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The volcano-sedimentary evolution of a post-Variscan intramontane basin in the Swiss Alps (Glarus Verrucano) as revealed by zircon U-Pb age dating and Hf isotope geochemistry

Letsch, Dominik ; Winkler, Wilfried ; von Quadt, Albrecht ; Gallhofer, Daniela

In: International Journal of Earth Sciences, 2015, vol. 104, no. 1, p. 123-145

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    Titre
    • The volcano-sedimentary evolution of a post-Variscan intramontane basin in the Swiss Alps (Glarus Verrucano) as revealed by zircon U-Pb age dating and Hf isotope geochemistry
    Auteur
    • Letsch, Dominik. Department of Earth Sciences, Geological Institute, ETH Zentrum, Sonneggstrasse 5, 8092, Zurich, Switzerland
    • Winkler, Wilfried. Department of Earth Sciences, Geological Institute, ETH Zentrum, Sonneggstrasse 5, 8092, Zurich, Switzerland
    • von Quadt, Albrecht. Department of Earth Sciences, Geological Institute, ETH Zentrum, Sonneggstrasse 5, 8092, Zurich, Switzerland
    • Gallhofer, Daniela. Department of Earth Sciences, Institute of Geochemistry and Petrology, ETH Zentrum, Clausiusstrasse 25, 8092, Zurich, Switzerland
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • International Journal of Earth Sciences, 2015, vol. 104, no. 1, p. 123-145. Springer Berlin Heidelberg
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:332026
    Summary
    The Late Palaeozoic Glarus Verrucano basin (GVB, Glarus Alps, eastern Switzerland) formed as an intramontane graben in the aftermath of the Variscan orogeny. Its fill, the Glarus Verrucano, consists of immature alluvial fan and playa lake deposits with intercalated bimodal volcanics (basalts and rhyolites). Despite its importance for local and regional geology, no modern sedimentologic or stratigraphic studies on the GVB exist. By means of sedimentologic and geochronologic studies, we reconstruct the volcano-sedimentary evolution of the GVB: it developed at the Carboniferous/Permian boundary and experienced a first (bimodal) volcanic phase around 285Ma. For the same time, indications for temporarily humid climate in the otherwise rather arid Early Permian are demonstrated (e.g. pyrite-bearing sandstones). During the Middle and Early Late Permian, increasing aridity is indicated by playa deposits, fanglomerates and subaerial ignimbrites, which mark a second (silicic) volcanic phase at 268Ma. The detrital zircon age spectra are dominated by Late Variscan ages and thus demonstrate that older sedimentary and metamorphic rocks once forming the Variscan nappe edifice were already mostly eroded at that time. Finally, some larger-scale speculations are given which could indicate a causal connection between the widespread tectono-magmatic Mid-Permian Episode and the local development of the Glarus Verrucano basin.