Abstract The Sakarya Zone and the Kırşehir Block of northern Turkey are separated by the İzmir–Ankara–Erzincan Suture (IAES) Zone which is the remnant of the northern branch of the Neotethys Ocean. During the closure of the IAES in the Late Cretaceous, northwards drift of the Kırşehir Block and its eventual indentation into the Sakarya Zone produced crustal deformation defined by thrusts and reverse faults, mainly between the indenting Kırşehir Block and the Sakarya Zone. Previous palaeomagnetic studies in the eastern part of the Pontides and the Sakarya Zone showed that palaeomagnetic declinations could record the deformation that resulted in the curvature of the IAES. In order to define the tectonic deformation of the northern part of the Kırşehir Block, we present new palaeomagnetic data from 57 different sites that include Mesozoic–Cenozoic sedimentary and volcanic rocks. The results from Late Cretaceous rocks (40 sites) indicate that large clockwise rotations of c. 140–165° occurred in the eastern limb of the bend, while anticlockwise rotations progressively decreased from c. 80° to 55° from SW to NW in the western limb of the bend. In contrast, small clockwise and anticlockwise rotations are observed in the flat-lying segment of the suture zone. These rotation patterns are consistent with the geometrical trends of the IAES in northern Turkey. Declinations of seven different Middle Eocene sites within the Kırşehir Block are rotated anticlockwise by c. 30–10°. This indicates that the deformation in the Sakarya Zone and the Kırşehir Block continued in the Middle Eocene.

Abstract Reconstructions of the Anatolian continent and adjacent areas assume the existence of one or more continental fragments during Mesozoic–Early Cenozoic time. These rifted from North Africa (Gondwana) during the Triassic, drifted across the Mesozoic Tethys and collided with Eurasia during latest Cretaceous–Paleocene time. Current reconstructions range from a regional-scale Tauride–Anatolide continent with oceanic basins to the north and south, to numerous rifted continental fragments separated by small oceanic basins. Field-based evidence for the inter-relations of the continental blocks and associated carbonate platforms is discussed and evaluated here, especially to distinguish between sutured oceans and intra-continental convergence zones. Several crustal units are restored as different parts of one large Tauride–Anatolide continent, whereas several smaller crustal units (e.g. Kırşehir massif; Bitlis/Pütürge and Alanya/Kyrenia units) are interpreted as continental fragments bordered by oceanic crust. We infer a relatively wide İzmir–Ankara–Erzincan ocean in the north and also a wide South Neotethyan ocean in the south. Several smaller oceanic strands (e.g. Inner Tauride ocean, Berit ocean and Alanya ocean) were separated by continental fragments. Our proposed reconstructions are shown on palaeotectonic maps for Late Permian to Mid-Miocene. The reconstructions have interesting implications for crustal processes, including ophiolite genesis and emplacement.

Abstract Metamorphic and igneous rocks exposed in NW-vergent thrust sheets and their autocthonous basement in the NE Pontides were dated by the U–Pb method using zircons, supported by geochemical data for granitic rocks. Two meta-sedimentary units (Narlık schist and Karadağ paragneiss) yielded detrital zircon populations of 0.50–0.65 and 0.9–1.1 Ga, suggesting an affinity with NE Africa (part of Gondwana). The youngest concordant zircon age is Ediacaran for the schist but Devonian for the paragneiss, bracketing the paragneiss depositional age as Mid-Devonian to Early Carboniferous. Metamorphic rims of zircon cores in the paragneiss gave Carboniferous ages (345–310 Ma). The zircon rim data indicate two Variscan metamorphic events (334 and 314 Ma) separated by a hiatus (320–325 Ma). Granite emplacement took place during early Carboniferous, Early Jurassic and Late Jurassic phases. The crystallization age of the early Carboniferous granites ( c. 325 Ma) corresponds to a hiatus in the zircon age data that could reflect subduction slab break-off. The Variscan granitic rocks intruded a Gondwana-derived continental terrane that was loosely accreted to Eurasia during early–late Carboniferous time but remained isolated from Eurasian-derived terrigenous sediment. In contrast, the Jurassic granitic magmatism relates to later back-arc extension along the southern margin of Eurasia. Supplementary material: Full isotope data (8 tables) are available at http://www.geolsoc.org.uk/SUP18558

