Lycian Nappes Research Articles

Formation of the Late Palaeozoic Konya Complex and comparable units in southern Turkey by subduction–accretion processes: Implications for the tectonic development of Tethys in the Eastern Mediterranean region

The southern margin of Eurasia, from the Balkan region eastwards, is widely envisaged as an active continental margin related to northward subduction, at least during Late Carboniferous–Early Cenozoic time. By contrast, the Late Palaeozoic setting of the southern (Gondwana) margin was previously interpreted as an intra-continental marginal basin related to southward subduction beneath the northern margin of Gondwana, or as part of a forearc complex (e.g. forearc basin) related to northward subduction beneath Eurasia. Palaeotethyan evolution is recorded in the Konya Complex (new name), an assemblage of Palaeozoic (Silurian-Carboniferous) meta-sedimentary and meta-igneous rocks that is exposed beneath metamorphosed Upper Permian–Mesozoic shelf-type sediments in central southern Turkey to the north of the Tauride Mountains. The Konya Complex is dominated by large thrust slices of mainly Devonian shallow-water platform carbonates (Bozdağ unit). There is also a melange that is made up of lenticular sheets and blocks of mainly Lower Carboniferous shallow-water limestones, Silurian–Devonian black chert (lydite), pelagic limestones and rare blocks of mid-ocean ridge-type and within plate-type basaltic rocks. The blocks are set in a mainly terrigenous-derived siliciclastic matrix, locally including siliceous tuff. The matrix is interpreted as mainly deep-water turbidites and debris-flow deposits. An overlying, intact volcanic-sedimentary sequence includes chemically enriched extrusives (e.g. trachyandesites) that also exhibit a negative Nb anomaly, suggesting a subduction influence. Dykes crosscutting the carbonate platform units are relatively depleted and also show a subduction influence. Shallow-marine carbonates and terrigenous quartzose sediments of mainly Late Permian age are exposed above the Konya Complex in the west of the area. In contrast, Triassic non-marine, to shallow-marine, clastic sediments unconformably overlie the Konya Complex in the east of the area. Both the Permian and the Triassic sediments pass upwards without a break into a Middle Triassic–Upper Cretaceous platform carbonate succession, which was overthrust by accretionary melange and ophiolites during latest Cretaceous time. The Mesozoic carbonate platform and the underlying Konya Complex experienced polyphase deformation and partial high-temperature/low-pressure metamorphism related to Alpine (Late Cretaceous–Early Cenozoic) closure of Tethys. Comparison of Tauride and Pontide units suggests the deformed Konya Complex Upper Palaeozoic carbonate platform has Gondwanan affinities. We also compare the Complex with other Upper Palaeozoic units in southern Turkey, including the Tekedere unit (Lycian Nappes) and the Karaburun and Chios melanges. All of these units are interpreted to have formed by subduction/accretion processes. Alternative possible settings involve northward subduction, southward subduction, or terrane displacement (strike-slip). Northward subduction beneath Eurasia requires collisional assembly with Gondwana, possibly during the latest Triassic “Cimmerian orogeny” for which there is little evidence. A southward-dipping subduction zone would need to be located some distance outboard of the Gondwana margin as there is little evidence of Upper Palaeozoic arc magmatism in the Tauride platform. Emplacement as an exotic terrane, probably derived from further west in the Balkan region is also possible.

From palaeotectonics to neotectonics in the Neotethys realm: The importance of kinematic decoupling and inherited structural grain in SW Anatolia (Turkey)

In order to asses young, i.e. “neotectonic” fault kinematics and the relation with plate-tectonic processes in SW Turkey we focused on the questions: 1) what produced the structural grain, i.e. how and when are faults generated, 2) what was/is the kinematic behaviour of these faults and 3) during which period(s) were these faults active? Firstly, the distribution of faults has been investigated using a lineament analysis performed on satellite imagery and digital elevation models. We define five main tectonic domains in SW Turkey: 1 and 2) the Northern and Southern Western Anatolian extensional provinces; 3) the eastern Hellenic arc (including Rhodes Island and the submarine Anaximander mountains); 4) The Lycian Taurides and 5) the western limb of the Isparta Angle. Lineament analysis reveals dominance of three lineament groups, i.e. NNE-, ENE-, and WNW-trending, in all identified domains. Variations in the relative importance of lineament groups exist and are attributed to the specific tectonic evolution of each domain. A synthesis of recently published field data shows that the onset of activity of related fault groups is neither synchronous, nor uniform. The “structural grain” for the neotectonic deformation in SW Turkey is formed during the last stage of palaeotectonic deformation (stage 1), which is dominated by the onset of the Menderes Massif exhumation along a top-N major detachment, the Datça break-away fault [Seyitoğlu, G., Işık, V., and Çemen, İ., 2004. Complete Tertiary exhumation history of the Menderes massif, western Turkey: an alternative working hypothesis. Terra Nova, 16, 358–364.], and related SE-ward sliding of the Lycian Nappes in the footwall of this fault. This stage is characterized by spatially variable types of deformation that are delineated by, from NW to SE, the Datça Fault around the Menderes–Lycian contact zone and the Lycian frontal thrust zone, respectively. The kinematic decoupling along these structures explains the co-existence of top-N detachment type extension in the Western Anatolian Extensional province and ongoing nappe emplacement and piggy-back development in the Lycian Taurides. The decoupling also explains the lateral complexity of deformation associated with later neotectonic deformation. From late Miocene onward, stage 2 NNE–SSW extension dominated the Western Anatolian Extensional province, influenced by combined Anatolian extrusion and Hellenic subduction roll-back. Contemporaneously, bidirectional ESE–WNW and NNE–SSW extension controls the Lycian Taurides due to the effects of Hellenic arc expansion superposed on extrusion-roll-back extension. The zone of kinematic decoupling is characterized by structural complexity, with local transpressional features. During stage 3 (post-Late Pliocene), the same types of extension prevail in the Western Anatolian Extensional province and the Lycian Taurides, although a third tectonic regime becomes gradually more important. This regime is associated with a tectonic escape in the Hellenic arc that induced forearc slivers to be sheared of the expanding arc along (mostly) sinistrally displacing ENE-trending strike-slip zones. Several of these zones have been identified in the coastal zones of SW Turkey, either through recent seismicity or field observations and are especially focused in the Lycian Taurides domain. Here, they form what is classically referred to as the Fethiye–Burdur Fault Zone, which becomes gradually penetrated from the SW by oblique- or strike-slip zones, exemplifying the time-transgressive nature of the tectonic escape mechanism. Zones of kinematic decoupling remain persistent throughout the entire Early Miocene–Recent tectonic evolution of SW Turkey and explain the existence of differently deforming tectonic domains.

