Comments and proposals about the Valanginian-Lower Hauterivian ammonite zonation of south-eastern France

A modified zonation for the Valanginian-Lower Hauterivian is proposed on th e basis of 9 reference sections in the Vocontian basin and compared with ot her zonations in the same area. The biostratigraphic subdivisions proposed here reflect the evolution of the ammonite faunas. The main modifications o f the zonal scheme concern the Upper Valanginian. The Neocomiensis horizon is abandoned. The former Trinodosum zone is replaced by the Peregrinus zone for its lower part and by the Furcillata zone for its upper part. The Call idiscus zone is retained only as horizon of the Furcillata zone. In the Low er Hauterivian, the Kiliani horizon (new) is proposed to replace the Bargem ensis horizon. The Radiatus zone is still maintained at the base of the Hau terivian. However, the main faunal caesura takes place at the base of the L oryi zone. This new scheme has the advantage of avoiding the introduction o f new biostratigraphical units.