Structural and kinematic analysis of a transpressional basin: Çiçekdağ Basin

The Central Anatolian Crystalline Complex (CACC), which lies within Turkish Alpine orogenic belt, incorporates several basins located either within the complex or at and along its boundaries. Many of the basins developed during extension since Late Cretaceous and then evolved with advancing collision of Anatolide-Tauride with Pontides. With regard to deformation and evolution of the region, recent paleomagnetic study from the central Anatolian intrusives defines three blocks with characteristic rotation, pointing out the break-up of the CACC and the formation of two deformation zones between blocks. This study is focused on Çiçekdag Basin (ÇB) which is located within ˘ one of the intensely deformed zones in the CACC. The structural analysis within and around ÇB in support of these models and claims is, however, limited. Thus this present study aims to provide more structural data that bears on the evolution of the Çiçekdagı Basin as well as the CACC, especially during regional contraction taking place at ˘ the end of the Eocene. Major structures of the study area fall into six groups: (i) E-W-trending synclines and a burried major reverse fault, suggesting N-S shortening; (ii) approximately NW-SE-trending plunging en-échelon folds, consistent with NE-SW compression; (iii) a NW-SE-trending (130◦ ) left-lateral strike-slip fault; (iv) E-W-trending (260◦ ) normal fault at southern edge of the basin and NW-SE-trending (∼150◦ ) normal fault; (v) NE-SW-trending reverse faults (∼050◦ -055◦ ) in the north of and middle of the basin, with hanging wall syncline geometry compatible with NWSE to N-S compression; (vi) WNW- ESE trending reverse faults implying nearly N-S compression. At this stage, it is not clear to us if all these structures were encountered within the same strain field or they belong to a poly-phase deformation. This will be evaluated and discussed further

Thermal history and extensional exhumation of a high-temperature crystalline complex (Hirkadağ Massif, Central Anatolia)

The Central Anatolian Crystalline Complex (CACC) is a large continental domain exposed in central Turkey that was affected by high temperature metamorphism during the Late Cretaceous. As a result of this event, Paleozoic sediments became metamorphosed, initially under Barrovian conditions, then overprinted locally by high temperature-low pressure metamorphism, and intruded by widespread batholiths. In this study we focus on the crystalline Hirkadağ Massif located in the central part of the CACC, where we applied an integrated approach involving metamorphic, structural and geochronological analysis in order to elucidate its tectonic history from burial to exhumation. Our metamorphic study reveals that conditions of metamorphism reached ~7-8kbar/700°C and were relatively homogeneous at the scale of the Hirkadağ Massif. Coeval with the regional metamorphism, the rocks were intensely deformed as reflected by isoclinal folding, the development of a pervasive foliation and top-to-the-SE shearing. This was followed by decompression to pressures of ~3-4kbar at 800°C, which may be linked to the emplacement of local granodioritic intrusions at ~77Ma. Subsequent cooling of the Hirkadağ high-grade metamorphic and intrusive rocks is indicated by 40Ar/39Ar cooling ages of 68.8±0.9Ma (biotite) and 67.0±1.2Ma (potassium feldspar). Evidence for tectonic exhumation has been identified within the marbles at the NE margin of the Hirkadağ Massif, in the form of discrete protomylonitic and mylonitic shear bands showing a consistent N40-60 top-to-NE sense of shear. Further east, the contact between brecciated mylonitic marbles and non-metamorphic conglomerates preserves the typical structural features of an upper-crustal detachment fault. Restoration of the Hirkadağ Massif and the CACC to their late Cretaceous configuration suggests that the LP-HT metamorphism, magmatism and extensional structures evolved as a result of the development and exhumation of a ~N-S trending magmatic arc experiencing regional E-W extension above an active subduction zone

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Late Eocene evolution of the Cicekdagi Basin (central Turkey): Syn-sedimentary compression during microcontinent-continent collision in central Anatolia

The Central Anatolian Crystalline Complex (CACC) exposes metasediment rocks overlain by Cretaceous ophiolites and intruded by granitoids. Following late Cretaceous exhumation of its high-grade metamorphic rocks, the CACC started to collide with the Central Pontides of southern Eurasia in the latest Cretaceous to Paleocene. Here, we present the sedimentary, stratigraphic and tectonic evolution of the Cicekdagi Basin, located in the northwest of the CACC. Magnetostratigraphic dating, supported by Ar-40/Ar-39 geochronology, shows a late Eocene basin age. The basin fill unconformably overlies metamorphic basement in the south and ophiolites of the CACC in the north. It consists of red conglomerates, sandstones and siltstones, which overlie a sequence of nummulitic limestones. In the south, these limestones are similar to 10 m thick, are underlain by a few meters of conglomerate unit unconformably covering the CACC metamorphics. In the north, the limestones are underlain by a similar to 200 m thick sequence of volcanics and fine-grained clastics intercalating with shallow marine black shales. The upper Eocene sediments of the Cicekdagi Basin were deformed into a syn-anticline pair. Progressive unconformities in the northern flank and a rapid and persistent similar to 180 degrees switch in paleocurrent directions from southward to northward in the southern flank of the anticline demonstrate syn-sedimentary folding. We interpret the folding to result from a southward progression of the Cankiri foreland basin as a result of ongoing collision between the CACC and the Pontides