Grain size, TOC and elemental composition data for sediments from the northern South China Sea

All 22 samples were located on the northern slope of the South China Sea, of which 17 samples were collected using a box sampler during cruise HYSH201901 of R/V Haiyang IV in 2019 and 5 samples were collected using a piston corer during Ocean Drilling Program (ODP) Expedition 184 in 1999. All samples were stored in cold repository and dried before experimental treatments. Grain size measurements of the sediments were carried out on a Mastersizer 3000 laser particle size analyzer. Prior to analysis organic matter was removed by leaching the sediment with 15% H2O2. Total organic carbon (TOC) of the sediments was measured in Thermo EA-IsoLink elemental analyzer. Prior to analysis carbon bound to carbonate minerals was removed by leaching the sediment with 10% HCl. Total element concentrations (Al, Ca, Ti, Fe, Mn) of the bulk sediments were measured after acid digestion (HF, HNO3 and HCl) by Thermo iCAP 7400 ICP-OES. Solid phase iron speciation data were measured following sequential Fe extraction (Fecarb, Feox, Femag, Fepy) by Thermo iCAP 7400 ICP-OES.