Ulvi Can Ünlügenç

The Misis–Andırın Complex: a Mid-Tertiary melange related to late-stage subduction of the Southern Neotethys in S Turkey

Abstract The Mid-Tertiary (Mid-Eocene to earliest Miocene) Misis–Andirin Complex documents tectonic-sedimentary processes affecting the northerly, active margin of the South Tethys (Neotethys) in the easternmost Mediterranean region. Each of three orogenic segments, Misis (in the SW), Andirin (central) and Engizek (in the NE) represent parts of an originally continuous active continental margin. A structurally lower Volcanic-Sedimentary Unit includes Late Cretaceous arc-related extrusives and their Lower Tertiary pelagic cover. This unit is interpreted as an Early Tertiary remnant of the Mesozoic South Tethys. The overlying melange unit is dominated by tectonically brecciated blocks (>100 m across) of Mesozoic neritic limestone that were derived from the Tauride carbonate platform to the north, together with accreted ophiolitic material. The melange matrix comprises polymict debris flows, high- to low-density turbidites and minor hemipelagic sediments. The Misis–Andirin Complex is interpreted as an accretionary prism related to the latest stages of northward subduction of the South Tethys and diachronous continental collision of the Tauride (Eurasian) and Arabian (African) plates during Mid-Eocene to earliest Miocene time. Slivers of Upper Cretaceous oceanic crust and its Early Tertiary pelagic cover were accreted, while blocks of Mesozoic platform carbonates slid from the overriding plate. Tectonic mixing and sedimentary recycling took place within a trench. Subduction culminated in large-scale collapse of the overriding (northern) margin and foundering of vast blocks of neritic carbonate into the trench. A possible cause was rapid roll back of dense downgoing Mesozoic oceanic crust, such that the accretionary wedge taper was extended leading to gravity collapse. Melange formation was terminated by underthrusting of the Arabian plate from the south during earliest Miocene time. Collision was diachronous. In the east (Engizek Range and SE Anatolia) collision generated a Lower Miocene flexural basin infilled with turbidites and a flexural bulge to the south. Miocene turbiditic sediments also covered the former accretionary prism. Further west (Misis Range) the easternmost Mediterranean remained in a pre-collisional setting with northward underthrusting (incipient subduction) along the Cyprus arc. The Lower Miocene basins to the north (Misis and Adana) indicate an extensional (to transtensional) setting. The NE–SW linking segment (Andirin) probably originated as a Mesozoic palaeogeographic offset of the Tauride margin. This was reactivated by strike-slip (and transtension) during Later Tertiary diachronous collision. Related to on-going plate convergence the former accretionary wedge (upper plate) was thrust over the Lower Miocene turbiditic basins in Mid–Late Miocene time. The Plio-Quaternary was dominated by left-lateral strike-slip along the East Anatolian transform fault and also along fault strands cutting the Misis–Andirin Complex.

Tectonic and sedimentary evolution of the Cenozoic Hatay Graben, Southern Turkey: a two-phase model for graben formation

Abstract New structural and sedimentary studies form the basis of a new interpretation for the Neogene Hatay Graben. Fault analysis reveals three contemporaneous trends of fault orientation (000°–180°, 045°–225° and 150°–350°) suggesting that the graben is transtensional in nature. Sedimentary studies show that, following shallow-marine deposition from the Late Cretaceous to the Eocene, a hiatus ensued until Early Miocene fluvial sedimentation. After a Mid-Miocene marine transgression, water depths increased until the Messinian salinity crisis, followed by a regression from the Pliocene to the present day. The basin initially developed as the distal margin of a foreland basin of the Tauride allochthon to the north, developing a classic sedimentary sequence during Mid-Late Miocene. Stresses caused by loading of the crust created a flexural forebulge to the south that supplied sediment mainly northwards. During the Plio-Quaternary, transtensional graben development took place, primarily influenced by the westward tectonic escape of Anatolia along the East Anatolia Fault Zone and left-lateral offset along the northward extension of the Dead Sea Transform Fault. This area is, thus, an excellent example of a foreland basin reactivated in a strike-slip setting. Our new two-phase model: foreland basin, then transtensional basin for the Hatay Graben, is in contrast to previous models, in which it was generally assumed that the Plio-Quaternary Hatay Graben represents a direct extension of the Dead Sea Fault Zone or the East Anatolian Fault Zone.

