S Vitale

S Ciarcia

S Mazzoli

M N Zaghloul

Tectonic evolution of the 'Liguride' accretionary wedge in the Cilento area; southern Italy: a record of early Apennine

Keywords: subduction, superposed folding, synorogenic sedimentation, stratigraphic record, structural analysis, Apennine Orogen

The early stages of southern Apennine development have been unraveled by integrating the available stratigraphic record provided by synorogenic strata (of both foredeep and wedgetop basin environments) with new structural data on the Liguride accretionary wedge cropping out in the Cilento area, southern Italy. Our results indicate that the final oceanic subduction stages and early deformation of the distal part of the Apulian continental margin were controlled by dominant NW-SE shortening. Early Miocene subduction-accretion, subsequent wedge emplacement on top of the Apulian continental margin and onset of footwall imbrication involving detached Apulian continental margin carbonate successions were followed by extensional deformation of the previously 'obducted' accretionary wedge. Wedge thinning also enhanced the development of accommodation space, filled by the dominantly siliciclastic Cilento Group deposits. The accretionary wedge units and the unconformably overlying wedge-top basin sediments experienced renewed NW-SE shortening immediately following the deposition of the Cilento Group (reaching the early Tortonian), confirming that the preceding wedge thinning represented an episode of synorogenic extension occurring within the general framework of NW-SE convergence. The documented Early to the Late Miocene steps of southern Apennine development are clearly distinct with respect to the subsequent (late Tortonian-Quaternary) stages of fold and thrust belt evolution coeval with Tyrrhenian back-arc extension, which were characterized by NEdirected thrusting in the southern Apennines. 1 1. Introduction

A c c e p t e d M a n u s c r i p t 3 The southern Apennines are part of the peri-Mediterranean Alpine belt and result from the interaction between the converging Apulian and European plates since Late Cretaceous time (e.g. Mazzoli and Helman, 1994, and references therein). The related tectonic evolution involved the subduction of Tethyan oceanic lithosphere beneath the overriding Calabrian continental crust [START_REF] Bonardi | Calabria-Peloritani terrane and northern Ionian Sea[END_REF]. Following Early Miocene docking of the two continental margins, the subduction of oceanic lithosphere gave way to that of continental lithosphere [START_REF] Ranalli | Time dependence of negative buoyancy and the subduction of continental lithosphere[END_REF], which is also evinced by exhumed HP-LT rocks originally belonging to the distal part of the Apulian continental palaeomargin [START_REF] Iannace | The carbonate tectonic units of northern Calabria (Italy): A record of Apulian paleomargin evolution and Miocene convergence, continental crust subduction, and exhumation of HP-LT rocks[END_REF].

During the Early Miocene, the tectonic wedge formed by oceanic and transitional units (Liguride Units; [START_REF] Bonardi | Il Complesso Liguride Auct.: stato delle conoscenze e problemi aperti sulla sua evoluzione preappenninca ed i suoi rapporti con l'arco calabro[END_REF]'Internal' Units, Ciarcia et al., 2009;[START_REF] Vitale | Structural analysis of an Internal Unit of the southern Apennines (Cilento area, Italy): new constraints on the[END_REF] overthrusted the inner sector of the Apennine Platform [START_REF] Mostardini | Appennino centro meridionale. Sezioni geologiche e proposta di modello strutturale[END_REF]; Fig. 1). Subsequently, detached Mesozoic-Neogene sedimentary successions of the foreland (i.e. Apulian) plate were piled up eastward onto progressively outer domains, while sedimentation was occurring in both wedge-top and foredeep basins [START_REF] Bonardi | Carta delle principali Unità Cinematiche dell'Appennino meridionale[END_REF].

Remnants of the oldest part of the Apennine accretionary wedge, represented by the Liguride Units and associated Miocene wedge-top basin deposits, crop out extensively in the southern Apennines (Fig. 1). The aim of this paper is to analyze the structural setting and the tectonic evolution of the Liguride accretionary wedge, in order to investigate the first steps of the Apennine orogeny. A complete structural analysis is provided for the Liguride Units and associated wedge-top basin successions cropping out in Cilento (Fig. 1).

A c c e p t e d M a n u s c r i p t 4

The Liguride Units of the southern Apennines (Fig. 2) encompass the ophiolite-bearing Frido and Nord-Calabrese units [START_REF] Bonardi | Il Complesso Liguride Auct.: stato delle conoscenze e problemi aperti sulla sua evoluzione preappenninca ed i suoi rapporti con l'arco calabro[END_REF][START_REF] Bonardi | Calabria-Peloritani terrane and northern Ionian Sea[END_REF] as well as the Parasicilide and Sicilide units [START_REF] Ciarcia | Stratigraphy and tectonics of an Internal Unit of the southern Apennines: implications for the geodynamic evolution of the peri-Tyrrhenian mountain belt[END_REF]Vitale et al., 2010, and references therein), the latter two including basin successions probably deposited on thinned continental/transitional crust. Starting from the Early Miocene, all of these units were deformed and accreted into the Apennine tectonic wedge [START_REF] Ciarcia | Stratigraphy and tectonics of an Internal Unit of the southern Apennines: implications for the geodynamic evolution of the peri-Tyrrhenian mountain belt[END_REF][START_REF] Vitale | Structural analysis of an Internal Unit of the southern Apennines (Cilento area, Italy): new constraints on the[END_REF] and then unconformably overlain by wedge-top basin deposits of the Cilento Group [START_REF] Bonardi | Il Complesso Liguride Auct.: stato delle conoscenze e problemi aperti sulla sua evoluzione preappenninca ed i suoi rapporti con l'arco calabro[END_REF] and Monte Pruno Fm [START_REF] Ciarcia | Stratigraphy and tectonics of an Internal Unit of the southern Apennines: implications for the geodynamic evolution of the peri-Tyrrhenian mountain belt[END_REF]. In the Cilento, only the Parasicilide and Nord-Calabrese units crop out (Fig. 3a). The 'Internal' Units (i.e. the Liguride Units) tectonically overlie the 'External' Units that were derived from the deformation of sedimentary cover successions belonging to the Apulian continental margin (Fig. 3a). These comprise shallow-water and slope carbonates (Apennine Platform) and pelagic basin (Lagonegro Basin) successions (e.g. Mazzoli et al., 2008, and references therein). Lower-Middle and Upper Miocene wedge-top basin deposits occur on top of the tectonic pile (Fig. 2).

