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JOURNAL OF STRUCTURAL GEOLOGY, vol.127, 2019 (SCI-Expanded, Scopus)
The central Menderes Massif in western Turkey is a bivergent metamorphic core complex characterised by two detachment faults that operated with opposite sense of shear. Here, we present K-Ar ages and hydrogen isotope data for fault gouge as well as fission track and (U-Th)/He ages for apatite and zircon from bedrock samples to constrain the timing of detachment faulting. Comparison of the K-Ar ages and low-temperature thermochronologic ages indicates brittle faulting at temperatures between similar to 240 and similar to 70 degrees C. At the western termination of the Gediz detachment, K-Ar ages between similar to 12 and similar to 5 Ma suggest rather continuous faulting since the mid-Miocene; a Pliocene phase of rapid slip is mainly recorded in the eastern part of this detachment. In contrast, K-Ar ages from the Buyuk Menderes detachment cluster at 22-16 and 9-3 Ma and provide evidence for two phases of faulting, which is in accordance with new and published low-temperature thermochronologic data. Hydrogen isotope ratios of -76 to -115 parts per thousand indicate infiltration of meteoric water during detachment faulting and gouge formation. The youngest K-Ar ages and cooling histories for hanging and footwall rocks imply that the activity of both detachments ended similar to 3 Ma ago when the currently active grabens were established.