Browsing by Author "Koc, Ayten"

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Late Neogene Oroclinal Bending in the Central Taurides: a Record of Terminal Eastward Subduction in Southern Turkey
(Elsevier Science Bv, 2016) Koc, Ayten; van Hinsbergen, Douwe J. J.; Kaymakci, Nuretdin; Langereis, Cornelis G.
The Tauride fold-thrusts belt formed during similar to S-N convergence between Africa and Eurasia since Cretaceous time. The western end of the central Taurides strike NW-SE, highly obliquely to the overall convergence direction, and connect to the NE-SW Beydaglan-Lycian Nappe flank of the western Taurides, forming the so-called 'Isparta Angle'. In Neogene time, the western and central Taurides and the inner part of the Isparta Angle became overlain by Neogene sedimentary basins including Manavgat, Koprucay and Aksu, characterized by marine clastics and carbonates. The eastern limb of the Isparta Angle experienced multidirectional Miocene to Present extension, whereas E-W shortening affected the marine sedimentary basins in the heart of the Isparta Angle. To quantitatively reconstruct the Neogene kinematic evolution of the Taurides, towards restoring the subduction system accommodating Africa-Eurasia convergence, we paleomagnetically assess if and when vertical axis rotations affected the Manavgat, Koprucay, and Aksu basins in Early Miocene to Pliocene times. We show that the northern Koprucay Basin rotated similar to 20-30 degrees clockwise, the Manavgat Basin underwent similar to 25-35 degrees counterclockwise rotation, and the Aksu Basin underwent no rotation since the Early-Middle Miocene. It was previously shown that the Beydaglari region underwent a post-Middle Miocene similar to 20 degrees counterclockwise rotation. These results show that the prominent oroclinal salient geometry of the western Taurides thus acquired, at least in part, since Miocene times, that the Koprucay Basin rotated relative to the Aksu Basin along the Aksu thrust, and that the Beydaglari platform rotated relative to the Aksu Basin along the Bucak thrust, which must have both been active until Late Neogene time. This synchronous E-W shortening in the heart of the Isparta Angle, and multidirectional extension in its eastern limb may be explained by relative westward retreat of an eastward dipping subducting Antalya slab that has previously been imaged by seismic tomography and a Benioff zone. The Neogene Bucak thrust west of the Aksu Basin may represent the most recent surface expression of the Antalya subduction zone. (C) 2015 Elsevier B.V. All rights reserved.
Lithological Mapping of the Ayhan Basin (Central Anatolia) and Geological Implications: an Integration of Remote Sensing and Field Surveys
(Tmmob Jeoloji Muhendisleri Odasi, 2021) Koc, Ayten
The Central Anatolian Crystalline Complex (CACC), consisting of metamorphic rocks, ophiolites, and magmatic intrusions, is the largest metamorphic complex in Turkey. It is also one of the key areas for reconstruction of the subduction zones, accommodating the Africa-Europe convergence since the Cretaceous in the Eastern Mediterranean. The Ayhan Basin, chosen as the study area, is a supra-detachment basin that developed on the CACC. It has basin infill with an age ranging from Paleocene to Quaternary, interrupted by angular unconformities, and is expected to contain the whole geological record of tectonic mechanisms which have affected the region from Paleocene to Recent times. Producing a well-defined lithological map showing the structural elements of the basin is very important to understand the geological evolution of the Ayhan Basin and also to determine the spatial and temporal effects of the triggering mechanisms which deform the CACC. For this purpose, optical satellite image (Landsat TM and ASTER) processing techniques (pan-sharpening, resampling, principal component analysis, decorrelation stretching, and band combination), which have a widespread application, were used in determination of the lineaments and lithological units, having different reflectance values. After this, detailed lithostratigraphy and geological mapping of the Ayhan Basin were created by field verification. Considering the reconstructed stratigraphy and the geological map of the Ayhan Basin based on field observation and remotely sensed data, it has a depositional system that starts with continental deposits before Lutetian, then continues with marine sediments during the Eocene, and again ends with continental deposits. When the deformation processes are evaluated based on the trigger mechanisms of the Central Anatolian Crystalline Complex's (CACC) evolution, the northern and southern part of the CACC show clearly different processes. Accordingly, the boundary of the impact zone of the subduction zones in the north and south of the CACC is located between the Cicekdag and Ayhan basins.
