Supercritical flows are ubiquitous in natural environments; however, there is rare 3D anatomy of their deposits. This study uses high-quality 3D seismic datasets from the world’s largest submarine fan, Bengal Fan, to interpret 3D architectures and flow processes of Pliocene undulating bedforms that were related to supercritical flows. Bengal undulating bedforms as documented in this study were developed in unconfined settings, and are seismically imaged as strike-elongated, crescentic bedforms in plan view and as rhythmically undulating, upstream migrating, erosive, discontinuous reflections in section view. Their lee sides are overall 3 to 4 times steeper (0.28° to 1.19° in slope) and 3 to 4 times shorter (117 to 419 m in length) than their stoss flanks and were ascribed to faster (high flow velocities of 2.70 to 3.98 m/s) supercritical flows (Froude numbers of 1.53 to 2.27). Their stoss sides, in contrast, are overall 3 to 4 times gentler (0.12° to 0.27° in slope) and 3 to 4 times longer (410 to 1139 m in length) than their lee flanks and were related to slower (low velocities of 2.35 to 3.05 m/s) subcritical flows (Froude numbers of 0.58 to 0.97). Bengal wave-like features were, thus, created by supercritical-to-subcritical flow transformations through internal hydraulic jumps (i.e., cyclic steps). They have crests that are positive relative to the surrounding region of the seafloor, suggesting the predominant deposition of draping sediments associated with net-depositional cyclic steps. Turbidity currents forming Bengal wave-like features were, thus, dominated by deposition, resulting in net-depositional cyclic steps. Sandy deposits associated with Bengal net-depositional cyclic steps are imaged themselves as closely spaced, strike-elongated high RMS-attribute patches, thereby showing closely spaced, long and linear, strike-elongated distribution patterns.

超临界流在自然环境中无处不在。但是，它们的沉积物很少有3D解剖结构。这项研究使用了来自世界上最大的海底扇Bengal Fan的高质量3D地震数据集，以解释与超临界流有关的上新世起伏地层的3D架构和流动过程。这项研究中记录的孟加拉起伏地貌是在无限制的环境中开发的，并且在平面图中被地震成像为走向伸长的新月形地貌，在剖面图中被成像为有节奏的起伏，上游迁移，侵蚀性，不连续反射。他们的背风面总体比陡壁高3至4倍（坡度为0.28°至1.19°），短3至4倍（长度为117至419 m），并且归因于速度更快（2.70至3的高流速） 。98 m / s）超临界流（弗劳德数为1.53至2.27）。相比之下，它们的前躯侧要比后腰轻3到4倍（坡度为0.12°到0.27°），长3到4倍（长410到1139 m），并与速度较慢（速度较低）有关。 2.35至3.05 m / s）的亚临界流（弗劳德数为0.58至0.97）。因此，通过内部水力跃迁（即循环步骤）的超临界至亚临界流动转换产生了孟加拉波状特征。它们的波峰相对于海底周围区域为正，表明与净沉积循环步骤相关的垂悬沉积物主要沉积。因此，形成孟加拉波状特征的浊流被沉积控制，从而导致净沉积循环步骤。