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The Penninic nappes or the Penninicum are one of three nappe stacks and geological zones in which the Alps can be divided. In the western Alps the Penninic nappes are more obviously present than in the eastern Alps (in Austria), where they crop out as a narrow band. The name ''Penninic'' is derived from the Pennine Alps, an area in which rocks from the Penninic nappes are abundant. Of the three nappe stacks the Penninic nappes have the highest metamorphic grade. They contain high grade metamorphic rocks of different paleogeographic origins. They were deposited as sediments on the crust that existed between the European and Apulian plates before the Alps were formed. They are characteristically ophiolite sequences and deep marine sediments, metamorphosed to phyllites, schists and amphibolites. ==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 continental crust of the Valais Ocean, metamorphosed ophiolites and other sedimentary rocks from this disappeared oceanic 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 Briançonnais microcontinent. These are rocks from the lower continental crust deformed and intruded by Variscan granites, but also metamorphosed sedimentary rocks: graphite-bearing Carboniferous rocks, red sandstones from the Permian period, Triassic evaporites and thin limestones of the Jurassic and lower Cretaceous. Examples of Briançonnais terranes are the Sankt Bernard and Monte Rosa nappes; the Monte Rosa and the Mischabelhörner are formed by hard Briançonnais gneisses. *rocks from the former Piemont-Liguria Ocean, mainly ophiolites (fragments of the oceanic crust of this domain); limestone deposited in shallower parts of the Piemont-Liguria ocean and turned into marble and originally deep marine mudstones formed in the oceanic trench that existed at the northern edge of the 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「penninic」の詳細全文を読む スポンサード リンク
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