Sediment distribution and depositional processes along the fluvial to marine transition zone of the Mekong River delta, Vietnam
Sediment distribution and depositional processes along the fluvial to marine transition zone of the Mekong River delta, Vietnam
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越南湄公河三角洲河海过渡带沉积物分布及沉积过程
DOI：
10.1111/sed.12489
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发表时间：
2018
期刊：
影响因子：
3.5
通讯作者：
Tamura Toru
中科院分区：
文献类型：
--
作者：
Gugliotta Marcello;Saito Yoshiki;Nguyen Van Lap;Ta Thi Kim Oanh;Tamura Toru
具有河流、潮汐和波浪作用的沿海河流地区被定义为河流向海洋过渡区，可延伸至河口上游数百公里。本研究的目的是提高沉积物分布和沉积过程的理解沿着河流向海洋过渡带使用从湄公河三角洲收集的河床沉积物样品的综合数据集。确定了六种沉积物类型，并解释为反映河流和海洋过程的综合作用。根据沉积物类型组合，湄公河河流-海洋过渡带可细分为上游区和下游区;这两个区之间的边界位于河口上游80至100 km处。上游河道以砾质砂和砂以及偶尔的异石韵律岩为特征，表明推移质供给和沉积主要受河流作用控制，潮汐影响较小。下游河道的特征是杂岩韵律岩，其次是砂和泥，这表明悬浮物的供应和沉积主要受潮汐过程控制，其次是河流的影响。干湿季的沉积物分布表明，沿着河流向海洋过渡带的沉积物动力和沉积过程存在显著的季节变化。上游道表现出较强的河流沉积过程与下属的潮汐影响在雨季和没有沉积弱河流和潮汐过程在旱季。下游道表现出强大的共存的河流和潮汐沉积过程中，在雨季和强大的潮汐沉积过程中，河流的影响可以忽略不计，在旱季。最大湍流存在于沿着河流向海洋过渡区的下游道，在雨季和旱季，并由河流，潮汐和波浪过程的组合驱动。
The area of coastal rivers with a combination of fluvial, tidal and wave processes is defined as the fluvial to marine transition zone and can extend up to several hundreds of kilometres upstream of the river mouth. The aim of this study is to improve the understanding of sediment distribution and depositional processes along the fluvial to marine transition zone using a comprehensive dataset of channel bed sediment samples collected from the Mekong River delta. Six sediment types were identified and were interpreted to reflect the combined action of fluvial and marine processes. Based on sediment‐type associations, the Mekong fluvial to marine transition zone could be subdivided into an upstream tract and a downstream tract; the boundary between these two tracts is identified 80 to 100 km upstream of the river mouth. The upstream tract is characterized by gravelly sand and sand and occasional heterolithic rhythmites, suggesting bed‐load supply and deposition mainly controlled by fluvial processes with subordinate tidal influence. The downstream tract is characterized by heterolithic rhythmites with subordinate sand and mud, suggesting suspended‐load supply and deposition mainly controlled by tidal processes with subordinate fluvial influence. Sediment distributions during wet and dry seasons suggest significant seasonal changes in sediment dynamic and depositional processes along the fluvial to marine transition zone. The upstream tract shows strong fluvial depositional processes with subordinate tidal influence during the wet season and no deposition with weak fluvial and tidal processes during the dry season. The downstream tract shows strong coexisting fluvial and tidal depositional processes during the wet season and strong tidal depositional processes with negligible fluvial influence during the dry season. Turbidity maxima are present along the downstream tract of the fluvial to marine transition zone during both wet and dry seasons and are driven by a combination of fluvial, tidal and wave processes.
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DOI：
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发表时间：
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