Armorican Massif

The Armorican Massif is the remnant of a former located in north-western France mountain range. Geologically, including the Channel Islands to the Armorican massif, but politically they belong to the British Isles. So they are not considered here. The massif includes Brittany, western Normandy, west of the Pays de la Loire and the north-west of Poitou -Charentes. The name is derived from Armorica, a former between the Loire and the Seine estuary located Gallic populated area. It originated in the Paleozoic Variscan orogeny from the. In contrast to the Massif Central, the Armorican massif has hardly used the alpine unfolding. It was, however, raised during the development of the Bay of Biscay at the same time with the Cantabrian Mountains, the foothills ( épaulement ) it forms. Although the height of 400 m is rarely achieved (416 m at Mont des Avaloirs, Mayenne, Pays de la Loire and 413 m at the Signal d' Écouves, Orne, Normandy ), the solid due to the rocks and the steep landscapes must be assigned to the mountains.

Geography

The Armorican massif extends over an area of ​​approximately 65 000 km ² of

Brittany has two ridgelines on: the Monts d' Arree chain in the north, le Roc'h Ruz (385 m), le Menez Kador ( Signal de Toussaines ) ( 384 m) and le Roc'h Trevezel, in the east of the Monts du Mené ( Mont Bel-Air, 339 m), the Montagnes Noires in the south ( 326 m) les Landes de Lanvaux then the Sillon de Bretagne, as a continuation of les Montagnes Noires up to Nantes. The rivers have dug deep valleys: Alder, Odet, Blavet, Scorff, Laïta, Aven, etc.

In the department of Mayenne in the Pays de la Loire:

The Mont des Avaloirs, (highest point of the Armorican Massif 416 m), the chain of les Coëvrons.

In Sarthe:

The Alpes Mancelles in the east. The du mont skin Fourché reaches 217 m.

In Normandy:

• The signal d' Écouves, in the Orne reaches 413 m ( second highest point)
• The Mont Pinçon Calvados region with 365 m
• Located in the Orne Roche d' Oëtre, is one of the most picturesque landscapes in the Armorican Massif.
• Mortain with the highest waterfalls in North West France.

In Vendée and Deux -Sèvres:

• The heights of Vendée with 290 m on Mont Mercure and 269 m at the Puy Crapaud and, in Gâtine, 271 m at the Terrier de Saint -Martin- du- Fouilloux.

Geology

Geological areas

The Armorican massif was shaped by two orogenies, namely the Variscan orogeny and the Cadomian orogeny, so that the difference between the Cadomian range in the north and Variscan area can be made in the south. Even an older Icartien orogeny, which dates back to the Paleoproterozoic, was tracked in Jobourg in Normandy, and in Trégor in Brittany.

Nordamorikanischer area or Cadomischer area

The mountain ranges and cratons from the Icartien ( see above) and the sediments of the Pentévrien were strongly deformed, folded and exposed to a metamorphosis. It is due to the Cadomian and Variscan orogenies. The basement contains metamorphic rocks ( gneiss as ) from the Icartien and Pentévrien. But they are very rare for the digestion. Traces of it come in Trégor (next to Saint- Brieuc in Brittany, and are port - Beni, Trébeurden and Moulin -de- la -Rive ), in la Hague ( in Jobourg on the Cotentin Peninsula in Normandy ), but primarily in the Bailiwick Guernsey, in Guernsey, Sark and Alderney for the digestion. Icart Point in South Guernsey has given the Icartien his name.

The Cadomian range consists of scraps of former Cadomian mountain range. It is made of granite plutons ( Perros -Guirec, Bay of Saint -Brieuc, region Sartilly, Mayenne ) which date back to the Proterozoic. They are of Proterozoic sediments accompanied (South Cotentin, West Calvados, Northern Mayenne region around the river Rance ). These come from the Paleozoic sediments, which form a continuation of these deposits. They can be found in the center of Brittany Douarnenez to Angers Rennes. Or the sediments do not form a continuation, were easily folded Variscan orogeny during the. Variscan granite plutons of Carboniferous come to digestion ( region around Bourbriac, PLOEUC -sur- Lié and Dinan ). The whole thing was intersected by a verläufende from the Rade de Brest to the Sarthe Variscan fault.

The border in the south corresponds to the nordamorikanischen shear zone and imSüdteil the Cadomian area are Paleozoic deposits of Mittelarmorikanischen Synklinoriums ( ( syncline from Menez -Belair, from Vieux -Vy -sur- Couesnon and of Vitre all in the department of Ille -et -Vilaine in Brittany ) ).

Südarmorikanischer area or variszischer area

In südarmorikanischen area, the rocks consist mainly of Variscan granites. They are found along a fault that runs from the Pointe du Raz to the Loire. Sedimentary rocks from the Cambrian, Ordovician and Silurian ( Belle- Ile -en- Mer, western coast of Vendée, south of Angers Located region, and La Grande Brière ) they have been folded during the Variscan orogeny, or have become metamorphic, form the Paleozoic sedimentary rocks the region.

In Proterozoic volcanic and there is an active orogenic attributable to the Cadomian orogeny activity, and there is a mighty sediment accumulation ( Briovérien ).

These granites are due to the Variscan orogeny incipient before 330 million years and are the backbone of a mighty mountain range. The sandstones of the Ordovician and Silurian shale from the slide down into the synclines.

The shift to the north of the Iberian plate generates significant folds produced during the Silurian. She plunges below the Armorican plate. From subduction results in the Loire mountain range ( cordillera ligérienne ) and also a mountain range in the south of the Armorican Massif. The whole is then accompanied by weathered rocks ( molasses ) and granites from the Devonian the Carboniferous.

After the varizische orogeny took place, the massif of the erosion in the Mesozoic was suspended. In the Paleocene, there was an acceleration of erosion due to the subtropical climate. Thus, a peneplain has arisen. The Armorican Massif has hardly known to exploit the Pyrenean and Alpine orogenesis, and was not raised by it. Nevertheless, the effects of both orogenies are visible in the form of dislocations.

Structures

The difference can be made between:

• Domnonéen area: basement before the Cambrian orogenies has more experience ( the last is the Cadomian orogeny ) hardly busy during the Variscan orogeny;
• Mancellien or Le Mans area: basement before the Cambrian but younger ( Briovérien ) as flysch and Paleozoic rocks metamorphosed during the Cadomian orogeny and have been folded; to Variscan plutons;
• Mittearmorikanischer range: Paleozoic sedimentary rocks;
• Ligérien Loire region ( Pays de la Loire): metomorphisiert before the Cambrian basement rocks;
• Westvendée: from the Cambrian it has to do with the Massif Central.

The first two areas are part of the Cadomian range, the other three are part of the Variscan area. There is also the shear zone and the nordarmorikanische südarmorikanische shear zone.