Geological map of the Bielle area in the middle Ossau valley. A: Quaternary (alluvium); Gl: Quaternary (glacial tills); Br: undifferenciated Cretaceous (Lauriolle diapiric breccias); Al: Clansayesian (Uppermost Aptian)-Lower Albian (black spi²cule marls); n3: Clansayesian (Uppermost Aptian)-Lower Albian (Arudy limestones); n2: Aptian (rudist-bearing limestones); n1: Barremo-Bedoulian (limestones with annelids and Deshayesites-bearing marls); J: undifferenciated Jurassic (limestones, dolostones and marls); T: Middle-Upper Triassic (shales, cellular dolomites and ophite); Pm: Permo-Triassic (quartzite-bearing conglomerates); P: undifferenciated Palaeozoic (Cinq Monts formation).