title: Dose estimation, kinetics and dating of fossil marine mollusc shells from northwestern part of Turkey.
abstract: Electron spin resonance (ESR) spectroscopy was used to determine the geological formation age of fossil mollusc shells taken from marine terrace deposits (İkizlerçeşme-Çanakkale) in northwestern part of Turkey. This work reports the first results obtained by the ESR technique on shells collected from this region. In the ESR spectra of the natural and γ-irradiated shell samples, two different signals attributed to orthorombic (gxx=2.0030, gzz=2.0015, gyy=1.9980) and isotropic (g=2.0006) CO2(-) ion radicals were overlaped (Signal C). Annealing and kinetic experiments suggest the possibility of using the ESR signal at g=2.0015 (C signal) for the estimation of accumulated geological doses. The ESR signal growth curve on additional gamma irradiation has been best fitted by a combination of two single exponential saturation functions. This may support the existence of at least two components of the g=2.0015 ESR dating signal. Based on this model, the accumulated dose of the samples was determined as 110±11Gy. Also the isothermal decay curves of the ESR dating signal could be best described by the combination of two first order decay functions. Activation energy and meanlifetime values at 15°C of the two components were calculated as E1=1.4±0.1eV, E2=1.1±0.1eV, τ1=7.2×10(6) years and τ2=3.3×10(3) years, respectively. Uranium content of the studied shells was found to be high according to their chemical analysis. This may point out that the marine shell has received uranium from outside particularly in carbonate sediment. Therefore, the ESR age of the samples was also calculated using Early Uptake (EU), Linear Uptake (LU) and Combined Uptake (CU) models and results were discussed.
authors.affiliation: Turkish Atomic Energy Authority, Sarayköy Nuclear Research and Training Center, 06983 Saray, Ankara, Turkey.
authors.forename: Canan
authors.initials: C
authors.lastname: Aydaş
authors.affiliation: Dokuz Eylül University, Faculty of Science, Department of Physics, 35370 Buca, İzmir, Turkey. Electronic address: birol_engin65@yahoo.com.
authors.forename: Birol
authors.initials: B
authors.lastname: Engin
authors.affiliation: Çanakkale Onsekiz Mart University, Department of Geological Engineering, 17020 Çanakkale, Turkey.
authors.forename: Sevinç
authors.initials: S
authors.lastname: Kapan
authors.affiliation: Çanakkale Onsekiz Mart University, Department of Geophysical Engineering, 17020 Çanakkale, Turkey.
authors.forename: Tolga
authors.initials: T
authors.lastname: Komut
authors.affiliation: Turkish Atomic Energy Authority, Sarayköy Nuclear Research and Training Center, 06983 Saray, Ankara, Turkey.
authors.forename: Talat
authors.initials: T
authors.lastname: Aydın
authors.affiliation: Dokuz Eylül University, Faculty of Science, Department of Physics, 35370 Buca, İzmir, Turkey.
authors.forename: Ufuk
authors.initials: U
authors.lastname: Paksu
mesh_terms: D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D005580:Fossils; D005720:Gamma Rays; D055593:Geological Phenomena; D007700:Kinetics; D008954:Models, Biological; D008974:Mollusca / Q000737:chemistry / Q000528:radiation effects; D011874:Radiometry; D013997:Time Factors; D014421:Turkey; D014501:Uranium / Q000032:analysis
chemical_list: D014501:Uranium
keywords: Aragonite fossil shells; ESR dating; Electron Spin Resonance (ESR); Mollusc shell; Turkey; Çanakkale