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  • 1
    Publication Date: 2011-07-01
    Description: The southern part of the Strandja Massif, northern Thrace, Turkey, comprises a basement of various gneisses, micaschists and rare amphibolite, and a cover of metaconglomerate and metasandstone, separated from each other by a pre-metamorphic unconformity. Metamorphic grade decreases from the epidote–amphibolite facies in the south to the albite–epidote–amphibolite/greenschist-facies transition in the north. Estimated P–T conditions are 485–530°C and 0.60–0.80 GPa in the epidote–amphibolite facies domain, and decrease towards the transitional domain between greenschist- and epidote–amphibolite facies. Rb–Sr muscovite ages range from 162.9 ± 1.6 Ma to 149.1 ± 2.1 Ma, and are significantly older (279–296 Ma) in the northernmost part of the study area. The Rb–Sr biotite ages decrease from 153.9 ± 1.5 Ma in the south to 134.4 ± 1.3 Ma in the north. These age values in conjunction with the attained temperatures suggest that the peak metamorphism occurred at around 160 Ma and cooling happened diachronously, and Rb–Sr muscovite ages were not reset during the metamorphism in the northernmost part. Structural features such as (i) consistent S-dipping foliation and SW to SE-plunging stretching lineation, (ii) top-to-the-N shear sense, and (iii) N-vergent ductile shear zones and brittle thrusts suggest a N-vergent compressional deformation coupled with exhumation. We tentatively ascribe this metamorphism and subsequent diachronous cooling to the northward propagation of a thrust slice. The compressional events in the Strandja Massif were most probably related to the coeval N-vergent subduction/collision system in the southerly lying Rhodope Massif.
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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  • 2
    Publication Date: 2017-09-30
    Description: Before the Late Cretaceous opening of the Black Sea, the Central Pontides constituted part of the southern margin of Laurasia. Two features that distinguish the Central Pontides from the neighbouring Pontide regions are the presence of an extensive Lower Cretaceous submarine turbidite fan (the Cağlayan Formation) in the north, and a huge area of Jurassic–Cretaceous subduction–accretion complexes in the south. The Central Pontides comprise two terranes, the Istanbul Zone in the west and the Sakarya Zone in the east, which were amalgamated before the Late Jurassic (Kimmeridgian), most probably during the Triassic. The basement in the western Central Pontides (the Istanbul Zone) is made up of a Palaeozoic sedimentary sequence, which ends with Carboniferous coal measures and Permo-Triassic red beds. In the eastern Central Pontides, the basement consists of Permo-Carboniferous granites and an Upper Triassic forearc sequence of siliciclastic turbidites with tectonic slivers of pre-Jurassic ophiolite (the Küre Complex). The Küre Complex is intruded by Middle Jurassic granites and porphyries, which constitute the western termination of a major magmatic arc. Upper Jurassic–Lower Cretaceous shallow-marine limestones (the Inaltı Formation) lie unconformably over both the Istanbul and Sakarya sequences in the Central Pontides. Two new measured stratigraphic sections from the Inaltı Formation constrain the age of the Inaltı Formation as Kimmeridgian–Berriasian. After a period of uplift and erosion during the Valanginian and Hauterivian, the Inaltı Formation is unconformably overlain by an over 2 km-thick sequence of Barremian–Aptian turbidites. Palaeocurrent measurements and detrital zircons indicate that the major part of the turbidites was derived from the East European Platform, implying that the Black Sea was not open before the Aptian. The Cağlayan turbidites pass northwards to a coeval carbonate–clastic shelf exposed along the present Black Sea coast. In the southern part of the Central Pontides, the Lower Cretaceous turbidites were deformed and metamorphosed in the Albian. Albian times also witnessed accretion of Tethyan oceanic crustal and mantle sequences to the southern margin of Laurasia, represented by Albian eclogites and blueschists in the Central Pontides. A new depositional cycle started in the Late Cretaceous with Coniacian–Santonian red pelagic limestones, which lie unconformably over the older units. The limestones pass up into thick sequences of Santonian–Campanian arc volcanic rocks. The volcanism ceased in the middle Campanian, and the interval between late Campanian and middle Eocene is represented by a thick sequence of siliciclastic and calciclastic turbidites in the northern part of the Central Pontides. Coeval sequences in the south are shallow marine and are separated by unconformities. The marine deposition in the Central Pontides ended in the Middle Eocene as a consequence of collision of the Pontides with the Kırsehir Massif. Supplementary material: The palaeontological data (foraminifera, nannofossil and pollen) are available at: https://doi.org/10.6084/m9.figshare.c.3842359
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 3
    Publication Date: 2019
