New data on the age of the installation of Urgonian-type carbonates along the northern Tethyan margin: biostratigraphy of the Chopf Member (Helvetic Alps, eastern Switzerland)

The Chopf Member is a glauconitic, phosphate-bearing succession that occurs in the distal part of the Helvetic Alps (eastern Switzerland). The recent discovery of age-diagnostic ammonites within this horizon allows for its attribution to the lower part of the Gerhardtia sartousiana zone (middle Late Barremian). This new age corresponds to a maximal age for the onset of the Schrattenkalk Fm. in this area, and is coeval with the onset of the Urgonian facies in other parts of the western Tethyan realm. This new age allows also for a more precise dating of Late Barremian δ13 C curves. To cite this article: S. Bodin et al., C. R. Geoscience 338 (2006). © 2006 Académie des sciences.