High-resolution biostratigraphy and chemostratigraphy of the Cenomanian stratotype area (Le Mans, France)

Abstract : The definition of the Cenomanian stage was based on the description of several type 34 sections scattered in the vicinity of Le Mans (Sarthe, France). Despite limited exposures 35 nowadays, the area remains a reference for the palaeontology of the Cenomanian due to its 36 outstanding richness in marine macrofossils, especially molluscs, bryozoans, brachiopods and 37 echinoderms. The publication in 2015 of the volume dedicated to the Cenomanian stratotype 38 yielded the opportunity to restudy the last accessible outcrops. This paper provides a high39 resolution stratigraphic scheme and palaeoenvironmental reconstruction for the middle and 40 late Cenomanian interval in its type area. La Garenne Quarry is a window on the middle Cenomanian, where Praeglobotruncana rillella nov. sp. has been identified. The δ 13 41 Ccarb and δ 18 42 Ocarb record of a Cenomanian–Turonian succession close to Le Mans is correlated with the 43 type section of Pueblo (Colorado). Isotopic and biotic events highlight the presence of several 44 hiatuses in the sedimentary record of Le Mans especially around the Cenomanian–Turonian boundary with a dramatic truncation of the plateau of high δ 13 45 Ccarb values. Coiling reversal 46 events among the surface dwellers Muricohedbergella delrioensis, indicate sea surface 47 temperature changes with transient coolings, including the Plenus cold event, and warm 48 conditions at the Cenomanian–Turonian boundary. Sandy to chalky facies have yielded 49 empty, well-preserved shells of foraminifera allowing the description of Dicarinella 50 falsohelvetica nov. sp. Oxygen isotopic analyses performed on right- and left-coiled M. 51 delrioensis reveal a systematic offset during cold events which lead to discuss about the 52 potential occurrence of cryptic species in the Mesozoic.
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Delphine Desmares, Marc Testé, Bérengère Broche, Maxime Tremblin, Silvia Gardin, et al.. High-resolution biostratigraphy and chemostratigraphy of the Cenomanian stratotype area (Le Mans, France). Cretaceous Research, Elsevier, 2020, ⟨10.1016/j.cretres.2019.104198⟩. ⟨hal-02328773⟩

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