BGS Zone 24 (=UKB20 of Hart et al., 1989)
Base: Inception of Bolivinoides peterssoni.
Top: Inception of Bolivinoides paleocenicus.
- Globotruncanella havanesis and Rugoglobigerina milamensis are consistently present for the first time from the base of the zone (although very rare specimens may occur immediately below it).
- A number of species appear for the first time at or immediately above the base: Bolivinoides decurrens, Bolivinoides australis, Gavelinella bembix, Osangularia navarroana and Neoflabellina reticulata.
- Pyramidina minuta has its inception in the highest B. mucronata macrofuanal zone (although it is very rare) and becomes more numerous in the early Maastrichtian.
- Eponides beisseli and Valvulineria lenticularis become extinct at the top of the zone.
24i: Concurrent range of Bolivinoides peterssoni and B. decoratus (in the Sidestrand Chalk Member). Hedbergella holmdelensis apparently becomes extinct at the top of the subzone.
24ii:. From the extinction of B. decoratus to the top of the zone (in the Sidestrand Chalk Member).
Macrofaunal correlation: Early B. lanceolata Zone s.l.
Age: Early Maastrichtian