GEOLOGICAL HISTORY OF THE MORVAN
Morvan or Mor Ven in old Celtic language meaning Dark Mountain, is located in the northeastern part of the French Massif Central. Administratively, the Morvan region is distributed between the following four departments Yonne, Côte d'Or, Saône-et-Loire and Nièvre, all belonging to the Bourgogne (Burgundy) region. The Regional Park of the Morvan, created in 1970, covers 225 762 hectares in the highest and wooded hills.
Hight historical site, the Mont Beuvray and its vicinity are typical of the "morvandiaux" landscapes covered with forests and meadows.
The Trias and Lias argillaceous sediments (i.e. Bazois in the western part) surround the granitic mounts of the Morvan to which succeed the Lias and Jurassic limestone cuestas of Terre Plaine to the North and Auxois to the East. Southward the Charollais and the alluvial plain of the river Loire are the natural limits of the great Morvan.
Geologically the Morvan is mainly composed of Paleozoic formations, folded and granitized during the building of the hercynian mountain belt along the variscan orogeny, these mountains being eroded in the Carboniferous and Permian times. During Mesozoic and Cenozoic times large fracturation in relation to the pyrenean and alpine orogenies, is responsible of the formation of the Limagnes and Bresse grabens and Saint-Léon and Morvan horsts in the northeastern part of the Massif Central. Thus the Morvan presents a geologic unity and its study domain extends from the Haut Morvan mounts in the north, grading downward the southern Morvan low hills and then river Loire and Blanzy - Le Creusot coal field to the South.