Humpback-dunes and Aggrading Standing Waves - Characteristic Features of Glacigenic Subaqueous Fans

DEDICATED: "GLACIATIONS" The formation and preservation of aggrading standing waves, antidunes and humpback dunes is commonly recognized to be rare in the geologic record. Field examples from glacigenic deltas and subaqueous fan settings indicate that these structures might be considered as a characteristic feature of these depositional systems. The objective of this study is to provide an analysis of depositional facies and geometries, which have rarely been studied from three-dimensional exposures and interpret them in terms of flow processes. The requirements for the formation of these relatively rare bedforms are met within plane-wall jets emerging from melt-water conduits. Hydraulic jumps occur when the initial supercritical flows evolve into subcritical flows and cause the formation of stationary standing waves immediately downstream. High sediment load and rapid flow deceleration establish highly aggradational conditions and allow for the deposition and preservation of deposits of aggrading standing waves and humpback dunes.