Cycles of humid-dry climate conditions around the P ⁄ E boundary: new stable isotope data from terrestrial organic matter in Vasterival section (NW France) Jean-Yves Storme, 1 Christian Dupuis, 2 Johann Schnyder, 3 Florence Quesnel, 4 Sylvain Garel, 3,4,5 Alina I. Iakovleva, 6 Paola Iacumin, 7 Antonietta Di Matteo, 7 Mathieu Sebilo 8 and Johan Yans 1 1 Department of Geology, FUNDP, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium; 2 UMons, Faculte ´ Polytechnique, GFA, rue de Houdain 9, 7000 Mons, Belgium; 3 Universite´ Paris 06, UMR 7072 ISTEP (UPMC-CNRS), 4, place Jussieu, 75252 Paris Cedex 05, France; 4 BRGM, GEO ⁄ G2R, BP 36009, 45060 Orle ´ans Cedex 2, France; 5 Institut des Sciences de la Terre dÕOrle ´ans (ISTO), Orle ´ans University, UMR 6113, 1A rue de la Fe ´rollerie, 45072 Orle ´ans, France; 6 Geological Institute RAS, Pizhevsky pereulok 7, 109017 Moscow, Russia; 7 Earth Sciences, Parma University, Viale G.P. Usberti 157 ⁄ A, 43100 Parma, Italy; 8 Universite´ Paris 06, UMR 7618 BIOEMCO (UPMC), 4, place Jussieu, 75252 Paris Cedex 05, France Introduction The Palaeocene–Eocene boundary (P ⁄ EB) (55.8 Ma; Aubry et al., 2007) is associated with an abrupt global climate warming probably caused by a catastrophic release of greenhouse gases (Kennett and Stott, 1991; Za- chos et al., 2003). The P ⁄ EB marks the beginning of the Palaeocene–Eo- cene Thermal Maximum (PETM), defined chemostratigraphically as the beginning of the onset of a 150–200 ka (Aubry et al., 2007; Westerhold et al., 2007) global carbon isotope excursion (CIE) recognized in both marine and terrestrial sections (e.g. Kennett and Stott, 1991; Koch et al., 1992; Sinha, 1997; Zachos et al., 2003; Magion- calda et al., 2004; Wing et al., 2005; Yans et al., 2006). The profound ocean acidification (Zachos et al., 2005) associated with this event has affected marine ecosystems with a massive extinction of benthic forami- nifera (Thomas, 1998). Terrestrial ecosystems were also strongly affected by important changes in plant com- munities (Wing et al., 2005; Smith et al., 2007) and shifts in taxonomic and trophic composition of terrestrial vertebrate faunas, resulting in the radiation and rapid migration of mod- ern mammals (Gingerich, 2003; Smith et al., 2006). An increasing number of PETM studies are dedicated to marine sections, whereas the terrestrial con- ditions remain poorly documented (Collinson et al., 2003; Pancost et al., 2007). Numerous Palaeocene–Eocene (P ⁄ E) outcrops are scattered along the Upper Normandy coast. Sections are well exposed, continuously eroded and located in a central position in the sub-basins of the southern North Sea Basin; therefore, they can be considered as reference sections for the NW European terrestrial-shallow marine P ⁄ E deposits (Magioncalda et al., 2001; Aubry et al., 2005). In this study, the position of the CIE is refined in a terrestrial key section of the Dieppe–Hampshire Basin, using a high-resolution sampling approach for carbon isotopes analyses of or- ganic matter (OM). The OM is char- acterized by Rock-Eval pyrolysis and palynofacies investigations. Nitrogen isotope results are also provided, for the first time for the P ⁄ EB, to refine our knowledge of the environmental and palaeoclimatic conditions around the P ⁄ EB. Geological and geographical setting The section of Vasterival is located along the Upper Normandy coast in France, 8 km west of Dieppe (Fig. 1). This section encompasses lignite com- plex (L1) of the Cap dÕAilly section (Fig. 2). In the Cap dÕAilly area, the Mont Bernon Group corresponds to the so-called Sparnacian (SP). The lower part of the Mont Bernon Group is the Mortemer Formation, which comprises from base to top: sands and sandstones (ÔSables et Gre`s du Pays de CauxÕ, SP1) followed by sandy lime- stones, pyritic marls and palaeosols, and a 1-m thick lignite complex (ÔCalcaire dÕAilly MemberÕ, SP2). This lignite complex (L1) exhibits a succes- sion of five multicentimetre-scale lignite beds (Lb1–Lb5) interstratified with OM bearing silts and clays beds (Fig. 3). The ÔSables et Argiles a` Ostracodes et MollusquesÕ (SAOM) of the Ailly Member (SP3) overlies uncomformably the lignite complex (Dupuis et al., 1998; Magioncalda et al., 2001; Aubry et al., 2005). ABSTRACT The Palaeocene ⁄ Eocene boundary (P ⁄ EB) and the Palaeocene– Eocene Thermal Maximum (55.8 Ma) are defined stratigraphi- cally based on carbon isotope ratios of various materials. Here, the position of the P ⁄ EB is refined in the terrestrial–lacustrine and swampy Vasterival section (Upper Normandy coast, France) by using carbon isotopes measured on dispersed organic matter (d 13 C org ). Moreover, nitrogen isotopes on dispersed organic matter (d 15 N org ) are, for the first time in the Palaeogene record, associated with carbon isotope and lithological data to constrain palaeoclimatic and environmental changes around the P ⁄ EB in a terrestrial environment. Humid-dry fluctuations before and during this key interval in Earth history are suggested. Terra Nova, 00, 1–9, 2012 Correspondence: Jean-Yves Storme, Department of Geology, FUNDP, Univer- sity of Namur, rue de Bruxelles 61, 5000 Namur, Belgium. Tel.: +32 81724469; fax: +32 81724471; e-mail: jean-yves.storme@ fundp.ac.be Ó 2012 Blackwell Publishing Ltd 1 doi: 10.1111/j.1365-3121.2011.01044.x