Original paper
High-resolution bio- and chemostratigraphy of an expanded record of Oceanic Anoxic Event 2 (Late Cenomanian–Early Turonian) at Clot Chevalier, near Barrême, SE France (Vocontian Basin)
Gale, Andrew S.; Jenkyns, Hugh C.; Tsikos, Harilaos; van Breugel, Yvonne; Sinninghe Damsté, Jaap S.; Bottini, Cinzia; Erba, Elisabetta; Russo, Fabio; Falzoni, Francesca; Petrizzo, Maria Rose; Dickson, Alexander J.; Wray, David S.
Newsletters on Stratigraphy Volume 52 Number 1 (2019), p. 97 - 129
published: Jan 15, 2019
published online: Sep 4, 2018
manuscript accepted: Jun 15, 2018
manuscript revision received: May 29, 2018
manuscript revision requested: Dec 20, 2017
manuscript received: Oct 28, 2017
ArtNo. ESP026005201004, Price: 29.00 €
Abstract
A newly located exposure of the Niveau Thomel, an organic-rich level at the Cenomanian–Turonian boundary, provides a highly expanded record of Oceanic Anoxic Event (OAE) 2, except for the lower relatively condensed glauconite-rich part of the section. The new locality, close to Barrême in the Vocontian Basin, SE France, is developed in deep-water hemi-pelagic facies (shales, marls, marly limestones, variably enriched in organic matter) and provides an improved understanding of palaeoceanographic events associated with OAE 2. Investigation of the biostratigraphy (nannofossils and planktonic foraminifera), organic and inorganic geochemistry (bulk carbonate δ18O, total organic carbon (TOC), bulk organic, biomarker-specific and carbonate δ13C, major and trace elements, and Rock-Eval data) has allowed characterization of the sediments in great detail. The combined study further constrains the detailed relationship between bio- and chemostratigraphy (particularly with respect to the details of the well-displayed positive carbon-isotope excursion) for this interval. The section also provides new evidence, in the form of a positive oxygen-isotope excursion and an offset between carbonate and organic-carbon carbon-isotope records, which confirms the importance of cooling accompanied by a drop in dissolved CO2 in near-surface waters during the Plenus Cold Event that characterized the early part of OAE 2. Evidence for increased oxygenation of bottom waters, together with elevated concentrations of redox-sensitive and chalcophilic elements registered elsewhere through the level of the Plenus Cold Event, may be reflected in enhanced concentrations of iron (in glauconite) and nickel in coeval strata from the Clot Chevalier section.
Keywords
Cenomanian–Turonian boundary • biostratigraphy • geochemistry • Vocontian Basin • Oceanic Anoxic Event 2