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O n th e t ec t oni c origi n o f Iberia n t opog r ap h y A .M . Casas-Sainz a , ? , G . d e Vicen t e b a Departament o d e Ciencia s d e l a Tierr a , Unive r sida d d e Za r agoza , Spain b Grup o d e T ectonofísic a Aplicad a UCM . F .C . Geológicas , Uni v ersida d Complutens e d e Madrid , Spain abstrac t articl e i nf o Articl e histor y : R ecei v e d 2 8 Januar y 2 0 08 Acce p te d 2 6 Januar y 2 0 09 A v a ilabl e onlin e xxxx K eywords: Iberia Planatio n surface Landscape Meseta Crusta l thickening T ectonics Th e present-d a y t opo g rap h y o f th e Iberia n peninsul a ca n b e considere d a s th e resul t o f th e Mesozoic – Cenozoic tec t oni c evolutio n o f th e Iberia n plat e (includin g rif t in g an d basi n formatio n durin g th e Mesozoi c and compressio n an d mountai n buildin g processe s a t th e border s an d inne r par t o f th e plate , duri n g th e T y , follo w e d b y Neoge n e ri f tin g o n th e Mediter r anea n side ) an d surfac e processe s actin g duri n g th e Quaternar y . Th e northern-centra l par t o f Iberi a (correspondin g t o th e geologica l unit s o f th e Duer o Basin , th e Iber i a n Chain, an d th e Centra l System ) sho w s a mea n ele v atio n clos e t o on e thousan d meter s abo v e se a leve l i n a ve r age , some hundred s o f me t er s highe r tha n th e souther n hal f o f th e Iberia n plate . Thi s ele v ate d are a correspond s t o (i ) the to p o f sedimentatio n i n T ertiar y ter r estria l endorhei c sedimentar y basin s (Paleo g en e an d N e ogene ) and (ii ) planatio n surface s develope d o n Paleozoi c an d Mesozoi c ro c k s o f th e moun t ai n chain s surroundin g the T ertiar y sedimentar y basins . Bot h type s o f surface s ca n b e foun d i n continuit y alon g th e margin s o f som e f the T ertiar y basins . Th e Bougue r anomal y ma p o f th e Iberia n peninsul a indicate s negati v e anomalie s relate d to thickenin g o f th e continenta l crust . Correlation s o f ele v atio n t o crusta l thicknes s an d ele v atio n t o Bougu e r anomalie s indicat e tha t th e dieren t landscap e unit s withi n th e Iberia n plat e ca n b e ascribe d t o die r ent patterns : (1 ) Th e negati v e Bougu e r anomal y i n th e Iberia n plat e sho w s a roug h correlatio n wit h ele v ation , the mos t importan t gr a vit y anomalie s bein g linke d t o th e Iberia n Chain . (2 ) Mos t par t o f th e so-calle d Iberian Meset a i s linke d t o intermedia t e-ele v atio n area s wit h crusta l thickening ; thi s patter n ca n b e applie d t o th e two mai n intrapla t e mountai n chain s (Iberia n Chai n an d Centra l System ) (3 ) Th e mai n mountai n chain s (Pyrenees an d Betics ) sho w a direc t correlatio n betwee n crusta l thicknes s d ele v ation , wit h highe r ele v ation/crustal thicknes s rati o fo r th e Centra l Syste m vs . th e Betic s an d th e Pyrenees . Othe r feature s o f th e Iberia n topog r ap h y , namel y th e longitudina l pro  l e o f th e mai n ri v er s i n th e Iberia n peninsul a an d th e distributio n o f present-day endorhei c areas , ar e consisten t wit h th e T ertiar y tec t oni c evolutio n an d th e chang e fro m a n endorhei c t o an e x orhei c regim e durin g th e Lat e Neo g en e an d th e Quaternar y . Som e o f th e problem s inv o lvin g th e timin g and developmen t o f th e Iberia n Meset a ca n b e anal y se d consideri n g th e youn g es t refe r enc e level , constitute d by th e shallo w marin e U ppe r Cretaceou s limestones , tha t indicate s stron g dierence s induce d b y (i ) th e o v erall T ertiar y an d recen t compressio n i n th e Iberia n plate , responsibl e fo r dierence s i n ele v atio n o f th e refe r ence leve l o f mor e tha n6 k m betwee n th e mountai n chain s an d th e endorhei c basin s an d (ii ) th e eec t o f Neoge n e e xtensio n i n th e Mediter r anea n ma r gin , responsibl e fo r lo w erin g seve r a l thousand s o f meter s t o w ar d th e East an d upli f t o f rif t shoulders . A par t o f th e recen t upli f t withi n th e Iberia n plat e ca n b e attribute d o  sostati c upli f t i n zone s o f crusta l thickening. 1 . Int r oduction Th e Iberia n t opogr a p h y i s cha r act e rise d b y a hig h a v era g e ele v ation, t o gethe r wit h th e prese n c e o f high l y ele v a t ed  a t surface s dev e loped al l o v e r th e Iberia n peninsul a (th e so-calle d Iberia n Meseta) . These featu r e s de  n e a landscap e comple t el y diere n t fro m tha t o f wes t ern an d Medi t err a nea n Euro p e an d mo r e simila r t o ele v ate d ar e a s of norther n Afric a an d wes t er n Asi a ( Bi r ot , 1 959 ; Gladfel t e r , 1 9 7 1 ; Solé Sabarís , 1 9 78 , 1 983 ) . Hig h plain s i n Iberi a ca n b e classi  e d acco r ding t o thei r geo l ogica l natu r e : planatio n surface s de v elope d main l y on P alaeozoi c an d Mesozoi c ro c k s an d sedimentati o n surface s o f Neo g ene r ocks . Som e o f th e pro b lem s in v o l vin g th e timin g an d de v elopmen t of th e Iberia n Meset a ar e her e ana l y se d fro m th e g eologica l poin t o f vi e w , consider i n g th e r ol e o f th e o v e r al l T ertiar y an d r ecen t comp r essio n in th e Iberia n pla t e , th e eec t o f Ne o gen e e xt e nsio n i n th e Medi t err a nean margin th e te c toni c s o f th e Atl a nti c margi n an d th e conse q uence s of isostati c uplif t i n zone s o f crusta l thi c kening. T h e p a rti c u l a r t opo g r a p h y o f t h e Iberi a n p l a t e h a s l e d t o se v e r a l h y p o t h e s es , c o n s i de r i n g die re n t a g e s a n d t e c t o ni c o rigi n fo r th e upli f t , a n d a t t e m p t i n g t o e x p l a i n t h e h i g h l y ele v a t e d c e n t r a l a r e a (t h e s o - c a lle d M e s e t a ) o f t h e I b er i a n m i c r o c o n t i n e n t . T h e m a i n t o p o g r a p h i c f e a t u r e s o f t h e I b e r a n Meset a h a v e bee n p r ev i o us l y c h a r a c t e rise d f r o m g e o m o r - p h o lo g i c a l s tud i e s a n d l a n d s c a p e a n a l y s i s . T h e r e f o re , s o m e o f t h e m o d e l s ? Correspondin g autho r . T el. : +3 4 9 7 6 7 620 7 2 ; fax : +3 4 9 7 6 7 6 1 1 0 6 . E-mai l addresses: a c asa s @ u niza r . e s ( A . M . C a s as -S a in z ) , g d v @ g e o . uc m . e s (G . d e V ice n t e ) . Pleas e ci t e thi s articl e as : Casas-Sa i nz , A.M. , d e Vicen t e , G. , O n th e t ecto n i c origi n o f Iberia n t opogr a p h y , T ec t onop h ysic s (2 0 09) , doi: 1 0 . 1 0 1 6/j. tec t o.2 0 09. 0 1 .030 proposeddonotfocusonthecausesofuplift.Fourgroupsofhypothesescanbeestablished,accordingtotheproposedgeometryandoriginfortheIberianMeseta:(1)moreorlessuniformupliftoftheIberiancratonafterthecompleteerosionandformationofanIberianpeneplainattheendoftheTertiary(seeVázquezHoehne,1992andreferencestherein),(2)TiltingofthewholeplatetowardsthewestduringtheQuaternary, Fig.1.MainfeaturesofIberiangeology(A),NScross-section(B)showingthemaincompressionalgeologicalfeaturesandanEWcross-section(C)showingextensionalstructuresbetweentheAtlanticandMediterraneancontinentalmargins.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 thusconditioningthedrainagepatternofthewholePeninsula(seee.g.SoléSabarís,1983andreferencestherein).(3)Dome-shapedstructuresrelatedtoextensionintheMediterraneanmargin(SimónGómez,1984andreferencestherein).