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Stratigraphic, sedimentological and palaeoenvironmental constraints on the rise of the Urgonian platform in the western Swiss Jura

Authors

  • ALEXIS GODET,

    1. Institut de Géologie, Université de Neuchâtel, rue Emile Argand 11, CP 158, 2009 Neuchâtel, Switzerland
    2. Neftex Petroleum Consultants Ltd, 97 Milton Park, Abingdon, Oxfordshire OX14 4RY, UK
    3. Institut de Géologie et Paléontologie, Université de Lausanne, Anthropôle, 1015 Lausanne, Switzerland (E-mail: Alexis.Godet@unil.ch)
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  • KARL B. FÖLLMI,

    1. Institut de Géologie, Université de Neuchâtel, rue Emile Argand 11, CP 158, 2009 Neuchâtel, Switzerland
    2. Institut de Géologie et Paléontologie, Université de Lausanne, Anthropôle, 1015 Lausanne, Switzerland (E-mail: Alexis.Godet@unil.ch)
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  • STÉPHANE BODIN,

    1. Institut de Géologie, Université de Neuchâtel, rue Emile Argand 11, CP 158, 2009 Neuchâtel, Switzerland
    2. North Africa Research Group, School of Earth, Atmospheric and Environmental Science, University of Manchester, Williamson Building, Oxford Road, Manchester M13 9PL, UK
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  • ERIC De KAENEL,

    1. DeKaenel Paleo-Research, 2000 Neuchâtel, Switzerland
      Associate Editor – Tracy Frank
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  • VIRGINIE MATERA,

    1. Institut de Géologie, Université de Neuchâtel, rue Emile Argand 11, CP 158, 2009 Neuchâtel, Switzerland
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  • THIERRY ADATTE

    1. Institut de Géologie, Université de Neuchâtel, rue Emile Argand 11, CP 158, 2009 Neuchâtel, Switzerland
    2. Institut de Géologie et Paléontologie, Université de Lausanne, Anthropôle, 1015 Lausanne, Switzerland (E-mail: Alexis.Godet@unil.ch)
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Abstract

Urgonian-type carbonates are a characteristic feature of many late Early Cretaceous shallow-marine, tropical and subtropical environments. The presence of typical photozoan carbonate-producing communities including corals and rudists indicates the prevalence of warm, transparent and presumably oligotrophic conditions in a period otherwise characterized by the high density of globally occurring anoxic episodes. Of particular interest, therefore, is the exploration of relationships between Urgonian platform growth and palaeoceanographic change. In the French and Swiss Jura Mountains, the onset and evolution of the Urgonian platform have been controversially dated, and a correlation with other, better dated, successions is correspondingly difficult. It is for this reason that the stratigraphy and sedimentology of a series of recently exposed sections (Eclépens, Vaumarcus and Neuchâtel) and, in addition, the section of the Gorges de l’Areuse were analysed. Calcareous nannofossil biostratigraphy, the evolution of phosphorus contents of bulk rock, a sequence-stratigraphic interpretation and a correlation of drowning unconformities with better dated sections in the Helvetic Alps were used to constrain the age of the Urgonian platform. The sum of the data and field observations suggests the following evolution: during the Hauterivian, important outward and upward growth of a bioclastic and oolitic carbonate platform is documented in two sequences, separated by a phase of platform drowning during the late Early Hauterivian. Following these two phases of platform growth, a second drowning phase occurred during the latest Hauterivian and Early Barremian, which was accompanied by significant platform erosion and sediment reworking. The Late Barremian witnessed the renewed installation of a carbonate platform, which initiated with a phase of oolite production, and which progressively evolved into a typical Urgonian carbonate platform colonized by corals and rudists. This phase terminated at the latest in the middle Early Aptian, due to a further drowning event. The evolution of this particular platform segment is compatible with that of more distal and well-dated segments of the same northern Tethyan platform preserved in the Helvetic zone of the Alps and in the northern subalpine chains (Chartreuse and Vercors).

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