The subsiding Vocontian Basin in SE France was an important depocenter during the late Early Cretaceous. The rims of this basin were occupied by large carbonate photozoan platforms, locally known as ‘’urgonian’’ platforms. During the late early Aptian, open marine heterozoan marls and carbonates accumulated on top of these former platforms, followed later by thick clayey sandy marls. In this succession, sediment accumulation was interrupted by several drowning phases which lead to hiatuses, encompassing up to several ammonite subzones. Such sedimentary successions are particularly well known in the Bas-Vivarais area of the Ardèche department (SE France). These sediments were mapped by the Bureau de Recherches Géologiques et Minières (BRGM) under various names whose definitions are imprecise and do not obey the rules of the stratigraphic nomenclature. Therefore, a compilation and revision of the available litho- and biostratigraphic data of the late early Aptian on the Languedoc platform is necessary to clarify the local stratigraphy. Here a new lithostratigraphic formation (the Chabert Formation) is proposed based both on lithological and sedimentologic criteria as well as ammonite biostratigraphy. In agreement with the nomenclature rules of lithostratigraphy, the type section and locality of the Chabert Formation are proposed for a section outcropping near the Chabert farm (SE Ardèche). This formation consists of heterozoan sediments (marls and crinoidal limestones) spanning the upper Deshayesites forbesi to the upper Dufrenoyia furcata ammonite Zones. The Chabert Formation is subdivided into three members - the Violette, Rocherenard, and Picourel Members, respectively. Above the Chabert Formation, black marls of late Aptian age (uppermost Dufrenoyia furcata Zone and above) are present, which we propose to name as Frayol Formation.