(4)Lithosphericfolding,causingthedifferentialupliftofdifferentpartsoftheIberianplateandconditioningthedistributionofbasinsandmountainschains,boundedbyfoldsandfaultsCloetinghetal.,2002;DeVicenteetal.,2007).Althoughhypothesesingroups(1)and(2)arerelatedtolandscapeanalysesanddonotproposeageological/geophysicalapproachtotheoriginofuplift,theymustbetakenintoaccountwhenconsideringanalysisofeventsresultingindistinctlandscapeevolutionandtheirrelativechronology.Theobjectivesofthispaperare:(i)todescribethedifferenttypesofsurfacesthatconstitutetheIberianMesetaandtoproposeaclassicationofsurfacesaccordingtothegeologicalbackground,(ii)toestablisharelationshipbetweencrustalthicknessandtopographyinthedifferentpartsoftheIberianplate,(iii)todenethegeologicalconstraintsneces-sarytointerprettheIberiantopographyintermsofTertiary/Quaternaryupliftand(iv)todiscusstheoriginofthehighlyelevatedIberiantopography,consideringtheformationofpeneplainsandthetimeinwhichtheyreachedtheirpresentposition.WenallyinterpretIberiantopographyintermsofPaleogenestructure,recentfracturing,exten-sionalmovements,andisostaticrebound.GeologicalandgeophysicalconstraintsareconfrontedwithexistingmodelsfortheIberianMeseta.2.GeologicalbackgroundThetopographyoftheIberianplateisstronglyconditionedbyplatetectonicevolutionduringtheMesozoicandtheTertiary(Casas-SainzandFaccenna,2001;CasasandCortés-Gracia,2002;Rosenbaumetal.,2002;Cloetinghetal.,2002;Tejeroetal.,2006;VergésandFernández,2006;DeVicenteetal.,2007).DuringMesozoictimes,widespreadriftingalongtheeastern,northernandwesternmarginsoftheIberianplate,andtheeastwardsdisplacementoftheIberianplatewithrespecttoEuropewerelinkedtotheopeningofthenorthernAtlanticandriftinginwesternEurope(Alvaroetal.,1978;Ziegler,1989,1990;SalasandCasas,1993).SincetheLateCretaceous,AfricanEuropeconvergenceandcollision(withlithosphericsubductionatthesouthernIberianmargin,BlancoandSpakman,1993)generatedthesubsequentupliftofthePyrenees,theIberianChain,theCentralSystem(Casas-SainzandFaccenna,2001),andotherminorrangesandslipfaultcorridors(DeVicenteandVegas,2009-thisissueThrustingandfoldingattheplatemarginsandwithintheIberianplatefavouredthedevelopmentofinternallydrainedbasinsborderingthemainmountainchains:theDuerobasininthenorthernhalfoftheplate,andthehighTagus(Madrid)basininitssouthernhalf(Fig.1Conversely,theAquitaineandGuadalquivirbasins,locatedoutsidethecentralpartoftheIberianplate(thepresent-dayIberianMeseta), Fig.2.SketchshowingthemainsedimentationandtectonicevolutioneventsacrossIberia(NSandEWtrends)duringtheTertiary.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 underwentamarine-continentalforelandbasinevolution(exorheic),becausetheywereopentotheAtlanticoceansincetheirearlyevolutionarystage.TheEbrobasinunderwentacompleteevolutionfromanexorheicforelandbasin(turbiditicandmolasse)duringtheEarlyOligocene,thenchangingtoendorheicduringtheLateOligoceneandtheMiocene(seee.g.Puigdefàbregas,1975).ThechangingofdrainagetypewasdrivenbytheupliftofthePyreneanthrustsystematthenorthernplateboundary.ExtensionduringtheMesozoicwascontrolledbyrifting(Fig.1),withseveralimportantriftsystems:(1)theBasqueCantabrianAquitainePyreneanriftingsystemtotheNorth,mainlycontrolledbyEWandSEnormalfaults(Sotoetal.,2008andreferencestherein),(2)theIberianBasin,inthecentral-easternpartoftheplate(Alvaroetal.,1978;SalasandCasas,1993;VanWeesetal.,1998),controlledbyNE(dominantintheEast,Antolínetal.,2008)andNWSE(dominantinthewest,Casasetal.,2000b;Liesaetal.,2000,2006)faulting,(3)theBeticbasins,inthesouth,separatedfromtheIberianplatebyNEfaults(Deweyetal.,1989;CrespoBlancetal.,1994;SanzdeGaldeano,1996;Gràciaetal.,2006),(4)theLusitanianbasin,controlledbyNnormalfaultsdelimitingthewesternIberianpassivemargin(Montenatetal.,1988;Pinheiroetal.,1996;Kullberg,2000).ThemainriftingstagesarePermianTriassicandEarlyCretaceousinage(Sopeñaetal.,1983;SalasandCasas,1993;VanWeesetal.,1998;DeVicente,2004).Theseperiodsareassociatedwiththemaximumthicknessofsyn-extensionaldepositswithintheplate,althoughimportantdepositionalareas,spe-ciallylinkedtothenorthernplatemarginalsodevelopedduringtheLateCretaceous(Martínez-PeñaandCasas-Sainz,2003;McClayetal.,TheconvergencebetweenAfricaIberiaandEuropefromtheLateCretaceousonwardsbroughtabouttheinversionofMesozoicextensionalbasinsandthick-skinbasementupliftzones(Fig.2).Inthecentral-easternpartoftheIberianpeninsula,theIberianBasinbecametheIberianChain(Alvaroetal.,1978).FoldingandthrustingofthePaleozoicbasementinareaswithnodepositionduringtheMesozoic(sedimentaryhighs)werealsouplifted,andsubsequentlyformed(i)theSpanish-PortugueseCentralSystem(DeVicenteetal.,2007andreferencestherein)andSouthofit(ii)theENEWSW-orientedmountainschainslocatedbetweentheCentralSystemandtheBeticChain(ToledoMountainsandSierraMorena,Cloetinghetal.,2002;DeVicente,2004).TheCatalonianCoastalRange,intheEast,consistsofbothbasementupliftsinareaswiththinsedimentarycoverandbasininversioninbasinalareas(GuimeràandAlvaro,1990;RocaandGuimerà,1992;Roca,1994).TheMesozoicbasinslocatedinthewesterncontinentalmarginwerealsoinvertedduringthisstage(seee.g.Alvesetal.,2003).InthenorthernIberianmargin,theupliftofthePyreneesconsistedofsouthward-directedbasementthrustingtogetherwiththeinversionoftheCretaceoussedimentarybasins(ñoz,1992;Teixell,1998).AconsequenceofthePyreneanupliftwastheclosingoftheDuero Fig.3.ComparisonbetweengeologyandtopographyintheIberianpeninsula,wherethedevelopmentofhighplainsindifferentkindsofrockscanbeseen.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 andEbrobasinsinitsnorthernedge,thusdeningasubstantialpartoftheIberianMeseta.Southwards,bothbasinswerealsoclosedbythecontemporaryupliftofthemaininteriorranges:TheIberianChainandtheCentralSystem.ExtensionalmovementsintheeasternandsoutherncoastsoftheIberianpeninsuladenedthepresent-dayshapeofthecontinentalplatformandtheoceanictroughs(RocaandGuimerà,1992;Balanyáetal.,1997).ExtensionduringtheLatePaleogeneandtheNeogeneformedtheValenciaTrough(continental-intermediatecrust,1992)andlaterontheAlboranSeaandtheAlgerianbasin(Fig.2),withoceaniccrust(Roca,1994;Sàbatetal.,1995;SanzdeGaldeano,1996;Balanyáetal.,1997Thesedimentaryllinghistoryofterrestrialbasinsshowssomecommonfeatures(Calvoetal.,1993;Calvo,2004)relatedwithtectonicactivityintheIberianplate:(1)TheearlierunitsweredepositedduringtheEocene,withthick,time-continuoussuccessions,dominatedbycontinentalfacieswithhighsedimentationrates.(2)TheDueroandTagusbasinsbegintoindividualisesincetheLateEocene,indicatingrstupliftoftheCentralSystem.(3)Incontrastwiththisearly,homogeneousstage,duringtheOligoceneEarlyMiocene,thesedi-llingofthebasinswascharacterisedbytheformationofdiscontinuitiesand/orsedimentarybreaks(fordenitionanduseofthesetermsseee.g.Muñoz-JiménezandCasas-Sainz,1998),thusningseveraltecto-sedimentaryunits.Althoughthenumberandthespecicageofeachoftheseunitschangefromonebasintoanother,indicatingdifferenttectonicactivityinthedifferentbasinborders,therelevantfactisthatthegreatestnumberofsedimentarybreakswasconcentratedduringthisperiodoftime,allowingforthewholeoftheseunitstobeinterpretedassyn-tectonic(DeVicenteandVegas,thisvolume).(4)ThenalstagesintheonshoregeologicalevolutionoftheIberianplatearecharacterisedbywidespreadlacustrinesedimen-tationintheendorheicbasins(Miocene,Anadónetal.,1990;Calvoetal.,1993;Alcaláetal.,1994;AnadónandMoissenet,1996;Alcaláetal.,1997;Alonso-ZarzaandCalvo,2000;Alcaláetal.,2000)andthebeginningofcaptureandexorheismintheDuero,EbroandTagusbasins(PlioceneandQuaternary,Martín-Serrano,1991;Gutiérrezetal.,1996;García-Castellanosetal.,2003;Babaultetal.,2006).Allu-vialdepositsweredepositedbytheuvialnetwork(Duero,Ebro,Tagusriversandtheirtributaries)installedontheancientinternally-drainedbasins(Gutiérrezetal.,1996Duringtheendorheicexorheictransition,paleo-karsticationpro-cessesanderosionoccurredintheUpperMiocenelimestonesCañaverasetal.,1996).ThisdenudationepisodewasshortlyinterruptedbyalluvialfansedimentationduringtheLateMiocenePliocene(formingtheRañadeposits)widespreadontheSpanishMeseta,im-mediatelybeforecongurationoftheQuaternaryuvialnetwork.3.Geomorphology3.1.AclassiforthehighplainsinIberiaAverageelevationoftheIberianpeninsulaisabout660m,cor-respondingtoa3700mfreeboardofthecontinentalcrustoverthesurroundingoceanicplains.Acleardistinctionoftopographycanbeestablishedbetweenthenorthernandsouthernhalvesoftheplate,bothseparatedbytheCentralSystem(Fig.3).ThenorthernhalfofIberiashowsanaverageelevationof800manditssouthernhalf500m(theBeticChain,forexample,showsameanelevationofabout700m,Fig.4).Theoverallhightopography,lowrelieflandscapeoftheIberianMesetaisdevelopedintheinnerpartoftheplate,ankedclearlyinthenorthbythePyreneesCantabrianmountains(Fig.3),andnotsoclearlyintheSouthbytheBeticChain.Bothmarginalrangesare Fig.4.TopographyoftheIberianpeninsulashowingthemaintraitsofitslandscape.Numbersindicatetheaverageelevationofitsdifferentsectors.