journal of geodynamics · 20 t. dumont et al. / journal of geodynamics 56–57 (2012) 18–38 fig....

SA

TI

a

ARRAA

KWCCFW

1

acTS

0d

Journal of Geodynamics 56– 57 (2012) 18– 38

Contents lists available at SciVerse ScienceDirect

Journal of Geodynamics

jo u r n al hom epage : ht tp : / /www.e lsev ier .com/ locate / jog

tructural and sedimentary records of the Oligocene revolution in the Westernlpine arc

. Dumont ∗, S. Schwartz, S. Guillot, T. Simon-Labric, P. Tricart, S. JourdanSTerre, CNRS & Université de Grenoble I, Maison des Géosciences, 1381 rue de la Piscine, BP53, 38041 Grenoble Cedex 9, France

r t i c l e i n f o

rticle history:eceived 23 February 2011eceived in revised form 12 October 2011ccepted 10 November 2011vailable online 20 November 2011

eywords:estern Alps

ontinental subductionollisionoreland basinsestward escape

a b s t r a c t

The northwestwards-directed Eocene propagation of the Western Alpine orogen is linked with (1) com-pressional structures in the basement and the Mesozoic sedimentary cover of the European foreland,well preserved in the External Zone (or Dauphiné Zone) of the Western Alps and (2) tectono-sedimentaryfeatures associated with the displacement of the early Tertiary foreland basin. Three major shorteningepisodes are identified: a pre-Priabonian deformation D1 (N-S shortening), supposedly linked with thePyrenean-Provence orogeny, and two Alpine shortening events D2 (N- to NW-directed) and D3 (W-directed). The change from D2 to D3, which occurred during early Oligocene time in the Dauphiné zone,is demonstrated by a high obliquity between the trends of the D3 folds and thrusts, which follow thearcuate orogen, and of the D2 structures which are crosscut by them. This change is also recorded in theevolution of the Alpine foreland basins: the flexural basin propagating NW-wards from Eocene to earliestOligocene shows thin-skinned compressional deformation, with syn-depositional basin-floor tilting andsubmarine removal of the basin infill above active structures. Locally, a steep submarine slope scar isoverlain by kilometric-scale blocks slided NW-wards from the orogenic wedge. The deformations of thebasin floor and the associated sedimentary and erosional features are kinematically consistent with D2in the Dauphiné foreland. Since ∼32 Ma, the previously subsiding areas were uplifted and the syntectonicsedimentation shifted westwards. Simultaneously, the paleo-accretionary prism, which developed dur-ing the previous, continental subduction stage, was rapidly exhumed during the Oligocene collision stagedue to westward indentation by the Adriatic lithosphere, which likely enhanced the relief and erosionrate. The proposed palinspastic restoration takes into account this two-stage evolution, with importantnorthward transport of the distal passive margin fragments (Brianc onnais) involved in the accretionnaryprism before the formation of the western arc, which now crosscuts the westward termination of theancient orogen. By early Oligocene, the Ivrea body indentation, which was kinematically linked with theInsubric line activation, initiated the westward escape and the curvature of the arc was progressivelyacquired, as recorded by southward increasing counter-clockwise rotations in the internal nappes. We
propose that the present N-S trend of the Ivrea lithospheric mantle indenter which appears roughlyrectilinear at ∼15 km depth could be a relict of the western transform boundary of Adria during its north-ward Eocene drift. The renewed Oligocene Alpine kinematics and the related change in the mode ofaccomodation of Africa–Europe convergence can be correlated with deep lithospheric causes, i.e. partialdetachment of the Tethyan slab and/or a change in motion of the Adria plate, and was enhanced by theE-directed rollback of the eastern Ligurian oceanic domain and the incipient Ligurian rifting.
. Introduction

The Alpine orogen resulted from the collision of the Adri-tic microplate, supposedly linked with Africa, with the European
ontinental margin of the Western Tethys ocean during Earlyertiary times. The Africa–Europe convergence was oriented N-
(Dewey et al., 1989; Rosenbaum et al., 2002) but the Adriatic

∗ Corresponding author. Tel.: +33 476635904.E-mail address: [email protected] (T. Dumont).

264-3707/$ – see front matter © 2011 Elsevier Ltd. All rights reserved.oi:10.1016/j.jog.2011.11.006

© 2011 Elsevier Ltd. All rights reserved.

microplate may have moved independently during the Tertiary(Channel, 1996; Handy et al., 2010). The Western Alpine orogenis well documented but the paleogeographic restoration is stilldebated (Schmid et al., 2004; Handy et al., 2010). The arcuate shapehas been interpreted in different ways, involving (i) pre-Alpine(Tethyan) paleogeographic inheritance on the European marginside (Lemoine et al., 1989), or due to the shape of the Adriatic
indenter (Tapponnier, 1977); (ii) purely collisional origin due toindenter-induced body forces causing variable transport/spreadingdirections, referred to as the radial outward model (Platt et al.,1989b); (iii) plate motion with rotation of the Adriatic microplate
dx.doi.org/10.1016/j.jog.2011.11.006

http://www.sciencedirect.com/science/journal/02643707

http://www.elsevier.com/locate/jog

mailto:[email protected]

dx.doi.org/10.1016/j.jog.2011.11.006

eody

aeme(aOt(

ccekiecEB2c2

mpatLtpe“medcts

rtTvnosfmag

pemttwtbd

2

o

T. Dumont et al. / Journal of G

nd/or part of the Penninic foreland (Vialon et al., 1989; Collombett al., 2002 and references therein), or with change in relativeotion of the Adriatic microplate (Schmid and Kissling, 2000; Ford

t al., 2006 and references therein). As proposed by Handy et al.2010), a sharp change occurred at about 35 Ma, in the motionnd configuration of the Adriatic microplate, and the subsequentligocene dynamics could be partly driven by the initiation of

he Ligurian rollback subduction and associated eastward retreatVignaroli et al., 2009).

Nevertheless, the finite radial shape of the Western Alpine arcannot be simply restored without facing overlap problems in itsentral part. This geometry results from progressive deformationvents from Eocene to Miocene, and involves rotations of ancientinematic indicators during younger deformation stages, especiallyn the Internal Zones (Fig. 1; Choukroune et al., 1986; Collombett al., 2002; Rosenbaum and Lister, 2005). There is evidence of anti-lockwise rotation of transport directions through time, both in thexternal and in the Internal Zones (e.g. Lemoine, 1972; Merle andrun, 1981; Steck, 1998; Schmid and Kissling, 2000; Ceriani et al.,001), so that the initial geometry can only be restored throughonsideration of incremental displacements (Capitanio and Goes,006).

The present arc is outlined by a lithospheric thrust ramp com-only called “Crustal Pennine Thrust” (CPT, Fig. 1), exposed at

resent at the front of the Internal Zones, which are metamorphic,nd corresponding to at least an 80 km offset of the Moho alonghe ECORS-CROP profile (Guellec et al., 1990; Kissling et al., 2006;ardeaux et al., 2006). This feature occurred quite late in Alpine his-ory and does not fit the earlier Alpine kinematics and geometry,articularly in the Internal Zones (Schmid and Kissling, 2000; Dèzest al., 2004; Thomas et al., 1999). However, in the footwall of theCrustal Pennine Thrust”, that is, in the External Zone, the displace-ents and rotations are moderate (Gratier et al., 1989; Aubourg

t al., 1999). It is thus possible to observe the interference betweenifferently oriented shortening stages during the development ofontinental collision more easily than in the Internal Nappes stackhe building of which was polyphase and involved in continentalubduction.

The aim of this paper is to depict how the Alpine Oligocene plateevolution is recorded within the external part of the Alps, both inerms of deformation and of sedimentary evolution through times.he arguments considered are (i) the interference structures andariably-directed nappe displacements that are found in the Exter-al Zone within the Dauphiné and southern Subalpine domainsf the western and southwestern parts of the arc (Fig. 2) and (ii)ynsedimentary deformation and displacements of the Tertiaryoreland basins over the External Zone. A review of structural, meta-

orphic and chronological data available from the whole westernnd central Alps provides an integrated framework for the investi-ated kinematic changes.

Cross-folding in the External Zone has been previously inter-reted as an interplay between Pyrenean and Alpine shorteningvents, that is between the Iberian and Apulian plates kine-atic effects (i.e. Lemoine, 1972; Ford, 1996). It is shown here

hat a significant part of N-S shortening is actually younger thanhe “Pyrenean-Provence” event and just preceeded the west-ard Oligocene propagation of the Internal Nappes. It is proposed

hat these structures, which formed around the Eocene-Oligoceneoundary, are linked to the NW propagating Adria–Europe collisionuring the early stage of the Alpine orogenesis.

. Structural and stratigraphic setting

The External Zone of the Western Alps (Fig. 1) is composedf elevated crystalline basement massifs having recorded the

namics 56– 57 (2012) 18– 38 19

Hercynian orogeny (Corsini et al., 2004; Guillot et al., 2009), sur-rounded by a Tethyan sedimentary cover of Mesozoic age andscattered remnants of Cenozoic Alpine foreland basins (e.g. DeGraciansky et al., 2010, and references therein). The basement mas-sifs trend NE-SW from Mont-Blanc to Belledonne, and NW-SE in thesouthernmost part of the Alpine arc (Argentera). The NE-SW trendcorresponds to the Hercynian fabric reactivated in large-scale tiltedfault blocks during the Tethyan rifting (e.g. Lemoine et al., 1986and references therein). This part of the European palaeomargin ofthe Tethys suffered approximately E-W shortening in the footwallof the CPT during Alpine orogenesis (e.g. Dumont et al., 2008 andrefrences therein), The Pelvoux massif, which is located at the tran-sition between the NE-SW and NW-SE trends, has a sub-circularshape (Fig. 2) because it suffered several non-coaxial Pyrenean andAlpine shortening events (Ford, 1996; Dumont et al., 2008).

This compressional interference structure was first affectedby N-S shortening events commonly assigned to the “Pyrenean-Provence” stage, during late Cretaceous to Eocene times (Meckelet al., 1996; Ford, 1996; Michard et al., 2010). Subsequently,that is during late Eocene to earliest Oligocene, a first set ofnon-metamorphic nappes (“Embrunais Nappes”, Figs. 1 and 2),composed of late Cretaceous deep-water sediments likely ofoceanic origin and of Mesozoic cover detached from the distal andmiddle parts of the European palaeomargin, were gravitationallytransported towards more proximal portions of the European fore-land (Kerckhove et al., 1978; Merle and Brun, 1981; Ford et al.,2006). It is observed that the later stages of thrust system propaga-tion (from middle Oligocene onwards) were more radially directed(Choukroune et al., 1986; Platt et al., 1989a). The main associatedcrustal-scale structure corresponds to the “Crustal Pennine Thrust”CPT (Figs. 1 and 2), which represents the limit between the foreland(including the early Embrunais Nappes; E, Fig. 1) and the metamor-phic, Internal Nappes stack (Sue and Tricart, 2003). The Pelvouxmassif was lying in the footwall of both the NW-ward directedEmbrunais Nappes and the W-ward directed Internal Nappes,which crosscut the latter (Dumont et al., 2008). This explains itsantiformal dome geometry.

The Mesozoic series overlies a sharp, late Hercynian unconfor-mity, developed as a peneplanation surface which became flat andhorizontal over the whole study area between late Carboniferousand early Triassic times. The so-called Dauphiné type (central partof the External Western Alps) and Subalpine Mesozoic sequence(Subalpine massifs and southern part of the arc; Fig. 2) are charac-terised by the following formations:

- Late middle to Late Triassic: thin peritidal dolomites showingonly minor thickness variation, which implies that the whole arearemained flat and horizontal until near end-Triassic times. TheTriassic sequence, which is only made of carbonates in Dauphiné,remains attached to the basement, but it thickens further S and SEin the SE-France basin (Courel et al., 1984), and also in the InternalNappes, including evaporites which provide widespread detach-ment layers. The Triassic sequence is capped by thin alkaline totransitional basaltic flows in Dauphiné, which may indicate thestartpoint of Tethyan rifting.

- Lowermost Liassic (early to middle Hettangian) transgressiveplatform carbonates grade upwards into thick early Liassic toMiddle Jurassic hemipelagic marls and limestones. These latterformations are coeval with repeated stages of extensional fault-ing (Chevalier et al., 2003; Dommergues et al., 2011), and showimportant thickness and facies changes due to differential subsi-dence (Lemoine et al., 1986; Dumont, 1998).

- Late Jurassic to early Cretaceous pelagic, post-rift carbonatesare rarely preserved in the Dauphiné massifs, but the post-riftunconformity is locally observed thanks to Tithonian limestonesdirectly overlying the Hercynian basement (Barféty and Gidon,

20 T. Dumont et al. / Journal of Geodynamics 56– 57 (2012) 18– 38

Fig. 1. Overall map of the Western Alps and their foreland. CPT: Crustal Pennine Thrust, boundary between the External and Internal Zones. Horizontal stripped areas:Internal Zones, made of metamorphic units displaced from the European tethyan margin, the Ligurian Tethys ocean and from the Adriatic margin. Vertical stripped areas:e gin (BE

-

-

arly emplaced nappes, including units issued from the distal European passive mar: Embrunais-Ubaye nappes; L: Ligurian nappes.

1983). The post-rift cover is widespread further to the west andsouth, providing the thick carbonate series of the Subalpine mas-sifs.

The Upper Cretaceous formations recorded the earliest com-pressional deformation (pre-Senonian folding) in the DevoluySubalpine massif, due to the motion of the Iberian block (Meckelet al., 1996).

A sharp pre-Priabonian continental erosion surface cuts theMesozoic sequence downwards from the southeast (Maritime
Alps) to the Pelvoux massif further northwest (Gupta and Allen,2000). This event was linked with exhumation of the Pelvouxbasement and folding of the Dauphiné and Subalpine Mesozoiccover, and it is assigned to the Iberian plate motion (Gidon,
rianc onnais, Piedmont) and from the ocean floor (Helminthoid flyschs)—P: Prealps;

1979; Ford, 1996). Later on, the subsidence due to flexural bend-ing of the European foreland underneath the propagating Alpinewedge (Sinclair, 1997) led to the deposition of a transgressivesequence including Middle to Late Eocene platform limestones(Pairis, 1988), hemipelagic Globigerina marls and finally thick tur-biditic sandstones/shales alternations dated latest Eocene-earlyOligocene (Ravenne et al., 1987; Joseph and Lomas, 2004). ThePaleogene sediments, which are widespread in the southern partof the Western Alps, are capped by a characteristic formation
containing olistostrome over much of the Western Alpine arc(“Schistes à blocs”; Kerckhove, 1964) and by the gravity-drivenemplacement of the first “exotic” nappes in the basinal setting(Kerckhove, 1969; Campredon, 1977).

