ABSTRACT Deep-marine levees are areally extensive features that border submarine channel systems and act to confine throughgoing sediment gravity flows. Compared to the adjacent channel, where episodes of erosion and bypass are commonplace, levees are mostly depositional features that experience little erosion, and therefore high preservation potential of individual beds, and as a consequence are generally assumed to provide a nearly continuous depositional record of sediment transport events down deep-marine slopes. Nevertheless, despite their size, volumetric prominence, and interpretive significance in the deep-marine sedimentary record, levees have received much less research attention compared to the adjacent channels. Exceptionally well exposed levee deposits in the Neoproterozoic Windermere Supergroup are dominated by thin-bedded, upper-division turbidites that form sharply bounded bedsets typically comprising 2–10 beds with similar grain size, bed thickness, Tc and Td/e division thickness, number of sets of ripple cross-lamination per bed, and ripple height, width, and spacing; additionally, the lithological and dimensional characteristics of the component beds in a bedset change at similar rates and spatial position along depositional strike. Such similarity suggests that deposition of each bed in a bedset is not associated with separate flow events (i.e., turbidity current), but instead represent systematic and recurring pulses or surges during a single flow event with similar hydraulic and textural conditions as they overspilled the channel margin and spread over the levee. Additionally, pulses were of sufficiently low frequency to allow the accumulation of a Td/e layer at the top of each bed and at least partial consolidation of the underlying bed. Finally, studies that have monitored and evaluated the frequency of turbidity currents in modern deep-marine systems suggest that there are a smaller number of beds, and even fewer bedsets preserved in ancient levee deposits than flow events. This suggests that many flows do not travel far enough downslope, or are of insufficient height, to result in any significant deposition on the levee. The bulk of levee strata, therefore, is likely deposited by anomalously large, pulsing flows that deposit multiple beds, but occur only once every several hundred to even several thousand years.

中文翻译：

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古代深海堤坝中薄层浊积岩的系统组织：浊流中节律性脉动的可能证据

摘要 深海堤岸是一种广泛的特征，与海底航道系统接壤，并起到限制通过的沉积物重力流的作用。与经常发生侵蚀和旁路的相邻河道相比，堤坝主要是几乎没有侵蚀作用的沉积特征，因此单个河床具有很高的保存潜力，因此通常被认为提供了几乎连续的沉积物沉积记录将事件运送到深海斜坡。然而，尽管堤坝在深海沉积记录中具有大小、体积突出和解释意义，但与相邻河道相比，堤坝受到的研究关注要少得多。新元古代温德米尔超群出露得天独厚的堤坝沉积物以薄层、上层浊积岩为主，形成边界清晰的层组，通常由 2-10 个层组成，具有相似的粒度、层厚度、Tc 和 Td/e 划分厚度、数量每床的波纹交叉层压组，以及波纹高度、宽度和间距；此外，一个床组中的组成床层的岩性和尺寸特征沿沉积走向以相似的速率和空间位置变化。这种相似性表明床组中每个床的沉积与单独的流动事件（即浊度电流）无关，而是代表系统性和反复出现的脉冲或浪涌，在具有类似水力和纹理条件的单次流动事件中，它们溢出河道边缘并蔓延到堤坝上。此外，脉冲的频率足够低，以允许在每个床的顶部积累 Td/e 层，并至少部分固结下面的床。最后，监测和评估现代深海系统中浊流频率的研究表明，与流动事件相比，古代堤坝沉积物中保存的床层数量较少，甚至更少。这表明许多水流没有向下坡行进足够远，或者高度不够，导致堤坝上有任何明显的沉积。因此，大部分堤坝地层可能是异常大的沉积物，