Volcanic-driven nutrient flux to the oceans stimulated marine productivity and organic matter burial during Oceanic Anoxic Event 2 (OAE2; ~94 million years ago). While the preferential burial of ¹³C-depleted organic matter led to a general ¹³C enrichment of sediments during the event, a 2‰ ¹³C depletion punctuated the first half of the event (known as the Plenus), raising questions about carbon cycle feedbacks during OAE2. Here we present organic geochemical evidence (for example, pyrogenic polycyclic aromatic hydrocarbons) from the Western Interior Seaway that indicates increased forest fire frequency in the western United States during the Plenus. Carbon mass balance equations, which account for the amount and carbon isotopic composition of atmospheric CO₂ and forest biomass during OAE2, potentiate fires in the western United States as part of a widespread increase in forest fires that could have alone caused the global 2‰ ¹³C depletion during the Plenus. Plant biomarkers suggest that local precipitation and plant type did not change significantly, indicating that elevated atmospheric oxygen levels from widespread organic carbon burial increased the frequency of fires in wet forest ecosystems that were extensive during OAE2. Plant biomarkers also indicate that forest fires amplified the flux of terrestrial organic matter and nutrients to the oceans, which may have enhanced marine productivity, organic carbon burial and the return to ¹³C-enriched sediments at the end of the Plenus. The extent that this feedback impacted global biogeochemistry during the Plenus and the rest of OAE2, as well as other events in Earth history, warrants further investigation.

火山驱动的营养物向海洋的通量刺激了海洋缺氧事件2（OAE2；〜9400万年前）的海洋生产力和有机物埋葬。虽然优先埋葬贫¹³ C的有机物导致事件期间沉积物的总体富集¹³ C，但事件的前半部分（称为Plenus）击穿2‰ ¹³ C的耗费，引发了有关碳循环反馈的问题在OAE2中。在这里，我们介绍了来自西部内陆海道的有机地球化学证据（例如，热解多环芳烃），表明全美期间美国西部森林火灾的频率增加。碳质量平衡方程式，说明大气中一氧化碳的含量和碳同位素组成₂和OAE2期间的森林生物量，美国西部森林大火加剧，这是森林大火的一部分，仅此一项就可能导致全盛期间全球2‰ ¹³ C的消耗。植物生物标志物表明，当地的降水和植物类型没有明显变化，表明广泛的有机碳埋藏增加了大气中的氧气水平，增加了在OAE2时期广泛的湿润森林生态系统中的火灾频率。植物生物标志物还表明，森林大火加剧了陆地有机物质和养分向海洋的流动，这可能提高了海洋生产力，掩埋有机碳并恢复了¹³脾的末端富含C的沉积物。这种反馈影响了在斑节时期和OAE2其余时间的全球生物地球化学的程度，以及地球历史上的其他事件，值得进一步研究。