T. Dumont et al. / Journal of Geodynamics 56– 57 (2012) 18– 38 21

Fig. 2. Detailed map of the Dauphiné, Provence, Southern Subalpine and Maritime Alps areas, with location of Figs. 3 and 7. A: locality of Figs. 8, 9, 10 (bottom) and 11 (right).B ole ofA aroun

3A

3

istfpem

: locality of Fig. 11 (left). C: locality of Fig. 10 (top). CPT: Crustal Pennine Thrust, sreas of interest (see text)—A: around Restefond pass (SE of Barcelonnette city); B:

. Structure of the Dauphiné-Subalpine foreland before thedria–Europe collision

.1. Hercynian and Tethyan inheritance

The structure of the External Crystalline basement massifsn the Western Alps (Mt Blanc, Belledonne, Pelvoux; Fig. 1) istrongly influenced by the Permo-Carboniferous External crys-alline shear zone trending N30◦E and including local N-S strike-slip
aults (Guillot et al., 2009). The orientation of the Hercynianetrofabric changes to N140◦E in the Argentera massif (Corsinit al., 2004). It can be used as a post-Permian deformationarker.
the Internal Nappes; EBT: Embrunais Basal Thrust, sole of the Embrunais Nappes.d the Galibier pass (N of Brianc on city); C: Faucon du Caire (S of Gap city).

The Dauphiné basement massifs, between Belledonne andPelvoux, represent NS-trending Jurassic tilted blocks (Fig. 3;Lemoine et al., 1986). They result from reactivation of the Hercynianfabric and are subparallel to it, but they were moved obliquely byTethyan syn-rift extension (NW-SE; Lemoine et al., 1989; Dumontet al., 2008). Alpine inversion consists mainly of buttressing inthe hangingwall of master rift faults and shortcuts in their foot-wall. Basement shortening involves both folding and thrusting. Inthe Argentera massif, maximum burial is estimated at 4.8–7 kb
(Sanchez et al., 2011b), but in the Pelvoux massif the basementdeformation processes are still debated, considering the moremoderate burial setting (Ford, 1996; Dumont et al., 2008). Compres-sional deformation increases eastwards, approaching the Crustal


F ifs (ar( t blocka by pre

Ptotae

snnem

3

mrptedsFitlsase

twcf1n

ig. 3. Tethyan and Pyrenean-Provence inheritance in the Dauphiné External massBelledonne-Taillefer, Grandes Rousses-Rochail) corresponds to Tethyan tilted faul

sub-circular shape, its southern and southwestern boundaries beeing underlined

ennine Thrust. There is no evidence for compressional reactiva-ion of the extensional boundary faults. The first-order wavelengthf compressional structures is of the same order of magnitude thanhe major tilted blocks width: i.e., the Grandes Rousses basementnticline is superimposed on a 10 km-wide tilted block (Dumontt al., 2008).

Conversely, the Pelvoux basement massif has a sub-circularhape which is best explained by the interplay between several,on-coaxial shortening events. It is cored by a relatively homoge-eous late Hercynian granite (Guerrot and Debon, 2000) with littlevidence of important variations in the syn-rift series around theassif (Barféty, 1988).

.2. Pre-Priabonian structures (D1)

The Alpine flexural basin floor recorded compressional defor-ation before the onset of sedimentation, which onlapped a locally

ugged topography (Gupta and Allen, 2000). A pre-Senonian eventroduced local folding of the Mesozoic sequence in basinal set-ing, involving gravity sliding close to the platform edge (Michardt al., 2010). A younger, basement-involved compressional event isocumented by high-angle basement thrusts sealed by Priabonianediments which are found in the south and SW Pelvoux areas (a,ig. 3; Gidon et al., 1980; Ford, 1996). The associated kinematicndicators in the footwall Mesozoic sediments indicate a S-SWransport direction consistent with another set of basement thrustsocated further north (b, Fig. 3) but not sealed by the Paleogeneediments except at their southeastern termination, and which aressigned to the same shortening event. All these pre-Priaboniantructures are tilted by younger EW shortening events (Dumontt al., in press).

This pre-Priabonian compressional event D1 caused an impor-ant exhumation of the whole southern part of the Pelvoux massifith complete removal of the Mesozoic stratigraphic section by

ontinental erosion. The pre-Priabonian truncation surface is alsoound on the northern side of the Pelvoux massif (Barbier et al.,973), allowing the underlying Mesozoic sequence to be completedorthwards up to Upper Jurassic. There, this surface is onlapped

ea located in Fig. 2): the NE-SW to NS orientation of the western Dauphiné massifss (red) superimposed on the Hercynian fabric. Conversely, the Pelvoux massif has-Priabonian thrusts (black).

southwards by coarse fluvial conglomerates at the bottom of thePaleogene Flysch des Aiguilles d’Arves Fm., partly sourced by thePelvoux cristalline basement (Ivaldi, 1987). The southern Subalpinedomain, located to the SE of the Pelvoux massif (Fig. 2), developeda large wavelength uplift with NW-ward truncation of the UpperCretaceous to Jurassic sequences before the Eocene transgression.

It is noteworthy that the trends of the structural and tectono-sedimentary features related with this D1 compressional event arestrongly oblique or even sub-perpendicular to the present orogenin the southern part of the arc, represented by the CPT.

4. Foreland subsidence and deformation: NW-ward orogenpropagation during Eocene

4.1. Early Alpine deformation (D2)

An important amount of N-S convergence and northward dis-placement of the Alpine orogenic wedge with respect to theEuropean foreland is considered in the Central and Eastern Alpsduring late Eocene times (Froitzheim et al., 1994; Schmid andKissling, 2000; Dèzes et al., 2004), requiring either a major sinistral-oblique accommodation zone at the western end of the early Alpineorogen as postulated by Ricou and Siddans (1986), or a stronglyoblique oceanic subduction of the Piedmont ocean and further col-lision in the Western Alps (Handy et al., 2010). The External westernAlps provide kinematic data corresponding to this deformationstage, both in the cristalline basement of the Pelvoux area and in thesurrounding Mesozoic and Tertiary sedimentary cover. Importantnorthward to NW-ward displacements occurred at the southernand eastern sides of the Pelvoux massif, i.e. the “Perron des Claux”thrust (Vernet, 1966), which can be followed laterally over morethan 30 km (PDC, Fig. 4). In the southern Pelvoux area (site 1, Fig. 4),
it crosscuts the Meso-Cenozoic cover, and further north it detachesthin basement slices in the eastern Pelvoux region (sites 2–4, Fig. 4).The propagation of the PDC thrust from the Meso-Cenozoic coverdown to the Hercynian basement towards the north can only have


Fig. 4. The Meije dome, an interference between NS (or NW-SE) and EW shortening in the Pelvoux external basement massif. Upper part: 3D map of the basement/Mesozoiccover interface (rainbow shaded surface) and of the granite/gneiss interface (purple shaded surface) in the northern Pelvoux area. Despite the erosion of the former surfacein the central part, both of them are clearly involved in the dome shape, which demonstrates that this structure is Alpine in age (post-Mesozoic). Lower part: block diagram(looking to the East) and associated NS section across the Pelvoux massif and the Meije dome, with the main thrusts and localities cited in the text—1: col de Méollion andS ); 3: nV massip

ot

“tTwyt

ommet Drouvet, north of Orcières; 2: northern side of Les Bans valley (Onde riverallon de Chambran, SE of Rochers de l’Yret; 5: from NE slopes of the Combeynotass).

ccurred provided that the latter had been previously uplifted (dueo pre-Priabonian shortening, D1, Section 3.2).

The PDC thrust probably connects further north to theMadeleine” thrust which duplicates the Eocene sequence overhe Combeynot basement unit (site 5, Fig. 4; Barbier et al., 1973).
he deformation in its footwall at sites 1 and 4 indicate a NW-ard transport. The PDC thrust has been deformed during several
ounger Alpine events, as shown by (i) severe overprint by top-to-he-west shearing in the footwall of the Crustal Pennine Thrust (site

orthern side of Ailefroide valley, between Ailefroide and Pelvoux villages; 4: upperf (Rochers de la Madeleine) to southern slopes of Crête de Chaillol (W of Lautaret

11: Pêcher et al., 1992; Butler, 1992; Simon-Labric et al., 2009), (ii)long wavelength folding (Fig. 4), (iii) eastward dip caused by differ-ential uplift of the Pelvoux massif with respect to Internal Nappesduring the Neogene (Tricart et al., 2000) and (iiii) offset of the thrustsurface by several late orogenic NE-SW dextral strike-slip faults.

Several reverse faults are found in the footwall of the PDCroof thrust, which are also N- to NW-directed. The Pelvoux thrust(PeT, Fig. 4) is associated with N-directed imbricates in the lowerMesozoic sediments (Pêcher et al., 1992 and personal data); the

2 eody

Cbcetatctt2

tilssmMtbniatosmPid

l(fTmwe(twsw2o

4E

pEuapaEbupeEect

4 T. Dumont et al. / Journal of G

ombeynot thrust (CoT) and Meije thrust (MeT) transport foldedasement over the Jurassic cover further north. The Meije thrustlimbs section in its footwall towards the north, but has an appar-nt NE-ward dip due to further tilt. The hangingwall basement ofhe Meije and Combeynot thrusts include large wavelength rampnticlines involving the granitic core, the gneissic envelope andhe Triassic-lower Liassic sedimentary cover (Fig. 4). The Mesozoicover in the footwall of the Meije and Combeynot thrusts con-ains ENE-WSW trending drag folds, and the sole of the Combeynothrust sheet shows a top-to-the NW shear band (Authemayou,002).

There is some evidence that the motion of the PDC thrust and ofhe associated Pelvoux, Meije and Combeynot thrusts occurred dur-ng earliest Oligocene times. The Combeynot shear band yielded aowermost Oligocene 40Ar/39Ar age (Simon-Labric et al., 2009). Softediment deformation is recorded in the very top of the Paleogeneediments at several localities, indicating top-to-the NW displace-ents associated with the PDC thrust: to the SE of the Pelvoux, itseso-Cenozoic hangingwall sequence is overlain by a thick Ter-

iary olistostrome (“complexe d’Orcières”, Debelmas et al., 1980)eneath the Embrunais Basal Thrust. N to NW recumbent isocli-al folding is sealed by this olistostrome and vanishes laterally in

t (Kerckhove et al., 1978). Further west, Gidon and Pairis (1980)nd Butler and McCaffrey (2004) provide evidence for NW-directedransport in the footwall of the PDC thrust, which occurred duringr very soon after the deposition of the uppermost Paleogene flyschediments (Dumont et al., in press). Similar syn-sedimentary defor-ation criteria are found along the northern continuation of the

DC thrust (Bravard and Gidon, 1979). The olistostrome represent-ng the very top of the Paleogene sedimentary sequence is locallyated early Oligocene (Mercier de Lépinay and Feinberg, 1982).

The D2, top-to-the N to NW deformation of the Dauphiné fore-and is related with the emplacement of the earliest Alpine nappesEmbrunais Nappes, Dumont et al., 2008), whose remnants areound immediately to the SE of the Pelvoux massif (Figs. 1–5).hese nappes, made of oceanic and continental margin sedi-ents, are derived from the uppermost part of the accretionnaryedge as shown by their very low metamorphic grade. They were

mplaced initially in basinal setting by the way of gravity processesKerckhove, 1969) and they finally covered a much larger part ofhe Dauphiné and Subalpine forelands than their present remnants,ith a significant thickness of 4–8 km over part of the Pelvoux mas-

if (Waibel, 1990) and the Argentera massif (Labaume et al., 2008)hose basement exhumation occurred recently (Sanchez et al.,

011a). Some other remnants of these early Alpine nappes consistf the Prealps and the Ligurian flysch nappes (P, L, Fig. 1).

.2. Foreland basin propagation and orogen migration during theocene

The Eocene flexural basin propagated first over the Brianc onnaisart of the European palaeomargin during the early to middleocene. Its basal infill unconformably covers the Brianc onnaispper Cretaceous to Paleocene deep marine sequences withoutny evidence of emersion. The coastal migration reached moreroximal parts of the Tethyan margin, that is the southern Sub-lpine, Dauphiné and Helvetic domains, during the middle to lateocene (Priabonian; Ford et al., 2006, and references herein). Theasin floor is marked by a sharp transgressive surface, locallynconformable (Pairis et al., 1984), because this area had beenreviously exposed due to the Pyrenean-Provence compressionalvents (D1). The propagation of the basin over it during late
ocene to earliest Oligocene times is marked by a rapid deep-ning due to flexural subsidence: the facies grade upwards fromoastal limestones to hemipelagic foraminiferal marls and thickurbiditic sandstone series, locally named “Grès d’Annot”, “Grès du
namics 56– 57 (2012) 18– 38

Champsaur”, “Flysch des Aiguilles d’Arves” and “Grès de Taveyan-naz” from south to north, respectively. As expected in a flexuralbasin setting (Sinclair, 1997), the diachroneity of this transgressivesequence over the whole Eocene time span is shown by compiledstratigraphic data (Fig. 6, left).

This Eocene propagation and coastal migration occurredtowards the N- to NW in the southern Subalpine domain(Kerckhove, 1969; Guardia and Ivaldi, 1987) and in the Helveticrealm (Kempf and Pfiffner, 2004; Ford et al., 2006), apart from aSW-ward lateral propagation and confinement at the western ter-mination of the basin (Maritime-Alps to Haute-Provence; Sztrakosand du Fornel, 2003; Puigdefabregas et al., 2004; Campredon andGiannerini, 1982). Sediment supply from the south and northwardor NW-ward sedimentary transport directions of the distal deltaicfans (Ravenne et al., 1987; Callec, 2001) are in agreement with thisN to NW direction of propagation of the lithospheric flexure. How-ever, as pointed by Ford et al. (2006), the geometry of the Eoceneflexural basin has been heavily distorted by the younger develop-ment of the Alpine arc.

