Contrasting sensitivity of weathering proxies to Quaternary climate and sea-level fluctuations on the southern slope of the South China Sea

Tropical marginal seas host important sedimentary archives that may be exploited to reveal past changes in continental erosion, chemical weathering, and ocean dynamics. However, these records can be challenging to interpret due to the complex interactions between climate and particulate transport across ocean margins. For the southern South China Sea over the last 90 kyr, we observe a contrasting temporal relationship between the deposition of clay minerals and magnetic minerals, which were associated with two different hydrodynamic modes. Fine-grained clay minerals can be carried in suspension by ocean currents, leading to a rapid response to regional climate-driven inputs. In contrast, changes in magnetic mineralogy were linked to glacial-interglacial sea-level variability, from which we infer a control by bedload transport and resuspension. Overall, this study indicates that the transfer pathways and mechanisms imparted by varying hydrodynamic conditions exert a substantial influence on the distribution of terrigenous material in continental margin sediments.热带边缘海蕴藏着关键的沉积记录（sedimentary archives），可用于揭示大陆侵蚀、化学风化与海洋动力系统的古演化过程。然而，受气候与大洋边缘颗粒物输运之间复杂相互作用的影响，这类记录的解译颇具挑战。针对过去90 kyr的南海南部区域，我们发现黏土矿物与磁性矿物的沉积过程呈现截然相反的时间演化关系，二者分别对应两种不同的水动力模式。细粒黏土矿物可通过洋流以悬浮态输运，因此对区域气候驱动的物质输入响应迅速。与之相反，磁性矿物学（magnetic mineralogy）特征的变化则与冰期-间冰期海平面波动相关，据此我们推断其受控于推移质输运与沉积物再悬浮过程。综上，本研究表明，不同水动力条件所塑造的输运路径与机制，对大陆边缘沉积物中的陆源物质（terrigenous material）分布具有显著调控作用。