B16_R_ copertina C August 20-28,2004 Florence -Italy

Field Trip Guide Book - B16 Pre-Congress J. Muñoz,A.Teixell R. Bourrouilh,L.Moen-Maurel, Leaders: FROM RIFTINGTOINVERSION BOUNDARY RECONSTRUCTION SEDIMENTATION ANDPLATE THRUST-BELT: GEODYNAMICS, WESTERN PYRENEESFOLD-AND- 32 Volume n°2-fromB16toB33 GEOLOGICAL CONGRESS nd INTERNATIONAL B16 28-05-2004, 17:16:22 The scientific content of this guide is under the total responsibility of the Authors

Published by: APAT – Italian Agency for the Environmental Protection and Technical Services - Via Vitaliano Brancati, 48 - 00144 Roma - Italy

Series Editors: Luca Guerrieri, Irene Rischia and Leonello Serva (APAT, Roma)

English Desk-copy Editors: Paul Mazza (Università di Firenze), Jessica Ann Thonn (Università di Firenze), Nathalie Marléne Adams (Università di Firenze), Miriam Friedman (Università di Firenze), Kate Eadie (Freelance indipendent professional)

Field Trip Committee: Leonello Serva (APAT, Roma), Alessandro Michetti (Università dell’Insubria, Como), Giulio Pavia (Università di Torino), Raffaele Pignone (Servizio Geologico Regione Emilia-Romagna, Bologna) and Riccardo Polino (CNR, Torino)

Acknowledgments: The 32nd IGC Organizing Committee is grateful to Roberto Pompili and Elisa Brustia (APAT, Roma) for their collaboration in editing.

Graphic project: Full snc - Firenze

Layout and press: Lito Terrazzi srl - Firenze

B16_R_ copertina D 27-05-2004, 8:29:37 Volume n° 2 - from B16 to B33

32nd INTERNATIONAL GEOLOGICAL CONGRESS

WESTERN FOLD-AND- THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION

AUTHORS: R. Bourrouilh1, L. Moen-Maurel2, J. Muñoz3, A. Teixell4 1 Laboratoire CIBAMAR, Université Bordeaux 1, Talence Cedex - 2 TOTAL, Pau Cedex - France 3 Departament de Geodinamica i Geofisica, Facultat de Geologia, Universitat de Barcelona - Spain 4 Departament de Geologia, Universitat Autònoma de Barcelona, Bellaterra - Spain

Florence - Italy August 20-28, 2004

Pre-Congress B16

B16_R A 27-05-2004, 8:39:53 Front Cover: 1. Thrusts and Folds structures of Les Eaux Chaudes in the , France. DAY 2, Stop 2.5b. 2. Thrusts and Folds structures of the External Sierras, Spain. DAY 5, Stop 5.3. 3. Thrusts and Folds of Gavarnie at La Estiba, Spain. DAY 6, Stop 6.2.

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Leaders: R. Bourrouilh, L. Moen-Maurel, J. Muñoz, A. Teixell

Introduction General geological This fi eld trip along a geotraverse through the north- setting (Plate 1, fi g.1 and 2). western and south-western Pyrenees area has three main purposes: Introduction 1. To analyse the present-day structures in the fold Situated between the European plate and the Iberian and thrust belt and to reconstruct their structural plate, the Pyrenean orogenic belt extends from the evolution in order to better understand the subsurface NW part of Spain or Galicia, to the Southern part of foreland structures (some of them being oil/gas traps the Alps and the Gulf of Genoa, in the Mediterranean. or prospects). It is thus a belt almost 2,000 km long, of which only 2. To describe the stratigraphic evolution of the the central part, or the Pyrenees, is a visible collisional Mesozoic and Tertiary formations (with respect to orogen, whereas both the Western part or the Bay of plate tectonics and to the Iberian plate drift) on several Biscay and the Eastern part or the Gulf of Lion and transects: along the Ossau Valley, the Aspe Valley, the Gulf of Genoa remain at subsea. Mendibelza and Orhy Massifs for the northern side, The Pyrenees resulted from an orogeny which and from the Orhy Massif to Jaca and Aïnsa for the developed over a previously thinned continental crust, southern side. but without an intervening oceanic crust between the 3. To give petroleum geoscientists the recent concepts two diverging plates. Underplating of the Iberian plate and keys for the Pyrenean foreland and foothills underneath the European plate led to the sinking of a hydrocarbon exploration. deep crustal root along a north-dipping plane while coeval delamination of the upper crust led to the The scenic landscapes of the Pyrenees mountain range propagation of a major fold-and-thrust belt to the provide an exceptional laboratory for examining the south as well as of a conjugate north-verging back- orogenic processes, from rifting to collision, both thrust system. Thus the range is characterized by a in the crustal lithosphere as well as in the foreland doubly-verging asymmetric thrust stack wedge: basins. - the southern fold-and-thrust belt (FTB) represents A comparison to more classical fold-and-thrust belts a south-verging imbricate fan affecting cover will be proposed along the way and in the wrap-up formations (Mesozoic and Cenozoic in age) conclusion of the fi eld trip. rooting into an antiformal stack of basement rocks (Precambrian to Paleozoic variscan folded series) in Field References: the axial zone. The piggy-back thrust sheets indicate a Topographic and Road maps : for example: crustal shortening which reaches over 100 km along, Michelin n°234 Aquitaine 1/ 200,000 i.e. 90% of the total orogen collision; Michelin n°573, Regional 1/400,000: - the northern fold-and-thrust belt is confi ned over Pais Vasco/Euskadi, Navarra, La Rioja. a narrower zone north of the axial zone or the High Michelin n°574, Regional:1/400,000: Chain, in a conjugate position to the underplating Aragon, Cataluña/Catalunya process (Moen-Maurel et al., 1999). Geological maps : The relatively minor inversion in the Northern FTB S.N.P.A. (Société Nationale des Pétroles d’ Aquitaine) protected the rifting series and structures from uplift (1972). Carte géologique des Pyrénées, scale and erosion, thus permitting the examination of the 1:250,000, P. Soler ed. 4 plates. initial processes of the orogenesis.

B.R.G.M. (1980). Carte Tectonique de la France, The genesis of the Pyrenean belt is the result of: B16 to B33 n° 2 - from Volume scale 1:1,000,000, B.R.G.M. Ed. - 1. the break-up of the 250 Ma old Wegener’s Pangea B.R.G.M.: 1/50,000 geological Maps: n° XIII-46, St and reactivation of its structural inherited fabrics, Jean Pied de Port; XIV-46, Tardets-Sorholus; XIV-47, - 2. the correlative propagation of the Atlantic Mid- ; XV-45, Pau; XV-46, Oloron Sainte Marie; Oceanic Ridge from Central Atlantic to the North, XV-47, (under press). with an Atlantic RRR triple junction along its Instituto Geologico y Minero de Espana, Geological Eastward opening branch entering Bay of Biscay, Maps at 1/ 250,000 and at 1/50,000: n°118 Zuriza, - 3. the Late Jurassic - Late Cretaceous diachronous n° 144 Anso, n°145 Sallent. Eastward opening of the Bay of Biscay which

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Volume n° 2 - from B16 to B33 B16 - B16 rift never producedoceaniccrust:itcanthusbecalled junction pointaborted(R-->r),theNorth-Pyrenean Bay ofBiscay. In Turonian theEastward Atlantic R basins, suchastheN-Pyreneanbasinattipof Iberian plateandinthebirthofriftedinterplate resulted inthedriftandprogressive rotationofthe Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell the Pyrenees,fromEbroBasin(South)to Aquitaine Basin(North). Plate 1-1.StructuralMapofthePyreneeswithlocationcrosssection AB. 2.Transversal crosssection AB of Figure 1-Crustalscalebalancedcrosssection,ECORS seismicprofi as wellbytheclosureof Tethys, whichprovoked opening ofboththeSouth Atlantic andIndianOceans, south-east. This driftisduetotheCretaceousoceanic Stopping thefreedriftofIberianplatetoward the - 4.thenorthward pushbythelarge African plate “aulacogen”, le, fromChoukrouneetal.,1989. 27-05-2004, 8:44:25 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Figure 2 - Cross-section passing through the and gas fi elds (Moen-Maurel et al.1999).

the migration of the African plate towards the NE and compensation responded to the collision and the then towards the N. This plate motion crushed the associated crustal thickening, creating a large open space between Europe and Africa and formed intraplate foreland over the Iberian plate, (the South- the Pyrenean-Alpine orogenic belt in a diachronous Pyrenean basin), and a retro-foreland basin on the compression which proceeded westwards along the Northern edge of the Iberian plate and over the northern margin of the Iberian plate. As a result of the collision between the Iberian and European plates, which began during the Turonian and continued: - 1. the rifted N-Pyrenean basin became a foredeep basin Volume n° 2 - from B16 to B33 n° 2 - from Volume - 2. a lithospheric

Plate 2 - 1. Transect Of The West-central Southern Pyrenees, from A. Teixell. 2. Cross-section of the Western Jaca basin and Ainsa basin across the Boltaña anticline, from J. Muñoz.

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European plate (the Aquitaine basin). verging subduction. To the east, the Pyrenean orogenic - 3. the Pyrenean orogenic belt displays a fan-shaped belt extends in the Alps of Provence, exhibiting minor cross-section, resulting from the crustal ductile inversion thrusts and folds (Debelmas, 1974). More underthrusting or underplating of the Pre-Pangean to the south, the Neogene Mediterranean extension, basement (Precambrian-Paleozoic) of the Iberian consecutive to the Betico-Rifean compressional plate underneath the European plate. Since the initial events (Bourrouilh and Gorsline, 1979) overprints the stages of the Pyrenean collision at Late Santonian- Pyrenean belt. Campanian times two foreland basins developed, one Between these belt-tip areas, where the European and on each side of the double-wedge (Figs. 1 and 2). Iberian plates are in full contact, i.e. in the Pyrenees - 4. The post-Pangean sedimentary infi ll of the sensu stricto, the collision directly affected the interplate (north) and the intraplate (south) basins continental lithosphere, since no oceanic fl oor was thrusted toward either the north (Aquitaine basin) and present. Using an inherited Precambrian ( ?) - Variscan south (Ebro basin) forelands, in successive shallow fault network, the collision provoked an inversion of fold-and-thrust piggy-back sheets. the deep fault network in the crustal basement, and the building of a deep-rooted fan-shaped mountain range Deformation of the Pyrenean double-wedge (Fig.1 and 2, and Plate 1). In the Central Pyrenees the migrated outwards in a piggy-back manner, although associated strike-slip motion that is well visible along synchronous hindward internal deformation has also one of the faults of the southern rift margin (North- been documented. The forward propagation of the Pyrenean Fault) marks the plate boundary. Along deformation in the southern Pyrenees was modifi ed, our geotraverse the NPF is concealed underneath a in the last stage of the evolution of the thrust-belt, by a south-verging thrust (Plate 1). The North-Pyrenean break-back reactivation of the older thrusts and by the rift structures were little inverted north of the rift development of new, minor out-of sequence thrusts axis, and remained north of the North-Pyrenean affecting syntectonic deposits (Martínez et al., 1988, Thrust Front. South of its axis the tilted blocks of the Vergés and Muñoz, 1990). Thrust transport direction rifting stage were affected by inversion and uplifted, was constantly N-S to NNE-SSW through most of either towards the south or the north, depending on the tectonic evolution as deduced by the map pattern the original dip sense of the rift faults, either sheared of the structures, kinematic criteria along thrust by wrenching, or thrust along the detachments in the planes and the absence of signifi cant rotation around Triassic evaporites and the Upper Cretaceous fl ysch. a vertical axis along the analyzed cross-section The south-verging thrusting along successive (Dinares et al., 1992). This implies a near normal shallow basal and internal plastic décollements also convergence through the main orogenic phase. The affected the cover of the High Chain, as well as the strike slip convergence vector between the two plates must be found at depth, decoupled from the cover sedimentary infi ll of the South-Pyrenean intraplate deformation. A partitioning of the deformation must basin. The plate collision resulted in the piggy-back occur both in map view and with depth in favour of stacking of south-verging folds and thrusts involving the activation of detachment horizons. the basement as well as its cover. Although an isostatic balance occured all along the Pyrenean orogeny, between compression - erosion The crustal and cover structuration is clearly -sedimentation, the main apparent mountain uplift observable in the fi eld, in the Pyrenean mountain belt has occurred since the Pleistocene, following mainly and foothills. It can be subdivided from north to south the glaciations. It mostly affects the Iberian plate, as a into different structural units (fi g. 2 and Plate 1, fi g.1 result of the isostatic rebound of the crustal Pyrenean and 2) (Castéras, 1974): subducted root. The northern foreland basin, in the southern part Volume n° 2 - from B16 to B33 n° 2 - from Volume of the Aquitaine basin, consists of a thick (few km) Structure of the Pyrenees succession of Upper Cretaceous turbidites overlain The Pyrenees can be considered an immature, by an up to 4 km thick Paleogene series. Most of the incomplete orogen resulting from plate drift rotations latter are represented by continental deposits as only which leads to varying deformations along strike. To marine platform sediments of Lower Ypresian age the west, the space between the European and Iberian are observed (Buy and Rey, 1975). The Aquitaine plates still remains open in the Bay of Biscay, the basin mainly developed in the footwall of the North- northern margin of Spain showing an incipient north- Pyrenean Frontal Thrust and was not greatly involved

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in the North-Pyrenean thrust system. The Axial Zone or High Chain (Plate 1, fi g. 2 and The southern part of the Aquitaine Basin is affected Plate 2, fi g. 1) is the highest part of the range, by folds with large curvature radii related to the and represents the present-day orographic axis. Pyrenean Tertiary tectonic phase. In this area the It is composed of Precambrian series, possibly Pyrenean compression is mainly Eocene in age. This folded (?) during the Late Proterozoïc, and of thick phase enhanced salt tectonics. Paleozoic series that were folded during the Variscan The Sub-Pyrenean Zone or northern folded foreland (Hercynian) orogeny and redeformed during the (which lies beneath and north of the North Pyrenean Upper Cretaceous to Tertiary Pyrenean tectonic Thrust Front (or NPTF) is characterized by north- phases. The High Chain basement is overlain by verging blind thrusts and asymmetric folds often discontinuous Permo-Triassic deposits and by a thick cored by a salt ridge or an inverted rift graben. Upper Cretaceous shelf carbonate series; this shelf The NPTF is composed of a series of en-echelon N- is overlain by the edge of an Upper Cretaceous to verging thrust faults running from the Bay of Biscay Tertiary synorogenic fl ysch basin, which developed up to the South-Western Alps. synchronously with the compression and with the The North Pyrenean Zone or NPZ, lies to the south of tectonic subsidence and deepening of the South and the NPTF and is characterized by north-verging thrusts North Pyrenean foredeep basins. and folds verging either north or south depending The basement rocks of the Axial Zone constitute an on the dip sense of the inverted normal faults. The antiformal stack. This antiformal stack only involves southern part of this zone has been deformed by upper crustal rocks, its fl oor thrust being located 15 schistose deformation and low-grade Pyrenean-age km below the top of the basement. In the Central metamorphism, at the contact with the NPF. Pyrenees it is constituted by three main structural Precambrian to Paleozoic basement outcrops in the units: Nogueres, Orri and Rialp thrust sheets NPZ, constituting the N-Pyrenean massifs. (Muñoz, 1992). The regional westward plunge of the The North Pyrenean Fault or NPF lies to the south of basement antiformal stack leaves only the Nogueres these units, and appears in various ways throughout – equivalent thrust sheet at outcrop level; it is then the belt. Its variable aspects take on the status of the called Gavarnie - Eaux Chaudes in the Western orogenic axis of the range (Iberian-European plate Pyrenees. The Nogueres-Gavarnie thrust sheet is the boundary), the change-over zone from northern uppermost of the antiformal stack and its southern tip to southern vergence (Central Pyrenees), the zone is the basement of the lower cover thrust sheets. In the of intense deformation (various schistosities), a central Pyrenees, the contact between the cover Upper metamorphic zone, and a lherzolite (mantle-derived Thrust sheets and the basement antiformal stack ultrabasic granulitic rock) injection zone (fi g. 2 and corresponds to a passive-roof backthrust (Morreres Plate 1, fi g. 2). backthrust). During the development and southward The fault evolved from an initial Albo-Cenomanian displacement of the basement antiformal stack the transtensional regime with the formation of pull- cover units have been wedged by delamination, and apart basins and the development of a thermal on the top of the basement, as described in other metamorphism (Debroas, 1990; Goldberg and orogenic belts (Price, 1986). A mirror image of this Maluski, 1988) to a later transpressional regime delamination of the cover by the basement thrust during the onset of convergence in Early Senonian sheets also exist in the North-Pyrenean foreland at the time (Puigdefàbregas and Souquet, 1986; Debroas, edge of the Paleozoic Basque Massifs, which make 1990). Lower crustal granulitic rocks as well as a cartographic salient and a splinter wedge into the ultrabasic upper mantle rocks (lherzolites) are northern foreland (Figure 1). observed embedded between the Lower Mesozoic The South Pyrenean Zone (Plate 2, fi g. 2) is metamorphic rocks along a narrow strip parallel to the characterized by South-verging thrusts and folds. B16 to B33 n° 2 - from Volume North Pyrenean Fault (Choukroune, 1976; Vielzeuf The stratigraphy is essentially represented by Permo- and Kornprobst, 1984). These rocks were carried to Triassic deposits, locally overlain by Jurassic, but upper crustal levels during the strike-slip faulting. mostly covered by Upper Cretaceous shelf carbonates Apart from this narrow strip parallel to the North passing to Eocene turbidites (in the western part) and Pyrenean fault neither post-Hercynian metamorphic Oligocene molasses conglomerates rocks nor lower crustal rocks are observed at the In the southern Pyrenees the cover Upper Thrust surface in the Pyrenees. Sheets (Muñoz et al., 1986) consist of Mesozoic and

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell late development stages(Coney, buried thesouth-Pyreneanthrustsystemduringits the enclosedbasinandprogressively backfi Eocene-Lower Miocenecontinentalclasticsfi paleogeographical closingoftheEbrobasin.Upper Priabonian evaporites. These evaporites representthe sediments oftheforelandbasinafterLower Thrust. Itismainlyfi foreland southoftheSouthernPyreneesFrontal The EbroBasinrepresentstheautochthonousexternal foreland basin. and thesedimentaryinfi duplexes systemwhichaffects boththeHighChain and representstheFrontalthrustoframps from theeasttonorth-west(Plate1,Fig.2) The South-Pyrenean Thrust FrontorSPFTextends Sheets. tectonics isastructuralfeatureoftheUpper Thrust faults, mainlyLower Cretaceousinage.Inversion thrusts isstronglycontrolledbyprevious extensional N-S transportdirectioncanbededuced.Locationof confi probably relatedtotheoriginalMesozoicbasin Sheets show numerousobliqueandlateralstructures, Cretaceous) extensional faults. The Upper Thrust geometry imposedbyCretaceous(mainlyLower the Cretaceousstratigraphicunitscoupledwith progressive southwards thinningandpinchoutof 7km. This sedimentarywedgeistheresultof units andprogressively thickens northwards upto series isonlytensofmetersthickinthesouthernmost the easternPyrenees(Figs.1and2). The Mesozoic central PyreneesandthePedraforcathrustsheetsin Boixols, MontsecandSierrasMarginales) inthe Central-South Pyreneanthrustsheets(Cotiella, with theEbroforelandbasin(Fig.2). They arethe top ofautochthonousPaleogene rocksincontinuation evaporites. These thrustsheetswerelaterthrustedon detached fromthebasementover theUpper Triassic syntectonic Paleogene rockswhichwereinitially techniques (deeprefl has beeninvestigated bydifferent geophysical The crustalandlithosphericstructureofthePyrenees crustal structure Geophysical dataand ECORS-Pyrenees profi from thedeepseismicrefl best constrainthePyreneancrustalstructureare anomalies, tomography, heatfl profi les, gravity, magnetotellurics,magnetic guration. Fromthesestructuresanapproximately lled bythelaststagecontinental ection and refractionseismic les (Choukrouneetel.,1989, ll oftheSouth-Pyrenean ection profi ection ow). The datathat et al les, mainly the ., 1996). lled and lled lled Pyrenees (Pous and byamagnetotelluricprofi tomographic analyses(SouriauandGranet,1995) is compatiblewithothergeophysical datasuchas into themantle. This inferredcrustalsubduction was subductedtogetherwiththelithosphericmantle lower crust,below theuppercrustaldouble-wedge, (Fig. 4). Apparently, thecrustwas decoupledandthe the bestgeometryinwhichtointegrate allthesedata wedge involves only uppercrustalrocksprovides that anexplanation inwhichtheorogenicdouble- al combined geologicalandgeophysicaldata(Roure of thePyreneeshave beengiven onthebasisof Several different interpretationsofthecrustalstructure et al construction ofcrustalbalancedcross-sections(Roure the Europeanoneandhasbeenbasisfor to show thesubductionofIberianplatebelow Roure 1989). These profi on theorderof80kmarereachedwestwards from shortening decreaseswestwards. Shorteningvalues as cross-sectionswestoftheECORSone,show that Srivastava, 1991). These paleomagneticdata,aswell motion ofIberiaafterpaleomagneticdata(Roestand plates asdeducedbyreconstructionofthepast the estimatedseparationofIberianandEuropean These shorteningcalculationsarecompatiblewith of theNorthPyreneanFault. the south-verging thrustsandantiformalstacks,south about 90%ofthecollisionshorteningisproducedby Pyrenean Fault (Moen-Maurel by thenorth-verging structuresnorthoftheNorth more than15kmofshorteningcanbeaccounted estimate ofabout125km(Vergés section intheeasternPyreneesyieldedashortening 1989). A shorteningcalculationforacrustalcross- over 100km(Deramond central Pyreneeshave estimatedshorteningvalues is restored.Othercross-sectionrestorationsofthe below thesolethrustofPyreneansystem up to160kmiftheinternaldeformationofcrust 147 km(Muñoz,1992).However, thisvalue increases along theECORSprofi of acrustalcross-sectionthecentralPyrenees orogenic contraction(Fig.1). A geometricalsolution geological databut alsotoestimatetheamountof constructed notonlytointegrate geophysicaland Balanced andrestoredcross-sectionswere Balanced andrestored cross-sections ., 1989,Mattauer, 1990,Muñoz,1992). We believe ., 1989,Muñoz,1992). et al .,1995). le gave atotalshorteningof les have beeninterpreted et al et al ., 1985;Roure le acrossthecentral ., 1995). Therefore et al ., 1995).No 27-05-2004, 8:40:35 et al et ., WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

