Generation of pavoni pipes in coarse-grained submarine mass wasting deposits as result of hydroplaning: stratigraphic occurrence and physical modelling

We present the results of physical modelling of the generation mechanisms of fluidization structures observed in coarse-grained deposits of a succession of Oligocene submarine turbidite systems. Such structures mainly appear as alignments of gravel sized particles, sub-vertically rotated with respect to the bedrock of the succession, embedded in sand-like pipes. We interpret these features as conduits of wet sediments expulsion similar to the "Pavoni pipes" observed in certain subaerial landslide deposits created by wet deposits compressed and pressurized by the settling landslide body. The best example of Pavoni pipes is found within the partly glacial Bonaduz gravel sediments in Switzerland, overloaded by the weight of the giant late-glacial Flims landslide. In analogy with the Bonaduz gravels, we suggest that the overburden pressure of a mass wasting body depositing onto unconsolidated sediments increased the load and started the escape pipes, now recognizable as the subvertical alignments. Calculations indicate that in submarine environment, a landslide body settling to the sea bottom after hydroplaning can increase basal pressure for a relatively long time, which promotes the creation of fluid escape pipes within its own body.