BSGF- Earth Sciences Bulletin 2018, 189,10 ©R. Leprêtre et al., PublishedbyEDP Sciences 2018 https://doi.org/10.1051/bsgf/2018009 Available online at: www.bsgf.fr The Tell-Rif orogenic system (Morocco, Algeria, Tunisia) and the structural heritage of the southern Tethys margin Rémi Leprêtre1,2,*, Dominique Frizon de Lamotte1, Violaine Combier3, Oriol Gimeno-Vives1, Geoffroy Mohn1 and Rémi Eschard3 1 Université deCergy-Pontoise,Département Géosciences et Environnement (GEC), 1 rueDescartes, 95000Neuville/Oise Cedex, France 2 Sorbonne Université, CNRS-INSU, Institut desSciences dela TerreParis, ISTeP UMR7193,75005 Paris,France 3 Total-EP,2 place JeanMillier,92078Courbevoie LaDéfense,France Received: 30January2018/ Accepted: 15June 2018 Abstract – TheTell-Rif(TellinAlgeriaandTunisia;RifinMorocco)istheorogenicsystemfringingtothe souththeWestMediterraneanbasins.Thissystemcomprisesthreemajortectonic-palaeogeographiczones from north to south: (1) the internal zones (AlKaPeCa for Alboran, Kabylies, Peloritan, Calabria) originating from the former northern European margin of the Maghrebian Tethys, (2) the “Flyschs zone” regardedastheformercoveroftheoceanicdomainand(3)theexternalzones,formingtheformersouthern Maghrebian Tethys margin more or less inverted. The Tell-Rif is interpreted as the direct result of the progressive closure of the Maghrebian Tethys until the collision between AlKaPeCa and Africa and, subsequently,thepropagationofthedeformationwithinAfrica.Thisgivesaconsistentexplanationforthe offshore Neogene geodynamics and most authors share this simple scenario. Nevertheless, the current geodynamicmodelsdonotcompletelyintegratetheTell-Rifgeology.Basedontheanalysisofsurfaceand sub-surfacedata,weproposeareappraisalofitspresent-daygeometryintermsofgeodynamicevolution. Wehighlightitsnon-cylindricalnatureresultingfromboththeMesozoicinheritanceandtheconditionsof the tectonic inversion. During the Early Jurassic, we emphasize the development of NE-SW basins precedingtheestablishmentofanE-WtransformcorridorconnectingtheCentralAtlanticOceanwiththe Ligurian Tethys. The Maghrebian Tethys developed just after, as the result of the Late Jurassic-Early Cretaceous left-lateral spreading between Africa and Iberia. By the Late Cretaceous, the occurrence of severaltectoniceventsisrelatedtotheprogressiveconvergenceconvergencebetweenthetwocontinents.A majorpre-Oligocene(pre-35Ma)compressionaleventisrecordedintheTell-Rifsystem.Theexistenceof HP-LTmetamorphicrocksassociatedwithfragmentsofmantleintheExternalMetamorphicMassifsofthe Eastern Rif and Western Tell shows that, at that time, the western part of the North-African margin was involved in a subduction below a deep basin belonging to the Maghrebian Tethys. At the same time, the closureoftheWestLigurianTethysthrougheast-vergingsubductionledtoashiftofthesubduction,which jumpedtotheothersideofAlKaPeCainvolvingbothEastLigurianandMaghrebianTethys.Slabrollback led to the development of the Oligo-Miocene back-arc basins of the West-Mediterranean, reworking the previousWestLigurianTethyssuture.ThedockingofAlKaPeCaagainstAfricaoccurredduringtheLate Burdigalian(17Ma).Subsequently,theslabtearingtriggeredwestwardandeastwardlateralmovementsthat areresponsiblefortheformationoftheGibraltarandTyrrhenianArcsrespectively.Theexhumationofthe ExternalMetamorphicMassifsoccurredthroughtectonicunderplatingduringthewestwardtranslationof the Alboran Domain. It resulted in the formation of both foredeep and wedge-top basins younger and youngerwestward.Thelackoftheseelementsintheeasternpartofthesystemssignsadifferentevolution dominated by frontal accretion. In the discussion, we precisely address the origin of the non-cylindrical behavior of the orogenic system and question the mechanisms explaining at large scale the phases of coupling/uncoupling between the major plates. Keywords:Tell-Rif orogenic system (Algeria, Morocco, Tunisia) / Tethys / West Mediterranean / coupling vs decoupling/ frontalaccretion vs tectonic underplating *Corresponding author: [email protected] ThisisanOpenAccessarticledistributedunderthetermsoftheCreativeCommonsAttributionLicense(http://creativecommons.org/licenses/by/4.0),whichpermits unrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited. R.Leprêtre et al.: BSGF2018, 189,10 Résumé – Lesystèmeorogéniquetello-rifain(Maroc,Algérie,Tunisie)etleproblèmedel’héritage structuralsurlamargesudtéthysienne.Le Tell-Rif (Tell en Algérie et Tunisie; Rif au Maroc) est un systèmeorogéniquequibordeausudlesbassinsouestméditerranéens. Ce systèmecomprendtroiszones tectono-paléogéographiques principales, du Nord au Sud: (1) les zones internes (ou AlKaPeCa pour Alboran-Kabylies-Peloritain-Calabre)issuesdel’anciennemargeseptentrionale,côtéEurope,delaTéthys Maghrébine, (2) le domaine des Flyschs, considéré comme la couverture sédimentaire de ce domaine océaniquedisparuet(3)leszonesexternes,représentantlamargesudtéthysienneplusoumoinsinversée. DanslecontextedelaformationdesbassinsdeMéditerranéeoccidentale,leTell-Rifrésulteraitdirectement delafermetureprogressivedelaTéthysMaghrébinejusqu’àlacollisionentreAlKaPeCaetl’Afrique,puis, de la propagation dans la plaque Afrique vers le sud de cette déformation. Ce scénario, qui fournit une explication satisfaisante pour la géodynamique néogène, est approuvé par la majorité des auteurs. Cependant, ces modèles géodynamiques tiennent peu compte de la géologie tello-rifaine en se basant la plupartdutempssurl’arcbético-rifainetoubliantdefaitl’anciennemargetéthysiennenord-africaineetles données sur les Kabylies. Sur la base de données de surface et de sub-surface, nous proposons une réévaluation de la géométrie actuelle duTell-Rif au regard de sonhistoire géodynamique. Cette synthèse nouspermetdesoulignersonimportantnon-cylindrisme,quirésulteàlafoisdel’héritagemésozoïqueetdes conditionsdel’inversion.AucoursduJurassiqueinférieur,nousinsistonssurledéveloppementdebassins d’orientations NE-SW antérieurs à la mise en place d’un grand couloir transformant qui relia l’Océan AtlantiqueCentralàlaTéthysLigure.LaTéthysMaghrébines’estdéveloppéepostérieurement,enréponse à l’ouverture en contexte de décrochement senestre de l’espace entre la plaque ibérique et l’Afrique au Jurassique supérieur-Crétacé inférieur. Lors du Crétacé supérieur, plusieurs événements tectoniques survinrentaucoursdurapprochementAfrique-Europe.Unévénementcompressifmajeurintervientavant l’Oligocène (anté-35Ma). L’existence de roches métamorphiques de HP-BT associées à des fragments mantelliques dans les «Massifs Externes à Schistosités du Rif oriental et du Tell occidental montreeneffetqu’àcetteépoque,lapartieoccidentaledelamargesud-téthysienneaétéimpliquéedansune subductionsousunbassinprofond,appendicedelaTéthysMaghrébine.Enmêmetemps,ladisparitiondela TéthysLigureoccidentale,dansunesubductionàvergenceversl’est,apermisunsautdesubductionducôté sud-est d’AlKaPeCa, pour finalement impliquer les Téthys Maghrébine et Ligure orientale. Le retrait du panneau plongeant d’abord vers le sud, puis vers l’ouest, permit la mise en place des bassins arrière-arc oligo-miocènesdeMéditerranéeoccidentaleréutilisantlasuturedelaTéthysLigureprécédemmentfermée. L’arrimagedumicrocontinentAlKaPeCacontrel’AfriqueseproduitauBurdigaliensupérieur(17Ma).Àsa suite, le panneau plongeant subit deux déchirements latéraux vers l’ouest et l’est, à l’origine des arcs de GibraltaretTyrrhénien,respectivement.L’exhumationdesmassifsexternesàschistositéfutalorspermise via un sous-plaquage tectonique lors du déplacement vers l’ouest du domaine d’Alboran. Ceci eut pour conséquencelaformationd’unefossed’avant-paysetdebassinssupra-nappesdeplusenplusjeunesvers l’ouest.Cesélémentsn’existentpasàl’estetdémontrentuneévolutionstructuraledifférente,dominéepar l’accrétionfrontale.Dansladiscussion,nousapportonsdesélémentsprécissurl’originedunon-cylindrisme du système et sur les mécanismes qui pourraient expliquer à grande échelle les phases de couplage/ découplage entre les plaques tectoniques en jeu. Motsclés:systèmeorogéniquetello-rifain(Maroc,Algérie,Tunisie)/Téthys/Méditerranéeoccidentale/couplage vs.découplage/ accrétion frontale vs.sous-plaquage 1 Introduction (Alvarez, 1974; Bouillin, 1986). A two-steps scenario is currently considered for the formation of the West Mediterra- neanbasins(Bouyahiaouietal.,2015;Medaourietal.,2014and TheWestMediterraneanback-arcbasinsdevelopedsincethe referencestherein).AfirstepisodeofNNW-SSEextension(Aïte Oligoceneinrelationwiththeroll-backofthesubductionofthe Ligurian-MaghrebianTethys1(LMT)(Bouillin,1986;Doglioni and Gélard, 1997) occurred until the docking of AlKaPeCa blocksagainstAfrica,whichfollowingradiochronologicdataon etal.,1999;FrizondeLamotteetal.,2000;Gueguenetal.,1998; granites cross-cutting the African crust, occurred during the JolivetandFaccenna,2000;Jolivetetal.,2008;Lonerganand Lower Miocene before or at 17Ma (Abbassene et al., 2016; White,1997;MalinvernoandRyan,1986;Réhaultetal.,1984; Aïssaetal.,1999;Chazotetal.,2017).AsecondepisodeofE-W VergésandSàbat,1999;Fig.1).Thenetresultoftheroll-back extension is related to slab tearing, delamination and rapid was the stripping-off of the Alboran, Kabylie, Peloritan and translationswestward,formingtheBetic-RifArc(orGibraltar Calabria (AlKaPeCa) domains from the European margin Arc),andeastward,formingtheTyrrhenianArc.Thisepisode can be tracked in the tectono-sedimentary record from the 1 Inouracceptation,theLigurianTethysisthesouthernpartofthe SerravaliantotheTortonianfromthewesternTelltothecentral Alpine Tethys and the Maghrebian Tethys is the former oceanic Rif (among others, Delteil, 1974; Guardia, 1975; Mattauer, connectionbetweentheLigurianTethysandCentralAtlantic.Wewill 1958;Polvêche,1960;Septfontaine,1983). see below that the Ligurian Tethys likely comprised two parallel TheTell-Rif(TellinAlgeriaandTunisia;RifinMorocco) branches. or Maghrebides is the orogenic system fringing the West Page2 of35 R.Leprêtre et al.: BSGF2018, 189,10 Fig. 1. Structural scheme of the Western Mediterranean region (after Etheve et al., 2016). West Mediterranean, Europe and North Africa structuralfeaturesareshown,differenciatingtheAlpineandintracontinentalbelts,respectively.LocationofthemapofFigure2isgiven(red polygon).Notethat the Variscan frontisonly drawn forNorthwestAfrica. Mediterranean basins to the south (Durand-Delga, 1969; propose a completely different model. Their model suggests Wildi, 1983). This system comprises 3major tectonic-palae- that Alboran was initially (i.e. during the Mesozoic) located ogeographic zones, i.e., from north to south: (1) the internal alongtheAfricanmarginandconsequentlyseparatedfromthe zones (AlKaPeCa) originated from the former northern