the ECORS cross-section (Grandjean, 1992, Teixell, Stratigraphic and 1996, 1998). geodynamic evolution The estimated duration of convergence in the central (Fig. 3) (See further on the contribution of A. Teixell Pyrenees is about 60 Ma, which gives a mean and of J. Muñoz for a more detailed study of the shortening rate of 2.5 mm/yr. A similar shortening Southern Pyrenean side). rate has also been deduced in the eastern Pyrenees According to Bourrouilh, Richert and Zolnaï, 1995, during a shorter period of convergence (Vergés et al., Richert et al., 1995, the stratigraphic and structural 1995). The latest deformation migrated westwards. It evolution of the Pyrenees can be summarized as Stopped during Middle Oligocene time in the eastern follows: Pyrenees and continued to the Middle Miocene in Precambrian to Paleozoic the westernmost Pyrenees (Vergés, 1993). In the The evolution of the Precambrian and Paleozoic central Pyrenees, along the ECORS cross-section, domain related to the geodynamics of the Pyrenees, deformation ended by Early Miocene times. Montagne Noire and Western Mediterranean has Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 3 - Geodynamic evolution of Bay of Biscay-Pyrenees and North-Pyrenean basins, from Bourrouilh et al., 1995, modifi ed.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell from basetotop:postorogenicredconglomerates Germano-type i.e.athree-foldstratigraphy: The Triassic seriesareofatypical Triassic toEarlyLiassic(Fig.3) fl debris (Lucas1985)but alsobasaltic an andesiticvolcanism provides volcanic of continentalredbeds,inwhichlocally previously deformedseries.Itiscomposed The series. Variscan graniteslocallyintrudedthe and foldsmetamorphism.Upper orogeny was accompaniedbylarge thrusts (or Hercynian) orogenies. The Variscan affected byCaledonianand Variscan and Paleozoic basementwerethensuccessively section andtheredPermianmember. Precambrian a limyDevonian, asandy-shalycarboniferous (Gapillou, 1981),ablack-shalySilurianinterval, 1985), athickfi then locallystromatolithicCambrian(Bouquet main members:apost-orogenicconglomeraticand (Ursuya-Baigoura massif). The Paleozoic containssix (Agly massif)andradiochronologicallydated Generally, Precambrianseries aremetamorphosed was acquiredduringtheLateProterozoïc(Cadomian). The structuralframework ofthePrecambrianbasement Bourrouilh andMirouse,(1984)others. by Winnock (1971), Autran andCogné(1980), Paleozoic hasbeenstudiedinthe Aquitaine area been synthetizedbyBourrouilhandal.(1980). The Lacq-Meilllon area(Total). Figure 4-Tectono-stratigraphic evolution ofthe ows, aswitnessesofoceanicexpansion. Permian liesunconformablyonthe ne-grained silici-clasticOrdovician et al ., is againseparatedintotwo domains,alongthe In theLatePortlandiantoBerriasian,platform in average) areassociatedtothisregressive cycle. dolomitic facies oftheManoDolomite(200 m thick tectonic phaseleadstoageneralregression. The At theendofJurassic,Neo-Kimmerian synsedimentary salttectonicsalongbasementfaults. local condensedsedimentarydeposits,relatedto environment ofdeposition,affected onlyby to LateKimmeridgianperiodrepresentsastable Following thisphaseofdifferentiation, theMiddle limestones ofthelower CagnotteFormation. Ammonite marlsandLower Kimmeridgianshaly open marineenvironment tothewest : Oxfordian and BayseresFormations totheeastversus a more part withdolomitesandlimestonesoftheMeillon is subdivided intotwo majorprovinces: aninner platform (Canérot,1987). The localPangean platform paleogeographical differentiation onthe phase leadingtostructuraland associated toamoreactive extensional Early Kimmeridgiantimeperiodcanbe (Dogger-Malm). The Oxfordianthrough then mainlylimestoneplatformsequence upwards intoashallow-marine dolomitic, The Lower Liassicanhydritesgrade Jurassic present-day basincenter. taper off tozerotowards the Aquitaine several hundredsofmetres),whilethey southernmost riftedbasinedge(over distension, hasbeenemplacedalongthe thickest volcanic wedgeshowing crustal shales withevaporites andvolcanics. The and sandstones,marinecarbonatesred Figure 5-Cross-sectionoftheLacq-Meillon area (Total). 27-05-2004, 8:40:39 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

submeridian trend defi ned here above. At the Jurassic- The paleogeography changes completely, and Cretaceous boundary large areas became emergent as is entirely controlled by the important tectonic demonstrated by the presence of anhydrite, some movements taking place along the plate boundaries coal, red shale, clastics (sand), sand-rich carbonates (Peybernès and Souquet, 1984). As a result, the and intra-formational (desiccation) breccias. The fi rst subsiding zones shift to the south towards this very salt-movements (gentle swells and salt-cushions) mobile zone, while a massive transgression develops seem to have started as early as in the Portlandian over the entire area. The Late Albian sedimentation (Winnock and Pontalier 1970). Massive sand-bodies overlaps the earlier paleogeographies, demonstrating were deposited in the Parentis Basin during the the change of structural stress at this time. Locally salt Purbeckian-Wealdian period. The equivalent series tectonics enhanced erosion and subsidence, producing of the southern Aquitaine sub-basins are carbonates, the main hydrocarbon traps as they are known today. intraformational breccias and shales (Lacq). The Late Cretaceous sedimentation over the south-western part of the An important inversion occurred diachronously all basin indicates a deeper environment of deposition along the Europe-Iberia plate boundary. While the and a more continuous sedimentation during the Late western part remains extensive in a rift mode, the Jurassic – Early Cretaceous transition (Hauterivian eastern part of the domain progressively became in – Berriasian). Montagné’s thesis (1986) evidenced compression and in a foredeep mode. Correlatively, rifting during Late Jurassic, south of . Later, two extensive carbonate platforms developed, ODP Leg 103 (1988) found turbidites in the off-shore covering to the north the major part of the Aquitaine Hauterivian sequences in the westernmost part of the Basin, and to the south the persistently high Iberian basin near Bilbao, indicating yet another opening plate, both carbonate and separated by the N-Pyrenean (rifting) attempt of the Bay of Biscay. fl ysch-furrow in between. Thus, the Late Cretaceous paleogeography shows three major domains from Early Cretaceous North to South: From Late Jurassic onward, a new paleogeography On the Aquitaine platform, to the north, the developed, provoking the formation of en-echelon syntectonic sedimentation of the foredeep evolves diamond-shaped grabens in relation with the laterally to a carbonate shelf (Dubois and Seguin, activation of inherited structural fabrics. 1980) of Cenomanian to Maastrichtian ages. Within these basins three major phases of This domain is located in a more distal and more subsidence associated to extensional phases can be stable environment within the Late Cretaceous distinguished: paleogeography. It is important to point out Barremian to Early Aptian. that, along the southern limit of the shelf (South The depocenters are associated to very thick black Aquitaine margin), the Cenomanian carbonates shale deposits, while the surrounding carbonate unconformably rest over the Upper Albian sediments. platforms show a very low rate of sedimentation. This unconformity fades out northwards into the One of the main salt diapiric event also occurs during platform. Salt-lineaments of varied orientations as this time along the border faults of the newly formed well as circular diapirs were also enhanced in this basins by migration of the Triassic evaporites from apparently stable platform and in the Parentis Basin. the subsiding depocenters towards the edges. They are located mostly along major faults and fault- Latest Aptian to Early Albian. intersections, such as the diapirs near the city of Dax, The shelf-basin confi guration is acquired during this and along the oil-bearing structures of the Arzacq period. The basins are yet characterized by a very high Basin, (Fig. 6). rate of subsidence and sedimentation of black shales. The N-Pyrenean basin progressively becomes Halokinesis is still going on, such as at the edges equivalent to a Cenomanian to Maastrichtian B16 to B33 n° 2 - from Volume of the Aptian-Albian pull-apart basins and rhomb- foredeep located immediately to the north of North- grabens, e.g. the huge Audignon anticline to the Pyrenean Fault (NPF), thus bordering the European- north of the Arzacq Basin. The shelf-basin transition Iberian plate boundary. The entire fast-subsiding, is marked by a system of limy patch reefs while the turbidite-fi lled, mobile belt becomes progressively platforms surrounding the shelves show a low rate of the North Pyrenean Zone, where the major part of sedimentation. the orogenic thin-skinned deformation of the North- Late Albian. Pyrenees will take place (Zolnai 1971). During the

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell However, asaresultoftheongoing north-westward unconformity. sediments and/orthebasement,withasharpangular Chaudes” or“calcairesdescañons”overlay theearlier Cretaceous carbonateseriesofthe“calcairesdesEaux massive, thick(about500m)IberianUpper Cretaceous carbonateplatformdeveloped. The To theSouth, infl salt-structures actedaspaleogeographicbarriersand Zolnai 1975). Within theNorthPyreneanfurrow the the mobiledomainsofforedeep(Stevaux and material (salt,shale)arealsoemplaced,mainlyinto and salttectonics.Olistostromescomposedof Triassic the Maastrichtian. Transpression provoked wrenching marls andendedwithathickmudstoneseriesduring furrow bynow becamefi The fl northwards, from Turonian toLower Maastrichtian. prominent, theaxisofforedeepmigrated As compressionbetweenthetwo platesbecame Maurel E-W asymmetricandnarrow troughorfurrow (Moen- a singleN-Pyreneanbasin,whichcorrespondstoan Cenomanian, theen-echelonriftbasinsmerged into uenced thedistribution oftheturbiditicsystems. Figure 6-Structuralframework andPetroleum Provinces oftheSouth Aquitaine andN-Pyreneanbasins(Total). yschsedimentationinthedeepNorthPyrenean et al ., 1999). ontheIberianplate,anUpper ne-grained, dominatedby The easternandcentralpartsoftheforelandbasins west again. diachronous andoblique,progressingfromeastto the controlofongoingcompression,whichis paleogeography anditsbasinevolution areunder of relatively reducedtectonicactivity, the Tertiary Srivastava, 1991). After aDano-Paleocene period convergence betweenEuropeand Africa (Roestand The Paleocene was atimewithrelatively low plate Tertiary cannibalisation oftheplatformedges. Trough sediments,asaresultoftheprogressive known betweentheplatformsandNorthPyrenean then aretro-forelandbasin.Notransitionalfacies are (Iberian plate)areseparatedbyafl p7latforms tothenorth(Aquitaine)andsouth In conclusion, study. the NorthPyreneanequivalent fl Pyrenees. Itsconnectionwithorindependencefrom High Chaininthepresent-daycentralandwestern Iberian carbonateplatformalongtheareaof Senonian fl intraplate retro-forelandbasin,theSouthernUpper Pyrenean compressionandoftheformation ysch domainprogressedover theformer thetwo Upper Cretaceouscarbonate ysch basinisunder yc foredeep ysch 11-06-2004, 7:44:52 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

changed from marine to continental as topography large masses of coarse continental fanconglomerates developed and the amount of eroded material was (“poudingues”) deposited in successive sequences, in suffi cient to fi ll the basins. In the western Pyrenees the a suite of fans. crust would have recovered its initial thickness later The Ebro basin became closed and separated from than in the central and eastern Pyrenees as a result of the Atlantic because the tectonic relief growth during a greater extension of the Pyrenean crust during Early the inversion of the Lower Cretaceous basins in the Cretaceous times coupled with a younger and lesser western Pyrenees. Erosional debris of the Pyrenees amount of convergence. In this area Paleocene rocks and other surrounding chains of the Ebro basin are represented by deep-water carbonate and silici- (Iberian and Catalan Coastal Ranges) progressively clastic sediments deposited in continuity with the fi lled the basin and then backfi lled, to bury the fl anking Upper Cretaceous turbidites (Pujalte et al., 1989). thrust belts on its margins (Coney et al., 1996). This Two main events will arise : progressive backfi lling forced deformation to migrate 1. the N-Pyrenean foredeep basin will retreat from hindwards and as a consequence reactivation of east to west, and thus the related sedimentary facies previously developed thrust structures and break-back synchronously will do the same, recording the thrust sequences occurred (Vergés and Muñoz, 1990, orogenic evolution, horizontally and vertically. From Burbank et al., 1992b). The southern Pyrenees were east to west and from bottom to top, facies will pass almost completely buried by Early-Middle Miocene from syntectonic fl ysch facies to tidal deposits and times. then to syn- and post-orogenic fanglomerates. The greatest part of the Aquitaine Basin, to the north In detail: the Late Cretaceous-Paleocene time period of the orogenic foreland, nevertheless, remained is still marked by margin instability, with large shallow marine, until the general fi lling of the basin submarine collapses of carbonates mass-fl ows (see caused the sea to progressively retreat to the west. here below, Stop 1.2 at Le Tucq). The abrupt and subsequent Miocene-Pliocene re- In Late Paleocene-Eocene (Ypresian) rhythmic excavation of the southern Pyrenees and the Ebro sedimentation continued in the N-Pyrenean basin, basin to develop the present fl uvial system was some constituting a new thick fl ysch sequence. combination of the Miocene rifting of the western During the Early-Middle Eocene thrusting rate Mediterranean and the Messinian desiccation crisis. increased. Both foreland basins experienced a deepening which resulted into the widest extension Structural history of the Pyrenees of marine deposits in the Pyrenean foreland basins Inherited structures of Precambrian to Paleozoic (Puigdefàbregas et al., 1992, Burbank et al., 1992a). age affected the tectonic basement of the Pyrenean The thrust front in the southern side of the central orogeny, and had a fundamental infl uence on the Pyrenees strongly advanced because deformation of geometry of the Upper Jurassic to Upper Cretaceous the Mesozoic wedge on top of a weak detachment extensional (grabens and rift margins) and on the level (Triassic evaporites). Shallow marine deposits Upper Cretaceous to Tertiary compressive structures were deposited in the foreland as well as in the (frontal and lateral ramps). This combination of pre- piggy-back basins which demonstrate a subhorizontal rifting events produced three trends: mean topography over the southern frontal wedge. - N 20°E to 40°E: corresponding to the Garonne Strongly subsident troughs fi lled by turbiditic - Villefranche fault zone crossing through Toulouse sequences were developed south of the uplifted city. It is active in Late Variscan times as a left-lateral basement in the footwall of the upper thrust sheets. strike slip fault. Some relief existed hindwards as evidenced by the - N 90°E to N 120°E: its corresponds to the Celt- N-S river systems supplying basement clastics and Aquitaine hinge-line and to the North Pyrenean fault by the geometry and location of proximal alluvial zone which acts as a left-lateral strike-slip fault in B16 to B33 n° 2 - from Volume fans. A maximum topography of 1-2 km has been Late Variscan times. calculated based on paleotopographic reconstructions - N 160°E represented in the Axial Zone by kilometer- and fl exural modelling (Vergés et al., 1995, Millán et high folds and incipient cleavage of Variscan age. al., 1995). A succession of events affected the N-Pyrenean In Oligocene along the future Pyrenean foothills domain (fi g. 4 and 5), after the Variscan orogeny. i.e. the orogenic foreland, sedimentation became progressively more terrigenous from east to west, with The fi rst post-Variscan rifting attempt took place

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell place alongtheEuropean-Iberianplateboundaryin Biscay. Although themajortranscurrentmotiontakes Plate, whichresultedintheopeningofBay extension andanticlockwise rotationoftheIberian marked bytheparoxysmofgeneralnorth-south The EarlyCretaceous Transtension andpull-apartbasins sets offaults). (essentially theN20°E,50°E-70°Eand160°E controlled primarilybytheinheritedbasementfaults a result,theJurassicsedimentationappearstobe characterized bydiffuse W-NW/E-SE extension. As phase. In Aquitaine, theJurassicpaleogeography is between thetwo platesisrelatedtothatdeformation transtensional faults. A regional sinistralwrenching by N20°Eright-lateraland160°Eleft-lateral which createsE-Wstrikingnormalfaults connected Cretaceous “revolution” or phase oftheLateJurassic(Montagné,1986)-Early The BayofBiscayriftingcorrespondstotheextensive propagation totheNorthofMid-AtlanticRidge. the openingofCentral Atlantic Oceanandthe This periodischaracterizedbythebeginning of Jurassic- EarlytoMid-Cretaceous rifting well asgravity tectonics(Zolnaï,1975). km thick,allowed diapirism,foldingandthrusting,as detachment horizon,whichlocallycanbemorethan1 The thickKeuper evaporitic andshalypotential plate boundary, but alsotothenorth. and theLiassicanhydrites),nearIberian-European transition (approximatelybetweentheKeuper salts fl during theLate Triassic. Submarine(ophitic)volcanic edge, whichalternatedwithdeepcorridorsalready Grand Rieu)wereformedalongthesouthernbasin- Fault Zone).Highemerging blocks(e.g. Arbailles, the southernbasinedge,(nearNorthPyrenean event basin inthecentreofarea,while The Triassic -Jurassic (Gapillou 1981)nearStJeanPieddePort. SW-oriented) ElizondotroughinBasquecountry 1,000 m.Oneofthesegrabensisthetransverse (NE- clastics andvolcanic fl the basinitself;they arefi grabens areknown inthePyreneesaswellunder deformed series.RoughlyN-SandE-Woriented, The Permianliesunconformablyonthepreviously the latestagesofpost-variscan peneplanation. as soonthe ows andintrusionstookplaceatthe Triassic-Jurassic Triassic prevailed inboththeParentis Basin,andalong was widelydepositedinafl EARLY PERMIAN ows, withthicknessesupto geologicalevolution is lled withredcontinental third riftingepisode a secondrifting : , i.e.during at-lying

