BGS Zone 13 (=UKB11 of Hart et al., 1989)

Base: Inception of Verneuilina muensteri.

Top: Inception of Stensioeina granulata granulata

Biomarkers:

• Stensioeina granulata levis accompanies the first specimens of V. muensteri immediately above the Navigation Hardground through to the Hope Gap Hardground (basal M. cortestudinarium macrofaunal zone) in the Lewes Nodular Chalk Formation of southern England, but it is very rare.

• Gavelinella pertusa appears within the lower part of the zone, although the exact stratigraphical position of its inception is difficult to place due to its rarity in the earliest part of its range.

• In the very highest part of the foraminiferal zone (highest M. cortestudinarium macrofaunal zone) Globorotalites michelinianus generally disappears from the record in southern England (Lazarus Effect).

Gavelinella tourainensis becomes extinct at the top of the foraminiferal zone at the East Cliff/horeham Marl 2 (M. cortestudinarium/M. coranguinum macrofaunal zonal boundary).

Macrofaunal correlation: M. cortestudinarium Zone.

Age: Coniacian