Variscan orogeny In the Czech Republic and Eastern Poland the Bohemian Massif is the eastern end of the unmodified Variscan belt of crustal deformation in Europe. Further Variscan developments to the southeast are partly hidden and overprinted by the Alpine orogeny. In the Alps a Variscan core is built by Mercantour, Pelvoux, Belledonne, Montblanc and Aar Massif. Dinaric, Greek and Turkish mountain chains are the southeastern termination of the Variscan proper. The Variscan was contemporaneous with the Acadian and Alleghenian orogeny in the United States and Canada, responsible for forming the Ouachita and Appalachian Mountains. North American areas with Variscan foldbelts include
Svecofennian orogeny and thick continental crust collapsed under the influence of gravity and spread out. By 1850 millions years ago this collapse had evolved to a dynamic of extensional tectonics. In this extensional milieu short-lived sedimentary basins formed. The Svecobaltic orogeny developed when subduction bought the Fennoscandian Craton into an oblique collision with the Sarmatian Craton. The mentioned sedimentary basins were destroyed by basin inversion 1830 million years ago. This last event of basin inversion was associated with a period of metamorphism in southern Finland that peaked about 1820 million years ago. Two models exist regarding the origin of the Nordic orogeny: