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长江口细颗粒物质来源丰富、水动力作用活跃,近年来又受到三峡大坝等流域大型工程的影响,因此其水下三角洲沉积层序对自然过程(物源变化、潮汐水道地形调整、风暴潮事件等)和人类活动(航道疏浚等)的响应成为一个重要的科学问题。对覆盖长江口水下三角洲的31个站位的沉积物柱样进行了粒度分析,并对其中30个站位的柱样进行了~(210)Pb测定,结果表明,长江口物质主要是来源于现代流域供给,少数站位的砂质沉积则代表海底侵蚀。沉积物柱状样的平均粒径有4种类型的垂向分布趋势:Ⅰ.向上细化,Ⅱ.垂向稳定,Ⅲ.垂向波动式变化,Ⅳ.向上粗化。分别对应于不同的地貌部位和冲淤动态。~(210)Pb比活度垂向变化有4种类型:1)标准衰变剖面,2)均一~(210)Pb_(total)活度剖面,3)分段式衰变剖面以及4)分段式衰变与倒置衰变复合剖面。4种类型的空间分布格局显示,多数站位不是连续堆积的。不同站位的柱状样沉积记录代表了长江口水下三角洲沉积对各种因素(沉积动力过程、流域水库建设等)的复杂响应模式。长江口水下三角洲粒度与~(210)Pb的空间分布特征指示了研究区的多种沉积动力特征,如物源变化、水动力变化、相邻区域的侵蚀搬运与二次堆积、水动力强弱的空间差异以及事件沉积的影响。
Due to the rich source of fine particulate matter and active hydrodynamic forces in the Yangtze River estuary, it has also been affected by large-scale projects such as the Three Gorges Dam in recent years. Therefore, the sedimentary sequence of the subaqueous delta has a great influence on natural processes (source changes, tidal channel topography adjustment, Events, etc.) and human activities (waterway dredging, etc.) have become an important scientific issue. Sediment samples of 31 stations covering the Yangtze River Estuary subaqueous delta were analyzed for particle size and ~ 210 Pb concentrations were measured for 30 of them. The results show that the material of the Yangtze Estuary is mainly derived from The supply of modern watershed, sandy sediments of a few stations represent seafloor erosion. There are four types of vertical distribution of the average particle size of the sediment-like sediment: Ⅰ. Upward refinement, Ⅱ. Vertical stability, Ⅲ vertical fluctuations, Ⅳ upward coarsening. Corresponding to different parts of the landscape and scour and silt dynamics respectively. There are four types of vertical variation of ~ (210) Pb specific activity: 1) standard decay profiles, 2) uniform ~ 210 Pb total activity profiles, 3) fractional decay profiles and 4) Decay and Inverted Decay Compound Profile. The four types of spatial distribution show that most stations are not continuously stacked. The column-like sedimentary records at different stations represent the complex response patterns for various factors (sedimentation dynamics, basin construction, etc.) in the delta of the Changjiang Estuary. The Yangtze River estuary subaqueous delta and the spatial distribution of ~ (210) Pb indicate a variety of sedimentary dynamics such as source changes, hydrodynamic changes, erosion and secondary accumulation in adjacent areas, hydrodynamic strength The spatial difference and the impact of event deposition.