Kabylie, which, together with the Calabrian and Peloritan EuropeanmarginoftheLMT;(2)the“Flyschszone”regarded terranes,wereontheEuropeansideoftheMaghrebianTethys. as the former sedimentary cover of the LMT and (3) the This provocative proposition is interesting but disregards externalzones,theformerNorthAfricanpassivemarginofthe several geological evidences: LMT (Fig. 2). (cid:1) the strong palaeogeographic affinities between Alboran InthegeodynamicframeoftheWestMediterraneanbasins and the Kabylie during the whole Mesozoic, especially formation,theTell-Rifisinterpretedasthedirectresultofthe during Triassic time, these two domains being character- progressive closure of the LMT until the collision of ized by “Alpine” facies contrasting with the “Germanic” AlKaPeCa with Africa at 17Ma. Such a scenario gives a facieswhichcharacterizebothAfricanandIberianmargins consistent explanation for the offshore geodynamics and is (Bouillin, 1986; Durand-Delga, 1969); nowsharedbyalmostalltheauthors.Somediscussionsremain (cid:1) offshore data (Booth-Rea et al., 2007; Medaouri et al., about the importance of the westward movements (i.e. the 2014),suggestingratherWSWthanNWmovementsofthe initialpositionofAlboranterrane[the“Al”oftheAlKaPeCa Alboran Domain; system]) and their precise timing. The difference between (cid:1) seismic data showing that Kabylie-like terranes can be reconstructions by Van Hinsbergen et al. (2014) and Crespo- currently followed offshore up to the Oran meridian Blanc et al. (2016) are considerable in terms of westward (Domzig et al., 2006), i.e. in the assigned root zone of migration of the Alboran domain but are end-members of a Alboran in the Vergés and Fernàndez (2012) model. single model. This consensus has been recently broken by Vergés and For these reasons, we do not retain this scenario and the Fernàndez (2012) followed by Casciello et al. (2015), who presentpaperfollowstheframeofclassicalmodelsconsider- Page3 of35 R.Leprêtre et al.: BSGF2018, 189,10 S NI U T N m (D) (C) CollohguodELESSER KABYLIAadrejdeMConstantine 100 k Tell-Rif thrust Internal zones : AlKaPeCabasement + «Dorsale calcaire» Flyschs units Plio-Quaternaryautochthonous cover foreland (Atlas) ust hr BABORS aPeCa t MM) naenarr ALGIERS GREATERKABYLIA BIBAN HODNA BASIN usts and faultsAlK Tell-Rif higher nappes Tell-Rif northernmost units External Metamorphic Massifs (E Tell-Rif external windows ure3isshown. e hr g tide Tenes SINESRAUO Main t eninFi v M tseW (B) Mostaganem.B fileOranhC Figure 8a Neogene magmatism Plio-Quaternary Tell-Rifcover / Chelif limitsLate Miocenethrust-top basins Miocene foredeeps hefourcross-sectionsgi t YR N AARDECESS erohsnO cationof B o EK L -BER m. (A) FFJNAl Hoceima AMATEKAG Figure 7aGUERCIFTazaBASIN Internal zones plate units (margin, basin) Oceanic crustAlgerian Basin apoftheTell-Rifsyste Tanger RHARB BASINAT Structuralm B 2. A R g. Fi Page4 of35 R.Leprêtre et al.: BSGF2018, 189,10 ing the European origin for all the AlKaPeCa domain. swing is observed. These are late-acquired Neogene features Nevertheless,theselattergeodynamicmodelsfailtointegrate related to the Alboran motion and associated vertical axis at least two major issues: they do not incorporate all recent rotations(e.g.Cifellietal.,2016;Plattetal.,2013).TheBetic- geological developments in the Betics geology and forget Rif belts thus defines a very arcuate orogenic system partially or totally the Tell-Rif geology. We will not develop (Lonergan and White, 1997). The Tell also extends in Sicily theBetics geology here.Asa matteroffact, dealing withthe towards the Apennines, with a “symmetrical” 90° anti- Rif history for Mesozoic and Cenozoic times makes more clockwise swing within the Calabrian arc. In the literature, senseincomparisonwiththeevolutionoftheTell,astheyboth theTell-Rifbeltispresentedasacylindricalorogenicsystem belong to the South Tethys margin. The comparison between with continuous palaeogeographic-palaeotectonic zones, RifandBeticsisanimportanttopicbutmainly fortherecent namely the internal zones (AlKaPeCa), the Flyschs zone post-EarlyMiocene stages whenRifandBetics shareseveral and the external zones (see the masterly synthesis of Wildi, commonevents.Forthesakeofgeologicalcoherencesincewe 1983). However, these zones are not continuous and very considertheevolutionoftheSouthTethysmargin,wepropose important along strike variations occur in the external zones arenewedviewofboththeTellandtheRifevolution,witha (Figs. 2 and 3). Relying on the available literature and new particular emphasis on the following points: cross-sections along the belt, we will describe the first-order (cid:1) the importance of the Paleozoic and early Mesozoic geometry of the system and its lateral variations from the structural inheritance, which strongly influenced the internal zones toward the external ones in the following southern Tethys margin geometry; sections. (cid:1) the significance of pre-Late Oligocene (pre-30Ma) compressionaleventsnotonlyintheAtlasSystem,where 2.1 The AlKaPeCa and Flyschs domains theyarewellestablished(seeareviewinFrizondeLamotte et al., 2000, 2009, 2011), but also in the Tell-Rif system, The internal zones of the Tell-Rif belt, shared with the where their effects were often ignored or minimized; Betics,belongtotheAlKaPeCadomain,asdefinedbyBouillin (cid:1) the existence of high pressure-low temperature (HP-LT) (1986). AlKaPeCa is a continental domain with European metamorphic suite, typical of subduction zones, (Negro affinities(Bouillin,1986;Michardetal.,2002,2006).Except et al., 2007) associated with fragments of serpentinites in fromadismemberedMesozoictoEocenecover(theso-called the Eastern Rif (Michard et al., 1992, 2007, 2014) and “Dorsale Calcaire”), unconformably capped by upper Oligo- likely in the Western Tell (Fenet, 1975; Guardia, 1975; cene to lower Miocene clastics, it mainly shows Paleozoic Michardetal.,2006,2007).Thissuggeststhatthesouthern rocksdistributedintotwomajornappescomplexes.Theycrop Maghrebian Tethys margin was involved in subduction. out in Lesser Kabylie (Bouillin, 1979; Bouillin and Perret, The metamorphic rocks are preserved in the so-called 1982; Caby and Hammor, 1992; Mahdjoub et al., 1997), “Massifs Externes à schistosité” of the French authors Greater Kabylie (Saadallah and Caby, 1996) and Internal Rif (hereafter called External Metamorphic Massifs [EMM]), (reviewinMichardetal.,2006).Theuppernappecomplexis strung out over Eastern Rif and Western Tell (Fig. 2); poorly or non-metamorphic, only recording Variscan events. (cid:1) the presence of wide Miocene basins associated with the However, close to the basal contact with the lower nappe EMManddevelopedontopoftheorogenicsysteminthe complex an Early Miocene metamorphic event widely Rif and western Tell (Fig. 2). Among these basins, the overprinting also the lower nappe can be recognized (see Chelif Basin occupies a large part of the western Tell in Chalouan and Michard, 1990; Negro et al., 2006 for the Rif; Algeria (Neurdin-Trescartes, 1992; Perrodon, 1957). Saadallah and Caby, 1996 for the Lesser Kabylie; among othersCabyetal.,2001;Fernandezetal.,2016fortheEdough Toaddressthesetopics,wewillfirstexaminethestructure Massif). In contrast, the lower nappe (internal Rif: Sebtides; and geometry of the Tell-Rif system, emphasizing its non- Greater Kabylie: Lower Unit; Lower Kabylie: Beni Ferguen cylindrical character. Then, we will establish new and/or nappe) shows a general higher grade and a clear polyphased revisedfactsexplainingthechangesinthelateralorganization history. It is separated from the upper nappe through an of the orogenic system. On this basis, we will propose an extensionalshearzone.Thislowernappestillrecordsremnants updated set of palaeogeographical maps for the Cenozoic oftheVariscanevents(e.g.Fernandezetal.,2016;Mahdjoub evolution of the West Mediterranean. Key geodynamics et al., 1997; Montel et al., 2000; Peucat and Bossière, 1981; consequencesofourreviewwillbediscussedattheendofthis SaadallahandCaby,1996;Sánchez-Gómezetal.,1999;Zeck, contribution. 1999).However,itismainlycharacterizedbythesignatureof theAlpineevents,rangingfromHP-LTfortheearliestevents 2 Geological setting (cid:1) overall geometry of (Bruguier et al., 2017; Caby et al., 2014; Mahdjoub et al., 1997) to HT-LP for the most recent ones during Early to the Tell-Rif MiddleMiocene(Fernandezetal.,2016;Michardetal.,2006; Plattetal.,2013;Rossettietal.,2010withreferencestherein). TheTellisalinearmountainbeltstrikingE-W.Bycontrast, TheEdoughmassifpresentsapeculiarcase.Ithaseitherbeen animportantcurvatureexistsintheRif,whichswingsfromE- interpretedasanexternaloraninternalmassif(Bruguieretal., Win the eastern Rif to N-S in the western Rif (Fig. 1). This 2017; Caby et al., 2001; Caby et al., 2014; Hilly, 1962; featureisthesouthernbranchofthe“GibraltarArc”or“Betic- Michard et al., 2006; Vila, 1970). This difficulty stems from Rif Arc” (Durand-Delga and Fontboté, 1980), which extends thepoorlydefinedcontactbetweentheexternalzonesandthe northwardintheBeticswhereanother90°apparentclockwise Edough massif. For Vila (1970), the Edough massif shows a Page5 of35 R.Leprêtre et al.: BSGF2018, 189,10 MOROCCANMESORIF (Samaka et al.,KETAMAFLYSCHALBORAN BASINPRERIF (seismic-based)MESETA1997 & seismic-based)UNITUNIT(Do Couto et al., 2016)Autochtonous/Atlassic unitsNorth Africa margin(A)SNNeogeneLanghianPliocene-Quaternary(L. Oligo-Torton.)Jurassic(LK margin-Arab, 2016)00Alboran BasinMessinian (upper«Late Cret.»(a)(a) L. MioceneTriassic11unit)(b)(Aptian/Albian-(b) E. MioceneMaastrichtian)22Messinian saltOceanic crustEarly Cret./ in the33Rif : Early Cret. to BasementLate Miocene (up20 kmPaleogene44to Messinian base)5566AlKaPeCa basement/Tell units TWT (s)TWT (s)NumidianOlistrostomesPliocene-Quaternarynappe «Oligo-miocene«Oligo-mioceneLate Miocenekabyle»oranais»ALGERIAN PASSIVE MARGINDAHRA MASSIFTELL BELT & MIOCENETellian allochton(Delteil, 1974)CHELIFF BASIN (seismic-based)Early Miocene (up(a)MIOCENE FOREDEEP(a) Paleogene (Kassebto Langhian)(b)(Mauret./Massyl.)COTOCEANIC CRUST (?)in Tunisia)(b) Upp. Cret.