Nuretdin Kaymakci

Tectono-stratigraphy of the Çankırı Basin: Late Cretaceous to early Miocene evolution of the Neotethyan Suture Zone in Turkey

Abstract The Çankırı Basin straddles the İzmir–Ankara–Erzincan Suture Zone which demarcates the former position of the northern branch of the Neotethys. It includes more than 3 km of pre-Middle Miocene in-fill related to late Cretaceous to pre-Middle Miocene evolution of the region. The basin has developed on the upper Cretaceous subduction complex and arc related basins of the Neotethys Ocean. The basin fill includes an upper Cretaceous forearc sequence overlain by Paleocene with a local unconformity. The upper Cretaceous configuration of the Çankırı basin is interpreted as a part of a forearc basin. The Paleocene and younger history is interpreted as a foreland sequence dominated by progressively southwards migrated depocenters in front of southward migrating thrust faults upon which a series of piggy-back basins were developed. Termination of the forearc setting and beginning of foreland basin conditions indicates complete subduction of the Neotethyan oceanic crust and onset of collision between the Pontides (Laurasia) and the Taurides (Gondwana) in the Paleocene. Thrusting and related sedimentation continued until the Aquitanian (Early Miocene).

Palaeomagnetic evolution of the Cankiri Basin (central Anatolia, Turkey): implications for oroclinal bending due to indentation

P alaeomagnetic data in combination with palaeostress data and anisotropy of magnetic susceptibility orientations are utilized to develop a tectonic evolutionary model for the Early Tertiary part of the � (omega)-shaped Ca nkiri Basin (Turkey). The results reveal clockwise rotations in the northeast and anticlockwise rotations in the west and southeastern corner of the basin. The magnetic inclinations indicate a northward drift of the Ca nkiri Basin and support an indentation model for the Kirsehir Block. It is proposed that the � -shape of the Cankiri Basin was the result of indentation of the Kirsehir Block into the Sakarya Continent during northwards migration accompanying closure of Neotethys. It appears that the indentation started prior to Eocene and ended before Middle Miocene times.

Dating of the Black Sea Basin: new nannoplankton ages from its inverted margin in the Central Pontides (Turkey)

Abstract The Eocene uplift and inversion of a part of the Black Sea margin in the Central Pontides, allows us to study the stratigraphic sequence of the Western Black Sea Basin (WBS). The revision of this sequence, with 164 nannoplankton ages, indicates that subsidence and rifting started in the Upper Barremian and accelerated during the Aptian. The rifting of the western Black Sea Basin lasted about 40 Ma (from late Barremian to Coniacian). In the inner, inverted, Black Sea margin, the syn-rift sequence ends up with shallow marine sands. The uppermost Albian to Turonian was a period of erosion or non deposition. This regional mid-Cretaceous stratigraphical gap might result from rift flank uplift, as expected in the case of a thick and cold pre-rift lithosphere. However, coeval collision of the Kargi Block, along the North Tethyan subduction zone at the southern margin of the Pontides, might also have contributed to this uplift. A rapid thermal post-rift subsidence of the margin occurred during the Coniacian–Santonian. Collision of the Kirşehir continental block commenced in Early Eocene time (zone NP12) giving rise to compressional deformation and sedimentation in piggyback basins in the Central Pontides, whereas the eastern Black Sea was still opening.

Sedimentary Basin Tectonics from the Black Sea and Caucasus to the Arabian Platform

This wide area of the Alpine–Himalayan belt evolved through a series of tectonic events related to the opening and closure of the Tethys Ocean. In doing so it produced the largest mountain belt of the world, which extends from the Atlantic to the Pacific oceans. The basins associated with this belt contain invaluable information related to mountain building processes and are the locus of rich hydrocarbon accumulations. However, knowledge about the geological evolution of the region is limited compared to what they offer. This has been mainly due to the difficulty and inaccessibility of cross-country studies. This Special Publication is dedicated to the part of the Alpine–Himalayan belt running from Bulgaria to Armenia, and from Ukraine to the Arabian Platform. It includes twenty multidisciplinary studies covering topics in structural geology/tectonics; geophysics; geochemistry; palaeontology; petrography; sedimentology; stratigraphy; and subsidence and lithospheric modelling. This volume reports results obtained during the MEBE (Middle East Basin Evolution) Programme and related projects in the circum Black Sea and peri-Arabian regions.

