Le prélude au Quaternaire : les modalités d'entrée en glaciation (65 Ma ‑ 2,2 Ma)

• Published in: Quaternaire
• Main Author: van Vliet‑Lanoë, Brigitte
• Format: Article in Journal/Newspaper
• Language: French
• Published: Association française pour l’étude du quaternaire 2009
• Subjects: Cénozoïque; circulation thermohaline; glaciation; tectonique; aridité; Cainozoic; conveyor belt; glacierization; tectonics; aridity; geo; hist; Antarctic; The Antarctic; Antarc*
• Online Access: https://doi.org/10.4000/quaternaire.1006; http://journals.openedition.org/quaternaire/1006

The Cainozoic era records a step-like glacierization, first on the southern hemisphere and since the onset of Neogene on the northern hemisphere. This evolution is linked to the rifting and to plate tectonic that opened or closed several straits. Since the Cretaceous, the creation of collisional or isostatic deloading reliefs thanks to underplating or superficial erosion favoured the glacierization. Sea floor spreading and ice storage induced an important sea-level drop. Modifications of the marine and atmospheric circulations induced by the new-born reliefs intensified the cooling trend. The Earth shifted from an unipolar glaciation to a bipolar one from the Neogene, from a zonal oceanic circulation to the present thermohaline circulation throughout CO2 consumption. From 3 Ma, in relation with the land masses and oceans configuration, the glacierization is global with a strong control by insolation strength, and an equatorial positioning of the Intertropical convergence zone (ITCZ). The increasing aridity influenced the biodiversity and dust production at least since the Oligocene. At the onset of the Pleistocene, the glacierization is mostly completed : the Antarctic ice maximum occurred during the Miocene, although true ice sheets only developed from the Pliocene in the northern hemisphere. Le Cénozoïque enregistre une englaciation croissante par étapes, d’abord dans l’hémisphère sud puis, depuis le début du Néogène, dans l’hémisphère nord. Cette évolution est en relation surtout avec le rifting et la tectonique des plaques qui ouvrent ou ferment des détroits. La création de reliefs de collision ou de reliefs de décharge isostatique par érosion crustale ou superficielle, après le Crétacé, favorise l’englaciation. L’extension du plancher océanique et le stockage croissant de glace amènent une baisse eustatique importante. Les modifications des circulations océaniques et atmosphériques, que les reliefs entraînent, accentuent le refroidissement par le biais de la consommation du CO2 atmosphérique. La Terre ...