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 thrustingovertheIberiancontinentalplate,whatmeansthatinbothsituationstheforelandtothemountainrangesisontheIberianside.TheIberianhightopographyconsistsmainlyofremnantsofhighplains,dissectedbythepresent-dayuvialnetwork.TheseremnantsofhighplainsarewidespreadinthenorthernhalfoftheIberianmicrocontinent,andnotsomuchinitssouthernhalf(Figs.3and5Fromthegeologicalpointofview,twomaintypesofhighplainscanbedistinguishedintheIberianpeninsula(Figs.3and5highplainscoincidingwithTertiarysedimentarybasins(Figs.3and5A),withhighestpreserveddepositsLateMiocenetoPlioceneinageandsubhorizontalbedding.Themainrepresentativesofthiskindofsurfaces(manyofthemerosionalintheirpresentform)areintheDueroBasin(includingtheAlmazanBasin),atelevationsbetween700and1200ma.s.l.,andintheEasternTagusBasin,atelevationsbetween500and1000ma.s.l.(GraciaPrietoetal.,1990;Mediavillaetal.,1996;GutiérrezElorzaandGracia,1997;Alcaláetal.,1997;Cortés,1999;García-Quintanaetal.,2004;Benito-CalvoandPérez-González,2007).IntheEbroBasinthiskindofsurfacesisrestrictedtomarginalareasnearthebasinmargins,sincemoststructuralsurfacesdevelopednearthecentralpartofthebasinarelowerthan500ma.s.l.andcannotbeconsideredashighplains.Otherstructuralsurfacescanreach800ma.s.l.inthebasincentrebutcorrespondtolevelsbelowthetopofNeogenesedimentationPérez-Rivarésetal.,2002,2004highplainsconsistingoferodedsegmentsofMesozoicandPalaeozoicrockswithplanationsurfaces(pediplains),developedonthemountainranges(fold-and-thrustsystemsandbasementuplifts)formedduringthePaleogeneEarlyMiocene(Figs.3and5B,D,E).Thistypeofsurfacesarespeciallywelldeveloped Fig.5.PhotographsshowingdifferentaspectsofplanationsurfacesintheIberianpeninsula.A.HighDuerobasin,withQuaternarydepositspartlycapturedbytheSilrivernetwork,owingtowardstheMiño.B.Planationsurface(pediplain)inthecentralpartoftheIberianChain.AresidualreliefofPalaeozoicrockscanbeseeninthebackground.C.Highplains(1200ma.s.l.)developedonMesozoicandTertiaryrocksintheIberianmeseta,asseenfromaresidualreliefofPalaeozoicrocks.Aresidualendorheicarea(smalllake)canbeseen.D.PlanationsurfacedevelopedonPaleozoicrocks,notcapturedyetbythepresent-dayuvialnetwork(IberianChain).E.Stronglydissectedplanationsurface(1000m.a.s.l.)inMesozoic(Triassic,Jurassic,Cretaceous)rocksintheIberianChain.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 throughouttheIberianChain(between1000and1600ma.s.l.),theCentralSystem(between900and1500m.a.s.l.),inmarginalareasofthePyreneesandtheCantabrianmountains(between1000and1300ma.s.l.),andnallyintheAtlanticmarginandtheGalicianMassif(between300and1700ma.s.l,althoughQuaternarysedimentationsurfacesareatloweraltitude).Inmountainchains,planationsurfacesarewellpreservedclosetotheirborderswiththeEbroandDuerobasins,andinsomeareasoftheCentralSystemandtheToledoMountains(RodríguezVidal,1983;SimónGómez,1983,1984;Moissenet,1985,1989;GraciaPrietoetal.,1990;VázquezHoehne,1992;GutiérrezElorzaandGracia,1997;VidalRomaníetal.,1998),andtheirgeometryincludesinsomeareassteppedlevelsaroundthehighestmassifsCasasandCortés-Gracia,2002).SteppedplanationsurfacesdevelopedinthenorthwesterncorneroftheIberianpeninsula(GalicianMassif,Fig.3)linkingthesummitlevelswithsealevel(astheresultofupliftand/orerosionalstepping,VidalRomaníetal.,1998)arethecounterpartoferosionsurfacesdevelopedontheendorheicfaceofthemountainchains.OntheAtlanticmarginthedifferentlevelsoferosionsurfacesarealignedinNSdirection,andhavebeeninterpretedastheresultofhorst-and-grabentectonicsinvolvingre-activationofNNESSWfaultslinkedtotheupliftoftheIberianMesetaduringtheNeogeneandQuaternaryDeBrumFerreira,1991Bothtypesofplanationsurfacesdescribedcanbeincontinuityatthesameelevationandareindistinguishableonlyfromtheirtopographicdetails(i.e.fromtopographicmaps,Fig.4,although,forexample,karsticationismorecommononerosionalsurfacesdevelopedonMesozoiclimestonesandstructuralreliefsormesasaretypicalofNeogenebasins).Thecoupledoriginofbothkindsofsurfacescanberelatedwithuplift/sedimentationhistoriesalongtheTertiarycompressionalbasinmarginsintheIberianpeninsulaGuimeràandGonzález,1998;CasasandCortés-Gracia,2002).Thiscanbeclearlydeducedfromsomeofthegeometrical/topographicalrelationshipsalongthebasinborders,forexamplebetweentheCastilianBranchoftheIberianChainandtheTagusbasin(Fig.6).InthissectionthesedimentationsurfaceatopoftheTagusbasincanbeprolongednorthwardstotheplanationsurfacesdevelopedonMesozoicrocksoftheIberianchain,reachingthetopographicEbro/DuerodivideintheAragonianBranch.Bothkindsofplanation/sedimentationsurfaceshavebeenstronglydissectedsincethestartoftheexorheicdrainage,especiallyintheEbroandwesternmostpartoftheTagusBasins(seeFigs.4and5A,E).Planationsurfacesmustbemappedbydetailedanalysisofcontourmaps,closelyspacedprolesandaerialphotographstoascertaintheircontinuityLidmar-Bergström1988,1996;Bonowetal.,2006).Correctlymappedtheycanbeusedforconclusionsonwarping,tiltingandfaulting(Lidmar-Bergström,1988;DeBrumFerreira,1991;Lidmar-Bergström,1996;CasasandCortés-Gracia,2002;Bonowetal.,2006).Thersttype(Neogenetopsedimentationsurfaces)canbereconstructedwhentheyoungestsedimentsarepartlypreserved,whatisthecaseintheheadsofthethreemainTertiarybasins(Ebro,Duero,andTagus),andtakingintoaccountthedipofbeds,usuallyshallowlydippingtowardthebasincentre.ErosionalvoidsintheEbro,DueroandTagusbasinscanbecalculatedaccordingtothe Fig.6.Topographic-geologicalcross-sectionthroughtheAragonianBranchandtheCastilianBranchoftheIberianChainandtheTagusbasin,showingtherelationshipbetweenthedepositionalandplanationsurfacesandtheiraveragediptowardthesouthwest.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 differencebetweenthepresent-dayelevationandthetopofsedimentationinthedifferentpartsofthebasins,andtheerosion/sedimentationbalance(Casasetal.,2000b;García-Castellanosetal.,20033.2.Sedimentationsurfaces:reconstructionanddissectionAlthoughatpresentmostofthealluvialplainoftheEbroRiverrunsbelow400ma.s.l.(seeFig.7),beforetheQuaternaryerosionalprocessestheEbroBasinwasatabout1100minelevation(inpresent-daycoordinates),limitedtotheEastbytheCatalonianCoastalRanges.SomeareasoftheDuerobasinrecordNeogenesedimentationatsimilarelevations,favouringtheinterpretationthatthedifferentTertiarybasinsinnorthSpainwereconnectedattheendoftheendorheicstage(Santistebanetal.,1996;Casasetal.,2000bConversely,incontrastwiththeEbroBasin,mostofthesedimentaryplainoftheDueroRiverrunsatpresentbetween700and1000ma.s.l.ErosionintheEbroBasinprogressedfromeasttowest(García-Castellanosetal.,2003),favouredbyregressiveerosionintotheNeogeneendorheicbasin(Babaultetal.,2006).Followingthisinterpretation,theDuerobasinismuchlesserodedthantheEbroBasin,ascanalsobeinterpretedfromtheriverproles(Fig.7).Itcouldbeconsideredasanearlierstageintheexhumationevolutionofthebasin,witherosionprogressingfromthewesttotheeast.ThiscouldalsoindicateadifferentintensityintheneotectonicactivitybetweentheeasternandwesternpartsofIberia.InthesouthernhalfoftheIberianpeninsulatheaverageele-vationislower(Fig.4),astheTagusBasincanbedividedintotwodifferentsectors,separatedbyathresholdattheconuencebetweentheCentralSystemandtheToledoMountains:(i)theeasternsectorcorrespondstoastronglysubsidingterrestrialbasin(MadridBasin)thatwasendorheicduringmostpartoftheCenozoicandwascapturedonlyattheendoftheMiocene,withatotalincisionofabout500m;(ii)thewesternsectorconsistsofseveralsmallerbasinsatlowerelevationslimiteddownstreambyridges,thatwereendorheicduringsomeperiodsoftheCenozoic(ProençaCunhaetal.,2005)andwereprobablyopentotheAtlanticbeforetheeasternpartofthebasinwas.BothpartsoftheTagusbasin(easternandwestern)wereonlyconnectedaftertheinstallationoftheQuaternaryuvialnetwork.SouthoftheTagusbasin,onlytheupperpartoftheGuadianaBasin(LaMancha)showsananaloguescenarioofhighplainslinkedtoendorheicbasinsatelevationsbetween600and700ma.s.l.