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Mediterranean Geoscience Reviews, 2025 (Scopus)
Isparta Angle (IA) is a significant structure within the Southwest Anatolian Extensional Domain of Türkiye and comprises poorly studied active grabens such as Karamık Graben (KG). KG is a 6–17-km-wide, 29-km-long active depression serving as a key feature for understanding the evolution of the IA. This study investigates the neotectonic characteristics of the KG using an integrative approach combining field mapping, stratigraphic sections, borehole data, and fault-slip analysis. The graben exhibits two distinct fills separated by an angular unconformity: (1) a deformed latest Early Miocene–Late Pliocene infill by the short-term NE–SW-directed compression (Phase-I extension), and (2) an undeformed Quaternary infill (Phase-II extension). A larger lake basin developed during the Phase-I extension and was restricted to a smaller area during the neotectonic period due to step faulting. Fault-slip data indicate that the present tectonic regime is characterized by multi-directional (radial) extension. Deposition rates calculated from the borehole and stratigraphic sections are 0.06 mm/year for the Quaternary units, 0.02 for the Türkbelkavak Fm, and 0.06 mm/year for the Akın Fm, while the underestimated averaged vertical slip rates are 0.170 mm/year for the Quaternary units, 0.02 mm/year for the Türkbelkavak Fm, and 0.06 mm/year for the Akın formation. We also suggest that both vertical slip and deposition rates have become faster during the Quaternary. Based on all these findings, the onset of the neotectonic regime is Early Quaternary in the region. We interpret the Phase-I extension resulted from the slab retreat/tear of the Aegean subducting slab, with a subsequent contraction phase likely tied to the final stage of the Aksu Thrust (Late Miocene to the Pliocene). The Phase-II extension is attributed to the slab-retreat/tearing and tectonic escape of the Anatolian platelet since the Late Pliocene/Early Quaternary. The northern margin-boundary faults of the KG were reactivated by two successive moderate earthquakes (Mw = 6.5 and Mw = 6.2) on February 3, 2002, known as the Çay Earthquakes. However, the rest seems active, as evidenced by the findings of this study, and implies a seismic gap. The possible earthquakes to be sourced from the southern section of the Devederesi, Akkonak, and Karacaören Fault Zones are estimated as maximum Mw = 6.5, 6.5, and 6.6, respectively.