Characteristics of tidal-bore deposits and facies associations in the Qiantang Estuary, China
Characteristics of tidal-bore deposits and facies associations in the Qiantang Estuary, China
复制标题
DOI：
10.1016/j.margeo.2013.11.012
复制
发表时间：
2014-02
期刊：
影响因子：
2.9
通讯作者：
D. Fan;Junbiao Tu;Shuai Shang;Guofu Cai
中科院分区：
文献类型：
--
作者：
D. Fan;Junbiao Tu;Shuai Shang;Guofu Cai
在岩心地层和粒度资料的基础上，研究了钱塘江口潮孔沉积特征，并综合了其与其他沉积相的横向和纵向对比。一个典型的潮孔和伴生流沉积包体通常由(1)一个波浪形/平面侵蚀基底开始，上覆(2)一个巨大的砂质层，(3)一个平行层状或一些薄的异质层状砂质层。沉积单元，尤其是平行层状体，容易变形为具有泄水构造的卷曲层理、火焰和沸腾砂块。在河口中部，主河道和下潮滩的潮孔沉积物（tmd）向中潮滩的tmd和异质岩床交替层过渡，再向上潮滩的不完全潮韵律岩过渡。潮汐泥质沉积物通常比潮汐砂质沉积物（TSDs）更粗，分选程度更低，而潮汐泥质沉积物（tmd）的颗粒更细，分选程度更低，正偏度也更低。因此，二元尺寸参数标绘是区分这三种成因沉积层类型的有效工具。沿中轴线，三种相划分较为明显，分别为：(1)河口外的线状沉积脊和侵蚀槽，(2)河口中部的tmd，(3)河口上部的粗质河流沉积。钱塘江河口三段式相模式与其他已知的潮汐主导的河口相模式相似，但首次在沉积相中强调潮孔沉积，并利用详细的判别结构和构造特征。这些方法提供了更好地了解潮孔过程及其在现代和古代大潮至高潮河口沉积物弥散和相形成中的重要作用的潜力。
The characteristics of tidal-bore deposition in the Qiantang Estuary are studied on the basis of core strata and grain-size data, and lateral and longitudinal associations with other sedimentary facies are synthesized. A typical depositional package by tidal bores and associated flows is generally initiated with (1) an undular/planar erosion base, overlain by (2) a massive sandy bed, and (3) a sandy bed with parallel laminations or some thinly heterolithic beds. The depositional units, especially the parallel laminations, are prone to deformation into convolute bedding, flames, and boiled sand patches with water-escape structures. In the middle estuary, tidal-bore deposits (TBDs) at the main channel and the lower tidal flat transit laterally into alternative beds of TBDs andz heterolithic beds at the middle tidal flat, and then toward incomplete tidal rhythmites on the higher tidal flat. TBDs are generally coarser and less sorted than tidal sandy deposits (TSDs), and tidal muddy deposits (TMDs) have finer grains, less sorting and lower positive skewness than either TSDs or TBDs. Therefore, bivariate plotting of size parameters is a useful tool to differentiate between these three genetic sedimentary bed types. Along the axis, three facies divisions are obvious and consist of: (1) linear depositional ridges and erosion troughs at the outer estuary, (2) TBDs at the middle estuary, and (3) coarse fluvial deposits at the upper estuary. The tripartite facies model of the Qiantang Estuary is similar to other well-known tide-dominated estuarine facies models, but it is the first to stress tidal-bore deposition in the sedimentary facies using detailed discriminative textural and structural characteristics. The approaches offer the potential to better understand tidal-bore processes and their important role in sediment dispersion and facies formation within modern and ancient macrotidal to hypertidal estuaries.