Turrilites acutus Subzone
Base: The base of the subzone is immediately below the first appearance of the ammonite Turrilites acutus (Robaszynski et al., 1998), although previously it has been placed somewhat lower, at the top of the highest of three widely developed Cenomanian acmes of the brachiopod Orbirhynchia mantelliana (Bristow et al., 1995).
Top: The top of the subzone is immediately below the first appearance of the ammonite Acanthoceras jukesbrownei (Robaszynski et al., 1998)
Range of index species: The index species occurs in the lower half of the subzone only (Robaszynski et al., 1998).
Faunal abundance & preservation: The subzone is rather sparsely fossiliferous, except for locally common terebratulid brachiopods.Ammonites are rather poorly preserved as iron-stained chalky moulds.
Bio-markers: Inoceramus atlanticus is common in the higher part of the subzone.
Age: Mid Cenomanian