Mont Fier, Mountain summit in Prémanon, France

Mont Fier is a summit in the Jura massif reaching 1,282 m, located in the commune of Prémanon. It is a perched syncline: a limestone cliff of Upper Jurassic age forms a shallow bowl, framed by two side combes about 1 km wide and 150 m deep. The wooded ridge shows a pale rock face below the crest.

Mont Fier is the only known example in the Jura of a synclinal perché: its summit is a downfolded limestone basin left standing above the surrounding eroded anticline. The upper Jurassic limestone cliff forms a shallow syncline, while the two side combes, about 1 km wide and 150 m deep, are cut into upper Jurassic marls and marly limestones.

The mountain serves as a landmark for people exploring the Jura region and holds meaning for local walkers who navigate these paths regularly. It shapes how visitors understand the landscape around Prémanon.

Well-marked hiking trails lead to the summit, with route information available at the Prémanon tourist office. Bring sturdy footwear and a map, as mountain weather can change quickly in this region.

Mont Fier is the only known example in the Jura of a synclinal perché: its summit sits in a limestone basin of the Upper Jurassic, while the two side valleys around it are cut into softer marls. The anticline it belongs to, the Tressus-Les Arcets anticline, runs southwest as far as Saint-Claude.