SHOCK-INDUCED RESUSPENSION DEPOSITS FROM A PLEISTOCENE PROGLACTAL LAKE (KLESZCZOW GRABEN, CENTRAL POLAND)

Several glaciolacustrine successions forming part of the Quaternary fi ll of the Kleszczow Graben contain massive and widespread fine-grained units that are abnormally thick and homogeneous. Field studies of suc h a unit indicate that it is the result of rapid settling of particles from a sediment cloud consisting of material that had once settled on the lake bottom but were resuspended. The geological setting makes it likely that the trigger mechanism responsible for the sediment cloud in the lake water was a shock and that this shock (most probably an ea rthquake) was caused by tectonic activity in the graben.