Autostratigraphy is the stratigraphy generated by large‐scale autogenesis, developed based on the full recognition of the non‐equilibrium behaviour of depositional systems in response to steady external forcing. The existing autostratigraphic concepts were derived mostly from studies of river deltas growing during a single rise or fall of base level (or relative sea level). The present study challenges to extend the autostratigraphic framework to the alluvial‐shelf system growing through steady base‐level cycles by two‐dimensional tank experiments. During each experimental run, the base level was changed symmetrically, wherein through cycles, the rise and fall had the same constant rate (|R_bl|) and period (T_bl), and thus the same constant amplitude (A_bl), but with no basin tectonism. In total, nine runs with different combinations of |R_bl| and A_bl were performed. The experimental results brought the following implications. (i) The shelf‐transiting active depositional system takes non‐equilibrium responses in earlier base‐level cycles, during each of which the system experiences episodes of degradation with base‐level fall. (ii) After the system has sufficiently grown through cycles, non‐equilibrium responses change into equilibrium responses, whereby the shelf‐transiting alluvial system, whether retrogradational or progradational, is free from degradation and continues to aggrade but with a gradually decreasing rate of aggradation. (iii) The alluvial topset river tentatively but autogenically attains a graded state during the falling limb of an intermediate cycle, which separates the earlier degradation‐inclusive and later aggradation‐sustainable cycles. (iv) The number (or duration) of cycles elapsed prior to this phase‐transition is linearly proportional to the amplitude (or the square of the period) of base‐level cycles, with a coefficient defined by the rates of base‐level change and sediment supply. Such a growth pattern does not necessarily hold when considering long‐term tectonic subsidence or uplift. These notions help to understand the stratigraphic architectures of natural alluvial‐shelf systems evolved through base level cycles.

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稳定基础水平周期内冲积层系统生长的地层学建模：二维储罐实验

自地层学是由大规模自生作用产生的地层，它是在充分认识到沉积系统对稳定外力作用的非平衡行为的基础上发展起来的。现有的地层学概念主要源自对基准面（或相对海平面）单次上升或下降期间河流三角洲的研究。本研究面临的挑战是通过二维储罐实验将地层学框架扩展到通过稳定的基层循环而增长的冲积层系统。在每个实验运行期间，基准电平对称地变化，其中在整个周期中，上升和下降具有相同的恒定速率（| R _bl |）和周期（T _bl），因此具有相同的恒定幅度（a _bl），但没有盆地构造。总共有9个运行，它们具有|的不同组合 R _bl | 和一个_bl被执行。实验结果带来以下启示。（i）陆架上空活动沉积系统在较早的基层周期中获得非平衡响应，在每个周期中，系统都会经历基层下降的退化。（ii）系统经过一个周期充分生长后，非平衡反应转变为平衡反应，因此，无论是逆行还是渐进的陆架过渡冲积系统都不会降解，并且会继续恶化，但逐渐降低。（iii）冲积层顶河暂时但自发地在中间周期的下降沿达到渐变状态，这将较早的包括退化和较后的聚集可持续的周期分开。（iv）在此相变之前经过的周期数（或持续时间）与基本水平周期的幅度（或周期的平方）成线性比例，其系数由基本水平变化率定义和沉积物供应。考虑到长期的构造沉降或隆升，这种增长方式不一定成立。这些概念有助于理解通过基层周期演化的天然冲积层系统的地层结构。