Türkiye Jeoloji Bülteni

Abstract: The Turkish geological community has experienced profound sorrow over the loss of one of its greatest values, our dear friend and teacher, Prof. Dr. Namık Aysal, a faculty member of the Department of Geological Engineering at Istanbul University-Cerrahpaşa, on October 6, 2025. Atonly 52 years of age, during the most productive years of his life, Prof. Dr. Aysal`s untimely passinghas left an irreplaceable void not only in the academic community but also among his student sand friends. Mr. Aysal dedicated his short life to science, his students, the Geochronology and Geochemistry Laboratory—which he establishedwith great effort alongside his colleagues and remains unique in our country—his colleagues through out Türkiye, and the mountains he loved so much. His multi-faceted personality, inexhaustible energy, and the "guiding driving force" heradiated to his surroundings are felt even more profoundly in his absence and are deeply missed.

Abstract: In this study, the Mollusca fauna (Gastropoda and Bivalvia) from two drilling cores, each 12 meters deepand obtained in Taşköprü village (located between Lake Akşehir and Lake Eber), was systematically examined for the first time, and the paleobiogeographic distribution of the fauna was documented. From the systematically collected samples obtained from the drilling cores, eight genera and eight species belonging to the class Gastropodaof the phylum Mollusca were identified, including Valvata piscinalis (O. F. Müller, 1774), Valvata sp., Bithyniapseudemmericia Schütt, 1964, Bithynia pseudemmericia operculum, Graecoanatolica lacustristurca Radoman, 1973,Laevicaspia caspia (Eichwald, 1838), Laevicaspia kolesnikoviana (Logvinenko & Starobogatov, 1966), Laevicaspia lincta (Milaschewitsch, 1908), Laevicaspia sp., Lymnaea sp., Stagnicola sp., Radix auricularia (Linnaeus, 1758),Radix sp., Gyraulus parvus (Say, 1817), and Gyraulus sp. Additionally, three genera and six species belongingto the class Bivalvia were identified, including Euglesa casertana (Poli, 1791), Euglesa personata (Malm, 1855),Pisidium amnicum (O. F. Müller, 1774), Pisidium jassiensis Cobălcescu, 1883, Pisidium sp., Dreissena iconicaSchütt, 1991, Dreissena polymorpha (Pallas, 1771), and Dreissena sp. Comparison with previous studies from theLakes Region shows that the occurrence of V. piscinalis, B. pseudemmericia, G. lacustristurca, R. auricularia, G.parvus, E. casertana, E. personata, P. amnicum, P. jassiensis, and D. iconica – species previously reported from sediments of the Konya Closed Basin and Lakes Eğirdir, Beyşehir, Burdur, and Suğla – suggests that during the LatePleistocene there may have been a physical connection among these basins, that these lakes developed under similar paleoenvironmental conditions.

Abstract: The Anatolian Diagonal is a prominent left-lateral shear zone that plays a key role in the neotectonic framework of Türkiye, spanning 170 km between the Central Anatolian and East Anatolian fault zones and extending approximately 850 km from Erzincan to the Cyprus Arc. Its southwestern onshore termination is represented by theEcemiş-Deliler Fault, while its offshore continuation, the Biruni Fault, trends toward the Cyprus Arc. This studyaims to characterise the southwestern end of the Ecemiş-Deliler Fault through geomorphic markers, and to identifythe Biruni Fault using key offshore seismic reflection profiles and geological cross-sections provided by Turkish Petroleum. Focal mechanism solutions for offshore seismic events are also examined to assess fault kinematics.Based on onshore observations, a left-lateral offset of 18 km along the Göksu River indicates a long-term slip rate ofapproximately 2.25 mm/year at the southwestern end of the Ecemiş-Deliler Fault. Offshore, detailed definition andmapping of the Biruni Fault revealed that it comprises a zone of closely spaced, parallel strike-slip segments in itsnortheastern sector, transitioning in a single linear fault trace that extends south westward toward the Aegean Arc. Despite its clear morphological expression, the southwest end of Ecemiş-Deliler fault and the Biruni Fault of theAnatolian Diagonal have low seismic activity, likely because most regional deformation is accommodated furtherwest along the Antalya-Kekova Fault Zone and the Ptolemy–Pliny–Strabo Fault Zone. The restraining stepovers ofthe Antalya Thrust and Fethiye Thrust between these structures provide new insight in a slip partitioning in  the eastern Mediterranean. 

Abstract: Degradational changes caused by rapidly increasing anthropogenic activities in recent years inlake ecosystems, which are crucial for biodiversity, have attracted attention. Potentially toxic element (PTE)contamination plays a significant role in environmental degradation in lake ecosystems. This study focused on the ecological risk along the tombolo shores of Lake Uluabat (Apolyont), one of Turkey`s important wetlands, where  Gölyazı settlement is located. Sediment samples taken from the lake bottom along the tombolo shore were analysedfor organic carbon and chlorophyll degradation products. Furthermore, the enrichment factor (EF), contaminationfactor (CF), modified contamination factor (mCD), toxic risk index (TRI), pollution load index (PLI), ecological risk index (mER), and potential ecological risk index (PER) were calculated using PTE values determined by ICPMS. Based on the obtained data, the PTE concentration in lake sediments is in the following order: Fe (29200) >Al (21500) > Mn (962) > Ni (256) > Cr (101) > Zn (90)> As (39) > Pb (37) > Cu (31) > Co (20). According to EFdata, the enrichment level of PTEs is Ni (10.31) > As (8.24) > Pb (5.05) > Mn (3.12) > Cr (3.08) > Co (2.81) > Zn(2.58) > Fe (2.30) > Cu (1.88). The ecological risk level from PTEs is Ni (51), Co (41), Pb (25), As (24), Cu (10) and the average potential ecological risk level is 161. In the littoral zone around Gölyazı settlement, all PTEs except Cuare enriched to a certain extent. Ni was identified as the ecological risk source with highest risk in the lake. The mainanthropogenic risk sources in the lake, where a moderate ecological risk was identified, are agricultural, industrial,and settlement wastes. 

