On the basis of the microfacies and correlations of the stratigraphic units of the Arbailles massif with those further to the north (Arancou-Bergouey, Orthez-Sainte Suzanne, France), more precise information is available on the upper Jurassic and lower Cretaceous stratigraphy of the area. Due to the absence of the Perisphinctus bed (Oxfordian) the Callovian-Oxfordian boundary is indefinitely drawn; the Kimmeridgian-Portlandian boundary is likewise imprecise. The Neocomian exists but is undifferentiated. The Aptian can be divided into upper (limestones) and lower (marls) units, a regionally recognizable subdivision. The Cretaceous is transgressive, but more concordant than discordant.