| 海南岛洋浦湾沉积作用研究 |
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| 引用本文： | 王颖,朱大奎.海南岛洋浦湾沉积作用研究[J].第四纪研究,1996,16(2):159-167. |
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| 作者姓名： | 王颖 朱大奎 |
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| 作者单位： | 南京大学海岸与海岛开发国家试点实验室 |
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| 摘 要： | 本文对海南岛洋浦湾海域的洋浦湾、新英湾、洋浦深槽及拦门沙浅滩的沉积环境和沉积特征做了描述、讨论，对河流、海岸侵蚀和珊瑚礁生物的３种沉积物来源及数量做了分析计算，得出其总量为９×１０4ｍ３／ａ。根据钻孔柱状样的14Ｃ及210Ｐｂ分析，得出８０００ａＢ．Ｐ．以来沉积速率为０．１～０．２ｃｍ／ａ，近百年来沉积速率为１～２ｃｍ／ａ。
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| 关 键 词： | 沉积作用 潮汐汊道 |
| 收稿时间： | 1994-02-15 |
| 修稿时间： | 1995-11-20 |
SEDIMENTARY PROCESSES IN YANGPU BAY,HAINAN ISLAND,CHINA |
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| Wang Ying,Zhu Dakui.SEDIMENTARY PROCESSES IN YANGPU BAY,HAINAN ISLAND,CHINA[J].Quaternary Sciences,1996,16(2):159-167. |
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| Authors: | Wang Ying Zhu Dakui |
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| Institution: | State Pilot Laboratory oj Coast and Island Exploitation, Nanjing University, Nanjing 210093 |
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| Abstract: | Yangpu Bay is located on the northwest coast of Hainan Island.It is composed of an outer Yangpu Bay, and an inner Xinying Bay.Xinying Bay is a tidal embayment with an area of 50km2. The mouth of the embayment, referred to as Baimajing Strait is 550m wide and has a cross-sectional area of about 50km2.Two rivers enter the embayment from the east (Dashui Jiang) and from the southeast (Chun Jiang), respectively. Their combined drainage basin area is 1 419 km2. Fluvial sediment has formed two distinctive river deltas.The main tidal channel extends from Baimajing Strait to the ebb tidal delta located at the mouth of the bay. It is 10km long, 400～500m wide and 5～25mdeep. The bottom sediments of the main channel consist of three distinctive,stratigraphic units. The upper layer is muddy marine sediment; the underlying middle layer is composed of sand and gravel deposited by river currents and the lowermost layer consists of silt and clay size particles typical of Zhanjiang Formation sediments. The main channel is an ancient river valley that was eroded along two major faults in pre-Holocene time. During the Holocene, a rise in relative sea level drowned the ancient river valley. The upper and lower reaches of the channel became the sites of sediment deposition that eventually infilled those parts of the ancient river valley. However, the channel area between Baimajing and the ebb tidal delta was kept open because of daily scouring of deposited sediment by powerful tidal currents.An ebb tidal delta at the western end of the tidal channel is characterized by shoals having a maximum water depth of about 5m. This shallow area is about 400m long and 80～150m wide. Its stratigraphy consists of the same three layers observed in the channel sediments.Block gate shoal (ebb tidal delta) has developed in three stages. Initially, prior to 8000 aB. P., the channel was cut by river currents which eroded the Zhanjiang Formation and deposited the 7m thick layer of sand and gravels.Secondly, during the Holocene relative sea level rise, the entire embayment (inner and outer harbour area) was flooded. Finally, a tidal inlet, which developed in the bay, deposited marine mud resulting in a gradual shoaling of the ebb tidal delta until it attained its present depth of about 5m. Core data suggest that this approximate water depth has been maintained over the past 3 000 years with net deposition of only about 70 cm since that time. A large sand bank forms the south side of Yangpu Bay. The area of the bank lying above the zero metre contour is about 2. 5 km2. The bank has developed on an erosional platform of Zhanjiang Formation sediment. It forms a thin veneer of about 0～2m in thickness on the platform surface. Bathometric records indicate that, between 1955 to 1980, this veneer area increased by about 0. 7km2.An area delineated by water depths less than 2m represents about 40% of the total area of the bay. This area also shows an enlargement of about 0.7km2, an increase of approximately 5%.Sediment dynamics of Yangpu Bay are characterized as: (1) There is100×106～200×106m3 tidal prism:The mean surface water tidal current speed is > 1m/ s and the bottom water mean current speed is > 0. 25m/s at the narrow entrance of Baimajing. The large volume of the tidal prism and the level of tidal current speed are important in avoiding siltation of the navigation channel. (2)The speed of the flood current is smaller than the ebb current; flood tide period is longer than the ebb tide by two or three hours. The flood tidal current approaches Yangpu Harbour through the outer harbour sand bank and then enters the Xinying Bay. In the bay, the current divides into two branches that follow two channels. The main flood current is in the south branch and the main ebb now is in the north branch. The ebb current (3/4 of water quantity) flows out mainly along the deep channel, and the remainder passes through the outer harbour sand bank to return back to sea. The velocity of the ebb current decreases from the inner harbour to the outer bay, but it is still powerful eno |
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| Keywords: | sedimentary processes tidal inlet |
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