苏北中部滨海平原成陆机制研究

苏北中部滨海平原位于废黄河三角洲和长江三角洲之间，其形成与全新世最大海侵之后长江、古黄河的供沙历史和供沙状况密切相关，并且现今海域南黄海辐射沙洲的辐聚点也位于这段海岸，故探讨其成陆机制具有重要意义。本文数值模拟了公元８世纪时该区的Ｍ２潮汐、潮流，在此基础上，计算了７种粒径泥沙在当时潮流场中的净输运状况，划分了海底冲淤区。计算结果表明，公元８世纪时苏北岸外存在大致以东台为顶点的辐射状古潮流场，其分布格局与现今苏北岸外大致以京港为顶点的辐射关潮流场基本一致，该辐射状潮流场的存在是由当时台东岸外的独特驻潮波波腹所决定的。进入苏北岸外古辐射状潮流场中的泥沙，在辐聚、辐散的潮流作用下，每一个潮周期均自ＮＥ、ＳＥ方向向东台附近海域净输运泥沙，在东台附近海域发生淤积。由此认为，苏北中部滨海平原是大致以东台为顶点的辐聚、辐散潮

PRELIMINARY STUDY ON FORMATION MECHANISM OF THE MIDDLE LITTORAL PLAIN IN THE NORTHERN PART OF JIANGSU PROVINCE

The middle littoral plain in the Northern Jiangsu Province is located between the Old Yellow River Delta and the Changjiang River Delta. Its formation is related closely to the sediment supply history of the Changjiang River and the Old Yellow River after the transgression maximum of Holocene. At present, the convergent point of the Radial Sand Ridges in the Southern Yellow Sea is also located in this area. Therefore, study on the formation mechanism of the littoral plain has important significance. The M2 tide and tidal currents in the 8th century are simulated with a 2 D tide model. Based on tidal current results, sediment transport fields for seven kinds of grain size are calculated, and seabed erosion/accretion pattern is obtained from the divergence of sediment transport rate. The results show that a wave loop of standing tidal waves existed off the northern Jiangsu coast in the 8th century. Under the control of the wave loop, tidal currents converge to or diverge from the Dongtai area. The distribution pattern of the paleo radial tidal current field is similar to that of the present one with apex in the Qianggang area. Within a single tide cycle, net sediment was directed towards the Dongtai area, thus net deposit occurred in this area. The simulated results of the paleo radial tidal current field and the sediment transport patterns in this paper are generally consistent with field data. The littoral plain was formed from submarine shoal, which grown up quickly and combined with land when the radial tidal current field transports sediment from the Old Yellow River and the Changjiang River towards the Dongtai area with net accretion. The paleo radial tidal current field with apex in Dongtai area and abundant sediment supply from the Old Yellow River and the Changjiang River are two favorable conditions for development of the littoral plain.