(B)NNWSSENeogeneKetama magmatismcrustKabylia basement 00MetamorphicKetama unitbasement of the EMM& Tell equivalent11223344556620 km7788TWT (s)TWT (s) ATLASICLESSER KABYLIETELLALGERIAN MARGIN (Arab, 2016)FORELAND(Bouillin, 1979 & seismic-based)(seismic-based) OCEANIC CRUST (?)COT(C)NNWSSE000111222333??444555????666??7TWT (s)20 kmTWT (s)20 km8TWT (s)?? NUMIDIAN NAPPEKASSEB & FRONTAL IMBRICATIONSATLASICTUNISIAN MARGIN (Tricart et al., 1994)(seismic-based)(Rouvier, 1977 & seismic-based)FORELAND(D)NNWSSE 0001112223334445556620 km6 TWT (s)TWT (s)TWT (s) flFig.3.Cross-sectionsoftheTell-Rifsystem.Sectionswerebuiltusingsurfacegeology,wellsandpropertyreectionseismicdata.Fromwesttoeast:(a)easternRifbeltsectioncuttingthroughtheFlyschsunit,theKetamaunit,intrachainNeogenebasins(Taounate)andassociatedJurassicunits,andTsoulnappeontopoftheLateMioceneforedeep.MainmapreferenceisfiSuter(1980a,1980b)completedbyourteameldwork;(b)WesternAlgerianTellsection,fromtheoffshore,theDahraMassif,MioceneChelifBasin,andTelliannappesrestingontheearlyMioceneforedeep.MajormapreferencesarewithintheworksbyDelteil(1974),Fenet(1975),Polvêche(1960)andThomas,(1985);(c)EasternAlgerianTellsection,fromtheoffshorethroughtheLesserKabylie,Flyschsunit,theTelliannappes,andtheAtlasdomain.MainmapreferencesarewithintheworkbyBouillin(1979)andVila(1978,1980);(d)TunisianTellsection,fromtheoffshorethroughtheNumidiannappe,theimbricatedfrontalunits,theMedjerdasaltarea,theAtlasdomain.PrincipalmapreferenceisthemapbyRouvier(1977)fortheTunisianTell. Page6 of35 R.Leprêtre et al.: BSGF2018, 189,10 metamorphic cover belonging to the South Tethys margin. Kabylie-like terranes are continuous from Eastern Tunisia to Caby et al. (2001) demonstrated that this contact is not a SicilyandsouthernApennines(Auzendeetal.,1974;Bouillin, stratigraphical one but tectonic, still approving the external 1986; Bouillin et al., 1999; Catalano, 1987; Catalano et al., nature of the Edough Massif. They considered it to be an 1985; Compagnoni et al., 1989; Mascle et al., 2004; Tricart African metamorphic core complex, developed after the et al., 1994; Zitellini et al., 1989). Also, the Flyschs domain, emplacement of the Tellian nappes (and following them, notably the so-called Numidian flysch, develops widely in among others, Caby et al., 2014; Fernandez et al., 2016; Eastern Algeria and Tunisia. Bruguier et al., 2017). Following Michard et al. (2006) on the basis of metamorphic data and Paleozoic remnants within the massif, it is considered as belonging to the 2.2 The external domains internal zones rather than the external ones. The recent geochemical and Oligocene-Miocene dating results also The external domains, representing the former African convergemorewithaninternalorigin(Bruguieretal.,2017; paleomargin,aredescribedasapileofthrust-sheetsrestingon Fernandez et al., 2016). top of a Miocene foredeep in which allochthonous blocks Sandwiched between AlKaPeCa and the external domain (olistostromes) are included (e.g. Caire, 1957; Vidal, 1971). (Figs.2and3),theFlyschsdomainisconsensuallyviewedas This foreland basin, well developed at the front of the Rif theformercoveroftheMaghrebianTethysandpartiallyofthe (Gharb Basin) and in western and central Algeria, becomes East Ligurian Tethys (i.e. the “Bassin des Flyschs” of the narrower in between (in the Gareb-Kebdana promontory Frenchauthors),separatingEuropeandIberiafromtheAfrican [HervouëtandDeLuca,1980])andevendisappearsineastern plate up to the Miocene (Bouillin et al., 1970; Durand-Delga AlgeriaandTunisia,inareaswheretheforelanditselfhasbeen and Fontboté, 1980; Guerrera and Martín-Martín, 2014 for a impacted by major inversion tectonics (Fig. 2). The foreland review). The flyschs are divided into two units, namely an basin, when it exists, rests unconformably on a more or less internal “Mauretanian” unit, whose stratigraphic age spans foldedanddeeplyerodedMesozoicsubstratum,namelyeither from Jurassic to Late Miocene, and an external “Massylian” theAtlasbeltorthe“Mesetas”(Fig.1).Itislocallyoverlainby unit including the so-called “Numidian Formation”, often thin thrust-sheets (few hundred meters to no more than detached from its substratum and dated as Late Oligocene to 1.5km), which constitute erosional outliers of the uppermost Early Miocene (Guerrera and Martín-Martín, 2014; Thomas Tell-Rifunitsbycontrasttolowerunitsinterpretedastectonic et al., 2010). The Massylian unit shows a progressive lateral windows. transition towards the external domains of the South Tethys The uppermost units, called here “higher Rif-Tell margin. nappes”, are rather homogeneous all along the Tell-Rif. In Contrary to the older parts of the flyschs, deposited in a general, they are detached along an Upper Cretaceous passive margin environment, the post-Eocene sedimentation décollementandcompriseatypicallithostratigraphiccolumn directly recorded the orogenic activity. The basin is fed by of deep-marine sediments from Upper Cretaceous up to immature turbiditic sandstones in theinternal parts (Guerrera LowerMiocenewithoutsignificantunconformity.IntheRif, et al., 2005) and ultramature sandstones from the African theycomprisetheAknoul,Tsoul,OuezzaneandPrerifnappes craton in its external part (Belayouni et al., 2013; Guerrera or units and correspond to the former cover of the Ketama- etal.,2012;GuerreraandMartín-Martín,2014;Thomasetal., Tanger unit belonging to the Intrarif zone (Suter, 1980a, 2010).ThequestionofwhetherornottheMaghrebianTethys 1980b). The Aknoul nappe crops out in the eastern Rif and wasflooredbyanoceanicsubstratumisstillopen.Maficand presents the most complete sedimentary pile from Lower mantle rock remnants can be found along with the Jurassic CretaceoustoMiocene.TheTsoulnappe(Leblanc,1979)and strata of the Mauretanian flyschs (Durand-Delga et al., 2000; Ouezzane nappes (Durand Delga et al., 1962; Hottinger and Gélard,1979;GuerreraandMartín-Martín,2014)buttheyare Suter, 1962) are twin-units detached along a décollement in very