Palaeoclimatic and palaeoenvironmental reconstruction of the Valanginian (~135 Ma, Lower Cretaceous) : towards a better understanding local versus global process

• Main Author: Charbonnier, Guillaume
• Other Authors: Interactions et dynamique des environnements de surface (IDES), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Paris Sud - Paris XI, Christophe Colin
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2013
• Subjects: Orbital forcing; Tectonic forcing; Palaeoclimatic belt; Terrigenous/nutrient influxes; Weissert Episode; Local vs global processes; Episode Weissert; Processus locaux versus globaux; Flux terrigène/de nutriments; Ceinture climatique; Forçage tectonique; Forçage orbital; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; North Atlantic
• Online Access: https://theses.hal.science/tel-00956584; https://theses.hal.science/tel-00956584/document; https://theses.hal.science/tel-00956584/file/VA2_CHARBONNIER_GUILLAUME_10122013.pdf

The Valanginian stage witnesses a positive carbon isotope excursion (amplitude 1.5-2‰) in the sedimentary records, the so-called « Weissert Episode ». This event coincides with major palaeoenvironmental and palaeoclimatic changes. The formation of the Paraná-Etendeka large igneous province has widely been proposed as the major driving force behind these changes. However recent investigations demonstrate that the Weissert Episode precedes the volcanic activity. Thus the driving force(s) behind these changes are still under debate. In the herein study, cyclostratigraphic, biostratigraphic, mineralogical and geochemical analyses have been performed on mid- and high latitudes sites (the Orpierre and Arnayon/La Charce sections in the Vocontian Basin, and the ODP hole 765C in the Argo abyssal plain) in order (i) to explore the dynamic of the local versus global processes in the palaeoenvironmental changes and (ii) to discuss the possible forcing factors behind the Weissert Episode. Local diagenetic and sedimentological processes that might bias the palaeoclimatic signals are highlighted and discussed before any palaeoenvironmental interpretation. The astronomical calibration of the Weissert Episode performed at Orpierre, allowed for the first time, the calculation of detrital and nutrient influxes into the Vocontian basin. They highlight rapid climate changes at mid latitudes, characterized by pronounced humid conditions during the Weissert Event (Early–Late Valanginian transition) and drier conditions in the Late Valanginian. In parallel, new geochemical and mineralogical analyses performed on the ODP hole 765C have been integrated to a global compilation of published geochemical and mineralogical data from 23 sections, located in five depositional environments. Three latitudinal belts have been recognized during the Valanginian : (i) an arid palaeolatitudinal belt in the Proto North Atlantic Ocean (~15–17°N), (ii) a subtropical climatic belt in the Northwestern Tethyan margin (~25–30°N) and (iii) a warm temperate ...