Albian Stage and Substage boundaries

Abstract

The base of the Albian Stage has been defined in the European province at the earliest appearance of the ammonite Leymeriella ('Proleymeriella') schrammeni anterior Brinkmann, the earliest member of the important 'mid-Cretaceous' ammonite superfamily Acanthocerataceae. A type section in the Harz fore­deep region of northern Germany has been proposed. A certain amount of intra-provincial variation in the ammonite fauna around this boundary is known in the European province. This does not provide insuperable difficulties, however, in the recognition of late Aptian and early Albian ages in the various lithological sequence􀀧 within this province. Leymeriella is generally unknown in the Canadian-Russian Arctic province, but the association of a Leymeriella of schrammeni Subzone age with a Freboldiceras in north Greenland, provides a useful correlation of these largely disparate provincial ammonite faunas. Correlation with the Gondwanan province is less certain at present. The length of Albian time (14-15.5 Ma) has led to the recommendation that Substage boundaries should be defined for the Middle and Upper Albian. The Subzone of Lyelliceras lyelli provides a good base for the Middle Albian, one that can be recognized in both the European and Gondwanan provinces. The base of the Upper Albian is marked by Dipoloceras cristatum an ammonite which is also of widespread occurrence in both of these provinces. The occurrence of the Arctic province ammonite Pseudogastroplites in the cristatum Subzone provides a good marker for correlation of this province with the European and Gondwanan provinces.