Original paper

Observations on the lithostratigraphy and ammonite succession across the Cenomanian-Turonian boundary in the environs of Le Mans (Sarthe, N.W. France)

Kennedy, W. J.; Juignet, P.

Abstract

Revision of the lithic and ammonite-inoceramid sequence across the Cenomanian-Turonian junction in the type area of the Cenomanian, the environs of Le Mans, shows that: 1. The Marnes à Ostrea biauriculata represent a horizon high in the classic Calycoceras naviculare Zone. 2. The Sables à Catopygus obtusus yield a Metoicoceras gourdoni Zone fauna. 3. The succeeding Craie à Terebratella carantonensis represents a previously unrecognised and un-named interval in the zonal sequence, above the gourdoni Zone, but below the appearance of Inoceramus labiatus sensu stricto. 4. Chalk with Inoceramus labiatus and Mammites nodosoides is present in the type area. Clarification of these relationships, together with faunal and historical arguments lead to the proposition of a return to the classic definition of the base of the Turonian stage on faunal grounds at the base of the Inoceramus labiatus/Mammites nodosoides Zone (DE GROSSOUVRE 1901).