Frédéric Gueydan

Jean-Pierre Brun

Mélody Phillippon

Mélanie Noury

Sequential extension as a record of Corsica Rotation during Apennines slab roll-back

The Mediterranean geodynamic system is an exceptional natural laboratory to study the complexities of back-arc extension during subduction rollback. Corsica is a key locality that recorded the Alpine subduction-collision history followed by 30 Ma of the Apennines slab rollback, responsible for the successive opening, from West to East, of the Liguro-Provençal basin and the Tyrrhenian Sea. The overall strain pattern of the Alpine metamorphic units of Alpine Corsica is studied through a synthesis of i) available geological maps, ii) geochronological data and iii) newly acquired structural data relative to successive events of ductile and brittle extension, Three main stages of extension are recorded: 1/ Syn-

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M A N U S C R I P T metamorphic Oligocene extension accommodated by N140° trending ductile shear zones, that correspond to the reactivation of a major Alpine thrust; 2/ Burdigalian ramp-flat extension with N60°-70° trending fault zones that controlled the deposition of onshore piggy-back basins (e.g. St Florent basin), and 3/ Serravalian N-S trending fault zones. From a geodynamical point of view, these successive extensional deformations in Alpine Corsica can be correlated to the history of the Apennines slab rollback. The two first stages are related to a southeastward rollback of the Appennines slab that successively triggered: 1/ Continental rifting in Oligocene leading to the opening of the Liguro-Provençal basin and 2/ Burdigalian extension with N60°-70° trending fault zone, oblique to the Alpine thrust that, after a counterclockwise rotation of the Corso-Sardinian block, became unable to accommodate extension. Finally, the third stage that gave NS-trending fault zones developed in Serravalian, at the onset of Tyrrhenian rifting, related to an eastward rollback of the Apennines slab, as a response of slab tearing in Sicily.

1-Introduction

The Tertiary geodynamic evolution of the Mediterranean mainly corresponds to the formation of three backarc extensional systems (Alboran, Ligurian-Thyrrenian, Aegean-Anatolian) driven by slab rollback (Wortel and Spakmann, 2000;[START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF]). In Central Mediterranean, the rather complex morphology of the Apennines slab is related to 30

Myr of slab rollback responsible for the opening of two major basins: the Liguro-provençal basin and the Tyrrhenian sea [START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF]. In this framework, Corsica has a key position where the Alpine shortening occurred up to 30 Ma and was followed successively by the Liguro-Provençal extension, from 30 to 20 Ma, and the Tyrrhenian extension since 15 Ma [START_REF] Jolivet | Geometry and kinematics of extension in Alpine Corsica[END_REF][START_REF] Molli | Northern Apennine-Corsica orogenic system: an updated overview[END_REF]. The aim of the present paper is to analyse, in the Alpine

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metamorphic units of Corsica (called -Alpine Corsica‖), the 3D structural pattern that resulted from the successive stages of Cenozoic deformation.

Corsica shared with the Alps a common history from Cretaceous to Oligocene [START_REF] Gueguen | On the post-25 Ma geodynamic evolution of the western Mediterranean[END_REF][START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF]. In the Alps, the Penninic thrust that is defined by the boundary between the metamorphic domain that evolved mainly between 70 and 30

Ma (see synthesis in Rosenbaum and Lister, 2004) and the external non-metamorphosed terranes, is underlined by Eocene flysh deposition [START_REF] Handy | Reconciling plate-tectonic reconstructions with the geological-geophysical record of spreading and subduction in the Alps[END_REF] (Fig. 1). In Alpine Corsica, the metamorphic rocks that mainly consist in oceanic derived rocks, the so-called Schistes Lustrés units (SL), have registered a subduction-exhumation cycle with a metamorphic peak dated between 70 Ma and 35 Ma, similar to the Alps [START_REF] Handy | Reconciling plate-tectonic reconstructions with the geological-geophysical record of spreading and subduction in the Alps[END_REF]Malusa et al., 2015) (Fig. 1). The thrust contact between the metamorphic nappe stack and the non-metamorphic external zone (Hercynian basement without sedimentary cover) that is underlined by Priabonian sediments is an equivalent of the Penninic front [START_REF] Caron | Carte géologique de la France (1/50,000[END_REF][START_REF] Molli | Northern Apennine-Corsica orogenic system: an updated overview[END_REF] (Fig. 2).

Since Oligocene, the Alps underwent collision with westward propagation of the external thrusts and Miocene flexural deposits [START_REF] Handy | Reconciling plate-tectonic reconstructions with the geological-geophysical record of spreading and subduction in the Alps[END_REF] (Fig. 1), while Corsica underwent two major extensional events, related to the rollback of the Apennines slab (see synthesis in [START_REF] Molli | Northern Apennine-Corsica orogenic system: an updated overview[END_REF]. First, the opening of the Liguro-Provençal ocean isolated the Corso-Sardinian block from the European plate and, consequently, from the Alpine-related deformation. In Southeast France, several onshore basins at 30 Ma (in late Rupelian; Seranne, 1999) mark that Oligocene continental rifting. Subsequent breakup occurs at 21.5 Ma with the formation of the Liguro-Provençal oceanic basin up to 15 Ma [START_REF] Chamot-Rooke | Constraints on Moho depth and crustal thickness in the Liguro-Provençal basin from a 3D gravity inversion: geodynamic implications[END_REF]. A counterclockwise (ccw) rotation of around 55° of the Corso-Sardinian block, between 21.5 and 15 Ma [START_REF] Edel | La rotation miocene inferieur du bloc corso-sarde; nouvelles contraintes paleomagnetiques sur la fin du mouvement[END_REF][START_REF] Gattacceca | Miocene rotation of Sardinia: new paleomagnetic and geochronological constraints and geodynamic implications[END_REF][START_REF] Rehault | Evolution tectonique et sédimentaire du bassin Ligure (Méditerranée occidentale)[END_REF], controlled Liguroprovençal opening and seafloor spreading. Second, opening of the Tyrrhenian Sea isolated the

