Sedimentary Characteristics of theModern Tidal Flat of Jiuduansha Shoal in Changjiang Estuary

XIE Xiao-ping; WANG Zhao-yin; SHEN Huan-ting

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.

Sedimentary Characteristics of theModern Tidal Flat of Jiuduansha Shoal in Changjiang Estuary

1. Department of Hydraulic aod Hydro-electrical Engineering, Tsinghua University, Beijing 100084;

2. School of Resources and Planning, Qufu Normal University, Qufu, Shandong 273165;

3. State Key Lab of Estuarine and Coastal Sediment Dynamics and Morphodynamics, East China Normal University, Shanghai 200062

Received Date: 2005-01-19

Rev Recd Date: 2005-05-20

Publish Date: 2005-12-10

Key words:

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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Sedimentary Characteristics of theModern Tidal Flat of Jiuduansha Shoal in Changjiang Estuary

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