辐射沙脊群典型潮道-沙脊过渡带短尺度沉积与地貌变化过程

The large-scale and typical radial sand ridges in the near shore region of middle eastern Jiangsu Province was developed in the background of sea level rising in the post-glacial period. The ridial sand ridges covered more than 20000 square koilometers and displayed as a huge sedimentary morphological system composed of tens tide channels and sand ridges.Since the 1980's, great advances have been made in the study of sedimental and morphological changes.one field of the advances is the better understanding of the formation and evolution modles of the ridial sand ridges in large temporial-spacial scale based on the analysis of field survey, surface-core sediments results,tide current data. The another aspect of advances is the study of sand banks,sand ridges and tide channels changes in ten years- few years scale based on the comparison of different temporial remote images and field survey.It is obvious that the sedimentary and morphological changes or process of the transition zone between the channel and ridge are the key process of modern ridial sand ridhe and the related study is few in the past decades.This application is planned to sellect the transition zone between Xiyang Chnnel and Dongsha sand ridge as the study area. Choosing 3 sections and 8 times of field surveys will be carried out in the spring season and autumn season, the additional surveys will be completed in the summer after the storm surge.The key object of this study is the short scale sedimentary and morphological changes and its evolutions trend in the transition zone between the tide channel and sand ridge of the study area. The research results will be of important geomorphological significances and will provide the useful scientific data for the construction of the planed huge man-made island of Dongsha in the sand ridge.

江苏沿海近岸海域在冰后期海平面上升过程中发育了的典型辐射状沙脊群，涉及海域面积20000多平方公里，由数十条潮道和沙脊构成的沉积地貌体系。二十世纪80年代以来，辐射沙脊群地区的地貌与沉积研究取得了很大的进展：据野外调查、沉积钻孔、潮流资料，对辐射沙脊群大时空尺度地貌的形成过程和演化模式有了科学认识；据不同时期遥感影像和实地观测，对辐射沙脊群地区沙洲、沙脊、潮沟地形在十年、多年尺度上的动态变化趋势做了大量的研究。由于潮道-沙脊过渡带的沉积与地貌动态变化是辐射沙脊群演化的关键动力过程，这方面的研究十分薄弱，申请项目选择西洋-东沙潮道地形过渡带的3个断面，不同季节和夏季风暴潮之后进行多次重复断面地形、表层-柱样沉积采集，并用浅地层剖面勘测断面沉积地层，探索短时间尺度潮道-沙脊过渡带沉积与地貌动态和冲淤变化趋势，具有重要的学术价值，可为潮道-沙脊过渡带动力地貌理论研究和应用提供科学基础数据。

江苏近岸海域在冰后期海平面上升过程中发育了的典型辐射状沙脊群，涉及海域面积20000多平方公里，由数十条潮道和沙脊构成的沉积地貌体系，由于潮道-沙脊过渡带的沉积与地貌动态变化是辐射沙脊群演化的关键动力地貌过程，申请项目选择西洋-东沙潮道地形过渡带进行现场水沙过程观测，采集了东沙浅滩多个浅钻岩芯，进行了210Pb测年分析，分析了东沙沙脊浅滩不同位置的沉积速率，对1973-2016年相近的低潮位时相的东沙浅滩遥感影像进行了沙脊水边线和沙脊线的提取，探索短时间尺度潮道-沙脊过渡带沉积与地貌动态和冲淤变化趋势。. 研究发现：东沙浅滩岩芯记录沉积速率变化显著，其中东沙的南端为淤积的峰值区，与潮流辐聚泥沙汇聚沉积过程有关；东沙西部边缘处于持续性的冲刷环境；沙脊中心部位沉积速率较低，东北部因为大量的养殖紫菜筏架影响，沉积速率有增加的趋势；对近岸海域一系列沙坝遥感影像的提取分析，发现沙坝的发育走向基本与海岸线方向平行，且前端都发育有沙嘴，并不断向东南方向延伸，表明江苏沿海潮滩的物源地主要是辐射沙洲及废黄河水下三角洲。遥感分析发现1973-2016年期间的东沙浅滩发生了很大的变化，整体向东北移动，东沙浅滩南北向的分水岭（脊线）总体向东迁移，西洋-东沙过渡带的冲刷明显。. 本项目的研究对认识辐射沙洲的现代动态变化过程具有较大的学术价值，可为潮道-沙脊过渡带动力地貌研究和应用提供科学基础数据