Schrattenkalk Formation, Limestone formation in Swiss Alps, Switzerland

The Schrattenkalk Formation is a Barremian to Aptian limestone unit of the Helvetic Alps, named after the Schrattenfluh in Lucerne. It is divided into the Lower Schrattenkalk, the Rawil Member with sandstone and marl beds, and the Upper Schrattenkalk, all deposited on a shallow carbonate platform at the northern edge of the Tethys Ocean. Its thickness reaches up to 300 m in Switzerland and decreases eastwards to 60–100 m in the Allgäu and Bregenzerwald.

Bernhard Studer named this geological formation in 1834 after the Schrattenfluh area in Lucerne. This definition became an important point in the study of Alpine geology.

The name comes from combining German words meaning craggy rocks and chalk, reflecting regional geological terminology developed by Swiss scientists in the 1800s. This naming shows how scholars used the landscape around them to understand and classify natural features.

This formation is accessible at several locations, including rock faces and cave systems like Hoelloch. It helps to use guided tours or gather local information when exploring these areas.

In an abandoned quarry at Chilchsteinen on the south side of Pilatus, a fossil root soil was found, probably from mangrove-like vegetation. Together with the high detritus content of the Rawil Member, it shows that these beds were deposited near the shore.