Staffelegg Formation

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.

Staffelegg Formation
Stratigraphic range: late Hettangian-early Toarcian
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Outcrop of the formation in the Schellen quarry
TypeGeological formation
Sub-unitsSee text
UnderliesOpalinus Clay
OverliesKeuper Group
Thickness20 to 50 m (66 to 164 ft)
Lithology
PrimarySiltstone, marl
OtherLimestone, sandstone
Location
Coordinates47.4°N 8.6°E / 47.4; 8.6
Approximate paleocoordinates36.9°N 17.4°E / 36.9; 17.4
RegionCanton of Aargau
Country  Switzerland
ExtentFolded Jura
Type section
Named forStaffelegg Pass
Named byReisdorf et al.
LocationStaffelegg
Year defined2011
Staffelegg Formation is located in Switzerland
Staffelegg Formation
Staffelegg Formation (Switzerland)

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

References

  1. Staffelegg Formation at Strati.ch
  2. Reisdorf et al., 2011a
  3. Staffelegg Formation at Fossilworks.org
  4. Reisdorf et al., 2011b

Bibliography

Further reading

  • Kiefer, L.; G. Deplazes, and H. R. Bläsi. 2015. Sedimentologie und Stratigraphie des Frühen Juras in der Nordschweiz: Staffelegg-Formation und sich nach Osten anschliessende Vorkommen, nagra Arbeitsbericht, 14–95. NAB.
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