The starved infill of the Paleogene flexural basin bears evidenceof synsedimentary deformation preceeding the emplacement ofthe first gravity-driven nappes and of the accretionnary wedgehaving caused the N to NW-directed deformation D2. Even inits western termination, N to NW-ward propagation of deforma-tion is recorded during the Late Eocene (Stanley, 1980; Tempier,1987) and the Grès d’Annot in Maritime-Alps suffered NW-directedbasin floor deformation, documented by NW- or SE-directed onlaps(Ravenne et al., 1987; Euzen et al., 2004; Smith and Joseph, 2004)or sequences architecture (Broucke et al., 2004). Compressionalbasin-floor deformation is also demonstrated by the occurence oflarge-wavelength removal of the Paleocene section prior to thefirst Embrunais Nappes emplacement. This feature is best docu-mented across a NW-SE cross-section (Fig. 7), which is trending“orogen-parallel” with respect to the present arc, contrary to themore classical NE-SW profiles found in the litterature (e.g. Fordet al., 1999). This removal, which took place in a basinal settingas demonstrated by the permanent occurrence of an olistostromeover the surface, is found over two long-wavelength anticlines cor-responding to the Embrun half-window and to the Barcelonnettewindow (Fig. 7) where the Paleocene series is missing beneath thenappes. As these areas correspond to the Jurassic Vocontian basin,this erosion was probably caused by an uplift due to an incipientstructural inversion of this basin. The relationships between Paleo-gene basin floor folding and erosion can be observed to the south ofthe Barcelonette window, SE of Barcelonette city (Figs. 7 and 8). TheMesozoic series are locally affected by thin-skinned deformation,showing a tight, EW trending and northward directed recumbentanticline cored by Triassic evaporites (Terre Plaine fold, Fig. 8).The Paleogene flysch series (Grès d’Annot Fm.) have been com-pletely eroded above the fold hinge, and the truncation surfaceoutcrops further south, over the normal limb. Here, the evidencefor Paleogene syndepositional activity of the fold consist of (1)southeastward-tilt of the hemipelagic Globigerina marls, which areonlapped by the lower part of the Grès d’Annot formation (upperFig. 8, left; Kerckhove, 1974) and by a marker layer of conglomeraticdebris-flow usually occurring ∼300 m above the base of the for-mation (Jean, 1985; Joseph and Lomas, 2004), (2) northwestwarderosional truncation of the Grès d’Annot fm., from >600 m thickto zero in about 5 km across the Bonnette pass (Figs. 8 and 9). Thetruncation surface represented a NW-dipping paleoslope presentlyincised by several valleys (Fig. 8, top and Fig. 9) and capped bythe olistostrome. This submarine erosional event seems to have
followed or to have occurred in association with soft-sedimentdeformation and normal faulting in the Grès d’Annot further south-east (Bouroullec et al., 2004) which may indicate gravitationalunstability.


F sts inv(

kfFtt

ig. 5. Structural sketch map from Dauphiné to Provence, and main faults and thruD3), respectively (cartoons in the lower part of the figure).

The paleoslope together with the olistostrome are overlain byilometre-scale blocks of Mesozoic sedimentary cover derived
rom the Brianc onnais and Provence domains (Fig. 8; location Aig. 2). We propose to regard these blocks as olistoliths and not asectonic thrust sheets, mainly because there is no evidence of tec-onic shear zones at their base. They overlie basinal clastic deposits
olved in the N- to NW-directed episode (D2) and in the W- to SW-directed episode

covering a kilometre-scale submarine paleoslope that truncates theEocene flysch stratification, also with no evidence of tectonic con-
tact (Fig. 10, bottom). Similar olistoliths of Brianc onnais origin aredescribed further SE, to the SE of the Argentera massif (Lanteaume,1990). These blocks show different stratigraphic signatures, indi-cating that they slid from a paleogeographic hinge zone inherited


Fig. 6. Chronostratigraphic litterature review comparing the sedimentary record of the Paleogene flexural basin of the Western Alps (left part), the metamorphic imprint ofthe European passive margin units involved in the Alpine orogen (central part) and their kinematic record (tectonic transport criteria, right part). The continental subductionregime, marked by the propagation of the flexural basin and by the diachronicity of the HP-LT metamorphism in the orogenic wedge, is associated with N-directed transportcriteria. It ceased during early Oligocene, coeval with the re-orientation of kinematic indicators (see refs. Agard et al. (2001), Amaudric du Chaffaut (1982), Barféty et al. (1992),Baudin et al. (1993), Berggren et al. (1995), Bigot-Cormier et al. (2000), Bogdanoff et al. (2000), Bousquet et al. (2002), Bucher et al. (2004), Callec (2004), Caron et al. (1980),Ceriani and Schmid (2004), Cliff et al. (1998), Crespo-Blanc et al. (1995), Dal Piaz (2001), Duchêne et al. (1997), Du Fornel et al. (2004), Egal (1992), Engi et al. (2001), Evansand Eliott (1999), Fischer and Villa (1990), Freeman et al. (1998, 1997), Gebauer (1999), Gubler-Wahl (1928), Hardenbol et al. (1998), Jeanbourquin and Goy-Eggenberger(1991), Keller et al. (2005), Keller and Schmid (2001), Kerckhove and Thouvenot (2008), Kurz et al. (1996), Lahondère et al. (1999), Lapen et al. (2007a,b), Lateltin (1987), LeBayon and Ballèvre (2006), Leloup et al. (2005), Lihou (1995), Malusà et al. (2005), Markley et al. (1998), Meffan-Main et al. (2004), Merle et al. (1989), Michard et al. (2004),M ve (19R 07), SeZ

fPJwteeFti∼lodgNBtocbo(

onié (1990), Mosar et al. (1996), Nagel (2008), Padoa (1999), Pairis and Kerckhoubatto and Hermann (2001), Schlunegger and Willett (1999), Schwartz et al. (20immermann et al. (1994)).

rom the Tethyan rifting (Fig. 11, right) and inverted during thealeogene. Some of them contain Provence-type, reefal upperurassic facies (log 1, Mourre Haut and Grande Séolane units),

hich supports the hypothesis of a southern provenance, consis-ent with the interpretation of gravity sliding from the northerndge of the Provence platform. One of them shows an importantrosional gap beneath the Tethyan breakup unconformity (log 3,ig. 11), a typical signature of a hangingwall block. It is noteworthyhat very similar anomalies are found in a stack of “thrust sheets”n the Brianc onnais nappes stack near the Galibier pass, that is90 km further NNW (Fig. 11, left, and location B Fig. 2). In this

atter locality, which lies in the hangingwall of the CPT, out-f-sequence thrusting associated with D3 (Section 5.1) makes itifficult to restore the initial order of the units, but Fig. 11 (left part)ives a tentative correlation based on stratigraphic arguments.evertheless, the similarities between sites A (Restefond pass) and

(Galibier pass), located in the footwall and in the hangingwall ofhe CPT, respectively, are to be considered regarding the restorationf the Internal zones (Section 6) and their displacement during the
ollision stage (Section 5.1). Above these blocks initially emplacedy gravitational processes, the bulk of Embrunais nappes is madef Helminthoid flyschs series of late Cretaceous to Paleocene ageKerckhove, 1969), obducted from the oceanic realm.
87), Parsy-Vincent (1974), Reddy et al. (2003), Ring (1995), Rubatto et al. (1999),no et al. (2005), Steck (1990), Tilton et al. (1991), Varrone and d’Atri (2007), and

To sum up, the tectono-sedimentary behaviour of the Paleo-gene flexural basin is documented by onlaps and submarine erosionassociated with basin floor folding during and soon after its Pri-abonian to early Oligocene infill. This immediately preceeded theD2 shortening episode recorded in the Dauphiné foreland andthe emplacement of the Embrunais nappes. All these featurescan be consistently integrated in the NW-directed propagationmodel of the Alpine orogen from Eocene to early Oligocenetimes.

4.3. Crustal record of continental subduction during the Eocene

According to several authors, the propagation of the Alpineorogen during the Eocene is maintained by continental subduc-tion processes (Berger and Bousquet, 2008, and references herein).Following this, the shallow level features described above mustbe compared to the deep crustal record of the Internal Zones,which exhibit a wide range of European continental margin unitsgradually involved in the subduction channel during the Paleo-
gene. Reviews of geochronological and tectono-metamorphic data(e.g. Berger and Bousquet, 2008; Bousquet et al., 2008) indicatethat high-pressure metamorphism occurred over a long time spanbetween 70 and 35 Ma, while there is little evidence for an elevated


Fig. 7. Upper part: NW-SE section across the external zone of the southern western Alps, from the southern Pelvoux to the Argentera massif (vertical exaggeration 2×). Thisprofile is trending sub-parallel to the present Alpine orogen in the southern part of the western arc, but it crosscuts sub-perpendicularly the early Alpine structures (D2).The Paleogene series (yellow) are missing in the central part of the profile (area between the yellow dashed lines on the map) due to erosion before the emplacement of theEmbrunais nappes (orange). This erosion, which occurred in submarine setting (see Figs. 8–10), is regarded as the consequence of an incipient structural inversion of theM arcelf

o(

ezetbbcoofIA(ftI(wg

esozoic Vocontian basin, whose thick series are now exposed in the Embrun and Brom the SW: the Embrunais Nappes are underlined by snow in the foreground.

rogen at that time considering the relatively low erosion budgetKuhlemann, 2000).

The diachroneity of involvement of the distal margin units,specially the Brianc onnais domain, in the continental subductionone is illustrated in Fig. 6 (middle part) showing high-pressure andxhumation ages plotted from some selected references betweenhe oceanic units and the proximal European margin representedy the External Zone. It documents the overlap of high-pressure andrittle exhumation ages in different fragments of the Brianc onnaisrust, which is in agreement with their gradual accretion to therogenic wedge. This evolution is coeval with the migrationf the Paleogene flexural basin towards the Dauphiné/Helveticoreland (Fig. 6, left part), spanning the whole Eocene stage. In thenternal Zones, the kinematic indicators corresponding to the earlylpine deformation stages are predominantly northward directed

Section 5.3), consistent with the tectono-sedimentary evidencerom the flexural basin and from the foreland. The structures ofhe resulting accretionary buildup, exhumed at present in the
nternal arc, are best shown across a NS-trending cross-sectionTricart and Schwartz, 2006). All these features are consistentith the orientation of Africa–Europe convergence during Paleo-
ene after Rosenbaum et al. (2002). Considering the palinspastic

onnette tectonic windows. Lower part: aerial photograph of the western Alpine arc

reconstruction of Schmid and Kissling (2000), the propagation rateof the foreland basin after Ford et al. (2006), and the subduction rateof the distal parts of the European margin (Berger and Bousquet,2008), the rate of propagation of the orogen would have been ofthe same order of magnitude than the Africa–Europe convergencerate (∼1 cm/yr). However, this estimation is poorly constrainedand it assumes that Adria was not moving independently of Africaduring Eocene times, which is still debated because of the possibleoccurrence of spreading of the Ionian sea between Africa and Adriabefore 35 Ma (Michard et al., 2002; Handy et al., 2010). Anyway,as pointed out by Handy et al. (2010), the northward displacementof Adria during Eocene fits the palinspastic width of the distalEuropean margin (about 120–150 km of Brianc onnais domain;Lemoine et al., 1986; Stampfli et al., 1998, 2002) predicted to havebeen consumed in the subduction zone. Considering the Adria platemotion direction, the tectonic transport criteria in the Internalnappes and the evidence of N-NW propagation of the forelandflexural basin during Eocene, a significant northward displacement
of the Brianc onnais units, at present spreading around the arc, isneeded during the early stages of Alpine continental subduction.This was postulated by the model of Ricou and Siddans (1986)and is consistent with some observed similarities between the


Fig. 8. The Restefond paleoslope, located to the SE of the Barcelonnette city (location Figs. 2 (A) and 7). Bottom: detail of the cross-section of Fig. 7(top) at the SE terminationof the Barcelonnette window (same colors legend as Fig. 7). Both onlap and erosion of the Grès d’Annot fm. occurred over the hangingwall of the Terre Plaine fold-and-thruststructure, which was therefore active during Priabonian to earliest Oligocene times. Top and middle: panoramic view of the northern slopes of the Restefond pass, showing(i) the onlap of the Grès d’Annot sandstones over the tilted Globigerina hemipelagic marls near “cabanne de Clapouse” (left part of the picture), and (ii) the truncation of theG The pw blockt

Ba

5f

5w

eOtt

rès d’Annot stratification beneath the “Schistes à blocs” olistostrome layer (grey).

ith respect to the panoramic view. Several hectometric to kilometric scale slidedext). The stratigraphic composition of these blocks is given in Fig. 11 (right).

rianc onnais and the Provence-Corsica-Sardinia upper Paleozoicnd Mesozoic stratigraphic sequences.

. The Oligocene revolution: westward extrusion andormation of the arc

.1. Deformation in the External Zone: Main Alpine,est-directed stacking (D3)

The eastern part of the Dauphiné zone was underthrust
astwards beneath the Crustal Pennine Thrust from the earlyligocene onwards (Simon-Labric et al., 2009). This is recorded by
he dominantly top-to-the west intense shear in the footwall ofhe CPT at the eastern edge of the Pelvoux massif (Butler, 1992),

aleoslope resulting from this truncation is dipping northwestwards, that is obliques are hanging over this paleoslope, which are issued from different domains (see

and approximately 30◦ diverging transport directions on bothsides of the Pelvoux culmination are observed (Fig. 5; Gamond,1980; Tricart, 1980; Bürgisser and Ford, 1998). This demonstratesthe occurrence of basement uplift in the Pelvoux area prior tothe D3 westward transport of Internal Nappes over it, due to thecumulative effects of D1 and D2 basement thickening. The changein orientation of shortening is documented in the footwall of theCPT by the tectonic overprint of deformation D3, which producedinterference structures with the previous shortening episodesbecause of its different orientation.

To the north of the Pelvoux massif, a change in transport direc-tions of thin-skinned thrust sheets from N-NW to W-NW or westis described (Bravard, 1982; Ceriani et al., 2001). Complicated 3Dstructures due to a near 90◦ change in shortening orientation, from


Fig. 9. Top: aerial photograph of the south-dipping “Mauvaise côte” cliff, located to the west of the Restefond pass. Bottom: same view with recent normal faulting restored( nted ia

atSitiduki

iwfbeTfhtr(

left part). This cliff truncates obliquely the submarine erosion surface which is prese ∼20◦ apparent angle with the erosion surface.

pproximately N-S (D2) to approximately E-W (D3), reactivate E-Wrending thrusts as strike-slip faults (Dumont et al., 2008). To theE of the Pelvoux, a D2 northwestward directed recumbent foldnvolving the Late Eocene flysch (Grès du Champsaur fm.), the olis-ostrome and part of the Embrunais Nappes (Kerckhove et al., 1978)s affected by D3 westward folding, so that antiformal hinges areeveloped both within the reverse limb and within the correct way-p section. This occurs in the footwall of the Prapic thrust, which isinematically linked with the WSW-ward propagation of shorten-ng in front of the Crustal Pennine Thrust (Bürgisser and Ford, 1998).

At a larger scale, the interplay between NS and EW shorten-ng is documented by the structure of the Meije granitic dome,

hose shape is not issued from a preserved Hercynian pluton butrom an Alpine compressional interference: this is shown by similarending of the boundary between the granitic core and the gneissicnvelopes and of the peripheral basement-cover interface with itsriassic cover (Fig. 4, top), thereby precluding any Hercynian originor this structure. The Meije dome is a result of N-S “arching” in the
angingwall of the Meije thrust (D2) combined with E-W arching inhe footwall of the Crustal Pennine Thrust (D3). This dome may beegarded a smaller scale version of the sub-circular Pelvoux massifFig. 3). Some other domes occur in the sedimentary cover of the
n Fig. 8. The stratification of the Annot sandstone fm. is enhanced by snow, showing

External Zone (Fig. 5), which are likely related with the same D2/D3interference.