Abstract: Microplastics have increasingly been recognized as a global pollutant due to their pervasive distribution and potential adverse impacts on marine ecosystems. Microplastics (MPs) were collected from surface sediments at five sites in the Gulf of Gemlik using density separation. The isolated MPs were subsequently identified and characterized with a stereomicroscope and fluore scence microscope. This study provides the first comprehensiveassessment of microplastic pollution in the sediments of the Gulf of Gemlik, focusing on their abundance, spatial distribution, and potential ecological risks. The concentration of the MPs ranged from 2,200 to 6,400 items per kilogram of dry weight across the study sites. Fibers were the dominant shape type (58.4%), while black was the mostprevalent color (26%). According to the ecological risk assessment, the sediments were classified as moderately to considerably contaminated with MPs. These findings contribute new insights in the occurrence and characteristics of microplastics in the surface sediments of the Gulf of Gemlik and establish a foundation for future research and management strategies aimed at mitigating microplastic pollution.

Abstract: The Isparta Basin is a tectonically complex depression situated at the junction between the WesternAnatolian extensional province and the Tauride orogenic belt. It lies near the intersection of the Hellenic and Cyprusarcs, forming the Isparta Angle. This transitional zone is characterised by intense crustal deformation, complex fault systems, and active seismicity, making it a key area for geophysical investigation. Microgravity anomalies were analysed to assess the thickness of the basin`s sedimentary deposits. A 2-D Fourier transformation-based procedure was used to decompose the gravity data in regional and residual components. This spectral filtering step isolated shallow subsurface signals from broader tectonic influences, thereby providing a robust foundation for depth modelling by enhancing the resolution of near-surface features that are often masked by deeper structuraltrends. Residual gravity anomalies were further examined using both 2-D and 3-D local optimisation-based inversion techniques. These complementary methods allowed for cross-validation of results mathematically and improved confidence in the derived structural interpretations. The resulting basement depth estimates demonstrate consistencyand align well with the established geological framework of the Isparta Basin, including known fault geometries and stratigraphic boundaries, with the inversion results indicating maximum sedimentary fill thickness of approximately0.53 km. This result has practical implications for disaster management, particularly in assessing the potential forseismic amplification. Thick sedimentary sequences can substantially affect ground-motion characteristics during earthquakes, especially within basin environments. Therefore, mapping the spatial distribution of sedimentary accumulation contributes to more informed regional risk assessments and supports the development of target edmitigation strategies. These findings are expected to provide valuable input for land-use planning and infrastructureresilience in the Isparta Basin, offering essential baseline information for authorities and engineers involved inseismic hazard mitigation.

Abstract: The Çakrazboz Formation, located in the Amasra–Kastamonu region of the Western Pontides (NWTürkiye), represents the only known Triassic continental sedimentary succession in Türkiye. This study integrates sedimentological, petrographic, and stratigraphic data from six measured sections to reconstruct depositional environments and evaluate paleoclimatic controls. Field and thin-section analyses reveal a complex facies mosaiccomprising three major lithofacies groups: lacustrine, palustrine, and fluvial. Lacustrine facies are represented by carbonate-rich successions, including micrite, wackestone, and packstone, indicating low-energy profundal tosublittoral settings. Palustrine facies, occurring predominantly in marginal lake environments, are characterized by pedogenic overprinting, fenestral fabrics, root traces, and desiccation features, with the Bozköy and Başköy-1sections showing more pronounced development of these features. Başköy-2 and Başköy-3 exhibit fluvial pointbar deposits with upward-fining successions and pedogenically modified mudstones, representing meanderingriver systems deposited during overfilled lake stages. Stratigraphic and sedimentological evidence indicates that the basin experienced repeated shifts between underfilled, balanced-fill, and overfilled lake stages. Carbonate-richsuccessions in the Çakrazboz and lower İncigez sections represent low-energy profundal lacustrine conditionstypical of underfilled stages. The upper İncigez and Başköy-1 sections preserve features of balanced-fill conditions,with fining-upward transgressive intervals overlain by progradational littoral facies. Overfilled conditions are locallyrecorded in Bozköy and in the upper parts of Başköy-1, as evidenced by laterally extensive successions that thicken and coarsen upward, reflecting sustained freshwater inflow. These vertical facies transitions, stacking patterns, anddiagenetic overprints are indicative of orbitally forced lake-level fluctuations under subhumid to semi-arid climateregimes, contributing to a broader understanding of Late Triassic continental basin evolution, facies architecture, and climate-controlled sedimentation.