(seeFig.43.3.ErosionalsurfacesFlatsurfacesaremorecommonlydevelopedonMesozoicrocks,mainlyJurassicandCretaceousmarinelimestones(Fig.5B,C,E),withmanyexo-karsticfeatures.Theseareusuallymorefrequenttheolderandhighertheplanationsurfaceis(CasasandCortés-Gracia,2002Planationsurfaceslinkedtoendorheicbasinsarearrangedinsteppedlevels(between2000and1000minelevation),withdifferent Fig.7.LongitudinalprolesofthemainriversoftheIberianpeninsula.Elevationplottedagainstlength(A)andagainstthenormalisedlength(B)toallowdirectcomparisonbetweenthedifferentrivers.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 degreesofdissectionbytheQuaternaryuvialnetwork.However,theirreconstructionandcorrelationisstillpossibleinsomeareasbymeansoftheelevationofthedifferentremnantsofplanationsurfacesRodríguezVidal,1983;SimónGómez,1983,1984;GutiérrezElorzaandGracia,1997;Graciaetal.,2001,2002;CasasandCortés-Gracia,2002).Onthesea-facingsideofthemountainstheelevationofplanationsurfacesisusuallylower,withrecognisedremnantsdowntoafewhundredmetersabovesea-level,allowingforthemovementoffaultstobereconstructed(DeBrumFerreira,1991;VidalRomaníetal.,1998PlanationsurfacesdevelopedonPalaeozoicmaterialsarenotsoregularassurfacescuttingacrosstheMesozoiclimestones,andusuallycoversmallerareas,inasimilarwaytothosedevelopedintheAxialZoneofthePyrenees(cf.Babaultetal.,2005).InmanyplacesalongtheIberianMeseta,Palaeozoicrocksformedresidualreliefzonesstandingoutonthepeneplains(Fig.5).However,theresistancetolinearerosionbyriversduringtheexorheicstagewasprobablylowerinthePaleozoicrocks,speciallyinfracturedzones,thanintheMesozoicrocks,favouringlinearincisionalongthemainVariscanstructuraltrends(NWSEintheeasternpartofnorthernIberia,seeFig.12,NESWintheDueroBasinandtheCentralSystem,Alvaroetal.,1978;Cortésetal.,20034.Constraintsonrockuplift4.1.Geologicalconstraints:elevationofgeologicalmarkersThemaximumupliftorsubsidenceofsurfacesorrocks(foradiscussionoftermssuchussurfaceuplift,upliftofrocksandexhumationwefollowheretheterminologyestablishedbyEnglandandMolnar,1990,seealsoDeBruijneandAndriessen,2002)canbeconstrainedbymeansofgeologicalmarkers,providedthatsuchfeatureshaveknownelevationattheirformationtimeandwereatinorigin.Inanycase,itmustbetakenintoaccountthattheaccuracyinthedetectionofsubsidence/upliftwillbelowerthantheoriginaltopographicirregularitiesofthechosensur-facecombinedwiththeuncertaintiesinthedeterminationofitsoriginalelevation.Bothplanationandsedimentationsurfacesmayttheseconditions.However,sinceplanationsurfacescanformatanyheightwithinamountainrange(asdemonstratedbyBabaultetal.,2005,2007),andtheycanbereworkedalonglongtimespansCasasandCortés-Gracia,2002),theiruseasupliftindicatorscanbeproblematical,eveniftheirage,inthecaseoftheIberianPeninsula,canberoughlyconstrainedbetweentheLateEoceneandthePliocene.SurfacesolderthantheNeogenecanofferagoodreference,especiallywhenasedimentarycoverofknownageisoverlyingthem.Themaindrawbackofancientsurfacesisthattheirpresent-daygeometryistheresultofcumulatedeventsandthatinterpretationmustbedonecarefullyinordertolterthetopographicchangesderivedfromrecentmovements.Inouropinion,twomaingeologicalmarkerscanbeusedtoconstrainthegeologicalhistoryofIberiantopography(Fig.8SincetheUpperCretaceousconsistsofshallowmarinelime-stones,widespreadthroughouttheIberianplate(andmuchofwesternEurope),thetopofthissedimentaryunitgivesareliableindicatorpredatingTertiarydeformation.Thedrawbacksforusingthissurfacearemainlyrelatedto(i)erosionofUpperCretaceouslevelsinmanyareasthatonlyallowforminimumvaluesforitselevation,andthereforeforuplifttobegivenfortheseareas,and(ii)thelongtimespanbetweentheLateCretaceousandtheQuaternary,thatonlyallowsforatime-limitframeforthevaluesgivenbyotherchronologicaltechniquestobeobtained,butnotforprecisingmovementsfrom60m.a.onwards.TheelevationofthetopofthePaleozoic.ThetopographyofthissurfaceistheresultoftheMesozoicextensionalmove-ments,theTertiarycompressionandtherecentmovements.Inspiteofitscomplexhistory,itselevationcangivesomecluestorejectmodelsnon-consistentwithitslong-wavelengthsundula-tions.Italsoallowsfordepictingdeformationalfeaturesinareas(westernpartofIberia)wheretheUpperCretaceousisdeeplyeroded.TheelevationofthetopofthePalaeozoicbasement(Fig.8ctsbasinevolutionduringtheMesozoic(overallloweringformWesttoEast),andcompressionalupliftofthemainchainsduringtheTertiary(seee.g.Sotoetal.,2006):linearEWtrendinthePyrenees,theCentralSystem,andtheBeticChain,NWSEtrendintheIberianChain,NESWtrendsintheCentralSystemandtheCatalonianCoastalRangeandNNESSWintheVilariçaleft-lateralFaultSystem.Themainlowsofthissurfacearelocatedinintra-platecontinentalbasins(Tagus,DueroandEbrobasins)whereitreachesmorethan4000mbelowsealevel(DeVicenteetal.,1996;Muñoz-JiménezandCasas-Sainz,1998;Casasetal.,2000b).Calcu-lationsconsideringlocalisostaticequilibrium(Casasetal.,2000bindicateacontributionofbothllingofintra-mountaintroughsboundedbyfoldsandthrustsandlocalisostaticcompensationduetothellingofthesetroughs.ElevationofthetopoftheUpperCretaceous(aatsurfaceatsealevelbeforetheTertiarycompressionalextensionalprocesses,Fig.8A)givesacluefortheuplift/subsidenceofalltheeasternpartofIberia,wherethissurfaceispreserved,orcanbereconstructedreliably.ThemaximumamountofupliftsinceLateCretaceoustimesisgivenbythissurface,whatcanhelptocontrastsomeofthehypothesesproposedfortheevolutionofeasternIberia.Inareaserodedbelowthislevel(topoftheUpperCretaceous),aminimumamountofupliftcanbeobtained,althoughinthewesternthirdoftheIberianpeninsulathepaleo-elevationofthebasementduringtheLateCretaceousisnotknownandthereforeupliftscalculatedbythismethodcanbeoverestimated.ThecontoursoftheUpperCretaceoussurfacearealsoagoodindicatoroftheerodedvolumeofrocksinthedifferentmountainranges.SomecrestsintheIberianChainareerodedupto1400mwhereastheaverageerosionabovethepresentdaytopographyinthischainis580m(CasasandCortés-Gracia,2002).InthemarginalareasoftheCentralSystemandtheCantabrianmountainsthegeometryoftheUpperCretaceouscanalsobereconstructed,butitspositionabovethepresent-dayoutcropsinthecentralpartofthesechainsismorespeculative,withminimumupliftvalueshigherthan2000m(see,e.g.,DeVicenteetal.,1996;Alonsoetal.,1996;AlonsoandPulgar,2004;DeVicenteetal.,2007).Althoughthiscanonlybeconsideredasaminimumvalue,takingintoaccountthethin-skinnedcompressionaldeformationintheseareas,theupperlimitforthetopoftheUpperCretaceousisprobablynotmuchbeyondthisgure(seeabove-topographyreconstructionsbyAlonsoetal.,1996;DeVicenteetal.,1996FromthereconstructionofthetopoftheUpperCretaceousbothinthemountainchainsandtheTertiarybasins,minimumtectonictopographiesof7000mforthebordersofbasinscanbeestablished,withatimespanfortheirformationextendingfromtheEocenetopresent-day.Thisimpliesastrongcomponentofcompressionaltectonicsinthepresent-daytopographythatshouldbetakenintoaccountwhenconsideringmodelsfortherecentevolutionoftheIberianplate.4.2.Geophysicaldata:crustalthicknessvs.topographicelevationCrustalthicknessintheIberianpeninsulacanbeconstrainedmainlyfromgravimetricdata(DeVicente,2004),althoughsomeseismicrefractionprolescanhelptoconstraingravimetricmodels(Zeyenetal.,A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 1985;Tesauroetal.,2007).Ingeneral,theBougueranomalyclearlynesthecontouroftheIberianmicrocontinent,withsharplydecreasingvaluestowardtheeastern,northernandwesterncoastallines(Fig.9Mezcuaetal.,1996;DeVicente,2004).Theabove-describedasymmetryintheelevationoftheIberianpeninsulaisalsoreectedintheBougueranomalymap(DeVicente,2004),withmoreimportantnegativeanomalies(exceptfortheBeticChain)inthenorthernpartoftheplate.Crustalthicknessmaximafollowmoreorlessthetrendsofthemainmountainchains(DeVicente,2004):(i)CantabrianMountainsandPyrenees,withcrustalrootsofmorethan45km,separatedfromeach Fig.8.A.ElevationofthetopoftheCretaceous(endofmarinesedimentationatthebeginningoftheTertiarycompressionalstage).B.ElevationofthetopofthebasementintheIberianpeninsula.DatafromJuncoAguado(1983)JuncoAguadoandCalvoSorando(1983)Jiménezetal.