Penninic
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The Penninic nappes or the Penninicum, commonly abbreviated as Penninic, are one of three
Of the three nappe stacks the Penninic nappes have the highest
.Middle Penninic nappes include the Monte Rosa, Mont Fort, Siviez-Mischabel, Cimes Blanches and Frilihorn, of European origin. Upper Penninic nappes include the Zermatt-Saas and Tsaté, of oceanic origin and the Dent Blanche nappe (Austroalpine), of African origin.[1]
Subdivision in the Western Alps
Four paleogeographic domains can be recognized in the Penninic nappes of the Western Alps:
- rocks from the former European continental margin that were subducted and obducted again.
- rocks from the basin. The occurrence of eclogite lenses shows these rocks were subducted to great depths in the Earth's mantle. Valais sedimentary rocks include thin Cretaceous limestones (now marbles) and Tertiary flysch which is now turned into (mica-) schists.
- rocks from the former Mischabelhörner are formed by hard Briançonnais gneisses.
- rocks from the former Apulian plate. From the Cretaceous onward the oceanic crust of the Piemont-Liguria ocean subducted at these trenches beneath the Apulian plate.
The Piemont-Liguria Ocean and the Valais Ocean are, together with some other small oceanic basins, called Alpine Tethys Ocean or Western Tethys Ocean. The Tethys Ocean itself is sometimes considered to have begun east of the Apulian and African plates, but normally the Alpine Tethys is regarded as part of it.
Subdivision in the Eastern Alps
The following Penninic lithologies are found in the Hohe Tauern window, the Kőszeg Mountains and at the northern boundary of the Alps:
- old Precambrian and Cambrian gneisses of continental basement.
- various Paleozoic metamorphic rocks (ophiolites, schists)
- younger deformation in the Alpine orogeny).
- Triassic and Jurassic sedimentary rocks and ophiolites, turned into calcareous phyllites and green schists by metamorphism. Stratigraphically on top of these Cretaceous to early Tertiary flysch deposits are found sometimes.
It is not clear which of these units can be correlated with the Penninic units of the Western Alps. Some of them are clearly Penninic, some clearly Helvetic, and some are disputed.
The oceanic trench deposits of the Penninic nappes are found through the Alps and called
What is clear at least is that the Briançonnais terrane is not found in the Eastern Alps. The conclusion that can be drawn is that the microcontinent wedged out in the east in the Alpine Tethys Ocean. Some authors suggest the ophiolites that occur at the Hohe Tauern window must be correlated with the Piemont-Liguria terrane of the western Alps, because trench deposits such as radiolarites occur in both.
References
- ^ Marthaler, Michel; Rougier, Henri (2021). "An Outstanding Mountain: The Matterhorn, in Landscapes and Landforms of Switzerland, World Geomorphological Landscapes". ResearchGate. Springer Nature Switzerland AG 2021. Retrieved 15 January 2022.
- Description of the Western and Central Alps on the website of S.M. Schmid
- Description of the geology of Austria on the website of Christof Kuhn
- Hoeck, V; Koller, F (1999). "Mesozoic Metamorphic evolution of the Tauern Window" (PDF). Acta Montanistica Slovaca. 4 (2): 145–147.