Iron geochemistry and C-S-Fe early diagenesis in sediments on South China Sea northeastern slope derived from tectonically active islands Responses to climate and environment changes

The dataset contains an age-depth model, sediment grain-size fractions, mean grain size, organic carbon contents and isotopic compositions, main elemental compositions, solid-phase reactive iron and reduced sulfur chemistry, and porewater chemistry collected from the northeastern slope of the South China Sea (SCS). These data were used to elucidate how sea-level rise and ocean current driven changes in sediment provenance from tectonically active Taiwan and Luzon islands have influenced Fe geochemistry and carbon–sulfur–iron diagenesis since the late Last Deglaciation. Results indicate that during 12.4–10.0 ka BP, marine organic carbon (OC) declined as primary productivity fell in response to rapid sea-level rise and weakening of East Asian Winter Monsoon (EAWM). During the low sea-level period before ~10 ka BP, elevated availability of degradable OC fueled sulfate reduction; however, total reduced inorganic sulfide (TRIS) remained low due to generally refractory nature of the sedimentary OC. After ~9 ka BP, bulk OC remained low, reflecting a weaker EAWM and enhanced Kuroshio intrusion driven by increased El Niño–Southern Oscillation (ENSO), with an increase in Luzon-derived sediment input in response to the intensification of Kuroshio intrusion. During the sea-level highstand after 9 ka BP, low OC and abundant reactive Fe oxides promoted dissimilatory Fe reduction, thereby suppressing sulfate reduction. After ~8.6 ka BP, enhanced input of Fe-rich volcanic material from Luzon by intensified Kuroshio intrusion represented a key mechanism for FeHR enrichment in marginal seas even under low-to-moderate chemical weathering of the source materials. Markedly high ratios of poorly reactive Fe (FePR) to FeT reflect the contribution from Luzon-derived Fe-rich detritus and/or inheritance from source materials typical of tectonically active islands in general. This study reveals coupled responses of sediment provenance, OC burial, and C–S–Fe diagenesis to sea-level and climate change, highlighting Fe-rich volcanic material in shaping Fe geochemistry and reactive Fe enrichment in oxic marginal seas.