Structural analyses along selected transects across the Menderes Massif and incorporation of existing data have resulted in a synthetic cross section across southwestern Turkey. The tectonic interpretation has been combined with 40 Ar/ 39 Ar laser-probe experiments on two syn-kinematic white mica populations, which, respectively, predate and overprint documented Early Miocene deformational fabrics. Our results indicate that the regional extension had initiated by Eocene±Oligocene times. A 362 Ma 40 Ar/ 39 Ar age derived from white mica which formed during a regionally observed, northward-directed tectonic transport suggests that the extension was contemporaneous with the tectonic emplacement of mid-crustal continental basement. Alternatively, the age may relate to the regional cooling of the basement sequence, and thus postdates the tectonic emplacement. In the latter scenario, the analysis fails to solve the present ambiguity on the Pan-African or Alpine affinity of the northward-directed transport. Further exhumation of basement rocks is characterized by a dominant displacement along the north-dipping Gediz Detachment at the northern margin of the massif, which developed under ductile conditions in the Early Miocene by partial exploitation of older zones of weakness, which originated from an earlier phase of basement emplacement. Youngest (semi)ductile activity along the Gediz Detachment has been recorded as having a 71 Ma 40 Ar/ 39 Ar age derived from syn-kinematic white mica in the top of the detachment. Following the initiation of the ductile Gediz Detachment, an antithetic, semibrittle, and south-dipping Büyük Menderes Detachment had developed in the center of the massif, which, together with the Gediz Detachment, accommodated further doming of the central part of the Menderes Massif and controlled the architecture of the surrounding supradetachment basins.

Western Turkey is one of the most spectacular regions of widespread active continental extension in the world. The most prominent structures of this region are E–W-trending grabens (e.g. Gediz and Büyük Menderes grabens) and intervening horsts, exposing the Menderes Massif. This paper documents the result of a recent field campaign (field geological mapping and structural analysis) along the southern margin of the modern Gediz Graben of Pliocene (∼ 5 Ma) age. This work provides field evidence that the presently low-angle ductile-brittle detachment fault is cut and displaced by the high-angle graben-bounding normal faults with total displacement exceeding 2.0 km. The evolution of the N–S extension along the Gediz Graben occurred during two episodes, each characterized by a distinct structural styles: (1) rapid exhumation of Menderes Massif in the footwall of low-angle normal fault (core-complex mode) during the Miocene; (2) late stretching of crust producing E–W grabens along high-angle normal faults (rift mode) during Pliocene–Quaternary times, separated by a short-time gap. The later phase is characterized by the deposition of now nearly horizontal sediments of Pliocene age in the hanging walls of the high-angle normal faults and present-day graben floor sediments. The evolution of extension is at variance with orogenic collapse and/or back-arc extension followed by the combined effect of tectonic escape and subduction rollback processes along the Aegean-Cyprean subduction zone. Consequently, it is misleading to describe the Miocene sediments exhumed on shoulders of the Gediz Graben as simple graben fill.

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The Kocac°ay Basin (KC°B) is a key area in western Anatolia^a well-known extended terrane where regional segmentation has received limited attention^for investigating strike-slip faults kinematically linked to detachment faults. In this paper, we present results of an integrated sedimentologic, stratigraphic, and structural study of Miocene alluvial fan/fan-delta/lacustrine deposits that accumulated in the KC°B, a NE-trending basin with connections to the Menderes Metamorphic Core Complex (MCC).We mapped and evaluated most of the key faults in the KC°B, many for the ¢rst time, and recognised di¡erent deformation events in the study area near the E margin of the MCC.We also present ¢eld evidence for kinematic connections between low-angle normal and strike-slip faults which were developed in an intermittently active basement-involved transfer zone in western Anatolia.We ¢nd that the KC°B contains a detailed record of Miocene transtensional sedimentation and volcanism that accompanied exhumation of the MCC. Structural data reveal that the basin was initially formed by transtension (D1 phase) and subsequently uplifted and deformed, probably as a result of early Pliocene wrench-to extension-dominated deformation (D2 phase) overprinted by Plio -Quaternary extensional tectonics (D3 phase).These results are consistent with progressive deformation wherein the axis of maximum extension remained in the horizontal plane but the intermediate and maximum shortening axes switched position in the vertical plane. Combining our results with published studies, we propose a new working hypothesis that the KC°B was a transtensional supradetachment basin during the Miocene.The hypothesis could provide new insights into intermittently active extension-parallel zone of weakness in western Anatolia.These results also suggest that the termination of low-angle normal fault systems within an extension parallel transfer zone may have resulted in a transtensional depressions which are di¡erent from classical supradetachment basins with respect to the sedimentation and deformational pattern of the basin in¢lls. Fig. 2. Simpli¢ed geologic map and cross section of NE-trending Cumaovası Basin and Kocac°ay Basin.The basins were separated by basement uplifts (e.g. the Nifdag ï ı High) during deposition of basin-¢ll units. MFZ, Mahmutdag ï ı Fault Zone; SFZ, Spildag ï ı Fault Zone; KF, KemalpaSa Fault; KTF, Kalkancatepe Fault; OFZ, Orhanlı Fault Zone.

