Notions of fair-weather, storm, and swell wave bases are ubiquitous in interpretations of wave-dominated siliciclastic shelves, carbonate ramps, and mixed-systems deposits that are present throughout the geologic record. A review of literature, observations of several modern and ancient depositional systems, and numerical hydrodynamic models reveal the roles of sediment grade, bathymetric irregularities, and depositional gradient on the variable depths to which waves leave a sedimentologically discernible record. They reveal that wave-induced horizontal particle velocities and estimates of wave effectiveness form a continuous spectrum with depth, with a lack of distinct subdivision into fair-weather and storm conditions. Although commonly ascribed to “fair-weather wave base,” the depth above which sediment is persistently agitated or winnowed also is shaped by bathymetric gradient, direction of wave approach, tides, and currents, as well as sediment grade. Similarly, even with identical waves, the maximum depth of initiation of sediment movement, e.g., effective wave base, is not directly comparable among shelves, or even within the same shelf through time, because hydrodynamic processes are encoded differently by shelves of variable morphology and sedimentology.The numerical models further suggest possible geomorphology–hydrodynamics–sediment linkages. Relative to steeper shelves impacted by identical waves, shelves of shallower gradient favor lower-energy seafloor conditions, likely accompanied by accumulation of finer or muddier sediment, thinner sandy shoreface accumulations, or both. Given that many stratigraphic accumulations from the parasequence to composite-sequence scale steepen upward with time, this conceptual model predicts an apparent increase in wave energy on the seafloor through time for individual progradational shorelines, even with constant waves.

中文翻译：

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深不可测：浪底流沙

在解释整个地质记录中存在的以波浪为主的硅质碎屑架、碳酸盐斜坡和混合系统沉积物时，晴天、风暴和膨胀波底的概念无处不在。对文献的回顾、对几个现代和古代沉积系统的观察以及数值水动力模型揭示了沉积物品位、水深不规则性和沉积梯度对波浪留下沉积学可识别记录的可变深度的作用。他们揭示了波浪引起的水平粒子速度和波浪有效性的估计形成了一个具有深度的连续谱，缺乏对晴天和风暴条件的明确细分。虽然通常被认为是“晴天波基，” 沉积物持续搅动或风选的深度也受测深梯度、波浪接近方向、潮汐和洋流以及沉积物品位的影响。类似地，即使使用相同的波浪，沉积物运动的最大起始深度，例如有效波基，在不同的陆架之间，甚至在同一个陆架内也不能直接比较，因为水动力过程被不同形态的陆架编码，并且沉积学。数值模型进一步表明了可能的地貌-流体动力学-沉积物联系。相对于受相同波浪影响的更陡峭的大陆架，较浅梯度的大陆架有利于较低能量的海底条件，可能伴随着更细或更浑浊的沉积物的积累，更薄的沙质海岸堆积物，或两者兼而有之。