Belemnella (Pachybelemnella) sumensis Zone

Base: The base of the zone is defined by the first appearance of the index species (Schulz, 1979).

Range of the index species: The range of the index species is co-extensive with the nominate zone (Schulz, 1979). In the Kronsmoor - Hemmoor sections, the index species is abundant, and also contains a restricted range of Belemnella (B?) cf. praearkhangelskii, the top of the range of Belemnella (B.) longissima (at the base), and sporadic occurrences of Belemnella (B.) gracilis (Schulz, 1979).

Biostratigraphical correlation: The exposed part of the zone, at the top of the Chalk Group in Norfolk, equates with the top of the B. lanceolata Zone and the exposed part of the B. occidentalis Zone of the standard macrofossil zonal scheme.

Lithostratigraphical correlation: The exposed part of the zone equates with the top of the Trimmingham Sponge Beds Member, the Little Marl Point and Beacon Hill Grey Chalk members (Johansen & Surlyk, 1990).