TurkishJournalofEarthSciences (TurkishJ.EarthSci.),Vol.13, 2004,pp.231-246. Copyright©TÜB‹TAK GeologyandStructuralEvolutionoftheTokatMassif (EasternPontides,Turkey) AL‹YILMAZ1 &HÜSEY‹NYILMAZ2 1CumhuriyetÜnversitesi,MühendislikFakültesi,ÇevreMühendisli¤iBölümü,TR-58140Sivas-Turkey (e-mail:[email protected]) 2CumhuriyetÜnversitesi,MühendislikFakültesi,JeofizikMühendisli¤iBölümü,TR-58140Sivas-Turkey (e-mail:[email protected]) Abstract: TheTokatMassifconsistsofapre-JurassicmetamorphiccomplexthatcropsoutwidelybetweenAmasya andRefladiyeinthewesternpartofeasternPontides,andwhichcanbecorrelatedwiththeKarakayaComplexof thewesternPontides.ThiscomplexisnamedtheTokatGroup,andisdividedintotwomainunits,namely,the TurhalMetamorphicsandDevecida¤Mélange.TheTurhalMetamorphicsformavolcano-sedimentarysequencein thenorthernpartoftheTokatMassif.Thelowerleveloftheformationismadeupofgneiss,amphiboliteandmica schists,whereastheupperpartisrepresentedbyanalternationofmicaschist,phyllite,metaclasticrocks, metabasiteandmarble,whichprobablyreflectsanarcassociation.TheDevecida¤Mélangeischaracterisedbya metavolcano-sedimentaryolistostrome,whichformsthesouthernpartofthemassif.Thisunitisquite heterogeneousandreflects,inplaces,asubductionmélangeand/orafore-arcsequence.TheDevecida¤Mélange mayhaveformedinasettingbetweenasubductionzoneandafore-arc.TheunitsoftheTokatMassifcanbe tracedalongtheeasternPontidesandalsoalongtheNorthAnatolianOphioliticBelt.Theseunitshavebeenaccreted tothemélangeprismastectonicslicesalongtheNorthAnatolianOphioliteBeltbeforetheCampanian.Someof LateCretaceousophioliticmélangeslicesalsocropoutintheTokatGroupasE–W-trendingtectonicslices.The ophiolitesandophioliticmélangearebelievedtohavebeenemplacedbothtothenorthandtothesouthduringthe LateCretaceous.Thenorth-vergentthrustshavebeenlaterrealignedintosouth-dippingthrustsduringa neotectonicphase. KeyWords: TokatGroup,KarakayaComplex,structuralevolution,easternPontides TokatMasifi'ninJeolojisiveYap›salEvrimi(Do¤uPontidler,Türkiye) Özet: TokatMasifi,do¤uPontidler’inbat›kesiminitemsiledenveAmasyaileRefladiyearas›ndageniflbiryay›l›m sunanLiyasöncesiyafltametamorfikbirkarmafl›kiletemsiledilirvebat›Pontidler’dekiKarakayaKarmafl›¤›ile koreleedilebilir.Bukompleks,Tokatyöresindeikitemelbirimeayr›labilir.Bunlar,TurhalMetamorfitlerive Devecida¤›Kar›fl›¤›’d›r.TurhalMetamorfitleri,masifinkuzeyinioluflturanmetavolkano-tortulbirdiziyikarakterize eder.Altkesimi,gnays,amfibolitvemikaflistlerle,üstkesimiisemikaflist,fillit,metak›r›nt›l›,metabazitve mermerinardafl›m›ndanoluflanbubirima¤›rl›kl›olarakbiryayistifininözellikleriniyans›t›r.Devecida¤›Kar›fl›¤›ise masifingüneyinioluflturanveyeryerolistostromalözelliktebloklumetavolkano-tortulistifikarakterizeeder.Bu birim,kimizamanyitimkar›fl›¤›,kimizamanyay-önüistifininözellikleriniyans›tanvea¤›rl›kl›olarakyitimzonuile yay-önüaras›ndageliflenheterojenbirkayatürütoplulu¤uiletemsiledilir.TokatMasifi’nioluflturanmetamorfik birimler,do¤uPontidler’indi¤erkesimlerindeveKuzeyAnadoluOfiyolitKufla¤›boyuncadaizlenmektedir.Bu birimler,dahagüneydekiKuzeyAnadoluOfiyolitKufla¤›’naaitofiyolitlimelanjprizmas›nageçKampaniyen