Belemnella lanceolata Zone s.l.

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Base: In East Anglia, the base of the zone is the top of the Overstrand Pyramidata Hardground (Johansen & Surlyk, 1990). In Northern Ireland, the base of the zone is questionably inferred to be co-extensive with the base of the Tanderagee Chalk (Wilson & Manning, 1978).

Top: In East Anglia, the top of the zone is placed at an unspecified level within the Trimmingham Sponge Beds Member (Wood, 1967), and in Northern Ireland, at an un-named plane of separation in the lower part of the Ballycastle Chalk (= base of Bed C of Ballycastle Chalk sensu Fletcher, 1977).

Range of index: In Northern Ireland, the index ranges from the middle part of the nominate zone (Bed D of Port Calliagh Chalk sensu Fletcher, 1977) to the B. occidentalis Zone (Wood, 1967). Data about the range of the index in East Anglia are incomplete or ambiguous, but Belemnella first occurs a little above the base of the nominate zone (Wilson & Manning, 1978), at which level it already shows a relatively advanced morphology. The distribution of Belemnella in East Anglia is anomalous compared to elsewhere in Europe: it co-occurs with Belemnitella at the base of the nominate zone, is then briefly absent from the zone, before returning and eventually replacing Belemnitella (Christensen, 1996). This might be explained by two successive immigrations of Belemnella into the Norfolk area (Christensen, 1996).

Key fauna:

Porifera: Porosphaera globularis
Brachiopoda: Carneithyris sp.
Cretirhynchia arcuata
C. cf. limbata
C. magna
C. aff. retracta trans C. magna*
C. sp.
Orbirhynchia sp.
Bivalvia: Pycnodonte vesiculare
Belemnoidea: Belemnella lanceolata
B. gracilis*
Belemnitella ex gr. posterior
Belemnitella spp.
Crinoidea: Austinocrinus bicoronatus
Echinoidea: Echinocorys ex gr. belgica
E. cf. heberti*
Echinocorys pyramidata*

(*: occurs in zone in Northern Ireland)

Faunal abundance & preservation: The zone is richly fossiliferous, especially in East Anglia, but in Northern Ireland the hardness of the chalk makes fossil collection difficult.

Bio-markers: In both East Anglia and Northern Ireland, the association of Austinocrinus bicoronatus, Belemnella and Echinocorys ex gr. belgica (gigantic & thick-tested) is characteristic of the zone (Peake & Hancock, 1970; Wilson & Manning, 1978). In Northern Ireland, Belemnella is absent from a thicker interval of strata in the basal part of the zone, and Echinocorys pyramidata has a broader range, being mostly a feature of the top of the B. mucronata Zone in East Anglia (Wood, 1967; Peake & Hancock, 1970; Wilson & Manning, 1978). Belemnitella occurs in equal proportions with Belemnella in the higher part of the zone in Northern Ireland, but is completely replaced by Belemnella in the upper part of the zone in East Anglia (Wood, 1967). The lower part of the zone in East Anglia contains abundant Porosphaera globularis, and both here and in Northern Ireland huge specimens of Pycnodonte vesiculare are common (Wood, 1967; Peake & Hancock, 1970; Wilson & Manning, 1978).

Age: Early Maastrichtian