The Nord-Calabrese Unit includes Jurassic pillow lavas at the base, overlain by the Timpa delle Murge Fm (consisting of argillites, quartz-arenites, limestones and jaspers) and then by the Crete Nere and Saraceno fms. In the Cilento area, only the latter two formations occur.

The Crete Nere and Saraceno fms (Fig. 4) comprise a predominately siliciclastic and calciclastic succession deposited on oceanic crust [START_REF] Bonardi | Il Complesso Liguride Auct.: stato delle conoscenze e problemi aperti sulla sua evoluzione preappenninca ed i suoi rapporti con l'arco calabro[END_REF] during plate convergence. The Crete Nere Fm is formed, from bottom to top, by a thick succession of black shales with intercalation of arenites, dark-brownish argillites and arenites in the middle part, and calcareous beds in the upper part. The middle-upper part of this formation has been dated as Middle Eocene; however the undated lower part could be as old as Late Jurassic, as suggested by [START_REF] Bonardi | Il Complesso Liguride Auct.: stato delle conoscenze e problemi aperti sulla sua evoluzione preappenninca ed i suoi rapporti con l'arco calabro[END_REF]. The Crete Nere Fm stratigraphically passes A c c e p t e d M a n u s c r i p t 5 upwards to the Saraceno Fm, which is characterized by calciclastic, locally silicified turbidites (Punta Telegrafo Member) at the base, followed by marls, pelites and arenites in the middle part and finally by sandstones of the Sovereto Member [START_REF] Bonardi | Carta delle principali Unità Cinematiche dell'Appennino meridionale[END_REF]. The uppermost part of the Saraceno Fm has been dated as Aquitanian-Burdigalian [START_REF] Bonardi | Carta delle principali Unità Cinematiche dell'Appennino meridionale[END_REF].

The Parasicilide Unit [START_REF] Bonardi | Geotraverse across the Calabria-Peloritani Terrane (southern Italy). Field Trip Guide Books[END_REF][START_REF] Ciarcia | Stratigraphy and tectonics of an Internal Unit of the southern Apennines: implications for the geodynamic evolution of the peri-Tyrrhenian mountain belt[END_REF][START_REF] Vitale | Structural analysis of an Internal Unit of the southern Apennines (Cilento area, Italy): new constraints on the[END_REF] cropping out in Cilento and corresponding to the Castelnuovo Cilento Unit of [START_REF] Cammarosano | Il substrato del Gruppo del Cilento tra il M. Vesalo e il M. Sacro (Cilento, Appennino Meridionale)[END_REF][START_REF] Cammarosano | Nuovi dati sui flysch del Cilento (Appennino meridionale, Italia)[END_REF], comprises both pre-orogenic and foredeep basin deposits (Fig. 4) grouped into four formations (from bottom to top): (i) micaceous sandstones, varicolored clays and slates of the Postiglione Fm; (ii) marls and limestones of the Monte Sant'Arcangelo Fm; (iii) whitish marls and marly limestones of the Contursi Fm; and (iv) foredeep sandstones of the Arenarie di Albanella Fm [START_REF] Donzelli | Lembi di Flysch oligocenico affiorante a SE della Piana del Sele[END_REF]. Due to intense folding, the original thickness of the whole succession can only be approximately estimated as exceeding 800-1000 meters. The dated portions of the succession range in age between Middle Eocene and Burdigalian; however, the lower undated deposits could be as old as Late Cretaceous [START_REF] Bonardi | Il Complesso Liguride Auct.: stato delle conoscenze e problemi aperti sulla sua evoluzione preappenninca ed i suoi rapporti con l'arco calabro[END_REF][START_REF] Guerrera | Tectono-sedimentary evolution of the southern branch of the Western Tethys (Maghrebian Flysch Basin and Lucanian Ocean): consequences for Western Mediterranean geodynamics[END_REF].

