Methodological studies on integration time interval's selection for the luminescence ages using quartz and feldspar minerals; sediments collected from Sakarya, Turkey

摘要

In this study, two different equivalent dose protocols using Infrared stimulated luminescence (IRSL), namely post IR (pIRIR) and Multi-Elevated temperature post IRSL (MET-pIRIR) were applied to geological samples collected from terrace staircases formed along the Sakarya River, western Anatolia, Eastern Marmara Region, Turkey. Methodological aspects were studied, as the IRSL signal, which is measured at elevated temperatures, yields unusual shape, consisting of an initial increasing part which is followed by the well-known decaying shape. Therefore, according to signal shape, instead of de-convolving the IRSL signals, equivalent dose estimations were performed using different time integration intervals of the emission. The results constitute of two groups, yielding equivalent dose values, in the range between 55 and 110 Gy for selected samples. Since de-convolution of the IRSL signals is both time consuming as well as difficult, mostly due to the presence of tunneling localized transitions, the selection of the appropriate/optimum time integration interval was discussed. The outcomes of this study indicate that IR stimulations at higher temperatures ranging from 200 to 250 degrees C are useful for feldspar dating, providing that initial increasing part will be eliminated. The thermal activation energy of that unusual part of the signal was calculated around 0.035 +/- 0.005 eV using Arrhenius plot, indicating that it may arise from phonon lattice interactions.