title: Orbital pacing of carbon fluxes by a ∼9-My eccentricity cycle during the Mesozoic.
abstract: Eccentricity, obliquity, and precession are cyclic parameters of the Earth's orbit whose climatic implications have been widely demonstrated on recent and short time intervals. Amplitude modulations of these parameters on million-year time scales induce "grand orbital cycles," but the behavior and the paleoenvironmental consequences of these cycles remain debated for the Mesozoic owing to the chaotic diffusion of the solar system in the past. Here, we test for these cycles from the Jurassic to the Early Cretaceous by analyzing new stable isotope datasets reflecting fluctuations in the carbon cycle and seawater temperatures. Our results document a prominent cyclicity of ∼9 My in the carbon cycle paced by changes in the seasonal dynamics of hydrological processes and long-term sea level fluctuations. These paleoenvironmental changes are linked to a great eccentricity cycle consistent with astronomical solutions. The orbital forcing signal was mainly amplified by cumulative sequestration of organic matter in the boreal wetlands under greenhouse conditions. Finally, we show that the ∼9-My cycle faded during the Pliensbachian, which could either reflect major paleoenvironmental disturbances or a chaotic transition affecting this cycle.
authors.affiliation: Laboratoire des Fluides Complexes et Leurs Réservoirs, UMR 5150, CNRS, Total, Université de Pau et des pays de l'Adour, 64013 Pau, France; Center for Marine Environmental Sciences, Universität Bremen, 28359 Bremen, Germany;
authors.forename: Mathieu
authors.initials: M
authors.lastname: Martinez
authors.affiliation: Géosciences Environnement Toulouse, UMR 5563, CNRS, Institut de Recherche pour le Développement, Université Paul Sabatier, 31400 Toulouse, France guillaume.dera@get.obs-mip.fr.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Dera
keywords: Mesozoic; carbon cycle; eustatism; orbital cycles; paleoclimate