Abstract Upper Ordovician–Upper Cretaceous high-pressure–low-temperature metasedimentary and meta-igneous rocks in the Dursunbey area provide insights into the Tavşanlı Zone (Anatolides) when compared to crustal units further south (e.g. Afyon Zone and Taurides). Schists near the base of the Tavşanlı Zone succession are cut by a small Upper Ordovician metagranite. This is covered by metaclastic sediments that are interbedded with bimodal rift-related basic-silicic volcanics of inferred Triassic age. Above this is a thick metacarbonate platform interpreted as the result of post-rift subsidence. Overlying metacarbonates, metapelites and metachert with metabasaltic intercalations (Upper Cretaceous?) reflect platform collapse. Overlying mélange contains blocks of ocean-derived intrusive and extrusive igneous rocks (e.g. ocean island-type basalt), metacarbonates and radiolarian chert, set in a low-grade metamorphosed shaly matrix. The Tavşanlı Zone was buried in a north-dipping subduction zone to 74–79 km at c. 88 Ma, exhumed and tectonically juxtaposed with accretionary mélange prior to the Late Palaeocene–Early Eocene. Geochemical studies of the meta-igneous rocks indicate the presence of ocean island basalt (OIB) and mid-ocean ridge basalt (MORB) sources modified by crustal contamination, evidenced by Th enrichment and fractional crystallization. A subduction chemical influence in the lower part of the succession (e.g. Nb depletion) was probably derived from subcontinental mantle lithosphere, modified during some previous subduction event (Panafrican?). Supplementary-material: Full geochemical data are available at http://www.geolsoc.org.uk/SUP18570

Abstract The Tauride–Anatolide continent, stretching for c . 900 km across western and central Turkey, is one of the world's best example of a subducted, exhumed passive margin within a collisional orogen. Twelve widely separated areas were studied and correlated to develop a new plate-tectonic model. A metamorphosed, rifted continental margin of Triassic–Lower Cretaceous age (Tauride–Anatolide platform) is overlain by Upper Cretaceous (Cenomanian-Lower Maastrichtian) pelagic sediments and then by both tectonic melange (subduction complexes) and sedimentary melange (foredeep gravity complexes). The melanges are overthrust by unmetamorphosed ophiolitic rocks, commonly peridotites with swarms of diabase/gabbro dykes, and are underlain by metamorphic soles. New geochemical evidence from basaltic blocks in the melange indicates predominantly subduction influenced, within-plate and mid-ocean ridge-type settings. The dykes cutting the ophiolites were probably intruded during early-stage intra-oceanic arc genesis. The metamorphosed continental margin, melanges and ophiolites in the north (Anatolides) are correlated with unmetamorphosed equivalents in the Taurides further south (e.g. Beyşehir and Lycian nappes). Oceanic crust of Triassic–Late Cretaceous age formed between the Gondwana-related Tauride–Anatolide continent in the south and the Eurasia-related Sakarya microcontinent in the north. Following Late Triassic–Early Cretaceous passive margin subsidence, the continental margin was covered by Cenomanian-Turonian pelagic carbonates ( c . 98–90 Ma). Ophiolites formed in an intra-oceanic subduction zone setting in response to northward subduction, probably within a two-stranded ocean, with the Inner Tauride ocean in the SE and the İzmir–Ankara–Erzincan ocean in the north/NW. Metamorphic soles relate to intra-oceanic subduction ( c . 95–90 Ma). Oceanic sedimentary/igneous rocks accreted to the advancing supra-subduction oceanic slab. The Tauride–Anatolide continental margin then underwent diachronous collision with the trench ( c . 85 Ma), deeply subducted and metamorphosed at HP/LT ( c . 80 Ma). Accretionary, ophiolitic and exhumed HP/LT rocks were gravity reworked into a southward-migrating flexural foredeep and progressively overridden ( c . 70–63 Ma). Slices of the upper part of the platform and its margin detached and were thrust southwards as the (Tauride) Lycian and Beyşehir nappes, together with regional-scale ophiolites. The continental margin and melange were simultaneously exhumed during Maastrichtian–Early Paleocene (70–63 Ma) and transgressed by shallow-water sediments, beginning in the Late Maastrichtian in the east ( c . 64 Ma) and the Mid?-Late Paleocene ( c . 60 Ma) further west. Remnant oceanic crust was consumed during Early Cenozoic time, followed by Mid Eocene (45–40 Ma) diachronous continental collision and a second phase of regional deformation. Rather than being progressive there were two stages of collision: first, Upper Cretaceous ophiolite emplacement driven by continental margin-subduction trench collision, and secondly Eocene collision of the Tauride and Sakarya/Eurasian continents.