The Cilento Group, whose age ranges from the Burdigalian/Langhian boundary [START_REF] Bonardi | Il Complesso Liguride Auct.: stato delle conoscenze e problemi aperti sulla sua evoluzione preappenninca ed i suoi rapporti con l'arco calabro[END_REF] to the lower Tortonian [START_REF] Russo | Alcune precisazioni stratigrafiche sul Flysch del Cilento (Appennino meridionale)[END_REF], is formed by arenitic and marly deposits (Fig. 4) of the Pollica and San Mauro fms [START_REF] Ietto | Il flysch mesozoico-terziario del Cilento occidentale[END_REF] laterally passing southward to conglomeratic, arenitic and marly deposits of the Torrente Bruca Fm [START_REF] Bonardi | Il Complesso Liguride Auct.: stato delle conoscenze e problemi aperti sulla sua evoluzione preappenninca ed i suoi rapporti con l'arco calabro[END_REF]. The Pollica Fm is formed by a thin-bedded succession of sandstones and pelites in the lower part (Cannicchio Sandstones Member), passing to a thin-to medium-bedded succession of sandstones, conglomerates, marls and pelites in the middle-upper part. The overlying San Mauro Fm is characterized by a medium-to thick-bedded succession of marls A c c e p t e d M a n u s c r i p t 6 and conglomerates. In the Lucania region, to the east, these formations correspond to the undifferentiated succession of the Albidona Fm [START_REF] Selli | Il Paleogene nel quadro della geologia dell'Italia meridionale[END_REF]. These deposits and the underlying units are covered unconformably by younger (Upper Miocene) coarse-grained wedge-top basin successions including: (i) the Castelvetere Fm (Pescatore et al., 1970), (ii) the Monte Sacro Fm [START_REF] Selli | Il Paleogene nel quadro della geologia dell'Italia meridionale[END_REF], and (iii) the Oriolo [START_REF] Selli | Il Paleogene nel quadro della geologia dell'Italia meridionale[END_REF], Serra Manganile [START_REF] Ghezzi | Uno studio del flysch nella regione calabro-lucana. Stratigrafia, tettonica e nuove idee sul Miocene dell'Appennino meridionale[END_REF] and Gorgoglione [START_REF] Selli | Il Paleogene nel quadro della geologia dell'Italia meridionale[END_REF] Fms, cropping out in the Sele River Valley,Cilento and Lucania,respectively (Figs. 1,2,3a,4).

The Nord-Calabrese Unit is generally tectonically superposed onto the Parasicilide Unit (e.g.

Alento and Lambro River Valleys, Fig. 3a). However, in the Sapri area it lies directly over the carbonates of the Apennine Platform, whereas northeastward of Cicerale-Monte Centaurino, this unit does not crop out (e.g. Torrente Pietra and Sele River Valleys Fig. 3a).

The Cilento Group unconformably covers the already deformed and imbricated Nord-Calabrese and Parasicilide units. This feature is shown in the geological map (Fig. 3a) and in cross section X-X' (Fig. 3b): the Cilento Group seals the Crete Nere and Saraceno fms (Nord-Calabrese Unit) in the Alento River Valley, west of the Lambro River and in the Sapri area, whereas it covers the Parasicilide Unit (located in the footwall to the Nord-Calabrese Unit) between Monte Sacro and Monte Centaurino and in the northeastern area, between the villages of Magliano Nuovo and Cicerale. The Crete Nere Fm is characterized by the superposition of three fold sets (F 1 NC , F 2 NC and F 3 NC ) and associated planar and linear structures. The main foliation in pelitic layers is a slaty cleavage (S 1 NC ) sub-parallel to F 1 NC fold axial planes (AP 1 NC ), whereas in the competent arenitic beds a spaced, disjunctive cleavage is present. F 1 NC folds display geometries ranging from tight to isoclinal (Fig. 5a). Fold shape alternates between classes 1c and 3 of [START_REF] Ramsay | Folding and fracturing of rocks[END_REF] Orria Syncline, as it is exposed around the Orria village; Fig. 3a) and related parasitic folds F 3 NC deform this succession in the NE sector of the study area, whereas rare meso-scale F 3 NC folds occur elsewhere.

Orientation data for the main structures exposed between Pisciotta Marina and Pioppi (Fig. 3a) are shown in Fig. 6. Bedding and (S 1 NC ) foliation poles (Figs. 6a,f) form two girdles providing theoretical (  and   ) fold axes plunging 055/07 and 065/16, respectively. (The latter value, obtained from folded S 1 NC , is related to second-phase folds). F 1 NC and F 2 NC folds are about coaxial: mesoscopic fold hinges A 1 NC (Fig. 6b) show a mean plunge of 051/19 and mesoscopic fold hinges A 2 NC (Fig. 6g) form a cluster around the mean value of 064/12 whereas in the Pioppi area A 1 NC data (Fig. 6c) define a girdle. The crenulation lineation (L 2 NC ) is parallel to A 2 NC fold hinges (Fig. 6h), to which is clearly related, and displays a mean plunge of 066/12. The axial planes AP 1 NC of F 1 NC folds are dipping mainly to the SE (Fig. 6d) in the Pisciotta Marina area, whereas in the Pioppi area they are scattered (Fig. 6e). The axial A c c e p t e d M a n u s c r i p t planes AP 2 NC of F 2 NC folds dip both to the NW and SE in the Pisciotta Marina area (Fig. 6i).

Poles to the associated crenulation cleavage (S 2 NC ) form two clusters including both moderately SSE dipping and NNW gently dipping sets (Fig. 6j).

The third fold set (F 3 NC ) is well-exposed in the Pioppi area. A 3 NC fold hinges (Fig. 6k) cluster around a mean value of 301/19, while fold axial planes are dominantly NE to SW dipping (Fig. 6l).

3 . 2 3 . 2 S a r a c e n o F m .

