SBZ 20 (late Priabonian)
Defined by the biostratigraphic range of: Nummulites retiatus, N. garnieri inaequalis, Heterostegina gracilis and Discocyclina trabayensis vicenzensis. Lower boundary imprecise, located within NP19-20 according to Mathelin and Sztrakos . The upper boundary coincides with the Eocene-Oligocene boundary which coincides with the base of SB21 according to Cahuzac and Poignant .
SBZ 19 (early Priabonian)
Defined by the biostratigraphic range of: Nummulites fabianii, N. garnieri garnieri, N. cunialensis, Discocyclina pratti minor and Asterocyclina alticostata danubica. The lower boundary coincides with the Middle/Upper Eocene boundary, located in the lower part of Chron 17.1 n, within P15 and to the lower part of NPI8, according to Berggren et al. .
SBZ 18 (late Bartonian)
Defined by the biostratigraphic rarige of: Nummulites biedai, N. cyrenaicus, N. vicaryi and N. boulangeri. The lower boundary imprecise, located within Chron 17.3r according to Serra-Kiel and Trave . SBZ18 corresponds to the early part of P15 and the late part of NPI7, and to the lower part of NPI8, according to data in Canudo et al. and Bombita .
SBZ 17 (early Bartonian)
Defined by the biostratigraphic range of: Alveolina elongata,A. fragilis, A. fusiformis, Nummulites brongniarti, N.perforatus, N. hottingeri, N. puschi, N. biarritzensis, N. lyelli and Discocyclina pulcra baconica. The lower boundary is located close to the base of Chron 19n according to Burbank et al. . SBZ17 starts in the upper part of P12 and extends over P13 and P14 according to Canudo et al.  and Serra-Kiel and Trave . It rides the NP16/NP17 boundary [Bombita, 1984].