Gonioteuthis Zone

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This zonal concept is only used in parts of East Anglia, where the standard zonal equivalents (= O. pilula & G. quadrata zones) cannot always be separately recognised. However, in the BGS Trunch Borehole [TG 2933 3455], Wood & Morter (1994) were able to tentatively infer the limits of the traditional O. pilula and G. quadrata zones.

Base: The base of the zone is placed at the top of the underlying M. testudinarius Zone (Peake & Hancock, 1970), presumably immediately above the highest occurrence of M. testudinarius. In Norfolk, there is no evidence of the U. anglicus Zone that usually immediately overlies the M. testudinarius Zone, and Wood & Morter (1994) suggested that there might be a non-sequence between the testudinarius and pilula zones in the Trunch Borehole.

Top: The top of the zone is immediately below the base of the Pre-Weybourne Chalk.

Range of index species: Peake & Hancock (1970) implied that Gonioteuthis 'belonging to the granulata-quadrata evolutionary series' occurred throughout the zone, but there is no precise range data, presumably because of poor exposures through this interval in East Anglia.

Key fauna:

Porifera: Retispinopora arbusculum
Bivalvia: Hypoxytoma tenuicostatum
Sphenoceramus (Inoceramus) lingua
Belemnoidea: Actinocamax versus
Belemnitella spp.
Gonioteuthis spp.
Asteroidea: Pycniaster magnificus
Stauranderaster senonensis
Crinoidea: Bourgueticrinus sp.
Echinoidea: Echinocorys tectiformis
E. spp.
Micraster schroederi
Offaster pilula

Faunal abundance & preservation: The zone is poorly fossiliferous.

Bio-markers: Locally the equivalent of the O. pilula or G. quadrata Zone of the standard zonal scheme can be recognised. The best example of this is a quarry at Wells [TF 928 429], where morphotypes of Echinocorys in the lower part of the succession possibly equate with the upper E. depressula Subzone, and are overlain by moderately common Offaster pilula and Echinocorys aff. cincta, suggesting assignment to the Subzone of abundant O. pilula (Peake & Hancock, 1970). A prominent marl in the Wells succession (Wells Marl) might equate with a marl (Old Nore Marl) in the middle of the O. pilula Zone in southern England (Wood & Morter, 1994). The first down-hole occurrence of Hypoxytoma tenuicostata in the Trunch Borehole was in the top of the O. pilula Zone, and this bivalve occurs in the lower part of the Sphenoceramus (Inoceramus) lingua Zone (below the Discoscaphites binodosus Subzone) in northern England (Whitham, 1993).

Age: Campanian.