Backsteinkalk als Zeuge ordovizischer Vulkanausbrüche (Backsteinkalk as Witness of Ordovician Volcanic Ash Falls)

Within the Backsteinkalk geschiebes (glacial erratic boulders) of Northern Germany which originale from the Swedish mainland two types are distinguishable: the older group comparable with the Upper Dalby (below the Kinnekulle bentonite), and the younger group corresponding to the Skagen limestone (below the Grimstorp bentonite). The Backsteinkalk is a cherty limestone silicified by the overlying bentonites. The Kinnekulle bentonite produced also silicifications in the region of the Baltic Sea between the Swedish mainland and the Baltic mainland (Baltic Backsteinkalk = Sandö Flint), and also in the shale facies in Scania (Sularp Kieselschiefer). Younger Backsteinkalk like silicifications are known only from Central Sweden until now