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A STUDY ON THE SOURCE AND THE DISTRIBUTION OF CLAY AT THE YELLOW SEA

Lin Chengkun(Department of Geo and Ocean Sciences, Nanjing University)  
Clay at the Yellow Sea (the HuangHai Sea) is composed largely of clay with d0.005mm, mineralogically. The most important constituents are clay minerals such as illite , montmonllonite, kalinte, chlorite etc. . According to characteristics of natural zone and their effect on composition of clay minerals, the source of cohesive sediment at the Yellow Sea can be considered as coming from 2 supplying regions, namely, the Yangtze River(X1), the Yellow River and the abandoned Yellow River delta (x2). The converging points are set up in the Yellow Sea area. Sampling stations are set up in the supplying regions and the converging points. Evaluation was made of clay minerals obtained out of sample from each sample by X-ray diffraction method, to ascertain their types, calculate their percentage, and work out the average percentage of clay mineral to represent the clay mineral composition of cohesive sediment at the Yellow Sea and its supplying regions. Clay mineral percentage thus worked out through evaluation of sediment samples from sample sites at the Yellow Sea and its supplying regions are listed in Table 1.Investigations and studies on the physiography indicate that clay mineralogical characters of cohesive sediment of the Yellow Sea are governed by geographical and geomorphological conditions of the watershed. According to the principle of equilbrium of sediment load, equations of clay mineralogical classification are presented. By means of least Squares Method, a mormal equation for calculating the converging percentage from all the supplying regions is given below: are the coefficients relatedto clay minerals.When the converging percentage of cohesive sediment from the Yangtze River supplying region (x1) or from the Yellow River supplying region (x2) is known, the source of clay deposition at each point of the Yellow Ses is computed. According to the data of all point of the converging percentages of 50% from the Yangtze River supplying region (X1), the map of source and distribution of clay deposition at the Yellow Sea is drawn in Fig.i.Fig. shows that in the deposited area of clay at the Yellow Sea, cohesive sediment comes mainly from the Yangtze River supplying region(X1) , which is called deposited area of the Yangtze River, covering an area of 226000 sq.km comprising 56.5% of the total Yellow Sea. When cohesive sediment comes mainly from the Yellow River supplying region (x2), it is called the deposited area of the Yellow River, covering an area of 174000 sq. km comprising 43. 5% of the whole.In the deposited area of the Yellow River under the influence of current system of Bohai Sea and western coast current of the Yellow Sea, a greater part of cohesive sediment is transported to the south, it deposites at west of 123 °E and a little part deposites at north coast of the Yellow Sea from 37°30'N to 40°N. In the deposited area of Yangtze River when the Yangtze River discharged into China Sea, a part of cohesive sediment is transported southeastward, and the others turn out of east 123 °E and join the Yellow Sea and Tsushima Warm Current. Cohesive sediment can extend to north of the Yellow and Bohai Sea and deposite at this area.This is quite different from what has been found in foreign countries
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