Foraminiferal Marls are largely exposed in the «Chaines subalpines» (tectonically part of the Helvetic Autochtonous) of Savoy. These Foraminiferal Marls overlie either sandy limestones bearing large arenaceous Foraminifera, or, with a slight unconformity, Nummulitic Limestones of Priabonian age. The Foraminiferal Marls are evidencing a deepening of the sea which invaded the entire area during Priabonian times. From the base to the top, the Foraminiferal Marls show a deepening of the sea by the increase of the pelagic Foraminifera. By a progressive decrease of the Foraminifera and of the CaC0₃ content, and by an increase of the detritics of remote origin, the Foraminiferal Marls go into the overlaying «Meletta Shales». The paleontological study has shown that the Foraminiferal Marls are very likely of Sannoisian age.