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Conférence "Géologie du Massif Armoricain"

Tuesday 12 Feb
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Address 6 rue Jules Ferry Maison des Associations 56170 Quiberon
Conference December 12 given by Sylvain Blais, at 14:30, house associations. Geological history of the Armorican Massif The Armorican Massif includes the lands flush with the West of the Paris Basin and the North West of the Aquitaine basin. This is a puzzle where 3 large mountain ranges followed one another. 1 / The icartian chain (2 billion years ago): the oldest rocks of the Armorican Massif were defined in Icart Bay in Guernsey and found in Trégor and the Cherbourg region. 2 / The Cadomian chain (750 - 540 million years ago) structured the Trégor, the bay of Saint Brieuc, the regions of Saint Malo and Fougères. 3 / The Variscan (or Hercynian) chain is the result of the collision between two continents and has deformed the central and southern parts of the Armorican Massif. This story ends 300 million years ago. A very long period of erosion follows, pplancainant the existing reliefs About 20 million years ago, the Armorican Massif is invaded by a temperate to hot sea, very rich in fossils whose accumulations are known under the name of faluns. Regional history continues in the Quaternary, where cold periods (retreat of the sea) follow warm periods (marine transgressions). These marine variations are clearly visible in the landscapes of the Armorican Massif. Recent storms alter the morphology of the ribs. The Armorican Massif is a veritable open-air geological museum where history, begun 2 billion years ago, continues today.
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