GSSP for the Paleogene - Neogene Boundary


Definition:

The Paleogene-Neogene System Boundary is defined in the Lemme-Carrosio Section (35m from the top of the section) in the village of Carrosio, south of the town of Gavi and north of Voltaggio (Allessandria Province), Italy.

Location:

The Lemme-Carrosio Section is located in the village of Carrosio. Longitude: 8°50’11” East; Latitude: 44°39’32” North. Carta Geologica d’Italia: Foglio Genova No. 82 (1:100 000); Tav. Voltaggio I NE (1:25 000).		click


Sedimentology:

The area of the Lemme-Carrosio Section is situated within the Piedmont Tertiary Basin, in southern Piedmont, Italy. In the Lemme Section, the Rigoroso Formation is characterized by poorly to very poorly sorted sediments which can be classified as fine and medium grained silts with fine silts dominating.		click


Sedimentological Markers:

An excellent lithological marker for the GSSP is provided by a distinct boundary between lithologic Unit A (the more massive part of the section) and the overlying lithologic UnitB-1 (the more stratified part of the section). At the 50m mark there is a horizon with yellowish nodules. The GSSP is exactly 15m above this lithologic boundary. A layer with yellowish nodules lies in lithologic Subunit B2, exactly one meter below meter 35.

Biostratigraphic Markers:

Calcareous Nannofossils:
Lowest occurrence of Sphenolithus ciperoensis is 21m below meter 35. Lowest occurrence of Sphenlithus delphix 12m below meter 35. Lowest and highest occurrence of Sphenolithus capricornutus within one meter above meter 35. Highest occurrence of Sphenolithus delphix 4m above meter 35.

Planktonic Foraminifera:
Lowest occurrence of Paragloborotalia kugleri two meters above meter 35. Highest occurrence of Paragloborotalia kugleri 25m above meter 35. Lowest occurrence of Globoquadrina dehiscens 12m above meter 35. Lowest occurrence of Globigerinoides altiaperturus 22m above meter 35.

Benthic Foraminifera:
Lowest occurrence of Uvigerina spinicostata one meter above meter 35.

Dinoflagellate Cysts:
Lowest occurrence of Ectosphaeropsis burdigalensis at meter 38. Highest abundance of Chiropteridium spp. at meter 39 and approximate highest occurrence of Chiropteridium spp one meter above meter 35. Bloom of Deflandrea spp. about 10m above meter 35 and highest abundance of Deflandrea at meter 15. Lowest occurrence of Distatodinium apenninicum at meter 10. Lowest occurrence of Membranilarnacia ?picena at meter 3 and lowest occurrence of Stoverocysta conerae at meter 1.

Magnetostratigraphy:

Biostratigraphic correlations allow the interpretation of the geomagnetic pattern of this section using the magnetobiochronologic scale of Berggren et al. (1995). Association of the distinct polarity reversals at meter 35 with biostratigraphic events cited above permit identifications of the magnetozones as Chron C6Cn.2r and Chron C6Cn.2n respectively. This unambiguous reversal pattern and the excellent biostratigraphic markers have been among the main reasons for defining the base of the Neogene at meter 35 of the Lemme-Carrosio section.

Other Locations around the World:

The GSSP is potentially correlatable worldwide by means of magnetostratigraphy, marine microfossil biostratigraphy, and/or stable isotope stratigraphy.

References:

Steiniger, F. F., Aubry, M. P., Berggren, W. A., Biolzi, M., Borsetti, A. M., Cartlidge, J. E., Cati, F., Corfield, R., Gelati, R., Iaccarino, S., Napoleone, C., Ottner, F., Roegl, F., Roetzel, R., Spezzaferri, S., Tateo, F., Villa, G., and Zevenboom, D., 1997. The Global Stratotype Section and Point (GSSP) for the Base of the Neogene. Episodes 20/1, p. 23 - 28.