title: A Cenozoic-style scenario for the end-Ordovician glaciation.
abstract: The end-Ordovician was an enigmatic interval in the Phanerozoic, known for massive glaciation potentially at elevated CO2 levels, biogeochemical cycle disruptions recorded as large isotope anomalies and a devastating extinction event. Ice-sheet volumes claimed to be twice those of the Last Glacial Maximum paradoxically coincided with oceans as warm as today. Here we argue that some of these remarkable claims arise from undersampling of incomplete geological sections that led to apparent temporal correlations within the relatively coarse resolution capability of Palaeozoic biochronostratigraphy. We examine exceptionally complete sedimentary records from two, low and high, palaeolatitude settings. Their correlation framework reveals a Cenozoic-style scenario including three main glacial cycles and higher-order phenomena. This necessitates revision of mechanisms for the end-Ordovician events, as the first extinction is tied to an early phase of melting, not to initial cooling, and the largest δ(13)C excursion occurs during final deglaciation, not at the glacial apex.
authors.affiliation: Institut de Physique du Globe de Strasbourg, UMR7516 CNRS/Université de Strasbourg, 1 rue Blessig, 67084 Strasbourg, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Ghienne
authors.affiliation: Department of Earth Sciences, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5.
authors.forename: André
authors.initials: A
authors.lastname: Desrochers
authors.affiliation: Géosystèmes, UMR8217 CNRS/Université Lille 1, Avenue Paul Langevin, bâtiment SN5, 59655 Villeneuve d'Ascq, France.
authors.forename: Thijs R A
authors.initials: TR
authors.lastname: Vandenbroucke
authors.affiliation: Institut National de la Recherche Scientifique, Centre Eau Terre Environnement, 490 rue de la Couronne, Quebec City, Quebec, Canada G1K 9A9.
authors.forename: Aicha
authors.initials: A
authors.lastname: Achab
authors.affiliation: Natural Resources Canada, Geological Survey of Canada, 490 rue de la Couronne, Quebec City, Quebec, Canada G1K 9A9.
authors.forename: Esther
authors.initials: E
authors.lastname: Asselin
authors.affiliation: Université de Rennes 1, Géosciences CNRS UMR 6118, Campus de Beaulieu, 35042 Rennes, France.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Dabard
authors.affiliation: Department of Earth Sciences, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5.
authors.forename: Claude
authors.initials: C
authors.lastname: Farley
authors.affiliation: Dipartimento di Scienze chimiche e geologiche, Università degli Studi di Cagliari, Scienze della Terra, Via Trentino, 51, 09127 Cagliari, Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Loi
authors.affiliation: Université de Rennes 1, Géosciences CNRS UMR 6118, Campus de Beaulieu, 35042 Rennes, France.
authors.forename: Florentin
authors.initials: F
authors.lastname: Paris
authors.affiliation: Department of Earth Sciences, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5.
authors.forename: Steven
authors.initials: S
authors.lastname: Wickson
authors.affiliation: Department of Earth Sciences, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5.
authors.forename: Jan
authors.initials: J
authors.lastname: Veizer