5 South Offshore Domain of the ∗ Central Anatolian Plateau Contents 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 5.2 Background and setting . . . . . . . . . . . . . . . . . . . . . . 106 5.2.1 Offshore domain: Outer Cilicia Basin . . . . . . . . . . 108 5.2.2 Onshore domains bounding the Outer Cilicia Basin . . 108 5.3 Reflection seismic data . . . . . . . . . . . . . . . . . . . . . . 110 5.3.1 Seismic facies, seismic ties, and onland correlations . . 110 5.3.2 Seismic line A . . . . . . . . . . . . . . . . . . . . . . . 112 5.3.3 Seismic line B . . . . . . . . . . . . . . . . . . . . . . . 114 5.3.4 Seismic line C . . . . . . . . . . . . . . . . . . . . . . . 117 5.4 Structural domains in the Outer Cilicia Basin . . . . . . . . . 117 5.4.1 Northern domain . . . . . . . . . . . . . . . . . . . . . 117 5.4.2 Southern domain . . . . . . . . . . . . . . . . . . . . . 118 5.5 RegionalstructuresandtectonicevolutionoftheOuterCilicia Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 5.6 Linking the Mut and the Cilicia basins . . . . . . . . . . . . . 124 5.6.1 Mut-Cilicia geologic onshore-offshore section . . . . . . 124 5.6.2 Tectonic regime and displacements . . . . . . . . . . . 126 5.7 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 5.7.1 The Central Cyprus Arc and its forearc basin system . 128 5.7.2 Uplift in the southern margin of the Central Anatolian Plateau . . . . . . . . . . . . . . . . . . . . . . . . . . 130 5.8 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 ∗To be submitted integrally to GSA Bull as: D. Ferna´ndez-Blanco, G. Bertotti, F. Pepe, A. Aksu and J. Hall, Neogene Tectonics of the Central Anatolia Plateau South Margin: Linking the MutandOuterCiliciaBasins 101 “In theory, there is no difference between theory and practice. But, in practice, there is.” Jan L.A. van de Snepscheut CAP Offshore Domain 103 Abstract The causes behind the growth of the southern margin of the Central Anatolian Plateau remain elusive. We use seismic, fieldwork, and literature constraints to study the Neogene kinematics and tectonic evolution of the transitional area between the uplifted onshore Mut Basin and the subsided offshore Outer Cilicia Basin, and link the latter to the Kyrenia Range, farther south. We constructed offshore-onshore sections along south Turkey and farther south to define the geometry and assess the syntectonic growth of a regional-scale Miocene monocline. In the northern margin of the Outer Cilicia Basin a system of top-to-the-south reverse faults, related with the monocline, offsets both the Miocene and the erosional unconformity underneath the Pliocene. Pliocene reflections onlap against the truncation surface and show syntectonic wedges and synsedimentary unconformities that indicate pre-Pliocene uplift and erosion followed by Pliocene and younger deformation. This large-wavelength kink-band fold has a 20–25 km (horizontal length) flank along the studied sections, in which we estimate a relative vertical displacement of 3.8km, rates of ∼0.5mm/y, and very low horizontal shortening values (<1%). Contractional structures developed also in the center and south of the Outer Cilicia Basin in relation to the Kyrenia thrust belt by mid-Pliocene or younger times. These data suggest that the ∼8 Ma surface uplift of the southern margin of the Central Anatolian Plateau is driven by compressional stresses, and that the modern Central Taurus behave as the forearc high of the Cyprus subduction system. 