The GSSP for the base of the Chattian Stage (Paleogene System, Oligocene Series) is defined at meter level 197 in the Monte Cagnero section, (Urbania, central Italy: 43°38'47.81"N – 12°28'03.83"E). This level coincides with the highest common occurrence of the planktonic foraminifer Chiloguembelina cubensis at the base of planktonic foraminiferal O5 Zone and falls in the upper part of calcareous nannofossil NP24 Zone, in the lower part of dinocyst Dbi Zone, and in the lower Chron C9n. Meter level 197 falls 30 cm below the base of a prominent, 40 cm–thick limestone bed in the middle of a recessive, 7 m–thick marly interval. This distinctive lithostratigraphic package is easily recognizable in the MCA section, and useful for recognizing the other lithostratigraphic intervals in this section, as well as in other coeval sections for regional correlation.
The Monte Cagnero section is located on the southeastern slope of Monte Cagnero (727 m above sea level; coordinates: 43°38'47.81"N – 12°28'03.83"E), a few kilometers to the SW of the town of Urbania (PU, Italy).
The Monte Cagnero section, which belongs to the pelagic succession of the Umbria–Marche basin. The GSSP lies in the Scaglia Cinerea Formation. The section consists of about 80 meters of hard grey limestone layers protruding out of recessive softer marls.
Highest common occurrence (HCO) of the planktonic foraminifer Chiloguembelina cubensis, at the O4/O5 planktonic foraminiferal zonal boundary of Wade et al. (2011).
The Highest Occurrence of the calcareous nanofossil Sphenolithus predistentus, which occurs 1 m below the primary marker.
Highest Common Occurrence of the calcareous nanofossil Sphenolithus distentus, marker of the base of NP25 Zone of Martini (1971), which is 4 meters above the primary marker.
The abundance interval of the Arctic cold–water Svalbardella cooksoniae dinocyst from meter levels 201 to 208, which is consistently found within Chron C9n.
The oxygen isotope excursion possibly related to the Oi2a glaciation event, which falls at meter level 193 in the middle part of Chron C9r.
The top of Chron C10n at meter level 190.2 and the base of Chron C9n at meter level 195.5, which would serve as correlation with marine and continental records.
Coccioni, R., Montanari, A., Bice, D.M., Brinkhuis, H., Deino, A., Frontalini, F., Lirer, F., Maiorano, P., Monechi, S., Pross, J., Rochette, P., Sagnotti, L., Sideri, M., Sprovieri, M.,Tateo, F., Touchard, Y., Van Simaeys, S., and Williams, G.L., 2017, The Global Stratotype Section and Point (GSSP) for the base of the Chattian Stage (Paleogene System, Oligocene Series) at Monte Cagnero, Italy. Episodes, 41 (1): 17-32.