Abstract The Izmir–Ankara–Erzincan suture zone (IAESZ) in the Central and the Eastern Pontides comprises a stack of thrust sheets of mainly Late Cretaceous–Early Cenozoic age that are restored as: (1) a subduction–accretion complex; (2) a continental-margin magmatic arc, plus an associated forearc basin; (3) a back-arc basin and its mainly sedimentary fill. Northward thrusting affected all of the Late Cretaceous units during latest Cretaceous (Campanian–Maastrichtian) time. This was followed by regional southward thrusting to form the present thrust stack during Mid-Eocene time. Alternative tectonic models are considered in the light of sedimentary, igneous geochemical and structural evidence, and global comparisons. We infer that the Northern Neotethys was subducted northwards beneath the Eurasian active margin during the Late Cretaceous. Subduction was associated with the genesis of a magmatic arc and a related forearc basin. The subduction zone retreated oceanwards, associated with the opening of a back-arc basin along the Eurasian margin, floored by oceanic crust and overlain by mixed terrigenous and volcaniclastic deep-marine sediments. Ophiolite genesis in a continental margin back-arc setting is suggested by the presence of screens of basement-type metamorphic rocks within an ophiolite-related sheeted dyke complex in the Eastern Pontides. During the latest Cretaceous closure of the inferred back-arc basin resulted in northward emplacement of ophiolitic and related units onto the Eurasian margin, as well exposed in the Central Pontides. In addition, accretionary mélange, volcanic arc, forearc and ophiolitic units were emplaced southwards onto the Tauride continent, represented by the Munzur platform in the Eastern Pontides, also during latest Cretaceous time. This incipient (‘soft’) collision was followed by widespread Paleocene–Early Eocene deposition of Nummulitic shelf carbonates and coarse clastic sediments on deformed and emplaced accretionary mélange, arc and ophiolitic units. Final closure (‘hard collision’) of the Northern Neotethys occurred during the Mid-Eocene, resulting in large-scale southward imbrication, together with northward backthrusting in some areas. Suture tightening and Plio-Quaternary strike-slip ensued.

Abstract The Central Pontides of northern Turkey is one of the best exposed seg-ments of the southern margin of Eurasia adjacent to the Tethys Ocean, at least from the Paleozoic onward, and its history can be taken as a guide to the tec-tonic evolution of the Pontides as a whole. A number of east-west-trending tectonic units record subduction-accretion and the growth of the south Eurasian margin. The Central Pontides also document Lower Cretaceous lithospheric extension related to opening of the Black Sea during the Late Mesozoic-Early Tertiary and a later active margin and collisional history. Three time intervals exemplify the tectonic evolution of the Central Pontides. During the Late Paleozoic-Mid-Jurassic, Tethys was subducted northward, with development of an oceanic arc (the Çangaldağ Complex) and rifting of a continental fragment (istanbul and Devrekani units), related to transform and/or active margin processes, to form a back-arc basin system (the Küre Complex and equivalents) in latest Paleozoic-earliest Triassic times. This was followed in the Lower Triassic by collision of a seamount (the Kargi Complex) with the active Eurasian margin, leading to deep burial beneath accreted units, including ophiolitic rocks. This collision possibly triggered collapse of the Küre back-arc basin further north, also in the Lower Triassic. Southward closure of the Küre Basin by the Upper Jurassic finally led to accretion of the entire tectonic stratigraphy to the southern margin of Eurasia during the “Cimmerian orogeny.” During the Late Jurassic–Early Cretaceous, the recently formed orogen sub-sided, possibly triggered by renewed northward subduction of Tethys, and carbonate platform sedimentation ensued during the Late Jurassic-Early Cretaceous. Crustal extension of the active margin then took place in the Early Cretaceous. The carbonate platform was dissected into half grabens, into which turbidites, debris flows, and olistoliths were shed. Early Cretaceous extension also activated exhumation of high-grade metamorphic rocks in the Central Pontides as a precursor to opening of the Western Black Sea marginal basin. During the Late Cretaceous-Early Tertiary, the Western Black Sea Basin underwent sea-floor spreading, while the southern margin rapidly subsided, associated with northward emplacement of ophiolites and ophiolitic melange. During the Early Tertiary, the Pontides were sutured to the Anatolides to the south, resulting in south-vergent reimbrication of the Paleotethyan basement, especially in southerly areas, and north-vergent compression near the Black Sea coast.