HERCYNIAN OROGENIC BELT

also called Variscan Orogenic Belt, series of mountain ranges that developed during the Devonian Period (which occurred about 408 to 360 million years ago) and the subsequent Carboniferous Period (which ended about 286 million years ago), as a result of the collision between Africa and a North American-North European continent. The Hercynian extends in western Europe for more than 3,000 km (1,860 miles) from Portugal, Ireland, and England in the west through Spain, France (Brittany, Massif Central, Vosges, and Corsica), and Germany (Black Forest, Harz) to the Czech Republic in the Bohemian Massif. The belt contains many rocks and structures that indicate that its formation was a result of seafloor spreading, subduction of oceanic crust, and plate collision. It has a sinuous outcrop caused by collisional indentation of one block into another. Crustal thickening led to uplift, erosion, and extensional collapse of the central part of the belt in the Massif Central and Bohemian Massif and thus to formation of coal-bearing basins in the Carboniferous Period (360 to 286 million years ago). The southern part of the belt was extensively deformed by the collision tectonics that gave rise to the Alps and Pyrenees, and it was dismembered by the opening of the western Mediterranean basins and the Bay of Biscay.