Fluidization: graded beds

Fluidization in a thick conglomerate to sandstone graded bed (Gosau Group of Muttekopf).

Fluidization in a thick conglomerate to sandstone graded bed (Gosau Group of Muttekopf). In the inner fluidized unit silt- and sandstone clasts float in a conglomerate matrix, pointing to inhomogeneous lithification prior to fluidization. The undisturbed parts of the beds at bottom and top show conjugate joints symmetric to bedding. Joint surfaces delimit the fluidized unit against the siltstone and must therefore predate fluidization. Probably bedding-parallel shortening caused rise of fluid pressures and hence fluidization.