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Corso-Sardinian block from the Apennines/Adria [START_REF] Gueguen | On the post-25 Ma geodynamic evolution of the western Mediterranean[END_REF][START_REF] Chamot-Rooke | Constraints on Moho depth and crustal thickness in the Liguro-Provençal basin from a 3D gravity inversion: geodynamic implications[END_REF][START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF]. Basins belonging to the Tyrrhenian Sea display ages that decrease eastward. The opening of the Bastia and Sardinia basins occurred at 32 Ma, attesting for a complex and polycyclic history of basin opening, from Ligurian to Tyrrhenian [START_REF] Mauffret | Tectonics and deep structure of the north-western Mediterranean Basin[END_REF][START_REF] Séranne | The Gulf of Lion continental margin (NW Mediterranean) revisited by IBS: an overview[END_REF] (Fig. 1). The first deposits in the Cornaglia basin are dated at 12 Ma (Chamot-Rooke et al., 1999) (Fig. 1). Rifting started in the Vavilov basin at 7 Ma and breakup and subsequent seafloor spreading occurred at 5-2Ma (Chamot-Rooke et al., 1999) (Fig. 1). At the easternmost tip of the Tyrrhenian Sea, seafloor spreading in the Marsili basin started at 2 Ma and is still active nowadays (Chamot-Rooke et al., 1999) (Fig. 1). This eastward migration of extension recorded the eastward rollback of the Apennines slab [START_REF] Wortel | Subduction and slab detachment in the Mediterranean-Carpathian region[END_REF]Rosenbaum and Lister, 2004;[START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF]. The docking of buoyant continental material to the North and South of the Apennine subduction triggered the tearing of the Apennines slab, which consequently a progressive narrowing of the trench. This event has been responsible for an acceleration of the Apennine slab rollback (Rosenbaum and Lister, 2004).

In Alpine Corsica, the extension-related structures have been mostly attributed to the Ligurian stage of rifting [START_REF] Jolivet | Midcrustal shear zones in postorogenic extension: Example from the northern Tyrrhenian Sea[END_REF]Molli, 2008 and references therein). More specifically, the onshore deposition of the St Florent basin was considered to occur during the Oligocene in the hanginwall of the East Tenda Shear Zone (ETSZ) coeval with the ductile to brittle-ductile extensional exhumation of the Tenda massif in the footwall [START_REF] Fournier | Alpine Corsica Metamorphic Core Complex[END_REF][START_REF] Daniel | Crustal-scale strain partitioning: footwall deformation below the Alpine Oligo-Miocene detachment of Corsica[END_REF][START_REF] Jolivet | Midcrustal shear zones in postorogenic extension: Example from the northern Tyrrhenian Sea[END_REF]. However, [START_REF] Cavazza | The Miocene Saint-Florent Basin in northern Corsica: stratigraphy, sedimentology, and tectonic implications[END_REF], questionned this interpretation by pointing out a 6 Myr gap between cooling ages of the Tenda massif (e.g. Basin (19-18 Ma; Fig. 2) [START_REF] Cavazza | The Miocene Saint-Florent Basin in northern Corsica: stratigraphy, sedimentology, and tectonic implications[END_REF]. Moreover, [START_REF] Fellin | The thermal evolution of Corsica as recorded by zircon fission-tracks[END_REF] suggested that the subsidence of the Saint-Florent Basin was not related to detachment faulting along the In this paper, we first summarize the geological key features of Alpine Corsica. We then present a new tectonic map of Alpine Corsica constrained by i) newly acquired field data (more than 600 structural measurements) and ii) an original synthesis of available geological maps and geochronological data. The main outcome of the study is a characterization of the 3D post-metamorphic deformation pattern, through a detailed mapping of foliation trajectories. We identified three main sets of extensional structures at map-scale and their sequence of development using the sedimentary record from the onshore and offshore Neogene basins. Finally, we interpret the variations of the extension direction in the frame of the Apennines slab rollback and the rotation of Corsica.

2-General structure: Tectonic map of Alpine Corsica

2.1/ Major tectonic units: a tectonic log

Our new structural map of Alpine Corsica is constrained by both (i) a synthesis of data from 11 BRGM geological maps and (ii) data acquired during extensive structural mapping (616 foliation measurements; stereoplot in Fig. 3). The references for the 11 BRGM geological maps are as follows, form North to South and from West to East: Luri (Lahondère et al., 1992), St Florent (Rossi et al., 1994a), Bastia [START_REF] Lahondère | Carte géol[END_REF], Santo Pietro Di Tenda [START_REF] Rossi | feuille Santo-Pietro-di-Tenda[END_REF], Vescovato [START_REF] Lahondère | Carte géol. France (1/50 000[END_REF], Corte [START_REF] Rossi | Carte géol. France (1/50000[END_REF], Cervione [START_REF] Guieu | Carte géol. France (1/50000[END_REF], Venaco (Amaudic du [START_REF] Amaudric Du Chaffaut | Carte géol[END_REF], Pietra di Verde [START_REF] Caron | Carte géologique de la France (1/50,000[END_REF], Ghissonaccia [START_REF] Jauzein | Carte géol[END_REF] and Bastelica [START_REF] Rossi | Carte géol. France (1/50 000[END_REF].

