The grade index model as a rationale for autogenic nonequilibrium responses of deltaic clinoform to relative sea‐level rise
The grade index model as a rationale for autogenic nonequilibrium responses of deltaic clinoform to relative sea‐level rise
复制标题
等级指数模型作为三角洲斜形对相对海平面上升的自生非平衡响应的基本原理
DOI：
10.1111/bre.12418
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发表时间：
2020-04
期刊：
影响因子：
3.2
通讯作者：
Tetsuji Muto
中科院分区：
文献类型：
--
作者：
Junhui Wang;Hajime Naruse;Tetsuji Muto
品位指数（Gindex）是一个无量纲数，表示从上游供应到三角洲的沉积物的陆上分配与陆上和水下分配的单位时间体积比。它最初是为了了解在相对海平面稳定的情况下，盆地水深对三角洲分流河道形态动力学的影响而提出的。在这里，我们研究如何上升的相对海平面调制的Gindex，使用几何推理和数值模拟。我们发现，品位指数模型可以解释的三角洲岸线的自动后退，自动淹没的整个系统，和自动中断的三角洲沉积，所有这些都是自生的非平衡响应稳定上升的相对海平面的后果。当三角洲平原的无因次断面积（At*）遇到用Gindex表示的临界值时，海退到海侵阈值（即自动海退的开始）被越过：当At* 低于和高于阈值时，海退和海侵分别持续。海侵方式取决于斜坡条件。如果腹地坡度（γ）比前积坡度（β）陡，则At* 和Gindex都随着相对海平面的上升而减小。最终，当At* = Gindex = 0时，沉积体系经历自动淹没。另一方面，如果γ < β，则At* 和Gindex都增加。后一种斜坡条件最终导致三角洲沉积的自动破碎，之后At* = Gindex = 1。该模型可用于解释和预测相对海平面上升条件下天然三角洲斜坡的地层响应。
Grade index (Gindex) is a dimensionless number given as the volume‐in‐unit‐time ratio of subaerial allocation to both subaerial and subaqueous allocations of sediment supplied to.a delta from upstream. It was originally proposed for understanding the effect of basin water depth on the morphodynamics of delta distributary channels under stationary relative.sea level. We here examine how rising relative sea level modulates the Gindex, using geometrical reasoning and numerical simulations. We find that the grade index model can account for autoretreat of the deltaic shoreline, autodrowning of the whole system, and autobreak of the deltaic sedimentation, all of which are the consequences of autogenic nonequilibrium responses to steadily rising relative sea level. The regressive‐to‐transgressive threshold (i.e. the onset of autoretreat) is crossed when the delta plain's dimensionless basal area (At*) encounters a critical value that is expressed in terms of Gindex: regression and transgression are sustained when At* is below and above the threshold, respectively. The mode of transgression depends on the slope conditions. If the hinterland slope (γ) is steeper than the foreset slope (β), both At* and Gindex decrease as the relative sea‐level rises. Eventually, the depositional system experiences autodrowning when At* = Gindex = 0. If γ < β; on the other hand, both At* and Gindex increase. This latter slope condition eventually causes autobreak of the deltaic sedimentation, afterward of which At* = Gindex = 1. The grade index model is useful for interpreting and predicting the stratigraphic responses of natural deltaic clinoforms in conditions of rising relative sea level.
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影响因子：
2
作者：
T. Muto;R. Steel;J. Swenson
通讯作者：
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影响因子：
5.8
作者：
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通讯作者：
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DOI：
10.2110/pec.08.90.0035
发表时间：
2008-12
期刊：
--
影响因子：
--
作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
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影响因子：
3.5
作者：
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通讯作者：
G. Parker;T. Muto;Y. Akamatsu;W. Dietrich;J. Wesley Lauer