Structural analysis on the Saraceno Fm has been carried out separately for the peliticcalcareous lower part (Punta Telegrafo Member) and for the arenitic-marly middle-upper portion. The analyzed lower part of the formation crops out at Pisciotta Marina, Punta

Telegrafo and Torre di Caleo (Fig. 3a). The Punta Telegrafo Member is characterized by the superposition of two meso-scale fold sets F 1 NC and F 2 NC (Fig. 5b). F 1 NC folds show tight to isoclinal geometries, with shapes ranging from chevron, rounded and box types (Fig. 5b).

Generally F 1 NC folds in pelitic rocks are of class 3 of [START_REF] Ramsay | Folding and fracturing of rocks[END_REF], whereas they are of class 1c for calcareous and arenitic layers. Second-phase folds (F 2 NC ) include open to tight folds (Fig. 5b) that are locally intensely developed (Fig. 5d). Variably developed cleavages are associated with the two fold sets. In the pelites, the first foliation (S 1 NC ) is a roughly axial planar slaty cleavage (involving total or partial transposition), whereas the second foliation (S 2 NC ) is a crenulation cleavage (Fig. 5c) to which a crenulation lineation (L 2 NC ) is also associated. Late, open F 3 NC folds refold this part of succession.

Complex vein arrays affect the whole calcareous succession, especially at Punta Telegrafo site (Fig. 5f). Most of the veins are orthogonal to F 1 NC fold hinges or form conjugate sets,

A c c e p t e d M a n u s c r i p t 9 often in the form of en-echelon vein arrays, both indicating extension parallel to the fold axis A 1 NC . Veins parallel to A 1 NC also occur, producing a characteristic chocolate tablet boudinage (Fig. 5f). Locally, especially in the isoclinal fold limbs, intense stretching occurs in the form of conjugate ductile shear zones (Fig. 5e) or as asymmetric boudinage (Fig. 5g). Extension veins orthogonal to F 2 NC fold hinges also occur, although they are less common. For both folding events, fold amplification was preceded by homogeneous shortening (bedding-parallel shortening for the first event), expressed by local thrust faults characterized by minor displacements (pre-buckle thrusts; [START_REF] Price | Analysis of geological structures[END_REF]. Often the second shortening affects previously boudinaged layers (Fig. 5h). The interference pattern developed by the superposition of F 1 NC and F 2 NC fold sets is of intermediate 2-3 type of [START_REF] Ramsay | Folding and fracturing of rocks[END_REF] classification (Fig. 5b), F 2 NC fold hinges forming a generally low angle with F 1 NC fold axes.

Nearly coaxial refolding is recorded by the distribution of bedding attitudes, the composite structures resulting from fold superposition maintaining an overall sub-cylindrical geometry.

Poles to S 0 NC form girdles (Fig. 7a,b) indicating theoretical (  ) fold axes of 064/09 (Punta Telegrafo) and 231/21 (Torre di Caleo). Poles to S 1 NC (Fig. 7g) are also distributed around a great circle whose pole plunges 237/06, this value representing the theoretical (  ) fold axis for the second-phase fold set. First-phase fold hinges (A 1 NC ) are scattered (Fig. 7c,e).

However, the related axial planes (AP 1 NC ) dip mainly to the NW and SE (Fig. 7d,f).

Conversely, second-phase fold hinges (A 2 NC ) form a subhorizontal cluster (Fig. 7h,k,m) with mean plunges of 037/06 (Pisciotta Marina), 042/00 (Punta Telegrafo) and 066/12 (Torre di Caleo). The related fold axial planes (AP 2 NC ) dip mainly to the NW and SE (Fig. 7j, l, n). A crenulation cleavage (S 2 NC ) and a crenulation lineation (L 2 NC ) are associated with secondphase folds. S 2 NC surfaces tend to dip either moderately to the NW or gently to the SE (Fig. 7o), whereas lineations L 2 NC form a cluster with a mean plunge of 248/04 (Fig. 7i). planes are also scattered (Fig. 7q,r). The related cleavage (S 1 NC ) dips mainly to the NW and SE (Fig. 7s). F 2 NC fold hinges plunge mainly to the NNE and S/WSW (Fig. 7t). F 2 NC fold axial planes are mainly gently dipping to sub-horizontal (Fig. 7u), similarly to the related crenulation cleavage S 2 NC (Fig. 7v). As for the lower part of the formation, also here interference patterns between F 1 NC and F 2 NC folds are of intermediate type between types 2 and 3 of [START_REF] Ramsay | Folding and fracturing of rocks[END_REF] classification (Fig. 8a,b). F 3 NC folds generally display open to tight shapes, with dominantly W-E trending hinges (Fig. 7w) and axial planes dipping mainly to the S and secondarily to the N (Fig. 7x). The previously mentioned Orria Syncline, representing a regional F 3 NC structure, involves also the Saraceno Fm in the NE part of the study area. dipping pre-buckle thrusts showing minor displacements (Fig. 8d). Minor thrust faults occur also in fold hinge regions to accommodate shortening in thinner layers (Fig. 8c, inset). In the Omignano area (Fig. 3a) the whole succession is deformed by a SE verging, overturned macro-scale F 1 CG fold and associated parasitic structures. In the area between Omignano, Pollica and Ogliastro, F 1 CG fold hinges of both meso-and macro-scale folds show a general NE-SW trend. A spaced, disjunctive cleavage (S 1 CG ) is associated with these folds.

