Paleohydrological and paleoenvironmental changes recorded in terrestrial sediments of the Paleocene-Eocene boundary (Normandy, France)

Sylvain Garel (1, 2, 3) , Johann Schnyder (2) , Jérémy Jacob (3) , Christian Dupuis (4) , Mohammed Boussafir (3) , Claude Le Milbeau (3) , Jean-Yves Storme (5) , Alina I. Iakovleva (6) , Johan Yans (7) , François Baudin (2) , Christine Fléhoc (1) , Florence Quesnel (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 iSTeP - Institut des Sciences de la Terre de Paris
3 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
4 GFA - Polytech Mons
5 FUNDP
6 Laboratory of Paleofloristics, Geological Institute
7 FUNDP - Fondation Universitaire Notre Dame de la Paix

The Paleocene-Eocene boundary (55.8 Ma) is associated with the Paleocene-Eocene Thermal Maximum (PETM), which is characterized by a negative Carbon Isotope Excursion (CIE), reflecting a major perturbation of the carbon cycle, and by an extreme and rapid global warming. The Cap d'Ailly area (Upper Normandy, France), in which previous studies have revealed the Paleocene-Eocene transition, is a reference locality for organic-rich terrestrial and lagoonal deposits of the "Sparnacian" stage, widespread in Northwestern Europe. In this study, we focus on the organic matter content of the Vasterival section. Organic data (Rock-Eval, palynofacies, biomarker analyses and compound specific isotope analyses) were acquired in order to constrain the paleoenvironmental and paleohydrological changes that occurred at the Paleocene-Eocene boundary. Stable carbon isotope compositions of higher plant leaf wax n-alkanes reveal a CIE of − 4.5 ‰, extending throughout the second half of the studied section. Palynofacies observations reveal: (i) an abrupt shift from a closed, quiescent marsh pond to an open eutrophic swamp subjected to algal blooms, concomitant with the onset of the CIE; and (ii) the evolution from a swamp to a tidal flat due to the marine transgression that occurred during the PETM. Higher plant biomarkers and their hydrogen isotopic composition compared to nitrogen analyses suggest: (i) dry episodes just before the PETM that may help to understand the triggering of this hyperthermal event; (ii) a moister climate associated with a stronger seasonality during the early PETM.

Mots clés: Paleoenvironments; Paleohydrology; Continental ecosystems; Hydrogen isotopes; Carbon isotopes; Dieppe-Hampshire Basin; PETM

Domaines: Interfaces continentales, environnement; Milieux et Changements globaux

Sylvain Garel, Johann Schnyder, Jérémy Jacob, Christian Dupuis, Mohammed Boussafir, et al.. Paleohydrological and paleoenvironmental changes recorded in terrestrial sediments of the Paleocene-Eocene boundary (Normandy, France). Palaeogeography, Palaeoclimatology, Palaeoecology, 2013, 376, pp.184-199. ⟨10.1016/j.palaeo.2013.02.035⟩. ⟨insu-00801796⟩