BGS Zone 18 (=uppermost UKB14 and lower UKB15 of Hart et al., 1989)

Base: Inception of Gavelinella cristata.

Top: Inception of Bolivinoides culverensis.

Biomarkers:

• Stensioeina granulata polonica extinction at Peake’s Sponge Bed.

• Stensioeina exsculpta gracilis inception in the middle part of the foraminiferal zone, at the Echinocorys elevata Band and lateral equivalents at the base of the M. testudinarius macrofaunal zone.

Subzones:

18i. (un-named subzone). Inception of Gavelinella cristata and Gavelinella stelligera to the inception of Stensioeina granulata perfecta

18ii. Stensioeina granulata perfecta Subzone: marked by the inception of the index species in the ‘mid’ U. socialis macrofaunal zone.

18iii. Bolivinoides strigillatus Subzone: marked by the inception of the subzonal index in the upper U. socialis macrofaunal zone, a little below Hawks Brow Flint and lateral equivalents.

18iv. (un-named subzone). Inception of Rosita fornicata, Rugoglobigerina pilula, Archaeoglobigerina cretacea and Heterohelix striata at the base of the U. anglicus macrofaunal zone.

Macrofaunal correlation: topmost M. coranguinum Zone (immediately below Peake’s Sponge Bed and lateral equivalents), U. socialis Zone, M. testudinarius Zone & U. anglicus Zone.

Age: Late Santonian & Early Campanian