Conversely, in the Orria, Gioi and Cardile areas the whole succession of the Cilento Group is deformed by the SW-S verging regional Orria Syncline (Zuppetta and Mazzoli, 1997), which represents a F 1 CG structure in terms of the Cilento Group deformation. regions is often accommodated by thrust faults or by cataclasis producing intense brecciation (Fig. 8f). Also in this part of the succession, pre-buckle thrusts commonly affect single stiff layers (Fig. 8g,h,i). In the Omignano area (Fig. 3a) minor parasitic folds are related to the previously mentioned overturned, SE verging major F 1 CG fold. The middleupper part of the Pollica Fm is also deformed by the previously mentioned regional fold and associated S-SW verging parasitic folds in the Orria-Gioi area.

Poles to bedding distributions (Fig. 9i-n Poles to bedding (Fig. 9s-u) indicate gentle folding in the Omignano area (Fig. 9s), whereas in the Orria-Piano Vetrale and Gioi-Cardile areas they form girdles (Fig. 9t,u) providing theoretical (  ) fold axes plunging 286/01 and 127/04, respectively (these being related to the regional Orria Syncline). Fold hinges are scattered (Fig. 9v), whereas fold axial planes dip mainly to the NNE and SSW (Fig. 9w).

5. Discussion

The Burdigalian time and subsequent deformation within the wedge [START_REF] Vitale | Structural analysis of an Internal Unit of the southern Apennines (Cilento area, Italy): new constraints on the[END_REF]. Like the Nord-Calabrese Unit, the Parasicilide succession is also deformed, in the NE part of the study area, by the regional (F 3 PS ) Orria Syncline.

A late, extensional origin of the contacts between the Nord-Calabrese and Parasicilide Units is suggested by the geometry of the tectonic contact in the Castelnuovo Cilento tectonic window (Fig. 3a, cross sections of Fig. 3b), which dramatically cuts all folds in both footwall and hanging-wall units [START_REF] Vitale | Structural analysis of an Internal Unit of the southern Apennines (Cilento area, Italy): new constraints on the[END_REF], as well as in the Sapri area, where the Nord-Calabrese Unit directly overlies the Apennine Platform succession with the tectonic omission of the Parasicilide Unit and part of the Crete Nere Fm. The simple restoration provided in Fig. 10 shows the proposed interpretation for the development of the present structural geometry as well as of wedge-top basin depocentres filled by the Cilento Group deposits.

The horizontal extension producing the two major low-angle normal faults shown in Fig. 10 is probably associated with previous wedge overthickening, as a result of thrusting of the Nord-Calabrese Unit onto the Parasicilide Unit, as well as with large-scale warping and uplift of the wedge related to footwall imbrication within the underlying Apennine Platform shallow-water to slope carbonates [START_REF] Vitale | Structural analysis of an Internal Unit of the southern Apennines (Cilento area, Italy): new constraints on the[END_REF]. Probably the accretionary wedge collapsed as it exceeded the critical taper, leading to the development of extensional detachments dipping toward the foreland. This processes, together with accretion of new material at the wedge toe, allowed the slope surface angle to decrease.

The tectonic contact between the Nord-Calabrese Unit and the Parasicilide Unit is gently folded by broad NE-SW trending antiforms, probably related to footwall imbrication as shown in the geological section X-X' in Fig. 3(b). This suggests that thrusting involving the Apennine Platform succession and wedge collapse were roughly coeval. Probably part of the Parasicilide units are all deformed by the regional Orria Syncline (Fig. 3a). This major fold is accompanied by a system of S-SW overturned parasitic folds (cross section Y-Y' in Fig. 3b).

The   -axes obtained from the poles to bedding measured in the Pollica and San Mauro Fms from different areas (Fig. 9c, m, n, t, u) point out an overall curved fold hinge for the regional In order to obtain a synoptic view of the fold trends in the whole study area, mesoscopic fold axis trends (both for the Liguride Units and the Cilento Group) are plotted in the geological map of Fig. 3a. It is worth noting that a broad homogeneity in fold axis trends exists for the Liguride Units (F NC 1-2-3 , F PS 1-2-3 ) and for the Cilento Group (F CG 1 ). The rough coaxiality between the first fold set (F CG 1 ) in the Cilento Group and F NC 1-2-3 and F PS 1-2-3 fold sets in the Nord-Calabrese and Parasicilide Units suggests a more or less constant orientation of regional shortening for these deformation stages.

Although asymmetric folds and kinematic features associated with thrust faults indicate both NW and SE vergences, it is reasonable to suppose a main SE/E tectonic transport for these units according to Miocene kinematic reconstructions proposed by several authors (e.g. Vignaroli et al., 2009 and references therein). This is consistent with the SE vergence of firstphase isoclinal folds in the Parasicilide Unit exposed in the tectonic window of Castelnuovo Cilento (Fig. 3a; [START_REF] Vitale | Structural analysis of an Internal Unit of the southern Apennines (Cilento area, Italy): new constraints on the[END_REF], as well as with top-to-the-ESE kinematics unraveled by [START_REF] Vitale | Finite strain analysis of a natural ductile shear zone in limestones: insights into 3-D coaxial vs. non-coaxial deformation partitioning[END_REF] for carbonate thrust sheets originally forming part of the Apennine Platform in the Calabria-Lucania border area [START_REF] Iannace | The carbonate tectonic units of northern Calabria (Italy): A record of Apulian paleomargin evolution and Miocene convergence, continental crust subduction, and exhumation of HP-LT rocks[END_REF]. Major differences in deformation styles occur between the Liguride Units and the Cilento Group. The Liguride Units show pervasive deformation, whereas the Cilento Group is characterized by locally disharmonic folding and variable fold geometries. Increasing fold wavelength from the bottom to the top of the Cilento succession is probably related to general coarsening and thickening upward (from the thin strata of the Cannicchio Sandstones Member to the meterscale strata of the San Mauro Fm).

