An experimental examination of the theory of shoreline autoretreat

海岸线自动后退理论的实验检验

基本信息

批准号：
10640442
负责人：
MUTO Tetsuji
金额：
$ 2.62万
依托单位：
Nagasaki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

The theory of shoreline autoretreat predicts that even if the rate of change of relative sea level [A] is constant (>0) and if any other basin dynamic conditions including the rate of sediment supply [S] (>0) and remain constant, the shoreline inevitably begins to retreat landward at a relatively early stage of delta growth and finally reaches the break point where the clear angular configuration of the delta front is lost suddenly. This autoretreat theory was examined with flume experiments in which a miniature of delta is built under a controlled steady state (A=const>0, S=const>0). The experimental results and related notions are summarized as below.l. The autoretreat of shoreline has been substantiated. Just as predicted from the theory, the deltas experienced the landward turnaround of a shoreline and subsequently the occurrence of a geometrical break event, without any change of basin conditions.2. A semiquantitative method to detect temporal changes in ancient basin dynamic conditions has been found from the discussion based on the theory of shoreline autoretreat. The applicability of this method was illustrated with the Paleogene regressive succession in the Central Tertiary Trough, west Spitsbergen.3. A series of the three-dimensional experiments has given negative evaluation to the conventional notion that any significant change in the entire sediment-stacking pattern of a sedimentary system is principally due to a significant temporal change of an external or allocyclic factor rather than to inbuilt or autocyclic mechanisms within the depositional system itself. In the transgressive phase, the delta plain retreats in a step-like manner, and the abandoned deltaplains, being submerged with water-level rise, are preserved as multiple stepped terraces. This particular behavior of a delta is related to the autoretreat effect combined with the autocyclic lateral-shifting processes of sediment-feeding streams.

海岸线自动后退理论预测，即使相对海平面的变化率[A]恒定（>0），并且如果任何其他流域动力条件，包括沉积物供应率[S]（>0）保持恒定，在三角洲增长的相对早期阶段，海岸线不可避免地开始向陆地后退，并最终达到三角洲前缘清晰的角形结构突然消失的断点。这种自动撤退理论通过水槽实验进行了检验，其中在受控稳定状态下建立了微型三角洲（A=const>0，S=const>0）。实验结果及相关概念总结如下： 1．海岸线的自动后退已得到证实。正如理论预测的那样，三角洲经历了海岸线向陆地的转向以及随后发生的几何断裂事件，而盆地条件没有发生任何变化。2．基于海岸线自动后退理论的讨论，找到了一种半定量检测古盆地动力条件随时间变化的方法。以斯匹次卑尔根岛西部中央第三系海槽的古近纪回归演替为例，说明了该方法的适用性。 3．一系列的三维实验对传统观念给予了负面评价，即沉积系统整个沉积物堆积模式的任何显着变化主要是由于外部或非循环因素的显着时间变化而不是内在或内部因素造成的。沉积系统本身的自循环机制。海侵阶段，三角洲平原呈阶梯状后退，废弃的三角洲平原随着水位上升而被淹没，保留为多级阶梯状阶地。三角洲的这种特殊行为与自退效应和沉积物供给流的自循环横向移动过程相结合有关。