title: Mercury enrichment indicates volcanic triggering of Valanginian environmental change.
abstract: The Valanginian stage (Early Cretaceous) includes an episode of significant environmental changes, which are well defined by a positive δ13C excursion. This globally recorded excursion indicates important perturbations in the carbon cycle, which has tentatively been associated with a pulse in volcanic activity and the formation of the Paraná-Etendeka large igneous province (LIP). Uncertainties in existing age models preclude, however, its positive identification as a trigger of Valanginian environmental changes. Here we report that in Valanginian sediments recovered from a drill core in Wąwał (Polish Basin, Poland), and from outcrops in the Breggia Gorge (Lombardian Basin, southern Switzerland), and Orpierre and Angles (Vocontian Basin, SE France), intervals at or near the onset of the positive δ13C excursion are significantly enriched in mercury (Hg). The persistence of the Hg anomaly in Hg/TOC, Hg/phyllosilicate, and Hg/Fe ratios shows that organic-matter scavenging and/or adsorbtion onto clay minerals or hydrous iron oxides only played a limited role. Volcanic outgassing was most probably the primary source of the Hg enrichments, which demonstrate that an important magmatic pulse triggered the Valanginian environmental perturbations.
authors.affiliation: Institute of Earth Sciences, Géopolis, University of Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Charbonnier
authors.affiliation: Marine Palynology Group, Institute of Earth Sciences, University of Utrecht, Heidelberglaan 24, 3584 CS Utrecht, The Netherlands.
authors.forename: Chloé
authors.initials: C
authors.lastname: Morales
authors.affiliation: Laboratoire GEOPS, Bâtiment 504, Université Paris Sud, UMR 8148, Orsay F91405, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Duchamp-Alphonse
authors.affiliation: Cantonal agency for environmental protection, Rue des Creusets 5, CH-1950 Sion, Switzerland.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Westermann
authors.affiliation: Institute of Earth Sciences, Géopolis, University of Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Thierry
authors.initials: T
authors.lastname: Adatte
authors.affiliation: Institute of Earth Sciences, Géopolis, University of Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Karl B
authors.initials: KB
authors.lastname: Föllmi