Geochemistry of Pliocene/Pleistocene basalts along the Central Anatolian Fault Zone (CAFZ), Turkey

Abstract Pliocene–Pleistocene volcanism accompanied strike-slip-related transtensional deformation along the Kizilirmak fault segment of the Central Anatolian fault zone (CAFZ) in the west of Şarkisla (Sivas–central Turkey). These volcanic rocks are represented by alkali olivine basalts. They can be divided into four different sub-groups on the basis of their Zr, Nb, TiO2 contents. A primitive mantle-normalized incompatible trace element diagram for four subgroups shows close similarity to typical OIB pattern. Some of the incompatible trace element ratios (Ce/Y, Zr/Nb, La/Ba, La/Nb) are also akin to OIB values. Highly fractionated REE patterns (La/YbN=24.7–9.2) with no Eu anomaly are the main features of the alkali basalts and are comparable to alkaline volcanism in continental rift zones. On the basis of Al2O3/TiO2, Nb/Y, Zr/Y Zr/Nb ratios, the geochemical differences among four sub-groups can be explained by variable degrees of partial melting of compositionally similar mantle source. Th/Nb, Th/Y, Nb/Y ratios and the primitive mantle-normalized trace element diagram suggests significant amount of crustal involvement for most of the alkali olivine basalts erupted along the CAFZ. Rupture of the continental lithosphere by strike-slip-related transtensional deformation might have caused decompressional partial melting of the asthenospheric mantle and generating alkali olivine basalts in this region.

Tectonostratigraphic evolution of the Upper Cretaceous–Cenozoic central Anatolian basins: an integrated study of diachronous ocean basin closure and continental collision

Abstract The Upper Cretaceous–Mid-Eocene Kırıkkale, Tuz Gölü, Haymana and Çankırı basins are bounded by the Pontide (Eurasian) continental margin to the north, the Niğde–Kırşehir microcontinent to the east and the Tauride–Anatolide continental unit to the south. The basins developed during northward subduction/collision of the İzmir–Ankara–Erzincan Ocean (‘northern Neotethys’) in the north and the inferred Inner Tauride Ocean in the south. Subduction of the İzmir–Ankara–Erzincan Ocean resulted in latest Cretaceous collision of the Niğde–Kırşehir microcontinent with the Pontide active margin and ophiolite emplacement. Some mid-ocean ridge-type oceanic crust remained to the SW and formed the basement of the Kırıkkale and Tuz Gölü basins. These basins are partially floored by an accretionary wedge to the west and by the Niğde–Kırşehir microcontinent to the east. Locally volcaniclastic, the sediment infill switched to terrigenous after latest Cretaceous. The Haymana Basin, further NW, developed as a forearc basin on the Mesozoic accretionary wedge and Pontide continental fragments. The Çankırı Basin also developed on an accretionary wedge, bounded by the Eurasian active margin to the north. An extensional setting prevailed during the latest Cretaceous related to subduction of remnant oceanic crust, followed by a switch to regional compression during Late Paleocene–Mid Eocene progressive and diachronous collision.

Late Cretaceous–Cenozoic subduction–collision history of the Southern Neotethys: new evidence from the Çağlayancerit area, SE Turkey

Abstract Evidence of the subduction–collision history of the S Neotethys is well exposed in the frontal part of the SE Anatolian thrust belt and the adjacent Arabian continental margin. The foreland succession in the study area begins with Eocene shelf carbonates, ranging from shallow marine to deeper marine, without sedimentary input from the Tauride continent to the north. After a regional hiatus (Oligocene), sedimentation resumed during the Early Miocene with terrigenous gravity-flow deposition in the north (Lice Formation) and shallow-marine carbonates further south. Clastic detritus was derived from the Tauride continent and oceanic accretionary material. The base of the overriding Tauride allochthon comprises ophiolite-derived debris flows, ophiolite-related mélange and dismembered ophiolitic rocks. Above this, the regional-scale Bulgurkaya sedimentary mélange (an olistostrome) includes blocks and dismembered thrust sheets of metamorphic rocks, limestone and sandstone, which include Late Cretaceous and Eocene foraminifera. The matrix is mainly strongly deformed Eocene–Oligocene mudrocks, hemipelagic marl and sandstone turbidites. The thrust stack is topped by a regionally extensive thrust sheet (Malatya metamorphic unit), which includes greenschist facies marble, calcschist, schist and phyllite, representing Tauride continental crust. Beginning during the Late Mesozoic, the S Neotethys subducted northwards beneath a backstop represented by the Tauride microcontinent (Malatya metamorphic unit). Ophiolites formed within the S Neotethys and accreted to the Tauride active margin. Large-scale sedimentary mélange developed along the Tauride active margin during Eocene–Oligocene. On the Arabian margin, a sedimentary hiatus and tilting (Oligocene) is interpreted to record initial continental collision. The Early Miocene terrigenous gravity flows represent a collision-related flexural foreland basin. Southward overthrusting of the Tauride allochthon took place during Early-Middle Miocene. Associated regional uplift triggered large-scale alluvial deposition. The foreland folded and faulted in response to suture zone tightening (Late Miocene). Left-lateral strike slip characterised the Plio-Pleistocene.