Syn-tectonic sedimentary evolution of the Miocene Çatallar Basin, southwestern Turkey

The Çatallar Basin is one of the Miocene basins located in the southern part of the Bey Dağları Massif (SW Turkey). This basin has been reinvestigated and new stratigraphic and sedimentological data are now presented. The Çatallar Basin lies in paraconformity on the Bey Dağları carbonate platform of Late Cretaceous to Palaeogene age. It consists of an impersistent, shallow-marine carbonate base (Karabayır formation, Late Oligocene to Early Burdigalian) followed by an onlapping detrital sequence including the Akçay and Bağbeleni formations (Langhian to Serravallian). The Akçay formation mainly contains turbidites in which several debris-flows and olistostromes are intercalated. The lowest debris flows derive from the local carbonate platforms of Cretaceous and Palaeogene age. Higher, the debris flows and olistostromes contain large carbonate blocks deriving from nearby sources (Bey Dağları platform carbonates), whereas the accompanying pebbles originate from the allochthonous ophiolitic units located farther to the north (Lycian Nappes) or to the east (Antalya Nappes). The origin of these ophiolitic detritus is a matter of debate. The new data obtained in this study favour a northern origin.

The late Early Miocene Acıpayam piggy-back basin: Refining the last stages of Lycian nappe emplacement in SW Turkey

Alluvial fan to shallow-marine sedimentation in the Acıpayam piggy-back basin took place in the hinterland zone of the SE-facing Lycian nappe stack and constrains the age and style of late-stage advance of these nappes. Syn-orogenic sedimentation commenced in Burdigalian time and is marked by coarse-grained alluvial fan deposits that directly overlie Mesozoic ophiolitic rocks. Palaeocurrent data obtained from these coarse-clastic units suggest a south-southeastward drainage. The succession fines upwards and passes into fluvial deposits that become increasingly enriched in carbonate clasts derived from tectonically deeper-seated nappes, suggesting progressive unroofening of the nappe pile. Upwards, the succession is transitional to a Late Burdigalian–Early Langhian marginal marine succession, consisting of off-shore fines with coal seams that overly both the coarse-clastic sediments and basement rocks. Clastic sedimentation ceased at the end of Early Langhian based on reef carbonates that cap the succession. Shallow-marine deposits and overlying reef carbonates confirm a marine transgression that has been reported from elsewhere in the Tauride Belt. Detailed sedimentology of the Acıpayam basin fill succession, its age and overall tectonic setting imply that during Burdigalian time the succession was deposited in a piggy-back basin, located in the hinterland zone of actively moving thrust sheets. We propose a model in which thick-skinned thrusting invoked inversion of early extensional faults in the autochthon and may explain the generation of large open folds with thick sedimentary sequences in their core. The formation of these large folds may have importantly influenced the frontal accretion such that active shortening moved into the hanging wall resulting in episodic nappe advanced of structurally higher nappes in a mode similar to thin-skin thrusting. The tectonosedimentary evolution of the Acıpayam piggy-back is strongly dependent on its position relative to the hinge of the large open fold. The absence of any compressional signatures in the basin fill succession indicates that these thrust translations ceased shortly after Aquitanian time. By Serravallian, the succession was interrupted and the region was uplifted to its present elevation, probably by gravitationally isostatic (orogenic) rebound of the nappe stack. After these episodes, tectonic extension predominated and the succession became dissected by nappe-front parallel normal faults that bound the present Çameli Basin.

