A New Method for Calculating Growth Rates of Ferromanganese Nodules From Marginal Seas: Implications for Terrigenous Input in the South China Sea

Accurate age determination of marine ferromanganese (Fe-Mn) nodules is crucial for interpreting their geochemical compositions as paleoceanographic tracers and for understanding critical metal (e.g., Co, Ni) enrichment. Previous empirical dating methods, primarily developed for deep-ocean nodules, are less effective in marginal seas with high terrigenous input. Here, we propose a novel rare earth elements and yttrium (REY) chronometer tailored for Fe-Mn nodules from the northeastern South China Sea (SCS). A robust negative correlation is established between the REY content and the growth rate: Growth Rate (mm/Ma) = −0.0186 × REY* + 38.301 (R² = 0.9223). Based on this model, we find that nodule growth in the SCS accelerated since ∼3.0 Ma, attributed to increased terrigenous input from the uplift of Taiwan. As more nodule data from marginal seas become available, this chronometer can be further refined, offering a reliable time marker for marine archives in these complex environments.