5.2. Renewed distribution of foreland basins during earlyOligocene

The distribution of the foreland basins in the southern Subalpinedomain (External Zone of the Western Alps) changed completelyduring Early Oligocene times (Ford et al., 2006): the formation of theDigne nappe (Figs. 2 and 5), corresponding to the previously sub-siding flexural basin, led most of the Eocene-lowermost Oligocene,westward pinching out flysch deposits to be uplifted and erodedby a continental drainage pattern. Conversely, some continentalor lacustrine, westward thickening depocenters developed in theproximal foreland of this nappe, over an area which was previouslydevoid of sedimentation. Only a narrow area at the hinge betweenthese two domains shows the Eocene and Oligocene sedimentarysequences overlapping (Meckel et al., 1996), but generally with an
erosional unconformity between both (Fig. 10, top).
The early Oligocene sediments in the Barrême thrust-top basinrecorded (i) a ∼90◦ shift in sedimentary transport directions (Evansand Mange-Rajetsky, 1991; Callec, 2001) and (ii) a change in source


Fig. 10. Outcrop views of the erosion surface which caps the sediments of the Late Eocene-Earliest Oligocene flexural basin (continental subduction stage): (1) In basinalsetting (location A, Fig. 2; outcrop located in Fig. 8), the submarine erosion surface is covered by olistostrome deposits (2) dated of early Oligocene age in the Helvetic realm( towat he cono ouse)

rfoa

Mercier de Lépinay and Feinberg, 1982) and by slided blocks (Figs. 8 and 9); (3, 4)he late Eocene-early Oligocene succession (“Nummulitic”, N) and is onlapped by tf the outcrops: south of Faucon du Caire (3: ravin de la Bouchouse; 4: ravin de la B

ocks: the Grès de Ville were fed in crystalline basement clastsrom the south (Provence-Corsica-Sardinia continent) whereas theverlying Clumanc conglomerates were fed in non-metamorphicnd HP-LT ocean-derived clasts from the rapidly exhuming Alpine

rds the foreland (location C, Fig. 2), a rugged continental erosion surface truncatestinental “Molasse Rouge” fm. (fluvial conglomerates, 5) of Oligocene age. Location

.

wedge located to the east or the NE (Chauveau and Lemoine,1961; Evans and Mange-Rajetsky, 1991; Morag et al., 2008). Thelatter source zone, subject to very active erosion, has been iden-tified as being inherited from parts of the Eocene accretionary


Fig. 11. Statigraphic content of the blocks hanging over the Restefond paleoslope (right part; see Fig. 8; location A, Fig. 2), and comparison with the thrust sheets of theG esozoih out tht mpariI

wtprsAs22

ipssMwotFssH

aiEs

alibier area (left part; location B, Fig. 2). The strong variations observed in the Minge zone inherited from the Tethyan rifting. The same statement can be done abop-to-the west transport (deformation D3) in the hangingwall of the CPT. This conternal zones with respect to the Embrunais nappes.

edge that suffered strong shortening and uplift in early Oligoceneimes (Bernet and Tricart, 2010; Schwartz et al., submitted forublication). The sediments of the Tertiary Piedmont basin alsoecorded a tectono-sedimentary shift at the same time, which con-ists of a sharp erosional unconformity truncating highly deformedlpine nappes, and which is overlain by coarse continental clasticstarting from the Early Oligocene (Polino et al., 1991; Cibin et al.,003; Carrapa et al., 2004; Di Giulio et al., 2001; Marroni et al.,002).

Some Oligocene syndepositional deformation criteria observedn the French southern Subalpine foreland indicate a westwardropagation, clearly different from the Eocene flexural basinetting: (i) in the Barême thrust-top syncline, top-to-the westyndepositional folding occurred as early as 31 Ma (Artoni andeckel, 1998; Callec, 2001); (ii) further north, westward to NW-ard directed thrusting occurred prior to or during the deposition

f the Rupelian “Molasse Rouge” fm. in the Digne area (Esclangonhrust-sheet: Haccard et al., 1989) and in Faucon du Caire area (C,ig. 2; Roche Cline thrust sheets: Arnaud et al., 1978). A westwardhift of depocenters is observed in Oligo-Miocene times both in theouthern Subalpine chains (Couëffé and Maridet, 2003) and in theelvetic realms (Beck et al., 1998).

To sum up, the observed interplay between exhumation of the
xial chain, deformation of the western foreland, erosion and sed-mentation clearly shows the occurrence of a sharp change duringarly Oligocene times with respect to the Eocene framework: sub-idence inversions, changes in clastic provenance, changes in the
c series show that the Restefond blocks (right) are issued from a paleogeographice Galibier thrust-sheets (left), except that they were more severly overprinted by

son also supports an important northward or northwestward displacement of the

trends of syndepositional deformation and changes in the directionof displacements of facies and depocenters. The age of this eventcan be bracketed within a short time interval between the youngestdeposits of the flexural flysch basin (∼31–32 Ma, Fig. 6 and refer-ences herein) and the oldest infill in the thrust-top molasse basins(∼30–31 Ma; Artoni and Meckel, 1998; Callec, 2001).

5.3. The early Oligocene orogen

The extensive Alpine literature provides much evidence of dra-matic changes in the central part of the Alpine orogen during earlyOligocene times. Both the magmatic activity, the deep and shal-low structures, the morphology and the kinematic/geodynamicsetting in the whole Alpine realm are involved in this revolution:the igneous activity, including the emplacement of the Periadriaticplutons between 33 and 31 Ma (Müller et al., 2001), is regarded asa thermal consequence of slab breakoff in the Central Alps (VonBlankenburg and Davies, 1995). The Bergell Pluton emplacementpostdates N-directed nappes stacking and it is coeval with theonset of dextral shear and thrusting along the Periadriatic linesegments (Schmid et al., 1989, 1996; Müller et al., 2001; Handyet al., 2010). Contemporaneous calc-alkaline post-collisional vol-canism is reported from the early Oligocene flysch sediments in
the northwestern foreland (Vuagnat, 1985; Waibel, 1990; Ruffiniet al., 1997).
A review of published kinematic data in the Internal and Exter-nal zones (Fig. 6, right part) shows how brutally the trends of


Fig. 12. Summary sketch of the Paleogene evolution of the Alpine foreland in the southern part of the Western Alps. The stages of deformation D1 to D3 refer to the deformationhistory presented in the text: The D1 structures and basement exhumation are sealed by Priabonian sediments to the south of the Pelvoux massif, but are not dated. Therequired N-S shortening component is assigned to the Eocene motion of the Iberian plate whose effects are known in the Pyrenean and Provence realms (Section 3.2). TheD2 deformation is expected to occur diachronously in the foreland of the propagating accretionary wedge (vertical hatching), and follows shortly the NNW- to NW-wardpropagation of the flexural basin (Section 4). It corresponds to the continental subduction stage, and it reached the Pelvoux area around the Eocene-Oligocene boundary. TheD3 collision stage overprinted completely the previous orogenic wedge, which was indented westwards by the Internal metamorphic nappes stack (horizontal hatching),g erencg ther w

sTbEt

iving birth to the western Alpine arc (Section 5). This overprint is shown by interfrade nappes (EN, vertical hatching), whose erosion feeded the molasse basins toge

tretching lineations and transport directions vary through time.
he anticlockwise rotation was pointed by Platt et al. (1989a),ut one can see more precisely a sharp ∼90◦ change close to theocene-Oligocene boundary. Contrary to the coupled migration ofhe orogen and of the foreland basin during the Eocene lithospheric
e structures, deformation and uplift of the previously emplaced, low metamorphicith metamorphic rocks issued from the exhuming paleo-accretionnary wedge (IN).

flexure (Fig. 6, central and left parts), this tectonic shift seems to
have occurred more or less simultaneously over the whole Alpinerealm. Before, the internal zones were dominated by north-directedtransport, associated with “transverse” folds (Caby, 1973), i.e. E-W trending. Pervasive D1 transport lineations (Choukroune et al.,


Fig. 13. Proposed palispastic evolution of the western Alpine realm and surrounding areas. The reconstruction considers both paleogeographical and paleostructural con-straints from the literature, such as coastal migration of the flexural basin after Ford et al. (2006) and the estimated location of the Adriatic microplate after the sequentialrestoration of Schmid and Kissling (2000) and Handy et al. (2010) and more open choices such as the western termination of the Valais ocean (A). It is proposed that, beforeEocene, the Western Adria Transform Zone (WATZ) bounded a NW-dipping subduction zone beneath Corsica-Sardinia-Calabria, from a SE-dipping zone beneath Adria. Thecontinentward propagation of this transform zone allowed the Brianc onnais terrane to be separated from the Iberian plate and integrated in the Alpine accretionnary prism,t Early

r ligoce

1irwOFci2t

eef2tdaW2dr

he Adriatic crust and upper mantle therefore overlying the European crust. From

ectilinear western boundary of the Ivrea upper mantle indenter which cores the O

986; Carry, 2007) have been re-arranged by arcuate bending dur-ng later episodes (Rosenbaum and Lister, 2005). Afterwards, theenewed tectonic activity is marked by the activation of major,est directed crustal thrusts in the Western Alps during earlyligocene (Badertscher and Burkhard, 1998; Tricart et al., 2000;ügenschuh and Schmid, 2003; Simon-Labric et al., 2009), whichross-cut the previous nappes stack. Coeval eastward underthrust-ng of the Pelvoux massif is dated 31–33 Ma (Simon-Labric et al.,009). This is also coeval with the onset of dextral movement alonghe Insubric line.

This early Oligocene event is also detected through a stronglevation of the axial Alpine orogen, which is suspected consid-ring the increase in sediment budget in the northern and westernorelands (Kuhlemann, 2000; Kempf and Pross, 2005; Morag et al.,008; Bernet and Tricart, 2010) leading to basins overfill and tohe transition from flysch to molasse sedimentation. An other evi-ence is provided by the onset of coarse sedimentation in Lombardynd Piedmont, interpreted as a consequence of rapid unroofing in
estern and Central Alps (Giger and Hurford, 1989; Carrapa et al.,
004). From early Oligocene onwards, one can observe a dramaticiscrepancy between (i) the rapidly exhuming axial chain, now rep-esented by the Internal Zones, with exhumation and canibalization

Oligocene onwards, the northern part of Adria rotated and moved westwards. Thene to present arc could be a relict of the WATZ.

of the Eocene flexural basin with its initial overload in the Frenchforeland and (ii) rapid burial affecting the previously exposedEocene HP wedge in the Italian Piedmont (Bertotti et al., 2006).

Apart from the Alpine orogen itself, the Early Oligocene also cor-responds to the initiation of subsidence in the West European riftsystem (Merle and Michon, 2001), of the Corsica-Sardinia rifting(Lacombe and Jolivet, 2005), and to the onset of the Tyrrhenian-Apenninic dynamics (Vignaroli et al., 2009; Handy et al., 2010).The first-order geodynamic cause that can explain both these fea-tures and the kinematic re-organization of the Alpine chain is stilldebated, but an increasing influence of the deep-seated mantledynamics in the Mediterranean area is suspected (Faccenna et al.,2004).

6. Discussion and conclusion

The central and southern parts of the External Western Alps
show evidence of several interfering shortening episodes dur-ing Alpine convergence. The present Pelvoux large-scale domeprobably initiated over a basement ridge perpendicular to thepresent chain, i.e. W-E, and the southern Subalpine Meso-Cenozoic

3 eody

cdwoitaoActndmbrewwdp(sgAaftgI

tste2alhdepEAva

wfgci((itaots

tWceS


over shows basin-and-swell structures (Remollon and Barrotomes, Embrun and Barcelonnette nappe windows; Figs. 2 and 7),hich result from interference between shortening events of varied

rientations. Such interferences were up to now regarded as super-mposed effects of the dynamics of the Iberian and Adriatic plates,he former beeing responsible for Pyrenean-Provence deformationsnd the latter for Alpine episodes. However, we observe that partf N-S to NW-SE shortening in the southern foreland of the westernlpine arc actually relates to the early stages of the Adria–Europeollision, because it post-dates the onset of flexural loading ofhe European foreland by the Austro-Alpine wedge. Top-to-theorthwest direction of propagation of the collisional thrust stackuring the Eocene-earliest Oligocene time span (Fig. 12) is docu-ented by both near-surface evidence in the Paleogene flexural

asin, such as synsedimentary folding, gravity sliding and subma-ine slope scar, and upper crustal deformation in the Dauphinéxternal basement. During the same period, HP-LT deformationithin the palaeo-accretionary prism occurred mainly in a north-ard propagating setting, as documented by published kinematicata from the internal arc (Fig. 6, right). The diachroneity of high-ressure ages within the Brianc onnais part of the subducted plateFig. 6, middle) is best explained by a continental subduction regimepanning the entire Eocene, coeval with the flexural basin propa-ation. Considering this long lasting north- to NW-directed earlylpine kinematic setting, the elements that were involved in theccretionnary wedge, such as the Brianc onnais continental marginragments, have to be restored to the SE of the future location ofhe western Alpine arc (Fig. 13A). This is consistent with a palaeo-eographic location of the Brianc onnais domain to the east of theberia-Sardinia-Corsica microplate (e.g. Stampfli et al., 1998, 2002).

A complete renewal of the tectonic setting occurred close tohe Eocene-Oligocene boundary, initiating a mature stage of colli-ion with westward escape of the Internal Nappes stack. Accordingo many authors (Ziegler, 1989; Stampfli et al., 2002; Collombett al., 2002; Rosenbaum and Lister, 2005; Ford et al., 2006; Molli,008), the formation of the western Alpine arc occurred mainlyfter the Eocene, that is during this mature stage of collision withateral extrusion. The deep part of the paleo-accretionnary wedge,aving migrated northwards during the previous, continental sub-uction stage, was then cross-cut and thrust westwards over themerged proximal part of the flexural basin, allowing a metamor-hic rocks provenance for the synorogenic sediments during thearly Oligocene, a scenario which is summarized in Figs. 12 and 13.ccording to us, and following Ford et al. (2006), this scenario pro-ides the best explanation for the two-stages deformation historynd interference structures observed in the external zone.