Structural architecture of the Rhodes Basin: A deep depocentre that evolved since the Pliocene at the junction of Hellenic and Cyprus Arcs, eastern Mediterranean

Interpretation of ~ 1500 km of multi-channel seismic reflection profiles shows that the Rhodes Basin evolved in two distinct tectonic stages. A protracted Miocene convergence (episode P1) resulted in the development of a mainly SSE-verging fold–thrust belt. This period corresponds with the emplacement of the Lycian Nappes to the northeast and fold/thrust complexes on the Island of Rhodes to the west. This phase of deformation ceased in the late Miocene. The absence of evaporites in the Rhodes Basin suggests that this region must have remained above the depositional base of marine evaporite environment during the Messinian. The morphology of the M-reflector, and the architecture of the lowermost Pliocene growth strata in the central portion of the Rhodes Basin demonstrate the existence of rugged paleo-relief over the pre-existing Miocene fold–thrust belt in early Pliocene. The middle Pliocene–Quaternary phase of deformation is characterised by NE–SW sinistral transpression (P2), and rapid regional subsidence. The P2 deformation occurred in response to an actively curving Hellenic Arc and the increasing obliquity of its eastern limb, the Pliny–Strabo Trenches (or fault zones) to the convergence vector of the African Plate. During this time, the P1 structures became re-activated as transpressional faults, further facilitating the rapid subsidence. We envisage the evolution of the Rhodes Basin as the result of subsidence associated with loading of the large imbricate thrust panels that carry the western Tauride Mountains in the north. At present, the Pliny–Strabo fault zones are delineated as a NE–SW trending 30–50 km-wide zone that continue into the western segment of the Rhodes Basin. This fault zone is further correlated with the similar trending ~ 50 km-wide Burdur–Fethiye Fault zone in southwestern Turkey.

Tectonic development of an orogen-top rift recorded by its terrestrial sedimentation pattern: The Neogene Eşen Basin of southwestern Anatolia, Turkey

The Eşen Basin of southwestern Anatolia formed as a NE-trending intramontane extensional graben, ca. 15 km wide and 30 km long, in the Early Tortonian, after the southeasterly emplacement of the Lycian nappes during the Tauride orogeny. The basin originated due to gravitational collapse of the hinterland zone of the Lycian Taurides in response to the lithospheric thickening caused by microcontinent collision. Sedimentation commenced with the development of basin-margin alluvial fans and a southward-directed axial fluvial system, the latter expanding laterally, changing its channel pattern from braided to meandering and forming floodplain lakes. The isolated ephemeral lakes merged into a single lake at the basin centre, fringed with vegetated mires and desiccated by the end of Miocene time. The second pulse of rifting in the basin, dated to the Early Pliocene, is attributed to the roll-back and outward expansion of the Cretan subduction arc to the south. A new lake rapidly expanded, and the Pliocene deposition of a thick marly succession was terminated by the basinward advance of Gilbert-type deltas and gradual desiccation of the lake in the Late Pliocene. The third pulse of rifting, near the end of the Pliocene, formed new faults, tilted the basin-fill succession and records regional deformation due to the westward tectonic expulsion of the Anatolian craton. The base of the overlying Pleistocene alluvium is an angular unconformity, with fluvial terraces indicating considerable Quaternary uplift. The developmental stages of the Eşen Basin are consistent with the tectonostatigraphic evolution of the adjacent Çameli Basin to the north, which may thus serve as a reference framework for the tectonic history of the region's extensional grabens.

Extensional v. contractional origin for the southern Menderes shear zone, SW Turkey: tectonic and metamorphic implications

The southern Menderes Massif in southwest Turkey consists mainly of orthogneisses and overlying Palaeozoic–Middle Paleocene schists and marbles. The contact between the two distinct rock types is almost everywhere structural, herein named the southern Menderes shear zone: a S-facing, high-angle ductile shear zone that separates metamorphic rocks of differing grade. Although there is a consensus that the shear zone was associated with top-to-the-S–SSW shearing and is of Tertiary age, its origin and nature have been highly debated over the last decade. Some claim the contact is a thrust fault, while others have argued for an extensional shear zone. Integration of field and microstructural data (the identification of different fabrics, associated kinematics and overprinting relationships) with fission-track thermochronology and the P–T paths of the rocks above and below the shear zone, supports the conclusion that the southern Menderes shear zone is an extensional shear zone and not a thrust. The data are consistent with a model that the exhumation and cooling of the southern Menderes Massif occurred after a period of extensional deformation. Pervasive top-to-the-N–NNE high-temperature–medium-pressure ductile shear structures (D2 deformation) overprint an early HP event (D1 deformation). The subsequent top-to-the-S–SSW greenschist shear band foliation (D3 deformation) developed mostly around the orthogniess–schist contact and forms the most characteristic features of the massif. The top-to-the-N–NNE structures are attributed to the main Alpine constructional deformation that developed during back-thrusting of the Lycian nappes during the latest Palaeogene collision between the Sakarya continent and the Anatolide-Tauride platform across the Neotethyan Ocean. The top-to-the-S–SSW structures are interpreted to be the result of the exhumation of the massif during the activity of the southern Menderes shear zone. The presence of these two distinct fabrics with differing kinematics suggests that the southern Menderes shear zone operated as a top-to-the-N–NNE thrust fault during early Alpine contractional deformation but was later reactivated with an opposite sense of movement (top-to-the-S–SSW) during subsequent Oligocene–Miocene extensional collapse.

