TurkishJournalofEarthSciences (TurkishJ.EarthSci.),Vol.11, 2002,pp.1-13. Copyright©TÜB‹TAK GeologyoftheÖrenandSurroundingAreas,SWAnatolia ÖMERFEYZ‹GÜRER1 &YÜCELYILMAZ2 1UniversityofKocaeli,EngineeringFaculty,DepartmentofGeologicalEngineering,Vinsan, TR-41100Kocaeli-TURKEY(e-mail:[email protected]) 2 ‹stanbulTechnicalUniversity,FacultyofMines,DepartmentofGeologicalEngineering,Maslak, TR-80626‹stanbul-TURKEY Abstract: OntheLycianNappesofSWAnatolia,Neogenebasinsdevelopedalongtwodifferenttrendsindifferent periods.NNE–trendingbasinsformedduringtheEarly-MiddleMioceneperiodasexemplifiedbytheÖrenand Yata¤angrabens.Thesegrabenfillsconsistofthreedistinctrockunits.Atthebaseare(1)coarseclastics,sourced fromelevatedareasadjacenttothebasin-boundingfaults.Thesearelinearriver-valleyfills.Theygivewayupward to(2)alternatingcoal-bearingsandstoneandlimestoneasthegrabenvalleysweregraduallywidened,andthe surroundingmountainswerereducedbyerosion.Finally,lakeenvironmentformed,invadingtheregionduringthe advancedstageofgrabendevelopment.Inthelakesweredeposited(3)extensivemarlsandlimestones.Thelake depositsgraduallyonlappedthegrabenshoulders.TheNE–trendinggrabensextendSWtowardtheshoreofthe SW-NE–trendingKale-Tavasbasin.Thelakeandtheseabasinwereapparentlyconnectedasevidencedbyseveral marineincursionsfromthesouthintotheÖrenbasin.Themarineunitswedgeouttothenorth.Onthegraben shoulders,theLower-MiddleMiocenesedimentswereoverlainunconformablybyred,browncoarseclastic sedimentsaslinearandaxialfluvialdepositsduringLateMiocenetimewhenN-Sextensionaltectonicsbegan.Under thistectonicregime,someoftheN-S–trendingfaultswerereactivedasoblique-slipfaultswithadip-slip component.Later,thefluvialdepositswerereplacedbysedimentsofanewlakeenvironment,inwhichextensive lacustrinelimestonesweredeposited.Theextentsofthelakeswereregional,stretchingfarbeyondthelimitsof thegrabens.TheE-W–trendingfaultsborderingthenorthernmarginoftheGökovagrabencutandpostdatethe UpperMiocene-LowerPliocenelacustrineunits.TheLowertoUpperMiocenesequenceswereelevatedonthe grabenshoulders.AlongthenorthernedgeofGökovagraben,morethan400mofcoarsefluvialconglomerates anddebriswereformedinfrontofthiselevatedregion.TheGökovagraben,mostlyoffshore,isabout150-km- longandenlargeswestwardfrom5to30km.Thewesternmarginofthegrabenrisessteeplytoover1000m, butthesouthernmarginislessmarked.Thecoastlinehasmanybaysandsmalloffshoreislands. KeyWords: Ören,Gökova,Neogenebasin,extensionaltectonics ÖrenveÇevresininJeolojisi,Güneybat›Anadolu Özet: Güneybat›Anadolu’da,LikyaNaplar›üzerindeikifarkl›zamandaveikifarkl›yöndeNeojenhavzalar› geliflmifltir.KKDgidiflli,ÖrenveYata¤anhavzalar›Erken-OrtaMiyosendönemindegeliflmifltir.Bugrabenlerdeüç farkl›kayatoplulu¤uvard›r;tabandafayl›havzas›n›r›nakomflualanlardanderlenmiflkabaklastikleryeral›r.Bunlar çizgiselakarsuvadidolgular›d›r.Buçökeller,grabenvadisiningiderekgenifllemesiveçevreyükseltilerinerozyonla afl›nd›r›lmas›ilekömürarakatk›lar›içerenkumtafl›,silttafl›ardalanmas›nageçer.Grabengeliflimininilerievresinde gölortam›oluflmuflvebölgeyikaplam›flt›r.Göllerdebafll›cakireçtafl›vemarnçökelmifltir.Gölçökelleritedriciolarak grabenomuzlar›n›aflm›flt›r.KDyönlügrabenler,GB-KDyönlüKale-Tavashavzas›n›nGBk›y›s›nado¤ru