öncesindetektonikdilimlerhalindeeklenmifllerdir.GeçKretaseyafll›olanofiyolitlimelanjprizmas›naaitbaz› dilimlerde,TokatMasifiaras›ndayaklafl›kdo¤u–bat›uzan›ml›olarakyeralmaktad›r.Dolay›s›yla,TokatMasifi birimleriaras›ndayeralanofiyolitlerveofiyolitlimelanjlar,ilkselyerleflimyerlerindeolmad›¤›ndanbunlar›nkonumu gözetilerekkenetkuflaklar›çizilemez.KuzeyAnadoluOfiyolitKufla¤›’n›oluflturanofiyolitlimelanjprizmas› bafllang›çtahemkuzeyehemdegüneyedo¤ruyay›larakbüyümüflvekuzeydekiyanimasiftaraf›ndayeralanmelanj dilimleridahasonrakis›k›flman›ngüdümündeyükselipafl›nm›flvekal›nt›yüzeylemelerneotektoniksüreçteretro- flaryajlarlaterslenmifltir. AnahtarSözcükler:TokatGrubu,KarakayaKompleksi,yap›salevrim,do¤uPontidler 231 GEOLOGYOFTHETOKATMASSIF Introduction Ithasalsobeensuggestedthat,atleast,theDevecida¤ ComplexistheequivalentoftheKarakayaComplexofthe TheE –W-trendingPontideorogenicbeltinnorthern Turkey,boundedtothesouthbytheNorthAnatolian westernPontides(Bingöl etal. 1975),andthatit OphioliteBelt(Figure1,Ketin1966),iscommonly representsasubduction-accretioncomplex(Tekeli1981). dividedintothewestern,centralandeasternPontides(Y. TheTokatMassifasawholeisplacedintotheSakarya Y›lmazetal. 1997a,b).Inthisclassification,theTokat ZoneofthePontides(Okay1989;Okayetal. 1991;Okay MassifliesintheeasternPontides.PartsoftheTokat &fiahintürk1997).Y.Y›lmazetal. (1997a,b),whohave Massifhavebeenstudiedbyvariousauthors(Alp1972; studiedthewholeoftheTokatMassif,haverenamedthe Öztürk1979;Özcan etal. 1980;Bektafl etal. 1984; rock-stratigraphicunitswithoutproperconsiderationof Özcan&Aksay1996;Seymen1991,1993;A.Y›lmaz thepreviousstratigraphicnomenclatureintheTokat 1980,1981a,b,1982a,b,1985;Okay1983,1996; Massif.Theyclaimedthatanophioliteoutcrop,extending Okay&fiahintürk1997).Thesestudieshave inanE –WdirectioninthecentreoftheTokatMassif, demonstratedthattheTokatMassifconsistsof representsanoldsuture,andthattherockstothenorth heterogeneouspre-Jurassicrockassociations.Thepre- andsouthofthis“suture”belongtodifferentformer JurassicrockassociationintheTokatMassifhasbeen plates. subdividedintoalowermetamorphicunitandanupper Thedifferenttectonicinterpretations,outlinedabove, blockyunit(Özcan etal. 1980;A.Y›lmaz1980,1982a, reflectsthescarcityofgeologicaldatafromtheTokat b).Thelowerunit,consistingofmetaclasticand Massif.Inthisstudyweaimtorectifythissituationby metabasicrocks,phylliteandmarbleisnamedtheTurhal providingdetailedgeologicaldatafromthemassif.These Metamorphics,andtheoverlyingmetavolcaniclasticunit dataincludethedescriptions,characteristics,distribution, withexoticblocksoftheDevecida¤Complex;these contactrelations,ages,depositionalenvironments,and stratigraphicnameshavebeenconfirmedbythe metamorphicgradesoftherockunitswithintheTokat StratigraphyCommitteeofTurkey(TSK1987). Massif.Wealsoprovideinformationonthelittleknown W 28e 32 36 40 W Black Sea Fault s R N t SE C BLACK S US ri SEA LE AS m UC e a A n C F a Figure 2 u l S KAM E S D E Ýstanbul Zone DE TM EA TI R NTI Tokat STERN PON U 40 RN PO T 40 WESTE SU N KIM AM IA A UT Sivas NORTH ANATOL KAR S UR AN E IAN S R- OL UT Ý S AT URE M D IT AN ÝZ M AN ST TFOR EA IDE PLA TH TAURIDE-ANATOL ENTS U PLATFO UIVAL O AN RM METAMORPHIC EQ S BI RA A KAM:Kargý Massif TM:Tokat Massif 36 28 32 36 AM:Akdaðmadeni Massif Figure1. SimplifiedtectonicdivisionsofTurkey.ThePontides(shadedregion)(afterKetin1966andgeneralevaluations).Abbreviations :KAM– Karg›Massif,TM–TokatMassif,AM–Akda¤madeniMassif.InsetshowsthelocationofthemapdisplayedinFigure2(afterOkay1 989; Okay&Tüysüz1999andpersonalevaluations). 