Plio-Quaternary stress regime in Eşen Çay Basin, SW Turkey

Abstract The Plio-Quaternary Eşen Çay Basin is situated at the junction of Hellenic and Cyprus arcs in southwestern Turkey. The basin is important for understanding the tectonic evolution of the region in relation to the Hellenic and Cyprus arcs. Fault data from unconsolidated Pliocene and Quaternary deposits, as well as from pre-Pliocene lithologies, are analysed in order to reconstruct the evolution of the stress field evolution from Pliocene onwards. Inversion of measured fault slip vector data identifies two main stress states: extensional and strike-slip. Both states are characterized by a NE–SW-trending minimum horizontal stress axis (σHmin=σ3). The mean R value is 0.67, indicating a triaxial state of stress. The inversion also indicates the existence of extensional and strike-slip faulting characterized by a NW–SE-trending σ3 axis. This indicates a change in the direction of the minimum horizontal stress axis (σ3) from a NW–SE-trending σ3 that dominated prior to Quaternary to a NE–SW-trending σ3 that dominated during Quaternary up to actual time.

Two-stage development of the Late Cretaceous to Late Eocene Darende Basin: implications for closure of Neotethys in central eastern Anatolia (Turkey)

Abstract The Darende Basin is an excellent example of an important, but little known, type of sedimentary basin that can form on the top of emplaced ophiolites prior to and during continental collision. The basin formation was preceded by southward emplacement of accretionary mélange and ophiolites onto the Tauride carbonate platform during latest Cretaceous. Sedimentation began during the Maastrichtian with non-marine clastic sediments accumulating in palaeovalleys. This was followed by a Maastrichtian marine transgression, triggered by extension along the basin margins. Rudist-rich patch reefs and a carbonate shelf developed in different areas. A second transgression during the Mid-Eocene was preceded by emergence, a hiatus (Paleocene), localized faulting and low-angle (<5–10°) tilting. Middle Eocene hemipelagic marls, shallow-marine Nummulites-rich carbonates, calciturbidites and sparse alkaline volcanism culminated in Late Eocene shallowing, emergence and then deformation. The first phase of basin development (Maastrichtian) is seen as extensional, related to slab-pull that resulted from northward subduction of remnant oceanic lithosphere beneath Eurasia in the Pontides to the north. The second phase of basin development (Mid–Late Eocene) is explained by crustal downflexure to form an under-filled foreland basin during the final collision of the Tauride continent with Eurasia. Basin uplift was delayed until after a Mid-Miocene marine incursion. Supplementary material: Full results of the palaeontological determination of collected samples from the Eocene aged sedimentary rocks of the Darende Basin are available at www.geolsoc.org.uk/SUP18544

Tectonostratigraphy of the Tercan-Çayirli Basin: Implications for the Neogene-Quaternary Tectonic Deformation of the Northeast Anatolian Block, Turkey