    Description: 〈span〉The Almacık Block is an approximately 73 km long and 21 km wide tectonic sliver formed by the North Anatolian Fault Zone in northwestern Turkey. Morphologically, it is one of the most pronounced structures along the North Anatolian Fault Zone. All the segments bounding the Almacık Block were ruptured during the second half of the 20th century. The fifty-four apatite (U–Th)/He ages we obtained showed that the region including the Almacık Block was exhumed during the Oligo–Miocene interval and then original exhumation pattern was distorted by the North Anatolian Fault Zone during the Miocene to recent. To interpret this distortion and to reconstruct it to the original state, we modelled “Λ”-shaped mountain fronts in the most probable deformation scenarios. The block has been tilted southward about an approximately east–west-trending horizontal (slightly dipping to the east) axis. As a result of this rotation, the northern part of the block has been uplifted about 2800 m, whereas the southern part has subsided about 430 m, likely during the last 2.5 Myr. The exhumation in the studied region started at around 34 Ma and lasted until 16 Ma with a mean exhumation rate of about 60 m/Myr.〈/span〉
    Print ISSN: 0008-4077
    Electronic ISSN: 1480-3313
    Topics: Geosciences
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  • 4
    Publication Date: 2019
    Description: 〈span〉The Suluova Basin is a prominent member of the wide transtensional Amasya Shear Zone located at the central part of the North Anatolian Shear Zone. This basin is crucial and provides well-resolved data to understand the evolution of transtensional tectonic zones as well as the morphological and paleoenvironmental changes of North Anatolia during the Quaternary. Analysis of detailed stratigraphical sections, faulting data, and mammal paleontology reveals that the Suluova Basin has started to evolve as a closed half-graben along the NW–SE-trending, SW-dipping basin bounding fault zone with normal slip in the early Quaternary. Initial sedimentation mode of the basin was dominated by alluvial fan facies associations. Progressive basin subsidence resulted in an expansion of a freshwater lake at the basin depocenter as faults propagated westwards. Further extensions in the basin were caused to initiate the E–W-trending southern tectonic boundary. Newly created accommodation space hosted a vast freshwater lake during the Calabrian (∼1.8–0.78 Ma) acting as a refugia for a rich faunal assemblage of large and small land mammals. The conditions prior to the onset of Middle Pleistocene (MIS19, ∼0.79 Ma) is marked with increasing regional erosion where paleo-Lake Suluova was captured by the regional river system. Synchronously, the next phase of the shear zone formation was introduced with E–W-trending dextral and NE–SW-trending sinistral strike-slip faults, cross-cutting the former basin structure, forming new depocenters. These faults are still active with noticeable seismic activity and comprise future risks for the major cities of the region.〈/span〉
    Print ISSN: 0008-4077
    Electronic ISSN: 1480-3313
    Topics: Geosciences
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  • 5
    Publication Date: 2013-12-13
    Print ISSN: 0263-4929
    Electronic ISSN: 1525-1314
    Topics: Geosciences
    Published by Wiley
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  • 6
    Publication Date: 2011-01-19
    Description: The southern part of the Strandja Massif, northern Thrace, Turkey, comprises a basement of various gneisses, micaschists and rare amphibolite, and a cover of metaconglomerate and metasandstone, separated from each other by a pre-metamorphic unconformity. Metamorphic grade decreases from the epidote–amphibolite facies in the south to the albite–epidote–amphibolite/greenschist-facies transition in the north. Estimated P–T conditions are 485–530°C and 0.60–0.80 GPa in the epidote–amphibolite facies domain, and decrease towards the transitional domain between greenschist- and epidote–amphibolite facies. Rb–Sr muscovite ages range from 162.9 ± 1.6 Ma to 149.1 ± 2.1 Ma, and are significantly older (279–296 Ma) in the northernmost part of the study area. The Rb–Sr biotite ages decrease from 153.9 ± 1.5 Ma in the south to 134.4 ± 1.3 Ma in the north. These age values in conjunction with the attained temperatures suggest that the peak metamorphism occurred at around 160 Ma and cooling happened diachronously, and Rb–Sr muscovite ages were not reset during the metamorphism in the northernmost part. Structural features such as (i) consistent S-dipping foliation and SW to SE-plunging stretching lineation, (ii) top-to-the-N shear sense, and (iii) N-vergent ductile shear zones and brittle thrusts suggest a N-vergent compressional deformation coupled with exhumation. We tentatively ascribe this metamorphism and subsequent diachronous cooling to the northward propagation of a thrust slice. The compressional events in the Strandja Massif were most probably related to the coeval N-vergent subduction/collision system in the southerly lying Rhodope Massif.
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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