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Dynamique des paléoenvironnements à huîtres du Crétacé Supérieur nord-aquitain (SO France) et du Mio-Pliocène andalou (SE Espagne) : biodiversité, analyse séquentielle, biogéochimie

Abstract : From the study of the Upper Cretaceous of the Aquitain Basin (Charentes, France) and of the Upper Neogene of the Sorbas basin (SE Spain), oysters can be useful at different scales of analyses: (1) Oyster assemblages have a great diversity of geometries. Their accumulation could be tridimensional, (in a shelly a bed) or bidimensional, with colonisation of a surface. A taphonomic analysis could be used to discriminate several find of assemblages according to their palaeoecological interests. Their organisation (geometry, population density...) often reveal sedimentary dynamics, can help to underline particular stratigraphic surfaces and can be used for the interpretation of sedimentary units. Such results could be useful for sequence stratigraphy analyses. (2) Species are distributed on numerous various environments. Each one of these species and their morphotypes are restricted to specific environmental conditions. Study of numerous parameters controlling their distributions (salinity, oxygenation, turbidity, quality of the substratum, bathymétry...) have be realised. Thus it is possible to reconstitute precisely climatic and edaphic parameters. (3) Shells record seasonal environmental fluctuations by sclerochronological studies and study of the stable isotopes composition (C&O) of their shell increments allow to characterise these seasonal variations. Sclerochronological studies allow to accede absolute age of each specimen too and then to reconstitute population dynamics. Therefore it is possible to characterise time of deposition of shellbeds (from several years to century time scale). Isotopic studies demonstrate that shell recording of sea water condition by Neopycnodonte is affected by a minor vital effect. The analyse of oxygene signal of Upper Cenomanian and Upper Campanian shells show a cyclic pattern that could be attributed to climatic seasonal variations.
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https://tel.archives-ouvertes.fr/tel-00006038
Contributor : Alain-Hervé Le Gall <>
Submitted on : Friday, May 7, 2004 - 4:03:46 PM
Last modification on : Thursday, January 14, 2021 - 11:41:33 AM
Long-term archiving on: : Wednesday, November 23, 2016 - 4:20:40 PM

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Blaise Videt. Dynamique des paléoenvironnements à huîtres du Crétacé Supérieur nord-aquitain (SO France) et du Mio-Pliocène andalou (SE Espagne) : biodiversité, analyse séquentielle, biogéochimie. Autre. Université Rennes 1, 2003. Français. ⟨tel-00006038⟩

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