genifllemifltir.Gölvedenizelhavzalar,Örenhavzas›n›ngüneyindedenizinbugrabeniçinedo¤rubirkaçkez ilerlemesiilek›smenbirleflmifltir.Bualandadenizelbirimlerkuzeyedo¤rukamalanmaktad›r.Kahverengi-bejrenkli, kömürarakatmanl›gölselincedetritiklervemarnlartemelüzerindeuyumsuzluklaçökelmifltir.Graben omuzlar›nda,Alt-OrtaMiyosençökelleriüzerine,GeçMiyosen’de,K-Ggerilmelitektoniklebafllayanlineerveaksiyal fluviyalortamda,k›rm›z›,kahverenkliklastiklerçökelmifltir.ButektonikrejimileK-Gyönlüfaylardanbaz›lar›, e¤imat›mbileflenleriolanoblikfaylarfleklindeyenidenhareketgeçirmifltir.Dahasonra,fluvialbirimleryerlerini yenibirgölünkireçtafllar›nab›rakm›flt›r.Gölünyay›l›m›bölgeselolupK-Ggrabenlerins›n›rlar›n›aflm›flt›r.Gökova grabenininkuzeykenar›n›s›n›rlayanD-Bdo¤rultulufaylar,ÜstMiyosen-AltPliyosengölselçökellerinikesmektedir. AltveÜstMiyosenistiflerigrabenomuzlar›ndayükselmifltir.Gökovagrabenininkuzeykenar›boyunca,yükselen blo¤unönünde,400metre’dendahakal›niriakarsuçak›ltafllar›vemolozbirikmifltir.Gökovagrabeni,büyük bölümüdeniziçinde,150kmuzunlu¤undavebat›yado¤ru5km’den30km’yekadargeniflleyenbirgrabendir. Grabeninkuzeykenar›nda,bat›ucu1000m’yiaflanyükseltilereulaflmaktad›r.Güneykenar›ndaise,birçokküçük koyveadalar›nolufltu¤u,dahaazbelirginbirmorfolojivek›y›çizgisigeliflmifltir. AnahtarSözcükler:Ören,Gökovagrabeni,Neojenhavzas›,gerilmelitektonik 1 GEOLOGYOFÖRENANDSURROUNDINGAREAS(SWANATOLIA) Introduction al. 1999,Bozkurt2000;Sar›ca2000).Theproposed Thereisacontroversyconcerningtheageofdevelopment synthesisofpreviouslyavailabledata(fiengöretal. 1985; oftheE-W–trendinggrabenbasinsofwesternAnatolia Walcott1988)or(commonly)ofinadequatedatawas (Figure1).Thetwomainviewsare:(1)theE-Wgrabens mostlyobtainedfromtherockscroppingoutalongthe begantoformduringtheLateOligocene-EarlyMiocene, immediatebordersofthegrabens(Seyito¤lu&Scott andhavebeencontinuouslyevolvingeversince(Seyito¤lu 1992,1996;Cohen etal. 1995).Totestandcompare &Scott1991);and(2)theE-Wgrabensareratheryoung thetwomodels,weundertookafield-mappingprojectto tectonicfeatures,andbegantoforminLateMiocenetime studytheÖrenarea(Figure2)becausethereandinthe (McKenzie1972;fiengör&Y›lmaz1981;Mercier etal. surroundingregions,morphologicallyactiveanddistinct 1989;Paton1992;Y›lmazetal. 1997,2000;Koçyi¤itet youngfaultsofvarioustrends,togetherwiththick Gulf of Edre IA 39° BEG N Ý GDG 38° BH A Massif BMG D KT Menderes 37° M YG ÖG AEGEAN SEA Kos Gulf of Gökova L.N.F. (L.N.) TAURIDES 02040 km Thrust 36° Normal and 27 strike-slip faults 29 30 mainly ophiolite, Tauride tectonic Neogene to recent mélange Cretaceous unit sedimentary rocks Cretaceous flysch and Jurassic to Cretaceous Neogene volcanic olistostrome assoc. Limestone and detrital rocks rocks (Bornova flysch zone) metamorphic rocks of Menderes Massif granitic plutons Figure1. GeologicalmapofwesternAnatolia(modifiedfromY›lmaz etal. 2000).BEG–Bergamagraben;GDG–Gediz graben,BMG–BüyükMenderesgraben;KT–Kale-Tavasbasin,LN–LycianNappes;LNF–LycianNappefront; BH–Bozda¤horst;ÖG–Örengraben;YG–Yata¤angraben.A,D,IandMarecitiesofAyd›n,Denizli,‹zmir andMu¤la,respectively.Insetshowsthelocationofthestudyarea. 2 N alluvium Milas QUATERNARY W E Gökova fm E. PLIOCENE Denizcik ls _+ L. MIOCENE Yatagan fm A A’ Sekköy fm NW No scale SE E.