Upper-flow-regime bedforms, including upper-stage-plane beds, antidunes, chutes-and-pools and cyclic steps, are ubiquitous in glacigenic depositional environments characterized by abundant meltwater discharge and sediment supply. In this study, the depositional record of Froude near-critical and supercritical flows in glacigenic settings is reviewed, and similarities and differences between different depositional environments are discussed. Upper-flow-regime bedforms may occur in subglacial, subaerial and subaqueous environments, recording deposition by free-surface flows and submerged density flows. Although individual bedform types are generally not indicative of any specific depositional environment, some observed trends are similar to those documented in non-glacigenic settings. Important parameters for bedform evolution that differ between depositional environments include flow confinement, bed slope, aggradation rate and grain size. Cyclic-step deposits are more common in confined settings, like channels or incised valleys, or steep slopes of coarse-grained deltas. Antidune deposits prevail in unconfined settings and on more gentle slopes, like glacifluvial fans, sand-rich delta slopes or subaqueous (ice-contact) fans. At low aggradation rates, only the basal portions of bedforms are preserved, such as scour fills related to the hydraulic-jump zone of cyclic steps or antidune-wave breaking, which are common in glacifluvial systems and during glacial lake-outburst floods and (related) lake-level falls. Higher aggradation rates result in increased preservation potential, possibly leading to the preservation of complete bedforms. Such conditions are met in sediment-laden jökulhlaups and subaqueous proglacial environments characterized by expanding density flows. Coarser-grained sediment leads to steeper bedform profiles and highly scoured facies architectures, while finer-grained deposits display less steep bedform architectures. Such differences are in part related to stronger flows, faster settling of coarse clasts, and more rapid breaking of antidune waves or hydraulic-jump formation over hydraulically rough beds.

中文翻译：

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与冰川形成环境中的超临界流有关的地层和沉积结构

上流地区的地层，包括上层平面的地层，反沙丘，溜槽和水池以及循环阶跃，在以大量熔水排放和沉积物供应为特征的成冰沉积环境中普遍存在。在这项研究中，回顾了弗洛德近临界流和超临界流在成冰环境中的沉积记录，并讨论了不同沉积环境之间的异同。上流态床形可能出现在冰川以下，地下和水下环境中，记录自由表面流和淹没密度流的沉积。尽管单个床形通常不能指示任何特定的沉积环境，但是某些观察到的趋势与非成冰环境中记录的趋势相似。在沉积环境之间，床形演化的重要参数不同，包括流量限制，床坡度，凝集速率和晶粒尺寸。在密闭环境中，例如阶跃或切谷，或粗粒三角洲的陡坡，循环阶跃沉积更为常见。在无限制的环境和更平缓的斜坡上（例如，冰川河扇形，富沙三角洲的斜坡或水下（与冰接触）的扇形），通常会沉积有锑。在低凝结速率下，仅保留岩床的基础部分，例如与循环水力跳跃区或反沙浪破裂有关的冲刷填充，这在冰川河流系统和冰川湖爆发洪水中很常见，并且（ ）湖平面的瀑布。较高的凝结率会增加保藏潜力，可能导致保存完整的床单。这些条件在充满沉积物的jökulhlaups和以增大密度流为特征的水下水环境中得到满足。粗粒状沉积物导致陡峭的地层剖面和高度冲刷的相结构，而较细粒状的沉积物显示出较陡峭的地层结构。这种差异部分与流动力强，粗碎屑沉降更快，在水力粗糙床上的反沙丘波或水力跃变形成得更快有关。而较细颗粒的沉积物则显示出较不陡峭的岩床构造。这种差异部分与流动力强，粗碎屑沉降更快，在水力粗糙床上的反沙丘波或水力跃变形成得更快有关。而较细颗粒的沉积物则显示出不太陡峭的岩床构造。这种差异部分与流动力强，粗碎屑沉降更快，在水力粗糙床上的反沙丘波或水力跃变形成得更快有关。