Morainic arches

Two morainic arcs are present on Bessans, but the southernmost one is the most marked. It is underscored by large blocks deposited by the successive advances and retreats of the glacier. Their composition, from augen gneiss, containing feldspar crystals in the form of a horse tooth, testifies to their origin some kilometres higher up in the valley at the hamlet of Écot de Bonneval-sur-Arc.