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The geological units belonging to Alpine Corsica have been defined on the basis of their lithology/mineralogy [START_REF] Lahondère | Les schistes bleus et les éclogites à lawsonite des unités continentales et océaniques de la Corse alpine: nouvelles données pétrologiques et structurale[END_REF], metamorphic conditions (synthesis in Vitale Brovarone et al., 2013) and structure [START_REF] Lahondère | Les schistes bleus et les éclogites à lawsonite des unités continentales et océaniques de la Corse alpine: nouvelles données pétrologiques et structurale[END_REF]; BRGM maps and our newly acquired field data). From these criteria, we define six major tectonic units (Fig. 3) and we propose a unified description of the metamorphic nappes from North (Cap-Corse) to South (Castagniccia) that was missing up to now. The non-metamorphosed Hercynian basement crops out to the West and South of Alpine Corsica (Unit 1; Fig. 3). Strongly deformed Eocene basins (nummulites-bearing flyschs) lay unconformably on the non-metamorphosed basement (Unit 2; Fig. 3). These sediments belong to the foreland Eocene basin deposits. A Hercynian basement unit affected by a medium to high-pressure (M-HP) metamorphism (unit 3: Tenda massif, West of St Florent, -External Continental units‖ of [START_REF] Molli | Northern Apennine-Corsica orogenic system: an updated overview[END_REF]-Popolasca, Francardo, Corte, Razzo Bianco) is thrust onto both the non-metamorphosed basement and the Eocene foreland sediments (Unit 3; Fig. 3). This late Eocene thrust is an equivalent of the Alpine Penninic front (Figs. 1 and2). The basal thrust crops out to the West of Corte where it is cut and reworked by late normal faults [START_REF] Molli | Northern Apennine-Corsica orogenic system: an updated overview[END_REF]. Peak metamorphic conditions yield a maximum of 10 kb [START_REF] Gueydan | Analysis of continental midcrustal strain localization induced by microfracturing and reaction-softening[END_REF]Malosoma et al., 2006;[START_REF] Malasoma | HP/LT metamorphism in the Volparone Breccia (Northern Corsica, France): evidence for involvement of the Europe/Corsica continental margin in the Alpine subdution zone[END_REF]. For clarity and simplicity, we refer to these continental metamorphic units as the Tenda unit sensu lato (s.l.) (Fig. 3). They can be interpreted either as the low-pressure (LP) equivalent of the Alpine internal crystalline massifs or as the exhumed deep portion of the external crystalline massifs, structurally located below the Penninic front. [START_REF] Jolivet | Midcrustal shear zones in postorogenic extension: Example from the northern Tyrrhenian Sea[END_REF][START_REF] Molli | Northern Apennine-Corsica orogenic system: an updated overview[END_REF]discussion in Vitale-Brovarone et al., 2013) (Fig. 2). Above this unit, two oceanic dominated units can be distinguished mainly based on their degree of Alpine metamorphism. The Lower oceanic unit (unit 5 regrouping the Mandriale, Farinole and Morteda units of [START_REF] Lahondère | Les schistes bleus et les éclogites à lawsonite des unités continentales et océaniques de la Corse alpine: nouvelles données pétrologiques et structurale[END_REF]Fig. 3) consists of basalts, gabbros and peridotites with slices of eclogitic gneisses. It recorded pressure conditions ranging from 22 to 24 kb, which are the maximum pressure conditions recorded by the entire Alpine nappe stack [START_REF] Ravna | Cold subduction and the formation of lawsonite eclogiteconstraints from prograde evolution of eclogitized pillow lava from Corsica[END_REF]Vitale-Brovarone et al., 2013). Above this unit, the Upper oceanic unit (unit 6 regrouping the Pigno, Gratera, Centuri, Inzeca, Vecchio, Linguizzetta, Santa Lucia and Balagne units of [START_REF] Lahondère | Les schistes bleus et les éclogites à lawsonite des unités continentales et océaniques de la Corse alpine: nouvelles données pétrologiques et structurale[END_REF]Fig. 3) recorded a low to medium pressure (L-MP) metamorphism (maximum 10 kb; Vitale-Brovarone et al., 2013).

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The Balagne unit is non-metamorphosed and contains obducted oceanic material: serpentinite, gabbros, pillows lavas and oceanic flysch sediments. Santa Lucia and Pigno units consist of continental fragments with L-MP metamorphism [START_REF] Jolivet | Midcrustal shear zones in postorogenic extension: Example from the northern Tyrrhenian Sea[END_REF]. Note that within the Upper oceanic unit, pseudotachylites have been recently discovered in the Gratera units at

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medium pressure (transition from greenschits to blueschists facies in meta-gabbros and peridotites; [START_REF] Austrheim | Pseudotachylytes from Corsica: fossil earthquakes from a subduction complex[END_REF][START_REF] Andersen | Fossil earthquakes recorded by pseudotachylytes in mantle peridotite from the Alpine subduction complex of Corsica[END_REF].

Miocene sediments deposited on top of the previously defined units (mainly SL) are found in three onshore basins: Saint Florent, Francardo and Aleria (Unit 7; Fig. 3). Within these basins, the sedimentary record ranges from Burdigalian to Messinian. The Francardo and St Florent basins contain exclusively 20-14 My old deposits (Burdigalian to Langhian; [START_REF] Cavazza | The Miocene Saint-Florent Basin in northern Corsica: stratigraphy, sedimentology, and tectonic implications[END_REF]Ferrandini,1999)

(Fig 2). The Aleria basin contains Burdigalian to

Pliocene sediments with a chance of depocenter location during Langhian (Fig. 3).

2.2/ Ductile deformation

The metamorphic units (Tenda s.l. and SL) recorded two events of ductile deformation. First, a top-to-W-SW shearing is observed in HP-LT assemblages, resulting from subduction-related thrusting [START_REF] Malavieille | Evolutionary model for Alpine Corsica: mechanism for ophiolite emplacement and exhumation of high-pressure rocks[END_REF][START_REF] Molli | Northern Apennine-Corsica orogenic system: an updated overview[END_REF][START_REF] Fournier | Alpine Corsica Metamorphic Core Complex[END_REF][START_REF] Daniel | Crustal-scale strain partitioning: footwall deformation below the Alpine Oligo-Miocene detachment of Corsica[END_REF][START_REF] Jolivet | Midcrustal shear zones in postorogenic extension: Example from the northern Tyrrhenian Sea[END_REF]. The ages of top-to-W-SW shearing are late

Cretaceous in SL and Mid-Eocene in Tenda (Fig. 2 with references in caption) (Brunet et al., 2002;synthesis in Vitale-Brovarone et al., 2013). This implies two stages of HP-LT metamorphism and associated deformation. Recent age constraints on SL unit seem to indicate a synchronous sudbuction of the Tenda massif and SL [START_REF] Vitale Brovarone | Timing of HP metamorphism in the Schistes Lustrés of Alpine Corsica: New Lu-Hf garnet and lawsonite ages[END_REF]. Despite this complexity, the ductile deformation with top-to-W-SW shearing indicates that the contact between the major tectono-metamorphic units presented above are thus major thrusts [START_REF] Caron | Metamorphism and deformation in Alpine Corsica[END_REF][START_REF] Lahondère | Les schistes bleus et les éclogites à lawsonite des unités continentales et océaniques de la Corse alpine: nouvelles données pétrologiques et structurale[END_REF][START_REF] Harris | Progressive and polyphase deformation of the Schistes Lustrés in Cap Corse, Alpine Corsica[END_REF]Malavielle et al., 1998;[START_REF] Mattauer | Tectonics Transverse lineation and largescale structures related to Alpine obduction in Corsica[END_REF][START_REF] Molli | Deformation and metamorphism at the eastern border of the Tenda Massif (NE Corsica): a record of subduction and exhumation of continental crust[END_REF], formed within the subduction zone. The internal structures of these units are complex and commonly show isoclinal folding, typical of thrust related structures. Our study does not concern this syn-metamorphic deformation, but aims at understanding the deformations that occurred at shallower levels, after thrusting and

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subsequent exhumation -i.e. low metamorphic to post-metamorphic deformations. Following thrusting, a second ductile deformation event was recorded with top-to-E shearing synchronous to HP to LP mineral assemblages, suggesting an exhumation-related deformation whose ages are also diachronous, starting in Paleocene in the SL and in late Eocene/Early Oligocene in the Tenda (Brunet et al., 2002) (Fig. 2). Two stages of ductile deformation related to exhumation thus characterize Alpine Corsica. An Eocene ductile exhumation only recorded in the SL with top-to-E shearing and an OIigocene ductile exhumation of the Tenda and also recorded in the SL with also top-to-E shearing.