A Miocene Onset of the Modern Extensional Regime in the Isparta Angle: Constraints From the Yalva‡ Basin (Southwest Turkey)
(Springer, 2016) Koc, Ayten; Kaymakci, Nuretdin; van Hinsbergen, Douwe J. J.; Vissers, Reinoud L. M.
The pre-Neogene Tauride fold-and-thrust belt, comprising Cretaceous ophiolites and metamorphic rocks and non-metamorphic carbonate thrust slices in southern Turkey, is flanked and overlain by Neogene sedimentary basins. These include poorly studied intra-montane basins including the Yalva double dagger Basin. In this paper, we study the stratigraphy, sedimentology and structure of the Yalva double dagger Basin, which has a Middle Miocene and younger stratigraphy. Our results show that the basin formed as a result of multi-directional extension, with NE-SW to E-W extension dominating over subordinate NW-SE to N-S extension. We show that faults bounding the modern basin also governed basin formation, with proximal facies close to the basin margins grading upwards and basinwards into lacustrine deposits representing the local depocentre. The Yalvac Basin was a local basin, but a similar, contemporaneous history recently reconstructed from the AltA +/- napa Basin, similar to 100 km to the south, shows that multi-directional extension dominated by E-W extension was a regional phenomenon. Extension is still active today, and we conclude that this tectonic regime in the study area has prevailed since Middle Miocene times. Previously documented E-W shortening in the Isparta Angle along the Aksu Thrust, similar to 100 km to the southwest of our study area, is synchronous with the extensional history documented here, and E-W extension to its east shows that Anatolian westwards push is likely not the cause. Synchronous E-W shortening in the heart and E-W extension in the east of the Isparta Angle may be explained by an eastwards-dipping subduction zone previously documented with seismic tomography and earthquake hypocentres. We suggest that this slab surfaces along the Aksu thrust and creates E-W overriding plate extension in the east of the Isparta Angle. Neogene and modern Anatolian geodynamics may thus have been driven by an Aegean, Antalya and Cyprus slab segment that each had their own specific evolution.
Miocene Tectonic History of the Central Tauride Intramontane Basins, and the Paleogeographic Evolution of the Central Anatolian Plateau
(Elsevier, 2017) Koc, Ayten; Kaymakci, Nuretdin; Van Hinsbergen, Douwe J. J.; Kuiper, Klaudia F.
Marine Lower-Upper Miocene deposits uplifted to > 2 km elevation in the Tauride mountains of southern Turkey are taken as evidence for the rise of a nascent plateau. The dynamic causes of this uplift are debated, but generally thought to be a regional dynamic topographic effect of slab motions or slab break-off. Immediately adjacent to the high Tauride mountains lie the Central Tauride Intramontane Basins, which consist of Miocene and younger fluvio-lacustrine basins, at much lower elevations than the highly uplifted marine Miocene rocks. These basins include the previously analyzed Altinapa and Yalvac basins, as well as the until now undescribed rigin Basin. In this paper, we aim to constrain the paleogeography of the Central Tauride Intramontane Basins and determine the role of the tectonics driving the formation of the high Miocene topography in southern Turkey. Therefore, we provide new data on the stratigraphy, sedimentology and structure of the continental Ilgin Basin. We provide an 40Ar/39Ar age of 11.61 +/- 0.05 Ma for pumice deposits in the stratigraphy. We provide paleostress inversion analysis based on growth faults showing that the basin formed during multi-directional extension, with NE-SW to E-W dominating over subordinate N-S extension. We conclude that major, still-active normal faults like the Aksehir Fault also controlled Miocene Ilgin basin formation, with proximal facies close to the basin margins grading upwards and basinwards into lacustrine deposits representing the local depocenter. The Ilgin Basin was a local depocenter, but it may have connected with the adjacent Altinapa Basin during high lake levels in late Serravallian time. The Ilgin Basin and the other continental basins provide key constraints on the paleogeography and tectonic history of the region. These continental basins were likely close to the paleocoastline during the Late Miocene after which there must have been major differential uplift of the Taurides. We suggest that the extension we documented in the Central Tauride intramontane basins are in part responsible for the major topography that characterizes the Central Taurides today. The causes of extension remain engmatic, but we suggest that the tomographically imaged Antalya Slab may have caused the contemporaneous formation of NE-SW trending syn-contractional basins in the west and NW-SE trending Central Tauride intramontane basins in the east by slab retreat. Our study highlights