The Oligocene westward escape of the Internal Alps indenteras kinematically linked with the dextral motion along the Insubric

ault to the north (Schmid et al., 1987) and with an expected conju-ate sinistral shear zone to the south, from which the recent “Sturaouloir” (Giglia et al., 1996) could derive. The lithospheric scalendenter is cored by Adriatic lithospheric mantle of the Ivrea bodyLardeaux et al., 2006). Thus, from the Early Oligocene onwardsFig. 13D), the northern part of Adria was translated westwards,ndenting the accretionary buildup derived from the previous con-inental subduction stage in between the western Alpine forelandnd the uplifted western limit of the Adriatic lithosphere. In frontf the Ivrea indenter, the “Piemont Schistes lustrés” fossil accre-ionary wedge therefore suffered E-W ductile to brittle extensionalhear during exhumation and tilting (Schwartz et al., 2009).

This two-stage model elucidates the discrepancy betweenhe present structure of recent “hypercollision” dynamics of the

estern Alpine arc, on the one hand, and the partly strike-slipontinental subduction belt developed previously on the west-rn edge of the northward-moving Adriatic microplate (Ricou andiddans, 1986), on the other. The initiation of the arc would have

namics 56– 57 (2012) 18– 38

been localised at the western termination of the Eocene flexuralbasin (Fig. 13B and C). The Adria upper plate, responsible for flex-ural loading, did not extend westwards farther than the presentlocation of the Ligurian Alps (Fig. 13B and C), involving the occur-rence of a major N-S sinistral transform boundary that we proposeto name Western Adria Transform Zone (WATZ; Fig. 13A). Con-sidering the interpretations of Durand-Delga and Rossi (2002),Faccenna et al. (2004) or Vignaroli et al. (2008), the longitudinallocation of this boundary corresponded with a subduction polar-ity reversal of the Tethyan oceanic lithosphere, from NW-dippingbeneath the Iberia-Sardinia-Corsica block to SE-dipping beneathAdria. As initially proposed by Ricou and Siddans (1986), sucha sinistral transform boundary allowed the Brianc onnais domainto be detached from the Corsica-Provence realm and transportednorthwards. The northward propagation of Adria along this bound-ary produced initial thrusting of the oceanic accretionary wedge(so-called Piedmont Schistes lustrés) over the distal European mar-gin, namely the Piedmont and internal Brianc onnais domains, thenthe gradual involvement of Brianc onnais fragments in the Tethyansubduction zone, contemporaneously with the closure of the Valaisocean further north (Handy et al., 2010). This northward motion ofAdria provided the superposition of Adriatic and European litho-spheric mantles, a duplication that is well documented in theWestern Alps (Lardeaux et al., 2006).

The Oligocene Western Alpine evolution resulted primarily inthe combined effects of two related dynamic processes: (i) west-ward indentation (combined with anticlockwise rotation; Channel,1996) of previously uplifted Adriatic lithospheric mantle to thenorth (Ivrea body) and (ii) SE- to E-directed incipient Apenninicthrusting to the south, probably driven by slab roll-back beneaththe Corsica-Sardinia-Provence realm suffering back-arc extension(Faccenna et al., 2004). The contrasting evolution of these twodomains led to strain partitioning and the necessary developmentof strike-slip boundaries (Giglia et al., 1996; Malusà et al., 2009).The Ivrea body, which has been extensively investigated using geo-physical methods (Roure et al., 1996; Schreiber et al., 2010 andreferences herein) and which outcrops at the western termina-tion of the Southern Alps (Siegesmund et al., 2008), is an Adriaticlithospheric mantle and crustal fragment overthrusting the Euro-pean Moho. The lower crustal section yielded Eocene ZFT ages(Siegesmund et al., 2008) which mark the N-directed thrustingstage (Handy et al., 1999) over the oceanic (Sesia) and continentalEuropean crust (Brianc onnais) during the continental subductionstage. The western boundary of the Ivrea body, corresponding tolithospheric mantle, trends approximately N-S beneath the south-ern part of the Western Alpine arc (Waldhauser et al., 2002; Kisslinget al., 2006; Lardeaux et al., 2006), that is in strong discrepancy withthe present arc shape. We propose that this N-S boundary whichappears roughly rectilinear at ∼15 km depth (Vernant et al., 2002;Schreiber et al., 2010) could be a relict of the western transformboundary of Adria during northward Eocene drift (WATZ, Fig. 13).The westward motion of this presumably inherited Adria inden-ter was accommodated by dextral shear along the Periadriatic lineas soon as earliest Oligocene (Schmid et al., 1987; Handy et al.,2005), with possibly a conjugate sinistral shear zone to the south(Giglia et al., 1996). It produced fast exhumation of the Eocenepaleo-accretionnary wedge, together with a dramatic increase inaltitude and erosion rates. This exhumation is recorded withinthe lower Oligocene molasse basins on both sides of the renewedrelief, sourced from high-pressure metamorphic rocks and oceanicmélanges of various metamorphic grades. The curvature of the arcwas progressively acquired, producing radial spreading of transport
lineations (Choukroune et al., 1986; Platt et al., 1989b; Lickorishet al., 2002) and southward increasing counter-clockwise rotationsof internal units (Collombet et al., 2002). The southern part of thearc now cross-cuts perpendicularly the paleo-accretionary wedge.

eody

Te(T

mfsme(hSMdi

A

R

R

A

A

A

A

A

A

B

B

B

B

B

B

B

B

B

B

B


he effects of Oligocene indentation were enhanced at the south-rn termination of the arc by the onset of Corsica-Sardinia riftingGuennoc et al., 2000) due to rollback of the NW-ward subductedethyan lithosphere (Faccenna et al., 2004; Jolivet et al., 2009).

The driving mechanism that produced this sharp change in theode of accommodation of Africa–Europe convergence in the Alps,

rom continental subduction to collision with lateral extrusion, istill debated. There is little evidence for any change in relativeotion between Africa and Europe (Dewey et al., 1989; Rosenbaum

t al., 2002) but a motion change is recorded by Adria 35 Ma agoe.g. Handy et al., 2010). This renewal in Alpine kinematics mustave been enhanced by the change of the subduction polarity fromE to NW in the Ligurian oceanic domain (Rosenbaum et al., 2002;ichard et al., 2006; Handy et al., 2010) and by the subsequent E-

irected rollback of the eastern Ligurian oceanic domain and thencipient Mediterranean dynamics.

cknowledgement

This work was supported by the Agence Nationale pour laecherche grant “ERD-Alps”.

eferences

gard, P., Jolivet, L., Goffé, B., 2001. Tectonometamorphic evolution of the SchistesLustrés complex: implications for the exhumation of the HP and UHP rocks inthe western Alps. Bull. Soc. Géol. France 172, 617–636.

maudric du Chaffaut, S., 1982. Les unités alpines à la marge orientale du massifcristallin corse. Doctorate thesis. Trav. Lab. Géologie Ecole Normale Supérieure,15, Paris, 133 pp.

rnaud, H., Gidon, M., Pairis, J.L., 1978. Dislocations synsédimentaires du socle etdéformations ultérieures de la couverture: l’exemple des chaînons subalpins auNE de Sisteron. C. R. Acad. Sci. Paris 287, 787–790.

rtoni, A., Meckel, L.D., 1998. History and deformation rates of a thrust sheettop basin; the Barrême basin, Western Alps, SE France. Geol. Soc. Lond. Spec.,213–237, Publication no. 134.

ubourg, C., Rochette, P., Stéphan, J.F., Popoff, M., Chabert-Pelline, C., 1999. The mag-netic fabric of weakly deformed Late Jurassic shales from the southern subalpinechains (French Alps): evidence for SW-directed tectonic transport direction.Tectonophysics 307, 15–31.

uthemayou, C., 2002. Géométrie tridimentionnelle et tectonique de raccourcisse-ment Nord-Sud dans le Massif du Pelvoux. Unpublished DEA. Université JosephFourier, Grenoble, 36 pp.

adertscher, N., Burkhard, M., 1998. Inversion alpine du graben Permo-Carbonifèrede Salvan-Dorénaz et sa relation avec le chevauchement de la nappe de Morclessus-jacente. Eclogae Geol. Helv. 91, 359–373.

arbier, R., Barféty, J.C., Bocquet, A., Bordet, P., Le Fort, P., Meloux, J., Mouterde, R.,Pêcher, A., Petiteville, M., 1973. Carte géologique de la France au 1/50000è, feuilleLa Grave. Bur. Rech. Geol. Min. Orléans.

arféty, J.C., 1988. Le Jurassique dauphinois entre Durance et Rhône. Etude strati-graphique et géodynamique. Documents du Bureau de Recherches géologiqueset minières, Orléans 131, 655.

arféty, J.C., Gidon, M., 1983. La stratigraphie et la structure de la couverturedauphinoise au Sud de Bourg d’Oisans. Leurs relations avec les déformationssynsédimentaires jurassiques. Géol. Alpine 59, 5–32.

arféty, J.C., Tricart, P., Jeudy De Grissac, C., 1992. La quatrième écaille près deBrianc on (Alpes franc aises): un olistostrome précurseur de l’orogenèse pen-nique éocène. C. R. Acad. Sci. Paris 314, 71–76.

audin, T., Marquer, D., Persoz, F., 1993. Basement–cover relationships in the Tambonappe (Central Alps, Switzerland): geometry, structure and kinematics. J. Struct.Geol. 15, 543–553.

eck, C., Deville, E., Blanc, E., Philippe, Y., Tardy, M., 1998. Horizontal shorteningcontrol of middle Miocene marine siliciclastic accumulation (Upper MarineMolasse) in the southern termination of the Savoy Molasse Basin (northwesternAlps/southen Jura). Geol. Soc. Lond. Spec. Publ. 134, 263–278.

erger, J.P., Bousquet, R., 2008. Subduction-related metamorphism in the Alps:review of isotopic ages based on petrology and their geodynamic consequences.Geol. Soc. Lond. Spec., 117–144, Publication no. 298.

erggren, W.A., Kent, D.V., Swisher, C.C., Aubry, M.P., 1995. A revised Cenozoicgeochronology and chronostratigraphy. In: Berggren, W.A., Kent, D.V., Aubry,M.P., Hardenbol, J. (Eds.), Geochronology, Time Scale and Global StratigraphicCorrelations, vol. 54. SEPM Special Publication, pp. 129–212.

ernet, M., Tricart, P., 2010. The Oligocene orogenic pulse in the Southern Pen-ninic Arc (Western Alps): structural, sedimentary and thermochronological
constraints. Bull. Soc. Géol. Fr. 182, 25–36.
ertotti, G., Mosca, P., Juez, J., Polino, R., Dunai, T., 2006. Oligocene to present kilo-metres scale subsidence and exhumation of the Ligurian Alps and the TertiaryPiedmont Basin (NW Italy) revealed by apatite (U–Th)/He thermochronology:correlation with regional tectonics. Terra Nova 18, 18–25.

namics 56– 57 (2012) 18– 38 35

Bigot-Cormier, F., Poupeau, G., Sosson, M., 2000. Dénudations différentielles du mas-sif cristallin externe Alpin de l’Argentera (Sud-Est de la France) révélées parthermochronologie traces de fission (apatites, zircons). C. R. Acad. Sci. Paris 330,363–370.

Bogdanoff, S., Michard, A., Mansour, M., Poupeau, G., 2000. Apatite fission track anal-ysis in the Argentera massif: evidence of contrasting denudation rates in theExternal Crystalline Massifs of the Western Alps. Terra Nova 12, 117–125.

Bouroullec, R., Cartwright, J.A., Johnson, H.D., Lansigu, C., Quémener, J.M., Savanier,D., 2004. Syndepositional faulting in the Grès d’Annot Formation SE France:high-resolution kinematic analysis and stratigraphic response to growth fault-ing. Geol. Soc. Lond. Spec., 241–265, Publication no. 221.

Bousquet, R., Goffé, B., Vidal, O., Oberhänsli, R., Patriat, M., 2002. The tectono-metamorphic history of the Valaisan domain from the Western to the CentralAlps: new constraints on the evolution of the Alps. GSA Bull. 114, 207–225.

Bousquet, R., Oberhänsli, R., Goffe, B., Wiederkehr, M., Koller, F., Schmid, S., Schuster,R., Engi, M., Berger, A., Martinotti, G., 2008. Metamorphism of metasediments atthe scale of an orogen: a key to the Tertiary geodynamic evolution of the Alps.Geol. Soc. Lond. Spec., 393–411, Publication no. 298.

Bravard, C., 1982. Données nouvelles sur le stratigraphie et la tectonique de la zonesdes Aiguilles d’Arves au nord du col du Lautaret. Géol. Alpine Grenoble 58, 5–13.

Bravard, C., Gidon, M., 1979. La structure du revers oriental du Massif duPelvoux: Observations et interprétations nouvelles. Géologie Alpine t.55,23–33.

Broucke, O., Guillocheau, F., Robin, C., Joseph, P., Calassou, S., 2004. The influenceof syndepositional basin floor deformation on the geometry of turbiditic sand-stones: a reinterpretation of the Cote de L’Ane area (Sanguiniere-Restefondssub-Basin, Gres d’Annot, Late Eocene, France). Geol. Soc. Lond. Spec. Publ. 221,203–222.

Bucher, S., Ulardic, C., Bousquet, R., Ceriani, S., Fügenschuh, B., Gouffon, Y.,Schmid, S., 2004. Tectonic evolution of the Brianc onnais units along a transect(ECORS-CROP) through the Italian–French Western Alps. Eclogae Geol. Helv. 97,321–345.

Bürgisser, J., Ford, M., 1998. Overthrust shear deformation of a foreland basin; struc-tural studies south-east of the Pelvoux massif, SE France. J. Struct. Geol. 20,1455–1475.

Butler, R.W.H., 1992. Thrust zone kinematics in a basement-cover imbricate stack:Eastern Pelvoux massif, French Alps. J. Struct. Geol. 14, 29–40.

Butler, R.W., McCaffrey, H.W.D., 2004. Nature of thrust zones in deep water sand-shale sequences: outcrop examples from the Champsaur sandstones of SEFrance. Mar. Petr. Geol. 21, 911–921.

Caby, R., 1973. Les plis transversaux dans les Alpes occidentales: implications pour lagenèse de la chaîne alpine. Bull. Soc. Géol. France 15, 624–634.

Callec, Y., 2001. La déformation synsédimentaire des bassins paléogènes de l’arc deCastellane (Annot, Barrême, Saint-Antonin). Mémoire Sciences de la Terre, Ecoledes Mines de Paris, 349, no. 43.

Callec, Y., 2004. The turbidite fill of the Annot sub-basin (SE France): a sequencestratigraphy approach. In: Joseph, P., Lomas, S.A. (Eds.), Deep Water Sedimenta-tion in the Alpine Basin of SE France, Geol. Soc. Spec. Publication no. 221. , pp.111–135.

Campredon, R., 1977. Les formations paléogènes des Alpes maritimes franco-italiennes. Memoire H. S. Soc. Geol., France, 199 pp.

