| 河流输沙与中国海岸线变化 |
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| 引用本文： | 李从先,张桂甲.河流输沙与中国海岸线变化[J].第四纪研究,1996,16(3):277-282. |
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| 作者姓名： | 李从先 张桂甲 |
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| 作者单位： | 同济大学海洋地质系 |
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| 摘 要： | 我国沿海地区构造升降使入海河流沉积物分布不均，９５％于构造下降地区入海，构造上升区接纳的河流泥沙不足５％，入海河流泥沙分布不均是我国海岸基本类型和海岸线变化差别的主要原因。在此基础上讨论了最大海侵的范围及时间，海岸线变化的趋势、速度和周期以及河流输沙对未来海岸线变化预测的影响。
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| 关 键 词： | 海岸线 海岸环境 河流输沙 海平面上升 |
| 收稿时间： | 1995-10-18 |
| 修稿时间： | 1995-11-06 |
RIVERINE SEDIMENTS AND COASTLINE CHANGES IN CHINA |
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| Li Congxian, Zhang Guijia.RIVERINE SEDIMENTS AND COASTLINE CHANGES IN CHINA[J].Quaternary Sciences,1996,16(3):277-282. |
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| Authors: | Li Congxian Zhang Guijia |
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| Institution: | Department of Marine Geology and Geophysics,Tongji University, Shanghai 200092 |
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| Abstract: | The uplifting of the Qinghai-Tibet Plateau generated large rivers, and consequently,large volume of riverine sediments were deposited at the coastal seas. Since then, the coastal zones of China have been an area rich in riverine deposits. Chinese coastline crosses both tectonic uplift and depression belts, and numerous fault-basins exist at the uplift belts. The tectonic depression areas, including the depression belts and the fault-basins at the uplift belts, accommodate about 95% of the riverine sediments, whereas the length of the coastline at these areas is only 21.6% of the total Chinese coastline; the tectonic uplift areas accommodate only 5% of the riverine sediments, but the length of the coastline is 78.4% of the total. Therefore, the sediment amount deposited at the depression areas within per kilometer is more than 40 times larger than that at the uplift areas. Sediments at the uplift areas are mainly sands and gravels, forming steeper slope coasts, while sediments at the depression areas are mainly silty sands and clay, forming gentle slope coasts. TIs distributive unbalance of riverine sediments along the coasts and the difference of the coastal slope control the coastline changes at various areas in China.The extent and time of the maximum Holocene transgression depend on rates of sea-level rise, sedimentary rates, and coastal slope gradients. The maximum transgression was larger in extent, and began earlier (about 7 500 ～ 7 000aB.P.) at the large-river deltaic areas because of the higher sedimentary rates and gentler coastal slope there; while it was smaller and began later (about 6 000 ～ 5 000aB.P.) at the tectonic uplift coastal zones because of the lower sedimentary rates and steeper coastal slope. Specifically, within one estuarine-deltaic area, the maximum transgression at the river mouth area was larger and began earlier than that at both flanks.Chinese coastline has experienced an evolution cycle resulted from the transgression and regression at the strand and deltaic plains since the Holocene epoch. The durations of coastline evolution cycles may last several thousands and ten thousands years, which are not isochroinc at any two adjoining points within a profile perpendicular to coastline. Coastal bars on the strandplains at the tectonic depression areas record the subcycles of the coastline changes since the maximum transgression, and show a duration of several hundred years. Migration of main river channels, alternation of flood and dry seasons, changes in waves and semidiunal and forthightly tide cycles, all of them can result in periodic progradation or regradation of the coastline, and the duration of the cycles are from one to several years.Future changes in Chinese coastlines are dependent on various natural and human factors, terrigenous and marine, global and regional, which varied greatly in temporal scales, so it is much complex to predict these changes. The way, trying to obtain flooded area and possible economic lose based on the predicted sea-level rise and the elevations of the coastal lowlands, is hardly applicable to the prediction of the Chinese coastal lowlands. To predict correctly the coastline changes, it is necessary to determine the fundamental and critical factors that control the changes,and to study the relationship and evolution trends of primary and secondary factors. |
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| Keywords: | coastline coastal environment riverine sediments sea-level rise |
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