232 A.YILMAZ&H. YILMAZ relationoftheTokatMassiftotheophioliticbelttothe Thisagecorrespondstotheperiodwhentheophiolitic south.Thisrelationshipisimportantforunderstanding mélangeprismwasthrustbilaterallytothenorthandto theplaceoftheTokatMassifintheregionaltectonic thesouth.ThemetamorphicrocksoftheAkda¤madeni framework. Group,whichbeartracesoftheAlpideorogeny(fiengör 1987),areregardedasthemetamorphicequivalentsof theAnatolide-TauridePlatform(A.Y›lmazetal. 1993).It RegionalGeology hasbeensuggestedthattheupperpartsofthe TherocksintheTokatMassifandinthesurrounding Akda¤madeniGrouprepresentnorth-facingAtlantic-type, regionbelongtooneofthefollowingthreebasictectonic passivecontinental-margindeposits(Seymen1985). units:thesearetheTokat,Yeflil›rmakandAkda¤madeni TheYeflil›rmakGroupconsistsofophioliticmélange, groups(Figure2;Özcan etal. 1980;A.Y›lmaz1980, representedbytheNorthAnatolianOphioliteBelt,andof 1982a,b).TheAkda¤madeniGroup,whichstructurally fore-arcsequences,whichlieunconformablyoverthe formsthelowerrockassociation(Figure3),ispartofthe mélange.Thisbeltstartsin‹zmir,andcontinues K›rflehirMassif(Seymen1985),andconsistsofgneiss, eastwardsinthedirectionofAnkara-Erzincanandjoinsto amphibolite,schist,quartziteandmarble(Figure3). theLesserCaucasusophioliticbelt(Zakariadze etal. Theserocks,whichareofcontinentalcrustalorigin,have 1983).TheUpperCretaceousophioliticmélangehasbeen beenregionallymetamorphosedintheamphibolitefacies, thrustalongtheNorthAnatolianOphioliteBeltnorthward andlaterwereaffectedbycataclasticmetamorphism andsouthwardoverothertectonicunits(A.Y›lmaz1980, (Alpaslan1993).Theageofthecataclastic 1982a,b,1985,1989;A.Y›lmaz&Özer1984;A. metamorphism,determinedbytheK/Armethod,falls Y›lmaz etal. 1985).IntheregionbetweenTokatand intotheSantonian–Maastrichtian(Alpaslan etal. 1996). Sivas,thepresentstructureischaracterisedbynorth- 40 36 Samsun 37 38 39 N BLACK SEA 41 Ordu 41 0 20 km T M aþova A G M A T Amasya I C Niksar B E L T Figure 4 Gümüþhane Turhal Reþadiye Koyulhisar Tokat Pulur Figure 6 Suþehri Agvanis Kelkit Köse daðý 40 40 Yýldýz Daðý Erzincan Evliya Tepe Kýzýldað Figure 5 36 37 Sivas 38 39 40 Tokat Akdaðmadeni Yeþilýrmak Group: mainly Yeþilýrmak Group: mainly Jurassic Group Group undivided ophiolites ophiolitic mélanges rocks Jurassic to Quaternary contacts overthrusts strike-slip settlements Tertiary rocks deposits faults Figure2. SimplifiedgeologicalmapoftheareabetweenTokat,SivasandErzincan(afterA.Y›lmaz1980,1982b;Özcanetal.1980;Özcan&Aksay 1996;andourownobservations).Insetsshowthelocationofthemapsdisplayedinthefollowingfigures. 233 GEOLOGYOFTHETOKATMASSIF N S 1500 m 1500 m 0 m 0 m Approximate scale Turhal Metamorphics, representing 020km metavolcano-sedimentary sequence Devecidað Mélange, including Permian Yeþilýrmak Group, representing ophiolitic Akdaðmadeni Group, including gneiss, and Triassic limestone blocks and in mélange prism including ophiolites and amphibolite, schist, quartzite and