(1983)Ribaetal.(1983)Lanaja(1987)Casasetal.(2000b)Herreroetal.(2004)Sotoetal.(2006)A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 otherbylowercrustalthicknessbelowtheBasqueCantabrianmountains(resultingfromtheinversionoftheMesozoicBasqueCantabrianbasin),wherestrongextensionalmovementstookplaceduringtheCretaceousstretchingstage(seee.g.Pujalte,1982,1989;García-Mondéjaretal.,1996;Sotoetal.,2008).Towardthewest,thiscrustalthicknessmaximumdescribesanNW-facingarc-shapedtowardthenorthwesterncornerofIberia,adoptingthereaNNESSWtrendthatmimicstheVilariçaFaultSystem,withsimilarcrustalthicknesses;(ii)TheCentralSystem,withaNESWelongatedmaximum,morepronouncedintheEast,nearthemaximumthicknessofsedimentsinthehighTagusbasin(Madridbasin),andprogressivelydiminishingtowardtheWest,becomingunnoticeablenearthePortuguesecoastline;(iii)TheBougueranomalyintheIberianChainisnotsoclearlydened,probablybecauseofthepreviousextensionalhistoryofthismassifduringtheMesozoicthatproducedawideareawithextensionalde-formation,insteadofrectilineargrabens(Guimeràetal.,1996).TheIberianChain,togetherwiththeCentralSystem,denesacompactrectangle-shapedpositiveBougueranomalyinthenorthern-centralpartofIberia,betweenthenorthernplatemarginandtheTagusBasin.TheCatalonianCoastalRange,locatedtowardstheshoreline,doesnotshowawell-denedgravimetricanomaly,becauseofitsproximitytothepositiveareasoftheMediterraneanmarineplatform;(iv)theBeticChain,withastronganomalyparalleltothecoastlinecontinuestotheSouthwiththeimportantpositiveanomalycorrespondingtotheAlboranTroughand(v)themountainsegmentssouthoftheCentralSystem,wherethegravimetricanomalyisstronglyconditionedbyaSElineamentsouthoftheCentralSystem,coincidingwiththelimitbetweenareaswiththickMesozoiccoverandTertiarycompressionaldeformationconsistingofwell-denedthrustsandforelandbasinstotheNE(IberianChain,CentralSystem)andtheareawithoutMesozoiccoverandmoderatethick-skinbasementuplifts(ToledoMountains).Furthermore,thislineamentcanalsoberelatedtoaPliocenevolcanicarea(CamposdeCalatrava)anditrepresentsalimitforinstrumentalseismicityatpresent.SeveralmodelsregardingthehightopographyoftheIberianMesetahavebeendened,consideringbothextensionalandcompres-sionalorigins(see,e.g.SimónGómez,1983,1984,1986,1989;GutiérrezElorzaandGracia,1997;Gonzálezetal.,1998;Graciaetal.,2001,2002;CasasandCortés-Gracia,2002;Gutiérrezetal.,2008).Apossibilitytodistinguishbetweenthetwoend-membermodelsisthecorrelationbetweencrustalthicknessandtopographicelevation(Fig.10).Highcontinentalareaswithcrustalrootsareprobablyrelatedwiththicken-ingunderaconvergenceregime,whereaselevatedareasrelatedtocrustalthinningcanbelinkedtoextensionalprocesses(mainlyrifting).IntermediatemodelscanbeassociatedwithlithosphericfoldingCloetinghetal.,2006Therelationshipbetweentopographicelevationandcrustalthick-nessorBougueranomaly(Fig.10)allowsforthedifferentgeologicalareastobedifferentiatedaccordingtotheirgeophysicalsignature.IntheIberianpeninsula(Fig.10),elevatedzoneswithinthenorthernpartoftheplatecoincidewithareasofmaximumcrustalthicknessandadecrease(morenegative)intheBougueranomaly,especiallyintheCantabrianmountains,thePyrenees(westernzone)andtheCentralSystem,wherenoimportantextensionalmovementstookplaceduringMesozoictimes.Inthethreemainmountainranges(Pyrenees,BeticsandCentralSystem)thereisaroughexponentialrelationshipbetweenbothparameters,theCentralSystemshowinghigherelevationsforsimilarcrustalthicknessesthantheBetics(intermediaterelationship)andthePyrenees(minimumelevation/thicknessratio).TheIberianChainisalsocharacterisedbyathickcrust,withathickercrustinrelationtothetopographicelevationthanotherareasintheIberianmainland.ItisimportanttonotetherelativedisagreementexistingbetweenMohodepthandBougueranomalyfortheIberianChain.TheatareascorrespondingtotheIberianMeseta(DueroBasin,IberianChain)twithintheintermediateelevationandMohodepthbetween30and40kmzone,relativelywellindividualisedindiagramsshownin10A,B.Ingeneral,inalltheextensiveelevatedareas,exceptforthesouthwesternpartofIberia,thereisadirect Fig.9.BougueranomalymapoftheIberianpeninsula.ModiedfromDeVicente(2004)A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 correlationbetweenelevationandcrustalthickness,whichsupportsacompressional/isostaticoriginformostpartoftheupliftoftheIberian4.3.Theevolutionfromendorheismtoexorheism:geomorphologicalconstraintsLow-leveltopographyareaswithintheIberianplatearelinkedto(1)coastalplainsdelimitedbyOligoceneMiocenenormalfaults(Mediterraneancoast),incontinuitywiththeoffshoreplainsoftheValenciaTroughortheAlgerianbasin,orrelatedtotheAtlanticmargin(Atlanticcoast),(2)externallydrainedbasinsformedduringcompressionaldeformationoftheplate(namelytheforelandGua-dalquivirBasin,limitingthesouthernpartoftheIberianMeseta),(3)Tertiary,internally-drainedbasinscapturedbytheuvialnet-workduringtheMioceneorthePlio-Quaternary(García-Castellanosetal.,2003).SedimentationduringtheNeogenethroughouttheIberianmicrocontinent(Fig.9)wasofalluvial/lacustrinetype,withalluvialfanssourcedintheresidualreliefareasoftheerodedmountainchainssurroundingthebasins(Cantabrianmountains,Pyrenees,IberianChain,CentralSystem,seee.g.Casasetal.,2000bTheoccurrenceofendorheicbasinswithintheplateduringthisperiod(Fig.11)isaparticularfeatureofIberia.ThisconditionedlandscapedevelopmentintheIberianplateduringalltheTertiaryandtheQuaternary(e.g.Coneyetal.,1996)evolvingunderthefollowingconstraints: Fig.10.Bougueranomaly(A)anddepthtotheMoho(B)vs.topographicelevationindifferentgeologicalunitsoftheIberianpeninsula.Verticalscale:elevationinkm(AandB).Horizontalscale:mGal(A)andkm(B).A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 Becauseofthehighbaselevels(continuouslyrisingduringthellingofthebasins),endorheicdepositionpreservedthemassifsofPalaeozoicandMesozoicrocksfromdeeperosion.However,theabsoluteheightofbaselevelsduringthestageofformationofplanationsurfaceisnotknownandinformationonthisaspectcanonlybeobtainedfromgeologicalmarkers(i.e.,geometryoftheUpperCretaceousmarinelimestones)andmorphologicalfeaturesalongthewesternandeasterncoasts.Depositioninendorheicbasinscontributedtorelativelyhighdepositionrates,accommodationspaceresultingnotonlyfromtectonicsubsidencebutalsofromtopographicdifferencesbetweensourceareas(mountains)andbasins(endorheicplains).Thismakesadifferencewithexorheicareas,andallowedforathoroughsedimentaryrecordoftheNeogenetobedepositedatthethreemainendorheicbasins(Ebro,DueroandTagus).Depositioninbasinsboundedbymountainchainscreatedaparti-cularenvironmentofisostaticconditionsatthebasinscale,be-causeofthesedimentaryllingofpreviousair-lledtroughs,withdifferencesindensityhigherthan2000kgm(seediscussiononthistopicinCasasetal.,2000bSincetheLateMiocenePliocene,endorheicbasinswerecap-turedbythepresent-dayuvialnetwork.Thisprocesswaslinkedto:(i)regressiveerosionintheEbroBasin(García-Castellanosetal.,2003;Babaultetal.,2006).AlthoughthecaptureoftheendorheicEbroBasinwasnotdirectlyrelatedtotectonics,extensionalmove-mentsbynormalfaulting(negativeinversion)withdownthrownblockstowardtheMediterraneancoastandtheoffshore(RocaandGuimerà,1992;Roca,1994)wereresponsiblefornarrowingthemountainthresholdseparatingtheendorheicEbrobasinfromtheseaandthusforfacilitatingthecaptureofthebasin.