The Tercan-Çayirli Basin is located in the Northeast Anatolian Block, and is bordered by the North Anatolian fault zone to the south and the Northeast Anatolian fault zone to the north. The basin developed on top of a southerly obducted, Upper Cretaceous ophiolitic mélange and low-grade metamorphic thrust sheets during Oligocene time. The lower sequences of the basin consist of coarse-grained continental clastics, reflecting foreland basin development. An Early Miocene transgression covered eastern Anatolia; deposition during this event corresponds to the upper sequences in the Tercan-Çayirli Basin. Late Miocene-Early Pliocene time is represented by basaltic-andesitic volcanism and continental sediments deposited in foreland basins. Coarse fluviatile clastics were deposited in strike-slip fault-controlled basins during the Quaternary. Tectonic deformation styles of the Northeast Anatolian Block and the Tercan-Çayirli Basin are shaped by Late Miocene-Early Pliocene thrust tectonics and Late Pliocene-Quaternary strike-slip tectonics, respectively. Kinematic analyses of fault slip data show NNW-SSE directions of movement. The tectonic deformation style of the Northeast Anatolian block reflects the combined effect of Late Miocene-Early Pliocene southward accretion and Late Pliocene-Quaternary eastward escape of the block toward the Caucasus.

Editorial introduction to ‘Geological Development of Anatolia and the Easternmost Mediterranean Region’

The present set of 22 papers stems from the 7th International Symposium on Eastern Mediterranean Geology that was held in Adana, Turkey, 18–22 October 2010. After its initiation in l992, in Adana this international conference has been held successively in Jerusalem (Israel) in l995, Nicosia (Cyprus) in 1998, Isparta (Turkey) in 2001, Thessalonica (Greece) in 2004 and Amman (Jordan) in 2007. The Cyprus and Thessalonica conferences were followed by substantive publications, including one with a focus on Cyprus (Panayides et al. 2000) and another mainly concerned with the Balkan region (Robertson & Mountrakis 2006). A subset of the papers that were presented at the 7th Adana meeting, together with some others, have been prepared and edited for the present volume. Anatolia and the surrounding region provide an excellent opportunity for the study of fundamental geological processes, including rifting, seafloor spreading, ophiolite genesis and emplacement, collision, continental assembly and neotectonics. This volume should interest a wide cross-section of international researchers, including those concerned with hydrocarbons, mineral deposits and seismic risk, and also postgraduate students and advanced undergraduates. The papers highlight the role of fieldwork, the multidisciplinary nature of much of the current research in the region, the role of teamwork and the strong contribution being made by young scientists. Following an introductory chapter, the volume is divided into four sections covering different aspects of the region as a whole. The area discussed mainly lies within Turkey, Cyprus and Syria. Section 1 is made up of a small number of papers that are mainly concerned with the Pontide belt of northern Turkey. Section 2 is concerned with the geological development of the Tauride and Anatolide belts of central and southern Anatolia, especially the Triassic–Jurassic period of rifting and passive margin development and the Late Cretaceous period of ophiolite genesis and emplacement. Section 3 is mainly concerned with the formation of sedimentary basins during closure of several Mesozoic ocean basins and the related structural development during Late Cretaceous to Pliocene time. Finally, Section 4 is devoted to aspects of the structural development of the region, mainly during the Pliocene–Quaternary (i.e. neotectonics) when the plate configuration was essentially as it is today. The area covered by each paper is shown in Figure 1. The introduction by Robertson et al. covers the southern part of Anatolia and the adjacent easternmost Mediterranean region that was the main subject of the international conference. The main focus is on Late Permian–Recent time. A review of the Late Precambrian–Recent geological development of the easternmost Mediterranean region is published elsewhere (Robertson et al. 2012). The authors discuss alternative interpretations of the Mesozoic–Cenozoic inter-relations of the various crustal units that make up the region. In particular, they consider whether these should be interpreted as individual microcontinents separated by Mesozoic small ocean basins or as parts of larger continental units (i.e. microcontinents). The Anatolides in the north are generally interpreted as the metamorphosed equivalents of the Taurides, although different reconstructions exist. The Anatolides are commonly seen as the northern, leading edge of the Mesozoic Tauride–Anatolide continent that subducted and underwent high-pressure/lowtemperature (HP/LT) metamorphism during Late Cretaceous–Early Cenozoic time. The Anatolides are divided into two parts, namely the HP/LTmetamorphosed Afyon–Bolkar Dag zone in the south, which can be closely correlated with the Taurides, and the very HP/LT Tavsanli Zone further north, which also shows some affinities with the Taurides but is less well understood. The Kirsehir Massif is interpreted as a rifted continental block that was separated from a larger Tauride continent to the south by a Mesozoic oceanic basin known as the Inner-Tauride Ocean. However, uncertainties remain, including the reconstruction