Türkiye Jeoloji Bülteni

Abstract: Western Anatolia is widely recognized as one of the fastest-extending continental regions globally, with the Akşehir–Simav Fault System (ASFS) constituting one of the most seismically active structures within this extensional regime. Representing a segment of the Simav Fault Zone, which forms the northwestern section of the ASFS, theBanaz Fault (BF) was re-evaluated in this study based on structural mapping, paleostress analysis of 155 faultslip data collected from 11 locations, and geodetic data. Rather than a single uniform strand, the ~ 37-km-long BFis redefined as a complex, multi-segmented structure comprising the Gürlek, Kızılcaören, and Derbent segments. Paleostress analysis reveals significant spatial and temporal variations in the local stress field. The northwestern Gürlek segment exhibits dominant right-lateral strike-slip character with sub-horizontal σ1 axis. Southeastward, thefault traces a distinct map-view curvature in to the Kızılcaören and Derbent segments, where the σ1 axis transitions to sub-vertical position, shifting the kinematic mechanism to normal and oblique-slip faulting. Superimposed slickenlines at the Evrendede locality preserve a transition from older, pure normal faulting to younger, right-lateral oblique normal faulting, confirming dynamic, counter-clockwise rotation of the σ3 axis over time.Geological and morphotectonic analyses yield a long-term vertical slip rate of 0.1 mm/yr since the PlioQuaternary, which is consistent with contemporary GNSS strain rates (1-2 mm/yr). The active status of the BF is further substantiated by newly-documented ridge-type travertines running strictly parallel to the fault strike (N55°Wand N40°E). Seismic hazard assessments indicate that while individual segments have the capacity to generate earthquakes ranging from Mw = 6.12 to 6.56, full-segment rupture encompassing the entire zone poses a major seismic risk with potential magnitude of Mw = 6.9. Ultimately, this study demonstrates that extensional horsetail structures mature via superimposed extensional phases, structural segmentation control, systematic displacement partitioning, and dynamic local stress variations (axis rotations), mechanisms that directly dictate deep hydrothermal fluid circulation pathways.

Abstract: Northwestern Anatolia contains many active fault segments with different strikes, tectonic regimes andslip rates. In this study, the tectonic control on topography along the Yalakdere Fault, a right-lateral strike-slipfault located south of the Gulf of İzmit, is investigated using a multi-scale morphometric approach. Mountain frontmorphology (Smf, Vf), basin-scale indices (AF, Bs, HI, HC), channel steepness (ksn), and drainage divide stability(χ) analyses are integrated with river profile inversion modeling to constrain the spatial and temporal variability ofuplift. Results reveal significant morphotectonic contrasts between the southwestern and northeastern segments ofthe fault. River profile inversion results show that uplift rates have varied throughout the Pleistocene, with peakuplift occurring during the Early Pleistocene. These findings demonstrate that the morphotectonic evolution of theYalakdere Fault is controlled by fault segmentation, lithological variability and differential uplift. The results furtherindicate that tectonic forcing, rather than climatic variability, represents the dominant control on landscape evolution.

Abstract: The NNE-SSW trending Gelenbe Fault Zone (GFZ), located within the Aegean extensional system, isone of the critical seismotectonic elements constituting the neotectonic structure of Western Anatolia. Extending between the Bigadiç district in Balıkesir and the Akhisar district in Manisa, this active fault system plays a key role in understanding the seismic activity and geodynamic structure of the region. The region exhibits high seismic activityin both historical and instrumental periods, making it a prominent area in terms of earthquake hazard in Türkiye.Based on geological field studies including mapping and fault surface measurements, this study provides detailed data about the surface segment geometry and kinematic character of the GFZ. Field observations and 1/25,000scale mapping studies show that the GFZ is an approximately 8-km-wide zone consisting of two nearly parallel main segments, the Eastern and Western segments, with lengths of 35 km and 36 km, respectively. The Eastern segment comprises four fault splays trending N-S and N10-20°E, while the Western segment consists of five fault splaystrending N-S to N35°E.Kinematic analyses conducted on 132 slip-plane data points collected from 12 distinct locations along thefault zone indicate local stress variations induced by fault bends—resulting from sinuous surface geometries—andthe presence of antithetic and synthetic secondary fractures developed within the shear zone. Paleostress analysis revealed that two distinct tectonic phases were effective in the evolution of the region. NE-SW compression-relatedNW-SE extension represents the Miocene-Early Pliocene compressional regime (Phase 1), while Phase 2 reflectsthe WNW-ESE compression-related NNE-SSW extensional regime effective from the Pliocene to the present. Focal mechanism solutions consistent with Phase 2 confirm that the eastern segment (DK4) of the GFZ was reactivated following the August 10, 2025, Sındırgı earthquake (Mw: 6.1). Furthermore, seismic activity concentrated on boththe primary right-lateral faults and the left-lateral antithetic secondary fractures. All obtained data indicate thatthe GFZ acts as a strategic barrier responsible for the transfer of the extensional regime, acting as a right-lateralstrike-slip transfer structure within the İzmir–Balıkesir Transfer Zone in the current deformation network of Western Anatolia and must be considered to have primary importance in regional seismic risk assessments. 

