The zone is 170 m thick, and ammonoids and other fossils occur as imprints in mudstones and as shell-rich layers in sandy turbidites.
The diversity of the ammonoid assemblage in this zone has increased to five genera and about 15 species.
Quite detailed correlations are not possible yet, but one can clearly see a westward diachronism in the first occurrence of some ammonoid genera.
Abundant concretions at several levels contain well-preserved ammonoids, bivalves and occasional fish.
Moreover, in the study of a highly diversified group such as the ammonoids, we believe that making too many generalizations can be risky.
This zone is widely distributed, 20-150 m thick, and contains the most diverse ammonoid assemblage with seven genera.
The number of ammonoid genera is greatly reduced to four, combined with a gradual shallowing-upward trend in the succession.
Brachiopods, cephalopods (ammonoids and one nautiloid) and bivalves are rare.