2.3/ Foliation trajectories

The metamorphic foliation of Alpine Corsica is a first order marker of later extensional deformations that occurred since Oligocene, even if some variations in the foliation attitude (i.e. strike and dip) can be related to pre-Oligocene deformations responsible for foliation development. The trajectories of bedding-parallel high-pressure foliations (Fig.

3

) that were drawn from 616 foliation measurement sites (Stereoplot; Fig 3) filter variations of foliation direction occurring at scales lower than 100m. Therefore, they provide an excellent mapping tool to identify and characterize structures larger than this threshold. Two main types of structures are put in evidence: folds and fault zones (Figs. 3 and4).

2.3.1/ Map-scale folds

On average, foliations dip westward with a mean N-NE trend. However, in three areas, Saint Florent, North of Cap Corse and southern rim of Castagniccia, a NE trend occurs with steep dips evolving from NW to SE. Three major synforms with a NE-SW trending axes affect the foliation, which from North to South are: the Centuri, the Saint Florent and the Aleria synforms (Figs. 3 and 4). In between, the deepest SL units (Castagniccia unit, Unit 4)

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form antiformal structures with N to NE axes, namely the Cap Corse and the Castagniccia antiforms (Fig. 3 and4). The obliquity of synform and antiform axes reflects a superposition of different extensional events that we discuss below.

2.3.2/ Map-scale fault zones

Deflections and/or discontinuities of foliation trajectories define major fault zones at map-scale in both the ETSZ and the SL. These fault zones are not single faults but consist in narrow (from 100m to 1 km wide) steeply-dipping corridors in which the foliation is downward bent, as it will be detailed below. They are associated to folds from some km to some 10km scales. In these fault zones, meter-scale normal faults are widespread generally steeping at deeper angles than the foliation. As striaes are seldom observed on the fault planes it must be mentioned that the obliquity angle between faults and foliation indicates a dip-slip sense of shear or close to dip-slip. This validates the kinematic interpretation of these largescale fault zones.

We identify and map three main trends of these fault zones:

1/ N140° (grey in Figs. 3 and4) mainly located at the rim of the Tenda massif (ETSZ)

and locally within the SL nappes 2/ N60°-70° (red in Figs. 3 and4) that control the foliation trend and define the three synforms of Centuri, St Florent and Aleria.

3/ N-S (blue in Fig. s 3 and4) that mostly control the foliation trend in the eastern part of the island.

Cross-cutting relationships (Figs. 3 and4) indicate that the three fault zone systems developed in the following order: N140° first, N60-70° second and N-S third.

/ Alpine thrust reactivation: N140° ductile faults

The East Tenda Shear Zone, in the eastern rim of the Tenda massif (Fig. 3), is the most spectacular example of the extensional reactivation of an Alpine thrust that occurred during the ductile exhumation of the Tenda massif [START_REF] Jolivet | Midcrustal shear zones in postorogenic extension: Example from the northern Tyrrhenian Sea[END_REF][START_REF] Daniel | Crustal-scale strain partitioning: footwall deformation below the Alpine Oligo-Miocene detachment of Corsica[END_REF][START_REF] Gueydan | Analysis of continental midcrustal strain localization induced by microfracturing and reaction-softening[END_REF][START_REF] Molli | Deformation and metamorphism at the eastern border of the Tenda Massif (NE Corsica): a record of subduction and exhumation of continental crust[END_REF]. Figure 5 shows a NW-SE cross-section of the ETSZ (see location EE' in Fig. 3) that highlights the superposition of two main deformation stages, associated with two superposed ductile fabrics.

The first foliation S1 that bears HP mineral (crossite, phengite; [START_REF] Gueydan | Analysis of continental midcrustal strain localization induced by microfracturing and reaction-softening[END_REF][START_REF] Molli | Deformation and metamorphism at the eastern border of the Tenda Massif (NE Corsica): a record of subduction and exhumation of continental crust[END_REF][START_REF] Maggi | Feedback between fluid infiltration and rheology along a regional ductile-to-brittle shear zone: The East Tenda Shear Zone (Alpine Corsica)[END_REF] [START_REF] Molli | Deformation and metamorphism at the eastern border of the Tenda Massif (NE Corsica): a record of subduction and exhumation of continental crust[END_REF]. Eastward, a progressive folding of the S1 foliation leads to the development of a new axial plane schistosity S2 (Fig. 5) with newly-formed greenschists minerals, attesting that S2 developped at lower pressure (Daniel et al., 1995;[START_REF] Gueydan | Analysis of continental midcrustal strain localization induced by microfracturing and reaction-softening[END_REF][START_REF] Molli | Deformation and metamorphism at the eastern border of the Tenda Massif (NE Corsica): a record of subduction and exhumation of continental crust[END_REF]. The ETSZ is characterized by a northeastward strain gradient (Photos C and D; Fig. 5) and is marked by: 1/ a progressive reduction of the grain size, 2/ a more penetrative S2 planar fabric and 3/ an increase of the number of C'-type shear bands with top-to-NE sense of shear (cross-section; Fig. 5). However, note that, close to the coastline, relicts of S1 folding can be found in the ETSZ mylonites. All together these observations attest for the extensional reactivation of the Alpine Thrust (SL/Tenda contact), as already documented by [START_REF] Molli | Deformation and metamorphism at the eastern border of the Tenda Massif (NE Corsica): a record of subduction and exhumation of continental crust[END_REF]. The strain gradient, from the core of the Tenda massif to the contact with the SL, was probably partly acquired during thrusting, since microlithons of folded S1 foliation in the mylonitic facies also show very small grain sizes (photo D;Fig 5,).

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The ETSZ is thus a demonstrative example of these N140° ductile normal fault zones (grey in Fig 3) that can be founded all along the SL/Tenda boundary but also along the SL/Hercynian basement boundary in Corsica [START_REF] Molli | Northern Apennine-Corsica orogenic system: an updated overview[END_REF]. These N140° trending normal ductile fault zones are associated with retrograde metamorphic reactions and hence suggest that they contribute to the unroofing of the Tenda massif from 15-20 km to shallower levels while the SL were already in upper crustal conditions.

