Comments on the paper entitled: 'New structural constraints on the southern Provence thrust belt (France): Evidences for an Eocene shortening event linked to the Corsica-Sardinia subduction' by L. Andreani, N. Loget, C. Rangin and X. Le Pichon, Bull. Soc. Géol. Fr., (2010), 181, no 6, 547-563

摘要

We discuss the Andreani et al.'s tectonic interpretation of both la Nerthe and L'Etoile ranges, which form the western part of the southern Provence thrust defined by Aubouin and Chorowicz [1967]. Referring to previous works, emphasis is given to the structural independence of the two ranges. The western L'Etoile range is underthrusted beneath the southern La Nerthe tectonic unit along the Graffiane key-area Aptian corridor. In contrast with the autochthonous concept of La Nerthe range by Andreani et al., structural and paleogeographic data are presented, supporting the interpretation of the southern part of the range as an important north-verging thrust emplaced during the Bartonian major tectonic event. This one was followed by a shortening Ludian (Priabonian) event resulting in a strong refolding of the southern La Nerthe structures. Contrary to the Andreani et al's interpretation, field facts provide evidence that the W-E trending fault systems affecting La Nerthe and L'Etoile ranges have formed during the N-S distensive regime that started from early Rupelian and that was accentuated during late Chattian and Aquitanian. However, stratigraphical and tectonic regional data suggest a Middle Oligocene strike-slip reactivation of the WE trending system faults of La Nerthe range, coeval to north-verging overthrusting and reverse faulting, affecting early Oligocene formations of the neighbouring Marseilles basin.