Sedimentology and U-Pb dating of Carboniferous to Permian continental series of the northern Massif Central (France): Local palaeogeographic evolution and larger scale correlations

The Carboniferous to Permian volcanic-sedimentary succession shown by the LY-F core from the Lucenay-lès-Aix area, in the northern part of the Massif Central, has been studied in order to obtain both landscape reconstructions (sedimentological analyses) and geochronological constraints (U-Pb dating on zircon and apatite). The lowermost part of the core consists mainly of lacustrine deposits with Gilbert-type delta and volcaniclastic-rich fan delta deposits including several altered volcanic ash layers (tonstein). In contrast, in the uppermost part of the core, playa-lake deposits dominate. LA-ICP-MS U-Pb analyses were performed on both zircon and apatite grains from interbedded tonsteins. This coupled U-Pb dating approach allows to assess potential reworking of volcanic material or the occurrence of non-volcanic grains, such as xenocrysts, in order to provide better evaluations for the depositional ages of the tonsteins. These investigations reveal that sedimentation took place between the late Gzhelian and the late Sakmarian (i.e., between c. 301 and 290 Ma). This sedimentary succession can therefore be compared to those from adjacent basins for which geochronological constraints are available (i.e., Autun and Lodève basins, resp. located north and south of the Massif Central). This study provides a reference section for future comparisons with similar sections from other Carboniferous to Permian basins, in France as well as elsewhere in Europe.