Table_1_Depositional control on the sulfur content and isotope of sedimentary pyrite from the southeast coast of China since MIS5.xlsx

The content and isotopic composition of pyrite sulfur are significantly affected by local depositional conditions and are sensitive to environmental evolution. Here, we use core QK11, collected from Xiapu Bay, southeast coast of China, to reveal how local depositional conditions constrained pyrite formation and sulfur isotopic composition since MIS5. Our results show that the content of pyrite sulfur is mainly controlled by the TOC content during interglacial intervals and is limited by the supplement of sulfate in glacial intervals. Therefore, the C/S ratios can effectively identify three transgressions since MIS5. The sulfur isotopic composition of pyrite ranges from -36.7 to 18.4‰ in the whole core. The occurrence of isotopically “heavy” pyrite is observed at the depth of 2.2~9.2, 27.2~33.8, and 43.5~62.5 mbsf, which is attributed to the influence of sulfate reservoir effect, depositional event, unsteady diagenetic environment, and other factors, highlighting the influence of local depositional and diagenetic processes on the isotopic composition of pyrite sulfur. Pyrite sulfur in other layers is generally depleted in 34S, as low as -36.7‰, indicating that the early-stage organiclastic sulfate reduction (OSR) plays an important role in sulfur isotopic fractionation. The results also suggest that organic carbon indicators (TOC/TN ratio and δ13C) combined with the C/S ratio can effectively distinguish between freshwater and marine environments, which is of great significance to reveal depositional evolution in deep time.

吡啶硫含量及其同位素组成受局部沉积条件的影响显著，对环境演变反应灵敏。本研究采用从中国东南沿海霞浦湾采集的QK11岩芯，揭示自 MIS5 以来局部沉积条件对吡啶硫形成及其同位素组成的影响。研究结果表明，间冰期中吡啶硫含量主要受有机碳含量（TOC）的控制，而冰期则受硫酸盐补充的限制。因此，C/S 比率可以有效识别 MIS5 以来的三次海侵。全岩芯中吡啶硫同位素组成介于 -36.7‰ 至 18.4‰ 之间。同位素“重”的吡啶硫在深度 2.2~9.2 m、27.2~33.8 m 和 43.5~62.5 mbsf 处出现，这归因于硫酸盐库效应、沉积事件、不稳定的成岩环境等因素的影响，突显了局部沉积和成岩过程对吡啶硫同位素组成的制约。其他层位的吡啶硫通常富含 34S，低至 -36.7‰，表明早期有机质硫酸盐还原（OSR）在硫同位素分馏中发挥着重要作用。研究还表明，有机碳指标（TOC/TN 比率和 δ13C）与 C/S 比率的结合，可以有效区分淡水和海洋环境，这对揭示深时沉积演化具有重要意义。