Staffelegg Formation

Staffelegg Formation
Staffelegg Formation
Stratigraphic range: late Hettangian-early Toarcian; ~200–182 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Outcrop of the formation in the Schellen quarry
Type	Geological formation
Sub-units	See text
Underlies	Opalinus Clay
Overlies	Keuper Group
Thickness	20 to 50 m (66 to 164 ft)
Lithology
Primary	Siltstone, marl
Other	Limestone, sandstone
Location
Coordinates	47°24′N 8°36′E / 47.4°N 8.6°E
Approximate paleocoordinates	36°54′N 17°24′E / 36.9°N 17.4°E
Region	Canton of Aargau
Country	Switzerland
Extent	Folded Jura
Type section
Named for	Staffelegg Pass
Named by	Reisdorf et al.
Location	Staffelegg
Year defined	2011
	Staffelegg Formation (Switzerland)

The Staffelegg Formation (German: Staffelegg-Formation, French: Formation de la Staffelegg, Italian: Formazione della Staffelegg) is a formation of Early Jurassic age (late Hettangian to early Toarcian stages) in the Canton of Aargau of northern Switzerland. The siltstones, marls, limestones and intermittent sandstones of the formation were deposited on the Northern Tethyan Carbonate Platform (NTCP). The Staffelegg Formation has provided fossils of the ichthyosaur Eurhinosaurus longirostris and the ammonite Catacoeloceras raquinianum.

Description

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]

Subdivision

The Staffelegg Formation is subdivided into:^[1]

Gross Wolf Member
Rietheim Member
Rickenbach Member
Breitenmatt Member
Grünschholz Member
Frick Member
Fasiswald Member
Membre du Mont Terri
Weissenstein Member
Beggingen Member
Schambelen Member

Fossil content

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

Reptiles

Ichthyosaurs

Invertebrates

Ammonites

Catacoeloceras raquinianum^[4]

References

^ ^a ^b ^c ^d Staffelegg Formation at Strati.ch
^ Reisdorf et al., 2011a
^ Staffelegg Formation at Fossilworks.org
^ ^a ^b Reisdorf et al., 2011b
^ ^a ^b ^c ^d Klug, C.; Sivgin, T.; Miedema, F.; Scheffold, B.; Reisdorf, A.G.; Stössel, I.; Maxwell, E.E.; Scheyer, T.M. (2024). "Swiss ichthyosaurs: a review". Swiss Journal of Palaeontology. 143. 31. doi:10.1186/s13358-024-00327-4. PMC 11366730.

Bibliography

Reisdorf, A.; Wetzel, A.; Schlatter, Jordan (2011a), "The Staffelegg Formation: a new stratigraphic scheme for the Early Jurassic of northern Switzerland", Swiss Journal of Geoscience, 104: 97–146, doi:10.1007/s00015-011-0057-1
Reisdorf, A. G.; Maisch, M. W.; Wetzel, A. (2011b), "First record of the leptonectid ichthyosaur Eurhinosaurus longirostris from the Early Jurassic of Switzerland and its stratigraphic framework", Swiss Journal of Geoscience, 104 (2): 211–224, doi:10.1007/s00015-011-0069-x