Stable supercritical-flow bedform phases under two-dimensional steady flow are geometrically simple and include long-wavelength cyclic steps at high Froude numbers and antidunes characterized by in-phase flow that is near critical. Less well understood are the transitional bedform phases at the boundaries of the stable bedform fields and bedforms developing in complex flow geometries like the channel–lobe transition zone. This complexity is exacerbated by the fact that natural flows are never steady. Stable antidune bedforms may be reworked by temporally increasing discharge into chute and pool, and cyclic step and chute and pool fields will be reworked into antidunes if discharge is sufficiently decreasing. In addition, the channel–lobe transition zone is continuously evolving in space and time due to the influence of solitary hydraulic jumps at the channel mouth on channel extension and back stepping. This detailed outcrop study of a deep-water delta slope belonging to the Eocene Sant Llorenç del Munt clastic wedge exposed near El Pont de Vilomara (north-east Spain), tackles the complex bedform architecture problems by applying a method previously developed for fluvial deposits. Analysis of surfaces traced on high-definition, drone-derived in-strike images combines architectural studies with facies analysis. Set boundaries of the bedforms were thus established, revealing the upslope migration of hydraulic jump zones and the intricate stacking of antidunes and solitary, mouthbar related chute and pool like structures. Further analysis of the stacking of bedforms and bounding surfaces provide evidence that deposition occurred in a relatively short (few hundreds of metres) channel–lobe transition zone at the base of the delta slope. The usefulness of the bounding surface hierarchy approach for turbidite deposits lies in the careful evaluation of the spatial extent of bounding surfaces, which are easily overlooked in complex architectures such as those created in the channel–lobe transition zone.

中文翻译：

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在深水三角洲的通道-波瓣过渡带中由超临界流控制的床形动力学的重建（SantLlorençdel Munt，西班牙东北部，始新世）

二维稳定流下稳定的超临界流床状相在几何上很简单，包括高Froude数的长波长循环阶跃和以接近临界的同相流为特征的反沙丘。不太了解的是稳定床形场边界处的过渡床形相，以及在复杂的流动几何形状（如河道至波瓣过渡带）中发展的床形。自然流量永远不会稳定这一事实加剧了这种复杂性。稳定的反沙丘床形可以通过暂时增加向斜道和水池的排放量进行重新加工，如果排放量充分减少，则循环阶跃，斜道和水池场将被重新加工为反沙丘。此外，由于在通道口处单独的水力跃迁对通道延伸和后退步阶的影响，通道-波瓣过渡区在空间和时间上不断发展。这项详细的露头研究是针对深水三角洲斜坡的，该斜坡属于始露于El Pont de Vilomara（西班牙东北部）附近的始新世SantLlorençdel Munt碎屑楔，它采用了以前为河流沉积而开发的方法，解决了复杂的地层构造问题。在高清晰度，无人机派生的打击图像上跟踪的表面分析将建筑研究与相分析相结合。这样就建立了床形的边界，揭示了水力跃升区的上坡迁移以及反沙丘和单独的，与口杆有关的斜槽和水池状结构的错综复杂的堆积。对床形和边界面堆积的进一步分析提供了证据，表明沉积发生在三角洲斜坡底部相对较短（几百米）的通道-波瓣过渡带。浊水沉积物的边界面层次方法的用处在于仔细评估边界面的空间范围，在复杂的体系结构（例如在通道-波瓣过渡带中创建的体系结构）中，这一点很容易被忽略。