that the Neogene deformation history, and perhabs even active tectonics, may be strongly affected by complex slab geometry in SW Turkey, and that crustal deformation plays an important role in generating the Miocene Tauride topography. The role of this crustal deformation needs to be taken into account in attempts to explain the ride of the Taurides and the evolution of the Anatolian Plateau. Marine Lower-Upper Miocene deposits uplifted to > 2 km elevation in the Tauride mountains of southern Turkey are taken as evidence for the rise of a nascent plateau. The dynamic causes of this uplift are debated, but generally thought to be a regional dynamic topographic effect of slab motions or slab break-off. Immediately adjacent to the high Tauride mountains lie the Central Tauride Intramontane Basins, which consist of Miocene and younger fluvio-lacustrine basins, at much lower elevations than the highly uplifted marine Miocene rocks. These basins include the previously analyzed Altinapa and Yalvac basins, as well as the until now undescribed rigin Basin. In this paper, we aim to constrain the paleogeography of the Central Tauride Intramontane Basins and determine the role of the tectonics driving the formation of the high Miocene topography in southern Turkey. Therefore, we provide new data on the stratigraphy, sedimentology and structure of the continental Ilgin Basin. We provide an 40Ar/39Ar age of 11.61 +/- 0.05 Ma for pumice deposits in the stratigraphy. We provide paleostress inversion analysis based on growth faults showing that the basin formed during multi-directional extension, with NE-SW to E-W dominating over subordinate N-S extension. We conclude that major, still-active normal faults like the Aksehir Fault also controlled Miocene Ilgin basin formation, with proximal facies close to the basin margins grading upwards and basinwards into lacustrine deposits representing the local depocenter. The Ilgin Basin was a local depocenter, but it may have connected with the adjacent Altinapa Basin during high lake levels in late Serravallian time. The Ilgin Basin and the other continental basins provide key constraints on the paleogeography and tectonic history of the region. These continental basins were likely close to the paleocoastline during the Late Miocene after which there must have been major differential uplift of the Taurides. We suggest that the extension we documented in the Central Tauride intramontane basins are in part responsible for the major topography that characterizes the Central Taurides today. The causes of extension remain engmatic, but we suggest that the tomographically imaged Antalya Slab may have caused the contemporaneous formation of NE-SW trending syn-contractional basins in the west and NW-SE trending Central Tauride intramontane basins in the east by slab retreat. Our study highlights that the Neogene deformation history, and perhabs even active tectonics, may be strongly affected by complex slab geometry in SW Turkey, and that crustal deformation plays an important role in generating the Miocene Tauride topography. The role of this crustal deformation needs to be taken into account in attempts to explain the ride of the Taurides and the evolution of the Anatolian Plateau.
New Insights on the Neogene Tectonic Evolution of the Aksu Basin (Se Turkey) From the Anisotropy of Magnetic Susceptibility (Ams) and Paleostress Data
(Pergamon-elsevier Science Ltd, 2020) Wasoo, Muhammad Harbi; Ozkaptan, Murat; Koc, Ayten
The junction between the Aegean and Cyprus arc in the southern Turkey forms a triangular-shaped morphological structure so-called Isparta Angle (IA). In Neogene time, the inner part of the Isparta Angle became overlain by sedimentary basins including Manavgat, Koprucay and Aksu, characterized by marine clastics and carbonates. Aksu Basin, one of these marine basins, provides geological records about the Neogene crustal deformation and stress field in the Eastern Mediterranean region. Therefore, we kinematically assess if and when tectonic stress fields affected the Aksu basin in early Miocene to recent times. For this purpose, Anisotropy of Magnetic Susceptibility (AMS) data (AMS) of cored samples and fault-slip data from the brittle mesoscopic faults were collected. The similar to 490 oriented samples for Anisotropy of Magnetic Susceptibility measurements were analyzed and two different maximum magnetic lineation's directions are recognized; 1) N-S magnetic lineation in Pliocene and 2) from N-S to NW-SE magnetic lineation in the Miocene. The results inferred from more than 1000 fault-slip data collected from 83 different sites combined with AMS results demonstrate that the Aksu Basin developed under four different tectonic phases; 1) similar to E-W extensional phase (related to basin formation), 2) similar to N-S compressional (Lycian) phase, 3) similar to(N)E-(S)W compressional (Aksu) phase and 4) N-S extensional (Recent) phase.
