Multi-proxy geochemical records of the Middle Cenomanian Event in the Xigaze forearc basin: Implications for methane seepage in a restricted marginal sea

Oceanic anoxic events (OAEs) represent abrupt perturbations of the global carbon cycle, characterized by widespread bottom-water anoxia and the transient yet globally extensive deposition of organic-rich black shales. Moreover, the substantial release of methane into the ocean–atmosphere system can significantly exacerbate environmental deterioration during OAEs, thereby promoting organic matter burial. However, the specific processes and feedback mechanisms coupling OAEs and methane seepage remain poorly constrained. In this study, we investigate host rocks, embedded carbonate concretions, and pyrite enclosed within these concretions from a representative Middle to Late Cenomanian section in the Xigaze forearc basin to identify the occurrence of an OAE and further evaluateits interrelationship with methane seepage.海洋缺氧事件（Oceanic anoxic events, OAEs）指全球碳循环的突发性扰动，其典型特征为广泛分布的底层水缺氧环境，以及短时且全域覆盖的富有机质黑色页岩沉积。此外，大量甲烷向海-气系统的释放会显著加剧海洋缺氧事件期间的环境恶化，进而促进有机质埋藏。然而，耦合海洋缺氧事件与甲烷渗漏的具体过程及反馈机制仍缺乏精准约束。本研究选取日喀则弧前盆地一处典型的森诺曼期中晚期地层剖面，对其宿主岩石、赋存其中的碳酸盐结核以及结核内部包裹的黄铁矿开展研究，以识别海洋缺氧事件的发生，并进一步评估其与甲烷渗漏之间的相互关系。