Abstract The mechanisms leading to environmental and climate change prior to and anticipating the well-studied Toarcian oceanic anoxic event are not completely understood. Specifically, the role of the continuing break-up of Pangea, associated palaeogeographic rearrangements, and the influence of volcanic activity are less well known. Therefore, we studied the Pliensbachian interval in the open marine, hemipelagic section of the Breggia Gorge in southern Switzerland, to elucidate the potential impact of these major changes on the environment and climate. We identified carbon isotope excursions towards lower values in whole-rock carbonates dated from the Sinemurian/Pliensbachian boundary, davoei, margaritatus, and spinatum Zones, and possibly from the Pliensbachian-Toarcian boundary. Using the whole-rock oxygen isotope record and phosphorus content, we associated these events with phases of increased runoff possibly related to climate warming. We also established the first mercury (Hg) record for the entire Pliensbachian, and in order to verify its validity, we analysed an additional section located along the Dorset coast in southern England. The presence of Hg spikes common in both sections may indicate the influence of episodes of increased volcanic activity. The Hg spike during the earliest Pliensbachian may coincide with a late phase of the central Atlantic magmatic province, and/or increased rifting linked with the opening of the Hispanic corridor. Further significant maxima in Hg contents are observed within the davoei and margaritatus Zones, and both phases may correspond to early volcanic activity of the Karoo-Ferrar large igneous province. Further analyses are, however, needed to corroborate this interpretation and evaluate the importance of organic-matter scavenging and detrital input in comparison to volcanic activity.

中文翻译：

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Pliensbachian 环境扰动及其与火山活动的潜在联系：瑞士和英国地球化学记录

摘要 在经过充分研究的 Toarcian 海洋缺氧事件之前和预期导致环境和气候变化的机制尚不完全清楚。具体而言，盘古大陆持续分裂的作用、相关的古地理重排以及火山活动的影响鲜为人知。因此，我们研究了瑞士南部 Breggia 峡谷开阔海洋半远洋部分的 Pliensbachian 区间，以阐明这些重大变化对环境和气候的潜在影响。我们在 Sinemurian/Pliensbachian 边界、davoei、margaritatus 和 spinatum 带以及可能来自 Pliensbachian-Toarcian 边界的全岩碳酸盐中确定了碳同位素向较低值的偏移。利用全岩氧同位素记录和磷含量，我们将这些事件与可能与气候变暖有关的径流增加阶段联系起来。我们还建立了整个 Pliensbachian 的第一个汞 (Hg) 记录，为了验证其有效性，我们分析了位于英格兰南部多塞特海岸的附加部分。两个部分中常见的汞峰值的存在可能表明火山活动增加的事件的影响。最早的 Pliensbachian 期间的 Hg 峰值可能与大西洋中部岩浆区的晚期阶段相吻合，和/或与西班牙走廊的开放相关的裂谷增加。在 davoei 和 margaritatus 带中观察到汞含量的进一步显着最大值，这两个阶段可能对应于 Karoo-Ferrar 大型火成岩省的早期火山活动。然而，进一步的分析是，