Late Miocene transcurrent tectonics in NW Turkey: evidence from palaeomagnetism and 40Ar–39Ar dating of alkaline volcanic rocks

A number of intra-continental alkaline volcanic sequences in NW Turkey were emplaced along localized extensional gaps within dextral strike-slip fault zones prior to the initiation of the North Anatolian Fault Zone. This study presents new palaeomagnetic and 40 Ar- 39 Ar geochronological results from the lava flows of NW Turkey as a contribution towards understanding the Neogene- Quaternary tectonic evolution of the region and possible roles of block rotations in the kinematic history of the region. 40 Ar- 39 Ar analyses of basalt groundmass indicate that the major volume of alkaline lavas of NW Turkey spans about 4 million years of episodic volcanic activity. Palaeomagnetic results reveal clockwise rotations as high as 73 ◦ in Thrace and 33 ◦ anticlockwise rotations in the Biga Peninsula. Movement of some of the faults delimiting the areas of lava flows and the timing of volcanic eruptions are both older than the initiation age of the North Anatolian Fault Zone, implying that the region experienced transcurrent tectonics during Late Miocene to Pliocene times and that some of the presently active faults in the region are reactivated pre-existing structures.

Kinematic and structural development of the Çankiri Basin (Central Anatolia, Turkey): a paleostress inversion study

Three different deformation phases have been recognized in the southern part of the Cankiri Basin from (1) the major structures and (2) through using paleostress inversion techniques for fault slip data. The deformation phases recognized from the paleostress data are correlated with those recognized from the major structures and dated accordingly. The first phase occurred in the Late Paleocene to pre-Burdigalian and is characterized by an oblique r2 and NNE-SSW to NE-SW trending subhorizontal r1 and WNW-ESE to NW-SE trending r3 patterns which indicate transcurrent deformation associated with a combination of thrusting and strike slip faulting (transpression) possibly due to indentation of the Kirsehir Block to the Sakarya Continent. The second phase occurred from the Burdigalian to the Serravallian and is characterized by a subvertical r1 and oblique r2 and r3, which indicate oblique extension associated with normal faulting possibly due to a post-orogenic collapse. The third deformation phase is characterized by a vertical r2 while the other stresses were horizontal, which indicate regional transcurrent tectonics, which is correlated with the current transcurrent tectonics controlled by the North Anatolian Fault Zone. D 2003 Elsevier Science B.V. All rights reserved.

Late Cretaceous to Recent kinematics of SE Anatolia (Turkey)

Abstract Five different deformation phases have been recognized in the SE Anatolian orogen and the Arabian Platform based on palaeostress inversion studies using fault-slip data sets. The timing and duration of these phases are determined using various criteria including the age of the affected strata, syndepositional structures, cross-cutting structures and overprinting slickensides. The oldest deformation phase is characterized generally by NE–SW-directed extension. The extension is thought to have resulted from slab-roll back processes during the Maastrichtian to Middle Eocene interval (c. 60 Ma to 40–35 Ma). The second deformation phase is characterized by east–west to NW–SE-directed compression and thought to result from cessation of roll-back processes possibly due to subduction of younger oceanic crust or increase in the convergence rate between Africa and Eurasia during the post-Middle Eocene to Late Oligocene interval (c. 40–35 Ma to 25 Ma). The third deformation phase is characterized by east–west to NW–SE-directed extension possibly due to slab detachment that initiated in Iran and migrated westwards during the latest Oligocene to Middle Miocene period (25–11 Ma). The fourth deformation phase is characterized by approximately north–south-directed compression due to collision and further northwards indentation of Arabian Plate by the end of Middle Miocene (11–3.5 Ma). The fifth and present deformation phase is characterized by NE–SW compression which might result from tectonic re-organization in the region since the Middle Pliocene (c. 3.5 Ma to recent).

