Figure F5. Biostratigraphic zonation used in this chapter for the Cretaceous follows Sissingh (1977) as modified and illustrated by Perch-Nielsen (1985). Datums for each boundary are listed with their age as determined by Erba et al. (1995) and Gradstein et al. (1995) (adapted from Whitmarsh, Beslier, Wallace, et al., 1998, p. 31).