长江口各地貌单元沉积构造和粒度分区特征

发布时间：2018-07-06 15:53

本文选题：砂质纹层 + 分粒级频率曲线　；参考：《海洋地质与第四纪地质》2016年04期

【摘要】：根据165个柱状样顶部1m的沉积构造和粒度分析结果,对长江口各地貌单元的沉积物特征进行了规律性总结,以应用于钻孔沉积相的判断。结果显示,河口心滩、上河口段落潮槽和拦门沙为主要砂质沉积区,属于牵引流沉积,分粒级频率曲线的峰值主要出现在63~125μm及125~250μm粒级,且峰值在125~250μm粒级的样品向海逐渐增多。而残留砂沉积物粒径大、分选好,特征明显。其余地貌单元均以泥质沉积为主,典型特征有:(1)潮坪层偶发育,砂质纹层密集;(2)在分粒级频率曲线中,口内涨潮槽主峰以4μm为主,口外涨潮槽变粗为31~63μm占主导,且砂质薄层增多;(3)下河口段落潮槽纹层很多,极薄纹层占主导;(4)南汇边滩分粒级曲线常见双峰现象,平均中值粒径在泥质沉积区最大,部分沉积物位于C-M图的递变悬浮段;(5)三角洲前缘复式河槽沉积物明显细于其他前缘沉积,反映了滞流点附近的弱水动力特征;(6)前三角洲为均质泥,纹层少见,为长江口区最细的沉积。
[Abstract]:Based on the results of sedimentary structure and grain size analysis of 165 columnar samples at the top of 1m, the sediment characteristics of various geomorphological units in the Changjiang Estuary are summarized regularly, which can be used to judge the sedimentary facies in boreholes. The results show that the main sandy sedimentary area is the estuarine core beach, the tidal channel in the upper estuary section and the bar sand, which belongs to the tractive flow deposition. The peak value of the frequency curve of grain size mainly appears at the grain levels of 63 ~ 125 渭 m and 125 ~ (250) 渭 m, and the peak value increases gradually at the level of 125 ~ 250 渭 m. However, the residual sand sediment has large particle size, good separation and obvious characteristics. The other geomorphologic units are mainly muddy, typical features are: (1) the tidal flat is occasionally developed, and the sand grain is dense, (2) in the grain-level frequency curve, the main peak of the intraoral flood trough is mainly 4 渭 m, and the main peak of the in-mouth tidal trough is mainly 4 渭 m, and the outer tidal trough is thickened to 31 ~ (63) 渭 m. And the sand thin layer increased; (3) there are many tidal channel layers in the lower estuary section, and the very thin grain layer dominates; (4) there are two peaks in the grain-grade curve of Nanhui beach, and the mean median particle size is the largest in the muddy sedimentary area. Some of the sediments are located in the progressive suspension section of C-M diagram, (5) the sediment of the delta front composite channel is much smaller than other front sediments, which reflects the weak hydrodynamic characteristics near the stagnation point, (6) the pre-delta is homogeneous mud, and the laminar layer is rare. It is the thinnest deposit in the Changjiang Estuary.
【作者单位】：华东师范大学河口海岸国家重点实验室;上海市地质调查研究院;
【基金】：国土资源部公益项目(201211009)
【分类号】：P737.1

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