The base of the Bathonian Stage is defined at the base of limestone bed RB071 in the Ravin du Bès Section, Bas-Auran area, southern Subalpine Chains, France. The boundary coincides with the first occurrence of the ammonites Gonolkites convergens and Morphoceras parvum.
The GSSP of the Bathonian Stage is located in the Bas-Auran area, southern Subalpine Chains, France, approximately 25 km SSE of Digne-les-Bains. The GSSP is located at a latitude of 43°57’38"N and a longitude of 6º18’55"E.
The GSSP succession is a cyclic marl-limestone alternation. In the Bas-Auran area, Lower Bathonian deposits comprise black or gray limestone beds alternating with marls. The Bajocian - Bathonian Boundary is defined at the base of limestone bed RB071. These deposits are relatively uniform mudstones to wackestones, with common ammonoids, scarce sponges and very scarce nautiloids, brachiopods, bivalves, belemnites, echinoids, crinoids and gastropods.
Ammonites: The boundary coincides with the first occurrrence of the ammonites Gonolkites convergens and Morphoceras parvum.
Nannofossils: The FO of Watznaueria barnesiae (NJT11) was observed in sample 68a of earliest Bathonian age (Zigzag Zone). This event defines the base of the Tethyan NJT11 Zone, comparable to most of the Boreal NJ11 Zone and NJ12a Subzone.
Ammonite FAD Gonolkites convergens (defines base of Zigzagiceras zigzag Zone)
An auxiliary section for the Bathonian Stage is located in Cabo Mondego, 40 km west of Coimbra, 7 km north of Figueira da Foz, Portugal (40°11'18"N, 8°54'30"W). It provides complementary data about the ammonite succession and biochronostratigraphic subdivision of the Sub- Mediterranean parvum Subzone and the Northwest European convergens Subzone.
Equal subzones scale Bajo-Bath-Callov
Fernández-López, S. R., Pavia, G. Erba, E., Guiomar, M., Henriques, M. H., Lanza, R., Mangold, C., Morton, N., Olivero, D., and Tiraboschi, D., 2009. The Global Boundary Stratotype Section and Point (GSSP) for base of the Bathonian Stage (Middle Jurassic), Ravin du Bès Section, SE France. Episodes 32/4, p. 222 - 248.