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Les foraminifères benthiques des Faluns du Miocène moyen du Blésois (Loir-et-Cher) et de Mirebeau (Vienne) dans le Centre-Ouest de la France

Jean-Pierre MARGEREL & Jean-Pierre MARGEREL

fr Geodiversitas 31 (3) - Pages 577-621

Published on 30 September 2009

Middle Miocene Benthic Foraminifera from the Faluns of Blésois (Loir-et-Cher) and of Mirebeau (Vienne) in the Center-West of France.

The “Faluns du Blésois” (Loir-et-Cher) and “Falun de Mirebeau” (Vienne), in Central-Western France, constitute the easternmost deposits of Mid-Miocene age due to the transgression of Atlantic waters. Benthic Foraminifera are diversified and very well preserved. The unilocular hyaline species are particularly abundant and diverse. One hundred eighty six species are listed and among which eight are new : Fissuripolymorphina plana n. sp., Lagenosolenia acarinata n. sp., Palliolatella robusta n. sp., Seguenzaella miocenica n. sp., Buliminella arcuata n. sp., Bisaccioides tonnetoi n. sp., Parrellina notonieri n. sp., Falsobolivina lobata n. sp. Three of those species are assigned to the new genera: Seguenzaella n. gen. and Falsobolivina n. gen. Two stratigraphic units are distinguished in the “Faluns”, each characterized by its sedimentary facies and its taxon association. All listed species occurs in the basal unit (fine sand), but diversify and abundance vary in according to grain-size. The taxonomic richness is impoverished in the coarser interbeded sands. As a consequence, only a few large-sized species occur in the upper unity on account of the coarse granulometry and strong hydrodynamism. Some species are common to Central and Western Tethyan Basin, but affinities with the diversity of the Aquitaine basin is much higher. The microfauna of the Blésois and Mirebeau Faluns announce the species diversity found in the Pliocene of the North Western France, with the survival of many taxa.
Keywords :
Benthic foraminifera, unilocular, systematics, middle Miocene, Central-Western France, paleoecology, paleoenvironments, comparative paleogeography
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