Acanthoceras jukesbrownei Zone

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Base: The base of the zone is immediately below the first appearance of the index species (Robaszynski et al., 1998).

Top: The top of the zone is immediately above the last occurrence of the index species (Robaszynski et al., 1998).

Range of index species: The zone is coincident with the total range of the index species (Robaszynski et al., 1998).

Key fauna:

Bivalvia: Inoceramus atlanticus
I. pictus
Pycnodonte vesiculare (locally abundant)
Ammonoidea: Acanthoceras jukesbrownei

Faunal abundance & preservation: Pycnodonte and Inoceramus are locally very abundant (see Bio-markers). Acanthoceras tends to be rather poorly preserved as iron-stained chalky moulds.

Bio-markers: Inoceramus atlanticus is abundant in the base of the jukesbrownei Zone (Gale, 1995). A marl in the lower part of the zone contains abundant Pycnodonte vesiculare, and represents the basal part of Jukes-Browne Bed 7. This marl marks the change from Inoceramus atlanticus below to Inoceramus pictus above, both species locally occurring in the marl.

Age: Mid Cenomanian