The two other observed fault zones trend (N60-70° and N-S) are younger and not associated with metamorphic minerals and therefore affect both SL and Tenda in upper crustal -i.e. post-metamorphic-conditions.

3.2/ Two stages of post-metamorphic faulting

3.2.1/ N60°-70° map-scale fault zones and foliation flexures

In is likely related to a strong mechanical anisotropy of the mylonites. This is illustrated by an attenuation of the deflexion of foliation trajectories away from the ETSZ, in relation with a decrease of the degree of pre-existing mylonitic anisotropy (Fig. 6a). In other words, the ETSZ is strongly reworked by N60°-70° trending deformation zones giving arcuate patterns of foliation trajectories at map scales (up to 5-6 km; Figs. 3 and6)

Similar arcuate foliation trajectories also occur in the SL of Alpine Corsica, within narrow N60°-70° trending deformation zones, that correspond to flexures (see location of major flexures in Fig. 4). Flexures consist of localized folding, with steeply dipping axial planes and shallow plunging fold axes, always associated to asymmetric synforms and antiforms at regional scale. Two major flexures are observed onshore: one North of St Florent Syncline (Bastia flexure) and the other North of the Aleria Basin (Aleria flexure; Figs. 3 and4).

Figure 7 shows a close-up North of Bastia, south of Erbalunga (see location in Fig 3)

where, over a distance of around one kilometre, the foliations evolve from gently dipping to steeply dipping and gently dipping again, defining a couple of asymmetric antiform and synform in the fault zone footwall and hangingwall, respectively. Foliation measurements carried out at a favourable site (Stereoplot, Fig. 7) define an asymmetric fold with a horizontal axis oriented N65°. Numerous normal faults with a mean N65° trend (Stereoplot; Fig. 6b) occur within the flexure with a top-to-SE sense of shear (Photographs; Figs. 7c andd).

On these bases, the flexure is the expression of a simple shear along a plane steeply dipping to the SE. In other words, instead of a single large normal fault, it is a deformation zone of distributed normal sense shearing accommodated by widespread small-scale normal faults. The above observations and measurements suggest that the foliation is first downward bent and, with the decrease of the angle between the shear direction and the foliation, the rock anisotropy become able to stimulate the development of a dominant set of normal faults at a

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low angle to the foliation (For a complete discussion of the mechanical effects of rock anisotropy see [START_REF] Cobbold | Development of internal structures in deformed anisotropic rocks[END_REF][START_REF] Cosgrove | The influence of mechanical anisotropy on the behaviour of the lower crust[END_REF].

In summary, the N60°-70° oriented fault zone structures (Figs.

/ N-S structures

Finally, N-S trending flexures are located to the Southeast of Castagniccia and along the eastern coastline of Cap Corse (Figs. 3 and4). Figure 8 documents one of these N-S flexures, near the San Nicolao village (location on Fig. 3). Foliation trajectories rapidly change in few km from gently NE-dipping to steeply E-dipping with a N-S trend (outcrop pictures and map in Fig. 8). At map scale, this N-S trending fault zone controls the eastern limbs of both the Cap Corse anticline and the Castagniccia anticlines (Fig. 3), defining a mean N-S trend oblique to the NE-SW trends of the Centuri, St Florent and Aleria synclines (Figs.

3 and 4). The Cap-Corse and Castagniccia anticlines therefore reflect the superposition of two extensional deformation events, respectively associated to N60°-70° and N-S trending normal fault systems. In the Aleria basin, map-scale relationships (Fig. 3) illustrate i) that the N-S

A C C E P T E D M A N U S C R I P T

trending fault zone cross-cuts and offsets the N60°-70° trending fault zone and ii) that a change in depocenter geometry associated to N-S faults occurred in middle Miocene.

4/ Interpretation: Sequential extension

The three types of extensional fault zones observed in Alpine Corsica can be dated using our compilation of geochronological ages (Fig. 2) and basin stratigraphy as reported in Figure 9 (see references in caption of Fig. 2).

4.1/ Oligocene extensional reactivation of an Alpine thrust

In the ETSZ, 40 Ar/ 39 Ar ages on minerals that define the S1 foliation yield an age ranging between 40 and 33 Ma while minerals that define the S2 foliation or C'-type shear bands with a top-to-E sense of shear yield ages between 32 and 25 Ma (Brunet et al., 2002) (Fig. 9). Therefore, the extensional ductile reactivation of the N140° trending ductile Alpine Thrust (SL/Tenda massif contact) occurred during Oligocene. These N140° trending normal fault zones are associated with retrograde metamorphism suggesting that they contribute to the unroofing from a15-20 km depth of the Tenda massif to shallower crustal levels whereas the SL units were already in upper crustal conditions.

Whereas some onshore Oligocene deposits are known in Sardinia (see synthesis in [START_REF] Faccenna | Extensional tectonics on Sardinia (Italy): insights into the arc-back-arc transitional regime[END_REF], there is no onshore Oligocene deposit in Corsica. Alpine Corsica was therefore most probably a structural high bounded by two major extensional faults (i.e. horst) trending N140° (offshore) during the Oligocene rifting. The Solenzara fault (N140° trending fault that bounds the Aleria Basin to the West, Fig. 3) acted as an extensional fault in Oligocene/early Miocene that controlled the deposition of Oligocene in the offshore part of the Bastia basin (see location in Fig. 1) [START_REF] Mauffret | Tectonics and deep structure of the north-western Mediterranean Basin[END_REF]1998). In summary, Oligocene

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rifting is accommodated in Alpine Corsica by the reactivation of an Alpine thrust resulting in the present day pattern of N140° trending fault zones, but without deposition and/or preservation of onshore sediments.

4.2/ Burdigalian ramp-flat extension and onset of onshore basin deposition

As quoted by [START_REF] Fellin | The thermal evolution of Corsica as recorded by zircon fission-tracks[END_REF] and [START_REF] Cavazza | The Miocene Saint-Florent Basin in northern Corsica: stratigraphy, sedimentology, and tectonic implications[END_REF], the deposition of onshore Burdigalian basins is not related to the ductile exhumation of the Tenda massif. The novelty of our study is the tectonic framework that controlled basin deposition during this period, after Liguro-Provençal break-up and prior to Tyrrhenian rifting.

The N60°-70° trending fault zones crosscut N140° trending fault zones and are therefore younger than Oligocene. The Aleria basin is controlled by such a N60°-70° oriented fault zone, suggesting a Lower Miocene (Burdigalian) age of formation. In the Saint Florent basin, the bedding is NE-dipping, parallel to the foliation of the underlying basement (e.g. in SL in Fig. 3 and cross-section in Fig. 9b), with a mean N60°-70° trend. To the Southeast, the SL units show a similar trend however with a progressive increase of the dip angle (crosssection; Fig. 9).

