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2013-09-26T13:25:18Z

Created page with "'''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 que..."

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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''':
{| class="Wikitable"
| 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

[[category:Standard zonation | 030]]

Belemnella lanceolata Zone s.l. - Revision history

Dbk: Created page with "'''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 que..."