As banded , also Warventon or Warvit is referred to in the geology a fine grained sediment , due to the regular alternation of light and dark pitches looks banded in cross section. Band clays arise in ice reservoirs and lakes or pools on the edge of the ice and are therefore tied to cold climates. They are currently forming in glaciated areas. During the Pleistocene , however, they were also deposited in numerous places within the areas then covered by ice. They are therefore very widespread in northern Germany.
Band tones are caused by the seasonal fluctuations in the supply of water and sediment, with the lighter layers coming from summer (the time when the ice melts), when a lot of sediment settled. The dark layers were deposited in winter when little material was delivered, which was also rich in organic matter. A light and a dark layer together each form an annual layer ( warve ). Their thickness fluctuates within wide limits. It depends primarily on the material supply with the meltwater and is usually between 0.5 and 50 centimeters. However, both higher and lower values are possible.
In most of the band clay deposits, the counting of the individual annual locations enables the determination of the time it took to deposit them. By comparing characteristic locations and sequences of different occurrences, it is possible to set up a varven chronology that is valid for a larger area .
Due to their fine grain, many band clays or silts are suitable as raw materials for the ceramic industry, especially for heavy ceramics. But they are also used for the production of building materials such as bricks or expanded clay .
- Frank W. Junge: The band tones of Central Germany and adjacent areas . In: Natural History Museum Mauritianum Altenburg (Hrsg.): Altenburger scientific research . tape 7 , 1998, ISSN 0232-5381 , p. 210 .
- Dieter Richter: General Geology . 3. Edition. de Gruyter, Berlin - New York 1985, ISBN 3-11-010416-4 , pp. 47 .
- Potential of stone and earth raw materials in Thuringia. (PDF file; 20 kB)