The St Florent basin is lying conformably on top of the NW limb of the Castagniccia antiform (Figs. 3 and cross-section BB'; Fig. 9). The cross-section AA' presents the entire geometry of the Castagniccia antiform and the projected position of the Saint Florent basin (Fig. 9). The Tenda s.l. has been drawn below the SL as suggested by [START_REF] Molli | Northern Apennine-Corsica orogenic system: an updated overview[END_REF] using available geophysical studies (Berthout et al., 1999). The N60°-70° oriented fault zones are reported in both Tenda and in the SL, as documented in the Figures 6 and7, respectively.

These fault zones define, in the SL nappe stack a narrow synform and a wide antiform, with a flat-lying antiform core. This fold geometry formed during the southeastward displacement of the SL nappe stack above a displacement surface with a ramp-flat geometry. The flat (i.e.

A C C E P T E D M A N U S C R I P T

décollement) corresponds to the interface between the SL and the Tenda basement and the ramp is a normal fault zone that cuts through the SL nappe stack (Castagniccia unit; Fig 9).

Steep normal sense displacement along N60°-70° trending ramp in the SL units (southeastern part of the cross-section AA', Fig. 9) likely corresponds to a normal fault affecting the Tenda basement underneath.

However, the AA' cross-section (Fig. 9) presents a geometry that suggests a least two stages of deformation during the ramp-flat extension. A two-stage model leading to the structure observed in cross-section AA', with two main units of SL (i.e. Castagniccia and the oceanic (lower and upper) units) and the Tenda, is proposed in Figure 10 1/ First, a classical ramp-flat extensional system inspired from analogue models (e.g.

Roure et al 1992) with a ramp within the SL and flats between different SL units and between the SL and the Tenda (Lithological log in Fig. 10). The complex metamorphic nappe stack contains a number of weak layers, such as marbles layers on top of the Castagniccia units or serpentinite at the base of the Lower Oceanic units (see detailed lithological units in Fig. 3) that allowed easy layer-parallel shear (i.e.

flat/décollement). Similarly, the contact between the SL (metamorphic units) and the Tenda s.l. (granitic basement) is a major weak zone. These two inherited weak layers acted as major décollements. Normal faulting of the Castagniccia units provided a ramp that connected the two décollements, allowing an extensional ramp-flat system to develop (Fig. 10a up). During extensional displacement, a syncline developed above the ramp in which the Saint Florent basin was deposited as a piggyback basin (Fig. 10a down). With increasing displacement the sedimentary layers deposited in the basin were tilted together with their basement (Castagniccia units) forming a rollover anticline.

A C C E P T E D M A N U S C R I P T

2/ Second, newly formed N60°-70° trending fault zones crosscut the ramp-flat geometry (Figs. 10b andc) allowing the unroofing of the Tenda massif along its eastern border (see Fig. 5).

The resulting first-order geometry of the Alpine Corsica consists in two ramp-flat systems that controlled the deposition of the St Florent and Aleria basins, lately cross-cut by N60°-70° steep normal fault zones (Fig. 10c). These two stages developed in sequence toward the SE. N60°-70° trending fault zones and related ramp-flat extension occurred during Burdigalian, as exemplified by the syn-kinematic deposition of the Saint Florent piggyback basin. Therefore, the clustering of LT ages between 20 and 15 Ma can be interpreted as related to this major ramp-flat extensional system that lead to the unroofing/cooling of the SL and the Tenda (see compilation of ages in Fig. 11). Note however that new LT data along profiles perpendicular to the inferred N60°-70° fault zones will be essential in a future study in order to better constrain the exact ages of activity of these structures (e.g. ages break across fault zones). In Sardinia, N60°-70° trending faults controlled the deposition of lower Miocene basins (Faccenna et al., 2002 and references therein). To make the general process more easily understandable, we represent the ramp-flat extensional system with an initially flatlying geometry of the metamorphic nappe stack (Fig. 10). It is likely that the initial geometry of the nappe stack was more complex. To incorporate the complexities that our too simple model fails to explain, an assessment of the subsurface geometry through geophysical imaging (e.g. seismics) would be useful.

4.3/ Serravalian N-S extension at the onset of Tyrrhenian rifting

N-S trending fault zones are the youngest extensional structures in Corsica. They controlled a change in depocenter geometry in the Aleria basin during Langhian/Serravalian (Fig. 3). A Langhian/Serravalian unconformity is observed in the Bastia Basin (Fig. 1) that is

A C C E P T E D M A N U S C R I P T
the offshore extent of the Aleria Basin [START_REF] Mauffret | Structural evolution of the Northern Tyrrhenian Sea from new seismic data[END_REF]. This unconformity can result from the switch in fault zones trend from N60° to N-S at the onset of Tyrrhenian rifting [START_REF] Chamot-Rooke | Constraints on Moho depth and crustal thickness in the Liguro-Provençal basin from a 3D gravity inversion: geodynamic implications[END_REF]Seranne;[START_REF] Séranne | The Gulf of Lion continental margin (NW Mediterranean) revisited by IBS: an overview[END_REF][START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF]. Low temperature ages younger than 15 Ma, mostly obtained in the eastern rim of Corsica are likely related to this event [START_REF] Fellin | Relief evolution in northern Corsica (western Mediterranean): Constraints on uplift and erosion on longterm and short-term timescales[END_REF]Fig. 11).

4.4/ Corsica extension as a record of the Apennines slab deformation

The above data and observations show that three stages of extension are recorded in Alpine Corsica (summarized in Fig. 11 consistent with the inferred southeastward Apennines slab rollback [START_REF] Faccenna | Lateral slab deformation and the origin of the western Mediterranean arcs[END_REF]. At that time, the Alpine thrust was oriented almost perpendicular to the stretching direction and therefore ideally oriented for reactivation, and, as a consequence, unroofing of the Tenda massif. Basin deposition did not occur onshore but offshore on both sides of Corsica, in the Ligurian basin and in the Bastia basin [START_REF] Mauffret | Tectonics and deep structure of the north-western Mediterranean Basin[END_REF](Mauffret, et al., , 1998)).