scarce. Durand-Delga et al. (2000) proposed that a the uppermost Cretaceous. In western Algeria, they find an probable rifted and hyper-extended continental crust only equivalent in the so-called “Senonian”, “Albo-cenomanian”, partiallyoceanizedcouldhaveflooredtheMaghrebianTethys “Chouala” and “Oligo-Miocene” nappes of the Oran area without havinggivenrise toa trueoceanic lithosphere. More (Delteil,1974;Fenet,1975;Guardia,1975;Polvêche,1960). dataaboutthemaficandmantlerockremnantsintheKabylies In central Algeria, these units correspond to the complexes isstillrequiredtobringcrucialargumentsaboutthenatureof “B” and “C” (Caire, 1957; Mattauer, 1958), complex “B” the Maghrebian Tethys. being more or less equivalent to the Aknoul nappe and In map view, the Flyschs and AlKaPeCa domains are complex “C” of Ouezzane-Tsoul nappe. In Eastern Algeria discontinuous.Tothewest,theydisappearonshorebetweenAl andTunisia,aMiocenefrontalbasinonlyscarcelyunderlines Hoceima(CentralRif)andMostaganem(westernTell)(Figs.2 the limit between the Tell and the Atlas. The higher nappes and 3). In this area, a problem arises due to the apparent (KassebunitsinTunisia,Rouvier,[1977])correspondmostly disruption of these domains corresponding to the offshore- to tectonic imbrications resting directly over the Lower onshore limit (Fig. 3). Offshore studies by Domzig et al. Cretaceousrocksoftheforeland(Vila,1980).Inthiscase,the (2006)showthattheinternalzonesandtheflyschsextendupto sole-thrust of the nappes is a major Upper Cretaceous some distance offshore (Fig. 2) but the major part of this décollement level allowing the complete decoupling of the disruptionisoftectonicorigin,duetothepost-EarlyMiocene upper part of the sedimentary pile. motions of the westernmost part of the AlKaPeCa domain Below and/or laterally, the lower Tell-Rif units are (mostly the Alboran microdomain). Interpretation of this exposed. They occur in three different structural settings, i. disruption is a major issue. To the east, on the contrary, the e., from outer to inner zones: Page7 of35 R.Leprêtre et al.: BSGF2018, 189,10 RIF TELL AGES Eastern Rif Present Pliocène 5.3 Ma Messinian 7.25 Ma Tortonian ? ? 11511.3.96.741 MMMaaa SLearrnagvhailalinan Alboran westward drifting ? Burdigalian 20.43 Ma Tellian allochthon Nature of the Neogene Basins on top of the Tellian allochthon Top unconf. Miocene Foredeep Late Tortonian ? -Messinian unconf. Basal unconf. detachment controlled unknown nature Fig.4.TimetablefortheNeogeneprogressionofdeformationalongNorthwestAlgeriaandNorthMorocco.Whenknown,thetectonicregime duringthebasinemplacementisspecified.Thereferencesfortheforedeepageare:(1)Caire(1957),Kieken(1975),Vila(1980)andCourme- Rault(1984)fortheBiban;(2)Mattauer(1958),Polvêche(1960),Lepvrier(1970)andRoureetal.(2006)fortheOuarsenis;(3)Delteil(1974) andRoureetal.(2006)fortheChelif/MinaMts;(4)Fenet(1975),Thomas(1985)andHassani(1987)fortheTessala/EastOran;(5)Guardia (1975),Guardia andFenet (1987),andGuardia (1990) forthe BeniSnassen/West Oran;(6) Septfontaine (1983)forthe eastern Rif. (cid:1) in the most external zones, they constitute tectonic Negroetal.,2007, 2008). They are made up of a stack of windowscorrespondingtolateculminationsoftheAfrican tectonic slices with Paleozoic rocks exhibiting HP-LT foreland piercing the core of late anticlines refolding the metamorphictype(7–9kbarand330–430°C;Negroetal., over-lying nappes. This is typically the case from west to 2007)atthetopofthesystem.TheorganizationoftheOran eastforthe“internalPrerif”,the“externalMesorif”(Suter, Massif roughly mimics the Temsamane Massif with 1980a, 1980b) and for the tectonic windows of the increasing metamorphic conditions toward the NW Ouarsenis (Mattauer, 1958) and Biban (Caire, 1957) showing the highest grade in the highest Paleozoic slices Massifs. A similar configuration is observed more to the (Fenet, 1975; Guardia, 1975). In the Temsamane Massif, eastintheConstantinois(Vila,1980),inTunisia(Rouvier, the HP-LT metamorphism is older than 23Ma (40Ar/39Ar 1977),aswellasinproductivestructuresforoilandgasin on white micas: Negro et al., 2008) in agreement with Sicily and Southern Apennines (Casero, 2004 and previousagespublishedbyMoniéetal.(1984)(40Ar/39Ar references therein), with the following particularities: in onwhitemicas).Jabaloy-Sánchezetal.(2015)(40Ar/39Ar the Constantinois, there areno Miocenedeposits between on white micas and amphiboles) retain a Late Oligocene- theautochthonousandallochthonousdomains;bycontrast, EarlyMioceneageforthepeakmetamorphicevent,butan inItalyPliocenedepositshavebeenpreservedattachedto older age (Late Eocene) remains possible. The EMM thelowerplate(Caseroetal.,1991).Thesedifferencesare disappearwestoftheNekorfaultintheRifandeastofthe due to the diachronism of the main overthrusting episode GreaterKabylieintheTell(Fig.2).Itisnotyetestablished across the Maghrebian-Apenninic orogen. As indicated whethertheseunitsareburiedatdepthbelowmoreinternal above, the sole-thrust of the “higher Rif-Tell nappes” unitsorifthisabsenceisduetomajortransitionzonesthat remains a décollement (and not strictly speaking a thrust- would separate significantly different tectonic domains; fault) in this case, with only a lateral displacement of (cid:1) north of the EMM, the “northernmost Rif-Tell units” are younger units over older ones, without any real