(ii)intheDueroandTagusbasin,owingintotheAtlanticatthepassivemargin,theendorheicexorheictransitionwasprobablyalsodrivenbyre-gressiveerosion.ItwaseasierandmoreadvancedinthecaseoftheTagusbasin(Martín-Serrano,1991).Accordingtootherauthors(BrumFerreira,1991),verticalmovementsintheonshoreoftheAtlanticcoastcouldalsoberesponsibleforbothloweringthecoastalplainsandhamperingtheDueroBasinfromerosionduringtheQuaternary.RiverprolesreectthemainlandscapefeaturesoftheIberianplateandtheendorheic/exorheictransition:TheDuerouvialbasin,drainingtheweakly-erodedTertiaryDuerobasin,showsastrongectionwherepassingfromtheTertiarybasintothecoastalplainacrosstheVilariçaFaultSystem(seeFigs.1,3and7).SimilarfeaturescanbeobservedintheSilriver,thatdrainsthenorthernmostpartoftheDuerobasinandisstronglyincisedinrecenttimes(Fig.5),and Fig.11.EvolutionfromendorheismtoexhorheismintheIberianpeninsulathroughtheTertiary.Endorheicareasprogressivelyreducinginsurfacewithtime.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 intheAlagonriver,atributaryoftheTagusthatisalsocuttingintotheDueroBasin.TheCentralSystem,thatseparatestheDueroandTagusbasins,alsoshowsanunusualdrainagepattern,withthewaterdivideclosertotheDueroBasin,thusinducingasouth-directeddrainage(towardstheTagus)foralmostalloftheinternalrangerivers.Alongitslongitudinalprole,theTagusrivershowsaprowithaheadwardstepfarthereastwithrespecttotheDueroriver,probablyreectingtheboundaryoftheNeogeneendorheiczoneFig.7).TheEbroriver,becauseofthepronouncederosionofitsbasinduringthePliocene/Quaternaryshowsaratherevenproandrepresentsamoreadvancedstageofbasinerosion(lessthan400mmeanelevation)thantheDuerobasin(closeto900mmeanelevationinintseasternpart),withhighlevelsofprobablePlioceneagepreservedonlyinthewesternmostpartofthebasin(Moreno,1979;Villenaetal.,1996).Asasummary,theDuerobasinisbeingcapturedbyalladjacentuvialbasins:TheEbrorivertotheE,theSilrivertotheN(Fig.5A)andtheTagusrivertotheS.DifferenthardnessofrocksbeingincisedcanbeusedasareasontoexplainthissituationwithrespecttotheTagus,butnotfortheSilriver.TheotherriversontheMediterraneanside(TuriaandJucar)showmoreunevenproles(Fig.7),withsuddenchangesatabout600ma.s.l.tojointhelow-reliefsurfacescorrespondingtotheeasternpartoftheIberianMeseta.Thesenon-regularprolescanbeinterpretedasearlystagesoftheevolutiontowardsregularproresultingfromyoungextensionaltectonicsneartheMediterraneancoastloweringthelocalbaselevel.TheSegurariveroccupiedthelowlandscreatedbyextensionaltectonicsintheAlborandomainandtheAlgerianbasin,itssourceareaislocatedintheExternalBeticsanditslongitudinalproleindicatesthattheSeguraRiverisnotrelatedwiththeIberianMeseta.AsreectedbythewestwardpinchoutofUpperCretaceoussediments,whicharewidespreadintheeasternpartoftheIberianPeninsula,thepaleo-topography(attheIberianmassif,westernpartofIberia)duringtheLateCretaceouswashighenoughtoallowforPalaeozoicrockstoemergeabovesealevelduringtheCretaceoussea-levelrise.FromgeologicaldataPalaeozoicpaleo-reliefscanbeestimatedtobeatleast100mhigherthanthesurroundingsurface,becausethisistheelevationdifferencebetweenPalaeozoicresidualreliefsandthelowermostdepositionalTertiarylevel.Thispaleotopographyisconsistentwithestimatesestablishedassuminglocalisostasy(c.f.Gaspar-Escribanoetal.,2004;DeVicenteetal.,2007).TheresidualtopographyiscalculatedfromobservedTertiarysedimentthicknessandobservedtopographyintheTagusandDuerobasins.FromtheassumptionthatpositivevaluesofresidualtopographyreectMesozoicpaleo-topography,apaleo-topographyofca200300mcanbeinterpretedinthewesternpartoftheTagusbasin,andahigherpaleo-topography,upto800m,inthewesternpartoftheDueroBasin.Theinterpretedpaleo-topographyisconsistentwithincreasedregionalcrustalthickness(excludingsediments)interpretedinthegravityprolesoftheCentralSystemDeVicenteetal.,2007).DuringtheOligoceneMiddleMiocene,sedimentsweretransportedfromthetopographichighsintheWesttothelowsintheEast.TheTagusandDuerobasinsbecamestarved,andtheireasternpartsgraduallyoverlledcausingalevellingofthetopographyinthewesternandeasternbasins.Atalaterstage,adrainagereversalgavewaytotheAtlanticpolarityoftheTagusandDueroBasins,favouredbyagentletiltingtowardstheSW.IntheagusbasinthiscanbededucedfromthedippingoftheUpperMiocenelacustrinelimestones,initiallyrelatedtotheupliftoftheCentralSystemwithalluvialfansystemsprogradingtowardtheSE.ThiscouldalsosuggestsomekindofgeneralupliftoftheIberianTheothertwomainriversontheAtlanticsideoftheIberianpeninsula,theGuadianaandtheGuadalquivir(Fig.6)showevenandlowproles,determinedbytheirevolutionwithinexorheicbasinslocatedbetweenupliftedareasbyrecentlithosphericfolding(Vicenteetal.,2007),thereforedeningastrongdifferencebetweenthenorthern(IberianMeseta)andthesouthernhalvesoftheIberianpeninsula.TheonlyexceptionistheupperGuadianabasin,withTertiaryendorheicevolutionandrecentlycapturedbyboththeGuadianaandtheJucarrivers.ThelowerpartoftheGuadianabasincouldalsobeconditionedbyhortsandgrabenparalleltotheNcoastlineasinterpretedbyDeBrumFerreira(1991).Inanycase,themarkedregularityoftheuvialnetworkpatternofthecentral-westernpartofIberia(Sil,Duero,Tagus,GuadianaandGuadalquivir)isanargumentfavouringgloballithosphericfolding(Cloetinghetal.,20024.4.Lineament-controlleddrainagepatternintheendorheicbasinsThepresent-daymorphologyofthemainTertiary(endorheic)basins(Ebro,DueroandTagus)isstronglyconditionedbyfractures(detectedfromlineamentmappingofsatelliteimages,digitalelevationmodelsandaerialphotographs,Fig.12).Inthispaperweconsiderthatlineamentsarestraightlinearfeatures,presumablyexpressingasubsurfacephenomenon,thatdifferdistinctlyfromthepatternsofadjacentfeatures(Sabins,1987).TheselineamentsshowaNEdominanttrendintheDueroandTagusbasins(Giner,1996;Cortésetal.,1998;Casasetal.,2000a;Cortésetal.,2003)andWNWESEintheEbrobasin(ArleguiandSimón,2001;ArleguiandSoriano,2003),coincidingwiththetrendofthemainriversortheirmaintributaries(Fig.12Lineamentsaretheresultoffracturing,oratleastthereisacoin-cidencebetweenorientationoflineamentsandfaulting(Cortésetal.,1998),withfracturesshowing,ingeneralatoutcropscale,smallornulldisplacements(small-scalefaultsandjoints),affectinghorizontalorsub-horizontalbedsofdifferentkindsofNeogenerocks(sandstones,limestonesandevaporites,ArleguiandSimón,2001;ArleguiandSoriano,2003).Thedifferentdevelopmentofmorphologicallineaments,indifferentareasofthesamebasin,andbetweenthedifferentbasinscanberelatedtotheexhumation/erosionvelocityduringthePliocene/Quaternaryandtotheorientationoffracturescomparedtotheuvialnetwork.Ingeneral,lineamentsaremuchbetterdevelopedintheDuerobasincomparedtotheEbrobasin,and,withintheEbrobasin,itscentralpartshowsbetterdenedlineamentsthanitseasternpart.Thiscanbeexplainedbyaworsedevelopmentofmorphologicallineaments(i)whereexhumationanderosionwasstronger(Ebrobasinvs.Duerobasin),and(ii)wherethemainriversortributariesareobliqueoralmostperpendiculartothemainfracturetrends(NStributariesintheeasternpartoftheEbrobasin).AdifferentlineamentdistributionisfoundattheTagusbasin,wherelineamentsaremuchmoreevidentwhenapproach-ingtheIberianChain(easternpart).IntheDuerobasinmostlineamentscanbeinterpretedasthere-activationoffaultsintheVariscanbasement,sincetheirmaintrendscoincidewithpreviouscrustalheterogeneities(e.g.TheMessejanaFault,seelocationinFig.1isnucleatedonalargeJurassicbasicdike)anddifferentgeologicalunitslocatedatitsborders(Cortésetal.,2003).SomegentletiltingtotheEcanbeobservedintheterracearchitectureofsouth-directedstreamsintheNWcornerofthebasin.Themaximumagefortheracturingstagecanalsobeconstrainedfromtheageofthehighestaffectedunit,whichisLateMiocenetoPliocene(Mediavillaetal.,1996;Santistebanetal.,1996).However,littleisknownabouttheoriginofthetectonicregimecausativeforfracturemovement,sinceopeningofjointsmayoccurundereitherwrench,extensionalorisostatically-drivenregimes(Hancock,1985;Simónetal.,1999;ArleguiandSimón,2001IntheEbrobasin,mostfaultsonNeogenematerialsareinterpretedtobeofextensionalorigin(Simónetal.,1999;ArleguiandSimón,2001)andcouldalsocorrelatewithancientfracturetrends.ThesetrendsareNESWintheCataloniancoastalrange,locatedintheeasternboundaryoftheEbrobasin,andNWSEintheIberianChain(thatformsthesouthernboundaryoftheEbrobasin)whereverysimilarlineamentsarefound.(Fig.12).ThedominantWNWA.