Sedimentary Characteristics of theModern Tidal Flat of Jiuduansha Shoal in Changjiang Estuary
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摘要: 根据2003年对长江河口九段沙潮间带和潮上带的现场调查和室内对沉积构造、粒度分布、矿物组成、沉积速率等的分析,对九段沙现代潮滩的沉积特征进行了研究。研究表明九段沙潮间带以小型交错层理为主,波痕发育,粒度主要为细砂至粗粉砂;潮上带主要为水平层理,粒度主要为中细粉砂。潮间带和潮上带的沉积矿物组成非常接近。沉积速率以潮间带低而潮上带高为特点。Abstract: Based on the field surveys in 2003 and laboratory analysis of the samples which taken from Jiuduansha Shoal, the sedimentary structure, grain size distribution, assemblages of the clayminerals and the sedimentation rates are studied aswell. The sedimentation rate is determined by 210 Pb method, and the results show that the sedimentation rate of the sup ratidal zone ismuch higher than that in the inter-tidal zone. The intertidal zone of the Jiuduansha shoal are mainly micro-wave and cross bedding, and sediments are dust-color fine sand and coarse silt, this zone is affected by the wave and tidal currents, some special sedimentary structure formed, and boulder clay, ripple and erosion ridge existed, these structure formed under wave processes. Sup ratidal zone are mainly horizontal bedding, and sediments are mainly middle-fine silt, because of dominant species are Phramites australis and Scirpus mariqueter on the supratidal zone, here is the lower energy sedimentary environment, and sedimentary structure are horizontal bedding,and mean size is between 5.0-27.0Φ. Clayminerals are similar between inter-tidal zone and sup ratidal zone, claymin-eralsmainly are illite, montmorillonite, kaolinite and chlorite, but they content on sup ratidal and intertidal zone are different. The sedimentation rate on the intertidal zone are 0.735cm / a, and on the supratidal zone, the sedimentation rate are 3.342 cm / a, higher than that on the intertidal zone.
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Key words:
- Yangtze River /
- Jiuduansha shoal /
- modern tidal flat /
- sedimentary characteristics
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