Abstract: This study evaluates the geothermal resource, metallic ore, industrial raw material, and lignite potentialof the Çan district (Çanakkale), located at the geo-economic focal point of the Biga Peninsula, from the perspective of sustainable resource management based on water-energy-mining nexus. The evaluation is based on field studies,physicochemical measurements, hydrogeochemical analyses, and institutional data. Among the low- to mediumenthalpy geothermal fields, Bardakçılar, Karaılıca, and Çan-Merkez are utilized for thermal and health tourism,whereas Alibeyçiftliği lacks facilities, with the resource being used directly by local residents. The highest downholetemperatures were measured at Bardakçılar (750 m, 67 ºC) and Karaılıca (450 m, 61.9 ºC). Geothermometer calculations indicate that reservoir temperatures may exceed the measured downhole temperatures, pointing tothe possibility of cascade utilization. The metallic ore endowment of the region is represented by the Halilağa (CuAu) porphyry system; the Ağı Dağı (Au-Ag), Kocayayla (Pb-Zn ± Cu), and Kumarlar (Pb-Zn-Cu ± Au) epithermal systems; and the Yuvalar (Fe-Cu) skarn deposit, associated with ancient metallurgy. The polymetallic nature of these mineralization systems offers potential for the by-product recovery of elements such as Ge, Mo, and Sb, warranting further detailed investigation. The industrial raw material resources, in turn, comprise kaolin, silex, quartz, and feldspar reserves — the primary inputs of the ceramics industry — together with limestone used in the cement andconstruction sectors, and Çan stone, valued as a decorative material. The basin, which holds approximately 92.5million tons of lignite reserves, hosts two thermal power plants with a combined installed capacity of 650 MW. Themining sector, providing direct employment for approximately 7,000 people, constitutes one of the main components of the local economy; however, sectoral dependency and the low female employment rate pose a risk to socioeconomic sustainability. Acid rock/mine drainage poses environmental risks to the ecosystem. In this regard, theutilization of fly ash generated by thermal power plants in the neutralization of acidic drainage and in limiting theoxidation of waste rock is among the proposed circular economy measures. The solar power plant established on therehabilitated lignite site constitutes a concrete example of post-mining land use, and the wider adoption of similar applications is warranted. Expanding the range of geothermal energy use in the region through detailed geophysical surveys and deep drilling is of particular importance. The findings underscore the necessity of holistic measures that balance economic growth with social inclusivity and ecological conservation.

Abstract: A comprehensive surface survey was conducted in 2025 at the ancient city of Arneai, a site documented only to a limited extent in the scholarly literature. The investigations were carried out by an interdisciplinary team supported by modern technologies, focusing on the general geology of the city and its building stones. The ancientcity of Arneai is located within the Tauride tectonic belt, which includes the Taurus Mountains. The oldest geologicalunit in the study area is the Upper Cretaceous Beydağları Formation which is overlain by Paleocene, Eocene,and Miocene units. Carbonate units are prevalent in the region. These units, predominantly limestone, were used as building stones in antiquity. Building stones for the ancient city were extracted from local (in-situ) limestone bedrock. Scattered, generally fragmented terracotta materials found on the surface appear to have two distinct colors.The red soil material is estimated to have higher iron content than the yellowish material. The small amount ofslag material identified during the survey suggests the presence of small-scale smelting furnaces (possibly for lead production). These preliminary results provide a framework for future systematic archaeological excavations and detailed geological investigations.

Abstract: April 29, 2026, marked a day of profound and grievous loss for the geosciences community,and most notably for the Department of Geological Engineering at Ankara University.We mourn the passing of our highly esteemed professor, Dr. Korhan Esat, who dedicated hislife to comprehending Türkiye`s active tectonicsand seismicity, and who was widely renowned for the meticulousness of his research and his profound love for his profession. This unexpected farewell has brought immense grief to his family,the colleagues he worked alongside, and the generations of students he mentored. Dr. Esat completed his undergraduate education between 1995 and 2001 in the Department of Geological Engineering, Facultyof Engineering, Ankara University. Subsequently, he earned his master`s degree from the Graduate School of Natural and Applied Sciences at the same university in 2004 with his thesis titled"Stratigraphy and Tectonics of the area between Çankırı and Eldivan". In 2005, he embarked on his professional career as a Research Assistant in the same department.