Mechanism for retreating barriers to autogenically form periodic deposits on continental shelves
Mechanism for retreating barriers to autogenically form periodic deposits on continental shelves
复制标题
撤退障碍以在大陆架上自生形成周期性沉积物的机制
作者：
Ciarletta, Daniel J.;Lorenzo-Trueba, J.;Ashton, A.D.
由于屏障海侵而保存在陆架海床上的残障沉积物是被动砂质边缘的共同特征，偶尔会发现多个沉积物均匀分布在相隔几到几十公里的地方。这些沉积物的形成通常被归因于异体越位过程，最常见的是海平面快速上升的时期，尽管地形变化或外部沉积物供应也被认为是原因。在这里，我们提出了一种机制，即在海平面不断上升的情况下，岸面动力学和沉积物向陆地冲过之间的自生反馈可以形成有规则间隔的陆架沉积物。屏障海侵的一个简单的形态动力学模型显示了一种周期性后退模式，在这种模式下，内部动力学产生了平移和沉积的交替事件，产生了低起伏的屏障沉积物跨岸沉积，其间距为公里级，随着陆架坡度的逐渐增加，间距会增加。模拟的屏障在陆架斜坡上形成自生的部分越界，梯度在1至3米/公里之间，海平面上升速率在1至18毫米/年之间。该模式产生的沉积物与来自世界各地的越界障碍的实地观测相关联，在陆架坡度和间距（波长）之间具有反比关系。这一结果表明，离散的残障体沉积物可能不是外部强迫变化的唯一指示，目前稳定的障壁岛可能容易受到快速行为转变的影响。
Relict barrier deposits preserved on the shelf seabed from barrier transgression are common features of passive, sandy margins, with multiple deposits occasionally found evenly spaced several to tens of kilometers apart. The formation of these deposits has typically been ascribed to allogenic overstepping processes, most commonly to episodes of rapid sea-level rise, although changes in topography or external sediment supply have also been invoked. Here, we present a mechanism whereby autogenic feedbacks between shoreface dynamics and the landward overwash of sediments can form regularly spaced shelf deposits even with constantly rising sea level. A simple morphodynamic model of barrier transgression exhibits a mode of periodic retreat whereby alternating episodes of translation and aggradation arise from internal dynamics, generating low-relief cross-shore deposits of barrier sediment with kilometer-scale spacing that increases for more gradual shelf slopes. Modeled barriers develop autogenic partial overstepping on shelf slopes with gradients between 1 and 3 m/km and for rates of sea-level rise between 1 and 18 mm/yr. Deposits produced by the model correlate with field observations of overstepped barriers from around the world, sharing an inverse relationship between shelf slope and spacing (wavelength). This result suggests that discrete remnant barrier deposits may not be exclusively indicative of changes in external forcing and that currently stable barrier islands may be susceptible to rapid behavioral transitions.
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影响因子：
2.9
作者：
D. Forbes;R. Taylor;J. Orford;R. Carter;J. Shaw
通讯作者：
D. Forbes;R. Taylor;J. Orford;R. Carter;J. Shaw
在颈部、烤叉上：控制自由烤叉的形状
影响因子：
3.4
作者：
Ashton, A. D.;Nienhuis, J.;Ells, K.
通讯作者：
Ells, K.
研究自生过程对同种异体强迫的响应：实验地貌学和地层学
DOI：
10.1002/9781118920435.ch5
发表时间：
2014
期刊：
Journal of Geophysical Research: Earth Surface
影响因子：
--
作者：
Wonsuck Kim;A. Petter;K. Straub;D. Mohrig
通讯作者：
D. Mohrig
影响因子：
3.9
作者：
Lorenzo-Trueba, Jorge;Ashton, Andrew D.
通讯作者：
Ashton, Andrew D.
障壁岛成因：来自美国东部大西洋中部大陆架的证据
影响因子：
2.8
作者：
D. Swift
通讯作者：
D. Swift