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.
Fault scarps in carbonates are structures well suited to 36 Cl analysis of paleoearthquakes to reconstruct the seismic history using cosmogenic 36 Cl. In this study, we measured cosmogenic 36 Cl concentrations in 117 samples along one of the active faults in Western Anatolia, the Priene-Sazlı Fault scarp, to reconstruct the age of paleoearthquakes along with their slip amounts, beyond the available historical and instrumental archives. Our results indicate four periods of high seismic activity on the Priene-Sazlı Fault since the early Holocene at 8.
The Havran-Balıkesir Fault Zone (HBFZ) is one of the major active structures of the Southern Marmara Region, which has been shaped by the southern branch of North Anatolian fault since the Pliocene. HBFZ is a 10-12 km wide, 120 km long, right-lateral strike-slip fault zone that consists of two ENE-striking main faults, namely, the Havran-Balya and Balıkesir faults. The 90-km-long Havran-Balya fault exhibits right-stepping en echelon geometry and is made up of (1) Havran, (2) Osmanlar, (3) Turplu and (4) Ovacık fault segments. On the eastern part, the 70-km-long Balıkesir fault is divided into two fault segments; (1) Gökçeyazı and (2) Kepsut. We estimated the long-term slip rate between 3.59 and 3.78 mm/yr using river offset. The Kepsut, Gökçeyazı and Ovacık fault segments are capable of generating an earthquake with a moment magnitude of up to 7.2. Detailed palaeoseismological studies show that the HBFZ is responsible for some surface faulting earthquakes with an average recurrence interval of 1000-2000 years during the late Holocene. Considering the fact that there was no evidence of a surface-ruptured earthquake for 2000 years, it can be stated that there is a seismic gap on the Gökçeyazı fault segment.
The Edremit Fault Zone (EFZ) forms one of the southern segments of the North Anatolian Fault Zone (NAFZ) at the northern margin of the Edremit Gulf (Biga Peninsula, South Marmara Region, Turkey). Stratigraphic, structural and kinematic results indicate that basinward younging of the fault zone, in terms of a rolling-hinge mechanism, has resulted in at least three discrete Miocene to Holocene deformational phases: the oldest one (Phase 1) directly related to the inactive Kazdağ Detachment Fault, which was formed under N-S trending pure extension; Phase 2 is characterised by a strike-slip stress condition, probably related to the progression of the NAFZ towards the Edremit area in the PlioQuaternary; and Phase 3 is represented by the high-angle normal faulting, which is directly interrelated with the last movement of the EFZ. Our palaeoseismic studies on the EFZ revealed the occurrence of three past surface rupture events; the first one occurred before 13178 BC, a penultimate event that may correspond to either the 160 AD or 253 AD historical earthquakes, and the youngest one can be associated with the 6 October 1944 earthquake (M w = 6.8). These palaeoseismic data indicate that there is no systematic earthquake recurrence period on the EFZ.
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