Tidal meander migration and dynamics: A case study from the Venice Lagoon
Tidal meander migration and dynamics: A case study from the Venice Lagoon
复制标题
DOI：
10.1016/j.marpetgeo.2017.04.012
复制
发表时间：
2017-11-01
影响因子：
4.2
通讯作者：
Marani, Marco
中科院分区：
文献类型：
--
作者：
D'Alpaos, Andrea;Ghinassi, Massimiliano;Marani, Marco
曲折模式是潮汐景观的普遍特征，对潮汐通道网络的动力学和它们所解剖的潮间带平台的地层学产生关键影响。尽管它们在景观演变中的重要性和它们的普遍性，潮汐曲流受到较少的关注时，与河流相比较。为了提高目前的理解潮汐曲流迁移及其可能的地层影响，我们分析了一系列的航空照片和卫星图像（从1938年至今）的曲折的潮汐通道在威尼斯泻湖，经历了多个截止事件在其演变过程中。所考虑的弯曲的迁移率在0.06-0.17米/年的范围内，而每单位宽度的迁移率在0.6和2.5%年（-1）之间变化。详细的高分辨率地貌，沉积和年代学分析进行了废弃的曲流弯曲，经历了这些截止之一。航空照片之前和之后的截止事件（1938年和1955年，分别）被用来推断迁移的最小速度（约0.10密耳）。沉积物岩心也收集了沿着一个横断面通过曲流颈部，以评估在截止事件期间的粒度变化，沉积速率，并获得进一步了解曲流弯曲的迁移速度。空间分布的沉积相（点坝砂，牛轭湖，盐沼泥），粒度分析，和210铅和铯-137年代学突出的曲流截止逐渐发生约70年前，目前的平均迁移率为0.25米/年。这样一个程序来估计曲流迁移率从地层数据显示是特别有用的，在没有高时间分辨率的遥感图像。所使用的方法的有效性和高的空间和时间分辨率的数据要求进一步调查和分析的类型在此提出的，进一步突出了现代模拟古代潮汐沉积物的研究领域的潜力。(C)2017爱思唯尔有限公司版权所有
Meandering patterns are universal features of tidal landscapes, and exert a critical influence on the dynamics of tidal channel networks and on the stratigraphy of the intertidal platforms they dissect. Despite their importance in landscape evolution and their ubiquity, tidal meanders have received less attention when compared to their fluvial counterparts. To improve current understanding of tidal meander migration and its possible stratigraphic implications, we analysed a sequence of aerial photographs and satellite images (from 1938 to present) of a meandering tidal channel in the Venice Lagoon, which experienced multiple cutoff events during its evolution. Migration rates of the considered bends are in the range of 0.06-0.17 m/y, whereas migration rates per unit width vary between 0.6 and 2.5% yr(-1). Detailed high-resolution geomorphological, sedimentological, and geochronological analyses were carried out for an abandoned meander bend, which experienced one of these cutoffs. Aerial photographs before and after the cutoff event (1938 and 1955, respectively) were used to infer a minimum velocity of migration (about 0.10 milt). Sediment cores were also collected along a transect crossing through the meander neck in order to evaluate changes in grain size, sedimentation rates during the cutoff event, and gain further insight into the velocity of migration of meander bends. The spatial distribution of sedimentary facies (point-bar sand, oxbow lake, and salt-marsh mud), grain-size analyses, and 210 Pb and Cs-137 chronologies highlighted that meander cutoff occurred progressively around 70 years before present with an average migration rate of 0.25 m/year. Such a procedure to estimate meander migration rates from stratigraphic data reveals to be particularly useful in the absence of high-temporal resolution remotely sensed-images. The effectiveness of the methods used and the high spatial and temporal resolution of the data call for further investigations and analyses of the type proposed herein, furthermore highlighting the potential of the study area as modern analogue for ancient tidal deposits. (C) 2017 Elsevier Ltd. All rights reserved.