古长江河口湾充填潮流作用机制的初步探讨

Preliminary study on the role of tidal currents in the filling of the paleo-Changjiang River Estuary

长江三角洲的发育是以古长江河日湾的充填来实现的．研究潮汐、潮流在古长江河口湾充填中所起的作用，可深入了解长江三角洲的形成发育过程．建立了渤海、黄海、东海的二维潮流数学模型，数值模拟了冰后期最大海侵，即现今长江三角洲地区为巨大河口湾时的M2潮汐、潮流．在此基础上，计算了古长江河口湾及其周围海域8种粒径泥沙的潮平均悬移与推移输沙率，并根据输沙率散度的正负，划分了海底冲刷区与淤积区．根据计算结果得出，冰后期最大海侵时，存在大致以古长江河口湾湾口中点为腹点、波腹线向海凸起的独特驻潮波波腹区．在其控制下，外海潮流大致以古长江河口湾湾口中点为顶点作辐聚、辐散运动．在古潮流场作用下，经历每一个潮周期后，古长江河口湾周围海域的泥沙均向河口湾内净输运，并在河口湾内淤积．古长江河口湾的充填是在长江带来大量泥沙，外海的潮汐、潮流又有利于泥沙向河口湾内净输运，且在河口湾内沉积的情况下实现的．外海的潮汐、潮流为古长江河口湾的充填、长江三角洲的发育提供了必要而又有利的水动力环境．

The Changjiang River Delta was formed through the filling of the paleo-Changjiang River Estuary (PCRE). Thestudy on the role of tide and tidal currents in the filling of the PCRE can help to understand the development of the Changjiang RiverDelta better. With a 2-D tide model, the M2 tide and tidal currents in the Bobal Sea, Huanghai Sea and East China Sea at the postglacial marine transgression maximum are simulated. Based on the hydrodynamic data obtained, the sediment transport fields of 8kinds of grain size in the PCRE and its adjoining areas are calculated, and the scabed erosion-accretion pattern is obtained in termsof the divergence of sediment transport rate. The results show that at the post-glacial transgression maximum, there existed a noticeable wave loop of standing tidal waves with the antinode of the wave loop being located in the mouth of the PCRE, and the waveloop lines being protruded towards sea. Under its control, tidal currents converge to or diverge from the mouth of the PCRE. Within a single tidal cycle, net sediment was directed towards the PCRE. Thus the PCRE has been filled under the conditions that theChangjiang River supplies a large amount of sediment, and the tide and tidal currents in the open sea impel this sediment to depositas much as possible in the PCRE. The tide and tidal currents in the open sea provide necessary and favorable dynamic environmentfor the filling of the PCRE and the development of the Changjiang River Delta.