BGS Zone 4 (=UKB 5 of Hart et al., 1989)

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Base: The inception of Flourensina mariae and Plectina cenomana.

Top: The extinction of Praeglobotruncana delrioensis.

Biomarkers:

Rotalipora reicheli becomes extinct in the upper T. costatus macrofaunal subzone.

Hagenowina anglica, Spiroloculina papyracea and Favusella washitensis disappear from the record at the T. costatus / T. acutus macrofaunal subzonal boundary.

Subzones:

4i: un-named subzone between the base of the zone and the inception of Praeglobotruncana stepheni.

4ii: Praeglobotruncana stepheni Subzone: Base defined by the inception of the index species at the base of the A. rhotomagense macrofaunal zone (and T. costatus macrofaunal subzone). Top defined by the incoming of Rotalipora cushmani.

4iii: Rotalipora cushmani Subzone: Inception at the base of the T. acutus macrofaunal subzone. Rotalipora greenhornensis accompanies the subzonal index. Upper boundary is the top of the zone.

Macrofaunal correlation: C. inerme Zone, A. rhotomagense Zone & earliest A. jukesbrownei Zone.

Age: Early to Mid Cenomanian