| 摘要: |
| 自1932年Shepard根据当时的海图指出亚洲东岸海底沉积物普遍存在近岸细、远海粗的分布特点以来,不少学者如 Shepard,Niino和Emery,范时清、秦蕴珊等对东海大陆架沉积物的类型及分布特征都进行过较详细的研究。他们认为外陆架砂质沉积物是在晚更新世冰期低海面时形成的。七十年代以来又有很多部门进行了大量广泛深入的调查研究。
本文根据我们近年来对陆架浅钻岩芯的分析和研究,就东海大陆架及黄海南部现代沉积物的形成过程提出一些粗浅的看法。
现代沉积物一般是指在现代环境下沉积的沉积物。正如 Mcmanus(1975)指出的,在时间上,其沉积物质的供给、分布及其沉积过程都是在现代进行的。由于现代环境具有一定的延续时间,所以现代沉积物还包括自该环境形成直至现在这个时期内形成的沉积物。
冰后期东海大陆架发生海侵,距今7500年前海平面接近于现今海平面,自那时以来,海平面保持相对稳定,除河口及近岸地区外沉积环境基本上没有发生大的变化,现代沉积开始形成的年代大体上与这个时期一致。现代沉积物分布于长江口三角洲及闽、浙近岸水深小于60-70米,宽约90-100公里的浅海地带,苏北沿岸向东至济岛地区,可延至水深100米左右(图1)。
东海大陆架现代沉积物的分散与沉积过程,直接受陆架区现代海洋水文要素的控制,东海陆架区的海流系统及盐度分布见图2,3。长江每年注入东海的总水量达9540亿立方米,占注入东海总水量的92%,其径流量的变化和淡水舌的分布以及流经本区东部的黑潮直接控制了本区的水文特征。 |
| 关键词: 东海大陆架 现代沉积 |
| DOI： |
| 分类号: |
| 基金项目:中国科学院海洋研究所调查研究报告第676号 |
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| A GENERAL DESCRIPTION OF THE MODERN DEPOSITION ON THE CONTINENTAL SHELF OF THE EAST CHINA SEA |
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Yang Guangfu, Dong Tailu, Xu Shanmin
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Institute of Oceanology, Academia Sinica
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| Abstract: |
| This paper presents a general description of modern deposition on the continental shelf of the East China Sea. The material upon which this study was based consisted of core and surface sediment samples。
On the continental shelf. the modern sediments consist mainly of clay, while in the region of estuaries and the Jianggang Bay in northern Jiangsu Province, they consist mainly of sand. In the region south of the Changjiang (Yangtze) River mouth, at water depths of less than 50-60 meters, the area of clayey sediments ranges from 90-100 kilometers in width, being thickest near the shore, measuring about 40-50 meters and thinning out toward the sea.It is also vastly distributed in the southern part of the South Yellow Sea where it extends over an area with water depths of 100 meter. its thickness being less than half a meter.
The modern sediments on the continental shelf occurred 7000-8000 yrs B.P.when the sea level uplifted to the present position. Transportation and deposition of the modern sediments are influenced by both the movement of terrigenous source materials and current, so the distributive tendency of the modern sediments is consistent with both the consistent variation of suspended materials in. sea water and the current system. The suspened materials that come from the Changjiang (Yangtze) River mouth have been distributed by currents. Some of them are carried southward by longshore current of the East China Sea, and then deposited in the shallow area near the shore south of the Changjiang(Yangtze) River mouth, while the other suspended materials are transported eastwards, and deposited in the southern part of the South Yellow Sea. The suspended materils carried away from the northern and
middle part of the South Yellow Sea by southflowing current are also deposited in the southern part of the South Yellow Sea, the residual suspended materials are transported over the continental shelf into the open sea. The sandy materials from the Changjiang (Yangtze)River are deposited in its estuary. The presence of sandy sediments in Jianggang Bay is a result of the action of tidal current. In the area of relict sand only a little biogenic deposition occurred.
The continental shelf of the East China Sea may be divided into four modern depositional provinces and one relict depositional province: 1) modern deltaic deposition in the Changjiang(Yangtze)River mouth; 2) shallow sea deposition covering near shore areas from Fujian Province to Zhejiang Province; 3)shallow sea deposition in the northern part of the continental shelf;4) modern tidal current deposition in the Jianggan Bay; 5) relict deposition on the outer continental shelf. |
| Key words: MODERN DEPOSITION THE CONTINENTAL SHELF OF THE EAST CHINA SEA |