Iberian platebecameincompressionalcontactwith Since atleastthebeginning ofLateCretaceous,the Compression comesfromtheEast... extension/collision Late Cretaceous – Tertiary diachronous known as“N-Pyreneanmetamorphism”. metamorphism allalongtheN-Pyreneanfault zone, the remobilizationoflherzolitesandapeculiarshear and Europeanplates(Plate1,fi and thedifferential driftmovements oftheIberian of Biscaysea-fl and theareasouthof Tarbes. Correlative totheBay emplaced withinthefl lava fl In themeantimetholeiticbasaltmasses(pillows and Cenomanian). turbidite (fl the basalwildfl Souquet andDebroas1981)tothenorth. Above which depositedintothedeepsea-arm(“aulacogen”, Pyrenees, offering sourceareasforcoarseclastics, country (BoirieandSouquet1982),orintheCentral to thesouthofMendibelzamassifinBasque the present-dayHighChainbecameemergent e.g. the Iberianmargin andlandmass. Large areasof faulted tiltedblocks(often-kmwidth),calved from opening oftheBayBiscayprogressedeastward, During LateJurassicandEarlyCretaceous,asthe North-Iberian marginandoceanisation: array. is lostbeyond thetransverse NE-SWPamplona- fault the different elementsoftheBasqueMassifs.Itstrace splits intoseveral E-Worientedbranches,separating easternmost PyreneestoBasquecountry, whereit over 500kminsuccessive segments, betweenthe Fault The W-E to WNW-ESE oriented and uplifts(withE-WNNW-SSE trendingedges. Richert andZolnaï,1995,R.Miranda Avilès, 2002) basins orpotentiallypull-apart(Bourrouilh, a setofNW-SE rapidlysubsiding,diamond-shaped (Canérot, 1989),allowing forthedevelopment of platform isdislocatedalongthesemainfault zones directions areusedasminorrelayfaults. The Jurassic 110°E inheritedfaults whiletheN40°Eand160°E sedimentation iscontrolledbytheactivation ofN by diffuse strike-slip movements. The highrateof Aquitaine Basin)totheEbroplatformisaffected entire region fromtheParentis basin(northofthe a Baja-Californiastyle(Miranda Avilès, 2002),the ows aswellsheeteddykes andsills)were was initiallyabraidedfault-system. Itstretches ysch) sequencewas deposited(Albian- oor spreading,thestrike-slip tectonics yschs, thefi ysch furrow, betweenBilbao rst thicksandy-shaly gs. 1and2),provoked North Pyrenean 27-05-2004, 8:40:48 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

the NW moving African plate. Iberia progressively the sites for the major dislocations, and (b) major crushed the space between its northern margin and formations of the sedimentary column (e. g. Keuper the European plate. Compression was diffuse during salt, Lower Cretaceous marls, Albian to Tertiary Late Albian to Cenomanian; it became effective fl ysch and molasse series) were still extremely as early as in the mid Late Cretaceous (Turonian- incompetent during the period of compression. Large, Senonian) in the eastern part of the Pyrenees (Henry open synclines and anticlines were fi rst formed; the and Mattauer 1972, Souquet and Deramond 1989), synclines later became overthrusted, overturned and propagated progressively to the west during the and/or thinned, sheared by the overriding anticlines. Senonian. Compression provoked gigantic linear Specifi c structures or “ nappes ” were thus generated, gravity slope sequences or “Evolutionary-mass fl ow- which would seem uncommon in areas of greater megaturbidites” (Bourrouilh et al. 1983), which can crustal rigidity and with more competent sedimentary reach 90 km in length and a thickness of about 60 m. sequences (there are very few true fl at-and-ramp Similarly, in the southern Pyrenean Basin, but during thrusts and “duplexes” in the northern Pyrenees, the Eocene, compression is accompanied by the Moen-Maurel et al., 1999). emergence of a syntectonic cycle of gigantic mass- fl ow-megaturbidites extending over 140 km in map The North and South Pyrenean Thrust Fronts are view, and more than 200 m thick (Soler et al., 1970, actually tectonic envelopes, and not continuous, Johns et al., 1981). unique, sole faults. They are composed by segments The main north-south compressional event of which relay each other, sometimes with important the Pyrenees began nevertheless from MIDDLE offsets. On the Northern Pyrenean side, several EOCENE onward. The main ductile deformation structural arcs exist: the Basque Arc, along the north- occurred at the plate boundary, within the North western Pyrenees, the Lannemezan Arc in the central Pyrenean Fault Zone, which represents the most northern Pyrenees etc., but also on the southern strongly compressed, schistosed, crushed part of the side, such as the Graus-Tremp Arc in the southern belt (Choukroune, 1974), and along the northern Pyrenees; their tips all lay in lateral or oblique ramps edge of the Iberian block. Former normal faults and which were inherited from the rift basin edges. Two hingelines were inverted into overthrusts, the northern well-explored surface anticlines are centered in the limit of the highly compressed zone corresponding to northern arcs : the Ste. Suzanne structure to the west, the earlier boundary between the fl ysch furrow and and the “Petites Pyrénées” in the Central Zone. Thrust the northern carbonate plaform. This long-lived sheets do not exceed 12 km. tectonic edge has thus become the North Pyrenean Thrust Front. The Southern thrust sheets are therefore the most The main structural events created or re-activated in spectacular ones: this period from Late Cretaceous (Maastrichtian) to From Early Eocene to Oligocene, the Upper Thrust Oligocene are: Sheets (Muñoz et al. 1986) or the South Pyrenean N 110°E folds, cleavage, stylolites, reverse faults and Central Unit (Seguret, 1972), composed of Mesozoic thrust planes either to the north or to the south. to syntectonic Tertiary formations, were successively N 20°E to 40°E, left-lateral lateral ramps. transported along a sole of Keuper evaporites, argilites N 160°E, right-lateral lateral ramps. and marls (Bresson, 1903, Seguret, 1972, Muñoz et Normal faults are also present: in some areas they al. 1986). They are, from East to West, the Pedraforca, are striking N-S; some minor sub-E-W faults are also Boixols, Montsec, Cotiella Thrust sheets; the front of created in close relation to major thrusts trending E-W all outlines the South-Pyrenean Front Thrust, which and salt ridge keystone collapse. produced the Sierras Marginales (plate 1). During the orogeny, several compressional episodes In the High Chain, these cover thrust sheets root into B16 to B33 n° 2 - from Volume followed each other, the younger, more external the Upper Paleozoic basement, along with the deeper faults (sole-faults of allochthonous units or rafts) thrusts which are the Nogueras and the Gavarnie- deforming the earlier, more internal ones in a piggy- Mont Perdu Units. back fashion. The deformation and structural styles The total shortening of the Pyrenees is evaluated, appear controlled by the rheology of the material depending on the authors, between 100 to 160 km. involved: (a) the already fractured deep basement Pyrenean orogeny and inversion continued during complex was involved in the compression, setting the MIOCENE.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell resulting inthediscoveries offi interest moved northward towards thebasinedges, during thesameperiod.In1970’s, exploration 7 Gm3 gas(110to250 BCF) werealsodiscovered Cassourat …) withaccumulations rangingfrom 3 to smaller sizedfi a surface anticline).Inthesame Arzacq basin,several discovery was madeusing2Dseismicdatashowing gas fi drilled ongravimetric anomalies)andtheMeillon Gm3 gas–9.2TCF)(discovery1951 (260 wellswere The very latest, Neotectonic relaxation anduplift 160°E” (right-andleft-lateral). (mostly left-lateralduetoS-compression)and“N- the basementfaults produced“N-40°E”dip-slip 2002) aswellrotationalconstrainsinducedalong Partitioning ofthedeformation(seeMiranda Avilès, Lacq oilfi was thenconfi on asurface anticline. The area’s positive potential (Comminges Basin). The discovery wellwas drilled Marcet GasFieldin1939(8 Gm3 ofgas–290BCF) in the1930’s andresultedinthediscovery oftheSt- South Aquitaine basins(forelandandfoothills)started since Romantimes,petroleumexploration ofthe province ofFrance. Although seepshave beenknown The Aquitaine arearepresentsthelargest oilandgas History Petroleum explorationframework trends areclearlyidentifi Bonrepos-Montastruc, fi (Pecorade, Vic Bilh,Lagrave, CasteraLouand They representthe mainpetroleumobjectives; their Jurassic dolomites andBarremian limestones Reservoirs province”) (fi along theedgesofforelandbasin(the“saltridges Meillon” domain),andanoiltrendtothenorth of thePyreneesFold and Thrust Belt (the“Lacq- along theleadingedgeandproximalforeland southern vergence tonearvertical. former overthrust sheets,back-steepeningthoseof post-orogenic isostaticadjustment,alsodeformedthe by erosion. This upliftmovement, possiblyalate-or m MSL.),wherePaleozoic outcropswereexhumed day High“axial”mountainChain(+2,000to+3,500 former southern(Iberian)margin toformthepresent- an important episode ofthePyreneanorogeny seemstohave been eld in1965(65 Gm3 gas–2.3 TCF) (this eld in1949,thedeepgiantLacqgasfi (Fig. 7). g. 6and7). relief development rmed bythediscoveries oftheupper elds (Ucha/, Rousse, PLIOCENE toHOLOCENE ed: agastrendtothesouth g 6. w hydrocarbon Two 6). g. ve sizableoilfi , whichupliftedthe eld in elds

most effi and anhydritesLower Aptian shalesrepresent the Hauterivian to Valanginian shales,Barremianshales Barremian andJurassic plays Seals transcurrent fault system. away fromtheimmediate settingofthe Tertiary Seron therefore reservoir capacitydecreasesignifi of theLagrave Fieldwheredolomitizationand Pyrenean faults. Itisdemonstratedbytheexample secondary dolomitizationinthevicinityofmain linked tothehighenergy facies distribution andtoa limestones (15to20%matrixporosity)areclosely platform. The goodreservoir characteristicsofthese (200 m to250 metres thick)ofthe Upper Cretaceous They correspondtotheLower Senonianlimestones The UpperCretaceous reservoirs fracturation. and permeabilityarealsoenhancedbyintense of theLacqgiantfi The Lower Barremian fracturing. again relatively poorbut enhancedbytheintense porosities rangingfrom 10 to15%.Permeabilityis the UpperBarremianlimestones,whichdisplay Within thissameareathereservoirs alsoinclude intervals characterizedbyahighenergy ofdeposition. again primarilyassociatedwithintensefracturingand better, they remainpoor(2to10%).Productionis Even thoughthepetrophysicalcharacteristicsare preserved asreservoirs withintheJurassicsequence. and Vic Bilhfi In theJurassic outershelf well productivity. vugs (duetosecondarydiagenesis),allowing forgood permeability isprimarilyduetojointfracturesand Meillon dolomite).For theseformations,effective porosity fortheManodolomitesand 4 to8%forthe characteristics areratherpoor(2to4%matrix structures. For thesetwo reservoirs thepetrophysical along theUcha,LacommandeandRoussetrendof gas-bearing ontheMeillongas-fi breccias. These reservoirs aretotallyorpartially Mano dolomites(150to200 m thick)andGarlin dolomites (200 m thickinaverage), thePortlandian represented bytheLower KimmeridgianMeillon On theJurassic easternshelf paleogeographic provinces describedearlier. domains canbedistinguishedinaccordancewiththe Earliest Cretaceouspaleogeographicsetting. Two occurrence iscloselylinked totheJurassicand (Fig. 7). cient sealsfortheoiland gas fi elds), onlytheManodolomitesare eld. Itslow porosities(2-11%) isalsooneofthereservoirs tothewest(Lacq,Pecorade eld trendaswell thereservoirs are elds inthe 27-05-2004, 8:40:52 cantly WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Figure 7 - Aquitaine basin : stratigraphic chart and Petroleum Systems (Total).

Arzacq basin. level of the Lower Cretaceous depocenters of the Upper Cretaceous plays Arzacq Basin and occurred during the Tertiary on Seals are composed of the Upper Senonian shaly both sides of the basin (fi g. 8). or marly intervals and by the Lower Tertiary slope The Kimmeridgian source rocks appear to have the shales. best potential. The organic matter is again primarily Source rocks (Fig. 7). of marine origin (type II-III). Important reserves of oil and gas have been discovered Trap types and hydrocarbon charge (Fig. 8). in the Aquitaine Basin, implying that sources with a The traps for the different fi elds are clearly related regional extension and good petroleum potential are to structures which are inherited from the Early present in order to expel signifi cant quantities of oil Cretaceous extension (platform to basin transition) and gas. Although some source potential has been and its associated salt tectonics along the limits recognized in the Tertiary, Albian and Liassic shales, of the basins (erosional pinch-out of the Jurassic these formations are low-quality source rocks. and Barremian reservoirs). These traps have been The main source rocks are clearly associated to the enhanced by the Pyrenean orogeny. Some of them are

Barremian and Kimmeridgian formations ( Fm) located in the Pyrenean fold and thrust belt (Saucede B16 to B33 n° 2 - from Volume as shown by the source-to-oil condensate and source- and ); but most occur within the proximal to-gas correlations. (Lacq, Meillon, Ucha, Lacommande, Rousse fi elds) The Barremian organic matter is primarily of marine and distal forelands (Vic Bilh, Castera Lou, Lagrave). origin including woody material (type II-III). Across Exceptional productive traps can be even found in the basin the oil window is reached at – 3,000 metres episyenites (Moen-Maurel et al., 1996). on average, while the gas window is reached at – 4,000 metres (fi g. 8). It is noteworthy that expulsion of hydrocarbons started during the Late Albian at the

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell The anticlockwiserotationoftheIberianplatewith 2) Platemotionvector evolution : Moen-Maurel arc position(andpreservingitspetroleumsystems, basins oftheEuropeanplateinalittledeformedretro- mainly affected theIberianplate, leaving therift Pyrenean (LateCretaceoustoEocene)inversion differentiated passive margins. the BayofBiscaytoproduceanoceanicfl times. However extension was never suffi basement fabrics thatwereacquiredinPaleozoic echelon, asaresultofthecontrolprevious oblique can beinvestigated inthesubsurface today, wereen- At theparoxysmof Albian rifting,many riftsthat to theEbrobasinandCantabriandomainSouth. wide) extending fromtheParentis basintothenorth the tethyandomainover abroadarea(400kmN-S of riftingfrom Triassic to Albian atthewesterntipof The continentalcrusthereunderwentdiffuse stages 1) Crustalcharacteristics characteristics shouldbepointedout: In comparisontoothersFTB,thefollowing striking Fold-and-Thrusts Belts Comparison withother et al ., 1999). Figure 8- Aquitaine-Arzacq Basin:Evolution ofSourceRocks (Total). : cient eastof oor andtwo European platesfromEarly The obliqueextension betweentheIberianand the or strike-slip intheeast. the sametimeextension inthewestandcompression and senseofthedisplacementvectors, producingat to Cenomanianledvariations intrend,magnitude respect totheEuropeanplatefromEarlyCretaceous The existence of Triassic evaporites ledtohalotectonics 3) Salttectonics any majoroblique collision. therefore thecover deformationcannotaccommodate thrust tipsstillexist atthe outcroporinthesubsurface, phases from Turonian toMiocene.Nevertheless most to measuretheamountofstrike-slip intheshortening fl the Triassic evaporites andintheUpperCretaceous During collisiontheuseofpotentialdetachmentsin al more than5%horizontalstretching,Moen-Maurel with minorhorizontaldisplacementsalongfaults (no diffuse extension whichproduceden-echelongrabens (supposedly reachingtensofkminstrike-slip), and strike-slip whichfocusedonspecifi led tothepartitioningofdeformationbetween ysch ledtovarying structuralstylesmakingitdiffi ., 1999). Cretaceous toCenomanian c shear fault zones fault shear c 27-05-2004, 8:40:56 cult et WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

from Late Jurassic onward. Salt pillows and ridges were - the petroleum system trilogy series were protected re-activated as anticlines during compression while from uplift and erosion over the Parentis and North- evaporite-rich widespread units acted as detachments Pyrenean basins since they remain situated in the and thrust soles. The salt mobility triggered enhanced outer rim of the collision, in a little affected retroarc amplitude and curvature in fold axes, non-cylindricity position. After rifting subsidence, the additional burial and virgation, as well as a diachronous record of the which was achieved with the foredeep deposition led tectonic stress events. When salt is involved onset and to reaching the gas window and to the development of end ages of tectonic events may vary through time and large gas traps. space making it diffi cult to tie deformation to stress - salt tectonics eventually enhanced the amplitude of and/or plate tectonics. traps and their closure. Such providence makes the 4) Fold-and-Thrust belt structural style: Aquitaine oil and gas structures quite similar to North Thick-skinned thrusting affected the Iberian plate Sea oil and gas fi elds. margin along the underthrusting plane, resulting in antiformal stacks of basement (Paleozoic) producing To conclude, it should fi nally be emphasized that fi rst of the axial zone of the mountain range. The steep dips all, the structural history of the whole area is controlled of the basement ramps may have been facilitated by by a N110°E plate boundary crustal anomaly, running the oblique component of the collision initial vector from West Greenland to the Tethys and then to the and the existence of steep and weak shear zones from modern Mediterranean (R. Bourrouilh, 1970, 1973). the Early Cretaceous drift stage (such as the North- This lineament is evidenced by the N-Pyrenean Fault Pyrenean Faut system). and its peculiar metamorphism, the thinning of the Thin-skinned thrusting was possible when cover crust, the Biscay rifting, the injection of the mantle detachments could be activated over large distances: lherzolites. The plate boundary crustal anomaly seems for the southern FTB it resulted in transferring the to be Pre-Triassic, putting in contact an Iberian deeply uplift and the 100 km range shortening in piggy-back structured (with pre-existing crustal detachment faults) fashion over a few large thrust sheets towards the and thick continental lithosphere to the south, and a external sierras, and for the northern FTB it resulted in thin, less structured European one to the north. The producing a retroarc and in accommodating the axial Late Cretaceous to Tertiary tectonic shortening is overload with thrusts and nappes mostly affecting the asymmetric, being estimated, depending on the authors Upper Cretaceous to Eocene fl ysch basins. and the area, at 100 to 160 km over the Iberian plate, The shape and magnitude of the thrust sheets was and at 5 to 12 km over the European one. strongly infl uenced by the attitude and potential friction In its western part (Bay of Biscay), the Pyrenean of the detachment stratigraphic horizons: salt ridges in orogen is incomplete. To the east, it interferes with the the north favoured large amplitude (up to 5 km) upright Betico-Kabylo-Alpine orogen and is overprinted by the and overturned when they slid over fl ysch units. Rift extensive Neogene Mediterranean structures. grabens and fl ysch basins morphology infl uenced The result of the collision in the Pyrenees produces the location of both frontal and lateral ramps. This an asymmetric fan-shaped orogen, resulting from the stratigraphic control leads to structural styles that are crustal ductile underthrusting or underplating of the common along the alpine (tethyan) orogen, unlike Iberian Precambrian-Paleozoic basement underneath craton margin orogens where isopach formations the European plate. rather, led to fl at-and-ramp thrust propagation such as in the Appalachians and the Rocky Mountains. The Pyrenean orogenic complex of the Pyrenees 5) Petroleum evaluation is devoid of granitic intrusions and syn-orogenic The North-Pyrenean retro-arc basin was a prolifi c oil volcanism, there are no ophiolitic masses and the and gas province with giant fi elds (Perrodon, 1980) known metamorphism is restricted to the trace of B16 to B33 n° 2 - from Volume because: the North Pyrenean Fault Complex (Choukroune - the petroleum system trilogy (source rock, reservoir 1974). This indicates that the major orogenic event and seal) belonged to pre- and syn-rift series which are in the area was the variscan one (tectonics with major usually characterized by extensive and stable marine crustal shortening, penetrative metamorphism and sedimentation making hydrocarbon migration easy granitization). Parts of this structural crustal heritage (or and exploration more predictable even in areas of regional fabrics) were activated during the Mesozoic poorly imaged seismic prospecting (Moen-Maurel et extensions, re-utilized by the Late Cretaceous to al, 1995). Tertiary Pyrenean orogenic convergence.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell Field Itinerary Upper Cretaceous fl Le Tucq : theNorth-Pyrenean margin andthe Stop 2.1: from Pau toOloron SainteMarie [email protected] ** TOTAL, 64018Pau Cedex, France,e-mail : e-mail : Avenue desFacultés, 33405 Talence Cedex, France, *Laboratoire CIBAMAR, Université de Bordeaux1, By R.Bourrouilh*andL.Moen-Maurel**, I. A transectofthenorthern pyrenees Panorama ofthePyrenees :fi Stop 1.1: Briefi A. Teixell By R.Bourrouilh,L.Moen-Maurel,J. Muñoz And Welcome tothefi Pau

ng andintroductiontotheField Trip. [email protected] . Figure 1.1-GeologicalviewofthePyrenees,fromBoulevarddesPau. eld tripandthePyrenees ysch : DAY 1 DAY 2 gure 1.1. Structural andsedimentologicallandscape: adjacent cartrack. and 2.1c,Guillampeausection)alongthesideof and themeasuredsection(fi section islocatedinthecurve oftheroad(fi the road,justatlocality“Le Tucq”. The outcrop Access: the silici-clasticPaleocene sedimentation. closure ofthebasin,andwestward progradationof is now covered byroadwork) whichiscoeval withthe Cretaceous-Paleocene sedimentation(but theKTlimit The sectionstudiedinthisStoppertainstoUpper can reach7kminthickness. Biscay. The North-Pyreneanfl Ma totoday, forming,uptonow, themodernBayof and thefurrow rapidlyretreatedwestwards, from80 as recently80Maago,duringtheLateCretaceous However, theareaunderwentcompressionaltectonics up bysynriftanddriftcalcareousCretaceousFlysch. N-Pyrenean basinortrough,whichwas rapidlyfi basins merged inalongandnarrow furrow orthe black shales.DuringCenomanian(-96Ma),rifted created andfi Bay ofBiscay. The N-Pyreneanriftedbasinswere as apassive riftedmargin duringtheopeningof Introduction fi gures 2.1a,b,c,2.1d theStopisonD934,rightsideof : theSouth Aquitaine margin developed lled bysyn-riftLower Cretaceous gure 2.1b, Tucq section yc sedimentation, ysch gure 1.1a) 27-05-2004, 8:41:00 theD lled WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Figure 2.1a - Flysch section at Guillampeau, top is on the right.

