Boulder clay

Boulder, also known as boulder clay, is the part of Grundmoränenmaterials, which emerged by superficial weathering of the calcareous glacial till. Boulder may already primarily caused by the deposition of calcium-free moraine beyond.

It consists mainly of sand and silt. The content of clay is subject to strong fluctuations. The glacial, mostly unstratified sediment may continue to be interspersed with rock fragments, blocks and other sediment components.

Formation

If the starting material of the glacial sediment had no lime, creating a lime-free sediment, which can not be described as marl due to lack of lime content, but otherwise has all the properties of the glacial till.

In the case of the glacial till of the originally present lime is gradually reduced by weathering (especially solution), in many cases until complete decalcification. The degree of decalcification increases from top to bottom, there may even be re- excretion of lime with Konkretionsbildung in deeper areas. Due to the onset after the ice age soil formation and rooting with, combined with good drainage but the upper floor area is usually completely free of lime. The color of the glacial till varies with the conversion to boulder from the previous gray to blue to yellow ocher to brown ( brunification ).