Microfossil assemblages and relative sea-level fluctuations in a lagoon at the Oxfordian/Kimmeridgian boundary (Upper Jurassic) in the eastern part of the Paris Basin |
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Authors: | Apolline Lefort Bernard Lathuilière Cédric Carpentier Vincent Huault |
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Institution: | 1.Laboratoire G2R,Nancy-Université,Vandoeuvre-lès-Nancy Cedex,France |
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Abstract: | The Late Oxfordian–Early Kimmeridgian interval of the eastern part of the Paris Basin is characterized by a carbonate succession
deposited in shallow-marine platform environments. The Gudmont-Villiers section is represented by deposits ranging from barrier
to typical lagoonal environments often poor in macrofossils. Previously unpublished calcareous microfossils are more abundant
and provide alternative paleoenvironmental indicators. They also provide a biostratigraphical framework across the Oxfordian–Kimmeridgian
boundary. The evolution of microfossil associations (algae and benthic foraminifera) in the lower part of the section, based
on statistical analyses, is correlated to the sea-level variations. The first highly diversified association composed of small
agglutinated and calcitic foraminifera (miliolids, textulariids, Spirillina, Trocholina, Molherina basiliensis etc.) characterizes high sea-level deposits; a second association richer in large agglutinated foraminifera (Alveosepta jaccardi, Everticyclammina, Nautiloculina oolithica) is significantly abundant in low sea-level deposits. A third association characterizes beds with a significant occurrence
of encrusting microorganisms and algae (Lithocodium aggregatum, Troglotella incrustans, Cayeuxia piae, dasycladaceans). The upper part of the section is marked by more argillaceous beds and by the occurrence of one opportunist
taxon (Lenticulina). This study shows that the microfauna-flora evolution in an internal carbonate platform environment constitute an efficient
tool to determine variations in the relative sea level. |
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