934 crosscuts the Upper Cretaceous fl ysch. The curve of the river, as well as that of the road are provoked by the top of the Upper Cretaceous fl ysch, containing large white mudstone mudfl ows, as well as reworked Triassic (fi rst diapiric) gravity slabs mass-fl ows, silici-clastic mass fl ows etc. In the landscape, the curve is marked by an old chalk oven, and prolonged by a smooth wooded cliff. Along the western side of the road two fi eld sections have been measured in the gently north-dipping Figure 2.1b - measured section at Le Tucq, from turbiditic and mass-fl ow sequences with internal R.Bourrouilh et al., 1993, unpub. data. slumps (Bourrouilh, Montagné and Doyle, 1993, unpublished data). and anoxic mud clasts, and by silici-clastic Bouma- The fi rst one, or the Tucq section is just on the curve type turbidites. Measured sedimentary fold axes are, of the road, in front of the Tucq restaurant, but is now successively, from bottom to top : N 60°, dip 35°E covered by road work (fi gure 2.1b): (unit 2, lower part), N 83°, dip 10° SE (small slump, The Upper-Cretaceous to Paleocene section is unit 3), N 175° (large slump, unit 3), N 90° to 110° 27 m thick and represents a mixed silici-clastic- (clast, base of unit 4), N 115°, dip 25°N, (base of unit carbonate sedimentation. Five sedimentary units 5), N 115°, dip 22° N-NE. can be distinguished. On the four basal units, the However, carbonate gravity sedimentation comes sedimentation is mainly constituted by successive back again and forms unit 5, considered the base of a silici-clastic mass-fl ow deposits, reworked mudstones large carbonate mud-fl ow. Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 2.1ca - measured section 1 at Guillampeau, from Figure 2.1cb - measured section 2 at Guillampeau, from R.Bourrouilh et al., 1993, unpub. data. R. Bourrouilh et al. 1993, unpub. data.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell migration oftheinterplatecompression. basin-Bay ofBiscay, duetotheprogressive westward shelf andtotheprogressive closureoftheN-Pyrenean amount ofcarbonatesdepositedontheedge the Ypresian. This relative instabilityisduetoahigh vary asmuchbelow intheCampanianandabove in thicknesses acrosstheNorth-Pyreneandomaindonot Late CretaceoustotheEarlyPaleocene even though Pyrenean basinappeartobeinstableduringthelate Conclusions: 2.1cb) measured alongthesideofroad(fi The secondoneortheGuillampeausection 1993, unpub. data. Figure 2.1d-Schematic reconstructionoftheDano-Paleocene Aquitaine marginatLeTucq, fromR.Bourrouilhetal. fi gure 2.1d : themargins oftheN- Figure 2.2-Panoramic viewoftheMailh Arrouy andOssau Valley (Total). g. 2.1caand is G. Montagné,1986,Seyve, 1984. For furtherinformation: Stop 2.2: Laruns, atSevignacq, ontherighttake thesmallroad Access: which isthelocallanguage: Aüssaü =highvalley). northward throughtheOssau Valley (inBéarnais, the HighRangeandPicduMidid’Ossau,fl frontal vallum oftheglacier, whichwentdown from The smallvillageofSevignacq isbuilt onthemorainic and neotectonics:Sévignacq the Ossau Valley: uplifting,glaciers leaving themainroadD934fromPau to

Stevaux andZolnaï,1975,

(fi gure 2.2) 27-05-2004, 8:41:06 owing WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

D 232, from Sevignacq to . The Stop is located relaxation at present. Rising of the mountain all after leaving Sevignacq and a few hundred metres around provoked in turn the Ossau river to change its down, after the cemetery, in the plain. course from north to west, cutting the moraine and the Structural landscape: the panorama shows, from left Urgonian limestone to the West. to right: the Mesozoic high mountain of Mont du Rey, The Ossau river now fl ows towards the west after the glacial U-shaped valley of Ossau, with the high cutting the frontal moraine and the cretaceous bedrock chain and the faulted caldera of Pic du Midi d’Ossau in a narrow deep neo-tectonic canyon, located in the in the background, and on the right, the Mesozoic western outskirts of village. Lazerque (1,368m) and Mailh Arrouy (1,251m) But an underground northward paleocirculation of the mountain range. Ossau waters still exists and fl ows to the north, under Interpretation: the Ossau glacier was one of the most the frontal moraine and producing a resurgent spring important Würmian Pyrenean glaciers, which fl owed in the karstifi ed limestone north of Rébénacq. There, south to north, from the High Chain to Sevignacq. At the river is called “Luy du Néez”. its front, it produced a large moraine, which surrounds us as a morainic vallum. Deglaciation began some Stop 2.3: 11,000 years ago and the glacier was about 1,000 m Arudy: opening of the rift as recorded by mud thick here. Melting of the ice provoked a reduction mound markers (fi g. 2.3a and 2.3b) of the ice weight on the crustal lithosphere, which Introduction: at the village of Arudy, several Aptian- began an upward isostatic buoyancy and slowly rose Albian mud-mounds are or were worked for marble. up. The mountain range is still being uplifted under Geological studies (Bouroullec et al., 1979), generally

Figure 2.3a - Stratigraphy and geodynamic evolution of the Arudy basin, from R. Bourrouilh, 2000. Volume n° 2 - from B16 to B33 n° 2 - from Volume

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell to thequarry, pastametalgate. left onagravel roadcrossingtheforest andleadingup West (Lurbe-St-Christaudirection). After 1km,turn own risk.Northof Arudy, follow D918towards the Visiting thequarry, even whenauthorized,isatyour at thePaloma quarry alongthe Arudy toLurbe road. Laplace foraccessauthorizationwellbeforevisiting excursion. Access tothe quarry isrestricted. Ask Mr Dela quarry)andmudmound,willbevisitedinthis Access: development stageofthemud-moundcomplex. into theblackshalebasinof Arudy duringthelatest which representanuppermost Aptian mud-moundslid Here wewillonlyvisittheBoisduBagerquarry, their originalenvironment. they couldhave beengravitationally displacedfrom buildups couldbenotintheiroriginalpositionorthat changes but they didnotconsiderthatsomeofthese studied therelationshipofbuildups tosealevels basin. LenobleetCanérot(1993)and(1996), large blocksthat have slumpedintotheblackshale some reefsandmud-moundsof Arudy wereinfact sedimentological dataontheareaandtosuggestthat Digbehi (1987)was thefi dealt withstratigraphyandmicropaleontology. onlytheBoisduBagerquarry(orBorde Figure 2.3b-Sketch oftheBoisduBagerquarry, asvisiblein1997,fromR.Bourrouilh,2000. rst topresentconsistent can tolerateacertainamountofturbidityinthewater. microsolenids candevelop inquitedeepwater and corals. According toL.Beauvais (pers.comm. 1995), massive grey mudstonescontainingfl situated 2kmsouth-westof Arudy. Itconsistsof We willfocushereontheBoisduBagermud-mound, continent (Plate1,fi spreading oftheBayBiscayontoEuropean indicating theeastward progressionofseafl intruded bybasicvolcanism withfl basins. These pull-apartbasinswereprogressively These build-ups grew inacontext ofanoxicpull-apart Albian reefsandmud-mounds(Fig.2.3a2.3b). this platformwas marked bythegrowth of Aptian- the smallvillageof Arudy, southofthecityPau, Aptian-Albian carbonateplatformdeveloped: near and Ammonitic blackshalesweredeposited. Then an invaded theareasouth ofPau duringtheBarremian lagoonal carbonates.FromtheBayofBiscay, the sea sandstones (GrèsdeLacq),thenbyLower Barremian Cretaceous disconformityisoverlain bycontinental transgressive sequence:anUpperJurassictoLower sequence (Fig.2.3a)shows atypicalextensional and southern edgeoftheN-Pyreneanrift,stratigraphic Structural landscape g. 1and2). (R.Bourrouilh,2000):onthe at microsolenidae oods ofbasalts, 27-05-2004, 8:41:15 oor WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Those corals have umbrella-shaped morphologies, grew near the aphotic-subphotic zone transition, and indicating a low energy environment; they grow in certainly below storm wave base (no evidence of successive layers, indicating the stratifi cation and the wave action). Stratigraphy and original position of the upper part of the mound. mound is shown by the layering of microsolenids (So The base of the mound shows a locally deformed on Fig. 2.3b). contact with the underlying black shales (Fig. 2.3b). 2. Due both to growth and to the opening of the Along the basal contact, the lower part of the mound Arudy Basin, the mound slid and rotated 65° shows a slump breccia, with large mud-mound clockwise towards the NE (N 30°E). This rotation elongated clasts, some of them with microsolenidae, produced emergence of the SW fl ank of the mound; embedded in a black shale matrix. The mound also this emergence does not seem to refl ect a sea level exhibits two layers of black shale, locally contorted fall, as proposed by Canérot (1996). Emergence was and with load pockets. These layers of black shales accompanied by aerial and karstic erosion of the can be interpreted as recurrence of mud sedimentation, mound. The fl ank of the mound is eroded by karstic or they refl ect shale intrusions into the mound which cavities. Karstic erosion penetrated deep into the dead slid downwards with the mound itself. Observation mound, resulting in the formation of a large karstic of the orientation of the microsolenids show that cavity, which was then fi lled by a breccia (Fig. 2 .3b). these two black shales are obliquely oriented, and A large part of the breccia is autochtonous, but blocks clearly indicate that the mud-mound has tilted over of overlying shallow water units, some as long as 2 to an angle of about 90° from its normal position, metres, also fell down in the cavity. considering that the concave side of the umbrella- 3. These clasts are interpreted here as reworked shaped microsolenids faces upwards. The body of parts of coarse graded supratidal to intertidal storm the mound consist of massive grey microsolenidae deposits (Fig. 2.3b). The original deposits, where mudstones but it also shows a large karstic erosional they originate, are not observable in place, laterally cavity which refl ects emergence (Canérot, 1996). The or directly overlying the mound, but the presence of cave is fi lled with a karstic breccia, partly originating such clasts among the karstic breccia testify that near from the mound itself. (Fig. 2.3b). The breccia the emerged mound, supratidal to intertidal storm is partly dolomitized and locally impregnated by sediments were deposited. These fl at-lying clasts bitumen. indicate horizontal bedding during the karstifi cation In order to determine the diagenesis of the mound period, which is in agreement with the geometry of and the quality of the marmoreal limestone, a new the karstifi cation. We can suppose that the storm geophysical tool, the electrostatic quadripole was deposits have been eroded, broken and taken away as used (Benderitter et al, 1997). A precise resistivity clasts, which fell down in the karstic cavity. map of the diagenesis and of the fracturing was 4. Renewed tectonic activity led to an anticlockwise obtained, showing the mud-mound build-up, the 125° rotation of the mound towards the SW (N karstic cave and its brecciated karstic infi ll. 210°E). As a result, the mud-mound collapsed and This side of the mound is karstifi ed and the karstic slid down into the deep black shale basin, where it cavities are fi lled with black shales (Fig. 2.3b). This was buried, forming a large olistolith (the mound is area presents a white to light grey colour and it is covered up by, and embedded into the black shales). largely dolomitized. Study of the dolomitization The slumping resulted in the formation of a slump shows that this refl ects the contact of the mound with breccia (on the base of the mound, 4, Fig. 2.3b), and the phreatic lens (Bourrouilh-Le Jan, 1973, 1975), of the two intrusive black shale layers, parallel to the related to emergence. basal surface of the mound (4, Fig. 2.3b). These black Geodynamic interpretation: a provisional scenario shale layers are deformed and contorted. for this mound development is proposed hereafter 5. The dead mound was then buried in the black shales B16 to B33 n° 2 - from Volume based on geometry, stratifi cation, geopetal structures, and later in the basin evolution, oil migrated into the karst, fi lling of the karst, diagenesis (Fig. 2.3b) The karstic cave (5, Fig. 2.3b). following numbers refer to the numbers on Fig. 2.3b: 6. The thermal development which matured the oil 1. The Bois du Bager mud-mound began to develop also seems to have been responsible for exfoliation as soon as turbiditic black shale deposition input of the karstic cave wall, above the reworked decreased signifi cantly (microsolenids can tolerate “pebbles” (6, Fig. 2.3b). Fragments of exfoliated a certain amount of turbidity). The mound probably cave wall are observed lying perpendicularly to the

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell (1991), Canérot(1996),Bourrouilh(2000) For furtherinformation: mounds orintrabasinalhigh-porosityanomalies. HCs migrateandhow they canconcentrateintomud- mounds karsticcavities isagoodexample ofhow The hydrocarbonfi in theParentis Basin). shows inthe Arzacq Basin,MimizanNorthoilfi the playsof Aquitaine basin(Gaujacqdiapiricoil Clansayesian reefintervals alsorepresentoneof of subsurface analogs(Bonnefondfi the permeability(andthusproductivity) mud-mounds produceddissolutionswhichenhanced Hydrocarbons: black shalesandfracturationofthemound producing aN120°Esubvertical schistosityinthe 7. The Pyreneanorogeny foldedthewholearea, hydrothermal origin. between exfoliated wall fragmentsmayalsobeof basal clasts. White calciticcementsfi Cezy unconformity andstratigraphy ofthe Stop 2.4: Pal= Paleozoic, T=Triassic, C=Cenomanian,T=Turonian, Co=Coniacian,Sa=Santonian Figure 2.4a-Southverging ThrustsandFolds ofLesEauxChaudesandpanoramaCézy. the Aptian karststhataffect the lling oftheBoisduBagermud- CanérotandLenoble lling thepores ed. The eld). eld (fi observe theCezyUpperCretaceousunconformity North PyreneanFault, wewillStoponD934to so calledforitswarm thermalwaters relatedtothe Access: thrusts nearLesEauxChaudes. The roadwillcrossintheforestseveral south-verging with itscharacteristicU-shapedprofi the baseofglacierisclearlyobservable above, Devonian limestonesinadeepcanyon; meanwhile sub-glacier valley oftheOssauriver, whichcutsthe it ispossibletoobserve, ontherightside,deep road begins toturnleft,andbeforeenteringatunnel, scenic view shows theice-ageOssau Valley. When the metamorphosed Devonian limestones;totheright,a Bonnes and Aubisque pass,totheleftroadcuts plate. Passing thecrossroadwithD918toLesEaux Paleozoic basementofthehighchainandIberian at Laruns,wenow drive alongD934throughthe Introduction: 2.4a and2.4b). des cañons”or“calcaires desEauxChaudes”(fi Iberian UpperCretaceous limestonesor“calcaires gure 2.4a). crossing the village of “ Les Eaux-Chaudes ”, Les Eaux-Chaudes crossingthevillageof“ crossingtheNorthPyreneanFault le. 27-05-2004, 8:41:19 g. g.

WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16 Volume n° 2 - from B16 to B33 n° 2 - from Volume Figure 2.4b - Stratigraphy and geodynamic interpretation of the Iberian margin and of the “ Canyon Limestones ” or “Calcaires des Eaux Chaudes”, at locus typicus. A, B = location and structural sketch ; C= Iberian Margin evolution ; D= Cenomanian ; E= Turonian ; F= Coniacian. From R. Bourrouilh and M. Alhamawi, 1993.

Structural landscape (fi gure 2.4a): the High Chain is the panorama, we see the granites, abruptly eroded there composed by a huge Paleozoic series, intruded and overlain by the transgressive Cenomanian by the Variscan granites of Les Eaux-Chaudes, which shallow water limestones, followed by Turonian and metamorphosed the surrounding rocks. Observing Santonian (yellow) limestones. This autochthonous

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell and Alhamawi (1993). and Alhamawi For furtherinformation: (Bourrouilh and Alhamawi, 1985). Campanian announcingcompressioninthe West fl sunk westwards. As aconsequence,deepcalcareous developed whiletheIberianplatedifferentially Pyrenean andNorth-Pyreneanforedeepbasins progressed duringtheLateCretaceous,South compression betweenIberianandEuropeanplates Alhamawi, 1985).However, asthetectonic features fromhurricanetrails(Bourrouilhand or “ limestone ofthecañons ” exibits sedimentation and, like intheBahamas,EauxChaudeslimestone environment quitesimilartothemodernBahamas occurred inashallow sea(fi Sedimentation oftheUpperCretaceouslimestone basin whichdeveloped north,alongaN110°axis. margin?) North-Pyrenean ofthedeep (-3,000mdeep limestones, theIberiannorthernmargin was alsothe deposition oftheseUpperCretaceousshallow water resting above theEaux-Chaudes granites. Duringthe erosional continentalsurface oftheIberianplateor Cenomanian toSantonian,sealingthepre-Cenomanian deposited directlyontheIberianplatebasement,from latitude. UpperCretaceousshallow water limestones located southofitsactualposition,inanintertropical transgression. Inthisperiod,theIberianplatewas the Cenomanian,seacameagain inageneral from herewestwards totheBayofBiscay. During deposited onthenorthernmargin oftheIberianplate, the Mendibelzaconglomerates.Suchfanglomerates fl by fl basement was eroded.Hugeerosionaccompanied such astheCezyMountain,emerged Iberian area uptotheCenomanian(-96Ma).Inlarge areas Biscay, theIberianplateremainedemerged inthis broke upinresponsetotheopeningofBay Interpretation: just above theparkingarea. Paleozoic basementformthepicdeGoupey (2,209m) fl again over theunderlyingthrust,forminganinverted series, stillrestingonevaporitic Triassic, isthrusted Cretaceous limestones. A secondUpperCretaceous base, followed upwards byathickseriesofUpper composed byaslabofevaporitic Triassic atthe Upper Cretaceousseriesisoverlain byathrust, ysch facies appearhereduringtheLateSantonian- uvial anddeltaicconglomerates(1kmthick) called ank ofasouth-verging recumbentfold. The inverted uvial transportationledtodepositionofthick whentheJurassic Aquitaine platform Ternet (1965),Bourrouilh gure 2.4b),inan glacier, now occupiedby theFabrèges reservoir. glacial morphology, createdbytheQuaternary Ossau The highpartoftheOssau Valley clearlyshows a et al the ChainproducedPicduMidid’Ossau(F. Bixel south; post-glacialerosionaswellrecentupliftingof the calderaandofringdyke werethrustedtothe then, duringthePyreneanorogeny, thenorthernhalfof the calderawas truncatedbyUpper Variscan faults and of anUpperCarboniferous-Permianvolcano. Later, surrounding alarge caldera (about 7kmindiameter) the landscapeto West, isconstitutedbyaringdyke peak ofPicduMidid’Ossau(2,884m),springingout in thispanoramatothesouth(Fig.2.5a),highest Stop 2-5a: of aPaleozoic crest. Artouste skiresort. A shortwalk willbringustothetop we willtake thetelepherique(cable-car)upto Access cover south-verging thrusts. Pyrenean basin,andaseriesofsuccessive basement+ tectonic inversion ofthenorthernmargin oftheSouth compression migratedwestwards andprovoked the was overlain bydeepwater fl the shallow water limestonefacies deepenedand Senonian: thefutureHighChaindownwarped, An incipientcompressionbegan hereduringthe continued duringamajorpartoftheLateCretaceous. shallow marinelimestonesandthissedimentation basement theC then intrudedbygranites.Directlyonthiscontinental plate was foldedduringthe Variscan orogeny and Introduction: Les Eaux-Chaudes:fi Artouste: theSouth-verging Folds and Thrusts of Stop 2.5: 1993. Alhamawi, 1985,R.Bourrouilh andM. Alhamawi, 1985, EauxChaudesmassif: Y. Ternet, 1965, M. For futherinformation: overturned fold(Ternet, 1965, Alhamawi, 1985). south-verging thrustsheetofGourzy, whichisan north, thisthrustsheetisalsooverlain byanother verging thrustsheetofLes Arcizettes. Furthertothe unconformably andareoverlain bythelarge south- granites, theUpperCretaceouslimestonesrest of theHighChain(right),intrudedbyUpper Variscan see frontcover, fi northward panoramaontheEauxChaudesmassif: crossing thecrest,wenow godownhill andhave a Stop 2-5b: ., 1985). : fromthebankofFabrèges damreservoir thePaleozoic basementoftheIberian enomanian transgressive seadeposited gure 1:over thePaleozoic basement gure 1.5andPlate1,fi Ossaupeak:F. Bixel yc fce. Tectonic facies. ysch 27-05-2004, 8:41:24 g.1 et al

., WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Figure 2.5a - Southverging Thrusting of the Late Paleozoic Ring Dyke of the caldeira of the Pic du Midi d’Ossau.