A c c e p t e d M a n u s c r i p t 18

The Cilento Group was deposited on an already deformed substratum consisting of the Nord-Calabrese and Parasicilide units. Therefore, the first two deformation events involving the latter two units occurred during the Burdigalian, being bracketed by the age of the Cannicchio Member (Burdigalian-Langhian boundary) and the age of the youngest deposits (Arenarie di Albanella Fm, Burdigalian) of the Parasicilide Unit. On the other hand, as suggested by Zuppetta and Mazzoli (1997), based on the analysis of the Orria Syncline and related parasitic structures, deformation of the Cilento Group immediately postdated the deposition of the youngest strata of San Mauro Fm (lower Tortonian according to [START_REF] Russo | Alcune precisazioni stratigrafiche sul Flysch del Cilento (Appennino meridionale)[END_REF]. Deformation stages for the various analyzed successions, their interpreted correlation and chronology are summarized in Table 1.

In order to summarize the present results, a geodynamic evolutionary sketch for the southern Apennine accretionary wedge between the Aquitanian-Burdigalian boundary and the post-lower Tortonian is provided in Fig. 11. In the first stage (Fig. 11a) the Nord-Calabrese succession is covered by the foredeep deposits of the Saraceno Fm (sandstones).

Subsequently, this unit is incorporated into the accretionary wedge and deformed by overall to the development of scattered folds (Fig. 11h).

6. Conclusions

The integration of available stratigraphic information with new structural data from the various tectonic units exposed in the Cilento area of the southern Apennines has allowed a comprehensive picture of the tectonic evolution of the Liguride accretionary wedge in this area to be obtained. The documented structural data point out that final oceanic subduction stages and early involvement in the deformation of the distal part of the Apulian continental margin were characterized by a broad NW-SE shortening. This, being consistent with recent plate kinematic reconstructions for the Western Mediterranean in Early Miocene times [START_REF] Schettino | Plate kinematics of the Western Mediterranean region during the Oligocene and Early Miocene[END_REF], is completely unrelated with NE-directed thrusting

Figure captions

Fig. 1. Tectonic sketch map of the southern Apennines (after Bonardi et al., 2009, modified).

Inset shows thrust front of the peri-Tyrrhenian mountain belt.

  A c c e p t e d M a n u s c r i p t 10 The middle-upper part of the Saraceno Fm is characterized by structures similar to those described for the lower part, although F 3 NC folds become more abundant. As for the Punta Telegrafo Member, this part of the succession is characterized by three fold sets: F 1 NC , F 2 NC and F 3 NC . Generally F 1 NC folds are tight to isoclinal and show variable geometries with chevron to rounded shapes, whereas F 2 NC folds are more open (Fig. 8a, b). Poles to bedding are scattered (Fig. 7p) with dominant NW and SE dip directions. F 1 NC fold hinges and axial

4 4 .

 4 Structural analysis of the Cilento GroupIn order to unravel possible stratigraphic controls on structural development and to analyze the role of bed-thickness on folding style, (i) the lower part (Cannicchio Sandstones Member) of the Pollica Fm, (ii) the middle-upper part of the Pollica Fm, and (iii) the San Mauro Fm have been analyzed separately. The analyzed outcrops are localized around the Pollica, Omignano, Orria, Gioi, Salento and Catona villages (Fig.3a).

  1 L o w e r p a r t o f t h e P o l l i c a F m : C a n n i c c h i o S a n d s t o n e s M e m b e r Several outcrops of the Cannicchio Sandstones Member have been analyzed, particularly in the Cannicchio type-locality (close to the Pollica village; Fig. 3a). In this area the succession is characterized by (F 1 CG ) folds showing kink and chevron shapes (fig 8c), and subordinate rounded or box geometries. These folds are often detached along pelitic layers (Fig. 8c) forming SE verging asymmetric fold trains characterized by overturned short limbs. It is common to find stiff beds sandwiched between pelitic layers and shortened by NW or SE

Figure 9 (

 9 Figure 9 (a to h) shows orientation data for the main analyzed structures. Poles of bedding

  i d d l e -u p p e r p a r t o f t h e P o l l i c a F m Meso-scale F 1 CG folds are generally asymmetric and show geometries ranging from open to tight, with chevron, rounded, box and kink shapes (Fig. 8e, f). Deformation in fold hinge

  ) provide theoretical (  ) fold axes plunging 068/19 (Ogliastro-Agnone), 208/22 (Pollica), 261/16 (Catona), 045/10 (Omignano), 255/02 (Orria-Piano Vetrale), and 322/03 (Gioi-Cardile). F 1 CG fold hinge lines (Fig.9o, p) display mean plunges of 069/09 (Ogliastro-Agnone) and 028/10 (Omignano), whereas fold axial planes dip mainly to the SE in the Ogliastro-Agnone area (Fig.9q) and both to SE and NW in the Omignano area (Fig.9r).4 . 3 4 . 3 S a n M a u r o F mThe San Mauro Fm crops out mainly in the N and NE sectors of the study area. In the former it shows only gentle F 1 CG folds, whereas in the latter it is deformed by the previously mentioned regional F 1 CG fold and associated open to tight parasitic folds with steep to gently dipping axial planes and fold vergence ranging between SE and SW. In this formation, overturned limbs only locally (Cardile and Gioi villages) and display larger wavelengths with respect to F 1 CG folds in the underlying Pollica Fm.

