中国的潮滩

本文将中国潮滩分为平原型和港湾型二类。以渤海湾和江苏海岸为例,讨论了平原潮滩的环境条件、沉积动力过程及沉积相,就浙江、福建具代表性的三个港湾,叙述了港湾潮滩的特征,还讨论了沉积物供应量及潮汐作用对潮滩发育的影响。

TIDAL FLATS OF CHINA

4 000 km long tidal flat coast of China can be divided into two major types: plain type and embayment type. Tidal processes and the quantity of sediment supply are the main factors in controlling the tidal flat development.The annual sediment discharge of Yellow River is 11×10⁸t. Because the Yellow River has migrated its course in great distances on both sides of the Shandong Peninsula, thus, wide tidal flats have been developed on the plaincoasts of Bohai Bay and the west Yellow Sea of Jiangsu Province. The two places are the major tidal flat coast of China. This kind of tidal flat is with the natural characteristics of: 3 to 20 km of width, a slope of 0.2—1%. Three zonations of mud flats above high tidal level, a sandy silt flat near the low tidal level and a mudy silt flat in the middle part of the intertidal zone. There are two major layers appeared in the profile: 2—3 m thick of mudy deposits on the upper layer, 10—15 m thick of sandy deposits of the lower layer, and a small transitional layer of mixed deposits in the middle. It is a kind of continuous deposits by huge sediment supply of large rivers. The sediment body can occupy an area of several square kilometres and a thickness of 100 metres with several cycles.There is a different type of embayment coast along Zhejiang, Fujian and Guangdong Provinces which is controlled by the different tectonic fault zone or fault basins. The suspended particle materials of the Yangtze River are transported longshore to the south during winter season, and the drifting joined with other rivers' inputs along Zhejiang and Fujian coasts together. This has a great influence on the tidal flat development in the long, narrow bays of the area. This type of tidal flats mainly consists of fine sediment of mud, without clear layers on the section profile or zonations on the plain view. The flats here are changeable locally and with rather small sediment bodies.