Stratigraphic updating and correlation of Late Barremian–Early Aptian Urgonian successions and their marly cover, in their type region (Orgon-Apt, SE France)

Abstract

Comparing the stratigraphy of the rudist bearing limestones of Orgon (the type locality for the Urgonian stage of d'Orbigny) with that of the Urgonian limestones of the Monts de Vaucluse-Apt region, where the stratotype of the Aptian sensu d'Orbigny is located, shows that the corresponding platform carbonates have distinctive ages, late Barremian (Gehrartia sartousiana zone), and Bedoulian (Deshayesites oglanlensis to the middle part of the Deshayesites deshayesi zone) respectively. Nevertheless the Upper Barremian Orgon limestones are still present in the western part of the Monts de Vaucluse where they are capped by a Palorbitolina lenticularis–Heteraster oblongus (Pa1) guide level, ascribed to the Imerites giraudi zone. The overlying rudist beds are characterized by the presence of Caprinidae (Offneria-Pachytraga-Praecaprina assemblage), and spread over the Monts de Vaucluse-Apt region; they also extend to the Mont Ventoux, and to the eastern Languedoc too. These latter beds, assigned to the early Bedoulian, i.e. the D. oglanlensis–D. weissi zones, are interrupted by a drowning discontinuity capped by Palorbitolina beds (Pa2) overlain by bioclastic or coral limestones of early late Bedoulian age (lower part of the D. deshayesi zone). The succeeding marly cover, including marly limestones and the lowermost part of the “Gargas marls”, which marks the regional demise of shallow carbonates, is ascribed to the late Bedoulian (Deshayesites grandis subzone and Dufrenoyia furcata zone) and represents the lowermost part of the “Aptian”sensu d'Orbigny.