BGS Zone 1 (=UKB1 and 2 of Hart et al., 1989)
Base: The inception of Plectina mariae and Hagenowina anglica. Flourensina intermedia and Hagenowina advena become common. The extinction of the Albian taxa such as Arenobulimina chapmani and Arenobulimina sabulosa.
Top: The inception of the succeeding zonal index
- Vialovella praefrankei becomes extinct in the lower part of the N. carcitanense macrofaunal subzone.
- Facies related taxa such as Bulbophragmium aequale folkestonensis, which is found in the Glauconitic Marl of southeastern Kent, were used by Hart et al (1989) to define his UKB 1 Zone.
Macrofaunal correlation: M. mantelli Zone
Age: Early Cenomanian