A new lithostratigraphic scheme for the Schinznach Formation (upper part of the Muschelkalk Group of northern Switzerland)

The sediments of late Anisian and Ladinian age in northern Switzerland, which were formerly named Upper Muschelkalk and Lower Keuper, mostly consist of carbonates. They accumulated in a transitional area between central parts of the Central European Epicontinental Basin and its margin towards the Vindelician Swell. Oolitic intervals imply the former presence of shoals or ramps in this region. They characterise this transitional region (Alemannische Fazies) together with dolomites in the upper part of the sedimentary succession. The total thickness usually varies between 50 and 85 m. A general decrease in thickness towards southeast has been found. The newly named Schinznach Formation is defined as a mappable unit of the upper part of the Muschelkalk Group. It is precisely introduced for those sedimentary rocks formerly named Upper Muschelkalk and Lower Keuper in northern Switzerland between the Doubs River and the Lake Biel in the west and the Lake Constance in the east. Within this formation the informal lithostratigraphic subdivisions currently in use should be replaced by new terms in accordance with the rules of lithostratigraphic nomenclature. In the scheme presented here the Schinznach Formation comprises 5 members and 5 beds.