tectonic croppingout.Theycorrespondroughlytothemid-Tellian duplication (older over younger rocks), except near the andpartlythehigh-TellianunitsofWildi(1983).Fromwest tectonic fronts where the nappes can thrust over or be to east, they comprise: theKetama-Tanger unit, the Dahra intermingled within young Miocene sediments; unit between Oran and Alger and, finally, the Babor unit (cid:1) more to the north, units with significantly stronger between the Greater and Lesser Kabylie (Leikine, 1971; deformation than the “higher Rif-Tell nappes” and the Obert, 1981). In general, these units comprise Triassic to above-mentioned tectonic windows are exposed in the Lower Cretaceous sedimentary rocks involved in large easternRifandwesternTell(Figs.2and3).Theseso-called recumbent folds and separatedintosub-unitsbyimportant External Metamorphic Massifs (EMM) comprise the thrust-faults.Importantly,thesemassifsaretectonicallyun- Temsamane Massif (Andrieux, 1971; Frizon de Lamotte roofedandtheirformerUpperCretaceoustoCenozoiccover and Leikine, 1985, 1987) in the Eastern Rif and the Oran makesupthecurrent“higherRif-Tellnappes”. (Ciszak, 1993; Fenet, 1975; Guardia, 1975), Chelif (Lepvrier, 1978) and Blida (Bles, 1971) massifs in the 3 Inputs for a revised Mesozoic-Cenozoic WesternandCentralTell.ThebestexposuresoftheEMM scenario are located in the Temsamane Massif (Booth-Rea et al., 2012; FrizondeLamotteandLeikine,1985,1987;Frizon Allthefeatures presented abovemustbeexplained either de Lamotte et al., 1991; Jabaloy-Sánchez et al., 2015; bythestructuralinheritance,i.e.theinitialconfigurationofthe Page8 of35 R.Leprêtre et al.: BSGF2018, 189,10 margin,orbytheprocessesactiveduringtheinversionofthe of accretion and separation between Europe and Apulia. margin. Lateral displacements, i.e. parallel to the margin, are EquivalentagesforoceanicaccretioncharacterizetheLigurian veryimportantduringthetwomainstagesofthegeodynamic Tethys (Puga et al., 2011; Tortorici et al., 2009). Following evolution. We will examine them successively. different authors (Andrieux, 1971; Carminati et al., 2012; Doglionietal.,1997;Guerreraetal.,1993;Handyetal.,2010; Pugaetal.,2011;Vitale-Brovaroneetal.,2013),itispertinent 3.1 Oceanization steps in the Tethys realm todistinguishtwobranchesintheLigurianoceanicrealmwith In all the recent kinematic and palaeogeographic restora- theinterveningAlKaPeCacontinentaldomain(Fig.5A).The tions(Dercourtetal.,2000;Handyetal.,2010;Schettinoand western branch has receiveddifferentnames in theliterature: Turco, 2009; Sibuet et al., 2012, Nirrengarten et al., 2018; West Ligurian ocean (Handy et al., 2010), Penninic ocean Biari et al., 2017), Iberia was located far east of its present (Vitale-Brovarone et al., 2013) and Betic ocean (Puga et al., position relatively to Africa at the beginning of the Jurassic 2011).WewillkeepthetermWestLigurianTethys(WLT)to (Fig. 5A). So, at first order, the Maghrebian Tethys is denominate this oceanic domain. interpreted by the authors as a transform oceanic sea way In between the Central Atlantic and the Ligurian Tethys, connecting the Central Atlantic and the Ligurian (Alpine) theIberianandNorth-AfricanbasinspresentasimilarTriassic Tethys. This corridor allowed the left lateral movement of toMiddleJurassicevolution.Theydevelopedfirstlyduringthe Africa relatively to Iberia during the Jurassic and Lower Upper Triassic at the same time as the rifting in Central Cretaceous (Fig. 5). Atlantic(Leleuetal.,2016;Olsen,1997;Withjacketal.,1998 In detail, the evolution is more complex. Geological data and references therein) and in the Alpine domain (Bertotti fromIberiaandAfricashowasetofNEtoENEtrending“en etal.,1993).Then,whereasslowoceanicaccretionormantle echelon”Mesozoicbasins,whichweremoreorlesssubjectto exhumation began in the Central Atlantic (Labails, 2007; tectonic inversion during the Cenozoic. These basins are: the Sibuet et al., 2012), they recorded a new rifting phase in the Algarve (Ramos et al., 2016; 2017a, 2017b) and Subbetic Lower Jurassic. This second rifting event lasted until the late (García-Hernández et al., 1989; Vera, 2001) basins on the BajocianintheRif(Favreetal.,1991)andintheMiddleAtlas IberiansideandtheKhemisset-Rif(Favre,1995;Favreetal., (Sanietal.,2000;Zizi,1996a,1996b).IntheTell,seismiclines 1991), Middle-Atlas, High-Atlas, Sahara-Atlas and Tunisia- published by Bracène and Frizon de Lamotte (2002) suggest Atlas basins on the African side (Frizon de Lamotte et al., that the rifting was still active during the lower part of the 2000, 2009 and references therein; Fig. 5A). All of them are Dogger. In southern Iberia, the timing is less clear due to a slightly oblique to the Atlantic and Alpine Tethys ENE trend riftingrevivalcharacterizingtheIberianPlateduringtheLate butalsototheE-Wconnection(i.e.theso-calledMaghrebian Jurassic-Lower Cretaceous (e.g. in the Algarve Basin: Rey, Tethys)betweenthesetwooceanicdomains.Itisinterestingto 2009andreferencestherein;intheBetics:[Vera,1988,2001]). try to understand the geometrical and chronological relation- Anyhow,wecanpostulatethatattheendoftheJurassicrifting ships between the intracontinental rift basins and the oceanic theNorthAfricanbasins(Rif,MiddleAtlas,SaharaAtlas)and domains. An interesting comparison comes to mind with the their Iberian counterparts (Algarve, Cadix, Subbetic) were Aden