长江口圆陀角附近泥沙输移趋势、岩芯沉积物粒度特征及其环境意义

发布时间：2018-01-11 04:15

本文关键词：长江口圆陀角附近泥沙输移趋势、岩芯沉积物粒度特征及其环境意义　出处：《南京大学》2014年硕士论文　论文类型：学位论文

【摘要】：圆陀角位于江苏海岸的南端,属于长江口北翼快速淤涨的海岸,其独特的潮滩沉积环境和复杂的沉积动力过程,决定了该区域对海岸环境变化响应十分敏感,径流、波浪、潮汐、沿岸流及风暴潮是影响圆陀角附近潮滩地貌动态变化的主要因素。本文以长江口北翼圆陀角附近潮滩为研究对象,针对该区域海岸动力环境复杂、物源丰富、受人类活动影响较大等特点,通过野外观测和潮滩沉积物粒度参数特征、137Cs测年分析研究,结合沿岸沙坝沙嘴地貌形态的遥感影像分析,从沉积泥沙输移趋势、现代沉积速率、潮滩沉积粒度对人类活动的敏感响应等方面,对圆陀角附近潮滩近岸泥沙的输运过程、泥沙来源及沉积特征进行了研究。恒大围垦大堤外侧海滩表层沉积物粒度实验结果表明,研究区砂质海滩表层沉积物以细砂级为主、分选性较好、正偏,由于受人类大规模围垦活动的影响,圆陀角附近潮滩的水动力发生了较大变化,水动力明显增强,细颗粒沉积物很难在近岸沉降。受围垦活动影响,恒大围垦大堤外侧潮滩类型逐渐由粉砂淤泥质潮滩转变成砂质海滩,沉积物粒度参数平面分布特征反映了海滩沉积与近岸的沙坝-沟槽地形有很好的对应关系。柱状岩芯沉积物粒度参数特征表明,柱状岩芯采样点附近区域潮滩沉积物的主要成分为砂质粉砂和粉砂,表明该区域主要为细颗粒沉积物堆积区。YTJ-5沉积物粒度呈现出自底部向上沉积物颗粒逐渐变细的特点,属于典型的潮滩沉积。在70cm深度以上含有较多的植物根系,沉积物沉积速率明显增强,反映出圆陀角附近海岸大规模引种互花米草有利于加快潮滩沉积物沉积,起到了很好的护岸促淤作用。岩芯沉积物在深度为100-160cm之间连续出现了多个粗粉砂沉积层,可能与风暴潮影响有关,反映了风暴潮是短时间内改变潮滩沉积过程的重要动力之一。YY孔岩芯自底部向上沉积物颗粒呈现出先变细再变粗的特征,岩芯从底部至116cm深度,随着潮滩的不断淤高,沉积物颗粒不断变细,反映了受人类大规模围垦活动影响之前潮滩的自然淤涨过程。116cm以上沉积物颗粒较粗,主要是受近期大规模围垦筑堤活动的影响。岩芯粒度特征反映了河口海岸环境的变化,潮滩沉积对风暴潮及人类活动的敏感响应。 137Cs剖面所反映潮滩沉积速率显示,自20世纪60年代以来圆陀角附近潮滩沉积物的平均沉积速率随着潮滩的淤积增高而降低。但是由于受人类大规模引种互花米草活动的影响,在1975-1986年之间,圆陀角附近潮滩沉积物沉积速率快速增加,达到4.73cm/a,反映出人类大规模引种互花米草起到了很好的促淤护岸效果,改变了淤泥质海岸的沉积环境。泥沙输运影响着潮滩地貌形态和沉积结构的形成和发展,圆陀角附近海岸发育一系列呈长条状的且不断向东南方向延伸的沙嘴。提取分析了这些沿岸沙嘴影像所反映的地貌形态特征数据,发现圆陀角近岸海域的苏北沿岸流输沙是塑造圆陀角附近潮滩地貌的重要因素和过程。
[Abstract]:The round corner is located in the Jiangsu south coast, which belongs to the rapid siltation of the north wing of the coast, its unique sedimentary environment and complex sedimentary dynamic processes, determines the region sensitive response to coastal environmental change runoff, tides, waves, coastal current and storm surge is the main factor affecting the round the corner the dynamic changes of tidal landform. The Yangtze River Estuary north wing YUANTUOJIAO point near the beach as the research object, according to the regional coastal complex dynamic environment, abundant material sources, characteristics affected by human activities, through field observation and tidal flat sediment grain size parameters, analysis of 137Cs years, combined with the analysis of remote sensing the image of the topography of longshore sands spit from the trend, the modern deposition of sediment transport, deposition rate, sediment particle size on the aspects of human activity sensitive response. The transport process of the round corner of tidal flat sediment. The source and sedimentary characteristics of sediment have been studied.
Hengda reclamation embankment lateral beach surface sediment granularity. The experimental results show that the sandy beach surface sediments in the study area of fine sand level, good sorting, positive bias, due to large-scale human reclamation activities, changed greatly the hydrodynamic YUANTUOJIAO point near the tidal power, water increased, fine sediments are hard in the coastal settlement. By reclamation, reclamation of tidal flat type levee Hengda lateral silt change gradually from mudflat into sandy beach, plane distribution characteristics of sediment grain size reflects the good corresponding relationship between the sand bar and beach sediments with coastal trench topography.
Show that the grain size parameters like sediment cores, the main component of cylindrical core sampling area near the intertidal sediments of sandy silt and silty sand, indicating that the region is mainly fine particle size of sediment accumulation zone.YTJ-5 sediments from bottom to top shows characteristics of sediment particles tapering, belong to sedimentary typical plants. The root contains more in the above 70cm depth, the sediment deposition rate increased significantly, reflecting the YUANTUOJIAO point near the coast to speed up large-scale introduction of Spartina alterniflora in intertidal sediment deposition, played a very good role in revetment and siltation. The sediments in the depth of 100-160cm between the continuous emergence of a number of coarse silt deposited layer, and may storm surge, reflecting the storm surge is one of the most important power.YY core change of sedimentary process in a short period of time from the bottom to the top of sediment particles showing The first thinning then coarsening characteristics, core from the bottom to the depth of 116Cm, with the continuous accretion of intertidal flat, sediment thinning, reflect the influence of human activities before the large-scale reclamation of tidal flat natural siltation process of sediments above.116cm coarse particles, which is mainly influenced by the recent large-scale reclamation activities. The size of embankment the core features reflect the changes of estuarine and coastal environment, sensitive response of sedimentary of storm surge and human activities.
137Cs profiles reflect sedimentary rate, since the 1960s round of angle of tidal flat sediments near the average deposition rate decreased with the increase of tidal flat sedimentation. But due to the impact of human activities in the large-scale introduction of Spartina alterniflora, between 1975-1986 years, the round of angle near the intertidal sediment deposition rate increased rapidly, reaching 4.73cm/a reflect the human scale introduction to siltation of Spartina alterniflora revetment effect is very good, has changed the sedimentary environment of muddy coast.
Sediment transport affects the formation and development of tidal flat geomorphology and sedimentary structure, the round angle near the coast is characterized by a series of long strip-shaped and continuously to the south-east spit. The morphologic feature extraction and analysis of these data along the spit reflected image, found the Subei Coastal YUANTUOJIAO point nearshore waters flow the sand is an important factor shaping the round angle near the beach geomorphology and process.

【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P736.21

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