Paleobathymetric Evolution of the Miocene Deposits of the Gombe Sector of the Lycian Foreland and Aksu Basins in Antalya, Turkey
(Tubitak Scientific & Technological Research Council Turkey, 2020) Sis, Fatih Seckin; Kouwenhoven, Tanja; Koc, Ayten; Kaymakci, Nuretdin
The evolution of the Lycian Foreland and Aksu basins are associated with the Africa-Eurasia convergence and collision of intervening continental blocks. Both basins developed around the Beydaglari, a Mesozoic carbonate platform, which constitutes the main component and western limb of the Isparta Angle. The Gombe Basin is an integral part of the Lycian Foreland Basin that comprises mainly Eocene to Late Miocene turbidites, onto which the allochthonous Lycian and Antalya nappes thrust over. The Aksu Basin, however, developed in the inner part of the Isparta Angle and is bounded by the Aksu Thrust in the east. During their evolution, these basins experienced significant bathymetric changes, possibly due to vertical motions and variations in the sediment supply. This study provides a detailed analysis of the paleobathymetric evolution of these basins. This conducted paleobathymetric study was based on the determination of the depositional depth by the abundance ratio of planktonic versus benthic foraminifera, which is the function of the water depth. The percentage of planktonic foraminifera relative to the total foraminifer population (%P) increases from shallow to deep water. However, some benthic foraminifera species are directly affected by the oxygen level of the bottom water, rather than by paleobathymetry, i.e. stress markers, and were discarded in the calculation. Additionally, the dissolution of the foraminifera has the potential for miscalculations, since planktonic foraminifera are more prone to dissolution than benthic ones. Nevertheless, the obtained quantitative results were verified and validated qualitatively by specific benthic depth markers that lived at specific depth ranges. Aksu Basin had a shallowing trend, and the sedimentation rate exceeded the subsidence in the middle of the section. Calculated depths for the Gombe Basin indicated depths around 1000 m, which was contrary to the high sedimentation rates indicated by the turbiditic facies of the basin infills.
Paleostress Inversion of Fault-Slip in the Ayhan Basin, Kırs,ehir , Ehir Block (Turkey) Since the Late Cretaceous: Insights Into the Neotethys Closure
(Pergamon-elsevier Science Ltd, 2024) Koc, Ayten
K & imath;rs,ehir , ehir Block, a large triangular continental domain exposed in Central Anatolia, is surrounded by ophiolitic melanges that mark former subduction zones associated with the closure of the northern and southern branches of the Neotethys Ocean. Notably, the Ayhan Basin, located in the inner part of the block, is one of the few locations containing a geological record from the Upper Cretaceous to the Pliocene. It provides a unique opportunity to examine the crustal deformation and the temporal and spatial stress distribution over the Central Anatolian orogen. This study encompasses a comprehensive analysis of the Ayhan Basin's stratigraphy and structure, combined with the paleostress inversion solutions derived from over 400 fault-slip data. The findings reveal that the Ayhan Basin underwent three distinct tectonic phases: (1) NE-SW extensional phase from Late Cretaceous to Lutetian, which refers to the main basin-forming stress configuration. Importantly, this extensional phase is crucial to delineate the spatial extent of the concurrent collision in the north. (2) N-S compressional phase during the Lutetian, mainly governed by the shortening of the K & imath;rs,ehir , ehir Block. This compressional phase caused the inversion of the inherited normal faults in the basin; and (3) NE-SW extensional phase active since the Late Miocene was accompanied by volcanism and uplift in the region. The Cyprus Slab's southward retreat might be this extension's triggering mechanism. Consequently, the temporal and spatial extent of the tectonic phases and their resultant deformations are crucial for understanding the underlying geodynamic processes and establishing their timing.
