Abstract Marine shales, the most common lithology in the stratigraphic record, represent an archive of long-term changes in sediment production, weathering intensity, and seawater chemistry through Earth history whose potential has been underexploited to date. In this study, we compiled compositional data for 14,531 samples from 268 shale and mud units ranging in age from the early Cryogenian (840 Ma) to the Recent. We examined secular variation in the Al-normalized concentrations of ten elements (Mg, Na, K, Ba, Sr, Y, Th, Rb, Nb, and Zr) selected for (1) their presence in typical X-ray fluorescence (XRF) datasets (thus providing sufficient data), and (2) their lack of redox sensitivity (thus excluding elements whose primary control is aqueous redox conditions). Relationships among the study elements were quantified using principal component analysis (PCA) and cluster analysis (CA), revealing several significant groupings: (1) a subset of “detrital elements” (K, Rb, Th, Nb, Y, and Zr) whose concentrations are primarily controlled by subaerial weathering processes; (2) a subset of “hydrogenous elements” (Mg, Na, and Sr) whose concentrations are significantly influenced by seawater chemistry, and (3) Ba, which is subject to multiple controls. The dominant influence on the detrital elements appears to have been not chemical weathering intensity per se but the ratio of Al-poor silt to Al-rich clay in the particulate weathering flux. Although possibly modulated by factors such as climate and land plant evolution, silt:clay ratios appear most closely linked to tectonism, with higher values associated with major orogenic events. The concentrations of the hydrogenous elements in marine shales were likely related to their seawater inventories, which were modulated at long time scales by rates of submarine hydrothermal alteration. Ba in marine shales may have been significantly influenced by atmospheric pO2 and seawater sulfate levels via their control of barite saturation in seawater. In summary, our findings document significant relationships of marine shale composition to first-order geological controls, suggesting that long-term secular changes in sediment and seawater chemistry can be reconstructed from fine-grained siliciclastic sediments.

中文翻译：

---

840 Ma以来海相页岩元素组成的长期变化：构造和海水影响

摘要 海相页岩是地层记录中最常见的岩性，代表了地球历史上沉积物产生、风化强度和海水化学的长期变化档案，其潜力迄今为止尚未得到充分利用。在这项研究中，我们编制了 14,531 个样本的成分数据，这些样本来自 268 个页岩和泥浆单元，年龄从早期低温纪 (840 Ma) 到近代。我们检查了 10 种元素（Mg、Na、K、Ba、Sr、Y、Th、Rb、Nb 和 Zr）的 Al 归一化浓度的长期变化，这些元素被选择为 (1) 它们在典型 X 射线荧光 (XRF) 中的存在) 数据集（因此提供了足够的数据），以及（2）它们缺乏氧化还原敏感性（因此排除了主要控制是水性氧化还原条件的元素）。研究元素之间的关系使用主成分分析 (PCA) 和聚类分析 (CA) 进行量化，揭示了几个重要的分组：(1) “碎屑元素”的子集（K、Rb、Th、Nb、Y 和 Zr）其浓度主要受地下风化过程控制；(2) “氢元素”(Mg、Na 和 Sr) 的子集，其浓度受海水化学的显着影响，以及 (3) Ba，受多重控制。对碎屑元素的主要影响似乎不是化学风化强度本身，而是颗粒风化通量中贫铝粉砂与富铝粘土的比例。虽然可能受气候和陆地植物进化等因素的调节，但淤泥与粘土的比例似乎与构造作用最密切相关，与主要造山事件相关的较高值。海相页岩中含氢元素的浓度可能与它们的海水存量有关，后者在很长一段时间内受到海底热液蚀变速率的调节。通过控制海水中的重晶石饱和度，海洋页岩中的 Ba 可能受到大气 pO2 和海水硫酸盐水平的显着影响。总之，我们的研究结果记录了海相页岩成分与一级地质控制的重要关系，表明可以从细粒硅质碎屑沉积物中重建沉积物和海水化学的长期长期变化。受海底热液蚀变速率的长期调节。通过控制海水中的重晶石饱和度，海洋页岩中的 Ba 可能受到大气 pO2 和海水硫酸盐水平的显着影响。总之，我们的研究结果记录了海相页岩成分与一级地质控制的重要关系，表明可以从细粒硅质碎屑沉积物中重建沉积物和海水化学的长期长期变化。受海底热液蚀变速率的长期调节。通过控制海水中的重晶石饱和度，海洋页岩中的 Ba 可能受到大气 pO2 和海水硫酸盐水平的显着影响。总之，我们的研究结果记录了海相页岩成分与一级地质控制的重要关系，表明可以从细粒硅质碎屑沉积物中重建沉积物和海水化学的长期长期变化。