The origin of a giant downward directed clastic dyke in a kame (Bełchatów mine, central Poland)

A kame near Czubata Góra in the Pleistocene overburden of the Bełchatów open-cast browncoal mine in central Poland shows several types of deformations. A number of diapirs occur, but also a structure that shows all characteristics of a diapir but consists of sediments that apparently intruded the underlying rather than the overlying sediments. Analysis of this structure shows that it consists of material that was originally deposited as a fine-grained (mainly silty) glacilacustrine sediment. Seismic activity triggered the material to fluidise, resulting in a structureless mass. Part of the fluidised material flowed down into a fissure that had formed in the underlying sediments (probably due to tectonics in the active graben), thus forming a clastic dyke; more of the overlying silty material was later pressed down into a dyke with the shape of a downward directed diapir.