  Crete Nere and Saraceno fms, forming the Nord-Calabrese Unit, show similar polyphase deformation almost coaxial geometry of the first two fold sets and the limited temporal range in which they must have occurred suggests that the two folding events developed as part of a progressive deformation event characterized by roughly NW-SE shortening. Initial layerparallel shortening during the D NC 1 deformation stage produced mesoscopic thrust faults showing minor displacements (pre-buckle thrusts). Subsequent fold amplification led to the development of dominantly isoclinal folds (F 1 NC ). This process was accompanied, especially in the calcareous beds (lower part of the Saraceno Fm), by boudinage and formation of enechelon vein arrays. Boudinage is intensely developed at the transition between the Crete Nere and Saraceno Fms, where the strata are often completely disrupted by conjugate extensional shear zones. Widespread veining reveals significant fluid localization at this level of the succession, a process probably controlled by the stratigraphic boundary between the low permeable shales and slates of the Crete Nere Fm and the high permeable limestones A c c e p t e d M a n u s c r i p t 14 forming the lower part of the Saraceno Fm. Veins, boudins and conjugate shear zones indicate extension along both the maximum (X) and intermediate (Y) axes of the bulk finite strain ellipsoid (i.e. oblate strain). Furthermore the occurrence of stretched isoclinal folds (intrafolial folds) and shortened boudins strengthens the hypothesis of progressive deformation. The layers were first shortened (by buckling) and then, as fold limbs came to lie roughly parallel to the maximum extension direction as a result of isoclinal folding, they were stretched, leading to the development of intrafolial folds. Such previously lengthened fold limbs, characterized by boudinage of the stiff layers, were subsequently shortened (locally developing 'folded boudins'; Ramsay and Huber, 1983) during the second deformation stage. This (D NC 2 ) is characterized by tight to open (F 2 NC ) folds, verging mainly to the SE and subordinately to the NW. The almost coaxial geometry of F 1 NC and F 2 NC fold sets, evident for the Crete Nere Fm and the lower part of the Saraceno Fm, is less consistent for the middle-upper part of the Saraceno Fm, resulting in interference patterns ranging between types 2 and 3 of Ramsay (1967). The third deformation stage (D NC 3 ) is characterized by the local development of meso-and macro-scale F 3 NC folds (such as in the Pisciotta-Ascea and Orria areas, Fig. 3a) displaying open to tight geometries. The structural evolution unraveled for the Crete Nere and Saraceno fms is comparable with that of the Parasicilide Unit cropping out in Cilento and forming, together with the Nord-Calabrese Unit, the Liguride Units in this area. The Parasicilide Unit, located in the footwall to the Nord-Calabrese Unit, is also characterized by superposed deformations (Vitale et al., 2010): F 1 PS isoclinal folds, related to a first deformation stage (D PS 1 ), are refolded by close F 2 PS folds developed in the form of a regional recumbent fold verging to the SE and associated parasitic folds (D PS 2 ). A third deformation event (D PS 3 ) produced open F 3 PS folds displaying horizontal axial planes, developed only in the steep to vertical F 2 PS limbs. The first two A c c e p t e d M a n u s c r i p t deformation stages are related to the accretion of this succession into the tectonic wedge in

  succession (Monte Bulgheria; Fig.3a) was exposed already in Middle Miocene time, feeding the Cilento Group with calcareous fine-grained sediments (San Mauro Fm). In this case, the tectonic window of Castelnuovo Cilento (Alento Valley; Fig.3a) may be interpreted as a breached anticline related to thrusting in the underlying Apennine Platform succession. The deformation of the Cilento Group succession, unconformably overlying the previous units, is characterized by a roughly NW-SE oriented shortening (D CG 1 ) expressed by prebuckle thrusts, reverse faults and asymmetric folds characterized by a main vergence toward the SE and secondarily toward the NW, S and SW. These F 1 CG folds generally range from tight to open and show kink geometries. Folding occurred at very low-T conditions, as evidenced by brittle deformation associated with tight folds. In the NE sector of the study area, the successions belonging to the Cilento Group and the underlying Nord-Calabrese and

  fold. Statistical (   fold axes plunge from 248/01 (Cannicchio Member), to 255/02 (Middleupper part of Pollica Fm), to 286/01 (San Mauro Fm) in the Orria area, to 322/05 (Middleupper part of Pollica Fm) and 127/04 (San Mauro Fm) in the Gioi area. According to Zuppetta and Mazzoli (1997), the general lack of cleavage development and of grain-scale deformation associated with the Orria Syncline is indicative of large-scale folding occurring in not completely lithified sediments. Based on this evidence, the authors suggested an early (syndiagenetic) origin for this fold, involving the Cilento Group sediments immediately following their deposition. Deformation involving non-completely lithified sediments within A c c e p t e d M a n u s c r i p t the general framework of thrusting and associated non-coaxial strain may have enhanced non-cylindrical folding.

