The delivery of organic carbon (OC) to the ocean's deepest trenches in the hadal zone is poorly understood, but may be important for the carbon cycle, contain crucial information on sediment provenance and event-related transport processes, and provide age constraints on stratigraphic sequences in this terminal sink. In this study, we systematically characterize bulk organic matter (OM) and OC signatures (TOC/TN, ${\delta }^{13}$C, ¹⁴C), as well as those from application of serial thermal oxidation (ramped pyrolysis/oxidation) of sediment cores recovered along an entire hadal trench encompassing high stratigraphic resolution records spanning nearly 2000 years of deposition. We analyze two cores from the southern and northern Japan Trench, where submarine canyon systems link shelf with trench. We compare results with previously published data from the central Japan Trench, where canyon systems are absent. Our analyses enable refined dating of the stratigraphic record and indicate that event deposits arise from remobilization of relatively surficial sediment coupled with deeper erosion along turbidity current pathways in the southern and central study site and from canyon flushing events in the northern study site. Furthermore, our findings indicate deposition of predominantly marine OC within hemipelagic background sediment as well as associated with event deposits along the entire trench axis. This implies that canyon systems flanking the Japan Trench do not serve as a short-circuit for injection of terrestrial OC to the hadal zone, and that tropical cyclones are not major agents for sediment and carbon transfer into this trench system. These findings further support previous Japan Trench studies interpreting that event deposits originate from the landward trench slope and are earthquake-triggered. The very low terrestrial OC input into the Japan Trench can be explained by the significant distance between trench and hinterland (>180 km), and the physiography of the canyons that do not connect to coast and river systems. We suggest that detailed analyzes of long sedimentary records are essential to understand OC transfer, deposition and burial in hadal trenches.

很难理解将有机碳（OC）输送到海底带最深的海沟中的方法，但对于碳循环可能很重要，它包含有关沉积物来源和与事件有关的运输过程的重要信息，并提供地层序列的年龄限制在此终端接收器中。在这项研究中，我们系统地表征了大块有机物（OM）和OC签名（TOC / TN，${\delta }^{13}$C，¹⁴C），以及通过应用连续热氧化（倾斜热解/氧化）沿整个海沟挖出的沉积物芯所产生的沉积物，这些沉积物涵盖了跨越近2000年沉积的高地层分辨率记录。我们分析了日本海沟南部和北部的两个岩心，海底峡谷系统将海底峡谷系统与海沟相连接。我们将结果与缺少峡谷系统的日本中部海沟的先前发布的数据进行了比较。我们的分析能够对地层记录进行精确的测年，并表明事件沉积源于相对较浅的沉积物的迁移，再加上南部和中部研究区沿浊流路径的更深侵蚀，以及北部研究区的峡谷冲刷事件。此外，我们的发现表明，半海洋背景沉积物中主要为海洋OC沉积，并且与整个海沟轴上的事件沉积有关。这意味着，位于日本海沟旁的峡谷系统不会作为将陆地OC注入到海区的短路，热带气旋并不是将沉积物和碳转移到该海沟系统的主要因素。这些发现进一步支持了先前的日本海沟研究，该研究认为事件沉积物来自陆上沟渠坡度，并且是地震触发的。进入日本海沟的地面OC输入量非常低，这可以通过以下方式来解释：海沟和腹地之间的距离很大（> 180 km），以及不与海岸和河流系统连接的峡谷的地貌。