104 Chapter 5 5.1 Introduction Avarietyofmodelsexplaintheupliftmechanismsandrelatedtopographiesobserved in orogenic plateau systems around the world. Thermo-mechanical and structural models propose explanations such as thickening of the crust, ductile flow or delami- nation of the lower/middle crust, tectonic/magmatic underplating, or delamination of the mantle lithosphere [e.g. Bird, 1979; Powell, 1986; Nelson et al., 1996; All- mendinger et al., 1997; Yin and Harrison, 2000; S¸eng¨or et al., 2003; Rowley and Currie, 2006; G¨o˘gu¨¸s and Pysklywec, 2008; Biryol et al., 2011]. Precipitation-erosion drivenmodelsstatethataridconditionsduringreliefinitiationcreatelargesediment loads in the interior of the system and transfer tectonic shortening toward its exter- nal areas, developing higher topographic relieves and triggering feedback processes, such as humid shadow and sediment trapping [e.g. Sobel, 2003; Mulch et al., 2006b; Garc´ıa-Castellanos, 2007; Ballato et al., 2010]. The Neogene Central Anatolian orogenic plateau (CAP) in Central Turkey, has proven qualities to be considered an orogenic plateau, i.e. endorheism and aridity in theflatCentralAnatoliaregion,high-dischargeriversintherainygorgedTaurusand Pontides mountains, a thick crust, and a thin lithospheric mantle [e.g. Ate¸s et al., 2005;Faccennaetal.,2006;MutluandKarabulut,2011]. Differentmechanismshave been recently proposed to explain the formation of the CAP. Some contributions consider the CAP, from the Black Sea to the Mediterranean, a single system in which surface uplift developed by sub-crustal detachment-delamination of the lower crust at around 5Ma [Aydar et al., 2010] or by delamination of the lithospheric mantle at ∼8Ma [Bartol et al., 2010]. Even though surface uplift is roughly coeval in both margins of the CAP, i.e. Late Miocene to Early Pliocene, other studies propose different growth mechanisms for the northern and southern margins. The North Anatolian Fault is considered to have been driving the tectonic inversion of Neogene basins and piecemeal uplift in the northern flank of the CAP since the end oftheMiocene[Yıldırımetal.,2011]. InthesouthernmarginoftheCAP,slabbreak- off and subsequent asthenospheric mantle upwelling are proposed as the engine for post-8Masurfaceuplift,eitherjointlyto[Schildgenetal.,2012a]orseparatelyfrom [Cosentino et al., 2012] other causes behind a possible second post-1,6Ma uplift. Our goal is to constrain the mode of (de)formation of the southern margin of the CAP (SCAP), to better understand its regional tectonic frame, and to discuss the possible causes behind its formation. Our approach to the problem is to con- sider the SCAP as an integral part of a larger system continuing farther south, a domain controlled by subduction beneath the Cyprus arc [Calon et al., 2005a, b]. WestudytheoffshoreOuterCiliciaBasin(OCB),betweenTurkeyandCyprus, and its relationship with its bounding landward basins (Fig. 5.1). Whilst the growth of the southern limit of the OCB, the Kyrenia Range, has been related to a southward verging thrust belt [e.g. Calon et al., 2005a; McCay et al., 2013], the origin of the OCBnorthernmargin,theCentralTaurusMountains,isstillamatterofdebate[e.g. Cosentinoetal.,2012]. Therefore,wefocusspecialattentionontheOCBlinktothe north, i.e. the Mut Basin, which is on top of the Taurus Mountains. These basins are the (subsided and uplifted) components of the southern margin of the CAP. To study the sediments and structures developed before and during the formation of the SCAP we adopt a multi-scale geometric approach in which: CAP Offshore Domain 105 32ºE 34ºE 36ºE 38ºE N 36º30´ 0 Km 500 36º30 ´N N 3 36º s AB 6ºN MaB Taurus MoMuBn t ain Z T N A 35º30´ OAn ▲ Z K ▲ A▲ ▲ ▲K y rO▲▲ e C n i B▲▲a R ▲ ▲ a n ▲ ▲g e ▲ M▲ ▲I Ce ▲BB ▲ K M▲ ▲ 0 K10m0 200 35º30´N 32ºE 34ºE 36ºE 38ºE AB Adana Basin KMATZ Kyrenia-Misis-Adrın Thrust Zone MeB Mesaoria Basin AKZ Anamur Kormakiti Zone MB Mut Basin OAn Offshore Antalya Basin ICB Inner Cilicia Basin MaB Manavgat Basin OCB Outer Cilicia Basin Figure 5.1: Location map, showing the main marine Miocene basins in and around