Calycoceras guerangeri Zone

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Base: The base of the zone is immediately below the first appearance of the index species (Gale, 1995).

Top: The top of the zone is immediately above the last occurrence of the index species (Gale, 1995).

Range of index species: The zone is coincident with the total range of the index species (Gale, 1995).

Key fauna:

Bivalvia: Amphidonte obliquatum (locally abundant)
Inoceramus pictus
Ammonoidea: Calycoceras guerangeri
C. spp.
Eucalycoceras pentagonum
Thomelites spp.
Echinoidea: Holaster spp. (thin-shelled, fragmentary species)


Faunal abundance & preservation: The zone is typically sparsely fossiliferous, and the fauna often fragmentary and poorly preserved.

Bio-markers: The middle of the zone contains a widely developed acme of the oyster Amphidonte obliquatum (Gale et al., 1999).

Age: Late Cenomanian.