Abstract The end-Triassic extinction is one of the major Phanerozoic mass extinctions and it appears to have been linked to coeval rapid and severe environmental change, thought to be triggered by volcanism in the Central Atlantic Magmatic Province (CAMP). However, direct stratigraphic evidence to substantiate this linkage and to help develop scenarios for the cascade of events is still scarce. Mercury is an increasingly widely used proxy to trace the volcanic activity associated with large igneous provinces (LIPs) in distal sedimentary sections, but so far Hg records are available from only a handful of Triassic–Jurassic boundary (TJB) sections. One of the few well-studied marine sedimentary sections with a continuous sedimentary record across the TJB is located at Csővar (Hungary) and it exposes an extended succession of carbonates deposited in an intraplatform basin on the western Tethyan shelf. Previously, this section yielded one of the first convincing records of carbon isotope excursions (CIEs) across the TJB, albeit from low-resolution sampling. Here we report a new, high-resolution δ13Ccarb curve, supplemented with Hg measurements. A series of successive negative carbon isotope excursions (termed NCIE-1 to 6) attests to carbon cycle perturbations in the TJB interval. Four excursions appear significant after statistical smoothing. Of these, NCIE-3 exhibits the highest amplitude and is biostratigraphically constrained to the topmost Triassic, hence reliably correlated with the initial CIE, a globally recognised excursion closely preceding the TJB, and coincident with the end-Triassic extinction (ETE) horizon. The Hg concentration data provide the longest record available to date from a single section across the TJB. It shows very low values below NCIE-3 that are interpreted as the pre-volcanic background, followed by a prominent Hg peak that is nearly coincident with the most significant carbon isotope spike (NCIE-3). The slight lag suggests that onset of a major extrusive phase of CAMP (marked by a significant rise in Hg) closely followed the very onset of carbon cycle perturbation at that time (expressed by an abrupt change in the δ13Ccarb signal), possibly from biogenic methane release. Subsequent and recurring smaller Hg psuggest a pulsatory nature of prolonged volcanic activity. Organic content in the section is consistently low and sedimentary Hg concentrations are therefore normalized against Fe content, a reliable proxy in the lack of significant lithological changes. The maximum sedimentary Hg concentration at Csővar is greater than that in any other TJB section, although not unprecedented if other events are considered. Three hypotheses are explored to explain the high values; i) the hit-or-miss model could suggest that deposition of the sampled beds was fortuitously coincident with major eruptions, ii) the presence and preservation of cryptotephra could account for the unusually high sedimentary Hg enrichment, and iii) changes in the proportion of Hg-carrier phases throughout the studied succession, e.g. from magnetite to pyrite dominance, could have enhanced the potential of Hg capture and deposition. Collectively, the new data provide direct stratigraphic and geochemical evidence for the link between CAMP volcanism and carbon cycle perturbations and strengthen the case of their causal relationship with the end-Triassic extinction.

中文翻译：

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西特提斯 Csővár 部分的汞异常和碳同位素偏移支持 CAMP 火山活动与三叠纪末灭绝之间的联系

摘要 三叠纪末大灭绝是显生宙主要的大灭绝之一，它似乎与同时期快速而严重的环境变化有关，被认为是由中大西洋岩浆省 (CAMP) 的火山活动引发的。然而，证实这种联系并帮助制定事件级联情景的直接地层证据仍然很少。汞是一种越来越广泛使用的替代物，用于追踪与远端沉积剖面中大型火成岩省 (LIP) 相关的火山活动，但到目前为止，只有少数三叠纪-侏罗纪边界 (TJB) 剖面可以获得汞记录。为数不多的在 TJB 上具有连续沉积记录的海相沉积剖面之一位于 Csővar（匈牙利），它暴露了沉积在特提斯大陆架西部台内盆地中的一系列碳酸盐岩。此前，该部分产生了第一个令人信服的跨 TJB 碳同位素偏移 (CIE) 记录，尽管来自低分辨率采样。在这里，我们报告了一条新的高分辨率 δ13Ccarb 曲线，并辅以 Hg 测量值。一系列连续的负碳同位素偏移（称为 NCIE-1 到 6）证明了 TJB 间隔中的碳循环扰动。统计平滑后，四次偏移显得显着。其中，NCIE-3 表现出最高的振幅，并且在生物地层学上被限制在最顶部的三叠纪，因此与初始 CIE 可靠相关，这是一个全球公认的紧邻 TJB 的偏移，并与三叠纪末灭绝 (ETE) 地平线重合。汞浓度数据提供了迄今为止来自 TJB 单个部分的最长记录。它显示低于 NCIE-3 的非常低的值，被解释为火山前背景，随后是一个突出的 Hg 峰，几乎与最重要的碳同位素峰值 (NCIE-3) 重合。轻微的滞后表明 CAMP 的主要喷出阶段的开始（以 Hg 的显着增加为标志）紧随当时碳循环扰动的开始（通过 δ13Ccarb 信号的突然变化表示），可能来自生物甲烷释放。随后和反复出现的较小汞表明长期火山活动具有脉动性质。该剖面中的有机物含量始终较低，因此沉积汞浓度相对于铁含量进行了标准化，这是缺乏显着岩性变化的可靠代表。Csővar 的最大沉积汞浓度高于任何其他 TJB 剖面，尽管如果考虑其他事件，这并非前所未有。探索了三个假设来解释高值；i) 命中或未命中模型可能表明采样床的沉积偶然与大爆发同时发生，ii) 隐藻的存在和保存可以解释异常高的沉积 Hg 富集，以及 iii) 比例的变化在整个研究序列中的汞载体相，例如从磁铁矿到黄铁矿的优势，可能增强了汞捕获和沉积的潜力。集体，