the study area of this contribution (onshore basins are in yellow, offshore basins are marked by their acronyms). The structures depicted in this map are based on the analysis of 1-arc DEM and LandSat 7 images from NASA. We depict the motion of the structures as known in the available literature. (i) We interpreted and depth-converted three N-S seismic lines in the offshore OCB and performed a detailed kinematic analysis of structures and sediment geometries. (ii) We produced two geologic cross sections from fieldwork data in the onshore Mut Basin, the northern counterpart of the OCB. (iii) Welinkedtheobtaineddatainaregionalonshore-offshoregeologiccrosssection delineating the monocline described by C¸iner et al. [2008], which was then geometrically analized to evaluate the timing and mode of formation of such structure, and thus that of the SCAP. (iv) We finally integrated these results with available data from the literature on northCyprustounderstandthetectonicsettinginwhichtheSCAPdeveloped and discuss its geodynamic drivers. This onshore-offshore approach allowed us to understand the latest Miocene- Pliocene tectonic transition in the SCAP, both geometrically and in time, and pro- vided constraints on the possible modes of plateau formation. 106 Chapter 5 5.2 Background and setting A broad marine basin formed by the Late Oligocene-Early Miocene times, in the northeasternmost Mediterranean that was then segmented into its present-day do- mains in Late Miocene. This idea is supported in southern Turkey by stratigraphic evidence for the Miocene sediments of the Manavgat, Mut, and northern Adana basins[Karabıyıko˘gluetal.,2000;C¸ineretal.,2008]. Stratigraphiccorrelationwith theoffshoreareastothesouthhasalsobeenestablished[I¸sleretal.,2005;Halletal., 2005a; Calon et al., 2005a; Burton-Ferguson et al., 2005; Aksu et al., 2005a, b] (see Fig. 5.2). Farther south, in the vicinity of the Kyrenia Range, deposition of the mostly deep-water upper Oligocene to upper Miocene sequence preceded shallow deposits, broadly similar to basins to the north and north-east, and with a common Tauride source [McCay and Robertson, 2012]. Mut Cilicia Kyrenia Mesaoria Basin Basin Range Basin Quaternary Fanglomerate Unit 1 Athalassa (1700 m∙s-1) Pliocene Mirtou Nikosia Unit 2 Messinian Lapatza Kalavasos (4000 m∙s-1) Tortonian Koronia Sertavul Serravall. Unit 3a Köselerli (3000 m∙s-1) Kythrea Pakhna Langhian Group Mut Burdigal. Aquitanian Derinçay Unit 3b Aalogrea - Terra (3000 m∙s-1) Ardana Basement CKoızmıldpaleğx Unit 4 LTarpyipthao Gs rGour.p TroLoedfkoasr Ca m/ plx. Figure 5.2: Seismic stratigraphy of the Cilicia Basin, showing the correlations between seismic stratigraphic units (and their associated velocities) and the onland sedimentary successions and exploration wells. Modified following Aksu et al. [2005a] and Calon et al. [2005b]. ThenorthernsectorofthisMiocenebasinispresentlyoutcroppingontheTurkish mainland and exposes a sedimentary sequence in excess of 1km in the Mut Basin, ontopoftheTaurusMountains. Thetopofthissequence,upliftedat2km,isdated as ∼8 Ma, Late Tortonian [Cosentino et al., 2012]. To the south, in the offshore Cilicia Basin, the bottom of the Messinian reaches ∼2,5km depth. More to the south, sedimentary deposits belonging to the previously continuous Miocene basin are now outcropping in the Kyrenia Ridge (Fig. 5.3). Therefore, two main periods ofdifferentialtectonicactivityareseen. IntheEarlyMiocene,aregionalsubsidence took place that continued until the Late Miocene. Then, the subsequent surface uplift of the northern and southern areas, coupled with continued subsidence in the central domain, led to the presently differentiated domains (Figs. 5.3 and 5.4). CAP Offshore Domain 107 N Taurus Mountains S Cilicia Basin Kyrenia Range ~40 km V.e.