Stop 2.6: Valley in the North Pyrenean Zone. It is the domain the Benou Plateau : thrusts and folds in the Ossau of the Béarn Ranges dominated by E-W structures Valley: fi gure 2.6a and 2.6b. (Mailh Arrouy, Barescou syncline, Moulle de Jaout This Stop represents a panoramic view of the Ossau anticline …). Nevertheless, the Ossau Valley marks the occurrence of transverse structures (lateral ramp), Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 2.6a - The Benou Plateau : thrusts and folds in the Ossau Valley.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell entire groupisthrusttothenorthwestover thefolded cover ofthePaleozoic sheetofGère-Bélesten. The of PladouSoum. The latterconstitutethedetached complex canbe foundinthefi towards thenorth. The extension ofthefoldedJaout the crestofIzeste Woods. The twistedseriesdips To theeast,Rey Mountainseriesoutcropagain on horses mixed with Paleozoic horses. fault). This fault zone consistsof Triassic ophite against thePortdeBéon Aptian units(PortdeCastet the south,inRey Mountain. This seriesisfaulted monocline series(Liasto Albian) dipping70°towards the PènedeBéonfaulted anticline)andthereverse Jaout Albian-Aptian foldedseries(Jaoutsyncline, Finally, Béon Triassic stripandintheLouviepass. west, whichissubvertical andoutcrops inthe Aste- The NorthPyreneanFault (NPF), especially, seeStop2.5b). of the“EauxChaudes”recumbentfolds(PicdeGer, Upper Cretaceouscover deformedin thecomplex The PyreneanHighChain, from southtonorth(Fig.2.6aand2.6b): the southernslopeofvalley shows thefollowing, plateau ontheBenoulateralmoraine. The view of middle Ossau Valley canbeobserved herefromthe Structural landscape: high-voltage electricpost. up tothevulturefeedinggrounds.Park aroundthe plateau above . Take thetrailthatheadsnorth, Access related toinheritedCretaceousnormalfaults. (Lenoble andCanérot,1992). Figure 2.6b-Structuralcross-sectionoftheN-PyreneanZoneinBiellearea,Ossau Valley, : headtowards theeasternendofBenou the NorthPyreneanZone, theglacialtopographyof withitsunconformable ve imbricateslices detailedbythe strikingeast- Casteras, 1974;Henry, 1987. For furtherinformation: (transpression). subsequent development ofcompressionalstructures Mesozoic paleogeographicstructuresinthe that isplayedbyextension-related (transtension) ridge). This againdemonstratesthefundamentalrole running alongtheHauteSoulefi Albian Ossaufault andtheIbechfault (a W-E fault located exactly attheintersectionofthatN30° breccias) tothesouthofLassourdebasin,is generation ridge),marked bybrecciainfi demonstrated thatthePicdeLauriollediapir(second Ossau Horst.LenobleandCanérot(1992)have also Albian. That fault borderedthewesternedgeof during theLiassic,EarlyKimmeridgianand fault re-usedanancientN30°normalfault, active strike-slip component.Ithasbeenestablishedthatthe Mailh Arrouy). Itslateactivity hasa W-E right-lateral south-verging Benouthrustfront(andthatofthe Interpretation: thrust, strikes N30°E(LenobleandCanérot,1992). The fl WE, sub-vertical structuresofBergoueits Woods. Marie Blanquepass.Park near thebridgewhich Barescou Valley totheOssau Valley through the Access: fi syncline (Jurassic reservoir andsource rocks) : Mailh Arrouy viewfrom Barescou Stop 2.7: gure 2.7aand2.7b. exured thrustfault, calledtheOssautransverse atEscot,take theroadthatleadsalong theOssauthrustclearlycuts LenobleandCanérot,1992; rst generationdiapir ll (collapse ll 27-05-2004, 8:41:30 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16 Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 2.7a and b - Sequence Stratigraphy of the Middle Jurassic of the Mailh Arrouy (Total).

crosses over the Barescou stream. evaporites and shales onto the Albian fl ysch of the Structural landscape: The topography of the Mail Barescou syncline (Fig. 2.7a and 2.7b). This series Arrouy reveals good outcrops of the Jurassic series shows, from base to top, the Lower and Middle that are thrusted southwards with a sole of Triassic Liassic limestones, the Upper Liassic marls, the

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell For furtherinformation: structure oftheMeillongasfi the southernedgeofblock)isalsosimilarto The geometryofthemonocline(andparticularly (Comminges basin–SaintMarcelfi in the Aquitaine basin,especiallyintheeasternsector The Liassicmarlsconstituteoneofthesourcerocks compared tothedolomiticlevels oftheMeillonfi constitute goodhydrocarbonreservoirs. They canbe thick andporous(especiallytheooliticshoals), Hydrocarbons: system tractinS6(pinnacleoftheMailh Arrouy). and S6).Notetherapiddevelopment ofthehighstand black dolomiteswerecutintotwo completeseries(S5 fl separating thelimestonecliffs comprisethemaximum series (transgressive systemtract). The grassyslopes lowstand systemtract)andthenafi upward series(highstandsystemtract,followed by Each sequencelimitbegins withacoarsening sequence limitsinthegrey scarpsofthelandscape. and S4,shown onFig. 16 aandb).Observe the were divided into3 third-order sequences(S2,S3 Sequence stratigraphy: base ofthe Triassic. of theLower Liassiclimestones,andlaterallyatthe The thrustfault dips20°to30°northward, atthebase of recrystallizedooliticshoalsandlagoonalfacies. dolomites calledthe“Mailh Arrouy dolomites”made grey “fi fi Herrere :Pillow-lavas ofthe Albian riftstage: Stop 2.8: intercalated betweenthetubes. larger roundtipstothesouthwest.Smallerpillows are volcanic lava tubesdip20-30tothesouthandendin in thesubsurface tothewest.Heresubmarine exposed afew kmtothewest,andthatareprevalent and teschenites(under-saturated syenites)thatare mesovolcanic magmaticrocksinclude episyenites other partsoftheOgeuBasin. The epivolcanic to basaltic columnsandpyroclastic breccias,visiblein part ofasuitevolcanic textures alsodisplaying within the Albian blackmarls(Fig.2.8). They are Stratigraphy : to theleftoffarm gate. cliff besidethecorncrib. A pedestrian pathislocated railroad crossing.Pillow-lava fl Arudy), parkattheCourrèges Farm just northofthe Access: ooding surfaces ofthesequences. The overlying gure 2.8 lament limestones” ofthe Aalenian, lower southofHerrère(D920)betweenOloronand (Moen-Maurel thepillow-lava fl theMailh Arrouy dolomitesare theBathonianlimestones Henry, 1987. et al eld. ., 1996). ows arelocatedinthe ows areinterbedded eld). nn upward ning eld. down tothebasement,orlikely beneath thethrust that arelocatedover thePyreneanaxialzone(eroded controlled bydiamond-shapedfault patterns.Riftaxes limited tohalf-grabensen-echelonbasins,andbasins separation. IntheNorth-Pyreneandomainriftwas sign ofoceaniccrustdevelopment, norofmargin between IberiaandEurope.However thereisno magmatic expression of themid-Cretaceousrifting the outcrop. Volcanics andepisyenitesrepresentthe that favoured theupliftwas locatedtothenorthof tubes indicatesthatthenormal(extensional) fault Tectonic signifi fi the Aquitaine a kmthick,andthusprovide thebestsealover mostof as sourcerockandseal. The Albian marls can beover that wereaffected bymagmatism. These marlsacted sills. The sourcerockswerethe Albian blackmarls reservoir consistedofchilledmargins ofepisyenite which producedgas(Moen-Maurel frequency markers thatweredrilledatLedeuixand see at-1200m/SSasimilarantiformmadeoflow the Gave d’Oloron Thrust. Inthe3Dseismic,onecan axis oftheanticlineplungesgentlytowestbeneath metres tothenorthofpillow-lava outcrop. The Anticline whoseN110axisislocatedafew hundred of thetubeswas acquiredduringfoldingoftheBelair Structural settingandhydrocarbons: Figure 2.8-Pillow-lavas fl elds (Lacq,Meillon...). cance: Herrer (20cmlongpencilfor scale). thesouthward fl ows of the Albian riftstageat et al partofthedip ., 1996). The ow ofthe 27-05-2004, 8:41:36 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

sheets, such as for the North-Pyrenean Fault) would Stop 3.2: be better candidates for the hundred-km long, left- roadcut - Jurassic dolomites lateral strike-slip displacement that occurred between (reservoir formation). Iberia and Europe through the Mid-Cretaceous. Access: again driving south on the N 134 the Stop concerns the road-cut, three kilometres north of DAY 3 Sarrance. Park at the picnic grounds. Park on the side from Oloron Ste Marie to Saint Jean Pied de Port of the road-cut, please, put on the warning lights. Sequence stratigraphy: the road cuts across the Leaving Oloron by the southern road N 134 to Col du Jurassic rocks of the sub-vertical northern limb of and the Spanish border, we enter the Aspe the Sarrance anticline (fi g. 3.1c). The road-cut reveals Valley, along which runs the Gave (river) d’Aspe. some sedimentary key points which have given rise Along the valley, there also exists a railway linking to a proposed sequence stratigraphy (Canérot et Oloron and the Spanish railway station of Canfranc. al., 1990) for the North Pyrenees dolomite series. This railway was cut a long time ago and discussions This study concerns the stratigraphic interval from between Spain and France are still taking place, to the Bathonian to the Upper Callovian in the Bearn restore it and the railway link. Entering the valley and Ranges. The set was divided into fi ve third-order the mountain, railway bridges, tunnels are visible on sequences, termed DSI to DSV (Lenoble, 1992). Only both sides of the N 134. part of sequences DS III to DS V can be observed here (Fig. 3.2). Stop 3.1: Sequence DS III (30 m): fi nely bedded dolomites Pont d’Escot - Ste Suzanne Formation (seal) : (outer shelf), grading into oolitic (offshore bars) and fi gure 3.1a, 3.1b, 3.1c fi nally reef deposits (colonial corals, fi g 3.2b). The Access: 15 km south of Oloron, on the N 134, we will series in this fi rst unit represents the highstand Stop in the parking lot, just after passing one of these system tract. The contact with sequence DS IV is not railway bridges, the Pont d’Escot. distinct. Stratigraphy, structural geology: from south to north, Sequence DS IV (40 m): bioclastic dolomites, thick the road cut reveals the Aptian sedimentary evolution and then fi nely bedded (offshore bars), characterizing of the Sarrance anticline’s sub-vertical northern the lowstand system tract. They are overlain by limb. The rapid transition from Bedoulian Ste- a striking ferruginous discontinuity, overlain by Suzanne marls, to Gargasian (Urgonian) limestones bioclastic horizon, interpreted as a transgressive (with Toucasia) is nevertheless progressive within surface. The oolitic bars (shoreface) and the overlying a highstand environment. Further up-section, the striped dolomites (inner lagoon) probably correspond Urgonian facies is prevalent within the lowstand to a highstand system tract. The maximum fl ooding of the next sequence (Fig. 3.1). The sequence limit surface has not been identifi ed. probably corresponds to a sedimentary hiatus, which Sequence DS V (15 m): thick dolomites (shoreface can be observed at the base of the thick beds with bars) overlain by striped dolomites (inner lagoon) abundant Rudistids. The schistosity is particularly correspond to lowstand and highstand system tract, well marked within the marly beds. Further south, and respectively. The transgressive interval and the upslope, the marls are interbedded with limestones, maximum fl ooding surface have not been clearly indicating that the marly series comprises two distinct observed. groups (Fig. 3.1b). This intermediate limestone and Because of intense fracturing, it was not possible dolostone is a regional seismic marker in the foothills to make a precise reconstitution of the described and foreland sub-surface. sequence. Stratigraphic determinations (Bathonian Volume n° 2 - from B16 to B33 n° 2 - from Volume Hydrocarbons: the Sainte Suzanne marl formation for DS III, Callovian for DS IV and DS V) are forms the upper or direct seal of many hydrocarbon based on the correlation scheme between the Béarn fi elds in Aquitaine (Vic-Bilh, Pecorade, Lacq), and dolomite series and the Basque series with abundant Meillon gas fi eld, located 30 km SE. Ammonites, which was not subjected to epigenetic For further information: Canérot, 1964; Castéras, processes. 1974. Hydrocarbons: the dolomite complex represented in the area was designated as the Mailh Arrouy formation, and considered as the equivalent of the

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell the Mailh Arrouy sequence). Kimmeridgian) thantheSarrancesequence(or probably muchyounger(UpperOxfordiantoLower research hasrevealed thattheMeillonformationis Meillon gas-bearingdolomiticformation.Further Figure 3.1a-Pont d’Escot:SainteSuzanne Aptian formation SequenceStratigraphy. Lenoble, 1992. For furtherinformation :thesouthern margin of Stop 3.3: : Canérot et al ., 1990; 27-05-2004, 8:41:40 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

(Fig. 3.3). In the Bedous Valley, the Triassic includes Muschelkalk limestones, Keuper shales and ophites in the slivers of duplexes that were thrust to the south (visible along the halpin road). These rocks were thrust onto the fl ysch of the Upper Cretaceous cover in the High North- Range, around the village of Lées (Fig. 3.3). Further north, the crest of the Layens Mtn shows a thick Pyrenean sub-horizontal Jurassic and Lower Cretaceous series rift: fi gure belonging to the normal limb of a recumbent anticline 3.3. verging to the north. To the east of the viewpoint the Access: N 134 Bergon Mtn shows a hanging recumbent syncline to village. with a top-to-the-north vergence. Entering Accous, Geodynamic interpretation: the Bedous area take the asphalt road marks the mid-point of the double vergence that to the east along a 3 km hairpin loop that leads to the viewpoint over Bedous Figure 3.2b - Colonial corals in Sequence DIII. and Stop there; a one mn walk to the hilltop to the west leads you to an excellent structural viewpoint. Structural landscape: the landscape shows the relation between the northern Pyrenean range, to the north, and the High Range, to the south, on the upstream side of the Aspe Valley

Figure 3.2a - Middle Jurassic Sequence Stratigraphy (Bathonian-Callovian), Northern side of Sarrance anticline, (Canérot and Lenoble, 1993). Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 3.3 - Structure of the High Range at Bedous, Aspe Valley, (Total). Fl= Upper Cretaceous Navarella fl ysch (Senonian), UK= Upper Cretaceous Canyon Limestones (Cenomanian- Lower Senonian), Tr= Triassic ophites.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell Figure 3.4b-Thefolded Megaturbiditeinthelandscape. Figure 3.4a-MegaturbiditeatOsquich Pass. 27-05-2004, 8:41:48 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

characterizes the Pyrenean mountain range. Some to l’Hôpital St Blaise and Mauléon-Licharre and then authors traditionally set the North-Pyrenean Fault the D 918 to Col d’Osquich. at this location but this hundred-km long strike-slip The Stop is located on the road from Mauléon to fault is likely concealed beneath the south-verging Larceveau, D 918, about 1km after the Osquich pass, thrust sheets, and would occur further north in depth, at the fi rst curves in the road, just before the village of probably where some earthquakes still originate St Jean Ibarre. nowadays. The Megaturbidite concept was fi rst established To the South, subduction of Iberia beneath Europe by Soler and Puigdefàbregas, 1970; Rupke, 1976, was so large in magnitude that only south-verging for huge gravity deposits occurring among Eocene thrusts and nappes can be observed. To the north, deposits of the Southern Pyrenean basin. Later, depending on the original dip of the rift faults, Johnson and al (1981) studied the South-Pyrenean inversion produced either north-verging or south- basin and Labaume et al. (1983) studied these verging folds. The rift structures are located in a retro- deposits in detail. Megaturbidites were later identifi ed arc setting, which limited its inversion and its uplift among the Cretaceous North Pyrenean sediments and (and erosion), thus permitting the petroleum system were studied in detail by Bourrouilh, Coumes and to exist till today. Offroy (1984) and Offroy (1984) who interpreted the infi lling of the North-Pyrenean cretaceous fl ysch Stop 3.4: basin, demonstrating that: Osquich Pass: Upper Cretaceous Megaturbidites: - two large megaturbidites occurred in the basin. One fi gure 3.4a, 3.4b, 3.4c and 3.4d. of them extends over more than 90 km, and varies Access: from Stop 3.3, drive back to Accous and from 60m in thickness, near Pau, to 20m in its western now drive N 134 back to Oloron. At the entrance to part, near the Atlantic Ocean. Oloron, drive on D 936 to and Sauveterre - Megaturbidites originate as evolutionary mass-fl ow- de Béarn. 11 km from Oloron, take on the left the D 25 megaturbidites (fi gure 3.4d) Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 3.4c - Sedimentological interpretation of the Megaturbidite, from Offroy, 1984.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell the Iberianmargin :(fi Ahusquy Pass: Structure ofthetiltedblocksand Stop 3.5: in interval surfaces (fi kinetic energy. Vibratory ripplescanbealsoobserved was internallystratifi intervals, whichdemonstratethattheturbiditicfl constituted bysuccessive but amalgamatedBouma’s (1983), Offroy (1984),thismegaturbidite is Interpretation: of theroad. of theroad,but also inthelandscape,onleftside turbidite, 40mthick,whichoutcropsontherightside Structural landscape: Introduction: We drive backtoMauléonby theD918road. and Offroy (1984),Offroy (1984),. Bourrouilh andOffroy, 1983,Bourrouilh,Coumes For furtherinformation: (fi affecting thefl enough, wecanobserve large Pyreneankink-folds On theleftsideofroad,andiflightisoblique gure 3.4b). Figure 3.4d-TheEvolutionnary-Mass-Flow-Megaturbidite concept,R.Bourrouilhetal.,1984,Bourrouilh,1987. ysch andparticularlytheMegaturbidite fromMauléontothesmallvillage studiedbyBourrouilhandOffroy ed, eachstratahaving aspecifi gure 3.4c). thepanoramashows amassive gure 3.5). Figure 3.5-Panorama from Ahusquy Pass. ow ow c The Arbailles anticlineisfollowed tothesouthbya frame ofthetiltedblockor“ Arbailles ”block. deposited. These competentlimestonesformthe marine partlyreefal limestonesoftheUrgonian were of “themarnesdeSteSuzanne”. Then, theshallow fi Hauterivian-Barremian shallow water limestonesand fan-like dipsoftheNeocomiancontinentalsands, tilted blockisdemonstratedbytheunconformable bauxitic remnants. The progressive rotationofthe the UpperJurassiclimestone,locallyshowing is clearlyregistered intheerosionalsurface affecting rift whichextended theBayofBiscay. This history southern margin ofthe N-PyreneanLower Cretaceous dolomitic Jurassic. The tiltedblockwas partofthe typical Germantype Triassic, followed byacalcareo- Upper Carboniferous,unconformablyoverlain bya N110°E anticlineshows acompleteseries,fromthe deformed inaNEverging thrustedanticline. This margin (Arbaillesblock),whosenorthernedgeis deformed tiltedMesozoicblockoftheIberian to the Ahusquy pass,theroadwillcrossalittle- fl of , theroadcutsUpperCretaceous nally bythefi ysch oftheN-Pyreneantrough.From Aussurucq rst large transgressive marinedeposits 27-05-2004, 8:41:55 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

large syncline, formed by the Upper Aptian-Albian of us, at the Pic d’Orhy, at an elevation of 2,017m. black shales, in what was the downthrown part of the For further information: see the geological map at Arbailles block. 1/50 000 n° XIV-46, Tardets -Sorholus Access: on the way to Mauléon by road D 918, we will take the small road D 147 on the left to Mendy Stop 3.6: and to Aussurucq and then through the Forêt des Lutogagné: Structure of the Lower Cretaceous Arbailles massif, up to the Ahusquy pass. tilted blocks: fi gure 3.6. Structural landscape and Interpretation: Ahusquy Introduction: this is a general panorama along the pass is situated on the Upper Aptian-Albian black strike of the southern fl ank of the Arbailles, or the shales, which form the core of the Apanicé-Bois de Apanicé-Bois de Zouhoure syncline. Zouhoure syncline. Access: leaving the Ahusquy pass, we drive to the The southern fl ank of this syncline is verticalized. Iraty pass and we will progressively cross the Albian The underlying Urgonian limestones, which form the black shales of the syncline to reach the Triassic frame of the Arbailles anticline to the north, crops out outcrops and the panorama. here again, forming a continuous rocky ridge, reaching Structural landscape: we Stop near the Cayolar an elevation of 1,265 m at the Pic de Behorleguy. (mountain barn) of . Looking to the north, The Jurassic and the evaporitic Triassic outcrop on we now examine the southern limb of the Arbailles the southern side of the syncline, in a narrow ridge syncline culminating locally in front of us at the separating it from the Mendibelza conglomerates; Lutogagné peak (1,097m). This southern fl ank is this N 110°E zone is generally interpreted as a major rotated vertically with the folding of the syncline, and Pyrenean Fault, extending to the West Souquet’s deeply fractured in this area. “Faille de Bigorre” (Souquet et Debroas, 1980). Interpretation: according to Canérot and Lenoble However, this hypothesis does not fi t with structural (1991), the Jurassic (Lower Lias to Bajocian) and drill-hole data and could be discussed during is covered by diapiric breccias ( the fi eld trip. Immediately south of this fault zone, collapse breccias) of Lower Cretaceous age, the thick black Albian-Vraconian conglomerates of and unconformably overlain by an uppermost the Mendibelza (this name means: black mountain Gargasian-Clansayesian limestone containing typical in Basque) range are directly discordant on the Foraminifera. (Peybernès and Garot, 1984). Therefore Paleozoics. In the background of the panorama, the most of the Jurassic and Barremian carbonates are Upper Cretaceous “calcaires des cañons” or “calcaires absent; a reconstruction with subcrop maps indicates des Eaux Chaudes” present a sheared unconformable the presence in the Barremian to Albian of a diapiric contact with the Paleozoics of the High Chain (see ridge which developed along the downfaulted side of Stop 2.4a and 2.4b, here above), which culminates at the Arhansus Fault. This ridge was then squashed by the Pic d’Anie (2,504 m high, to the left) and in front the subsequent compression between the upthrown Figure 3.6 - Lower Cretaceous tilted blocks. Volume n° 2 - from B16 to B33 n° 2 - from Volume

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Volume n° 2 - from B16 to B33 B16 - B16 Figure 3.7a-GeneralviewoftheMendibelzamassif. Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell Canérot andLenoble,1991 For furtherinformation: productive (Gaujacq). have beendrilled,andarelocallyHCbearing Tarbes basins,whereitcontainsreefstructureswhich sequence hasbeenobserved inthe Arzacq and platform (Aptian)tothe Albian marlbasin. This marks thevertical transitionfromtheUrgonian Hydrocarbons: downfaulted half-grabenofthe Arbailles Block. rift andthe Albian synclinewhichoccupiedthe block oftheIberianmargin oftheNorth-Pyrenean Mendibelza massfl Stop 3.7: result fromtheerosionofIberianplate. They Paleozoics, theMendibelza Albian conglomerates Introduction: fi Figure 3.7b-SedimentologyofMendibelzaconglomerates (Total). gure 3.7. directlyrestingunconformablyonthe theClansayesianseriesregionally ow conglomerates: Peybernès andGarot,1984, Structural landscape: Access: growing divergent Iberianmargin. and slopefanglomerates, rapidlyslurrieddown onthe They areathickaccumulationoffl passage betweentheriftandearlyplatedriftstage. eastwards. Thus, these fanglomerates markthe opening oftheBayBiscayrapidlyprogressed margin upliftoftheNorthIberianmargin, asthe conglomerates areinterpretedasresultingfrom grew upalongthecoastanddeltabayous. The branches anddebris,ofthecoeval forestswhich also containlayerswithremnantsofleaves, broken water andreefal limestonesandblackshales. They subcontemporaneous Lower Cretaceousshallow Jurassic limestones(Digbehi,1987),aswell evaporites (bipyramidal quartz), Triassic ophites, Ordovician tothePermian,andalso, Triassic rework allthePaleozoic series,fromatleastthe ontheroadtoIratypass Interpretation: are observable, topontheleft. Digbehi, 1987;Miranda Avilès, 2002. Bourrouilh, CoumesandOffroy, 1984; For furtherinformation: fl isolated pebblesoutcroppingonthesea the formerdepositedsequences,leaving water current,whichtookoff apartof abruptly washed outbyahighenergy the topofmass-fl fl mass-fl emplaced byimmature,i.e.proximal fi road, Mendibelza conglomeratesonIraty Stop 3.8: onroadD18,leaving the Access: Triassic ophitesandbipyramidal quartz. muscovite-rich greywackes, aswell limestones, carboniferousradiolaritesand quartz, Ordovician quartzites,Devonian reworking pebblesandgravels of including reefal limestones,and Cretaceous shallow water limestones, olistolithes ofPaleozoic blocks,Lower to observe large olistostromes,with Introduction: Saint Sauveur Chapel ontheright, oor. uvial (deltaic)overfl gure 3.8 ows, probablyresultingfrom down Iratypass,driving to . several mass-fl thisStopallows us theseslurriedbedswere ow sequencesis od. Frequently, oods. uvial tocanyon Boirie,1981, o sequences ow 27-05-2004, 8:42:01 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Figure 3.8 - Olistostromes and olistolithes in Mendibelza conglomerates.