Campredon, R., Giannerini, G., 1982. Le synclinal de St Antonin (arc de Castellane,Chaînes subalpines méridionales); un exemple de bassin soumis à une déforma-tion compressive permanente depuis l’Eocène supérieur. Géol. Alpine Grenoble58, 15–20.

Capitanio, F.A., Goes, S., 2006. Mesozoic spreading kinematics: consequences forCenozoic Central and Western Mediterranean subduction. Geophys. J. Int. 165,804–816.

Caron, C., Homewood, P., Morel, R., Stuijvenberg, J., 1980. Témoins de la nappedu Gurnigel sur les Préalpes médianes: une confirmation de son origineultrabrianc onnaise. Bull. Soc. Fribourgeoise Sc. Nat. 69, 64–79.

Carrapa, B., Di Giulio, A., Wijbrans, J., 2004. The early stages of the Alpine colli-sion: an image derived from the upper Eocene-lower Oligocene record in theAlps–Apennines junction area. Sediment. Geol. 171, 181–203.

Carry, N., 2007. De la subduction continentale à l’exhumation dans les Alpes pen-niques. PhD thesis. University of Rennes, 307 pp.

Ceriani, S., Fügenschuh, B., Schmidt, S., 2001. Multi-stage thrusting at the “PenninicFront” in the Western Alps between Mont Blanc and Pelvoux massifs. Geol. Rund.90, 685–702.

Ceriani, S., Schmid, S., 2004. From N–S collision to WNW-directed post-collisionalthrusting and folding: Structural study of the Frontal Penninic Units in Savoie(Western Alps, France). Eclogae Geol. Helv. 97, 347–369.

Channel, J.E.T., 1996. Paleomagnetism and Paleogeography of Adria. Geol. Soc. Lond.Spec. Publ. 105, 119–132.

Chauveau, J.C., Lemoine, M., 1961. Contribution à l’étude géologique du synclinaltertiaire de Barrême (moitié nord). Bull. Serv. Carte géol France 58, 287–318.

Chevalier, F., Guiraud, M., Garcia, J.P., Dommergues, J.L., Quesne, D., Allemand, P.,Dumont, T., 2003. Calculating the long-term displacement rates of a normalfault from the high-resolution stratigraphic record (early Tethyan rifting, FrenchAlps). Terra Nova 15, 410–416.

Choukroune, P., Ballevre, M., Cobbold, P., Gautier, Y., Merle, O., Vuichard, J.P.,
1986. Deformation and motion in the Western Alpine arc. Tectonics 5,215–226.
Cibin, U., Di Giulio, A., Martelli, L., 2003. Oligocene-Early Miocene tectonic evolutionof the northern Apennines (northwestern Italy) traced through provenance ofpiggy-back basin fill successions. Geol. Soc. Lond. Spec., 269–287, Publ. No. 208.

3 eody

C

C

C

C

C

C

D

D

D

D

D

D

D

D

D

D

D

D

D

E

E

E

E

E

F

F

F


liff, R.A., Barnicoat, A.C., Inger, S., 1998. Early Tertiary eclogite facies metamorphismin the Monviso Ophiolite. J. Metamorphic Geol. 16, 447–455.

ollombet, M., Thomas, J.C., Chauvin, A., Tricart, P., Bouillin, J.P., Gratier, J.P., 2002.Counterclockwise rotation of the western Alps since the Oligocene: new insightsfrom paleomagnetic data. Tectonics, doi:10.1029/2001TC901016.

orsini, M., Ruffet, G., Caby, R., 2004. Alpine and late Hercynian geochronologi-cal constraints in the Argentera massif (Western Alps). Eclogae Geol. Helv. 97,3–15.

ouëffé, R., Maridet, O., 2003. Découverte de deux gisements à micromammifèresdu Burdigalien supérieur dans la molasse du bassin de Digne (Alpes de HauteProvence, SE France): implications stratigraphiques et tectoniques. Eclogae Geol.Helv. 96, 197–207.

ourel, L., et al., 1984. Trias. In: Debrand-Passard, S., Courbouleix, S., Lienhardt, M.J.(Eds.), Synthèse géologique du Sud-Est de la France, Mémoire Bur. Rech. Géol.Min. No. 125. , pp. 61–117.

respo-Blanc, A., Masson, H., Sharp, Z., Cosca, M., Hunziker, J., 1995. A stable and40Ar–39Ar isotope study of a major thrust in the Helvetic nappes (Swiss Alps):evidence for fluid flow and constraints on nappe kinematics. GSA Bull. 107,1129–1144.

al Piaz, G., 2001. Geology of the Monte Rosa massif: historical review and personalcomments. Schweiz. Min. Petrogr. Mitt. 81, 275–303.

ebelmas, J., Durozoy, G., Kerckhove, C., Monjuvent, G., Mouterde, R., Pêcher, A.,1980. Notice de la carte géologique de la France au 1/50000è, feuille Orcières.Bur. Rech. Géol. Min. Orléans, 27.

e Graciansky, P.C., Roberts, D.G., Tricart, P., 2010. The Western Alps, from rift to pas-sive margin to orogenic belt. An integrated geoscience overview. Developmentin Earth Surface Processes, vol. 14. Elsevier, 429 pp.

ewey, J.F., Helman, M.L., Turco, E., Hutton, D.H.W., Knott, S.D., 1989. Kine-matics of the western Mediterranean. In: Coward, M.P., Dietrich, D.,Park, R.G. (Eds.), Alpine Tectonics, Geol. Soc. Spec. Publication No. 45. ,pp. 265–283.

èzes, P., Schmid, S., Ziegler, P.A., 2004. Evolution of the European Cenozoic RiftSystem: interaction of the Alpine and Pyrenean orogens with their forelandlithosphere. Tectonophysics 389, 1–33.

i Giulio, A., Carrapa, B., Fantoni, R., Gorla, L., Valdisturlo, A., 2001. MiddleEocene to Early Miocene sedimentary evolution of the Lombardian segmentof the South Alpine foredeep (Italy). Int. J. Earth Sci. (Geol. Rundsch.) 90,534–548.

ommergues, J.L., Guiffra, A., Dumont, T., Chevalier, F., 2011. La Lumachelle àCardinia (Bivalves) et Alsatites (Ammonites) du Revers de Cote Dure dansl’Hettangien de la couverture sédimentaire du Massif du Rochail (Oisans, Isère,France). Revue de Paléobiologie, Genève 30, 193–221.

uchêne, S., Blichert-Toft, J., Luais, B., Télouk, P., Lardeaux, J.M., Albarède, F., 1997.The Lu–Hf dating of garnets and the ages of the Alpine high-pressure metamor-phism. Nature 367, 586–589.

u Fornel, E., Joseph, P., Desaubliaux, G., Eschard, R., Guillocheau, F., Lerat, O., Muller,C., Ravenne, C., Sztrakos, K., 2004. The southern Grès d’Annot outcrops (FrenchAlps): an attempt at regional correlation. In: Joseph, P., Lomas, S.A. (Eds.), DeepWater Sedimentation in the Alpine Basin of SE France. Geol. Soc. Spec. Publica-tion No. 221, pp. 137–160.

umont, T., 1998. Sea-level changes and early rifting of a European Tethyan marginin the western Alps and Southeastern France. In: de Graciansky, P.C., Hardenbol,J., Jacquin, T., Vail, P.R. (Eds.), Mesozoïc and Cenozoic Sequence Stratigraphyof European Basins. Society of Economic Petrologists and Mineralogists, pp.623–642, Special Publication 60.

umont, T., Champagnac, J.D., Crouzet, C., Rochat, P., 2008. Multistage shortening inthe Dauphiné zone (French Alps): the record of Alpine collision and implicationsfor pre-Alpine restoration. Swiss J. Geosci. 101, 89–110.

umont, T., Simon-Labric, T., Authemayou, C., Heymes, T. Lateral termination ofthe north-directed Alpine orogeny and onset of westward escape in the West-ern Alpine arc: structural and sedimentary evidence from the external zone.Tectonics, in press.

urand-Delga, M., Rossi, P., 2002. About the Ligurian-Piemontese Ocean on thetransect Corsica-Apennines. C. R. Geosci. 334, 227–228.

gal, E., 1992. Structure and tectonic evolution of the external zone of Alpine Corsica.J. Struct. Geol. 14, 1215–1228.

ngi, M., Scherrer, N.C., Burri, T., 2001. Metamorphic evolution of pelitic rocks of theMonte Rosa nappe: constraints from petrology and simple grain monazite agedata. Schweiz. Min. Petrogr. Mitt. 81, 305–328.

uzen, T., Joseph, P., Du Fornel, E., Lesur,.S., 2004. Three-dimensional stratigraphicmodelling of the Gres d’Annot system, Eocene-Oligocene, SE France. Geol. Soc.London Spec. Publ. 221, 161–180.

vans, M.J., Eliott, T., 1999. Evolution of a thrust-sheet-top basin: the TertiaryBarrême Basin, Alpes de Haute Provence, France. Geol. Soc. Am. Bull. 111,1617–1643, Springer, Berlin, pp. 185–206.

vans, M.J., Mange-Rajetsky, M.A., 1991. The provenance of sediments in the Bar-rême thrust-top basin, Haute Provence, France. Geol. Soc. Spec. Publication No.57, 323–342.

accenna, C., Piromallo, C., Crespo-Blanc, A., Jolivet, L., Rossetti, F., 2004. Lateral slabdeformation and the origin of the western Mediterranean arcs. Tectonics 23,TC1012, 21 pp.

ischer, H., Villa, I.M., 1990. Erste K/Ar- und (super 40)Ar/(super 39)Ar- Hornblende-Mineralalter des Taveyannaz-Sandstein. Schweitz. Miner. Petrol. Mitt. 70,73–75.

ord, M., 1996. Kinematics and geometry of early Alpine, basement involved folds,SW Pelvoux Massif, SE France. Eclogae Geol. Helv. 89, 269–295.

namics 56– 57 (2012) 18– 38

Ford, M., Duchêne, S., Gasquet, D., Vanderhaeghe, O., 2006. Two-phase orogenicconvergence in the external and internal SW Alps. J. Geol. Soc. Lond. 163,1–12.

Ford, M., Lickorish, W.H., Kuznir, N.J., 1999. Tertiary foreland sedimentation in theSouthern Subalpine Chains, SE France: a geodynamic appraisal. Basin Res. 11,315–336.

Freeman, S.R., Butler, R.W., Cliff, R.A., Inger, S., Barnicoat, A.C., 1998. Deforma-tion migration in an orogen-scale zone array: an example from the BasalBrianc onnais Trust, internal Franco-Italian Alps. Geol. Mag. 135, 349–367.

Freeman, S.R., Inger, S., Butler, R.W., Cliff, R.A., 1997. Dating deformation using Rb-Sr in white mica: greenschist-facies deformation ages from Entrelor shear zone,Italian Alps. Tectonics 16, 57–76.

Froitzheim, N., Schmid, S.M., Conti, P., 1994. Repeated change from crustal shorten-ing to orogenparallel extension in the Austroalpine units of Graubunden. EclogaeGeol. Helv. 87/2, 559–612.

Fügenschuh, B., Schmid, S., 2003. Late stages of deformation and exhumation of anorogen constrained by fission-track data: a case study in the Western Alps. GSABull. 115, 1425–1440.

Gamond, J.F., 1980. Direction de déplacement et linéation: cas de la couverturesédimentaire dauphinoise orientale. Bull. Soc. Géol. France 1984 22 (7), 429–436.

Gebauer, D., 1999. Alpine geochronology of the Central and Western Alps: new con-straints for a complex geodynamic evolution. Schweiz. Miner. Petrogr. Mitt. 79,191–208.

Gidon, M., 1979. Le rôle des étapes successives de déformation dans la tectoniquealpine du massif du Pelvoux (Alpes occidentales). C. R. Acad. Sci. Paris 288,803–806.

Gidon, M., Buffet, G., Bonhomme, M., Montjuvent, G., Fourneaux, J.C., Mouterde, R.,1980. Carte géologique de la France au 1/50000è, feuille 845, St Bonnet. Bur.Rech. Geol. Min.

Gidon, M., Pairis, J.L., 1980. Nouvelles données sur la structure des écailles de SoleilBoeuf (bordure sud du massif du Pelvoux). Bull. Bur. Rech. Geol. Min. 1, 35–41.

Giger, M., Hurford, A.J., 1989. Tertiary intrusives of the Central Alps: their Tertiaryuplift, erosion, redeposition and burial in the south-alpine foreland. EclogaeGeol. Helv. 82, 857–866.

Giglia, G., Capponi, G., Crispini, L., Piazza, M., 1996. Dynamics and seismotectonicsof the West-Alpine arc. Tectonophysics 267, 143–175.

Gratier, J.P., Ménard, G., Arpin, R., 1989. Strain–displacement compatibility andrestoration of the Chaînes Subalpines of the western Alps. In: Coward, M.P.,Dietrich, D., Park, R.G. (Eds.), Alpine Tectonics. , pp. 65–81, Spec. Pub. No. 45.

Guardia, P., Ivaldi, J.P., 1987. Contrôle tectonique de la sédimentation paléogène surle bord méridional du massif de l’Argentera (Alpes Maritimes). Géologie Alpine,Grenoble, mém. H.S No. 13, 343–356.

Gubler-Wahl, Y., 1928. La nappe de l’Ubaye au sud de la vallée de Barcelonnette.Thèse. Paris, 201.

Guellec, S., Mugnier, J.L., Tardy, M., Roure, F., 1990. Neogene evolution of the westernAlpine foreland in the light of Ecors data and balanced cross-section. In: Mem.Soc. Géol. France No. 156, pp. 165–184.

Guennoc, P., Gorini, C., Mauffret, A., 2000. Histoire géologique du Golfe du Lion etcartographie du rift oligo-aquitanien et de la surface messinienne. Géologie dela France 3, 67–97.

Guerrot, C., Debon, F., 2000. U–Pb zircon dating of two contrasting Late Variscanplutonic suites from the Pelvoux massif (French Western Alps). Schweiz Min.Petrogr. Mitt. 80, 249–256.

Guillot, S., Di Paola, S., Ménot, R.P., Ledru, P., Spalla, M.I., Gosso, G., Schwartz, S., 2009.Suture zones and importance of strike-slip faulting for Variscan geodynamicreconstructions of the External Crystalline Massifs of the western Alps. Bull.Soc. Géol. France 180, 483–500.

Gupta, S., Allen, P.A., 2000. Implications of foreland paleotopography for strati-graphic development in the Eocene distal Alpine foreland basin. GSA Bull. 112,515–530.

Haccard, D., Beaudouin, B., Gigot, P., Jorda, M., 1989. Notice explicative de la cartegéologique de France (1/50000), feuille La Javie (918). Bur. Rech. Géol. Min.Orléans, 152.