Metamorphism of Precambrian–Palaeozoic schists of the Menderes core series and contact relationships with Proterozoic orthogneisses of the western Çine Massif, Anatolide belt, western Turkey

The tectonic setting of the southern Menderes Massif, part of the western Anatolide belt in western Turkey, is characterized by the exhumation of deeper crustal levels onto the upper crust during the Eocene. The lowermost tectonic units of the Menderes Massif are exposed in the Çine Massif, where Proterozoic basement orthogneisses of the Çine nappe are in tectonic contact with Palaeozoic metasedimentary rocks of the Selimiye nappe. In the southern Çine Massif, orthogneiss and metasedimentary rocks are separated by the southerly dipping Selimiye shear zone, preserving top-to-the-S shearing under greenschist facies conditions. In contrast, in the western Çine Massif, the orthogneiss is deformed and mylonitic near the contact with the metasedimentary rocks. The geometry of the mylonite zone and the observed shear directions change from north to southwest. In the north, the mylonite zone dips shallowly to the north, with top-to-the-N shear sense indicators showing northward thrusting of the orthogneiss over the metasedimentary rocks. In the southwest, the mylonite zone resembles a steep N–S striking strike-slip shear zone associated with top-to-the-SSW sense of shear. Overall, the geometry of the mylonite shear zone is consistent with northward movement of the orthogneiss relative to the metasedimentary rocks. Different shear senses are attributed to strain partitioning.AFM diagrams and P–T pseudosections with mineral parageneses of metasedimentary rocks of the Selimiye nappe and metasedimentary enclaves within the orthogneiss of the Çine nappe indicate a single Barrovian-type metamorphism. An earlier higher pressure phase is evident from staurolite–chloritoid inclusions in garnets of the Çine nappe, suggesting a clockwise P–T path. A similar path is inferred for the Selimiye nappe. Index minerals and the sequence of mineral parageneses point to a single amphibolite facies metamorphic event affecting metasedimentary rocks of both nappes, which predates Eocene emplacement of the high pressure–low temperature Lycian and Cycladic blueschist nappes. Northward thrusting of the orthogneiss onto the metasedimentary rocks of the Selimiye nappe is coeval with amphibolite facies metamorphism. Recently postulated polymetamorphism cannot be supported by this study. Petrological data provide no evidence for burial of the lower units of the Menderes Massif to depth greater than 30 km during closure of the Neo-Tethys. A major pre-Eocene tectonic event associated with top-to-the-N thrusting and Barrovian-type metamorphism could lend support to the idea of a Neo-Tethys (sensu stricto) suture south of the Menderes Massif and below the Lycian nappes.

The wide distribution of HP-LT rocks in the Lycian Belt (Western Turkey): implications for accretionary wedge geometry

Abstract In SW Turkey, Fe-Mg-carpholite has recently been recognized in the basal metasediments of the Lycian Nappes, which overthrust the Menderes Massif on its southern flank. This high-pressure-low-temperature (HP-LT) metamorphic index mineral was widely found in the Bodrum peninsula region. Our new metamorphic and structural data on similar carpholite-bearing rocks found farther north in several klippen of the Lycian Nappes located on top of the Menderes Massif show that HP-LT rocks in SW Turkey occur over a distance of >200 km in both north-south and east-west directions, thus indicating a wide HP-LT metamorphic belt. The deformation pattern from the Bodrum peninsula to Çivril, all along the contact between the Lycian Nappes and the Menderes Massif, reveals the role played by major top-to-the-NE shear zones contemporaneous with exhumation of the Lycian HP-LT rocks. This deformation shows an oblique direction of opposite shear sense relative to the earlier southward translation of the Lycian Nappes over the Menderes Massif, for which top-to-the-south displacements are preserved in the upper units of the Lycian Nappes on the Bodrum peninsula, as well as at the base of the Lycian nappe klippen located farther north. The widespread distribution of well-preserved Fe-Mg-carpholite-bearing rocks in the Lycian Nappes has implications for the geometry of the accretionary wedge responsible for HP-LT metamorphism in SW Turkey.

Neotectonic development of the Çameli Basin, southwestern Anatolia, Turkey

Abstract This study of the Çameli Basin presents a detailed basin evolution combined with structural analysis and provides the first detailed time-stratigraphic framework for the neotectonic development of Neogene grabens along the Fethiye-Burdur Fault Zone in southwestern Anatolia. During the Early Tortonian, the Çameli Basin was established as a broad fault-bounded fluviolacustrine basin that experienced NW-SE extension. By Mid-Pliocene time, continued NW-SE extension resulted in the formation of a new intrabasinal fault zone that split the basin longitudinally into two compartments. The development of a new generation of normal faults further split the basin into four narrow half-graben compartments at the end of the Late Pliocene. Structural analysis of basin-bounding and intrabasinal faults related to this three-stage basin development shows that NW-SE extension apparently persisted from Late Miocene to early Quaternary time. The youngest (i.e. Holocene), deformation is characterized by dextral shear along NE-SW-trending strikeslip faults and continuing NW-SE extension. The Late Miocene foundering of the basin was related to extension in the northerly hinterland zone of the still-emplacing Lycian nappes, whereas outward growth of the Hellenic Arc in response to the westward Anatolian extrusion is the main cause for NW-SE extension from the Pliocene onward. Dextral strike-slip faulting is localized and is associated with the activity of NW-SE-trending faults that accommodated NE-SW extension. The simultaneous activity of these faults suggests the existence of biaxial extensional tectonics, as initially proposed for the Burdur-Dinar area. Sinistral strike-slip faulting, continuing along the eastern Hellenic Arc, penetrated the southernmost part of Turkey but has not yet reached the Çameli Basin area. Our biostratigraphically well-constrained tectonosedimentary model for the evolution of the Çameli Basin provides a reliable time-stratigraphic framework for NE-SW extension in the ‘Fethiye-Burdur Fault Zone’ of SW Anatolia. We believe that this fault zone represents a broad zone of isolated or interconnected NE-SW-trending basins that formed under prevailing NW-SE extension, rather than being a significant strike-slip fault zone.

