Abstract The Early Jurassic Toarcian oceanic anoxic event (T-OAE) is characterized by an extinction event, a major sea-level rise, enhanced marine primary productivity, elevated seawater temperatures, widespread deposition of organic-rich sediments, and a negative carbon-isotope excursion (CIE). However, the T-OAE exhibits significant interregional variation in its expression, with strong spatial variation in lithology, total organic carbon (TOC) content, and the magnitude of the negative CIE in both carbonate and organic carbon profiles. It is better developed as a distinct geological event on the Northwest European Shelf (NWES), exhibiting both a large organic CIE (to –5 to –7 ‰) and high TOC content (to ~10 %), than in other regions globally. The reason for the regionally variable expression of the T-OAE has been a matter of debate, with models based on both regional and global factors proposed. We review these models in the context of the global sedimentary record of the T-OAE. The T-OAE records a global carbon-cycle perturbation that has been linked to Karoo-Ferrar Large Igneous Province magmatism, suggesting that volcanic emissions of greenhouse gases were the main cause of contemporaneous paleoenvironmental changes. Increases in seawater temperature have been documented only on the NWES to date, although lithologic and geochemical evidence of enhanced chemical weathering intensities is transregional. Mercury (Hg) enrichments are found mainly in shallow-marine settings, and their provenance in volcanic emissions remains uncertain. The exceptional expression of the T-OAE on the NWES points to regional oceanographic factors in the development of watermass stratification, deepwater anoxia, and enhanced organic matter accumulation. At a global scale, shifts toward more reducing oceanic redox conditions were spatially variable, and the T-OAE may therefore be more widely recognizable by its negative CIE than by paleo-environmental redox changes.

中文翻译：

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Toarcian（早侏罗世）期间的碳循环变化以及对 Toarcian 海洋缺氧事件的区域与全球驱动因素的影响

摘要 早侏罗世 Toarcian 海洋缺氧事件 (T-OAE) 的特征是灭绝事件、海平面大幅上升、海洋初级生产力增强、海水温度升高、富含有机物沉积物的广泛沉积和负碳同位素远足（CIE）。然而，T-OAE 在其表达上表现出显着的区域间变化，在岩性、总有机碳 (TOC) 含量以及碳酸盐和有机碳剖面中负 CIE 的大小方面具有强烈的空间变化。它在西北欧大陆架 (NWES) 上作为一个独特的地质事件发展得更好，与全球其他地区相比，它表现出较大的有机 CIE（至 –5 至 –7 ‰）和高 TOC 含量（至约 10 %）。T-OAE 的区域变量表达的原因一直是一个有争议的问题，提出了基于区域和全球因素的模型。我们在 T-OAE 的全球沉积记录的背景下审查这些模型。T-OAE 记录了与 Karoo-Ferrar 大型火成岩省岩浆作用有关的全球碳循环扰动，表明火山排放的温室气体是同期古环境变化的主要原因。迄今为止，仅在 NWES 上记录了海水温度的升高，尽管化学风化强度增强的岩性和地球化学证据是跨区域的。汞 (Hg) 富集主要存在于浅海环境中，它们在火山排放中的来源仍不确定。NWES 上 T-OAE 的异常表现表明区域海洋学因素影响了水团分层的发展，深水缺氧，增强有机质积累。在全球范围内，向更多减少海洋氧化还原条件的转变在空间上是可变的，因此 T-OAE 的负 CIE 可能比古环境氧化还原变化更容易识别。