SignificanceEstimates of seawater Li isotopic composition at the Permian–Triassic boundary (PTB) reveal extremely light seawater Li isotopic signatures accompanying the most severe mass extinction in the history of animal life. Theoretical modeling indicates a rapid enhancement of continental weathering during this time, which was likely triggered by the eruption of the Siberian Traps, rapid global warming, and acid rains. Our results provide independent geochemical evidence for an enhanced continental chemical weathering at the PTB, illustrating that continental weathering may provide a key link between terrestrial and marine ecological crises.

Fig. DR1: The biostratigraphic correlation between the Penglaitan, Tieqiao and EF sections. The conodont biostraigraphy in South China is after Jin et al. (2006) and Mei et al. (1998) and the conodont biostratigraphy of the EF section is after Wardlaw and Nestell (2010). For both the Penglaitan and Tieqiao sections, five conodont zones of J. xuanhanensis, J. granti, C. p. hongshuiensis, C. p. postbitteri, and C. dukouensis were defined and the two sections are correlated based on conodont zonation. The correlation between the EF section and the Penglaitan section is based on the conodont zone of J. xuanhanensis at each section, the conodont zone of C. p. hongshuiensis at each section, and the Guadalupian-Lopingian boundary identified at each section.

The end-Permian mass extinction represents the most severe biotic crisis for the last 540 million years, and the marine ecosystem recovery from this extinction was protracted, spanning the entirety of the Early Triassic and possibly longer. Numerous studies from the low-latitude Paleotethys and high-latitude Boreal oceans have examined the possible link between ocean chemistry changes and the end-Permian mass extinction. However, redox chemistry changes in the Panthalassic Ocean, comprising ∼85-90% of the global ocean area, remain under debate. Here, we report multiple S-isotopic data of pyrite from Upper Permian-Lower Triassic deepsea sediments of the Panthalassic Ocean, now present in outcrops of western Canada and Japan. We find a sulfur isotope signal of negative Δ S anomaly with the extinction horizon in western Canada suggests that shoaling of H 2 S-rich waters may have driven the end-Permian mass extinction. Our data also imply episodic euxinia and oscillations between sulfidic and oxic conditions during the earliest Triassic, providing evidence of a causal link between incursion of sulfidic waters and the delayed recovery of the marine ecosystem.end-Permian mass extinction | Panthalassic Ocean | multiple sulfur isotopes | sulfidic waters T he end-Permian mass extinction was the largest biotic catastrophe of the last 540 million years, resulting in the disappearance of >80% of marine species, and a full biotic recovery did not occur until 4-8 million years after the extinction event (1-6). Several lines of evidence from the low paleolatitude Paleotethys and high paleolatitude Boreal oceans, which accounted for ∼10-15% of the contemporaneous global ocean area, suggest that sulfidic (H 2 S-rich) conditions may have developed widely during the end-Permian extinction (7-13). However, redox chemistry changes in the Panthalassic Ocean, comprising ∼85-90% of the global ocean area, remain controversial, with competing hypotheses proposing extensive deepwater anoxia ("superanoxic ocean") or suboxic deep waters in combination with spatially constrained thermocline anoxia (14-18). Evidently, redox chemistry changes in the Panthalassic Ocean are central to an examination of the links between global-ocean conditions and the end-Permian extinction event as well as the subsequent delayed biotic recovery.The preservation of Permian-Triassic boundary deep-sea sediments is limited because most oceanic crust of that age has been subducted, and the only surviving Panthalassic seafloor sediments are within accretionary terranes or marginal uplifts

The Wa'ergang section in South China has been proposed as a potential Global Stratotype Section and Point (GSSP) for the base of Stage 10, the uppermost stage of the Cambrian System. In this study, high-resolution C-isotopic compositions are reported and we identified three large negative δ13C excursions, namely N1, N2 and N3, at Wa'ergang. The N1 is located just above the First Appearance Datum (FAD) of Lotagnostus americanus, corresponding to the possible base of the Proconodontus posterocostatus conodont Zone. The N2 was identified within the Micragnostus chuishuensis trilobite Zone and the Proconodontus muelleri conodont Zone. The N3 is located in the lowermost part of the Leiagnostus cf. bexelli – Archaeuloma taoyuanense trilobite Zone or Eoconodontus conodont Zone. The N1 and N2 can be correlated with the negative δ13C excursions preceding the Top of Cambrian Carbon Isotope Excursion (TOCE) observed globally. The N3 can be correlated with the TOCE or the HEllnmaria–Red Tops Boundary (HERB) Event. The inter-basinal correlation of N1 and L. americanus strongly supports that the base of Stage 10 may be best defined by the FAD of L. americanus. We also used a box model to quantitatively explore the genesis of the negative δ13C excursions from South China. Our numerical simulations suggest that weathering of the organic-rich sediments on the platform, probably driven by intermittent sea level fall and/or the oxygenation of the Dissolved Organic Carbon (DOC) reservoir in seawater, may have contributed to the generation of the negative δ13C excursions observed in the Stage 10 at Wa'ergang in South China.

Organic-rich Cretaceous source rocks of the petroliferous Songliao Basin in northeast China are considered to be lacustrine in origin, but paleontological and organic geochemical evidence suggest episodic marine incursions. As a test of this hypothesis, we applied time-series measurements of elemental and isotopic abundances on core and cutting samples to evaluate fluctuations in the sulfur and carbon cycles across the Santonian-Campanian transition preserved in the upper Yaojia and lower Nenjiang formations. The data reveal a spike in pyrite sulfur abundance and a marked negative excursion in δ 34 S at the base of the Nenjiang Formation when the basin expanded to its maximal extent. The elemental and isotopic data suggest that flooding was associated with rapid marine transgression that enhanced sulfate concentrations, which promoted microbial sulfate reduction in anoxic bottom waters that were episodically euxinic. Subsequent restriction of the basin and a decline in marine influence is supported by progressive upsection 34 S enrichment (up to 30‰) in Nenjiang Member I, which are interpreted to reflect the distillation of sulfate through enhanced pyrite burial, followed by a gradual return to lacustrine conditions that prevailed in overlying strata.

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