Handy, M., Babist, J., Wagner, R., Rossenberg, G., Konrad, M., 2005. Decoupling andits relation to strain partitioning in continental lithosphere: insight from thePeriadriatic fault system (European Alps). Geol. Soc. London Spec. Publ. 243,249–276.

Handy, M.R., Franz, L., Heller, F., Janott, B., Zurbriggen, R., 1999. Multistage accretionand exhumation of the continental crust (Ivrea crustal section, southern Alps,northwestern Italy and southern Switzerland. Geol. Soc. Am. Bull. 103, 236–253.

Handy, M., Schmid, S.M., Bousquet, R., Kissling, E., Bernouilli, D., 2010. Reconcilingplate-tectonic reconstructions of Alpine Tethys with the geological–geophysicalrecord of spreading and subduction in the Alps. Earth Sci. Rev. 102, 121–158.

Hardenbol, J., Thierry, J., Farley, M.B., Jacquin, T., de Graciansky, P.C., Vail, P., 1998.Mesozoic and Cenozoic sequence stratigraphic framework of European ba. In: deGraciansky, P.C., Hardenbol, J., Jacquin, T., Vail, P. (Eds.), Mesozoic and CenozoicSequence Stratigraphy of European Basins. Soc. Econ. Min. Petr. Spec. Publ. 60. ,pp. 3–14.

Ivaldi, J.P., 1987. Le Paléogène détritique marin du pays des Arves (Savoie): analysepar thermoluminescence et paléogéographie. Géologie Alpine, Grenoble, mém.H.S No. 13, 343–356.

Jean, S., 1985. Les grès d’Annot au NW du massif de l’Argentera-Mercantour. Unpub-lished PhD thesis. University of Grenoble, 244.

Jeanbourquin, P., Goy-Eggenberger, D., 1991. Mélanges suprahelvétiques: sédimen-tation et tectonique au front de la nappe de Morcles (Vaud, Suisse). GéologieAlpine 67, 43–62.

http://dx.doi.org/10.1029/2010TC002836

eody

J

J

K

K

K

K

K

K

K

K

K

K

K

K

L

L

L

L

L

L

L

L

L

L

L

L

L


olivet, L., Faccenna, C., Piromallo, C., 2009. From mantle to crust: stratching theMediterranean. Earth Planet. Sci. Lett. 285, 198–209.

oseph, P., Lomas, S., 2004. Deep-water sedimentation in the Alpine foreland basinof SE France: new perspectives on the Grès d’Annot. An introduction. Geol. Soc.Lond. Spec. Publ. 221, 1–16.

eller, L.M., Hess, M., Fügenschuh, B., Schmid, S., 2005. Structural and meta-morphic evolution of the Camughera-Moncucco, Antrona and Monte Rosaunits southwest of the Simplon line, Western Alps. Eclogae Geol. Helv. 98,19–49.

eller, L.M., Schmid, S., 2001. On the kinematics of shearing near the top of the MonteRosa nappe and the nature of the Furgg zone in the Val Loranco (Antrona valley,N. Italy): tectonometamorphic and paleogeographical consequences. Schweiz.Min. Petrogr. Mitt. 81, 347–367.

empf, O., Pfiffner, O.A., 2004. Early Tertiary evolution of the North Alpine ForelandBasin of the Swiss Alps and adjoining areas. Basin Res. 16, 549–567.

empf, O., Pross, J., 2005. The lower marine to lower freshwater Molassetransition in the northern Alpine foreland basin (Oligocene; central Switzerland-south Germany): age and geodynamic implications. Int. J. Earth Sci. 94,160–171.

erckhove, C., 1964. Mise en évidence d’une série à caractère d’ « olistostrome» au sommet des grès d’Annot (Nummulitique autochtone) sur le pourtourdes nappes de l’Ubaye (Alpes franco-italiennes). C. R. Acad. Sci. Paris 259,4742–4745.

erckhove, C., 1969. La Zone du Flysch dans les nappes de l’Embrunais-Ubaye (Alpesoccidentales). Géologie Alpine, Grenoble 45, 5–204.

erckhove, C., 1974. Notice explicative de la Carte géologique de France au 1/50000è,feuille Barcelonnette (895). Bur. Rech. Géol. Min. Orléans.

erckhove, C., Cochonat, P., Debelmas, J., 1978. Tectonique du soubassementparautochtone des nappes de l’Embrunais-Ubaye sur leur bordure occidentale,du Drac au Verdon. Géologie Alpine, Grenoble 54, 67–82.

erckhove, C., Thouvenot, F., 2008. Notice explicative de la Carte géologique deFrance au 1/50 000è, feuille Allos (919), deuxième édition. Bur. Rech. Géol. Min.,Orléans.

issling, E., Schmid, S., Lippitsch, R., Ansorge, J., Fügenschuh, B., 2006. Litho-sphere structure and tectonic evolution of the Alpine arc: new evidence fromhigh-resolution teleseismic tomography. In: Gee, D.G., Stephenson, R.A. (Eds.),European Lithosphere Dynamics, vol. 32. Geol. Soc. London Memoirs, pp.129–145.

uhlemann, J., 2000. Post-collisional sediment budget of circum-Alpine basins (Cen-tral Europe). Mem. Sci. Geol. Padova 52, 1–91.

urz, W., Neubauer, F., Genser, J., 1996. Kinematics of Penninic nappes (Glock-ner Nappe and basement-cover nappes) in the Tauern Window (Eastern Alps,Austria) during subduction and Penninic-Austroalpine collision. Eclogae Geol.Helv. 89, 573–605.

acombe, O., Jolivet, L., 2005. Structural and kinematic relationships between Cor-sica and the Pyrenees-Provence domain at the time of the Pyrenean orogeny.Tectonics 24, 1–20.

abaume, P., Jolivet, M., Souquière, F., Chauvet, A., 2008. Tectonic control on diagene-sis in a foreland basin: combined petrologic and thermochronologic approachesin the Grès d’Annot basin (Late Eocene–Early Oligocene, French–Italian externalAlps). Terra Nova 20, 95–101.

ahondère, D., Rossi, P., Lahondère, J.C., 1999. Structuration alpine d’une margecontinentale externe: le massif du Tenda (Haute-Corse). Implications géody-namiques au niveau de la transversale Corse-Apennins. Géologie de la France 4,27–44.

anteaume, M., 1990. Notice explicative de la Carte géologique de France au1/50000è, feuille Viève-Tende (948). Bur. Rech. Géol. Min., Orléans, 129.

apen, T.J., Johnson, C.M., Baumgrtner, L.P., Dal Piaz, G.V., Skora, S., Beard, B.L., 2007a.Coupling of oceanic and continental crust during Eocene eclogite-facies meta-morphism: evidence from the Monte Rosa nappe, Western Alps, Italy. Contrib.Mineral. Petrol. 153, 139–157.

apen, T.J., Johnson, C.M., Beard, B.L., 2007b. Lu–Hf age and isotope systematics ofthe Dora Maira nappe, western Alps. Goldschmidt Conf. Abstr. 2007, A544.

ardeaux, J.M., Schwartz, S., Tricart, P., Paul, A., Guillot, S., Béthoux, N., Masson, F.,2006. A crustal-scale cross-section of the southwestern Alps combining geo-physical and geological imagery. Terra Nova 18 (6), 412–422.

ateltin, O., Müller, D., 1987. Evolution paléogéographique du bassin des grès deTaveyannaz dans les Aravis (Haute Savoie) à la fin du Paléogène. Eclogae Geol.Helv. 80, 127–140.

e Bayon, B., Ballèvre, M., 2006. Deformation history of a subducted continental crust(Gran Paradiso, Western Alps): continuing crustal shortening during exhuma-tion. J. Struct. Geol. 28, 793–815.

eloup, P.H., Arnaud, N., Sobel, E.R., Lacassin, R., 2005. Alpine thermal and structuralevolution of the highest external crystalline massif: the Mont Blanc. Tectonics24, TC4002, 26.

emoine, M., 1972. Rythme et modalité des plissements superposés dans les chaînessubalpines méridionales des Alpes occidentales franc aises. Geol. Runschau 61,975–1010.

emoine, M., Bas, T., Arnaud-Vanneau, A., Arnaud, H., Dumont, T., Gidon, M., Bour-bon, M., De Graciansky, P.C., Rudckiewicz, J.L., Megard-Galli, J., Tricart, P., 1986.The continental margin of the Mesozoic Tethys in the Western Alps. Marine
Petroleum Geol. 3 (August (86)), 179–199.
emoine, M., Dardeau, G., Delpech, P.Y., Dumont, T., de Graciansky, P.C., Graham,R., Jolivet, L., Roberts, D., Tricart, P., 1989. Extension syn-rift et failles trans-formantes jurassiques dans les Alpes occidentales. C. R. Acad. Sci. Paris 309,1711–1716.

namics 56– 57 (2012) 18– 38 37

Lickorish, W.H., Ford, M., Bürgisser, J., Cobbold, P.R., 2002. Arcuate thrust systemsin sandbox experiments: a comparison to the external arcs of the Western Alps.GSA Bull. 114, 1089–1107.

Lihou, J.C., 1995. A new look at the Blattengratt unit of Eastern Switzerland: earlyTertiary foreland basin sediments from the South Helvetic realm. Eclogae Geol.Helv. 88, 91–114.

Malusà, G.M., Polino, R., Zattin, M., 2009. Strain partitioning in the axial NW Alpssince the Oligocene. Tectonics 28, 1–26.

Malusà, G.M., Polino, R., Zattin, M., Bigazzi, G., Martin, S., Piana, F., 2005. Miocene toPresent differential exhumation in the Western Alps: Insights from fission trackthermochronology. Tectonics 24, TC3004, 23.

Markley, M.J., Teyssier, C., Cosca, M.A., Caby, R., Hunziker, J.C., Sartori, M., 1998.Alpine deformation and 39Ar–40Ar geochronology of synkinematic white micain the Siviez-Mischabel Nappe; western Pennine Alps, Switzerland. Tectonics17, 407–425.

Marroni, M., Feroni, A.C., Di Biase, D., Ottria, G., Pandolfi, L., Taini, A., 2002. Polyphasefolding at upper structural levels in the Borbera Valley (northern Apennines,Italy): implications for the tectonic evolution of the linkage area between Alpsand Apennines. C. R. Géosci. 334, 565–572.

Meckel, L.D., Ford, M., Bernouilli, D., 1996. Tectonic and sedimentary evolution ofthe Dévoluy Basin, a remnant of the Tertiary western Alpine foreland basin, SEFrance. Géologie de la France 2, 3–26.

Meffan-Main, S., Cliff, R.A., Barnicoat, A.C., Lombardo, B., Compagnoni, R., 2004. A Ter-tiary age for Alpine high-pressure metamorphism in the Gran Paradiso massif,Western Alps: a Rb–Sr microsampling study. J. Metam. Geol. 22, 267–281.

Mercier de Lépinay, D., Feinberg, H., 1982. L’olistostrome sommital des grèsdelphino-helvétiques dans la partie nord-occidentale du massif de Platé-Haut-Giffre (Haute Savoie, Alpes occidentales): nature, âge et implications structurales.C. R. Acad. Sci. Paris 294, 1279–1284.

Merle, O., Brun, J.P., 1981. La déformation polyphasée de la nappe du Parpaillon(Flysch à Helminthoïdes): un résultat de la déformation progressive asociée àune translation non rectiligne. C. R. Acad. Sci. Paris t.292, 343–346.

Merle, O., Cobbold, P.R., Schmid, S., 1989. Tertiary kinematics in the Lepontine dome.In: Coward, M.P., Dietrich, D., Park, R.G. (Eds.), Alpine Tectonics, Geol. Soc. Spec.Publication No. 45. , pp. 113–134.

Merle, O., Michon, L., 2001. The formation of the West European rift: a new modelas exemplified by the Massif Central area. Bull. Soc. Géol. Fr. 172, 213–221.

Michard, A., Avigad, D., Goffé, B., Chopin, C., 2004. The high-pressure metamorphicfront of the south Western Alps (Ubaye-Maira transect, France, Italy). Schweiz.Min. Petrogr. Mitt. 84, 215–235.

Michard, A., Dumont, T., Andreani, L., Loget, N., 2010. Cretaceous folding in theDévoluy Mountains (Subalpine Chains, France): gravity-driven detachment atthe European paleomargin versus compressional event. Bull. Soc. Géol. France181, 565–582.

Michard, A., Chalouan, A., Feinberg, H., Goffé, B., Montigny, R., 2002. How does theAlpine belt end between Spain and Morocco? Bull. Soc. Géol. France 173, 3–15.

Michard, A., Negro, F., Saddiqi, O., Bouybaouene, M.L., Chalouan, A., Montigny,R., Goffe, B., 2006. Pressure-temperature-time constraints on the Maghrebidemountain building: evidence from the Rif-Betic transect (Morocco, Spain), Alge-rian correlations, and geodynamic implications. C. R. Géosci. 338, 92–114.

Molli, G., 2008. Northern Apennine-Corsica orogenic system: an updated overview.Geol. Soc. Lond. Special Publ. 298, 413–442.

Monié, P., 1990. Preservation of Hercynian 39Ar–40Ar ages through high-pressurelow-temperature Alpine metamorphism in the Western Alps. Eur. J. Miner. 2,343–361.

Morag, N., Avigad, D., Harlavan, Y., McWilliams, M., Michard, A., 2008. Rapid exhuma-tion and mountain building in the Western Alps: petrology and 40Ar/39Argeochronology of detritus from Tertiary basins of southeastern France. Tectonics27, 1–18.

Mosar, J., Stampfli, G.M., Girod, F., 1996. Western Préalpes Médianes Romandes:timing and structure. A review. Eclogae Geol. Helv. 89, 389–425.

Müller, W., Prosser, G., Mancktelow, N., Villa, I., Kelly, S.P., Viola, G., Oberli, F., 2001.Geochronological constraints on the evolution of the Periadriatic Fault system(Alps). Int. J. Earth Sci. (Geol. Rundsch.) 90, 623–653.

Nagel, T.J., 2008. Tertiary subduction, collision and exhumation recorded in theAdula nappe, central Alps. Geol. Soc. Lond. Special Publ. 298, 365–392.

Padoa, E., 1999. Les ophiolites du massif de l’Inzecca (Corse alpine): lithostratigra-phie, structure géologique et évolution géodynamique. Géologie de la France 3,37–48.

Pairis, J.L., 1988. Paléogène marin et structuration des Alpes occidentales franc aises.Doctorate thesis. Grenoble University, 501.

Pairis, J.L., Campredon, R., Charollais, J., Kerckhove, C., 1984. Paléogène, Alpes. In:Debrand-Passard, S., Courbouleix, S., Lienhardt, M.J. (Eds.), Synthèse géologiquedu Sud-Est de la France, Mémoire Bur. Rech. Géol. Min. No. 125. , pp. 410–415.

