Evidence of decoupled deformation during Jurassic rifting and Cenozoic inversion phases in the salt-rich Corbières-Languedoc Transfer Zone (Pyreneo-Provençal orogen, France)

Abstract

A detailed field study of Jurassic tectono-stratigraphic architecture of the southwestern part of the Corbières-Languedoc Transfer Zone (CTZT) in the French Pyrenees demonstrates for the first time 3D variations in thickness and stratigraphic geometries on near-orthogonal syn-sedimentary structures linked to Jurassic extension with salt. Some of these structures were previously interpreted as compressional and Pyrenean in origin (Late Santonian-Eocene). Our study instead shows that these are extensional salt- related structures that were reactivated during Pyrenean compression and again during Oligo-Miocene extension. We propose that the structures evolved through a strong interaction between inherited crustal structures of the same orientation, and salt tectonics. Strong segmentation of the CLTZ supra-salt cover by oblique structures, is inherited from Jurassic and is linked to interaction between basement EW structures of the Pyrenean rift domain and NE-SW structures of the European Tethyan margin. We distinguish NE-SW trending stuctures (Cévenoles) as extensional forced folds and NE-SW trending salt ridges that developed above basement cutting faults NE-SW oriented. Salt ridges delimited the future NE-SW trending orogenic domains (retro-foreland, Frontal, Main Nappe). N110 trending Pyrenean structures are represented by the Treilles Fault, a major syn sedimentary fault that roots into Keuper evaporites. This study shows that the Corbières is a key area to better understand Pyreneo-provençal evolution along its whole Wilson cycle (rift to rift) and to better understand the processes that govern the formation of a salt-rich rift transfer zone in a strongly pre-structured crust, its positive inversion and the role of salt tectonics in different deformation phases.

A new look at old debates about the Corbières (NE-Pyrenees) geology: salt tectonics and gravity gliding

“…Several unconformities, attributed to Mesozoic compressive events, were recognized under the Aptian (Mattauer & Proust 1962) and the Cenomanian (Durand-Delga 1964) in addition to the general ante-Maastrichtian unconformity known at regional scale [review in Durand-Delga & Charrière (2012)]. After a presentation of the general context and the details of the debates to which they gave rise, we will show that, in agreement with recent work in adjacent regions (Ford & Vergés 2020;Crémades et al 2021), these early unconformities are well explained by the activity of Triassic salt (halokinesis) during the Mesozoic rifting phases and not by compressional events.…”

Evolution of a low convergence collisional orogen: a review of Pyrenean orogenesis

“…Upper Triassic salt was first mobilised during Jurassic gentle rifting and post-rift subsidence. This is particularly well documented in eastern Pyrenean regions that were affected by Jurassic Tethyan rifting (e.g., Crémades et al, 2021;Vergés et al, 2020). A major phase of passive diapirism during Aptian-Cenomanian rifting affected the whole Pyrenean area.…”

“…Further east on the European plate margin a major transfer zone links the Pyrenean and Provencal rift systems (Corbières-Languedoc Transfer Zone, CLTZ, Fig. 3; Crémades et al, 2021). Although some plate tectonic models integrate a wide early Cretaceous oceanic domain between Europe and Iberia (some 300 km wide; e.g., Sibuet et al, 2004;Vissers and Meijer, 2012a, b), no evidence of oceanic crust (i.e., ophiolites) or of oceanic subduction of appropriate age (e.g., calc-alkaline volcanism) has been found.…”

“…Four onshore regions are notable for their abundant Upper Triassic evaporites (> 1 km) and well-developed diapirs: two on the Iberian plate, the Basque-Cantabrian belt (up to 2700 m in southern sectors; Ramos et al, 2022) and the South Central Pyrenean Unit (SCPU; up to 2700 m; Ríos, 1948;Serrano and Martínez del Olmo, 1990;Lopez-Mir et al, 2014;Saura et al, 2016;Caméra and Flinch, 2017;Espurt et al, 2019a;, and two on the European plate, the western NPZ and western Aquitaine Basin (> 1000 m; see Figs. 8a and 8c; Henry and Zolnai, 1971;Canérot, 1988;James and Canérot, 1999;Canérot et al, 2005;Biteau et al, 2006;Serrano et al, 2006;Espurt et al, 2019a;Labaume and Teixell, 2020) and the eastern North Pyrenean Zone and Corbières-Languedoc Transfer Zone (Viallard, 1987;Gorini et al, 1991;Ford and Vergés, 2021;Crémades et al, 2021). The remaining Pyrenean thrust belts are characterized by absent, thin and often discontinuous Upper Triassic evaporites.…”

“…The NPZ finally curves eastward into the N-S trending Corbières-Languedoc transfer zone (Fig. 3) where syn-orogenic successions north of the Mouthoumet massif lie in superimposed N-S and E-W folds and are overthrust from the east by the salt-rich Corbières nappe that records significant rotations (Rouvier et al, 2012).The transfer zone is primarily controlled by the presence of thick Triassic salt and reactivation of both the inherited NE-trending Tethyan passive margin crustal structures and the superimposed Pyrenean E-W rift system (Crémades et al, 2021).…”