Disentangling Combined Effects of Sediment Sorting, Provenance, and Chemical Weathering From a Pliocene‐Pleistocene Sedimentary Core (CSDP‐1) in the South Yellow Sea

The South Yellow Sea is an important sink for sediments delivered by the Yellow and Yangtze rivers in East Asia. We conducted a high‐resolution geochemical analysis on the bulk sediments retrieved from a marine drill core (CSDP‐1) using the method of X‐ray fluorescence (XRF). Our results show large geochemical variations along the core. As demonstrated by linear correlations along with the Al‐Si link in a compositional principal component analysis (PCA), the variations in elemental ratios among Al, K, Zr, Ba, and Si are primarily controlled by sediment sorting effects. A closer examination indicates a gradual shift of sediment provenance from the Yangtze to the Yellow River catchment in the core. With the help of a fuzzy c‐means cluster analysis on elemental ratios of Al/Si, Al/Ti, K/Si as well as the chemical index of alteration (CIA), the timing of a major provenance change in the core is narrowed down to 1.5–1.7 Ma. This timing corresponds to a major seismic and sedimentary boundary (T2) in the Yellow Sea Basin and coincides with the onset of fluvial terrace deposition and incision in the middle and upper reaches of the Yellow River. As a result, we argue that the major provenance change derived from geochemical variations in the Yellow Sea sedimentary basin can be linked with the integration of the modern Yellow River. The provenance change is likely caused by a coupling between regional tectonic deformation and the Asian summer monsoon enhancement in the early Pleistocene. Plain Language Summary Located in the East Asia continental margin, the Yellow Sea is an important place where sediment carried by the Yellow River and the Yangtze River, two largest rivers in the world, is deposited. By studying a ∼300‐m‐long drill core (CSDP‐1) in the sea, we attempt to reveal the integration history of the modern Yellow River. What we found is during the Early Pleistocene, approximately from 1.5 to 1.7 Ma, there were significant changes in sediment’s chemical features. We interpreted that the changes may represent a sediment source transition from one dominated by the Yangtze River to one by the Yellow River. We conclude that the integration of the modern Yellow River is due to tectonic activity and climate change that happened in the upper and middle reaches during the Early Pleistocene. Key Points Geochemical variations of sediment records in the South Yellow Sea have been primarily influenced by sediment sorting effects The provenance analysis indicates that t