Stop begins about 1 km down from the Chapel Lecumberry, on the small slope of the road. crossroad, on the fi rst road curve (Fig. 3.8). Structural landscape and Interpretation: Structural landscape: the large olistostrome crops 1. The post-rifting, syn-drifting “ European ” plate out all along the right side of the road, over several is represented here by the western structure of the tens of metres, gently resting on channelized mass- Arbailles tilted-block, showing the southern limb of fl ow. Large pebbles and Paleozoic and Lower the Arbailles (Apanicé) syncline, culminating here at Cretaceous calcareous fossiliferous olistolithes are Behorleguy peak (1,265 m). clearly observable on the side of the road. The Urgonian ridge of the Behorleguy peak is The other side of the road shows the Mendibelza verticalized. The shallow water Urgonian carbonates massif and, far in the background the Atlantic coast rest unconformably on bauxitic deposits fi lling up and the Bay of Biscay. a previous karst and were mined. This diachronous Interpretation: the on-going growth of transtensional bauxite extends unevenly from here to Provence, over basins provoked inversion of the morphology of their 800 km away, testifying to complex and polyphased southern margin, revealed both by the infi lling of the emersions/submersions of the “Durancian isthmus”. basins by large amounts of fl uvial conglomerates The slope down the Behorleguy peak is formed by an (Mendibelza ones) and by large olistostromes, incomplete Jurassic series, the pre-Urgonian erosion reworking olistolithes of former deposits but also of reaching irregularly the Callovo-Oxfordian, the the subcontemporaneous reefal carbonates (Boirie, Dogger or even the Liassic. 1981, Souquet and Boirie, 1985, Digbehi, 1987). The Lecumberry valley strikes through the soft These transtensional basins are similar to the modern evaporitic to calcareous, and arenitic Triassic. Baja Californian divergent basins of the Gulf of The possible fault previously discussed at Lutogagné, California (Miranda Avilès, 2002). must run on the right side of the valley For further information: Boirie, 1981, Souquet et 2. the Iberian plate is constituted here by the Boirie, 1985, Digbehi, 1987, Miranda Avilès, 2002. large amount of Albian to Vraconian Mendibelza Volume n° 2 - from B16 to B33 n° 2 - from Volume conglomerates, unconformably resting on the Stop 3.9: Paleozoics. Far in the background, the Mendibelza tilted blocks and European-Iberian margin, 2 km conglomerates are locally covered by the Upper NW of Lecumberry : fi gure 3.9. Cretaceous “calcaires des Cañons”. Introduction : this Stop allows us to observe the For further information: see the geological map at Arbailles tilted block and the European-Iberian 1/50 000, n° XIII-46, St Jean Pied de Port. margin. Access: on road D 18, about 2 km NW from

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell Access: Lutetian progressively appears. Then, acarbonatefl develop fromCenomaniantoLower Campanian. ” or“canyonThese “calcairesdescañons limestones” forming thehighpeaksofEauxChaudesMassif. these limestonesthefi the PyreneanHighChain. We alreadyobserved shallow water carbonatesformthemainframeof conglomerates, ahugeseriesofUpperCretaceous Introduction : Fold structures Pic d’Orhy South-verging Thrust and Stop 4.1a: Morning: us throughtheMendibelzaconglomerates. The roadtoLarrauandthePortdewilldrive from StJean PieddePort toJaca fromLarrau,roadD26climbsuptothePort restingontheMendibelza ysch facies uptotheLower DAY 4 DAY 4 rst day, in theOssau Valley, Figure 3.9-Tilted blocks andEuropean-Iberian margin. Eocene fl overturned syncline,formedbythe Paleocene-Lower Cretaceous fl a souththrustedanticline,involving theUpper verging foldsoftheOrhypeak,2,017mhigh,forming westwards wecanobserve theS-shapedsouth- Structural landscapeandinterpretation: elevation, nearthethrustsurface (fi de Larrau,1,575mhigh. We willStopat1,400m 1/50 000,n°XIV-47, Larrau. For furtherinformation: tectonic units. Here wecanseeoneofthehighestfold-and-thrust Structural landscapeandInterpretation: the Iberianplateinfrontofus. just below OrhyPeakand with theamplepanoramaof We arenow intheheart ofthePyreneanHighChain, m high. Access: Port deLarrau:StructuralPanorama Stop 4.1b: drive onD26uptothe PortdeLarrau,1,573 ysch (fi ysch, followed byansouth-verging g.4.1a2). seethegeologicalmapat g.4.1a1). theHigh 27-05-2004, 8:42:06 looking WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Figure 4.1a1 - Geological map of the Pic d’Orhy area, from BRGM Map, n° XIV-47, Larrau.

Chain now develops west and eastwards, the Upper This fl ysch joins the unconformable cover overlying Cretaceous to Lower Eocene “Calcaires des Cañons” the Paleozoic basement, in the High Range further to forming the mountain range. the south. To the south, the large south Pyrenean basin develops, Flattened and sheared (boudinage-affected) fi lled with Eocene fl ysch of the Hecho Group. Figure 4.1a2 - Aerial view of the Pic d’Orhy, courtesy of Stop 4.2a: Vivien De Feraudy (Total). Igountze Thrust and St-Engrace Thrust sheet. Access: take the D 26 back to Larrau and then along the Gave de Larrau to take road D113 on the right along the northern slope of the Ste-Engrace valley. Stop 500m east of the Kakoueta canyon road access.

Stratigraphy, structural geology: the Igountze unit B16 to B33 n° 2 - from Volume consists of the Devonian – Carboniferous basement and of its unconformable Albian cover comprising the Mendibelza conglomerates. This unit is southward thrusted, almost horizontally, over the Ste Engrace thrust sheet (fi g.4.2a1 and 4.2a2). The latter is also thrusted (fi g.4.2a3) over the so called canyon limestones (Cenomanian to Campanian) and the Navarella fl ysch (Campanian and Maastrichtian).

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Volume n° 2 - from B16 to B33 B16 - B16 High Chain(Total). Figure 4.2a2-Structuralcross-sectionbetween theIgountzeMassifand Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell in theMendibelzaconglomerates The diversity ofthemarinefacies from theHighRangebasement. fault separatedtheIgountzeblock fault. IntheEarlyCretaceousthis ancient north-dippingnormal Igountze Thrust reactivated an Structural interpretation: the mainthrustsheet. which isdisconnectedinfrontof Canyon limestonesandthefl Mendibelza conglomerates,the (Paleozoic covered bythe a klippewithcomplex structure south, Lakoura Peakismadeof limestone-fl duplex shearbelt,locatedatthe characterized byanorth-dipping beneath theIgountzethrustis Laterally theinternalshearingofSenonianseries sedimentary brecciasoccuratthebaseoffl ysch contact. To the ysch) the ysch. Figure 4.2a3-Larrau-LakhouraThrustsheet(Total). map n°XIV-47, Larrau. Saint-Engrâce area,fromBRGM Figure 4.2a1-Geologicalmapofthe to, but younger thantheonein 1981). This organization issimilar drowning tothesouth(Boirie, on atiltedblockwithincreasing these arecanyon-cone deposits towards thesouth),suggestthat deposition, gradualthickening sedimentary organization (onlap and siltstones)aswelltheir the Permian-Triassic sandstones that reworked thebasementand south, andthenpuddingstones Paleozoic fragmentsfromthe (enormous fanglomerates with For furtherinformation: block collapsedintheSenonian, still high)oftheHighRange. The southernmost block(whichwas the basementbelongto conglomerates thatreworked collapsed duringthe Albian. The Pyrenean Iberianmargin that corresponds toaslabofthe The IgountzeBlocktherefore the Arbailles (seeformerStops). (Souquet South, duringtheLateCretaceous sedimentary basintowards the widening ofthePyrenean demonstrating theprogressive et al ., 1985). 27-05-2004, 8:42:13 Ribis, WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

1965; Ducasse and Velasque 1988, Boirie 1981. duplexing contributed to the southward allochthonous transport of the Igountze-Ste-Engrace Thrust and the Stop 4.2b: Lakoura Thrust over a minimum of 7 km. The whole Intra-Senonian duplex underneath the Igountze sheared Navarella fl ysch acts as a detachment thrust and Lakhoura Thrusts. with a thick sole. Access: 500m east of the previous Stop. Park on the south side of the road. II. A transect of the Southern Stratigraphy and structural geology: the Navarella Pyrenees and Jaca basin turbiditic fl ysch (Campanian to Maastrichtian) is by Antonio Teixell mainly composed of alternating marly limestones Departament de Geologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain e-mail : [email protected]

Aim of the fi eld trip The aim of this itinerary is to examine thrust tectonics and interaction with sedimentary systems in the Southern Pyrenees. The Southern Pyrenees consist of south-vergent folds and Figure 4.2b - Larrau-Saint Engrâce-Lakhoura Thrust Sheet. thrusts and contain a very well- preserved record of synorogenic sedimentation. Synorogenic sediments are of uppermost Cretaceous to Lower Miocene age, and constitute the Jaca and Ebro basins (Plate 2, fi g.1). The fi eld itinerary will proceed from north to south from the Axial Zone -a large thrust culmination that forms the orographic axis of the Pyrenees- to the Jaca basin -a Paleogene foredeep now incorporated in the the orogen showing a typical turbidite to molasse succession-, and fi nally to the southern mountain front of the External Sierras –where the Pyrenees Figure 4.2b2 - Intra-formational antiformal duplex overthrust the present foreland of the Ebro basin. Navarella Flysch; St. Engrâce road Synthetic geological descriptions of the transect visited can be found in Teixell (1996, 1998). During the trip we will have the opportunity to study and marly sandstones. The beds are intensely sheared (fi g.4.2b). Intraformational duplexes result from features as 1) detailed kinematics and mechanics of the development of reversed parallel south-verging thrusting, 2) interactions between growing thrust ramps accompanying the motion of the Ste Engrace- faults and folds and proximal alluvial fans, and 3) Igountze Thrust sheet above, as well as that of the episodic evolution and progressive deformation of Larra Thrust further to the south.. At this Stop we can foreland basin deposits. observe an antiformal duplex, with a subhorizontal Volume n° 2 - from B16 to B33 n° 2 - from Volume fl oor shear plane and a roof shear plane folded along a Afternoon: N 120 axis. The sub-NS hinges of gravity slumps are Axial zone and Northern Jaca basin preserved in the internal layers of the duplex. This intense shear deformation occurred for at least Stop 4.3: 7 km southward, along a bedding plane slip zone at Pierre-Saint-Martin. The Larra thrust system. the top of the Canyon Limestones and underneath Access: follow the main road NA 1370 to the SW to the Igountze and Lakhoura Thrusts, to the south of cross the Spain/France border and park some 100 m the modern Kakoueta canyon. The intraformational after the signal, beside a road bend. Structural landscape: the Upper Cretaceous rocks

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell limestone memberandaupper, well-beddedand Cañons, attheboundarybetweenalower massive the LarrathrustislocatedwithinCalcairesdes thrust (Larrathrust)(Fig.4.3a).Inthestudyarea, vergent rampsthatrootinabedding-parallelfl system isathinduplex composedofnumeroussouth- of thisnorthernpartthe Axial Zone. The Larra system, characteristicoftheUpperCretaceousrocks In thisStopwecanobserve detailsoftheLarrathrust Alpine deformationinthisbasementmassif. area provides anuniqueopportunitytoconstrainthe Pyrenean Axial Zone(Plate2,fi have beenerodedaway inmoreeasternpartsofthe visited region liesinthatpost-Hercynian rocks One specialinterestoftheCretaceousrocks Pyrenean thrustloading. can beattributed to fl represent adrowning oftheSantonianplatformthat formations areofCampanian-Maastrichtianage,and visible inthelandscape(Ribis,1965). The latter marine shales,andasandstone/shaleturbiditicunit, the Paleozoic. Overlying thelimestonesareopen Cenomanian toSantonian)thatrestdirectlyon platform limestones(“CalcairesdesCañons”, that formthe Axial Zonecover consistofbasal exure attheinitialstagesof g. 1),andthusthe oor SW (fi orientation ofminorstructuresrangefromN-StoNE- (contraction orshear)thatcanbededucedfromthe to bedding,isalsopresent. Transport directions prior tofolding. An incipientfoliation,oblique indicate anearlyepisodeoflayer-parallel shortening arrays have beentiltedtogetherwithbedding,they arrays ofcalciteveins. As theshorteningaxes ofthe rocks, therearecontractional,conjugate en-echelon foliation coherentwithrampshear. Within thewall is stronglydeformedanddisplaysaninternaloblique surfaces, whichencloseanintervening rockslicethat zone ischaracterizedbytwo mainsubparallelfracture is truncatedinaramp-over-ramp geometry. The fault this stratigraphicunitincontact(Fig.4.3a).Bedding bearing limestonememberandtheshalyupperpartof The thrustramp,bringsthemiddlepartofchert- inferences forthekinematicsofthrustsystem. with asetofassociatedminorstructuresthatprovide parking placeshow agoodoutcropofthrustramp, Back totheroad,cutslocatedjustnorthof imbrications onahillsideinthelandscape. for somemetrestogetapanoramicview ofthrust From theparkingareawecanwalk westwards limestones andtheZurizashales. Teixell chert-bearing limestonemember(Teixell, 1990; presented infi A detailedprofi densely packed stackofbedding-parallelcalciteveins. inspection shows thatitsfoliated aspectisduetoa resembles amyloniticmarble.However, closer band ofstronglyfoliatedrockthat,atfi The Larrathrustappearsinoutcropasameter-thick antiform (Gavarnie thruststage). faulting duringthedevelopment ofthe Axial Zone angles totheN,duepost-thrusttiltingandnormal thrust dipsparalleltofootwall bedding,atgentle plane withoutrepetitionofstratigraphy. The Larra defi Structural landscape: border. outcrops bythesignalpostofSpain/France Access: Larra fl Pierre-Saint-Martin. Fault zonestructure ofthe Stop 4.4: Refugio deBelaguaislocatedsome5kmtotheSW. Zone (Pierre-Saint-Martinarea)(afterTeixell, 1990).The a segmentoftheLarrathrustsysteminnorthern Axial Figure 4.3a-Detailedgeologicalmapandcross-section of nition ofadécollement:bedding-parallelslip g. 4.3b). oor thrust. walk down theroadbacktoroadside et al ., 2000). The rampsabove cutthechert gure 4.4.Bedding-parallelveins are le of the fault zoneatthislocalityis theLarrathrustfi rt sight, rst 27-05-2004, 8:42:19 t the ts WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16 Volume n° 2 - from B16 to B33 n° 2 - from Volume

Figure 4.3b - Outcrop sketch and plots of minor structures of the ramp locality at Pierre-Saint- Martin (stop 4.3) (after Teixell et al., 2000).

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell to beintheorderof5km.Displacementwas mostly of theLarrathrust,whichcanberegionally estimated scale, thesewerenotkey mechanismsinmovement recrystallization areconspicuousatthethinsection during shorttimespans.Even thoughtwinningand could accommodateappreciableincrementsofslip sills”) weresurfaces ofzeroshearstrengththat and fl Being constitutedbyinterfaces betweensolid form ofbedding-parallelextensional fractures. weakening andlocalizedyield. Yield initiallytookthe change withinthelimestonecausedepisodicbrittle channeling. Fluidchannelingataslightlithologic A veins ontheleft(afterTeixell etal.,2000). Orientations areontheright;percentageandfrequencyof and otherminorstructures,asindicatedinthelegend. ‘A’. Otherlettersrefer todifferent setsofveins, stylolites structures areshown. Thrust-parallelveins arelabelled Positions andobserved cross-cuttingrelationsofchief Larra fl the weakening was inducedbystressandfl point ofview, veins arefi almost 100%vein material.Fromamicrostructural fault zonecenter, wheretherockappearsformedby footwall, andtheirfrequency increasestowards the abundant foratleast 3minbothhangingwall and Figure 4.4-Structuralprofi for detachment. Teixell capacity ofthehostrockwerenotprimarycauses Hence rheologicalweaknessandwater-generating within amechanicallystronglimestoneunit. The Larrathrusthasthesingularityofbeinglocated and groupedinsets(Fig.4.4). mesostructures have beencorrelatedacrosstheprofi orientation andrelationshipstooneanother, the folds andminorfaults. Onthebasisofaspect, apart fromtheveins includevein breccias, stylolites, complex assemblageofdiverse mesostructuresthat, present, althoughlessabundant. Infact, thereisa observed. Cross-veins obliqueto beddingarealso twinning andrecrystallization.Nofi crystals withvariable internaldeformationby uid, theopenextensional fractures (“water oor thrustatPierre-Saint-Martin(stop4.3). le ofthefaultzone et al lled withblocky calcite . (2000)proposedthat br hv been have bers uid le (leading todécollementslip). 2) stressreorientationandbedding-parallelshear of 1)bedding-parallelstressandcrackdilation, thrust was achieved byacyclic repetitionofepisodes 2000). Hence,weinferthatmovement ontheLarra by differential elasticcontraction(Teixell a shearstressonthefracture. This mayhave occurred have beensomesortofstressreorientationtoimpart displacement was paralleltobedding,theremust stress inathrustregime, but asmajorfl veins arecompatiblewithsubhorizontalmaximum A remainingproblemliesinthatbedding-parallel signature. accommodated bysliponthewater sills,leaving little numerous limestone-shalerepetitions,andshow system, formedearlier(Teixell, 1990). Thrusts cause the vicinityofRefugiobelongtoLarrathrust thrust faults deformingtheCretaceousformationsin landscape isabroadantiform.Minor, south-directed The large-scale structurethatcanbededucedinthe outcropping alongtheroadtoRefugio. Overlying thelimestones arestronglycleaved shales, close totheRefugiocontainshallow-water forams. in fi Lakora klippe. A cross-sectionoftheareaisshown good overview ofthe Axial Zoneandtheoverlying Structural landscape: hut oftheRefugiodeBelagua(signal). Access: 4.5. of theCretaceous cover ofthe Axial Zone, Refugio deBelagua.Generalviewandstratigraphy Stop 4.5: gure 4.5.UpperCretaceouslimestones thatare Figure 4.5-Geologicalcross-sectionoftheBelagua- Indicated as«hut»isthepositionofRefugiode driving southonNA 1370uptothemountain Lakora area,locatedinthenorthern Axial Zone. fromtheRefugiothereisa Belagua (stop4.5). or thrust oor 27-05-2004, 8:42:23