Mineral equilibria and geothermometry of the Dalaman–Köyceğiz thermal springs, southern Turkey

The Dalaman and Köyceğiz thermal springs are from karstic limestones belonging to Upper Cretaceous to Burdigalian Beydağları autochthon and Carboniferous to Lutetian Lycian nappes. They have measured temperatures of 24– 41 °C, specific electrical conductivities of 14,310–45,600 μS/cm, and are dominated by Na (1550–8500 mg/kg) and Cl (2725–15,320 mg/kg). The heat source of the geothermal systems of the area is tectonic related and the occurrence of the thermal springs is related to the young normal faults. Meteoric waters and seawaters recharge the reservoir rocks, are heated at depth with increasing geothermal gradient, and move up to the surface through the fractures and faults by convection trend and emerge as thermal springs. While thermal waters move up to the surface, they mix with different proportions of seawater and cold fresh waters. The seawater contribution to the thermal waters varies from 24% to 78%. Lake waters in the area are connected with thermal waters. Consequently, their chemical composition is influenced by the chemistry of thermal waters. Chemical equilibrium modelling based on measured outlet temperatures and measured pH shows that all the waters are oversaturated with respect to quartz and K-mica and undersaturated with respect to Al(OH) 3, anorthite, gypsum, siderite and SiO 2(a). Albite, alunite, aragonite, Ca-montmorillonite, calcite, chalcedony, chlorite, dolomite, Fe(OH) 3(a), fluorite, gypsum, illite, K-feldspar, kaolinite and sepiolite minerals are mostly oversaturated or undersaturated. Mineral saturation studies of the thermal springs indicate that dolomite, chalcedony and quartz are most likely to cause scaling at outlet conditions. Assessments from various chemical geothermometers, and Na–K–Mg ternary and mineral equilibrium diagrams suggest that the reservoir temperature is around 65–90 °C. The temperatures obtained from quartz, quartz-steam loss, Mg/Li geothermometers and mineral equilibrium diagrams give the most reasonable results.

Oligo-Miocene extension in the Lycian orogen: evidence from the Lycian molasse basin, SW Turkey

The Lycian molasse basin of SW Turkey is a NE-SW-oriented basin that developed on an imbricated basement, comprising the allochthonous Mesozoic rocks of the Lycian nappes and Palaeocene-Eocene supra-allochthonous sediments. The imbricated basement has resulted from a complex history related to the emplacement of different tectonic units from Late Cretaceous to Late Eocene. Following imbrication, extensional collapse of the Lycian orogen resulted in extensive emergent areas, some of which coincide with present-day mountains. These were surrounded by interconnected depressions, namely, the Kale-Tavas, Çardak-Dazkırı and Denizli subbasins. The Lycian molasse sequence contains a relatively complete record of the tectonic history of the Lycian orogenic collapse from which it was derived. The sequence is characterised by interdependence between tectonism and sedimentation, the latter of which includes fining-and coarsening-upward sedimentary cycles with syn-depositional intrabasinal unconformities. The Denizli subbasin consists of thick, coarse-grained wedges of alluvial fans and fine-grained fan-delta deposits formed in a shallowmarine environment. Some areas of the fan deltas were colonised by corals, red algae and foraminifera, forming patch reefs. The first phase of extensional collapse in the region is marked by the Lycian orogenic collapse, which may have been initiated by the beginning of the Oligocene (Rupelian), following the main Menderes metamorphism. Starting in the latest Early Miocene or in the Middle Miocene, the area of the molasse basin was subject to deformation with the Lycian nappes, and to erosion as well. At that time, the Lycian nappes, with some ophiolitic assemblages, were thrust over the molasse deposits and thus, NE-SW-trending folds were formed. The molasse deposits and thrust-related deformational structures were then unconformably covered by Upper Miocene continental deposits which belong to the neotectonic period of SW Turkey. The second phase of extensional collapse is marked by granitic intrusions and the formation of Miocene detachment-related extensional basins. This phase may have been related to the exhumation of the gneissic core of the Menderes Massif, from which fragments were derived and incorporated into the upper parts of the Denizli subbasin during the Aquitanian.

The Denizli graben-horst system and the eastern limit of western Anatolian continental extension: basin fill, structure, deformational mode, throw amount and episodic evolutionary history, SW Turkey