~2,5 pre-Miocene basement Continental Shallow water Deep water Salts Siliciclastics Figure5.3: SchematicN-Sregionalcrosssectionacrossstudyarea(approx.fromKaraman to Nicosia), showing the main type of depositional environment. Vertical exagg. ∼2.5. N S - 1 km Early Miocene - 1 km - 2 km Middle Miocene - 3 km 1 km - 1 km - 2 km Late Miocene - 3 km Figure 5.4: Schematic cross section showing the interpretation of the first order vertical motions and the overall scale of movements along the study area. The vertical scale is estimated as an approximation to the depth of deposition of the rocks of the area. The black line represents the position of the basement at every time-step, and the green area shows the location of the basement in the last time-step. Arrows depict the relative vertical displacement between the last and the present time-step. 108 Chapter 5 5.2.1 Offshore domain: Outer Cilicia Basin TheoffshoreOuterCiliciaBasin(OCB)liesintheEastMediterraneanSeabetween the mainland areas of south Turkey and north Cyprus (Fig. 5.1). The sea floor between these areas has a concave shape that opens and deepens westward, ranging from 800m to 1100m in depth. Loose boundaries can be defined to the east, where the sea floor gradually shallows as the OCB connects with the Inner Cilicia and Adana basins, and to the west, where the sea floor deepens abruptly to depths of 2km in a horizontal distance of ±20km, in relation to the offshore Antalya Basin. We consider the OCB as an elongated basin extending for ca. 120km in the N-S direction and approximately 160km in the E-W direction. The OCB can be seen as a forearc wedge top basin of the Cyprus arc-trench system. The OCB is bounded by the Taurus Mountains to the north and by the KyreniaRangetothesouth. Totheeast,theInnerCiliciaandtheAdanabasinsare progressively in-filled portions of the same system [Evans et al., 1978], the Cilicia- Adana basin complex. This foredeep of the Taurus Mountains [Aksu et al., 2005a] is bounded to the south and southeast by the Kyrenia-Misis-Adrin Thrust Zone (see Fig. 5.1). The topographic-bathymetric expression of this arcuate thrust zone embayssedimentswithsourcestotheeastandnortheast[Evansetal.,1978;McCay, 2010] and has led to the asymmetrical deposition of the thick Miocene and younger sediment infill of the Cilicia-Adana basin complex, as well as its relatively flat and markedly shallow basin floor. 5.2.2 Onshore domains bounding the Outer Cilicia Basin Present-dayonshoredomainsboundtheOuterCiliciaBasintothenorthandsouth. The northern component encloses the Central Taurus Range (Fig. 5.1). When con- sidered in a regional context, the modern Taurus Mountains are in a forearc high positionwithregardtotheCyprusarc-trenchsystem. LowertoUpperMiocenesed- iments, mostly marine, were deposited in the Mut Basin on top of the pre-Miocene Taurus substratum [Monod, 1977; Andrew and Robertson, 2002; Bassant et al., 2005; Eri¸s et al., 2005] (Fig. 5.3) and then uplifted. Toward the north, the marine sediments of the Mut Basin are coeval with fluvio-lacustrine deposits known from seismics for the Tuz G¨olu¨ area [G¨oru¨r et al., 1984; Huvaz, 2009; Fern´andez-Blanco et al., 2013], both of which are in turn unconformably covered by terrace and allu- vial fan Pliocene to Quaternary continental deposits [Monod et al., 2006; O¨zsayın et al., 2013]. In the southern margin of the Mut Basin, the Miocene rocks shape a monocline on top of the basement with a roughly flat surface in the hinterland that progresses into gently south-dipping geometries in its southward offshore continua- tion [C¸iner et al., 2008] (see Fig. 5.5). The E-W trending Kyrenia Range and the Messaoria plain, in Cyprus, form the southern onshore domain bounding the OCB. It is now accepted that the Kyrenia