With the ccw rotation of Corsica, easy reactivation of the Alpine thrust progressively decreased. Therefore, new fault zones developed in Burdigalian trending N60°-70°, perpendicular to the NW-SE stretching direction. At regional scale, the en-échelon pattern of these N60°-70° trending fault zones suggests a component of N-S dextral strike-slip motion along the Alpine thrust contact. Such a dextral strike-slip component along N60°-70° trending normal fault zones in both Corsica [START_REF] Maggi | Feedback between fluid infiltration and rheology along a regional ductile-to-brittle shear zone: The East Tenda Shear Zone (Alpine Corsica)[END_REF] and Sardinia [START_REF] Faccenna | Extensional tectonics on Sardinia (Italy): insights into the arc-back-arc transitional regime[END_REF] can be related to the progressive slab deformation during rollback toward the Southeast.

The development in Langhian/Serravalian of N-S trending fault zones indicates a major change in the direction of stretching and hence a switch of rollback direction from southeastward to eastward. This major change in slab rollback dynamics could likely be related to the onset of Africa collision, as recorded in Algeria/Tunisia, leading to a strong slab deformation between North Africa and Italy (Rosenbaum and Lister, 2004)

7/ Conclusion

Using an original compilation of geological and geochronological data together with newly acquired structural data, we evidence that three stages of extension were recorded in the exhumed metamorphic rocks of Alpine Corsica:

1) Oligocene extension accommodated by N140° trending fault zones corresponding to the extensional reactivation of an Alpine thrust; Francardo and Aleria, located in Fig. 3) and Liguro-Provençal and Tyrrhenian sea rifting.

Data are from [START_REF] Brunet | Migration of compression and extension in the Tyrrhenian Sea, insights from 40Ar/39Ar ages on micas along a transect from Corsica to Tuscany[END_REF][START_REF] Cohen | Age of emplacement of the schistes lustres nappe[END_REF]Maluski, 1977;[START_REF] Lahondère | Datation Sm/Nd du métamorphisme éclogitique en Corse Alpine: un argument pour l'existence au Crétacé Supérieur d'une zone de subduction active localisée sous le bloc corso-sarde[END_REF] for Ar/Ar and Nd/Sm ages from [START_REF] Danisík | Burial and exhumation of Corsica (France) in the light of fission track data: Tectonics[END_REF][START_REF] Fellin | Relief evolution in northern Corsica (western Mediterranean): Constraints on uplift and erosion on longterm and short-term timescales[END_REF][START_REF] Fellin | The thermal evolution of Corsica as recorded by zircon fission-tracks[END_REF][START_REF] Zarki-Jakni | Cenozoic denudation of Corsica in response to Ligurian and Tyrrhenian extension: Results from apatite fission track thermochronology: Tectonics[END_REF] for fission track data (AFT, ZFT and U-Th/He), from [START_REF] Bache | Evolution of rifted continental margins: The case of the Gulf of Lions (Western Mediterranean Basin)[END_REF][START_REF] Chamot-Rooke | Constraints on Moho depth and crustal thickness in the Liguro-Provençal basin from a 3D gravity inversion: geodynamic implications[END_REF][START_REF] Edel | La rotation miocene inferieur du bloc corso-sarde; nouvelles contraintes paleomagnetiques sur la fin du mouvement[END_REF][START_REF] Edel | Late Paleozoic rotations of Corsica and Sardinia: New evidence from paleomagnetic and K-Ar studies[END_REF][START_REF] Ferrandini | Chronostratigraphie et paléomagnétisme des dépôts oligo-miocènes de Corse : implications géodynamiques pour l'ouverture du bassin liguro-provençal[END_REF][START_REF] Ferrandini | La formation conglomératique du Vazzio près d'Ajaccio (Corse-du-Sud), un témoin des dépôts du Chattien supérieur continental synrift en Méditerranée occidentale[END_REF][START_REF] Montigny | Oligo-Miocene rotation of Sardinia: K/Ar ages and paleomagnetic data of Tertiary volcanics[END_REF] for Tyrrhenian and Liguro Provençal basins. Figure 2/ Compilation of geochronological ages and of onshore Corsica basins (Saint Florent, Francardo and Aleria, located in Fig. 3) and Liguro-Provençal and Tyrrhenian sea rifting. Data are from [START_REF] Brunet | Migration of compression and extension in the Tyrrhenian Sea, insights from 40Ar/39Ar ages on micas along a transect from Corsica to Tuscany[END_REF][START_REF] Cohen | Age of emplacement of the schistes lustres nappe[END_REF]Maluski, 1977;[START_REF] Lahondère | Datation Sm/Nd du métamorphisme éclogitique en Corse Alpine: un argument pour l'existence au Crétacé Supérieur d'une zone de subduction active localisée sous le bloc corso-sarde[END_REF] for Ar/Ar and Nd/Sm ages from [START_REF] Danisík | Burial and exhumation of Corsica (France) in the light of fission track data: Tectonics[END_REF][START_REF] Fellin | Relief evolution in northern Corsica (western Mediterranean): Constraints on uplift and erosion on longterm and short-term timescales[END_REF][START_REF] Fellin | The thermal evolution of Corsica as recorded by zircon fission-tracks[END_REF][START_REF] Zarki-Jakni | Cenozoic denudation of Corsica in response to Ligurian and Tyrrhenian extension: Results from apatite fission track thermochronology: Tectonics[END_REF] for fission track data (AFT, ZFT and U-Th/He), from [START_REF] Bache | Evolution of rifted continental margins: The case of the Gulf of Lions (Western Mediterranean Basin)[END_REF][START_REF] Chamot-Rooke | Constraints on Moho depth and crustal thickness in the Liguro-Provençal basin from a 3D gravity inversion: geodynamic implications[END_REF][START_REF] Edel | La rotation miocene inferieur du bloc corso-sarde; nouvelles contraintes paleomagnetiques sur la fin du mouvement[END_REF][START_REF] Edel | Late Paleozoic rotations of Corsica and Sardinia: New evidence from paleomagnetic and K-Ar studies[END_REF][START_REF] Ferrandini | Chronostratigraphie et paléomagnétisme des dépôts oligo-miocènes de Corse : implications géodynamiques pour l'ouverture du bassin liguro-provençal[END_REF][START_REF] Ferrandini | La formation conglomératique du Vazzio près d'Ajaccio (Corse-du-Sud), un témoin des dépôts du Chattien supérieur continental synrift en Méditerranée occidentale[END_REF][START_REF] Montigny | Oligo-Miocene rotation of Sardinia: K/Ar ages and paleomagnetic data of Tertiary volcanics[END_REF] for Tyrrhenian and Liguro Provençal basins.

