Late Triassic (Norian to Rhaetian) foraminifers are recorded from the area of Cornettes de Bise, Préalpes Médianes plastiques, Préalpes du Chablais, Switzerland and France. They belong to Agathammina austroalpina Kristan-Tollmann & Tollmann, 1964, and Hoyenella inconstans (Michalik, Jendrejakova & Borza, 1979). This microfauna, typical of the Norian - Rhaetian alpine Neotethys, allows to confirm the age of the Dolomies blondes and Plan Falcon formations, which overlie the Carnian evaporites of the decollement surface of the Nappe des Préalpes Médianes plastiques.