Helvetic (geology)

In Switzerland the Helvetic zone is found in outcrops on the northern side of the Alpine mountain ranges.

The Mesozoic of this unit is contemporary with that of the Helvetic nappes, but deposited further north on the former continental slope and therefore shallower in sedimentary facies.

At places throughout the Alps the European basement was, after being detached of its cover rocks, tectonically uplifted in a late stage of the orogeny.

Thus the "external massives" were formed, places where the Hercynian basement rock crops out in large anticlinoria at the southern (or in France eastern) side of the Helvetic zone.

Seen from the north (or in France from the west) the hard competent crystalline rocks of these external massivs form the first of the higher ranges of the Alps.