Mineralbestand und Genese fränkischer Keuper- und Lias-Tone

The clay mineral composition of Keuper and Liassic clays and marls from Franconia (southern Germany) varies in a characteristic manner within the stratigraphic profile:

1. 1.
   Considerable amounts of montmorillonite are characteristic of the Upper Burgsandstein (higher part of Middle Keuper), and comparable amounts of illite-montmorillonite mixed-layers characterize the Feuerletten (top of Middle Keuper). In addition to these minerals, both units contain much illite and muscovite, some kaolinite and quartz, feldspars and carbonates. According to geologic investigations, both sediments are of terrestrial origin (semi-arid climatic conditions).