Provenance Shift Recorded in Core Sediments From Northwest Hainan Island During the Middle Pleistocene: Evidence From Clay Minerals and Trace Element Geochemistry

ABSTRACT Since the Neogene, sediment transport to the northwestern South China Sea has involved multiple source areas, but provenance histories remain ambiguous due to overprinting by environmental change and tectonic activity. Xinying Bay, located off northwestern Hainan Island, transitioned from an open shelf to an inner bay during the Pleistocene and now serves as a key archive for disentangling climatic and tectonic influences on regional source–sink dynamics. This study integrates 14 C and electron spin resonance (ESR) dating, clay mineralogy and trace and rare earth element geochemistry of sediments from Core ZKDZ01 in Xinying Bay. Results reveal three distinct provenance units. The lowermost unit (U1) contains old sedimentary components with clay mineral assemblages and trace element ratios resembling those of Red River sediments. The middle unit (U2) shows affinity to intermediate–acidic granites from Hainan Island. The upper unit (U3) reflects mixed inputs from both Hainan and the Red River. We suggest that the shift from U1 to U2, dated to ca. 639–565 ka, was driven by the termination of the middle Pleistocene transition (MPT), when post‐glacial warming and sea‐level rise intensified local weathering on Hainan while inhibiting Red River sediment supply. The subsequent shift from U2 to U3 is attributed to regional tectonic uplift associated with volcanic activity and the opening of the Qiongzhou Strait. These findings highlight the coupled influence of climate and tectonics on sediment dispersal in the northwestern South China Sea since the Pleistocene.