| 冰期时的中国海——研究现状与问题 |
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| 引用本文： | 汪品先.冰期时的中国海——研究现状与问题[J].第四纪研究,1990,10(2):111-124. |
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| 作者姓名： | 汪品先 |
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| 作者单位： | 同济大学海洋地质系 |
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| 摘 要： | 沉积柱状样分析表明:末次冰期最盛时,东海缩剩冲绳海槽,南海变为袋状海湾,大河在陆坡入海,使南海北部陆坡与冲绳海槽海水浊度大增,沉积中碳酸盐含量被陆源物稀释,使剖面中CaCo3旋回与大西洋相似、与太平洋相反。因极锋南移,亲潮可能影响冲绳海槽,太平洋温水可能进入巴士海峡,南海表层冬、夏双向海流变为环流,加上沿岸冲淡水影响,使南海北部陆坡冬季表层水温比间冰期低6—9℃,季节差达8—10℃,远超过太平洋同纬度区的数值。
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| 关 键 词： | 冰期 中国海 碳酸盐沉积 古水温 古海流 |
THE ICE-AGE CHINA SEA——STATUS AND PROBLEMS |
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| Institution: | Department of Marine Geology, Tongji University |
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| Abstract: | Cores taken from over a hundred sites of the China Sea have been analyzed mainly in China since the last years. In the cores, deposits of the Last Glacial Maximum from 20 000 to 15 000 a B. P. have been recognized on the basis of 14C datings, microfossils and their oxygenisotopic data. The present paper is an attempt to synthesize the available data and to consider various aspects of the China Sea at the Last Glacial Maximum, including its paleogeomorphology, paleo-oceanography and paleosedimentology.At the Glacial Maximum, the sea level was lower than that at present by 130—150 min Dong Hai （the East China Sea） and by 100—120 m in Nan Hai （the South China Sea）. Consequently, Dong Hai together with Huang Hai （the Yellow Sea） and Bohai Gulf was reduced into an elongated trough with an area of less than one third of its present size, while Nan Hai became a semi-closed sack-like-shaped gulf. All the large rivers like Changjiang （Yangtze River）, Huang He （Yellow River）, Zhujiang （Pearl River） and Red River had their prolonged lower reaches on the place of the present continental shelf, emptying directly into the steep continental slope. Therefore, the suspended load of the sea water and the fine-grain clastic sedimentation rate upon the continental slope, especially near estuaries, was much higher than it is now, whereas the percentage of carbonates in bathyal deposits of that stage was much lower. Hence, the Late Quaternary CaCO3 percentage curves of cores taken from the northern continental slope of Nan Hai and from the Okinawa Trough are similar to those from the Atlantic, showing high values for the interglacial and lower values for the glacial stages.During the Glacial Maximum, Polar Front in the Pacific shifted southward and Oyashio cold water might influence the northern end of the paleo-Dong Hai. Meanwhile, temperate waters of the northern Pacific could migrate southward to reach Bashi Strait and partly enter the paleo-Nan Hai. The western passway of the Equatorial Warm Water into Nan Hai was cut off, and the post- or inter-glacial trans-basinal surface circulation pattern in Nan Hai was replaced by a semi-closed clockwise （summer） or counterclockwise （winter） pattern. The Coastal Currents with diluted water from estuaries were displaced to the continental slope and were running southward, in winter, being driven by the northeastern monsoon. The general effect of all these factors was a significant decrease of winter sea surface temperature at the glacial episodes. For example, the glacial/interglacial variation of winter sea surface temperature in the northern slope of Nan Hai （6—9℃） and the summer/winter variation （8—10℃） far exceed those in the Pacific at similar latitudes.The above-described surface circulation pattern of the ice-age China Sea is speculative in nature, and much more work is needed to prove and revise it. Vertical and deep-water circulation, CCD position, possible reduction of oxygen content in bottom water, biological productivity, migration route of brackish-water fauna between the Northern and Southern Hemisphere—these are mentioned examples of topics for further study of the ice-age China Sea. |
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