The Denizli graben-horst system (DGHS) is located at the eastern-southeastern converging tips of three well-identified major grabens, the Gediz, the Küçük Menderes and the Büyük Menderes grabens, in the west Anatolian extensional province. It forms a structural link between these grabens and the other three NE-NW-trending grabens—the Çivril, the Acıgöl and the Burdur grabens—comprising the western limb of the Isparta Angle. Therefore, the DGHS has a critical role in the evolutionary history of continental extension and its eastward continuation in southwestern Turkey, including western Anatolia, west-central Anatolia, and the Isparta Angle. The DGHS is a 7-28-km wide, 62-km long, actively growing and very young rift developed upon metamorphic rocks of both the Menderes Massif and the Lycian nappes, and their Oligocene-Lower Miocene cover sequence. It consists of one incipient major graben, one modern major graben, two sub-grabens and two intervening sub-horsts evolved on the four palaeotectonic blocks. Therefore, the DGHS displays different trends along its length, namely, NW, E-W, NE and again E-W. The DGHS has evolved episodically rather than continuously. This is indicated by a series of evidence: (1) it contains two graben infills, the ancient graben infill and the modern graben infill, separated by an intervening angular unconformity; (2) the ancient graben infill consists of two Middle Miocene-Middle Pliocene sequences of 660 m thickness accumulated in a fluvio-lacustrine depositional setting under the control of first NNW-SSE- and later NNE-SSW-directed extension (first-stage extension), and deformed (folded and strike-slip faulted) by a NNE-SSW- to ENE-WSW-directed phase of compression in the latest Middle Pliocene, whereas the modern graben infill consists of 350-m thick, undeformed (except for local areas against the margin-bounding active faults), nearly flat-lying fanapron deposits and travertines of Plio-Quaternary age; (3) the ancient graben infill is confined not only to the interior of the graben but is also exposed well outside and farther away from the graben, whereas the modern graben infill is restricted to only the interior of the graben. These lines of evidence imply an episodic, two-stage extensional evolutionary history interrupted by an intervening compressional episode for the DGHS. Both the southern and northern margin-bounding faults of the DGHS are oblique-slip normal faults with minor right- and/or left-lateral strike-slip components. They are mapped and classified into six categories, and named the Babadağ, Honaz, Aşağıdağdere, Küçükmalıdağ, Pamukkale and Kaleköy fault zones, and composed of 0.5-36-km long fault segments linked by a number of relay ramps. Total throw amounts accumulated on both the northern and southern margin-bounding faults are 1,050 m and 2,080 m, respectively. In addition, the maximum width of the DGHS and the thickness of the crust beneath it are more or less same (~ 28 km). The total of these values indicate a vertical slip rate of 0.15-0.14 mm/year and averaging 7% extension for the asymmetrical DGHS. The master faults of the Babadağ, Honaz, Küçükmalıdağ, Pamukkale and Kaleköy fault zones are still active and have a potential seismicity with magnitudes 6 or higher. This is indicated by both the historical (1703 and 1717 seismic events) to recent (1965, 1976, 2000 seismic events) earthquakes sourced from margin-bounding faults and some diagnostic morphotectonic features, such as deflected drainage system, degraded alluvial fans with apices adjacent to fault traces, back-tilting of fault-bounded blocks, and actively growing travertine occurrences. The kinematic analyses of main fault-slip-plane data, Upper Quaternary fissure ridges and focal-mechanism solutions of some destructive earthquakes clearly indicate that the current continental extension (second-stage extension) by normal faulting in the DGHS continues in a (mean) 026° to 034° (NNE-SSW) direction. Detailed and recent field geological mapping, stratigraphy of the Miocene-Quaternary basins, palaeostress analysis of fault populations and main margin-bounding faults of these basins, extensional gashes to fissures, and focal-mechanism solutions of destructive earth-quakes that have occurred in last century strongly indicate that extension is not unidirectional and confined only to western Anatolia, but also continues farther east across the Isparta Angle and west-central Anatolia, up to the Salt Lake fault zone in the east and the inönü-Eskişehir fault zone in the north-northeast. Therefore, the term “southwest Turkey extensional province” is proposed in lieu of the term “west Anatolian extensional province”.

Alpine high-P/low-T metamorphism of the Afyon Zone and implications for the metamorphic evolution of Western Anatolia, Turkey

Carpholite + chloritoid + pyrophyllite association occurs widely in the Triassic metaclastic rocks of the Afyon Zone in west-central Turkey. Fe-Mg-carpholite is associated with rare aragonite pseudomorphs and glaucophane in marbles and metabasites, respectively. The Afyon Zone consists stratigraphically of a Pan-African basement and an overlying Mesozoic cover sequence. The Pan-African basement, which shows Barrovian-type amphibolite-facies metamorphism, comprises garnet–mica schists, intruded by sodic amphibole-bearing metagabbros and leucocratic metagranites. It is unconformably overlain by a continuous metasedimentary sequence extending from Triassic to early Palaeocene. This cover sequence begins with metaconglomerates, which pass upwards into phyllites. Fe-Mg-carpholite occurs within this metaclastic sequence as rosette-like crystals in metapelites and fibres in quartz segregations. The metaclastic rocks are succeeded by metamorphosed platform carbonates, grading into Latest Mesozoic metamorphosed pelagic limestones, which in turn progress up to a Late Mesozoic–Early Tertiary olistostrome. This sequence is tectonically overlain by the blueschists of the Tavşanlı Zone. Fe-Mg-carpholite-bearing assemblages imply temperatures of about 350 °C and minimum pressures of 6–9 kbar, corresponding to burial depths of about 30 km for the Mesozoic passive continental margin sediments and the underlying Pan-African supracrustal metasediments and metaintrusives. The metamorphic rocks of the Afyon Zone are unconformably overlain by Upper Palaeocene–Lower Eocene sedimentary rocks, indicating a Paleocene age for the regional HP/LT metamorphism. This implies continuous younging of HP/LT metamorphism in the Anatolides related to northward subduction of the Anatolide–Tauride platform beneath the Sakarya Zone. From north to south this involved the Tavşanlı Zone (Campanian, 80 ± 5 Ma), the Afyon Zone (Palaeocene?), the Menderes Massif (Middle Eocene) and the Lycian Nappes (Late Cretaceous–Eocene?), all of which were probably derived from the frontal part of the Anatolide–Tauride platform.

