The Ternoise valley is the most northerly flowing in the syncline to the south of the Variscan front.
For much of its history the Weald had been slowly subsiding basin, but the growth of the Alpine Chain to the south during the Cenozoic caused a reactivation of the Variscan basement basin-bounding faults, the rocks were arched into a broad anticline which stretched across the English Channel to Northern France, the Weald–Artois anticline.
Just to the south of La Châtre, some twelve kilometres south of Vic, the Variscan-faulted rocks of the Massif Central begin with Cambrian/Ordovician migmatite.