Gulf opening reworking obliquely former Jurassic- already face-to-face (e.g. for a recent reference, Nirrengarten Cretaceous basins (d’Acremont et al., 2005). Another likely et al., 2018). The development of an E-W transform zone similar geological setting might be found in the Gulf of connectingtheAlpineTethystotheCentralAtlanticoccurred California where the ongoing right-lateral displacement just after. between the Pacific and the North America plates gave birth Given the kinematics of the Central Atlantic (Labails, to pull-apart basins. There, the crust was stretched to various 2007; Sibuet et al., 2012), it is likely that a “pure” transform extents.TheSaltonSeaBasin,locatedoncontinentalcrust,is movement lasted until 155Ma (Tithonian). Then, a net located along the San Adreas fault and is showing extreme decrease of the spreading rates (down to 2.6cm.yr(cid:1)1) thinning, though being bound by continental crust of normal occurred, coeval to a change in the plate kinematics. The thicknesses (Han et al., 2016 and references therein). This net result was an increase of the distance between Iberia and setting where only portions of the transform zone shows Africa. From a chronological point of view, this scenario is extreme crustal thinning might prefigure the Maghrebian consistent with the formation of the Ketama-Tanger oceanic Tethys before the left-lateral motion of Africa after the domainattheendofJurassictimes.Thus,thisbasinfilledwith Bajocian (van Wijk et al., 2017). flyschs outcropping in the Ketama unit simply appears as an ForthetimingoftheCentralAtlanticopening,wekeepthe appendix belonging to the Flyschs Basin itself. It is worth scenario proposed by Labails et al. (2010) and subsequently noting that a similar timing is also recognized for mantle modified by Sibuet et al. (2012), Klingelhoefer et al. (2016) exhumation along the south Iberian margin in the Gorringe and Biari et al. (2017). For Labails et al. (2010), the first Bankarea(Girardeauetal.,1998;Jiménez-Muntetal.,2010). oceanic crust appears at 195Ma (Sinemurian). However, Such a kinematic scenario could explain why mantle during c.a. 30Ma, the sea floor spreading was very slow exhumationandonsetofoceaniccrustaccretionoccurredlater (0.8cm/yr). By 165Ma (base Callovian), an acceleration is intheMaghrebianTethysthaninthemainAtlanticdomainand recorded up to spreading rates as high as c.a. 5cm/yr. For possibly later than in the Ligurian domain. The left-lateral Sibuetetal.(2012),mantleexhumationoccurredbetween190 movement of Africa associated with little divergence lasted and 177Ma followed by a ridge jump and a new oceanic during the whole Early Cretaceous and the beginning of the accretion since 177Ma (top Toarcian). In the Alpine Tethys, Upper Cretaceous, until the onset of the Africa-Eurasia ManatschalandMüntener(2009)propose166Mafortheonset convergence at 84Ma (Santonian). Page9 of35 R.Leprêtre et al.: BSGF2018, 189,10 A Toarcian-Aalenian WLT ELT WTeestth-Eyas sotp Leignuinrgia:n IM 150-185 Ma (Manatschal & Muntener, 2009; Puga et al., 2011) Central Atlantic opening: (Sahabi et a1l.,7 2500-41; 9La5b aMilsa et al., 2010) GoB GqB BB tPraonsts-f1o7rm0 M maotion CP RB PH TA Outer ramp & deep basins MA SA Shallow CA platforms & land B Tithonian-Berriasian N ?? PB N ? A a GoB GqB SbB SbB W. LIGUTREITHYS?? AlKaPeC MAGHREBIAN TETHYS CENTRAL ChU ATLANTIC OB OCEAN Oceanic domain/transitional crust RB Shallow platform Exhumed mantle PH & lands Passive margin extended domains Main normal rifting faults From Early to MA 200 km Minor transverse normal faults Late Jurassic Fig.5.PaleogeographicalreconstructionsfortheEarly-MiddleJurassicandtheendoftheLateJurassic.(a)Early-MiddleJurassic(Toarcian- Aalenian) wide-scale paleogeographical reconstruction. The well-established rifted domains are the Central Atlantic Ocean and the East Ligurian Tethys. In between, generally NE-SWoblique basins are more or less opened, from intraplate rift basins like the Atlas basins to embryonicoceanicdomainsliketheRifBasin,ortheBeticBasinwhereanoceanicdomainwaslikelypreserved.Themapandagesofbreak-up aremostlybasedonAïtOuali(1991),Dercourtetal.(2000),Favre(1992),Fedan(1988),Handyetal.(2010),Labailsetal.(2010),Lombardo etal.(2002),ManatschalandMüntener(2009),Pugaetal.(2011),Ramosetal.(2017b),Sahabietal.(2004),Sallarèsetal.(2013),Schaltegger etal.(2002),Soussi(2000)andthereferences.(b)FocusonthewesterntipoftheMaghrebianTethysbytheendoftheLateJurassic,afterthe east-southeastward drift of Africa since the Bajocian. This sketch illustrates the transition from extended and hyper-extended domains to exhumedmantleand/oroceaniccrust(maybetransitionalcrustforthewholeMaghrebianTethys).ThereconstructionisbasedonDercourtetal. (2000), Favre et al. (1991), Ramos et al. (2017b), and Vera (2001). The Rifian Basin, “Pays des Horsts” of the French authors (Northeast Morocco) and Chouala unit is our re-interpretation in terms of paleogeography of the field data presented in Ciszak (1993), Fenet (1975), Guardia(1975),andMichardetal.(1992,2007).AB:AlgarveBasin;BB:BeticsBasin;CA:CentralHighAtlas;ChU:ChoualaUnit;CP: CsontantinePlatform;ELT:EastLigurianBasin;GB:GorringeBank;IM:IberianMassif;MA:MiddleAtlas;OB:OranBasin;PB:Prebetics; PH: “Pays desHorsts”; RB: RifianBasin; SA: Sahara Atlas;SbB:SubBetics; TA: Tunisian Atlas;WLT:West Ligurian Basin. Page10of 35