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The Massif Central forms together with the Armorican Massif (Brittany and Normandy) one of the two big basement massifs in France. Its geological evolution started in the late Neoproterozoic and continues to this day. It has been shaped mainly by the Caledonian orogeny and the Variscan orogeny. The Alpine orogeny has also left its imprints, probably causing the important Cenozoic volcanism. The Massif Central has a very long geological history, underlined by zircon ages dating back into the Archaean 3000 million years ago. Structurally it consists mainly of stacked metamorphic basement nappes.〔Ledru, P., Lardeaux, J.M., Santallier, D., Autran, A., Quenardel, J-M., Floc'h, J-P., Lerouge, G., Maillet, N., Marchand, J. & Ploquin, A. (1989). Où sont les nappes dans le Massif Central français?, Bull. Soc. Géol. France 8, p.605-618.〕 == Introduction == The basement outcrops of the Massif Central have roughly the outline of a triangle standing on its tip. Because of its size – 500 kilometers long and 340 kilometers wide – the Massif Central partakes in several tectono-metamorphic zones formed during the Variscan orogeny. The bulk of the massif belongs to the Ligero-Arvernian Zone, sometimes also called the microcontinent Ligeria. With its northeastern tip, the Morvan, it reaches into the Morvano-Vosgian Zone which becomes the Moldanubian Zone farther east. All these zones constitute the interior core of the Variscan orogen in Europe which is characterized by the following traits: * It contains remnants of oceanic crust that were subducted during the Silurian and the Devonian. * The approach of Gondwana from the South onto the cadomian microcontinent Armorica (and farther east onto the Saxothuringian Mid-German Crystalline Rise) induced a continental collision slicing the basement into several large-scale nappes and thrusting them into southerly directions. * After the thrusting the orogen was exhumed diachronously. Exhumation started in the western and northern Massif Central already in the Upper Devonian (Frasnian) 380 million years ago whereas the southern part was elevated much later (in the Tournaisian, 350 MA BP). The Vosges farther east were raised even later – at the end of the Viséan at 330 MA BP. In the far south the Massif Central forms part of the Montagne Noire Zone. This zone constitutes together with the Pyrenees the microcontinent Aquitania; it is no longer made up of basement nappes, but contains low-grade Paleozoic sedimentary nappes having gravitationally slid off to the south from the rising Neoproterozoic basement. 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「Massif Central (geology)」の詳細全文を読む スポンサード リンク
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