Late Quaternary sea-level change, sedimentation and neotectonics of the Gulf of Gökova: Southeastern Aegean Sea

The sedimentary and tectonic Late Quaternary evolution of the Gulf of Gökova located at the southwest Anatolia–southeastern Aegean Sea region has been interpreted from 800 line km of 3.5 kHz and single channel airgun seismic reflection profiles. The older part of the Gökova basin is formed by mainly E–W trending faults and filled by the latest Miocene–Pliocene–Quaternary hemipelagic sediments with thickness up to 2.5 km. The Lycian Nappes, which primarily cover extreme southwestern Anatolia, represent the basement rocks for the Gökova region. Younger active faulting so-called Gökova Transfer Fault (GTF), which has not been previously discussed in the literature, trends NE in the central part of the Gulf of Gökova basin and records sinistral strike-slip motion broadly parallel to the convergence direction of the Aegean–Anatolian and African plates. The continental shelf of the northeastern Gulf of Gökova is mostly formed by numerous superimposed deltaic successions (depositional sequences), separated by major erosional unconformities. During times of lowered sea-level associated with late Quaternary glaciations, deltas prograded more than 40 km seaward from their present positions. Foreset progradation terminated with the rise of sea level in interglacial and post-glacial times and deltas were relocated far inland. These major transgressions resulted in unconformities that are correlated with the beginning of oxygen isotope stages 9, 7, 5 and 1, and provide chronostratigraphic markers for a detailed analysis of sedimentation patterns in the late Quaternary. All seismic lines show that the topset to foreset transition of the youngest Pleistocene delta system developed around 145–150 ms below present sea-level. Thus, the maximum Pleistocene sea-level lowering (18 000 years BP) was about −110 m. The positions of maximum regression for isotopic stages 6, 8 and 10 were found as 160, 190 and 215 m below present sea-level, respectively. Paleo shoreline positions during isotopic stages 2, 6 and 8 suggest an overall gradual subsidence of Gökova basin, during the last 0.5 Ma in the southeastern Aegean Sea. The seismic sedimentary chronology suggests that the Gökova Basin is subsiding at 0.3–0.4 mm/year. Three bathymetric low and E–W, WNW–ESE directed two main ridges in the gulf area are noticeable from the bathymetric data and are well correlated to the seismic data. While the main orientation of the gulf is E–W, more recent ENE–WSW and WNW–ESE structures are remarkable in the western and the mid-eastern part of the gulf respectively. Subsidence rates are greatest in the southern center of the basin and decrease northward, so that the northern area is being tilted southward.

Exhumation Paths of High-Pressure–Low-Temperature Metamorphic Rocks from the Lycian Nappes and the Menderes Massif (SW Turkey): a Multi-Equilibrium Approach

The Menderes Massif and the overlying Lycian Nappes occupy an extensive area of SW Turkey where high-pressure–low-temperature metamorphic rocks occur. Precise retrograde P–T paths reflecting the tectonic mechanisms responsible for the exhumation of these high-pressure–low-temperature rocks can be constrained with multi-equilibrium P–T estimates relying on local equilibria. Whereas a simple isothermal decompression is documented for the exhumation of high-pressure parageneses from the southern Menderes Massif, various P–T paths are observed in the overlying Karaova Formation of the Lycian Nappes. In the uppermost levels of this unit, far from the contact with the Menderes Massif, all P–T estimates depict cooling decompression paths. These high-pressure cooling paths are associated with top-to-the-NNE movements related to the Akçakaya shear zone, located at the top of the Karaova Formation. This zone of strain localization is a local intra-nappe contact that was active in the early stages of exhumation of the high-pressure rocks. In contrast, at the base of the Karaova Formation, along the contact with the Menderes Massif, P–T calculations show decompressional heating exhumation paths. These paths are associated with severe deformation characterized by top-to-the-east shearing related to a major shear zone (the Gerit shear zone) that reflects late exhumation of high-pressure parageneses under warmer conditions.

Facies and palaeogeographic evidence for the Miocene evolution of the Isparta Angle in its regional eastern Mediterranean context

We summarise facies evidence for four Miocene Basins (Lycian, Aksu, Köprü and Manavgat) within the Isparta Angle. Facies patterns are plotted on six palaegeographic maps restored to their pre-late Miocene setting. These maps are used to help infer the various controls on deposition. Facies trends and structural features suggest that the individual basins were kinematically linked within the overall African–Eurasia convergence zone. The Miocene Basins represent a classic example of how related basins may develop within an evolving orogen subject to variable controls through time. The dominant control was tectonic although autocyclic sedimentary processes (e.g., reef growth), and both relative and eustatic sea-level change played a significant role. From the palaeogeographic reconstructions and the tectonic context of the Isparta Angle, we infer that during the early Miocene, the westerly Lycian basin and the neighbouring Aksu basin experienced flexural subsidence related to southeastward thrusting of the Lycian Nappes. More distal effects of the forebulge may have caused uplift around the Aksu and Köprü basins initiating N–S half-grabens bounded by master faults on the eastern side of each basin. Later, the eastern basins of the Isparta Angle were influenced by regional northward subduction and inferred slab retreat within a remnant of the Southern Neotethys located within the Mediterranean Sea at the intersection of the south Aegean and Cyprus arcs.

