Between those two orogenic events, the continental crust extended and a sedimentary basin formed.
This deposit was made of sedimentary rocks such as limestone, claystones and conglomerates.
Roc’h Ruz is the highest point in Bretagne and it is only 387 m above the sea level.
It is part of a network of low mountains called Mont d’Arrée located in the center of Bretagne.
In the western region of Bretagne, around Brest, metamorphic rocks and carboniferous granites dating from the variscan period are surfacing.
The south of Bretagne also has metamorphic and variscan granites showing up.
Nowadays, Bretagne is a mythical region of France, and 13 million tourists come every year from the entire the world to see its magical landscapes.
Geology Bretagne was shaped by two main geological events.
During the Cenozoïc (from 66 Mya until today) the erosion and alteration of granites, gneiss and schists produced sedimentary rocks such as sandstones or claystones.
These sediments are now concentrated in the Rennes basin in the west, and in the Chateaulin basin in the east.