Rock magnetic properties of the fine-grained sediment on the outer shelf of the East China Sea: implication for provenance

The rock magnetic properties of surface sediments from the fine-grained depositional area on the outer shelf of the East China Sea, an area surrounded by sands, were investigated with a view to providing information on the sediment provenance. Multiple magnetic parameters such as magnetic susceptibility, anhysteretic remanent magnetization, saturation remanent magnetization (SIRM), coercivities of SIRM, and S ratios (relative abundance of low-coercivity magnetic minerals) were measured for all 179 surface samples, and partial representative samples were examined for their magnetic hysteresis parameters, temperature dependence of magnetic susceptibility and X-ray diffraction spectra. Our research indicates that the magnetic mineralogy is dominated by magnetite with a small amount of hematite and is primarily of a pseudo-single-domain to multidomain nature with a detrital origin. The magnetic concentration in the study area generally decreases to the east or southeast accompanied by magnetic particle fining to the east or northeast. The geographic pattern of magnetic properties is most reasonably explained by a major source of sediment jointly from the erosion of the old Huanghe River deposit and the discharge of the Changjiang River. The rock magnetic data facilitate understanding of the transport mechanism of fine-grained sediments in the outer shelf of the East China Sea.