Reconstruction of the Provence Chain evolution, southeastern France
Résumé
The Provence fold-and-thrust belt forms the eastern limit of the Pyrenean orogenic system in southeastern France. This belt developed during the Late Cretaceous-Eocene Pyrenean-Provence compression and was then deformed by Oligocene-Miocene Ligurian rifting events and Neogene to present-day Alpine compression. In this study, surface structural data, seismic profiles, and crustal-to-lithospheric-scale sequentially balanced cross sections contribute to the understanding of the dynamics of the Provence Chain and its long-term history of deformation. Balanced cross sections show that the thrust system is characterized by various structural styles, including deep-seated basement faults that affect the entire crust, tectonic inversions of Paleozoic-Mesozoic basins, shallower decollements within the sedimentary cover, accommodation zones, and salt tectonics. This study shows the prime control of the structural inheritance over a long period of time on the tectonic evolution of a geological system. This includes mechanical heterogeneities, such as Variscan shear zones, reactivated during Middle Cretaceous Pyrenean rifting between Eurasia and Sardinia. In domains where Mesozoic rifting is well marked, inherited basement normal faults and the thermally weak crust favored the formation of an inner thick-skinned thrust belt during Late Cretaceous-Eocene contraction. Here 155 km (similar to 35%) of shortening was accommodated by inversion of north verging crustal faults, north directed subduction of the Sardinia mantle lithosphere, and ductile thickening of the Provence mantle lithosphere. During the Oligocene, these domains were still predisposed for the localized faulting of the Ligurian basin rifting and the seafloor spreading.
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