An experimental examination of the theory of shoreline autoretreat

岸线自退理论预测，即使相对海平面[A]的变化率[A]是恒定的(&gt；0)，如果包括泥沙供应速率[S](&gt；0)在内的任何其他盆地动力条件保持不变，岸线也不可避免地在三角洲发育的相对早期阶段开始向陆地后退，最终到达三角洲前缘清晰的角形突然丧失的转折点。这一自退理论通过水槽实验得到了验证，在水槽实验中建立了一个三角洲的微型模型(A=Const&gt；0，S=Const&gt；0)。实验结果和相关概念总结如下。1。海岸线的自动后退已经得到证实。正如理论预测的那样，三角洲经历了岸线向陆地的转向，随后发生了几何断裂事件，而盆地条件没有任何变化。通过对海岸线自退理论的讨论，找到了一种半定量探测古盆地动力条件时间变化的方法。以斯匹茨堡西部中央第三系海槽的古近系海退序列为例，说明了该方法的适用性。一系列的三维实验否定了传统的观点，即沉积体系整个堆积模式的任何重大变化主要是由于外部因素或分配旋回因素的重大时间变化，而不是沉积体系本身的内置或自旋回机制。在海侵阶段，三角洲平原呈阶梯式后退，废弃的三角洲平原被水位上升淹没，保留为多个阶地。三角洲的这种特殊行为与自退缩效应和供沙河流的自旋横向移动过程有关。

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.