et al fi gure ., WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

fault-related anticlines that bear an associated north- DAY 5 dipping slaty cleavage, especially in shaly rocks. from Jaca to Labuerda. Stop 4.6: Morning Roncal valley. The Eocene fl ysch of the Southern Pyrenees (Hecho group). Southern Jaca basin and Access: drive down the Roncal valley and stop along External Sierras the main road some 2 km south of the village of Roncal. Stop 5.1: The roadcuts at this stop provide a good outcrop of San Juan de la Peña. Oligocene conglomerates the Eocene turbidites of the Hecho group. Turbidites of the Jaca basin. consist of silici-clastic sandstone/shale decimetric- Access: drive from Jaca to the west along C134 scale cycles, in which the pelitic component is largely and then take the road to the left that drives to the dominant. They represent relatively distal, basin plain San Juan de la Peña monastery. On the way to the facies within the Hecho group, and they have been External Sierras, we stop at San Juan de la Peña for dated as Lutetian in age (Mutti, 1984; Labaume et an overview of the Campodarbe formation that forms al., 1985). the youngest infi ll of the Jaca basin (Puigdefàbregas, Structural landscape: the turbiditic beds describe a 1975). synclinal fold at the outcrop scale, to which an axial Structural landscape: the Campodarbe beds describe planar cleavage is associated. This fold illustrates the the Guarga synclinorium (the present-day axis of characteristic deformation style of the Hecho group, the Jaca basin), whose position in the general cross- which originally accumulated in a foredeep in front section can be observed in Plate 2, fi g. 1. Fluvial of the growing orogen, and was later deformed and sandstone channels and shales grade upwards to incorporated in the mountain chain (e.g. Plate 2, fi g. 1). layered and massive alluvial fan conglomerates, Above this outcrop, in the landscape, we can see a which constitute the San Juan de la Peña massif. carbonate megabreccia bed, also characteristic of the The age of these rocks is Upper Eocene to Lower Hecho group. Clasts within the megabreccia derive Oligocene. The conglomerates show growth strata from carbonate platforms that fl anked laterally the (progressive unconformities) within synclinal folds. turbiditic trough. The position of these platforms The San Juan de la Peña massif is best known by and the geodynamic signifi cance of the megabreccias its monastery of the X-XII centuries, picturesquely have been the subject of diverse interpretations. Some sheltered by the conglomeratic cliffs. authors have proposed a northern provenance of the resedimented material, from hypothetical platforms Stop 5.2: lying on top of the active thrust margin of the basin Embalse de la Peña. Stratigraphy of the (Séguret et al., 1984; Labaume et al., 1985), wheras External Sierras other authors have proposed a southern source area, Access: follow N240 to the south to stop in the from platforms existing in the distal (foreland) margin proximity of the reservoir Embalse de la Peña. of the basin (Barnolas and Teixell, 1994). Proceed along the roadcuts to the south of the The megabreccia bed that we observe is numbered reservoir and the bridge. 5 in the sequence of 8 main units like this in the Structural landscape: the External Sierras are the northern Jaca basin. It shows a large mushroom-like foothills that constitute the South Pyrenean thrust feature interpreted to be a giant water-escape structure front (Plate 2, fi g. 1). Emergent thrusts bring Mesozoic by Labaume et al. (1983). rocks to the surface, starting with Triassic shales and Volume n° 2 - from B16 to B33 n° 2 - from Volume evaporites (Keuper facies) that, when present, form the regional décollement level of the Pyrenean cover thrusts (Séguret, 1972). The stratigraphic succession of the External Sierras is sketched in Fig. 5.2. We can recognize the diverse units in the gorge of the río Gállego, which provides one of the best and most visited sections across the Sierras.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell the area. They arebuilt byUpperOligocene-Lower stacks thatformawell-known touristic attractionof The Mallosisthelocalnameofagrouppicturesque Leonar. between thetwo prominentMallosuptotheCerro Mallos. Fromtheparkingplacewalk upalongthetrail and parkjustbelow theconglomerate pillarsofthe to Riglosontheleft(HU310).Crossvillage Access: interactions. Riglos. Thrust front andproximal alluvialfan Stop 5.3: basin, but muchreducedinthickness. Campodarbe bedsaresimilartothosewithintheJaca counterparts oftheHechoturbidites. The Arguís and formation (middleEocene)arethebasin-margin few hundredmofplatformlimestonetheGuara uppermost Cretaceoustolowest Tertiary age. The and lacustrinelimestones(Garumnianfacies) areof poorly constrainedextent, theoverlying redbeds Cretaceous age. Although theremaybehiatusesof Above theKeuper, wefi al., 1995). and Tertiary oftheExternalSierras(taken fromMillánet Figure 5.2-StratigraphiclogoftheMesozoic continuedown theN240andtake theroad nd rudist-bearingofUpper relationships withtheconglomerates. observed alongtheway up,alsoshow syntectonic 1995). Minorout-of-sequencethrusts,asthose to thelaterantiform(Teixell andGarcíaSansegundo, progressive unconformities(growth strata)associated the conglomeratesofMallos,thatinturnshow river. The leadingedgeofthethrustissealedby located beneathourfeet,justabove theGállego easterly plunge,soitdevelops afoldclosure The antiformthatarchesthethrusthasastrong appears unrootedandcompletelyoverturned. A andB),soitsleadingedge,isolatedbylatererosion, arch (seefrontcover, fi anticline, athrustthatisitselffoldedinanantiformal thrust fault risingfromtheaxialplaneofatight They showed theexistence ofalarge south-vergent until thework byPuigdefàbregas andSoler(1973). puzzled geologistsfordecades,andwas notresolved overturned successions(seefront cover, fi very complex, withrefoldedthrusts andlarge Gállego gorge. The structureoftheSierrasiscertainly view oftheentireExternalSierrasoverlooking the From thetopofitinerarywehave agoodpanoramic (Millán the area,providing evidence forthrustsequences thrust sheets. This kindofrelationshipiscommonin thrust faults, but areinturnoverridden byhigher-level pronounced paleorelief,sealingsomeoftheolder up theCerroLeonar, theconglomeratesonlapa sedimentation. As wewillclearlyseebytheitinerary The Mallosshow beautifulsignsofsyntectonic Fig. 5.3, A andB). segment ofthePyrenees(seefrontcover, fi the lastsynorogenicforelandbasindepositsofthis emergence oftheExternalSierras,andthey represent They accumulatedsynchronicallywiththemain (Puigdefàbregas, 1975;HirstandNichols,1986). south passrapidlytofl formed withinsmallalluvialconesthattowards the from theMesozoicand Tertiary oftheSierras,and The conglomeratesarecomposedofclastsderived of ExternalSierras. Miocene conglomeratesattachedtothesouthernface Barcelona, Spain,e-mail: Geologia, Universitat deBarcelona,Pedralbes,08028 Departament deGeodinamicaiGeofi By Josep Anton Muñoz, Basin III. The Ainsa Afternoon et al ., 1995). g. 2,Platefi uvial sandstonesandshales [email protected] g.1, andfi sica, Facultat de g. 2).It g.2 and g.2 27-05-2004, 8:42:28 g. 5.3, WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Introduction by a northwest-trending imbricate thrust system The Ainsa basin is located in the footwall of the and related folds. Two main thrusts in the footwall Cotiella-Montsec thrust sheet (Seguret, 1972) of the Cotiella thrust sheet, the Atiart and Los (Figs. 5.4b, 5.5a). This cover thrust sheet consists Molinos thrusts, detach the Ainsa turbiditic basin of Mesozoic and syntectonic Paleogene rocks that from underlying Paleocene and Lower Eocene have been detached from the Variscan basement on carbonate platform rocks. The Ainsa basin evolved Lower Triassic evaporites. During the Early Eocene to a piggy-back condition as thrusting propagating southward displacement of the Cotiella-Montsec, the forelandwards and the detachment Mediano anticline Tremp piggy-back basin developed on its hangingwall and the fault-propagation Boltaña fold developed. (Fig. 5.5a). The basin contains platformal and These folds developed during the fi lling of the Ainsa continental terrigenous facies that grade westward basin synchronously with their dextral rotation in the across an oblique lateral ramp of the Cotiella- footwall of the Cotiella thrust sheet. Montsec thrust sheet (in the region of the La Foradada The basin originated as a foredeep ahead of the fault, Fig. 5.5a) into the marine Ainsa turbidite basin innermost of these thrusts in the Early Eocene (Fig. (Nijman and Nio, 1975, Mutti et al., 1988). 5.5a) and evolved into a piggy-back setting as the The Ainsa basin is deformed by the Peña Montañesa thrust front propagated towards the foreland. The thrust system in the northeast, by the north-trending Mediano anticline in the south, and by the Boltaña Figure 5.3 - Cross-sections through the External Sierras anticline to the west (Fig. 5.4b). The structure of (after J. García Sansegundo, in Teixell & García the eastern part of the Ainsa basin is dominated Sansegundo, 1995). Volume n° 2 - from B16 to B33 n° 2 - from Volume

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell systems, packagesofturbiditesarefaulted and currents; however, inparticularpositionsofturbidite indicate depositionfromabroadvariety ofturbidity changes downslope. Mostof the facies involved transitions andonesystempreserved signifi outcrops allow insightsonchannel tooverbank channels andassociatedoverbank elements. The length reachingupto20km,andmostlyformedby than 300m,few kilometreswide,withapreserved anatomy. The turbiditesystemsaregenerallythinner with outcropsallowing thereconstructionoftheir3D embedded. The lattercorrespondtoturbiditesystems mudstones wherecoarser-grained lithosomesare The Ainsa SlopeComplex consistsprimarilyof thick, morethan15kmwideandupto80long. dominated lobeelementsareseveral tensofmetres mudstone interbeddings. The individual sandstone- replaced downcurrent bybasinalsandstoneand termed “outer-fan” sandstone lobes,whichare complex intheJacabasinconsistsofclassically fl the southwestandevolved totheNWintoabasin- The slopecomplex hadafl is upto4,000mthick,40kmlongand30wide. foredeep fi oor complex (Figs.5.5aand5.5b). The basin-fl Figure 5.4b-Geologicalsketch mapoftheEasternpart lled mostlywithaslopecomplex which the Ainsa BasinandoftheBoltaña Anticline. Figure 5.4a-Geologicalsketch mapoftheExternalSierras,Jaca Basinandthe Ainsa Basin. uviodeltaic sourcein cant oor

27-05-2004, 8:44:03 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

deformed by slumping at diverse scales or transformed Within a single depositional cycle, an overall into debris fl ow deposits. The resedimentation process decreasing rate of tectonic deformation caused an interacted with turbidite deposition and introduced a overall decrease in slope gradient, in turn responsible degree of architectural complexity. for contrasts on facies, architectural style and external The interplay between tectonics and sedimentation geometry among stratigraphically consecutive in the Ainsa basin had different scales. Below is a turbidite systems (Fig. 5.5b). summary of these relationships, ordered from basin Pulses of increased deformation caused angular scale to the scale of individual turbidite channel unconfomities at the base of turbidite systems. These elements. evolved overall towards abandonment, trough cycles The propagation of the thrust front caused the Ainsa of channel-complex development and abandonment. basin fi ll to be segmented as four major depositional However, their internal architecture and external cycles which are delineated by widespread angular geometry varies between end-members: 1) vertically- unconformities and are stepped towards the foreland stacked and symmetrical in cross-section and 2) (Fig. 5.5b). These unconformities are submarine complexly juxtaposed and markedly asymmetrical. truncations, up to several hundreds of meters deep, The more complex patterns arose in zones left piggy- which laid parallel to the elongation of the basin and back between growing anticlines. The overall straight were carved by mass wasting. The potential for mass downslope platform of individual turbidite channels wasting was created by forelimb rotation along the was in some cases modifi ed by anticline-related active basin margin and by fl exural downwarping topographies. in the outer basin margin. These “cañons” acted as Objectives: to examine the tectono-sedimentation containers for further slope deposition. relationships of the Ainsa basin, growthg folds and the surrounding thrust systems.

Figure 5.5a - Palaeogeography of the South Pyrenean foreland basin at Early Lutetian. Turbiditic systems of the Ainsa basin had feeder fl uvial systems in the Tremp basin. Clast composition is dominated by limestone clasts derived from Paleocene and Mesozoic rocks, but it also includes granites, volcanic rocks and others, which correlates to the exposed rocks in the hinterland, as it is also indicated by alluvial fans fringing the Northeastern Tremp Basin. From Arbués et al. 1998. Volume n° 2 - from B16 to B33 n° 2 - from Volume

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell turbidites ;2C:resedimentedcarbonates3delta;4alluvialplain5plain.Discontinuities codes Code for surfacesofsubamrinegravitationalerosion Mon :Montilobatfm.;CstCastissentCmCampanuéconglomerates(*)CpCapellaPrPerarrua fm.. stratigraphic units Main depositionalfacies Figure 5.5b-Syntheticstratigraphyofthe Ainsa Basin. Ainsa basin(afterPoblet etal.1988). Figure 5.6a-GeologicalmapoftheMedianoanticline, unconformity ;7:condensedsection8surfaceofsubmarinegravitationalerosion.Codefor localnamesof : FuFuendecampotectosedimentaryunit.From Arbués etal.1988. : Yb : Yerba marls(^);Gu&Gr:Guaralimestones(+)andGrustanmb(*)Cgl:Castilgaleufm :1 :carbonateshelf;2deltaandslope2Amudstones,2Bsilici-clastic : At : Atiart ;Ch-Lsz:Charo-LascorzFo :Formigales. Other Stop 5.4: surrounding structuresarevisible:theBoltaña From thisviewpoint the Ainsa basinandthe Structural landscape to thechurchattopofhill. follow theroadtovillageof Guaso. Take theroad Follow thisroadtoanintersection,turnrightand Guaso andtheGuaraparkaftercrossing Ara river. From Boltañadrive eastto Ainsa. Take theroadto Access : Ainsa basin. Tozal deGuaso.Panoramic viewofthe Stop 5.5: Eocene limestonesoftheBoltañaanticline. This Stopshows thesteep,west-dippinglimbof Boltaña anticline(Fig5.5a). a topographicbarrieratthepresentlocationof basin continuedbasinward intotheJacabasinwithout and 5.4c).Mostoftheturbiditesystems Ainsa basin andmostlyduringtheMiddletoLateEocene the lateststagesofturbiditefi boundary ofthe Ainsa basin,however itgrew during The Boltañaanticlineisconsideredthewestern intersection leadingtothevillageofJanovas. From Broto,drive eastto Ainsa. Stopinthe Access: Boltaña anticline

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Barbastro. Continue southwards past the now submerged village of Mediano. Turn left onto a small side road that leads to the village of Samitier and park the vehicles near the small square and fountain in the centre of the village. From the parking spot in the village take the farm track that leads off to the left and up the hill to the Ermita de San Emiterio and San Celedonio. Several good view Stops can be found along the way overlooking Mediano lake and the western limb of the Mediano anticline. Climb to the old church at the Ermita de San Emiterio and San Celedonio. From here there are excellent views of the Mediano anticline, the onlapping Ainsa turbidites, and the Buil syncline to the left. In the distance (if the weather is clear) the main ranges of the Pyrenean axial zone can be seen. Structural landscape The Mediano anticline is a north-plunging, north- trending detachment anticline developed above the Triassic evaporites (Fig. 5.6a). It is cored by massive to thick-bedded Eocene limestones (Fig. 5.6b). Eocene (Lutetian) turbidites onlap the anticline in a syn-folding growth sequence (Figs. 5.6a, 5.6b and 5.6c). The geometry, facies distribution (from alluvial to deep-water silici-clastics and carbonate rocks) plus the available magnetostratigraphy and biostratigraphy pose restrictions to the kinematic evolution of the anticline (Fig. 5.6c). Stop 5.7: Cotiella and Peña Montañesa thrust sheets. Access: drive back to Ainsa and Labuerda and continue north along the main road (N-138) until the village of Escalona. At this locality turn left to the Añisclo valley and immediately take the small road to the right to the village of Puertolas. Continue up the mountain and Stop just past the small village of Santa Maria before the village of Puertolas. Figure 5.6b - Mediano anticline evolution. Structural landscape From this viewpoint the large klippes at Peña anticline to the west, the Mediano anticline to the east Montañesa and the Cotiella thrust sheets can be and the Monte Perdido-Gavarnie, Peña Montañesa viewed. The fl at-lying fl oor thrusts of these thrust Volume n° 2 - from B16 to B33 n° 2 - from Volume and Cotiella thrust sheets to the north-northeast. sheets bring Mesozoic and Paleocene limestones This viewpoint is an excellent spot to discuss the on top of the Lower Eocene turbidites and marls of main geological features of the area, summarize the the Ainsa basin. The Atiart thrust (fl oor of the Peña structures observed these two days. Montañesa thrust sheet) merges hindwards with the Cotiella thrust. Stop 5.6: Ermita de San Emiterio and San Celedonio. Access: drive to Ainsa and take the C-138 towards

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell thrust sheetshows adistinctstratigraphy. Itinvolves Below theCotiella,Monte Perdido-Gavarnie Eocene. southwards aminimumof20kmduringtheEarly Ainsa basin. The Cotiellathrustsheetwas displaced limestones intotheLower Eocene turbiditesofthe up southwards inthefootwall fromthePaleocene lower thrustsheets. The Cotiellafl extension anddipssouthwards inthenorthabove the dips subhorizontalyformostofitscartographic Perdido-Gavarnie andbasementthrustsheets).It emplacement ofthelower structuralunits(Monte thrust oftheCotiellasheetisfoldedby above the Triassic evaporites (Fig.6.1b). The fl succession (mostlyUpperCretaceous),detached units characterizedbyavery thickMesozoic (Muñoz 1972) ortheso-calledMesozoicUpper Thrust Sheets unit oftheSouthPyreneanCentralUnit(Seguret, part oftheMontsecthrustsheet,mostextended The Cotiellathrustsheet(Fig.6.1a)isthenortheastern Introduction By Josep Anton Muñoz Sheets Cotiella Thrust the Monte-Perdido-Gavarnie and Basement ofthe Axial Zoneand IV. The Alpine structure ofthe from Labuerda toPau. the Medianoanticline. Figure 5.6c-Synsedimentarygrowth andkinematicsof et al ., 1986).Itconsistsofseveral structural DAY 6 oor thrustclimbs oor of Triassic redbeds,unconformablyoverlying the cover oftheselowermost thrustsheetsonlyconsists rocks intrudedbyUpper-Hercynian granitoids.The consist ofmetamorphicLower andUpperPaleozoic with adifferent stratigraphy are exposed. They Below theGavarnie thrust, basementthrustsheets turbiditc successionofthe Ainsa basin. upwards intothelower partofthe Lower Eocene (Seguret, 1972). The MontePerdidothrustsmerge have beendescribedastheMontePerdidothrustsheet units show anincreasingdisplacementwestwards and Upper CretaceousandPaleocene formations. These shows apileofsmallthrustimbricatesrepeatingthe succession. Above thebasement,thisthrustsheet Devonian rockstothebottomofMesozoic southwards intothehangingwall fromtheSilurian- of theGavarnie thrustwhichclimsupsection and Medianoanticlinesarethesoutherncontinuation underneath). The thrustsrelatedwiththeBoltaña structurally incontinuationwiththe Ainsa basin(i.e The MontePerdido-Gavarnie thrustsheetis by theLower Eocenemarlsandturbidites. consists oflimestonesanddolomitesisoverlain the overlying Cotiellathrustsheet. The Paleocene the several kmthickUpperCretaceousseriesof hundred metersthick(800maprox.)incontrastwith Hercynian basement. They formasuccessionseveral and sandstonesrestunconformablyontopofthe and folds. The Upper Cretaceouslimestones,marls shales andlimestonesaffected byHercynian thrusts and Carboniferousslightlytonon-metamorphosed Cotiella. The basementconsistsofSilurian,Devonian succession ismorereducedandmuchthinnerthanthe the Hercynian basementandtheMesozoic 27-05-2004, 8:43:23 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Figure 6.1a - Geological sketch map of the Cotiella thrust sheet and location of stops.

basement, Keuper above, and a thin bed (few tens of structural features of the Cotiella thrust sheet and its meters) of Upper Cretaceous limestones on top. The footwall (Fig.6.1a, 6.1b, 6.1c, 6.1d). On the other basement and the cover are both tightly folded and side of the valley the Cotiella thrust is visible at the affected by thrusts. bottom of the Upper Cretaceous limestone cliffs (1,200 meters high). It lies subhorizontaly above the Objectives: to examine the Alpine thrust structure of lowermost Eocene marls. Northwards of this locality the basement units of the Pyrenean Axial Zone as well the thrust as well as the Upper Cretaceous-Eocene as the structure of the main cover thrust sheets above beds in the footwall (Monte Perdido-Gavarnie thrust the basement. sheet) are tilted to the south 25-30º and truncated by a pair of E-W trending conjugate extensional faults Volume n° 2 - from B16 to B33 n° 2 - from Volume Stop 6.1: (Fig. 6.1c, 6.1d). Cotiella thrust and structure of its footwall. The Eocene marls are folded and affected by a Access: from Labuerda drive north to Bielsa (N-138) prominent N-S, NNW-SSE trending cleavage at a until the village of La Fortunada. Pass the village for high angle with the general E-W, ESE-WNW general 1 km before the road tunnel of Las Devotas. trend of the beds. This geometry is the result of a late Structural landscape tilting of the deformed marls and the Cotiella thrust The purpose of this Stop is to continue a general sheet by thrusting of underlying basement thrust cross section of the area as well as to observe some sheets.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell Continue northtoBielsa(N-138)andturnleft Access thrust sheets.LaLarritectonicwindow. Cross-section of theMontePerdido andGavarnie Stop 6.2: basin. Figure 6.1b-TheSyn-RaftingCotiellabasinreplacedinthetectono-stratigraphicevolution oftheSouth-Pyrenean This isoneofthemostspectaculargeological Structural landscape the river iscrossed. Walk for1hour. track immediatelybeforetheParador andparkonce Pineta-Parador NacionalMontePerdido. Take the footwall. and ofits Thrust Sheet the Cotiella - Structureof Figure 6.1c locality for and akey the Pyrenees scenes of 27-05-2004, 8:43:28 WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Figure 6.1d - Kinematics of the Cotiella Thrust sheet and the Mediano anticline.

understanding the basement involvement into the in the footwall of the Gavarnie thrust outcrop. Alpine thrust structure and the structural relationships Climb the grassy slopes southwards of that valley between the cover and the basement thrust sheets. towards La Estiba in order to get a view of the The course will follow the Pineta glacier cirque across the lower part of the Upper Cretaceous succession of the Gavarnie thrust sheet. The trail climbs up into B16 to B33 n° 2 - from Volume the lateral glacier valley of La Larri where the Triassic red beds

Figure 6.2a - The Gavarnie Thrust at La Estiba.