Tectonic evolution and paleogeography of the Kırşehir Block and the Central Anatolian Ophiolites, Turkey

In Central and Western Anatolia two continent-derived massifs simultaneously underthrusted an oceanic lithosphere in the Cretaceous and ended up with very contrasting metamorphic grades: high pressure, low temperature in the Tavsanli zone and the low pressure, high temperature in the Kirsehir Block. To assess why, we reconstruct the Cretaceous paleogeography and plate configuration of Central Anatolia using structural, metamorphic, and geochronological constraints and Africa-Europe plate reconstructions. We review and provide new 40Ar/39Ar and U/Pb ages from Central Anatolian metamorphic and magmatic rocks and ophiolites and show new paleomagnetic data on the paleo-ridge orientation in a Central Anatolian Ophiolite. Intraoceanic subduction that formed within the Neotethys around 100–90 Ma along connected N-S and E-W striking segments was followed by overriding oceanic plate extension. Already during suprasubduction zone ocean spreading, continental subduction started. We show that the complex geology of central and southern Turkey can at first order be explained by a foreland-propagating thrusting of upper crustal nappes derived from a downgoing, dominantly continental lithosphere: the Kirsehir Block and Tavsanli zone accreted around 85 Ma, the Afyon zone around 65 Ma, and Taurides accretion continued until after the middle Eocene. We find no argument for Late Cretaceous subduction initiation within a conceptual “Inner Tauride Ocean” between the Kirsehir Block and the Afyon zone as widely inferred. We propose that the major contrast in metamorphic grade between the Kirsehir Block and the Tavsanli zone primarily results from a major contrast in subduction obliquity and the associated burial rates, higher temperature being reached upon higher subduction obliquity.

Neotectonics of the southeast Marmara region, NW Anatolia, Turkey

The North Anatolian Fault Zone (NAFZ) bifurcates into three branches in the Marmara Region, which is a transition zone between the strike– slip tectonics manifested by the NAFZ and the N– S directed extensional regime of western Anatolia. The southern Marmara region is characterized by the middle and the southern branches while the northern branch controls the north Marmara region. The south Marmara region is characterized by approximately E – W trending rhomb-like horst and graben complexes bounded by strike slip-faults with normal component, striking mainly in E – W direction. This study documents the geometry and the structural characteristics of the NAFZ in the southeast Marmara region and discusses the commencement age of the strike– slip tectonics using deformation patterns of Neogene units and information available in the literature. q 2002 Elsevier Science Ltd. All rights reserved.

Lithospheric structural control on inversion of the southern margin of the Black Sea Basin, Central Pontides, Turkey

To illustrate the structural evolution of the Black Sea Basin in the context of Neotethyan subduction and subsequent continental collisions, we present the first lithosphere-scale, ∼250-km-long, balanced and restored cross section across its southern continental margin, the Central Pontides. Cross-section construction and restoration are based on field, seismic-reflection, geophysical, and apatite fission-track data. The structure of the onshore Pontides belt is predominantly controlled by inverted normal faults, whereas the offshore areas are devoid of large structural inversion. The restored section indicates that Cretaceous crustal thinning occurred synchronously with (probably buoyancy-driven) exhumation of a forearc high-pressure blueschist wedge likely during Neotethyan slab retreat. Apatite fission-track data show that structural inversion of the forearc zone, which formed the Central Pontides fold-and-thrust belt, started at ca. 55 Ma. This Eocene structural inversion followed upon collision of the Kirs¸ehir continental block and the arrest of Neotethyan oceanic subduction below the Central Pontides. Compared to the Central Pontides belt, which underwent significant shortening (∼28 km, i.e., ∼33%), the relatively colder and stronger Black Sea lithosphere prevented the northern offshore areas from undergoing inversion. We propose that the location of Cenozoic contractional deformation is related to the absence of lithospheric mantle below the southern Pontides (forearc) zone as a consequence of the Cretaceous high-pressure wedge exhumation.