Using well data the prequarternary subcrop and the base of glacial pleistocene is mapped. There are elevations of subcrop and channel systems at the base of pleistocene. Their configuration is rather independent of halokinetinally induced troughs and salinary structures of the subcrop. Channels in diverse directions were formed rather quickly by exaration, glacial tectonic and subglacial erosion. For many channels an Elster age can be proved.