Preparing the Ground for Plateau Growth: Late Neogene Central Anatolian Uplift in the Context of Orogenic and Geodynamic Evolution Since the Cretaceous
(Elsevier, 2022) McPhee, Peter J.; Koc, Ayten; van Hinsbergen, Douwe J. J.
Central Anatolia (Turkey) is a small and nascent example of a high orogenic plateau, providing a natural laboratory to study processes driving plateau rise. The 1-km-high plateau interior uplifted since c. 8-5 Ma, with a further phase of kilometre-scale uplift affecting the southern plateau margin since 0.45 Ma. Several causes of plateau rise have been proposed: peeling or dripping delamination of the lithospheric mantle; asthenospheric upwelling through slab gaps created by slab fragmentation or break-off, and; continental underthrusting and crustal shortening below the southern plateau margin. The Neogene history of the plateau has not been diagnostic of the causes of plateau rise. We thus evaluate proposed uplift causes in the context of the Anatolian orogenesis, which formed the plateau lithosphere during subduction since the Cretaceous. We combine this analysis with available constraints on uplift, and geophysical data that illuminate the modern mantle (and crustal) structure. Our analysis suggests that lithospheric dripping, which followed arc magmatism and shortening in the Kirsehir Block (eastern Central Anatolia), is the most likely cause of plateau interior uplift. Lithospheric dripping is, however, an unlikely sole driver of multi-phase uplift along the southern plateau margin. There, underthrusting of the African continental margin, recorded by c. 11-7 Ma thrusting on Cyprus, is a viable cause of uplift since 0.45 Ma, but cannot account for earlier uplift since c. 8-5 Ma. Instead, slab break-off below the southern plateau margin is likely in light of geophysical data. On the SW plateau margin, small-scale peeling delamination of the Central Taurides by the Antalya slab since early Miocene times accounts for >150 km slab retreat with no corresponding upper-plate deformation. A southwest-travelling wave of subsidence and uplift signalled this retreat and may have contributed to coeval oroclinal bending of the western Central Taurides and southeastward thrusting of the Lycian Nappes.
Reply To Comment on "preparing the Ground for Plateau Growth: Late Neogene Central Anatolian Uplift in the Context of Orogenic and Geodynamic Evolution Since the Cretaceous
(Elsevier, 2022) McPhee, Peter J.; van Hinsbergen, Douwe J. J.; Koc, Ayten
Rotations of Normal Fault Blocks Quantify Extension in the Central Tauride Intramontane Basins, Sw Turkey
(Amer Geophysical Union, 2018) Koc, Ayten; van Hinsbergen, Douwe J. J.; Langereis, Cor G.
Quantifying the amount of stretching in extensional basin systems is often challenging in the absence of seismic profiles or boreholes. However, when fault spacing and orientation as well as vertical axis rotation patterns are known, map-view restoration may provide a good estimate of total extension. This integrated structural and paleomagnetic approach provides a relatively straightforward tool in extensional basin restoration and fault zone kinematic analysis. Here we provide results of an extensive paleomagnetic survey of the Neogene Central Tauride intramontane basins (SW Turkey), where previous work revealed a complex array of basin-bounding normal faults and relay ramps. In total, 437 oriented cores were sampled at 43 sites distributed within Miocene-Pliocene continental sedimentary rocks from the Ilgn, Altnapa, Yalvac, and Beyehir basins. Despite the more or less coherent overall strike of the mountain belt and basins, rotations vary from 42 degrees clockwise (Yalvac) to 10 degrees (Beyehir), 21 degrees (Ilgn), and 30 degrees (Altnapa) counterclockwise. We show that the rotation pattern is related to normal faults and lateral variations in fault displacement superimposed on regional rotation patterns. We restore these to estimate a minimum NE-SW horizontal extension of 30-35km across the basin system. As a consequence of our reconstruction, it appears that the Sultandalar range that exposes low-grade metamorphic Paleozoic and Mesozoic rocks of the Geyikda and Bolkarda nappes of the Taurides represents a Miocene extensional core complex. Key Points
