The Carnian Pluvial Episode (CPE, ∼233 Ma) was characterized by multiple negative carbon-isotope excursions, turnovers in marine and terrestrial biota, and a Tethys-wide humid climate accompanied by abundant terrigenous sediment and freshwater input into sedimentary basins. A general temporal coincidence between the CPE and the emplacement of the Wrangellia Large Igneous Province (Wrangellia LIP) has been well documented, however, it remains unclear whether fluctuations in the intensity of the LIP's activity could be linked to the biotic and climate changes at the CPE. We here present mercury (Hg) concentration and isotope ratio records from a pelagic deep-water succession (Section N-O, Inuyama, Japan) that encompasses the CPE interval. Data reveal concurrent peaks in the Hg concentrations and ratios of Hg to TOC and enrichment factors ThEF、Al EF、Zn EF和 Ni EF表明在 CPE 硅碎屑输入之前,沉积物中发生了过量的 Hg 加载,这可能是由于火山活动造成的。此外,Hg 值显示 Julian 1 和 Julian 2 之间边界的负偏移,随后在 Julian/Tuvalian 过渡处正偏移到接近零的值。接近零Julian/Tuvalian 边界的 Hg 值与 Hg 和 Cu 负载的增加有关,表明火山 Hg 和 Cu 输入的峰值可能表明兰格利亚 LIP 活动达到高潮。最值得注意的是,朱利安/图瓦利过渡是碳酸盐岩平台演化、生物更替和与该事件相关的气候变化最显着变化的证据。因此,我们的结果表明,在 CPE 期间,LIP 火山活动强度的变化可能在推动生物和气候变化方面发挥了重要作用。我们的结果为与 LIPs(例如,二叠纪末期)相关的其他大规模灭绝事件提供了一个模型,其中低强度背景火山活动被高强度脉冲打断,后者才是真正的杀手。
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Climax in Wrangellia LIP activity coincident with major Middle Carnian (Late Triassic) climate and biotic changes: Mercury isotope evidence from the Panthalassa pelagic domain
The Carnian Pluvial Episode (CPE, ∼233 Ma) was characterized by multiple negative carbon-isotope excursions, turnovers in marine and terrestrial biota, and a Tethys-wide humid climate accompanied by abundant terrigenous sediment and freshwater input into sedimentary basins. A general temporal coincidence between the CPE and the emplacement of the Wrangellia Large Igneous Province (Wrangellia LIP) has been well documented, however, it remains unclear whether fluctuations in the intensity of the LIP's activity could be linked to the biotic and climate changes at the CPE. We here present mercury (Hg) concentration and isotope ratio records from a pelagic deep-water succession (Section N-O, Inuyama, Japan) that encompasses the CPE interval. Data reveal concurrent peaks in the Hg concentrations and ratios of Hg to TOC and enrichment factors ThEF, AlEF, ZnEF, and NiEF implying that excess Hg loading in the sediments occurred, likely due to volcanic activity, prior to the CPE siliciclastic input. Furthermore, Hg values show a negative shift across the boundary between the Julian 1 and Julian 2, followed by a positive shift up to near-zero values at the Julian/Tuvalian transition. The near-zero Hg values at the Julian/Tuvalian boundary are associated with an increase in Hg and Cu loading, suggesting a peak of volcanogenic Hg and Cu input that may indicate a climax in the Wrangellia LIP activity. Most notably, the Julian/Tuvalian transition is where evidence of the most pronounced changes in carbonate platform evolution, biological turnover and climate change associated with the event has been highlighted. Our results therefore suggest that variations in the intensity of LIP volcanism may have played a major role in driving biotic and climate changes during the CPE. Our results provide a model for other mass extinction events associated with LIPs (e.g., the end-Permian) where low-intensity background volcanism was punctuated by high-intensity pulses, these latter being the real killers.