Armorican Massif

The highest summit, the Mont des Avaloirs (Mayenne département), is just 417 m (1,368 ft) above sea level.

During the Neoproterozoic, older parts of the Armorican Massif formed the northern margin of the paleocontinent Gondwana.

Armorica rifted off the northern margin of Gondwana somewhere during the Ordovician or Silurian periods to move northward and collide with Laurussia during the Hercynian orogeny.

The oldest rocks of the massif are Neoproterozoic sediments of the Brioverian Supergroup which were deformed and metamorphosed during the Cadomian orogeny.

Late Hercynian granitoid bodies were intruded along the South Armorican Shear Zone.

Location of the Armorican Massif on a structural map of the north of France. Hercynian massifs are olive coloured.
Geologic map of the Armorican Massif and surrounding areas.
The site of the " Roche d'Oëtre ".