Rangeoutcropsinrelationwithaprominentdeep-rootedsouthvergingthrustsystem [Calon et al., 2005a, b; McCay, 2010]. In the Kyrenia Range, this imbricate system thrusts basement and Miocene rocks on top of Pliocene sediments and is in turn covered by Pleistocene deposits [Calon et al., 2005b; McCay et al., 2013]. Toward the south, the asymmetric Mesaoria Basin is a foredeep of the Kyrenia belt formed by Palæogene up to recent successions [McCay, 2010] (Fig. 5.5). C 33oE 34oE A Leyend Main features P O Pliocene-Miocene f 37oN 37oN erosional contact fs h o r e D e.g. Monod, 1977 o m Miocene monocline a i s.l. n ? ? Quaternary Middle Miocene ? ? e.g. Çiner et al, 2008 ? Transition Pliocene Lower Miocene Mut - Outer Cilicia basins 36oN 36oN and regional integration (this study) ? Upper Miocene Paleogene Miocene thrust system s.l. Up-Mid Miocene Pre-Cenozoic Basement e.g. Calon et al, 2005b Miocene asymmetry Km 0 30 60 90 33oE 34oE 35oN e.g. Mc Cay, 2010 Figure5.5: Mapshowingthedifferentcomponentsinandaroundthestudyarea. ThegeologicmapofSouthTurkeyandCenter-NorthCyprus depicts a common age nomenclature for the Cenozoic units. The age integration is based on the ages shown for the MTA geologic maps of 1 Adana and Konya 1:500.000 [Ulu, 2002; S¸enel, 2002], and the geologic map of Cyprus 1:250.000 [Constantinou, 1995], and the stratigraphic 09 correlation shown in Fig. 5.2. On the right hand, the main geometric and contact relationships for the area and one representative study for each of them are shown. 110 Chapter 5 33º E 34º E Taşuku N Bosyayι N 35º 35º Line C - Fig. 10Sadrazamk9ö .giF - By eniL 8 .giF - A eniL Tatlιsu21 .giF 0ininr PesttehieKflrlir2iieinsmp s5Rce rmsteseitoituicesnddy50 Finitgeurprreet5ed.6:seLisomcaitcionlinmesapinof tthhee Outer Cilicia Basin. 33º E 34º E 5.3 Reflection seismic data Three N-S multichannel seismic reflection lines have been analyzed (Fig. 5.6). The seismicprofileswereobtainedin1991and1992bytheMemorialUniversityofNew- foundland in collaboration with the Institute of Marine Sciences and Technology, Dokuz Eylu¨l University. The seismic lines cover an area south of Turkish onland locations Bozyayı and Ta¸suku, almost reaching Sadrazamk¨oy and Tatlısu cities in the north coast of Cyprus. These N-S seismic profiles, between 70km and 100km long, are ca. 30–35 km apart from each other in the east-west direction. Appendix A shows the raw seismic images of these lines. A small inset of a fourth line to the east is also shown (Fig. 5.6). Theseismiclines,originallyin.pdfformat,weretransformedtoSegYforanalysis of the seismic signal and seismic interpretation, and then converted to true depth. We performed these operations with GeoSuite AllWorks®. The seismic velocities shown in Aksu et al. [2005a] (and Fig. 5.2) were assigned to the different units for depth conversion of the interpreted time profiles. 5.3.1 Seismic facies, seismic ties, and onland correlations Seismicfaciescharacteristicsofspecificpackagesofreflectionsallowthedistinctionof fourseismicunitsintheOCB(Fig.5.7). Theseseismo-stratigraphicunitscorrespond tothosepreviouslydefinedbyAksuetal.[2005a]forthisarea. Thereaderisreferred to the aforementioned paper for a more detailed description of the seismic facies. Biostratigraphic and lithostratigraphic data used in this study were compiled by the Memorial University of Newfoundland from several onshore and offshore wells (see Fig. 6 in Aksu et al. [2005a], and the references therein). The ages of the seismo-stratigraphicunitsandtheirtentativecorrelationwiththestratigraphicunits outcropping onland were found by the same team by means of ties with exploration wells in the Inner Cilicia and Adana basins [Aksu et al., 2005a; Calon et al., 2005b]. The correlated ages for these units will be used in this contribution as shown in Fig. 5.7.