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell Barnolas, A. and Teixell, A. (1994).Platformsedimentation Spain p.145-146. International Sedimentological congress García delCuraandJ.Soria(eds.), Abstracts of the of South-CentralPyrenees,Spain. surfaces in thesedimentaryinfi McClay, K..(1998).Signifi Arbués P., MuñozJ.A.,PobletJ.;Puigdefàbregas C.and Université deBordeaux 1 (Fig. 6.2a,andFrontcover, fi differences betweenthehangingwall andthefootwall basement initshangingwall andthestratigraphic the foldedunconformityabove theHercynian with theGavarnie thrust.Noteitsantiformalattitude, bottom ofthevalley. This fault contactcorresponds and themetamorphicbasementoutcroppingat the UpperCretaceouslimestones-Triassic redbeds Upper Cretaceousrocksisvisible.Itrestsontopof basement oftheGavarnie thrustsheetbelow the northern ridge.Fromthisviewpoint, theDevonian d’Aspe, HauteChaîne,Pyrénées Atlantiques, supérieur delaMarge Ibérique: Vallée d’Ossau-Vallée sédimentaire etDiagenèsedescalcairesduCrétacé Alhamawi. M.(1992).Sédimentologie, Pétrtographie References Université deBordeaux1. Fieldtrip guidebookwas editedatLaboratoireCIBAMAR, to publishspecialin-housework andformaterialsupport. of Total (L.Moen-Maurel). We thank TOTAL forpermission , oftheUniversitat deBarcelona,Pedralbès(J.Muñoz),and Universitat Autonoma deBarcelona,Bellaterra(A. Teixell) of theUniversité deBordeaux1(R.Bourrouilh),ofthe Mountain belt.Ithasbenefi This work isacontribution totheknowledge ofthePyrenean Acknowledgements End ofthefi of theoutcroppinglower thrustsheets. Cretaceous, Triassic redbedsandgraniticbasement characterize thefoldandthruststructureofUpper between thevillagesofBielsaandParzan inorderto Several observations willbemadealongtheroadcuts Structural landscape leading totheFrenchborder. Drive backtoBielsaandreachmainroadN-138 Access the Gavarnie thrust.Bielsa-Parzán cross-section. Structure ofthegranitebasementinfootwall of Stop 6.3: Florence eld tripandreturnoftheparticipantsto DAY 7 DAY 7 , 320pages tedfromtheResearchprograms cance ofsubmarinetruncation ll of the Ainsa basin(Eocene g.3). In : J.C.Cañaveras, M.A. , IAS, Alicante, Thèse 15th Newsletter 7 Cretaceous examples ofSouthernFrance. extensional transformmargins: Devonian andLower Bourrouilh R.(2000).Mud-moundsondivergent and 81. Springer Verlag. Pyrenean Basin. Megaturbidites inanInterplatebasin:example oftheNorth Bourrouilh R.(1987).Evolutionary Mass-Flow- cartes géol.1/50.000e. de Espana beticas enelMediterraneooccidental. (Baleares). La Terminacion NororientaldeLasCordilleras Tectonica delaIslaMenorcaydelNoresteMallorca Bourrouilh R.(1983).Estratigrafi géologiques. au 1/50.000etfondstopographiques,2planchesdecoupes planches dansletexte, 6horstexte :2cartesgéologiques Université deParis V bétiques enMéditerranéeoccidentale. (Baléares). Laterminaisonnord-orientaledesCordillères Tectonique del’îleMinorqueetduNEMajorque Bourrouilh R(1973).Stratigraphie,Sédimentologieet XC, fasc 4,p.363-380,13fi Sierras deLevante deMajorque. Bourrouilh R.(1970).LeproblèmedeMinorqueetdes 25-43, 12fi l’Aquitaine méridionale. supérieur àfaciès urgonien danslesPyrénéesoccidentaleset Organisations sédimentairesetpaléoécologiquesdel’Aptien Bouroullec J.,Delfaud J.andDeloffre R.(1979). corrélations Chaîne, PyrénéesCentrales,Sédimentologieetpremières Le Cambro-Ordovicien del’Hospice deFrance,Haute Bouquet C.,BourrouilhR.,GuérangéB.et Vaché E.(1990). 405-435. des Pyrénées. Mendibelza : dépôtsdecônessous-marinsduriftalbien Boirie J.M.andSouquetP. (1982).LesPoudinguesde Université de Toulouse de Mendibelza(Pyrénées Atlantiques). Boirie J.M.(1981).Etudesédimentologiquedespoudingues BRGM ed d’années, itinérairesgéologiquesdansleparcnational. Mirouse R.andRogerP. (1985).Pyrénées : 500millions Bixel F., ClinM.,LucasCl.,Majeste-Menjoulas Pyrenees pays nord-pyrénéen. 1995b. Evolution géodynamiqueetpétrolièredel’avant- Biteau J.J.,LeMarrec A., Moen-MaurelL.andNoualG. 545-552. Pyrénées-Atlantiques, France. l’évaluation descarrièresdemarbres : exemple d’Arudy, F.G. (1997). Application duquadripôleélectrostatiqueà Benderitter Y., BourrouilhR.andBourrouilh-LeJan Geology foreland basin(Eocene,Jacabasin,southernPyrenees). and collapseinacarbonate-dominatedmargin ofaturbiditic , 12,1107-1110. , Toulouse, Fieldtripguidebook. , 101p. , t.99,1vol. 692p.,1vol. 95pl.ethors-textes, 2 g. 1pl. , p.131-133,1fi in SassiandBourrouilh,Eds.,IGCPn°5, Bull. C.R.P. Elf-Aquitaine GeoMarine Letters Soc. Géol.France Spec.Meetingon , 115p. I, 2tomes,822p.,196fi Géobios, Mémoire spécial g. g. C. R. Acad. Sci.Paris Ann. Soc.géol. Nord, , volume 7,n°2,p.69- a, Sedimentologiay Mem. Inst.Geol.Min. Thèse 3èmecycle, , vol . 6,n°2p. The Geological Thèse d’Etat. g. et95 27-05-2004, 8:43:35 n°3, , 325, t. WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16

Exploration in Murzuq Basin, M. A. Sola and D. Worsley, Basin determined from subsidence curves. Géol. Mag, 121, Ed. Elsevier, ch.23, p. 463-483. 421-428. Bourrouilh R. and Alhamawi M. (1993). Données Burbank, D., Puigdefàbregas, C. and Muñoz, J.A. (1992a). nouvelles sur l’évolution de la marge ibérique dans les The chronology of the Eocene tectonic and stratigraphic unités tectoniques des Eaux Chaudes, Vallée d’Aspe-Vallée development of the eastern Pyrenean foreland basin, d’Ossau. C. R. Acad. Sci. Paris. t. 317, série II, p.979-985. northeast Spain. Geol. Soc. Am. Bull. 104, 1101-1120. Bourrouilh R. and Doyle L. J. (1985). Petroleum Geology, Burbank, D., Verges, J., Muñoz, J.A. and Bentham, P. Tectonics and Sediments of the French Pyrenees and (1992b). Coeval hindward- and forward-imbricating Associated Aquitaine Basin. A.A.P.G. Field Seminar, 103 p. thrusting in the central southern Pyrenees, Spain: timing and Bourrouilh R. and Mirouse R. (1984). Le Paléozoïque rates of shortening. Geol. Soc. Am. Bull. 104:3-17 supérieur des bordures du Bassin d’Aquitaine : analyse Canérot J. and Lenoble J.L. (1991). Diapirisme sur une de données bibliographiques inédites. Géologie profonde marge en distension, puis en décrochement. (Exemple des de la France, Thème 7, Bassins paléozoïques cachés sous Pyrénées occidentales françaises). Public. Sp. N° 13 de l’Aquitaine. Doc. BRGM n° 81-7, 10 p. l’Association des Sédimentologistes Français, 125 p. Bourrouilh R. and Gorsline D. S. (1979). Pre-Triassic fi t Canérot J. and Lenoble J.L. (1993). Diapirisme crétacé sur la and alpine tectonics of continental blocks in the Western marge ibérique des Pyrénées occidentales : exemple du Pic Mediterranean. Geol. Soc. Am. Bull. v. 90, 1074-1083. de Lauriolle ; comparaison avec l’Aquitaine, les Pyrénées Bourrouilh R. et Offroy B. (1983). Séquences de mass-fl ow centrales et orientales. Bull. Soc. Géol. Fr., 164, 5, 719-726. évolutif - mégaturbidites du fl ysch Sénonien Nord-Pyrénéen. Canérot J. and F. Delavaux, 1986. Tectonique et Traitement informatique et Anatomie du bassin Sénonien. sédimentation sur la marge nord ibérique des chaînons Colloque sur le Sénonien. Marseille, septembre 1983. Géol. béarnais, Pyrénées basco-béarnaises. C. R. Acad. Sci. Paris. Méd. X, 345-359. v. 302, sér. II, n° 15, p. 951-956. Bourrouilh R., Cocozza T., Demange M., Durand Delga M., Casteras M. (1974). Les Pyrénées, in J. Debelmas Gueirard S., Guitard G., Julivert M., Martinez F.J., Massa ed.“ Géologie de la France ”, tome 2, p. 296-345, Masson, D., Mirouse R. et Orsini J.B. (1980). Essai sur l’évolution Paris paléogéographique, structurale et métamorphique du Choukroune P. and ECORS Team (1989). The ECORS Paléozoïque du Sud de la France et de l’Ouest de la Pyrenean deep seismic profi le: Refl ection data and the Méditerranée. 26ème Congrès géol. Intern. Colloque C 6, overall structure of an orogenic belt. Tectonics, Washington, 159-188, 11 fi g. Paris. 8, 1, pp. 23-39. Bourrouilh R., Coumes F. et Offroy B. (1984). Mécanismes Choukroune P. and Mattauer M. (1978). Tectonique des séquentiels et événements exceptionnels du Flysch Sénonien plaques et Pyrénées: sur le fonctionnement de la faille Nord-Pyrénéen. Corrélations par les dépôts gravitaires transformante nord-pyrénéenne; comparaison avec des profonds. Bull. Soc. géol. Fr. 7, XXVI, 1223-1234. modèles actuels. Bull. Soc. Géol. Fr., Paris (7), XX, p. 689- Bourrouilh R., Doyle L.J., Gapillou Cl., Offroy B. et Perlet J. 700. (1984). Les massifs paléozoïques basques et leur couverture Choukroune P. (1974). Structure et évolution tectonique de récente. Mécanismes de sédimentation du fl ysch du Crétacé la zone Nord-Pyrénéenne. Analyse de la déformation dans supérieur. Livret guide de l’Excursion AGSO, 19, 20 et 21 une portion de chaîne à schistosité subverticale. Mém. Soc. septembre 1984, 84 p., nbses fi g. BRGM-AGSO. Géol. Fr., nlle série, t. V, n° 127, p. 1-116. Bourrouilh R., Richert J.P. and Zolnai G. (1995). The Choukroune P., Le Pichon X., Seguret M. and Sibuet J.C. North Pyrenean Aquitain Basin, France : Evolution and (1973) − Bay of Biscay and Pyrenees. Earth and Planet Sc. Hydrocarbons. AAPG Bulletin, V 79, N° 6 (June 1995), Lett. 18, p. 109-118. 831-853. Choukroune P., Seguret M. and Galdeano A. (1973) − Bourrouilh-Le Jan F. G. (1973). Dolomitisation actuelle Caractéristiques et evolution structurale des Pyrénées : un dans le monde. Une revue. Sciences de la Terre, XVIII, 3, modèle de relations entre zone orogénique et mouvement 279-298. Nancy. des plaques. Bull. Soc. Géol. Fr. (7), XV, n° 5-6, 600-611. Bourrouilh-Le Jan F. G. (1975). Géochimie et isotopie des Combes P.J. (1969). Recherches sur la genèse des bauxites calcaires et dolomies de Lifou, sondage et subsurface : dans le Nord-Est de l’Espagne, le Languedoc et l’Ariège

diagenèse et évolution d’une plate-forme carbonatée du SW (France). Mém. C.E.R.G.H., Montpellier, t. III-IV, 1 vol. B16 to B33 n° 2 - from Volume Pacifi que. 11è Cong. Intern. Sédim. Thème 7, 25-32, Nice. 275 p. Bourrouilh-Le Jan F. G. (1996). Plate-formes carbonatées Coney, P.; Muñoz, J.A., McClay, K. and Evenchick, C. 1996. et atolls du Centre et Sud Pacifi que. Stratigraphie, Syntectonic burial and post-tectonic exhumation of the sédimentologie, minéralogie et géochimie. Diagenèses southern Pyrenees foreland fold-thrust belt. Journal of the et émersions : aragonite, calcite, dolomite, bauxite et Geological Society, London, 153, 9-16. phosphate. Doc. BRGM, 249, 365p. Curnelle R. (1983). Evolution structuro-sédimentaire du B.R.G.M., ELF-Rap, ESSO-REP and SNPA (1974). Trias à l’Infralias d’Aquitaine. Bull. Centres Rech. Explor. Géologie du bassin d’Aquitaine .B.R.G.M. Ed. Prod. Elf Aquitaine, 7, 1, 69-99, 16 fi g. Brunet M.F. (1984). Subsidence history of the Aquitaine Curnelle R., Dubois P. and Seguin J.C. (1982) − The

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Volume n° 2 - from B16 to B33 B16 - B16 Leaders: R.Bourrouilh,L.Moen-Maurel,J.Muñoz,A.Teixell Rupke (1976).Larger scaleslumpinginafl Pyrénées (Espagne). d’avant-fosse. Exemple dusilloncrétacéversant Suddes chevauchements etséquencesdedépôtsdansunbassin Souquet P. andDeramondJ.,(1989). Séquence de International, Paris, des Pyrénées évolution desbassinsdesédimentationdanslecycle alpin Souquet P. andDebroasE.J.(1981). Tectonogenèse et p. 5-20. de lageologiadel Alto Aragon Occidental. Soler M.andPuigdefàbregas C.(1970).Lineasgenerales Tome 1:129p,t.2:annexes :34pl,XVIIIp.Bibliographie. Pau. Thèse Crétacé/Tertiaire, duPaléocène etdel’YprésienauSud Seyve C.(1984).Etudemicropaléontologiquedupassage Pyrenean Basin(NorthSpain). seismicity inthePyreneesfrommegaturbidites intheSouth- Seguret M.,LabaumeP. andMadariagaR.(1984).Eocene Géologie Structurale,n°21. Publication deUstela,Université deMontpellier, décollées delapartiecentraleduversant suddesPyrénées. Séguret M.(1972).Etudetectoniquedesnappesetséries 130. Southwestern Pyrenees, Cénomanien) danslesPyrénées. Peybernès B.(1985).LeGroupe duFlyschNoir(Albo- Dol J., Thieuloy J.P., Bonnemaison M.,Manivit H.and Souquet P., DebroasE.J.,PonsPh.,Fixari G., RouxJ.C., evolution ofthePyrenees. balanced cross-sections,geometricconstraintstotracethe and DeramondJ.(1989).ECORSDeepSeismicdata Villien A., MatheronP., Bareyt M.,Seguret M.,CamaraP. Roure F., ChoukrouneP., Berastegui X.,MuñozJ.A., Geology North Atlantic fromtheLateCretaceoustopresent. plate boundariesbetweenEurasia,Iberiaand Africa inthe Roest, W.R. andSrivastava, S.P.(1991). Kinematicsofthe Fieldtrip pays Nord-Pyrénéen, (1995). Evolution géodynamiqueetpétrolièredel’avant- Richert, J.P., Moen-Maurel,L.,BiteauJ.J.,CanérotJ., Conference Field Trip Guidebook Taberner C.(1983).Evolución ambiental ydiagenéticade (B9): 18117-18134. teleseismic data. of thelithospherebeneathPyreneesfromlocaland Souriau A. andGranetM.(1995). A tomographicstudy 53, fascicule 2,p.149-192,Université deGrenobleed.. (1977). LachaînealpinedesPyrénées Souquet P., Peybernès B.,BillotteM.andDebroasE.J. 9, 1,183-252. the vicinityofLacqandMeillongasfi (1995). The NorthernPyrenees Thrust BeltandForeland in Richert J.P., Moen-MaurelL.,CanérotJ.andBiteauJ.J., , 19:613-616. guidebook,62p. 3ème cycle, Université Pierre-et-Marie-Curie. in ColloqueC7,26èmeCongrèsGéologique Journal ofGeophysical Research Mémoire B.R.G.M C. R. Acad. Sc.Paris, Soc. Géol.France Annual Meeting, Jour geol. Soc.London Tectonics Mar. Geol., . 68p. Bull. CREPElf Aquitaine, , 8(1),41-50. . n°107p.213-233. in Géologie Alpine elds. 309,137-144. 55,117-131. Pirineos yc basin, ysch AAPG Nice , 132,121- , v. 96, série , 100 t.

Occidentales françaises. Viennot P. (1927).RecherchesstructuralesdanslesPyrénées Earth andPlanetaryScienceLetters, the emplacementofPyreneanlherzolitesandgranulites. Vielzeuf, D.andKornprobst, J.(1984).Crustalsplitingand (ed.). ChapmanandHall,London,255-264. Occidentales. de décrochementdansl’avant-pays norddesPyrénées Zolnai G.(1975).Surl’existence d’unréseaudefailles Paris. in Histoire structurale duGolfedeGascogne Zolnai G.(1971).LefrontnorddesPyrénéesOccidentales, 1.30, Technip, Paris. in Histoire structurale duGolfedeGascogne, d’Aquitaine (contribution àl’histoireduGolfedeGascogne), Winnock E.(1971).Géologiesuccinctedubassin 131, 3-19. Bulletin Technique Exploration-Production Elf Aquitaine, nord pyrénéenne :conséquencessurl’exploration pétrolière. Villien A. andMatheronP. (1989).Géodynamiquedelazone 155, 267p. levels inthrustgeometry Pyrenean fold-and-thrustbelt:roleofforelandevaporitic Verges, J.,Muñoz,J.A.andMartinez, A. (1992).South Marine andPetroleum Geology pre-, syn-andpost-collisionalcrustal-scalecross-sections. S. (1995).EasternPyreneesandrelatedforelandbasins: Cires, J.,DenBezemer, T., Zoetemeijer, R.andCloetingh, Verges, J.,Millan,H.,Roca,E.,Muñoz,J.A.,Marzo,M., VI(2), 265-271. the SouthernCentralPyrenees. Verges, J.,andMuñoz,J.A.(1990). Thrust sequencesin III, p.1301-1321. Jurassique duBassindeParis. application auxcorrélationschronostratigraphiquesdansle F. and Trifi Vail P.R., ColinJ.P., JanDuCheneR.,Kuchly J.,Mediavilla Soc. Geol.España, sector centraldelaCuencaJaca(Pirineocentral). Teixell A. andGarcia-Sansegundo J.(1995).Estructuradel limestone. Stress andfl Teixell, A., Durney, D.W. and Arboleya, M.L.(2000). budget inthewestcentralPyrenees. Teixell, A. (1998).Crustalstructureandorogenicmaterial Soc. London Pyrenees: basementandcover thrustgeometries. Teixell, A. (1996). The Ansó transectofthesouthern 241-249. of thepyrenean Axial Zone. Teixell, A. (1990). Alpine thrustsatthewesterntermination 1-1400. de laCuenca Vic. los dépositosdel Terciario inferior(Paleoceno yEoceno) 238 lieff V. (1987).Lastratigraphieséquentielleetson Journ. Struct.Geol., uid controlondecollementwithincompetent , 153,301-310. Rev. Géog. Phys.Géol.Dyn., 8,207-220. Tesis Doctoral, Univ. deBarcelona, Bull. Serv. CarteGéol.France in: Thrust tectonics in: Thrust Bull. Soc.géol. France. 22,349-371. . 12(8):893-915. Bull. Soc.Géol.France Bull. Soc.Géol.France, Tectonics, 67: 383-386. XVII,3,219- , McClay, K.R. p.IV1.1– 17,395-406. Jour. geol. , Technip, 27-05-2004, 8:43:42 (8),6, Rev. , n° , 8, 8,

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