Critical revision and new proposals on the Aptian-Albian zonation of the Standard Mediterranean Ammonite Zonal Scheme

Difficulties of establishing a standard Mediterranean ammonite zonation of Aptian and Albian stages is a long-standing issue, which origination lies in paleobiogeographic reasons, debates on taxonomic problems and widespread presence of hiati, condensation and reworked levels, while poor record of ammonites is also connected to several biotic crises and periodic oxygen depletion. Hereby the maintenance of two-folded Aptian is supported with no zonal changes in the lower Aptian as keeping Deshayesites oglanlensis, D. forbesi, D. deshayesi and Dufrenoyia furcata Interval Zones. Regarding the upper Aptian zonation, the Parahoplites melchioris Zone is discussed, and several changes are proposed: the retention of 'Nolaniceras nolani' and 'Hypacanthoplites jacobi' Zones is supported, and to re-instate Diadochoceras nodosocostatum subzone as an Interval Zone is suggested. Introductions of 'Hypacanthoplites' elegans and Douvilleiceras leightonense Interval Zones are given, Douvilleiceras mammillatum Interval Zone is briefly discussed. Adoption of a zonation for the Mediterranean middle Albian based on hoplitid ammonites is impossible and must be abandoned, instead raising Lyelliceras lyelli subzone to Interval Zone rank, and discussion of Oxytropidoceras (Oxytropidoceras) roissyanum Interval Zone is given. For the upper Albian, Dipoloceras cristatum Interval Zone, and a zonation based on the succession of Pervinquieria spp. are discussed. Arrhaphoceras briacensis as an Assemblage Zone is discussed and supported. Geochronologic aspect of biozones is out of the scope of this paper.