Lower Cretaceous inversion of the European Variscan basement: record from the Vendée and Limousin (France)

Abstract : The post-orogenic evolution of the European Variscan basement remains difficult to constrain due to the absence of post-orogenic sedimentary records. One of the current ways to access this history is to constrain the thermal evolution of these basement areas through indirect methods such as low-temperature thermochronology (LTT) thermal modelling. In this study, apatite fission-track (AFT) data have been acquired for the north-eastern part (Vendée and Limousin) of the French Massif Central Variscan basement. Similar thermal inversion procedure has been done, assuming that some samples were close to the surface during Triassic times. The results show a complex post-Variscan evolution of the western part of the Massif Central. Inversion of the AFT data indicates a high-temperature event during the Jurassic period. This thermal event can be interpreted as the deposition of a significant sedimentary cover which has been later eroded during the Late Jurassic and/or Early Cretaceous. Interpretation of the thermal models implies the presence of the sampled rocks close to the surface during Cretaceous and Eocene times. The estimated volume of this eroded sedimentary cover suggests a probable larger extension of the surrounding sedimentary basins (Paris Basin and Aquitaine Basin) across the Variscan basement area.