The Lycian molasse basin of SW Turkey is a NE-SW-oriented basin that developed on an imbricated basement, comprising the allochthonous Mesozoic rocks of the Lycian nappes and Palaeocene-Eocene supra-allochthonous sediments. The imbricated basement has resulted from a complex history related to the emplacement of different tectonic units from Late Cretaceous to Late Eocene. Following imbrication, extensional collapse of the Lycian orogen resulted in extensive emergent areas, some of which coincide with present-day mountains. These were surrounded by interconnected depressions, namely, the Kale-Tavas, Çardak-Dazk¬r¬ and Denizli subbasins. The Lycian molasse sequence contains a relatively complete record of the tectonic history of the Lycian orogenic collapse from which it was derived. The sequence is characterised by interdependence between tectonism and sedimentation, the latter of which includes fining-and coarsening-upward sedimentary cycles with syn-depositional intrabasinal unconformities. The Denizli subbasin consists of thick, coarse-grained wedges of alluvial fans and fine-grained fan-delta deposits formed in a shallowmarine environment. Some areas of the fan deltas were colonised by corals, red algae and foraminifera, forming patch reefs. The first phase of extensional collapse in the region is marked by the Lycian orogenic collapse, which may have been initiated by the beginning of the Oligocene (Rupelian), following the main Menderes metamorphism. Starting in the latest Early Miocene or in the Middle Miocene, the area of the molasse basin was subject to deformation with the Lycian nappes, and to erosion as well. At that time, the Lycian nappes, with some ophiolitic assemblages, were thrust over the molasse deposits and thus, NE-SW-trending folds were formed. The molasse deposits and thrust-related deformational structures were then unconformably covered by Upper Miocene continental deposits which belong to the neotectonic period of SW Turkey. The second phase of extensional collapse is marked by granitic intrusions and the formation of Miocene detachment-related extensional basins. This phase may have been related to the exhumation of the gneissic core of the Menderes Massif, from which fragments were derived and incorporated into the upper parts of the Denizli subbasin during the Aquitanian.

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Based on historical and instrumental data, societies in the Eastern Mediterranean and MiddleEast have survived at least 150 large earthquakes (generally M > 6) during the past 2500 yr. Beyond this time span, an earthquake chronology is mostly unknown, which hampers the production of reliable long-term earthquake models. Since the only remaining evidence of seismic activity is a bedrock scarp, cosmogenic 36 Cl is the only suitable nuclide to be applied in the determination of the seismic history and slip rate of an active limestone fault plane. In this study, we focus on the 4-m-high Mugırtepe fault scarp within the active Manisa fault zone in western Anatolia, one of the most seismically active and rapidly extending regions in the world. We analyzed 44 samples in two slightly overlapping strips, which in total covered 2.65 m of the fault scarp. In order to determine the timing and the amount of slip of the paleoseismic events, we analyzed the measured 36 Cl concentrations using the Schlagenhauf Matlab ® code. We used two different scenarios based on two different inherited 36 Cl concentrations as constrained by our data and modeling. The best fi t for the fi rst scenario yields two seismic events, one at 13.7 ± 0.8 ka with a displacement of 0.5 ± 0.2 m and one at 7.8 ± 0.5 ka with 2.15 ± 0.35 m offset. For the second scenario, we obtained a single seismic event at 8.6 ± 0.6 ka with 2.65 ± 0.35 m of slip. These results indicate that the visible part of the Mugırtepe exposed fault scarp had achieved most of its displacement already by 8 ka. Initial surface faulting at Mugırtepe occurred not later than around 14 ka, and marked seismic activity continued until around 8 ka. Our fi rst results from the western Anatolian Extensional Province show the ability to reveal periods of enhanced seismic activity beyond historical data using cosmogenic 36 Cl.

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