic carbon; phe—phenanthrene; carb—carbonate; org—organic; EPE—end-Permian extinction; EPTD—end-Permian terrestrial ecological disturbance.

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