Burial depth and calcium carbonate content of sediment: impact on the sediment dry bulk density for the South China Sea

The dry bulk density （DBD） of marine sediment is an important parameter to calculate the mass accumulation rate and estimate the sediment flux in geological history. Due to sparse sampling interval, data of DBD in many borehole sediments are often poor in resolution or even unavailable, which restricts subsequent studies. Previous studies have found that the DBD of deep-sea sediments can be estimated via the content of CaCO₃ in the sediments. However, whether this method is feasible for the South China Sea (SCS) sediments remains unknown. In this study, we collected and analyzed data of DBD, CaCO₃ content (CaCO₃%), and burial depth of downcore sediment samples from 17 sites in four ODP/IODP expeditions of Legs 184, 349, 367, and 368 in the SCS. Results showed that the burial depth is an important factor affecting DBD in the southern SCS where currents are less dynamic as represented by the ODP1143 site, showing significant DBD-CaCO₃% relationship; while in the northern and central SCS, relationship between DBD and CaCO3% is poor due probably to dynamic currents and multiple non-CaCO₃ inputs, which leads to the unstable sedimentary environments. Using the burial depth and CaCO₃% of the ODP1143 site as variables, an empirical binary polynomial fitting equation for DBD was established, which may be applicable for the DBD estimation for the southern SCS where the sedimentary environment is similar to that of the ODP 1143 site.