  NW-SE shortening (D NC 1 ) developing isoclinal F NC 1 folds (Fig. 11b). During this stage foredeep sedimentation occurs on top of the Parasicilide domain with the deposition of the sandstones of the Arenarie di Albanella Fm. In Burdigalian time (Fig. 11c, d), the Nord-Calabrese Unit experiences continued NW-SE shortening (D NC 2 ) and the Parasicilide Unit is accreted into the wedge with the development of F (Fig. 11d), the inner sector of the Apennine Platform carbonate domain is overlain by the accretionary wedge, while sedimentation of the Bifurto Fm occurs in the newly developed foredeep. Later (Fig. 11e, f), the accretionary wedge undergoes horizontal stretching and vertical shortening, probably due to previous overthickening and to A c c e p t e d M a n u s c r i p t footwall imbrication in the underlying Apennine Platform carbonate succession, producing bending and uplift of the Liguride Units. Low-angle extensional detachments associated with synorogenic extension favor the development of accommodation space in wedge-top basin depocentres (Fig.11f) that are filled by the Cilento Group deposits (Fig.11g). Subsequent to the final (early Tortonian) deposition of San Mauro Fm, the whole tectonic pile -including the Nord-Calabrese and Parasicilide Units, as well as the Cilento Group -experiences renewed, though moderate, roughly NW-SE oriented shortening (

  characterizing the Apennine fold and thrust belt during later (late Tortonian to Quaternary) development of the Apennine-Calabrian-Sicilian arcuate orogen and associated opening of the Tyrrhenian Sea back-arc basin (e.g.Johnston and Mazzoli, 2009, and references therein).The progressive development of the accretionary wedge in Miocene times is marked by synorogenic sedimentation both in the trench and in wedge-top basins. Major overthrusting A c c e p t e d M a n u s c r i p t 20 of Liguride Units, wedge overthickening and subsequent emplacement ('obduction') on top of the Apulian continental palaeomargin were followed by wedge collapse. This was probably coeval with -and partly related to -incipient footwall imbrication within underlying Apennine Platform carbonates. Late deformation of the accretionary wedge, post-dating deposition of the Cilento Group wedge-top basin sediments (ending in the earliest Tortonian), was controlled by renewed more or less NW-SE oriented shortening, thus confirming that the previous wedge thinning episode took place within the general framework of plate convergence. The results, shedding new light into the Miocene tectonic evolution of the southern Apennine accretionary wedge, provide new insights into the early stages of southern Apennines development. This will hopefully contribute to a better understanding of a critical stage of Apennine geodynamics, involving the transition from the subduction of oceanic lithosphere to that of continental lithosphere, prior to the development of the intensely studied NE-directed Apennine foreland fold and thrust belt.

  the Miocene Apennine accretionary wedge. Comptes Rendus Geosciences, doi: 10.1016/j.crte.2010.03.005. Zuppetta, A., Mazzoli, S., 1997. Deformation history of a synorogenic sedimentary wedge, northern Cilento area southern Apennines thrust and fold belt, Italy. Geological Society of America Bulletin, 109, 698-708.

Fig. 2 .

 2 Fig. 2. Sketch showing tectonic and stratigraphic relationships between Liguride Units and

Fig. 3 .

 3 Fig. 3. (a) Geological sketch map of the Cilento area, showing all analyzed outcrop locations;

Fig. 4 .

 4 Fig. 4. Sketch showing stratigraphic relationships for the Nord-Calabrese and Parasicilide

Fig. 5 .

 5 Fig. 5. Examples of outcrop features in the Crete Nere Fm (a) and in the lower part of the Saraceno Fm (b) to (h). (a) Interference pattern between isoclinal F 1 NC and close F 2 NC folds (Torre di Caleo-Pioppi). (b) Interference pattern between isoclinal F 1 NC and open F 2 NC folds (Punta Telegrafo). (c) Crenulation cleavage (S 2 NC ) deforming preexisting pervasive foliation

Fig. 6 .

 6 Fig. 6. Lower hemisphere, equal-area projections showing orientation data for measured

Fig. 7 .

 7 Fig. 7. Lower hemisphere, equal-area projections showing orientation data for measured

Fig. 8 .

 8 Fig. 8. Examples of outcrop features in the Saraceno and Pollica Fms. Interference between isoclinal F 1 NC folds and close F 2 NC folds, middle part of the Saraceno Fm: (a) Torre di Caleo; (b) Ascea-Pisciotta. (c) F 1 CG detachment fold in the Cannicchio Sandstones Member, showing

Fig. 9 .

 9 Fig. 9. Lower hemisphere, equal-area projections showing orientation data for measured

Fig. 10 .Fig. 11 .

 1011 Fig. 10. Tectonic model showing present-day geometric relationships among the studied

  Figure01

Figure03A

  Figure03

Figure04A

  Figure04

Figure05A

  Figure05

Figure06A

  Figure06

Figure07A

  Figure07

Figure08A

  Figure08

Figure09A

  Figure09

Figure11

  Figure11

Table caption Table 1 .

 caption1 Correlation among deformation stages for the studied successions and related chronology.

Acknowledgements

Thorough review by Agustin Martin-Algarra and useful comments by JG Editor Randell

Stephenson allowed us to substantially improve the paper. We are grateful to Glauco Bonardi for the innumerable and invaluable discussions.

. 1 R e f e r e n c e s

Amore, O., Bonardi, G., Ciampo, G., De Capoa, P., Perrone, V., Sgrosso, I., 1988. Relazioni tra "flysch interni" e domini appenninici: reinterpretazione delle formazioni di Pollica, San