Shortening and Extrusion in the East Anatolian Plateau: How Was Neogene Arabia-Eurasia Convergence Tectonically Accommodated
(Elsevier, 2024) van Hinsbergen, Douwe J. J.; Guerer, Derya; Koc, Ayten; Lom, Nalan
Deformation in orogenic belts is typically widely distributed but may be localized to form discrete, fast-moving fault zones enclosing semi-rigid microplates. An example is the Anatolian microplate, which is extruding westwards from the East Anatolian Plateau in the Arabia-Eurasia collision zone along the North and East Anatolian Faults that cause devastating earthquakes, including those of February 6, 2023 in Southeast Anatolia. Here, we summarize the orogenic architecture of the East Anatolian Plateau and its underlying kinematic history since the Cretaceous, and use this to reconstruct the tectonic situation that existed at the onset of and during the development of the Neogene East Anatolian Plateau and the Anatolian microplate. The orogen first formed in the late Cretaceous by subduction-accretion of microcontinental lithosphere below Neotethys oceanic lithosphere. Then, in Paleogene time, the accretionary orogen underwent regional upper plate extension, causing crystalline crust exhumation and deep-marine basin formation. From early Miocene time onwards, the extended orogen shortened again and must have accommodated similar to 350 km of convergence, making crust up to 45 km thick, and causing >2 km of uplift. Since the similar to 13 Ma onset of North Anatolian Fault formation, microplate extrusion absorbed no more than 25 % (similar to 65 km) of Arabia-Eurasia convergence and even during this time alone, >200 km of convergence must have been accommodated by continued similar to N-S shortening. We highlight the need for field studies of the East Anatolian Plateau to identify where and how this major shortening was accommodated, what role it played in plateau rise and the onset and dynamics of microplate extrusion, and to better assess seismic hazards.
Structural Elements and Neogene Lithostratigraphy of the Manavgat Basin (Antalya, Turkey)
(Tmmob Jeoloji Muhendisleri Odasi, 2024) Yilmaz, Yusuf Emrah; Atakul-Ozdemir, Ayse; Koc, Ayten
The Tauride fold-thrusts belt has formed under similar to S-N convergence between the Africa and Eurasian plates since Cretaceous time. This movement also resulted in the development of the complex tectonic structure known as the Isparta Angle. In the Neogene period, the western and central Taurides and the inner part of the Isparta Angle became overlain by marine sedimentary basins (Antalya Basin Complex). The Manavgat Basin is one of these marine basins, and unconformably rests on the Tauride in the north. Basically, the Manavgat Basin has a sedimentation thickness of more than 1 km from the Early Miocene to Pliocene. Hence, it is expected to keep the geological records regarding the crustal deformation, besides the lithostratigraphic records during this time. Lithostratgraphically, seven basic units have been identified in the Manavgat Basin. These are, in line with previous studies; 1) Tepekli Formation (Burdigalian-E. Langhian), 2) Oymapinar Limestone (G. Burdigalian-Langhian), 3) Cakallar Breccia (Langhian), 4) Geceleme Formation (G. Langhian-Serravalian), 5) Karpuzcay Formation (G. Langhian-Tortonian), 6) Pliocene units (Yenimahalle and Kursunlu formations), and 7) Belkis Conglomerate (Quaternary). Biosamples were collected from two different measured sections of the Karpuzcay Formation, and the age of the formation was determined. These show that the Karpuzcay Formation was deposited in a deep marine outer neriticbathyal environment from the Late Langhian to Tortonian. In addition to lithostratigraphic features, structural elements forming the Manavgat Basin were also studied, and the Tortonian aged Cardakkoy Fault was described for the first time in this study. As a result, the presence of two different tectonic regimes in the region was determined. Accordingly, the Manavgat Basin developed under the influence of an extensional tectonic regime before the Tortonian, and of a compressional system during the post-Tortonian. This study indicated that N-S directional convergence between Eurasia and Africa and the kinematics of the fragmented subducted plate under the Isparta Angle should be reevaluated based on these paleostress phases.