-M. A A’ Turgut fm MIOCENE +_ Gökbel cong. Akbük ls B B’ _ + E. MIOCENE Ö.F.GÜRER &Y.YILMAZ L. OLIGOCENE Gökçeören fm +_ _ Alaçam + MESOZOIC Lycian Nappes 0 4 8km PALEOZOIC and Tauride tectonic unit Scale Söðütcük _ + Pýnarören _ + Bayýrköy B +_ Kuyucak _ + + MS +_ _ Bozalan _ Ören + A +_ Akbük bay B’ GULF OF GÖKOVA Figure2. SimplifiedgeologicalmapoftheÖrengraben(modifiedfromY›lmaz etal. 2000)andassociatedcrosssections.MS–measuredstratigraphicsection(Figure4),A–Alakilise. 3 GEOLOGYOFÖRENANDSURROUNDINGAREAS(SWANATOLIA) Neogenesuccessions,arepresent.Inthispaper,thenew direction.Grainsizedecreasestowardthenorth,where dataresultingfromthisstudyarefirstpresentedand theredclasticsedimentspasslaterallyandverticallyinto thenthedataarediscussedtoshedlightonthegeological greyconglomerates,whichinturn,passverticallyand evolutionoftheseNeogenebasins. laterallyintogrey,well-sortedsandstoneswithsome TheGökovagrabenisoneofthemajorE-W–trending limestoneslenses.Locallythesepasslaterallyintogrey grabensofwesternAnatolia.(Figure2).TheÖrenareais shalescontaininglignitebeds.Theseshalesarelagoonal locatedtothenorthoftheGökovagrabenwherethere andshallow-marineclasticsedimentswhichcontain arelargeNeogeneoutcrops.ThisNeogeneiscommonly gastropods,bivalvesandbenthicforaminifersofLate referredtoastheÖrenbasin,whichextendsfromthe Oligocene-EarlyMioceneage(Becker-Platen1970; GulfofGökovainthesouthtoMilasinthenorth(Figure Koçyi¤it1984;Hakyemez1989;Akgün&Sözbilir 2).TheÖrenNeogenebasinisbounded,forthemost 2001).Thesandstonesareoverlainbyaflysch-like part,bysteeplydippingoblique-slipfaultswith sequence,composedmainlyofalternatingsandstonesand considerableamountofnormalslipcomponent. marls.Thissequencehasnumerousfluvialchannel deposits,ranginginthicknessfromafewmeterstoafew tensofmeters;thesewereemplacedasturbiditedeposits GeologyoftheBasins whichincisedtheunderlyingsoftsedimentsandalso IntheGökovaregion,basinsofvariousagesand disturbedtheiroriginalattitudes.Therefore,locally orientationshavebeenidentified.Theoldestbasin,the developedunconformitieswereformedinthesuccession. Kale-Tavasmolassebasinoffiengör&Y›lmaz(1981),is Upwardinthesection,thehighenergyofthedepositional orientatedENE-WSW.Theyoungestbasinisthemodern environmentdecreases,asevidencedbyfining-upward Gökovagraben.Betweenthedevelopmentofthese profiles,andeventuallytheclasticsedimentsaregradually approximatelyENE-WSWorE-Wbasins,roughly replacedbylimestonesoftheKaleformation.Faunafrom N-S–trendingbasinsformedduringtheEarlyMiocene thelimestonesyieldAquitanian-Burdigalianages andLateMiocene.Themajorgeologicalcharacteristics (Hakyemez1989;Görür etal. 1995;Akgün&Sözbilir ofthesebasinsarebrieflydescribedbelow. 2001). TheKale-TavasBasin TheÖrenBasin TheKale-Tavasistheoldestbasinoftheregion,andits TheÖrenandYata¤anbasinsaresubparallelbasins sedimentaryfillrangesfromUpperOligocenetoLower trendingapproximatelyNNW-SSE(Figures1and2). Miocene.ThefilloftheKale-Tavasbasinisbest-observed ThesebasinsdisplayidenticalstrataofEarlytoMiddle intheareathatextendsfromnortheastofDenizliinthe Mioceneage.Typically,thebasinunitsrest easttotheGökovagrabeninthewest(Figure2). unconformablyontheslightlymetamorphosedrocksof thewesternTaurides.Inplaces,thelowermostclastic