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 fracturesetintheEbrobasinhasbeenrelatedtoextensionalmovements(multidirectionalextensionalregime)linkedtotheopeningoftheValenciaTroughintheEast(SimónGómez,1989;Capoteetal.,2002).TheageoffracturingintheEbrobasinisnotsowellconstrainedasintheDuerobasin,becausemostfracturesarepreservedonrocksofMiddleMioceneage,andoutcropsofrocksofLateMioceneagedonotallowforlineamentanalysis,thereforeonlyaveryvaguelowerlimitcanbegivenforthislatefracturingstage.IntheTagusbasin,fracturingonUpperMiocenesedimentsdonotallowtoestablishageneralstressregime(Giner,1996),butacleardifferenceisobservedwithrespecttotheotherbasins:intenseQuaternaryfaultingactivitycausedastraightNESWgrabeninthelowermostpartoftheJaramastream,withcontinuoussedimentationandsubsidenceofmorethan100mthicknessofuvialsediments.ItishighlyprobablethatolderrocksthroughouttheIberianplatealsounderwentthisfracturingstage,althoughitisverydifculttorecognisebecauseofthesuperpositionoverolderdeformationperiods(Late-Variscanfaulting,Mesozoicextension,Tertiarycompression,etc.).Inanoverallview,lineamentmapsindicatetheprevalenceofthedominantNESWandNWSEtrendsallovertheIberianVariscanMasif(seee.g.ArthaudandMatte,19754.5.UpliftindicatorsNosystematicworkhasbeendoneuptodatetosummarisegeomorphologicalandthermochronologicalevidencesofupliftduringtheQuaternary,andtocorrelatethedifferentsectorsoftheIberianMeseta.Therefore,theirqualityandreliabilitycannotbe Fig.12.TectoniclineamentsinthenortheasternIberianpeninsulainterpreted(B)fromDigitalElevationModels(A).NotetheprominentWNWESElineamentsintheEbrobasin(northernpartofthemap),mainlydevelopedonNeogenerocks,andthecombinedWNWESEandNNESSWlineamentsintheIberianChain(southernpartofthemap).InthenorthwesterncorneroftheguretheNESWlineamentsdominantintheDueroBasincanbeinterpreted.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 completelyassessedatpresent.However,inouropinionseveralindicatorsofupliftcanbeusedasarecordforrecentmovementsindifferentpartsoftheplate:SteppedterracelevelsofQuaternaryalluvialdepositsalongthemainPyreneanrivers(Lewisetal.,2000;Sanchoetal.,2004indicatingrecentdifferentialupliftofthemountainrangewithrespecttotheEbroBasin,althoughotheruvialterracesystemsinIberiaseemtobemoreinuencedbyclimaticandeustaticcontrolsSantistebanandSchulte,2007PlioceneelevatedmarineterracesoftheNCantabrianMountainsrasapaleosurfaces),withapparentlyreversedmovements(sink-ing)intheGaliciamargin(DeBrumFerreira,1991SteppederosionsurfacesintheAtlanticcoast(DeBrumFerreira,1991),indicatingadifferentialupliftofabout900maccordingtothisauthor.FissiontracksanalysesindicateanacceleratedPlioceneupliftoftheCentralSystem(DeBruijneandAndriessen,2002)andtheCatalonianRange(Juez-LarréandAndriessen,2002),thatcanberelatedtomorphologicalfeatures(Tejeroetal.,20064.6.RecentstresseldandseismicityOnshorelarge-scalestructuresofNeogeneandQuaternaryageareconcentratedinthesouthernplatemargin(BeticChainanditsforeland),thenortheasternsector(CatalonianCoastalRange),theEasternpartoftheIberianChainandtheAtlanticmargin.WithintheIberianMesetalarge-scaleNeogeneandQuaternarystructuresarerare.However,severaldomainscanbedistinguished(mainlyfromanalysisofsmall-scalestructuresandearthquakefocalmechanisms)accordingtothemainfaultingmechanismsduringtheNeogeneandtheQuaternary:IntheEbrobasinandtheIberianChainrecentextensionalpaleo-stresses(triaxialextension)andfocalmechanismsaredominantMuñoz-Martínetal.,1998;Herraizetal.,2000;DeVicenteetal.,2008).Asimilarpattern(SouriauandPauchet,1998)isfoundinthePyreneesandtheCatalonianCoastalRange,wherethemainkilometric-scalerecentfaults(ingeneralwithaNESWtrend)canbefound(Masana,1994).AtthePyrenees,recentstressinversionsfrommomenttensorfocalmechanisms(DeVicenteetal.,2008indicatetheprevailingofnormalfaultingparalleltothemaintopographichighs.Itcouldindicatesomeongoingisostaticcom-pensationofthemountainrangeandtheclearcessationofactiveInsouthernSpain,seismicityandrecentfaultingarelinkedtotheAfricaIberiaconvergenceinaNWSEdirectionpostdatingtheAn5(LateMiocene)anomaly(Rosenbaumetal.,2002),withnormal(centre),reverse(West)andstrikeslip(East)faultingAndewegetal.,1999;DeVicenteetal.,2008),thelatterdominantlydextralalongtheENEWSWlinesparalleltothenorthernboundaryoftheGuadalquivirbasin.InonshoreareaslinkedtothewesternIberianmargin(NSpainandPortugal)focalmechanismsandrecentfaultingareextensional,compressionalandstrikeip(Cabral,1989;Ribeiroetal.,1996;Borgesetal.,2001),althougharelativedominanceofstrikeslipfaultingcompatiblewithNWSEcompressionseemstoexist,withthrustingmechanismsincreasingtowardstheS(Stichetal.,2006;DeVicenteetal.,2008SpatialdistributionofseismicityintheIberianplatedenesthemarginalareasoftheIberianMeseta,whereasseismicitywithintheMesetaisscarceandlimitedtoareaswithimportantTertiarythrusts(Camerosmassif,CentralSystem)orwithstrikeslipandextensionalfaultsformedduringtheMesozoicandtheTertiary(IberianChain-VilariçaF.S.),whereprobablythecontinentalcrustismuchweaker(VanWeesandStephenson,1995).TheinstrumentalseismicityismoreimportantintheTagusBasinthanintheEbroandDuerobasins,inagreementwithitsmorerelevantQuaternaryfaulting.5.DiscussionWhatistheoriginforthehighelevationoftheIberianMeseta?Fromthesetofdataherepresented,two,notincompatibleorigins,canbeproposed,sinceprobablybothofthemcontributedtothedevelopmentofthepresent-daylandscape.Thecontributionofeachofthesetwofactorsisstillamatterofcontroversy,andnewdataarenecessarytoestablishedawell-denedmodelfortherecentland-scapeevolutionoftheIberianpeninsula(Fig.13Alpine(mainlyCantabrianPyreneanrelated)compressionaltec-tonicswastheprincipalresponsibleforclosinginternally-drainedsedimentarybasins(Ebro,Duero,andpartially,Tagus).Thebase-levelsfortheseinternally-drainedareaswereprogressivelyhigherbecauseoftheirllingwithsedimentssourcedintheboundingmountainchains.Lithosphericfoldingcontributedtotheisolationofterrestrialsedimentarybasinswithintheplate.Arecentstageofuplift,alongwithfracturere-activation,probablyrelatedtothepresent-dayseismicityandplatekinematicsresultedinrisingtheIberianlow-leveltopography,asinterpretedfromgeomorphologicalevidences.BecauseofthepredominantnormalfaultingfocalmechanismsinthePyreneesandtheIberianChain,isostaticreboundsubsequenttocrustalthickeningcouldbeinter-pretedasthesourceforthislateuplift.Arebothcausescompatiblewiththeconvergentregime(AfricaIberiaEurope)prevailingintheIberianplatesinceLateCretaceoustimes?ThePyreneancompressionwastheresponsibleforthethickeningoftheIberiancrust,speciallyalongmountainchains,andgaverisetolithosphericfoldingasfarastheAnti-Atlas.ThemovementoftheAlborandomaininawestwarddirectionbroughtaboutthesub-sequentdecouplingofthelithosphere.Decouplingwasdiachronous,sinceitbeganintheeasternpartofIberiaandprogressivelymovedtowardstheWest.Accordingly,thecoupledcrustmantlesystemwithprevalenceofNSconvergenceisstillactiveinthewesternmostpartofIberia(GulfofCadizandtheLusitanianbasin),wheretheeffectofdecouplingduetotheemplacementoftheAlborandomainisnotrecordedatpresent.Theisostaticreboundsubsequentlyfolloweddecoupling,especiallyineasternIberia,thePyreneesandtheIberianChain,withlittleinuenceoftheBeticcompressionalsystem.Accordingtothishypothesis,theendorheicexorheictransitionintheDuerobasincouldbeadelayed,far-eldeffectofthemechanicaldecouplingbetweenIberiaandAfrica.Whyarehighareasatsimilarheights,andwhathasthenhamperederosionoftheDuerobasinandtheupperpartoftheGuadianabasin?AccordingtoDeBrumFerreira(1991)duringtheNeogeneupliftbasinsandhorstsformedattheAtlanticmarginpartlyhamperedtheerosionoftheDuerobasin.However,thishypothesisavoidsconsideringtheveryoriginoftheDueroendorheicPaleogenebasin,thatshouldbeclosedtotheoceaninswesternpartduringmostpartoftheTertiary,becauseofthetranspressionalactivityofleft-lateralNNESSWfaults.Structuresresultingfromthisactivitywereprobablytheresponsibleforclosingthewesternbasinboundarybuttheirre-activationduringtheNeogeneandQuaternaryisdifculttoestimatefrompresent-dayavailabledata,since,asdemonstratedbyBabaultetal.(2007)planationsurfacescanformatdifferentheightsinmountainranges.ThedifferentllingandevolutionarypatternbetweentheeasternandwesternTagusBasincanbeexplainedasrelatedtothemechanicaldecouplingbetweenIberiaandAfricaduringtheemplacementoftheAlborandomain(Miocene)inthesouthernpartoftheplate,allowingA.