Pairis, J.L., Kerckhove, C., 1987. Le flysch de St Clément (Haut Embrunais): unpaléoprisme d’accrétion nummulitique dans la zone subbrianc onnaise. GéologieAlpine, mémoire H.S. 13, 371–378.

Parsy-Vincent, A., 1974. Contribution à l’étude géologique de la partie SW de laBalagne sédimentaire (Corse). Unpublished PhD thesis. Université Paul Sabatier,Toulouse, 101 p.

Pêcher, A., Barféty, J.C., Gidon, M., 1992. Structures est-ouest anténummulitiques à
la bordure orientale du massif des Ecrins-Pelvoux (Alpes franc aises). GéologieAlpine, Grenoble, Série spéciale Résumés 1, 72–73.
Platt, J.P., Behrmann, J.H., Cunningham, P.C., Dewey, J.F., Helman, M., Parrish, M.,Shepley, M.G., Wallis, S., Weston, P.J., 1989a. Kinematics of the Alpine arc andthe motion history of Adria. Nature 337, 158–161.

3 eody

P

P

P

R

R

R

R

R

R

R

R

RR

S

S

S

S

S

S

S

S

S

S

S

S

S

S


latt, J.P., Lister, G.S., Cunningham, P., Weston, P., Peel, F., Baudin, T., Dondey, H.,1989b. Thrusting and backthrusting in the Brianc onnais domain of the westernAlps. In: Coward, M.P., Dietrich, D., Park, R.G. (Eds.), Alpine Tectonics. Geol. Soc.Spec. Pub. No. 45. , pp. 135–152.

olino, R., Ruffini, R., Ricci, B., 1991. Le molasse terziarie della collina di Torino:relazioni con la cinematica alpina. Atti Tic. Sc Terra 34, 85–95.

uigdefabregas, C., Gjelberg, J., Vaksdal, M., 2004. The Gres d’Annot in the Annotsyncline: outer basin-margin onlap and associated soft-sediment deformation.Geol. Soc. Lond. Spec. Publ. 221, 367–388.

avenne, C., Vially, R., Riche, P., Trémolières, P., 1987. Sédimentation et tectoniquedans le bassin marin Eocène supérieur-Oligocène des Alpes du Sud. Rev. Inst.Franc ais du Pétrole 42, 529–553.

eddy, S.M., Wheeler, J., Butler, R.W.H., Cliff, R.A., Freeman, S., Inger, S., Pickles, C.,Kelley, S.P., 2003. Kinematic reworking and exhumation within the convergentAlpine orogen. Tectonophysics 365, 77–102.

icou, L.E., Siddans, A.W.B., 1986. The Western Alps. In: Coward, M.P., Ries, A.C. (Eds.),Collision Tectonics. Geol. Soc. Spec. Publ. 19. , pp. 229–244.

ing, U., 1995. Horizontal contraction or horizontal extension? Heterogeneous LateEocene and Early Oligocene general shearing during blueschist and greenschistfacies metamorphism at the Pennine-Austroalpine boundary zone in the West-ern Alps. Geol. Rundsch. 84, 843–859.

osenbaum, G., Lister, G.S, 2005. The Western Alps from the Jurassic to Oligocene:spatio-temporal constraints and evolutionary reconstructions. Earth Sci. Rev.69, 281–306.

osenbaum, G., Lister, G.S., Duboz, C., 2002. Relative motion of Africa, Iberia andEurope durin the Alpine orogeny. Tectonophysics 359, 117–129.

oure, F., Choukroune, P., Polino, R., 1996. Deep seismic reflection data and newinsights on the bulk geometry of mountain ranges. C. R. Acad. Sci. Paris 322 (2a),345–359.

ubatto, D., Gebauer, D., Compagnoni, R., 1999. Dating of eclogite-facies zircons:the age of Alpine metamorphism in the Sesia-Lanzo zone (Western Alps). EarthPlanet. Sci. Lett. 167, 141–158.

ubatto, D., Hermann, J., 2001. Exhumation as fast as subduction? Geology 29, 3–6.uffini, R., Polino, R., Callegari, E., Hunziker, J.C., Pfeifer, H.R., 1997. Volcanic-rich tur-

bidites of the Taveyanne sandstones from the Thônes syncline (Savoie, France):records for a Tertiary postcollisional volcanism. Schweiz. Min. Petrogr. Mitt. 77,161–174.

anchez, G., Rolland, Y., Jolivet, M., Brichau, S., Corsini, M., Carter, A., 2011a. Exhuma-tion controlled by transcurrent tectonics: the Argentera-Mercantour massif (SWAlps). Terra Nova 23, 116–126, doi:10.1111/j. 1365-3121.2011.00991.x.

anchez, G., Rolland, Y., Schneider, J., Corsini, M., Oliot, E., Goncalves, P., Verati,C., Lardeaux, J.M., Marquer, D., 2011b. Dating low temperature deformation by40Ar/39Ar on white micas, insights from the Argentera-Mercantour massif (SWAlps). Lithos, doi:10.1016/j.lithos.2011.03.009.

chlunegger, F., Willett, S., 1999. Spatial and temporal variations in exhumation ofthe Central Swiss Alps and implications for denudation mechanisms. In: Geol.Soc. Lond. Spec. Publ. No. 154, Exhumation Processes, pp. 157–179.

chmid, S.M., Aebli, H.R., Heller, F., Zingg, A., 1989. The role of the Periadriatic Line inthe tectonic evolution of the Alps. In: Coward, M.P., Dietrich, D., Park, R.G. (Eds.),Alpine Tectonics, Geol. Soc. Spec. Publication No. 45. , pp. 153–171.

chmid, S., Berger, A., Davidson, C., Giere, R., Hermann, J., Nievergelt, P.,Puschnig, A.R., Rosenberg, C., 1996. The Bergell pluton (Southern Switzerland,Northern Italy): overview accompanying a geological-tectonic map of theintrusion and surrounding country rocks. Schweiz. Min. Petrogr. Mitt. 76,329–355.

chmid, S., Fügenschuh, B., Kissling, E., Schuster, R., 2004. Tectonic map and overallarchitecture of the Alpine orogen. Eclogae Geol. Helv. 97, 93–117.

chmid, S.M., Kissling, E., 2000. The arc of the western Alps in the light of geophysicaldata on deep crustal structure. Tectonics 19, 62–85.

chmid, S.M., Zingg, A., Handy, M., 1987. The kinematics of movements along theInsubric Line and the emplacement of the Ivrea Zone. Tectonophysics 135,47–66.

chreiber, D., Lardeaux, J.M., Martelet, G., Courrioux, G., Guillen, A., 2010. 3-D modelling of Alpine Mohos in Southwestern Alps. Geophys. J. Int. 180,961–975.

chwartz, S., Guillot, S., Tricart, P., Bernet, M., Jourdan, S., Dumont, T., Montagnac, G.Source tracing of detrital serpentinite in the Oligocene molasse deposits fromWestern Alps (Barrême basin): implications for relief formation in the InternalZone. Geol. Mag., submitted for publication.

chwartz, S., Lardeaux, J.M., Tricart, P., Guillot, S., Labrin, E., 2007. Diachronousexhumation of HP-LT metamorphic rocks from south-western Alps: evidencefrom fission-tracks analysis. Terra Nova 19, 133–140.

chwartz, S., Tricart, P., Lardeaux, J.M., Guillot, S., Vidal, O., 2009. Late tectonic andmetamorphic evolution of the Piedmont accretionary wedge (Queyras Schisteslustres, western Alps): evidences for tilting during Alpine collision. Geol. Soc.Am. Bull. 121, 502–518.

eno, S., Dallagiovanna, G., Vanossi, M., 2005. A kinematic evolutionary model for
the Penninic sector of the Ligurian Alps. Int. J. Earth Sci. 94, 114–129.
iegesmund, S., Layer, P., Dunkl, I., Vollbrecht, A., Steenken, A., Wemmer, K., Ahrendt,H., 2008. Exhumation and deformation history of the lower crustal section of theValstrona di Omegna in tne Ivrea Zone, southern Alps. Geol. Soc. Lond. Spec. Publ.298, 45–68.

namics 56– 57 (2012) 18– 38

Simon-Labric, T., Rolland, Y., Dumont, T., Heymes, T., Authemayou, C., Corsini, M.,Fornari, M., 2009. 40Ar/39Ar dating of Penninic Front tectonic displacement (WAlps) during the Lower Oligocene (31–34 Ma). Terra Nova 21, 127–136.

Sinclair, H.D., 1997. Tectonostratigraphic model for underfilled peripheral forelandbasins: an Alpine perspective. G.S.A. Bull. 109, 324–346.

Smith, R., Joseph, P., 2004. Onlap stratal architectures in the Gres d’Annot: geometricmodels and controlling factors. Geol. Soc. Lond. Spec. Publ. 221, 389–399.

Stampfli, G., Borel, G., Marchant, R., Mosar, J., 2002. Western Alps geological con-straints on western Tethyan reconstructions. In: Rosenbaum, G., Lister, G.S.(Eds.), Reconstruction of the Evolution of the Alpine-Himalayan Orogen. J. VirtualExplorer, vol. 7, pp. 75–104.

Stampfli, G., Mosar, J., Marquer, D., Marchant, R., 1998. Subduction and obductionprocesses in the Swiss Alps. Tectonophysics 296, 159–204.

Stanley, D.J., 1980. The Saint-Antonin conglomerate in the Maritime Alps: A modelfor coarse sedimentation on a submarine slope. Smithsonian Contrib. Mar. Sci.5, 1–28.

Steck, A., 1990. Une carte des zones de cisaillement ductile des Alpes centrales.Eclogae Geol. Helv. 83, 603–627.

Steck, A., 1998. The Maggia cross-fold: An enigmatic structure of the Lower Penninicnappes of the Lepontine Alps. Eclogae Geol. Helv. 91, 333–343.

Sue, C., Tricart, P., 2003. Neogene to ongoing normal faulting in the innerwestern Alps: a major evolution of the late Alpine tectonics. Tectonics 22,doi:10.1029/2002TC001426.

Sztrakos, K., du Fornel, E., 2003. Stratigraphie, paléoécologie et foraminifères dupaléogène des Alpes Maritimes et des Alpes de Haute-Provence (Sud-Est de laFrance). Rev. Micropal. Genève 46, 229–267.

Tapponnier, P., 1977. Evolution tectonique du système alpin en Méditerrannée:poinc onnement et écrasement rigide-plastique. Bull. Soc. Géol. France 19,437–460.

Tempier, C., 1987. Modèle nouveau de mise en place des structures provenc ales.Bull. Soc. Géol. France 8, 1–8.

Thomas, J.C., Claudel, M.E., Collombet, M., Tricart, P., Chauvin, A., Dumont, T., 1999.First paleomagnetic data from the sedimentary cover of the French PenninicAlps: evidence for Tertiary counterclockwise rotations in the Western Alps. EarthPlan. Sci. Lett. 171, 561–574.

Tilton, G.R., Schreyer, W., Schertl, H.P., 1991. Pb–Rb–Nd isotopic behaviour of deeplysubducted crustal rocks from the Dora Maira Massif, Western Alps, Italy: what isthe age of the ultrahigh-pressure metamorphism? Contrib. Mineral. Petrol. 108,22–33.

Tricart, P., 1980. Tectoniques superposées dans les Alpes occidentales, au sud duPelvoux. Evolution structurale d’une chaîne de collision. Thèse de Doctoratd’Etat. Strasbourg, 407.

Tricart, P., Schwartz, S., 2006. A north-south section across the Queyras Schisteslustrés (Piedmont zone, western Alps): Syn-collision refolding of a subductionwedge. Eclogae Geol. Helv. 99, 429–442.

Tricart, P., Schwartz, S., Sue, C., Poupeau, G., Lardeaux, J.M., 2000. La dénudationtectonique de la zone ultradauphinoise et l’inversion du front brianc onnais ausud-est du Pelvoux (Alpes occidentales): une dynamique miocène à actuelle. Bull.Soc. Géol. France 172, 49–58.

Varrone, D., d’Atri, A., 2007. Acervulinid macroid and rhodolith facies in the EoceneNummulitic Limestone of the Dauphinois Domain (Maritime Alps, Liguria, Italy).Swiss J. Geosci. 100, 503–515.

Vernant, P., Masson, F., Bayer, R., Paul, A., 2002. Sequential inversion of local earth-quake traveltimes and gravity anomaly – the example of the western Alps.Geophys. J. Int. 150, 79–90.

Vernet, J., 1966. Observations nouvelles sur le synclinal d’Ailefroide et les borduresdu massif du Pelvoux en Vallouise. Trav. Lab. Géol. Grenoble 42, 275–280.

Vialon, P., Rochette, P., Ménard, G., 1989. Indentation and rotation in the westernAlpine arc. In: Coward, M.P., Dietrich, D., Park, R.G. (Eds.), Alpine Tectonics, Geol.Soc. Lond. Spec. Publ. 45. , pp. 329–338.

Vignaroli, G., Faccenna, C., Jolivet, L., Piromallo, C., Rossetti, F., 2008. Subductionpolarity reversal at the junction between the Western Alps and the NorthernApennines, Italy. Tectonophysics 450, 34–50.

Vignaroli, G., Faccenna, C., Rossetti, F., Jolivet, L., 2009. Insights from the Apenninesmetamorphic complexes and their bearing on the kinematics evolution of theorogen. Geol. Soc. Lond. Spec. Publ. 311, 235–256.

Von Blankenburg, F., Davies, J.H., 1995. Slab breakoff: a model for syncollisionalmagmatism and tectonics in the Alps. Tectonics 14, 120–131.

Vuagnat, M., 1985. Les grès de Taveyanne et roches similaires: vestiges d’une activitémagmatique tardi-alpine. Mem. Soc. Géol. Ital. 26, 39–53.

Waibel, A.F., 1990. Sedimentology, petrographic variability and very-low-grademetamorphism of the Champsaur sandstone (Paleogene, Hautes Alpes, France).PhD thesis. Geneva, 140.

Waldhauser, F., Lippitsch, R., Kissling, E., Ansorge, J., 2002. High-resolution tomog-raphy of upper-mantle structure using an a priori three-dimensional crustalmodel. Geophys. J. Int. 150, 403–414.

Ziegler, P.A., 1989. Geodynamic model for Alpine intra-plate compressional defor-
mation in Western and Central Europe. Geol. Soc. Lond. Spec. Publ. 44, 63–85.
Zimmermann, R., Hammerschmidt, K., Franz, G., 1994. Eocene high pressure meta-morphism in the Pennine units of the Tauern window (Eastern Alps): evidencefrom 40Ar–39Ar dating and petrological investigations. Contrib. Miner. Petrol.117, 175–186.