Morphogenetic impact of microbial mats on surface structures of Kimmeridgian micritic limestones (Cerin, France)

Authors

  • P. BERNIER,

    1. Université Claude-Bernard, Centre des Sciences de la Terre et Unité de Recherches Associée au C.N.R.S., no. 11, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
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  • C. GAILLARD,

    1. Université Claude-Bernard, Centre des Sciences de la Terre et Unité de Recherches Associée au C.N.R.S., no. 11, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
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  • J. C. GALL,

    1. Université Louis-Pasteur, Institut de Géologie, 1, Rue Blessig, 67084 Strasbourg, France
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  • G. BARALE,

    1. Université Claude-Bernard, Laboratoire de Paléobotanique et Unité de Recherches Associée au C.N.R.S., no. 11, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
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  • J. P. BOURSEAU,

    1. Université Claude-Bernard, Centre des Sciences de la Terre et Unité de Recherches Associée au C.N.R.S., no. 11, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France
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  • E. BUFFETAUT,

    1. Université Pierre et Marie Curie, Laboratoire de Paléontologie des Vertébrés, 4, Place Jussieu, 75230 Paris Cedex 04, France
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  • S. WENZ

    1. Muséum National d'Histoire Naturelle, Laboratoire de Paléontologie, 8, Rue de Buffon, 75008 Paris, France
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ABSTRACT

For several years, palaeoecological research has been conducted on micritic limestones of late Kimmeridgian age in the southern Jura Mountains. The sedimentary environment is that of a lagoon with an irregular bottom, which was repeatedly exposed. Between two stages of lime deposition, a microbial mat grew over the muddy surface, giving cohesion to the sediment, restraining erosion and preserving fossil remains and reptile tracks. Various structures at the microbial mat surface can be observed: crescentic wavy, radial wavy, torn, petee and mixed structures. They imply the presence of desiccation periods and a slight bottom slope leading to a downward sliding of the microbial mat. Such features may also be generalized to explain superficial microbial structures of other shallow carbonate-mud environments.

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