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 Fig.13.ConceptualsketchshowingtheevolutionoftheIberianMesetaduringtheTertiaryandtheQuaternary.Seetextforexplanation.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 forextensionalstressesintheEasternIberianplatetobegeneratedFig.2).Atthistime,extensionintheeasternpartoftheIberianplateco-existedwithcompressionandlithosphericfoldinginthewesternpartoftheplate(DeVicenteetal.,2008;DeVicenteandVegas,2009-thisissueSouthoftheTagusbasin,thepresentdayuvialnetworkcannotbeinterpretedastheresultofendorheic/exorheictransitionbecauseofthecontinuedthrustingactivityduringtheNeogene(anduntilpresent)ofthePortugueseCentralSystem(Ferreira-Soaresetal.,2005;Stichetal.,).TheGuadalquivirbasinhasbeenalsointerpretedintermsofforelandbasinevolution(seee.g.SanzdeGaldeano,1996ClimaticconstraintsshouldalsobeconsideredasapossiblecontributionforsomeofthechangesoccurringbetweentheTertiaryandtheQuaternary,likethereversalindrainageinthemarginalareasoftheendorheicsedimentarybasins.TheformationofplanationsurfacesonPalaeozoicandMesozoicrocksduringmostpartoftheTertiaryisinterpretedtobetheresultofpediplanationprocesses(GutiérrezElorzaandGracia,1997;CasasandCortés-Gracia,2002,andreferencestherein,seeFig.5B,D).Globalsedimen-tationratesincreasedduringthePlioceneandtheQuaternaryPeizhenetal.,2001)andthereforecanaccountforaninuenceindrainagechangeandcoarsedepositsoverlyingmanyoftheremnantsofpreviouslyformedplanationsurfaces.WhencomparingthehighlyelevatedIberianpeneplainswithotherelevatedareasintheEurasianalpinefoldbelt(Fig.14differencesariseespeciallywhenconsideringtheareainvolvedandtheamountofupliftorelevationineachcase.Sincemostofthemweredevelopedunderawell-establishedtectonicregime,somehintscanbeobtainedfortheevolutionoftheIberianMeseta(Fig.14Ingeneral,dimensionsofpeneplainslinkedtoextensionalhistoriesandpassivemargins(oldlandsontheLaurasiaandGondwanacontinents,e.g.KooiandBeaumont,1994;PeulvastandSales,2004;Jaspeenetal.,2006;Tinkeretal.,2008)arelargerandtheirevolutionincludestimespanslongerthantheupliftevolutionoftheIberianMeseta.Inaddition,theupliftandevolutionofsomeoftheseareasiscloselylinkedtoglaciationdeglaciationprocesses.PeneplainslinkedtocompressionaltectonichistoriesorconvergentregimesinAnatoliaandcentralareasofIran,MoroccoandAfghanistan(Fig.14arecomparableinsizetotheIberianplate.Furthermore,theirtectonicsettingisalsosimilar,sincetheyarelocatedintheoverriding,continentalplateoftheAfricanEurasiasubductioncollisionsystem.Twoofthem(IranandAnatolia)alsoshowacomplexsystemofhighplainsincludingbothareasoferosion(planationsurfaces)andsedimentation(basinllingsurfaces).InthecaseofIran,thedevelopmentofplanationsurfacesisrelativelyscarcewithrespecttotheIberianplate(i.e.highplainsofFiruzKunandSanbardanwithintheAlborzmountains),andtheyarestronglydissectedbytheuvialnetwork,buttheirstructuralpositionandmorphologicalfeaturesarecomparablewithIberiansurfaces.ThedifferentextensionofthiskindofsurfaceswithrespecttotheIberianpeninsulacanberelatedtothestrongertectonicactivityandhighertopographyinIran.Sinceplanationsurfacesareformedbypediplana-tionprocesses,longperiodsofslowdeformationratesfavourthewiderdevelopmentofthiskindofsurfaces(seee.g.CasasandCortés-Gracia,).AsimilarcontextcanbefoundinAnatolia(i.e.aroundtheTuzGölüendorheicbasin),wherethedevelopmentanddissectionofdifferentlevelsofplanationsurfacesarestronglyinuencedbyTertiaryandpost-Tertiarytectonics(seee.g.Dhontetal.,1998;TokayandAltunel,2005).Takingintoaccounttheageofthecompressionaldeformation,theIberianMesetacanbeconsideredanancientanalogueatslowerconvergencerateforthepresent-dayendorheic,intra-mountainbasinsofMiddle-EastAsia.InnorthernAfrica(Atlasuntains)faultingofplanationsurfacesbyreversefaultsandthrustsandoverallupliftisassociatedtotheareasofactivedeformation(i.e.Moreletal.,2000;Sébrieretal.,2006),whosemoderateactivityduringthePlioceneandtheQuaternarycanbecomparedtotheIberianChainandCentralSystemduringthePaleoceneandearlystagesoftheNeogeneandalsoprovideamodernanaloguefortheevolutionoftheIberianpeninsula,combiningbasementthrusting,basininversionArboleyaetal.,2004),pediplanationandfaultingofplanationsurfaces.Fromthecrustalthickness-elevationrelationshipsahypothesisofisostaticuplift(probablyerosion-triggeredduringpost-Neogenetimes)canbeproposedformuchoftherecentuprisingoftheIberianMeseta,andcontributionsfromupliftofriftshouldersinanextensionalsetting(i.e.openingoftheValenciaTrough)isprobablyaminimumpercentageofthetotalrecentuplift.Thisisconsistentwiththeextensionalre-activationofancientfracturelines,eventhoughaconvergentregimebetweenAfricaandIberiastillexists,thatprobablywasnotabletotransfercompressionalstressestotheinnerpartoftheplate(DeVicenteandVegas,thisvolume).Pervasiverecent(post-Neogene)fracturing,asdeterminedfromlineamentanalysisthroughouttheIberianpeninsulaistheresultofre-activationofLate-Variscanfractureswithdifferentorientations,withdominantdirectionschangingindifferentareasoftheIberianpeninsula(NESWtoNNESSWintheDuerobasinandthePortuguesebasementchangingtoWNWESEtoNWintheIberianChainandEbroBasin).Post-Neogenefracturingcanbeinterpretedastheresultofrecentandpresent-dayextensionalmovementsnearthetopographicsurface(seee.g.Antolínetal.,2008),consistentwiththestresseldintheuppercrustdeter-minedfromfocalmechanismsandcompatiblewiththeerosion-triggeredisostaticupliftoftheIberianmicrocontinent.AlthoughsomeofthegeodynamicmodelsproposedemphasisetheroleofextensionaltectonicsrecordedintheMediterraneanmarginintheupliftoftheIberianMeseta(cf.Introductionsection),inouropinionextensiondidnotincreasethemeanelevationoftheIberianChainandtheCatalanRanges,butinducedthedownwardsmovementoftheeasternblocksoffaultstowardtheMediterraneanside,consistentwithcrustalthinningasevidencedfromgravi-metricdata.RecentvolcanismintheinnerpartoftheIberianplatemaysuggestacontributionfromthermalactivitytotheupliftoftheIberianMeseta.However,NeogeneandQuaternaryvolcanicactivityisstronglylocalisedand,inouropinionthecrustalthicknesspatternandthermalowdistribution(Fernàndezetal.,1998)preventsinterpretinganimportantcontributionfromthermaluplift,asitoccursinotherareasoftheMediterraneanbelt(seee.g.Arboleyaetal.,2004;ElHaretal.,2006),althoughnewdatafromtheIberianmantleareneededtodiscardthishypothesis.Fromthedataanddiscussionsherepresenteditisevidentthat,inspiteoftheamountofdataexistinguptodate,thereisstillmuchworktobedonetounraveltheoriginoftheIberianMeseta,andespeciallythecontributionsofTertiaryandQuaternaryupliftsandthecausesforverticalmovements.Inouropinion,futureworkstobedoneshouldincludethefollowingaspects:precisedatingofdeformationalongrecentfaults,thatwillallowforachronologicalreferenceframeofdifferentmovementsinthedifferentpartsoftheplatetobeestablished.Furthermore,thedeterminationofmovementratesalongfaultscanhelptocon-strainratesofupliftforthedifferentdomains.datingofdepositslinkedtorecentevents,especiallythoselinkingtheendorheicandexorheicstagesinthedifferentbasins.establishingtherelationshipsbetweenrecentfaultsandseismicityinthemarginsandinnerpartoftheplate.datingtheexhumationofthemountainchainsandtheirrelation-shipswiththellingoftheforelandbasins.determiningthepalaeoclimaticevolutionlinkedtochangesinelevationofendorheicsedimentarybasinswouldhelptherecon-structionofpaleoelevationsindifferentbasinsinanindependentwayandcomparetheresultswithexhumationobtainedfromssiontrackdata.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030 Fig.14.Comparisonofarealdistribution(atthesamescale)andaverageelevationofdifferentelevatedplainsintheworldwiththeIberianmeseta.A.IberianMeseta.B.Atlasmountains,Morocco.C.Anatolia.D.TehranBasin,Iran.A.M.Casas-Sainz,G.deVicente/Tectonophysicsxxx(2009)xxx ARTICLEINPRESS Pleasecitethisarticleas:Casas-Sainz,A.M.,deVicente,G.,OnthetectonicoriginofIberiantopography,Tectonophysics(2009),doi:10.1016/j.tecto.2009.01.030