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    Paramagnetic characterization of fossil mollusc shells at eastern part of the old Konya lake: its importance for EPR dating
    (Oxford Univ Press, 2023) Ekici, Gamze; Sayın, Ülkü; Işık, Mesut; Kapan, Sevinç; Demir, Ahmet; Aydın Karaaslan, Hülya; Delikan, Arif
    Fossil mollusc shells are used for dating geological materials because they are well preserved throughout geological time. In this study, the radicals in the structure of fossil mollusc shells (Dreissena iconica, Valvata piscinalis, Bithynia tentaculate, Unio pictorum) collected from the Eastern Part of Old Konya Lake in Turkiye were investigated by EPR technique. For all fossil shells, microwave and temperature dependence of the signals were examined, and the signals suitable for dating are discussed. Characteristic features of intrinsic and impurity-related radicals were identified and the importance of paleontological evaluation of molluscs to get a reliable equivalent dose in EPR dating studies was emphasised.
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    The Importance of Pre-Annealing Treatment for ESR Dating of Mollusc Shells: A Key Study for Ismil in Konya Closed Basin/Turkey
    (Amer Inst Physics, 2018) Ekici, Gamze; Sayin, Ulku; Aydin, Hulya; Isik, Mesut; Kapan, Sevinc; Demir, Ahmet; Engin, Birol
    In this study, Electron Spin Resonance (ESR) spectroscopy is used to determine the geological ages of fossil mollusc shells systematically collected from two different geological splitting at Ismil Location (37.72769 degrees N, 33.17781 degrees E) in eastern part of Konya. According to the assessment of obtained ESR ages, the importance of pre-annealing treatment emphasize in the case of g=2.0007 dating signal is overlapped with the other signals arisen from short lived radicals that cause the wrong age calculation. To overcome this problem, the samples are pre-annealed at 180 degrees C for 16 minutes and, in this case ESR ages are recalculated for g=1.9973 dating signal. Dose response curves are obtained using 1.9973 signals after pre-annealing treatments for each samples. ESR ages of samples are obtained in the range of 138 +/- 38 ka and 132 +/- 30 ka (Upper Pleistocene) according to the Early Uranium Uptake model and the results are in good agreement with the estimated ages from stratigraphic and paleontological correlation by geologists. Thus, it is suggested that especially in the case of g=2.0007 dating signal cannot been used due to superimposition case, the signal with 1.9973 g value can be used for dating after pre-annealing treatment. The results reports the first ESR ages on shells collected from Ismil Location and highlight the importance of pre-annealing treatment. This study is supported by TUBITAK 114Y237 research project.
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    The superiority of using the ESR dating method in mollusc shells compared to 14C and 230Th/234U: A case study at the eastern part of Konya closed basin, central Turkiye
    (Pergamon-Elsevier Science Ltd, 2025) Ekici, Gamze; Sayin, Ulku Akpinar; Delikan, Arif; Kapan, Sevinc; Biyik, Recep; Demir, Ahmet; Isik, Mesut
    The Konya Closed Basin in central Anatolia preserves Quaternary lacustrine sediments, providing critical evidence for regional paleoclimatic reconstructions. Accurate dating of these is essential for understanding Quaternary climate evolution in the area. In this study, fossil mollusc shells systematically collected from the eastern part of the basin were dated for the first time using ESR spectroscopy. Prior to dating analyses, comprehensive geological investigations and paleontological classifications were conducted. ESR spectra recorded at room temperature on both natural and gamma-irradiated samples revealed freely rotated CO2- radical signals at g = 2.0007. Kinetic studies confirmed the long-term stability of the CO2- radical, with high activation energies (similar to 1.3 eV) and thermal lifetimes exceeding similar to 10(6) years, reconfirming its reliability as a dating signal throughout the Quaternary period. Most ESR ages were derived from the 2.0007 signal, while the signal of the orthorhombic CO2- radical at g = 1.9973 was utilized for a few samples. Dose-response curves were best fitted to a single exponential saturation function and equivalent doses were calculated accordingly. ESR ages ranged from 138 to 6 ka, showing stratigraphic consistency with the sedimentary record. Comparative dating using C-14 AMS and Th-230/U-234 techniques demonstrated general agreement with ESR ages, although minor discrepancies were observed due to the open-system behavior of mollusc shells. Overall, the results support the chronological reconstruction of Holocene to Middle Pleistocene paleoenvironmental events in the Konya Closed Basin.