Geological map of the Mauléon Basin and surrounding area (from Carte géologique de la France à 1/1 000 000, 6^e édition – 1996, BRGM Ed.). 1 to 4: selected stratigraphic sections in Fig. 3. Red doted line corresponds to Diagram D in Fig. 6. a: Quaternary alluvial deposits; q: Plio-Quaternary colluvium; m: Miocene; e: Eocene; c2: Upper Cretaceous; c1: Early Cretaceous; j: Jurassic; t: Triassic and ophites (22); r: Permian; h: Carboniferous; d: Devonian; b: Cambro-Ordovician.