| Yellow Sea and Bohai Sea are important parts of the eastern shelf of China, Bohaisea is located in northeastern part of China’s continental shelf, is a nearly enclosed seawhose topography is flat; while the Yellow Sea, located in the western Pacific Ocean,is a semi-enclosed shallow sea and between the mainland China and the KoreanPeninsula. Marine sediments contain a variety of geological history, not only canreveal geological changes in the modern seabed but also can detect the distribution ofseabed resources, such as biological resources, mineral resources, energy and so on,the research is not only theoretically but also economically important. Since the studyarea is of multi-provenance and complex hydrodynamic environment, there is muchcontroversy about the provenance identification and transport routes, so the study ofthe magnetic characteristics of the Yellow sea and Bohai sea surface sediments is veryimportant for the further research of surface sediments provenance and its transportroutes.This paper is based on analysis of particle size parameters and magnetic parametersof167surface sediments from Yellow sea and Bohai sea, summarizes the distributionof particle size parameters, magnetic parameters, discussed the types of magneticminerals and magnetic domain information, classified in accordance with thecharacteristics of the magnetic parameters and summarizes the features and analyzeits causes, discussed the relationship between the different size sediments andmagnetic parameters, eliminating the influence of particle size on the magneticparameters, discussed the relationship between magnetic characteristics andhydrodynamic characteristics, different magnetic characteristics of the differencesmuddy sediments areas and the relationship between the magnetic characteristics andprovenance. Obtained the main knowledge as follows: 1. The particle size distribution characteristics of Yellow sea and Bohai seasurface sediments. In eastern and central Southern Yellow Sea, western and centralNorth Yellow Sea, northwest Bohai Sea and northern Liaodong Bay, sedimentparticles are finer and poorly sorted with higher sorting coefficient. It is explained thatthese areas have weak hydrodynamic environment, the ability of sorting sediments inpoor; while in southern Liaodong Bay, Bohai Strait, eastern North Yellow Sea,western and southern South Yellow Sea and the Yangtze River estuary, sedimentparticles are coarser and better sorted with low sorting coefficient. It is explained thatthese areas has stronger hydrodynamic environment and the ability of sortingsediments is strong;2. The distribution of magnetic parameters of Yellow Sea and Bohai sea surfacesediments. Magnetic characteristics of the study area surface sediments are dominatedby ferrimagnetic mineral, wherein the magnetic mineral particles of Bohai Sea andNorth Yellow Sea surface sediment is coarse and dominated by single-domain andmulti-domain magnetic mineral,while in South Yellow Sea surface sedimentsmagnetic mineral grains are smaller and dominated by single-domain andpseudo-single-domain. Most of the Yellow Sea and Bohai sea surface sedimentscontain a certain amount of superparamagnetic (SP) particles. From the southeast tothe northwest the magnetic mineral content increases in Bohai Sea surface sediments,while with increasing distance from the coast magnetic mineral content becomes lessfor North Yellow Sea surface sediments. In the northern South Yellow Sea it’smagnetic minerals distribution is similar to the North Yellow Sea, and in the centralSouthern Yellow Sea, there is a low susceptibility areas, from central South YellowSea to the southeast and southwest, magnetic mineral content gradually increases.Overall, most of the Southern Yellow Sea surface sediments contain less magneticminerals than the Northern Yellow Sea sediments, while the Northern Yellow Seasurface sediment is less than most areas of the Bohai Sea. By analyzing the SIRM andgrain size parameters, magnetic mineral content positively correlate with an averageparticle size, by clay and silt content, but has significant negative correlation withsand content; 3. Correlation between different size fractions of the sediment and magneticparameters. Analysis and comparison of magnetic parameters correlated with the sizeparameters,(different size fractions of the sediment mass×magnetic parameters)and (full sample mass×magnetic parameter) and the average percentage of magneticparameters correlated each grain, the study found that the sample’s magneticcharacteristics mainly determined by clay sediment grain size (<4μm), and theproportion of substantially more than50%. Coarser sediments (>32μm) has a greaterimpact on the overall magnetic characteristics (about20%-30%), other size fractionsof the sediment little contribution to magnetic characteristics of the sediments, and themagnetic characteristics between particle size of <32μm sediment and particle size>32μm sediment have a great difference; By comparing the magnetic characteristics ofdifferent types of different size fractions, found that sediment particle size <32μm it’smagnetic mineral content and ferrimagnetic magnetic mineral content was higher thansediment particle size>32μm, mainly due to the magnetic minerals are heavyminerals and mineral grain size is smaller easily enriched in fine-grained sediments,magnetic minerals in the sediments of <32μm in fine greater than the sedimentsof>32μm;4. Yellow Sea and Bohai sea surface sediments magnetic feature classification,characteristics, provenance and genetic analysis. According to the sample S-300,magnetic parameters SIRM/χ and SIRM, the Yellow Sea and Bohai sea surfacesediments are divided into four types, Type1is named Yangtze river provenance andhigh content of magnetic minerals zone, which is characterized by a high magneticmineral content, moderate magnetic mineral particles and moderate ferrous magneticmineral content, by the Shandong Peninsula coast currents, SuBei coastal currents andstrong tide, transport sediment from Yangtze River and Old Yangtze River; type2isnamed Yellow mud area fine magnetic minerals zone, which is characterized bymoderate magnetic mineral content, moderate ferrous magnetic minerals content, finegrain size of magnetic minerals, this type farther away from provenance, it’ssediments contain Yangtze River and Yellow River substance, and also containsubstance transported by Kuroshio, HWC and other circulation; type3is named low content of magnetic minerals in sedimentary transition zone, the magneticcharacteristics of the magnetic mineral content is relatively low, ferrous magneticminerals content is low and magnetic mineral grain size moderate, the type of materialsource is abundant, but the Yellow River sediments predominate; type4is named forthe strong hydrodynamic coarse magnetic mineral zone, which is characterized by ahigh magnetic mineral content, coarse grain size of magnetic minerals, low ferrousmagnetic minerals content, the type of strong hydrodynamic, in the southern of theSouth Yellow Sea the Yangtze River sediments and sediments brought by Kuroshiomake a big difference;5. Magnetic characteristics of the study area and hydrodynamic parameters of theenvironment. Three muddy area were analyzed for this purpose. Bohai muddysediment has coarser magnetic minerals than the North Yellow Sea and SouthYellow Sea mud area, and the magnetic mineral content is also higher than the othertwo mud areas, but the ferrous magnetic minerals content is similar; along theShandong Peninsula coast current, magnetic mineral content becomes lower, grainsize becomes smaller and the ferrous magnetic mineral content varies little; whilealong the SuBei coastal currents, magnetic mineral content gradually become increase,ferrous magnetic mineral content also increases, the magnetic mineral grain sizegradually coarsens, probably due to the Kuroshio brings coarse particles of strongmagnetic minerals; along the HWC direction, its mud area magnetic characteristicschange significantly, in the South Yellow Sea mud area, sediment magnetic mineralcontent and ferrous magnetic minerals components are basically stable, while themagnetic mineral particles and the median diameter after a sudden fining continuedfrom south to north, inferred deposition may be mainly from the south into the muddyarea, and in the Northern Yellow Sea mud area, magnetic mineral content and ferrousmagnetic minerals content significantly increase, and from east to west decreases afterthe growth, and magnetic mineral grain size becomes fine, but first coarse then fine,indicating that the deposition process and the type of source material is morecomplex. |
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