The Ordovician of the Armorican Massif extends from the Lower Ordovician. (Arenig -Llanvirn - Llandeilo) to the upper Ordovician. (Caradoc - Ashgill).

It stretches from West to East, almost continuously, from the Crozon Peninsula (Morgat ...) to the center of Brittany (Gourin ...), Mayenne (Andouillé ...) and the western part of the Sarthe (Butte du Creux ...) => Median synclinarium from north to south extends from Normandy (Cotentin peninsula, south of Caen) to the region of Bain de Bretagne, Laillé ( Martigny Ferchaud synclinarium) to Angers, Ancenis, North of Vendée.

Note the extreme convergence with the Black Mountain (Saint Chinian region), Czechoslovakia and Morocco, but especially with the Iberian peninsula (Spain, Portugal).

It would be interesting to make a comparative study between these different regions.

Overview of some armorican specimens :