Neotectonic evolution of the Anaximander Mountains at the junction of the Hellenic and Cyprus arcs

The Anaximander Mountains, occupying an outer-arc position at the junction of the Hellenic and Cyprus arcs, have been studied using a suite of geophysical data including multibeam swath bathymetry, backscatter images, seismic reflection profiles and gravity and magnetic data, which support an improved description of its deformation history. Lithologically, the western mountains can be correlated with the neritic limestones of the Bey Dağlarý unit of SW Turkey. The eastern mountains relate to the ophiolitic Antalya Nappe Complex. In addition to this lithological contrast, a deep-seated crustal difference, which is best reflected in gravimetry, relates to the mid-Tortonian Aksu thrust phase. After the Early–Middle Miocene eastward emplacement of the Lycian Nappes, the Serravallian–Tortonian stage was characterized by the development of an array of grabens with N120°E strikes, which occupied a vast continental area that extended from southern Aegean to southwestern Turkey. During the mid-Tortonian, the last phase of thrusting marked the onset of a different kinematic regime related to the westward rotation of the Anatolian platelet. This Late Miocene change marked the start of differential subsidence that resulted in the formation of the Anaximander Mountains and which is reflected by an unconformity surface between the Lower–Middle Miocene and Plio–Quaternary units. The Messinian–Quaternary period in the western part of the Anaximander Mountains was characterized by distributed sinistral shear parallel to N70°E, which was marked by the onset of an extension on N20°E-striking normal faults that formed long graben-like depressions. During the Pliocene, these basins were transected by N70°E-striking sinistral strike-slip fault zones, although continued crustal extension suggests deformation in transtension. The eastern part of the Anaximander Mountains is instead characterized by N150°E-striking normal and/or oblique normal fault zones, which lack significant evidence of strike-slip deformation. Close examination of newly calculated predicted relative plate motions between Africa (from NUVEL-1A) and Anatolia (from GPS measurements) indicates that plate motion vectors change rapidly at the junction between the Hellenic and Cyprus arcs because of the close proximity to the pole of Anatolian rotation. These calculations indicate that along both the eastern Hellenic Arc and the western Cyprus arcs (the Florence Rise), the relative motion between the Anatolian and African plates is sinistral. On the southern Florence Rise, deformation is characterized by pure left-lateral faulting, whereas farther northwest, in the eastern Anaximander Mountains, the component of strike-slip decreases. Although arc-normal convergence predicts the occurrence of thrust faulting, southwestward trench retreat also causes an extension internal to this outer-arc domain, such that the preexisting N120°E-striking thrust faults of the Aksu phase have been reactivated as normal to oblique normal faults during the Pliocene and Quaternary. The observed sinistral faulting on faults striking N70°E in the western mountains is consistent with the relative plate motion along the eastern Hellenic Arc and merges with the extensional domain in the eastern mountains.

The Deep Resistivity Structure of Southwestern Turkey: Tectonic Implications

Magnetotelluric data along two profiles, across the Lycian nappes and the Beydag autochthon of the southwestern Taurides in the eastern Mediterranean region images shallow and deep crustal structures. Inversion of the magnetotelluric data from profiles K and H reveals two subzones of the crust of varying thickness; the first is the conductive and viscoelastic lower crust (< 75 ohm m), whereas the second is the resistive (500-7500 ohm m) and brittle upper crust. The thickness of the uppermost conductive units, the Lycian nappes, is found to be 3.5-4 km in the northwest and 0.5 km in the southeast. The total thickness of the autochthon that forms the resistive upper crust varies from 7-16 km beneath the Lycian nappes to 11-20 km beneath the Korkuteli region along profile K. The depth to the upper/lower crust boundary varies from 10 to 30 km in the region. The resistive upper crust is interrupted by more conductive vertical zones. One of these zones along profile K coincides with the Fethiye Burdur fault zone (FBFZ), one of the most prominent geological structures in the region. The FBFZ lies in continuity with the Pliny and the Strabo subduction zones in the Mediterranean Sea. Projections of all the vertical resistivity discontinuities in the MT images onto the gravity map with the main surface faults show an alignment parallel to the FBFZ, and the Pliny and the Strabo trenches. The Bouguer gravity map shows a low gravity zone between the towns of Fethiye and Burdur. This gravity low also coincides with the alignment of projections of vertical high conductivity zones onto the map. Almost no earthquakes occur in the conductive lower crust, whereas significant earthquakes occur in the resistive upper crust, and the resistive lithospheric upper mantle (~250 ohm m) in the southeastern part of the region along the profile K. In contrast, in the northwestern part of the profile, the upper mantle is conductive (80 ohm m), indicating a viscoelastic character.

Correlation of syn-orogenic tectonic and metamorphic events in the Cyclades, the Lycian nappes and the Menderes massif. Geodynamic implications

Abstract The recent discovery of HP-LT parageneses in the basal unit of the Lycian nappes and in the Mesozoic cover of the Menderes massif leads us to reconsider and discuss the correlation of this region with the nearby collapsed Helle-nides in the Aegean domain. Although similarities have long been pointed out by various authors, a clear correlation has not yet been proposed and most authors insist more on differences than similarities. The Menderes massif is the eastern extension of the Aegean region but it has been less severely affected by the Aegean extension during the Oligo-Miocene. It would thus be useful to use the structure of the Menderes massif as an image of the Aegean region before a significant extension has considerably reduced its crustal thickness. But the lack of correlation between the two regions has so far hampered such comparisons. We describe the main tectonic units and metamorphic events in the two regions and propose a correlation. We then show possible sections of the two regions before the Aegean extension and discuss the involvement of continental basement in the Hellenic accretionary complex. In our interpretation the Hellenic-Tauric accretionary complex was composed of stacked basement and cover units which underwent variable P-T histories. Those which were not exhumed early enough later followed a high-T evolution which led to partial melting in the Cyclades during post-orogenic extension. Although the Menderes massif contains a larger volume of basement units it does not show significant evidence for the Oligo-Miocene migmatites observed in the center of the Cyclades suggesting that crustal partial melting is strictly related to post-orogenic extension in this case.