  age of exhumation/extension 30-25 Ma; Fig 2) and the ages of first infill in the St Florent

  compilation of low-temperature (LT) thermochronological ages in the metamorphic units of Alpine Corsica (AFT, U-Th-He in Fig.2and references in figure caption) shows indeed a cluster of ages ranging between 20 and10 Ma, contemporaneous with basin deposition. The first deposit of St Florent occured after the continental break-up in the Liguro-Provençal basin(at 21.5, Chamot-Rooke et al., 1999), implying a « post-rift » environnement instead of a « syn-rift ». The deformation event that triggered rock exhumation, between Ligurian break-up and Thyrrenian rifting, therefore remained to be identified.

  is associated to C'-type shear bands and antithetic rotation of stretched feldspars indicating a top-to-W sense of shear (Photo A; Fig 5) (see also discussion in

  the Tenda massif, N60°-70° trending map-scale fault zones affecting the ETSZ are identified thanks to a high resolution of foliation mapping and foliation trajectories (local map and stereoplot; Fig 6). Molli et al. (2006) already pointed out such strong variations in foliation trend, near St Florent and Santo Pietro di Tenda (see their Figs. 4, 7 and 10). The mean N140° trend of mylonitic foliation in the ETSZ changes abruptly and is re-oriented in a N60°-70° direction within narrow deformation zones (Stereoplot and local map; Fig.6). This evolution that occurred without any metamorphic mineral growth -i.e. post-metamorphic-is closely associated to normal faults trending N65° (stereoplot; Fig.6). Note that this NE deformation zone is not a single normal fault but instead corresponds to a some hundred meters wide zone of distributed brittle-ductile deformation affecting pre-existing mylonitic fabrics (Fig.6 a). This distributed character of deformation, instead of a more localized fault,A C C E P T E DM A N U S C R I P T

  3 and 4) are either narrow zones of localized brittle-ductile deformation in mylonitic gneisses (Tenda units) or larger flexures (i.e. asymmetric folds) in the Schistes Lustrés s.l.. Two major N60°-70° trending zones affect the Alpine Corsica. The St Florent N60°-70° trending fault zone is a broad zone of deformation, with N60-70° trending deformation zone in the Tenda massif and N60°-70° trending flexure in the SL (Bastia Flexure; Fig. 3) that is associated to the St Florent basin depocenter. The Aleria N60°-70° fault zone is a more localized zone of deformation, appearing at map-scale as a single normal fault that delimitates the lower Miocene sediments of the Aleria basin (Fig 3).

  ) : 1/ Oligocene with N140° oriented normal fault zones (extensional reactivation of an Alpine thrust), 2/ Burdigalian with ramp-flat extension and associated N60°-70° trending normal fault zones/flexures and onshore deposition of piggy-back basins (St Florent and Aleria) and 3/ Langhian/Serravalian with N-S oriented fault zones responsible for a spatial change in the sedimentary depocenter in the onshore Aleria basin and an unconformity in the offshore Bastia basin. Our compilation of ages as well as basin stratigraphy allows an accurate dating of these three stages, with medium temperature (MT) cooling ages (Ar/Ar) for the first stage, low temperature (LT) ages and onshore basin deposition for Burdigalian (AFT and U/Th/He) and LT (mainly U-Th/He) together with the unconformity of the Langhian/Serravalian (Fig.11).

Figure 12

 12 Figure12presents the implications of these three stages of extension in the framework

Figure 1 /

 1 Figures Caption

Figure 2 /

 2 Figure 2/ Compilation of geochronological ages and of onshore Corsica basins (Saint Florent,

Figure 3 /

 3 Figure 3/ Tectonic map of Alpine Corsica with HP foliation trajectories (from our data shown

Figure 4 /

 4 Figure 4/ Major tectonic structures of Alpine Corsica, extracted from Figure 3.

Figure 5 /

 5 Figure 5/ N140° ductile fault zones: SW-NE cross-section in the East Tenda Shear Zone

Figure 6 /

 6 Figure 6/ N60°-70° fault zones in the Tenda massif (location in Fig. 4): A/ Detailed tectonic

Figure 7 .

 7 Figure 7. Structures and N60°-70° fault zones associated to the Bastia flexure in the Schistes

Figure 8 /

 8 Figure 8/ N-S fault zones in the Schistes Lustrés in the vicinity of San Nicolao (See location

Figure 9 / 3 Figure 10 /Figure 11 /FigFigure 12 /Figure 1 /

 931011121 Figure 9/ Simplified geological cross-section of the St Florent basin and its basement (Section

Figure 3 /

 3 Figure 3/ Tectonic map of Alpine Corsica with HP foliation trajectories (from our data shown in Stereoplot), major ductile and brittle deformation zones (N140° in grey; N60°-70° in red; N-S in blue). Detailed lithologies and names of Alpine nappe units (with numbers referring to units numbering in the main text) shown as a tectonic log.

Figure 6 /

 6 Figure 6/ N60°-70° fault zones in the Tenda massif (location in Fig. 4): A/ Detailed tectonic map of the ETSZ with N60°-70° trending normal fault zones and locations of cross-sections EE' (shown in Fig. 5) and FF' (shown in D/). B-C/ Stereoplots of foliations and faults measurements. D/ NNW-SSE cross-section (location FF' in A/) showing the rework of the ETSZ (N140 fault zone) by N60-70 fault zones. E/ Outcrop photographs (location in D/).

Figure 7 .

 7 Figure 7. Structures and N60°-70° fault zones associated to the Bastia flexure in the Schistes Lustrés. A/ Stereoplot of foliations measurements. B/ Detailed structural map of the N60°-70° Bastia flexure (See location in Fig. 4) with km-scale asymmetrical anticline (stereoplot of foliations in A) and N65° normal faults (stereoplot in C). D/ NNW-SSE cross-section (location FF' in B/) showing the deformation zone (flexure in light red) associated with N60-70 fault zones (see text for further details). E and F/ Outcrop photographs (location in D/).

Figure 8 /Figure 10 /Figure 11 /

 81011 Figure 8/ N-S fault zones in the Schistes Lustrés in the vicinity of San Nicolao (See location in Fig. 3). A/ Detailed structural map illustrating the change in foliation trends. B/ E-W crosssection (location HH' in A/) showing the deformation zone (flexure in light blue) associated with N-S fault zones (see text for further details). C/ outcrop photographs of steeply dipping foliations (location in B/).

Figure 12 /

 12 Figure 12/ Geodynamic significance of N140° ductile fault zones (left), N60°-70° ramp-flat extension (middle) and N-S fault zones (right) in the tectonic framework of the central Mediterranean and of the Apennines slab rollback (modified from Faccenna et al., 2004).