The role of volcanism as a driver of climate change remains widely debated. Following the end-Permian mass extinction, the protracted Early Triassic recovery interval was characterized by extreme climatic and environmental perturbations (hyperwarming, intense subaerial weathering, and extensive marine euxinia) and large carbon- and sulfur-cycle perturbations. Although a magmatic trigger is widely accepted, details regarding the timing and magnitude of degassing and its relationship to contemporaneous climate changes remain poorly understood. In this study, we present new paired carbonate δ¹³C and carbonate-associated-sulfate δ³⁴S data from deep-water settings in the Lower Triassic of South China to evaluate these issues. Our dataset reveals large positive shifts of both proxies across the Smithian/Spathian boundary (SSB), recording globally synchronous changes in the C and S cycles linked to co-burial of large quantities of organic matter and pyrite. Biogeochemical modeling of the C-S cycles shows that massive carbon release linked to increased magmatic degassing can account for observations of concurrent positive shifts of δ³⁴S and δ¹³C, enhanced weathering, expanded marine euxinia, and the Late Smithian Thermal Maximum (LSTM). Measured increases in δ¹³C (+3.2 ± 1.6‰) and δ³⁴S (+7.3 ± 2.3‰) across the SSB relative to their baseline values are consistent with a major magmatic degassing event during the Early to Middle Smithian, whose magnitude and rate we estimate at ~78,000 ± 13,000 Gt C and 0.26 Gt C yr⁻¹, respectively. Our results provide evidence that Early–Middle Smithian degassing was the primary trigger of the LSTM and concurrent biotic crisis.

火山活动作为气候变化驱动因素的作用仍然存在广泛争议。在二叠纪末大规模灭绝之后，漫长的早三叠世恢复期的特点是极端气候和环境扰动（超温、强烈的陆上风化和广泛的海洋euxinia）和大的碳和硫循环扰动。尽管岩浆触发被广泛接受，但关于脱气的时间和幅度及其与同期气候变化的关系的细节仍然知之甚少。在这项研究中，我们提出了新的配对碳酸盐 δ ¹³ C 和碳酸盐缔合硫酸盐 δ ³⁴来自华南下三叠统深水环境的 S 数据来评估这些问题。我们的数据集揭示了两个代理在 Smithian/Spathian 边界 (SSB) 上的巨大正向变化，记录了与大量有机物和黄铁矿共埋相关的 C 和 S 循环的全球同步变化。CS 循环的生物地球化学模型表明，与岩浆脱气增加相关的大量碳释放可以解释同时观测到的 δ ³⁴ S 和 δ ¹³ C、增强的风化作用、扩大的海洋 euxinia 和晚期史密斯热最大值 (LSTM)。^{δ 13} C (+3.2 ± 1.6‰) 和 δ ³⁴的测量值增加SSB（+7.3 ± 2.3‰）相对于它们的基线值与早到中史密世期间的一次主要岩浆脱气事件一致，我们估计其幅度和速率为 ~78,000 ± 13,000 Gt C 和 0.26 Gt C yr ^{- 1}，分别。我们的研究结果提供了证据，表明早期-中期史密斯脱气是 LSTM 和并发生物危机的主要触发因素。