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The sources, transport pathways and main distribution limitations of surface sediments were clearly identified in the Bohai Sea (BS) and Yellow Sea (YS) by combining the particle size and magnetic property distribution characteristics. The sediment distribution pattern on shelves is mainly controlled by the sediment sources, which include Huanghe-derived sediments, coastally eroded sediments, old Huanghe and old Changjiang subaqueous delta sediments, and mixed sediments transported by the Yellow Sea Warm Current (YSWC). The distribution pattern of silt reflects the transport pathway and limitation of the Huanghe- and old Huanghe-derived sediments, and the sand distribution reflects the final distribution of the coastally eroded sediments, including the eroded old Changjiang subaqueous delta sediments. In addition to the sediment sources, the complex hydrodynamic pattern on the shelves has an important influence on sediment distribution and transport. The sediment particle size and topography of shelves exert limited control over the sediment distribution. Surface sediment sources in the central South YS (SYS) were identified, with the most important contribution being from mixed sediment sources and a convergence area of finer sediment located at approximately 123°E, 36°N. [ABSTRACT FROM AUTHOR]

Abstract: Sedimentary environment and formation mechanism of the mud deposit in the central South Yellow Sea of China during the last 40kyr are studied based on the analysis of particle size, sediment density, chemical features, magnetic properties and AMS 14C ages of a new core YS01A together with other available core data. The results show that there exist four sedimentary sections during this 40kyr period, including two marine sections (A and C) and two terrestrial/intertidal sections (B and D). Sedimentary indexes of section D, which were formed before 40kyr, show that strong weathering and erosion occurred in this section. In contrast, sedimentary environment of section B was wetter and warmer and weathering and erosion were not as strong as in section D. Marine deposits in both sections A and C indicated the effects of sea level rise and section C was deposited when the climate was much wetter than in section A. Variations of climate and local hydrodynamics created different sediment features of two marine sections. From the estimated river discharges of the Huanghe, Changjiang and relevant Korean rivers and calculation of mud deposit volumes of section A during the past 9.7kyr, it is found that the sediment inputs from these river sources can only account for about 48% of sediments in the two mud deposits of the central and southeastern South Yellow Sea. The other main source of sediments is identified to be the seabed erosion, resuspension and redeposition from the Yellow Sea and, to a lesser extent, from the biogenesis and diagenesis. It provides a unique opportunity of understanding the formation and source of mud deposits by comparing the sedimentary properties of sections A and C in core YS01A. It is found that formation of mud deposits is not related directly to the Yellow Sea Warm Current, which only changed the sediment properties of mud deposits in section A since it formed from Holocene by bringing a large amount of organic mass and finer particles. However, cold water mass developed in this area is important as it helped to trap more and finer particles in the two marine sections. Upwelling usually occurs around 50m bathymetry which is at the juncture of two opposite water currents and has induced the thickest sediment layer. This study also confirmed that formation of the mud deposit in the central South Yellow Sea is caused mainly by the tidal currents on the continental shelves. [Copyright &y& Elsevier]

Abstract: Mud deposits are widespread in estuaries and on continental shelves, and contain important information regarding interactions between terrestrial and coastal processes. Magnetic properties of muddy sediments from the northeastern continental shelves of China, including shelves close to Korean coasts, were analyzed using bulk and size-fractionated samples to elucidate muddy sediment sources and transport. Types, concentration, and granulometry of magnetic minerals were determined and all samples were found to be dominated by magnetite. Muddy sediments from the Zhemin coast (off the Zhejiang and Fujian coasts) have the highest magnetic susceptibility (χ) and saturation isothermal remanent magnetization (SIRM) values, while those from the central and southeastern South Yellow Sea and the western Korea Strait have lower values reflecting lower magnetic mineral concentrations. Single domain ferrimagnetic grains dominate the magnetic particles in the central South Yellow Sea, while superparamagnetic (SP) grains contribute significantly to the magnetic grains in the Bohai Sea. SP and coarse multi-domain (MD) grains dominate magnetic grain assemblages in the North Yellow Sea and along the Zhemin Coast. Rock sediment particle size is not a major factor affecting the magnetic properties of the mud deposits in the study area. Rather, terrigenous inputs and hydrodynamic transport processes primarily control the magnetic properties, and sediments from the Changjiang and Huanghe rivers make the most significant contribution. This observation applies to the whole study area, although terrigeneous magnetic mineral concentrations decrease with increasing distance from the river mouths due to both sorting and mixing with other sediments with weak magnetic signatures. Bacterial magnetosomes also play a role in the central South Yellow Sea. [Copyright &y& Elsevier]