The formation is found in the northern canton of Aargau of Switzerland and has a thickness of 20 to 50 metres (66 to 164 ft), and in the Mont Terri area approximately 70 metres (230 ft). The Staffelegg Formation is named after the Staffelegg Pass, overlies the Keuper Group and is overlain by the Opalinus Clay. The formation comprises siltstones and marls. Additionally, limestones and subordinately also sandstones may occur especially in the Sinemurian part. In the Folded Jura, these sediments may make up the major portion of the Staffelegg Formation. Facies changes may occur within short distances in the Folded Jura. The Staffelegg Formation displays a small thickness compared to the occurrences of the Early Jurassic of southeastern France and southwestern Germany. A gradual decrease in thickness can be detected which continues from southwestern Germany into northern Switzerland.^[1]

Formerly, the formation was considered part of the Posidonia Shale, until it was defined as a separate formation by Reisdorf et al. in 2011.^[1][2]

The formation was deposited on the Northern Tethyan Carbonate Platform. The Staffelegg Formation dates from the late Hettangian to early Toarcian.^[1]

The Staffelegg Formation is subdivided into:^[1]

Among others, the following fossils have been reported from the formation:^[3]

Ichthyosaurs

• Eurhinosaurus longirostris^[4]
• Hauffiopteryx typicus^[5]
• Protoichthyosaurus cf. applebyi^[5]
• Stenopterygius sp.^[5]
• ?Temnodontosaurus sp.^[5]

Ammonites

• Catacoeloceras raquinianum^[4]