Evolution of a deep-water ferromanganese nodule in the South China Sea in response to Pacific deep-water circulation and continental weathering during the Plio-Pleistocene

Abstract

The South China Sea (SCS) is connected to the West Pacific through a deep channel in the Luzon Strait. Thus the SCS deep water is sensitive to the evolution of Pacific Ocean circulation, which significantly influences the global climate system. Geochemical data (Pb isotope and redox-sensitive elements data) and magnetic data were determined for a Fe–Mn nodule obtained from Jiaolong seamount in the central SCS. These records reflect interactions between changes in ice sheets, deep Pacific circulation, and weathering inputs to the deep SCS during the Pliocene and Quaternary. Our results show that the SCS deep-water environment can be divided into three major Stages (Stages 1–3). Stage 1 (∼4.8–1.4 Ma) was characterized by a well-oxygenated Pacific Deep Water (PDW) and lower dust inputs; then moderate stable deep-water ventilation and greater inputs of Asian dust occurred during Stage 2 (1.4–0.9 Ma). During Stage 3 (<0.9 Ma), a more isolated PDW was accompanied by sluggish Pacific overturning circulation, probably due to the weakened southern-sourced deep-water formation. In general, the progressive intensification of northern hemisphere ice-sheet play an active role in controlling the variation of the deep-water environment in the SCS. Interestingly, the variation in deep-water ventilation lagged behind weathering and erosion around the Middle Pleistocene Transition, which strongly indicates that the ocean and continent environments had different sensitivities to the global paleoclimatic changes at the glacial climate boundary.