Testing TM-OSL on different quartz samples to illustrate the advantages of the technique

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Abstract
The importance of the fast decaying signal of quartz for dating sediments is confirmed by years of research. In OSL dating, the single-aliquot regenerative-dose (SAR) protocol is applied to estimate age. The OSL signal measured in this protocol consists of components with different properties, particularly with different susceptibility to bleaching in sunlight. It is known how complicated it is to extract the fast decaying signal from other overlapping signals when blue light is used for stimulation. Decomposing OSL curves into components is unsuitable for dating purposes due to the challenges involved in handling many OSL curves for age estimation and obtaining consistent results across these curves. An OSL measurement method based on optical stimulation while the sample is heated, so-called thermally modulated OSL (TM-OSL), was recently implemented in the SAR protocol. Instead of the blue light (470 nm) in SAR (hereinafter referred to as SAR BLSL), red light (620 nm) is used for optical stimulation. In the protocol with TM-OSL measurement, the fast component is isolated and used for the OSL age determination. The advantage of this approach for a set of samples selected from various depositional environments is presented. The equivalent dose for the same samples was also determined using the SAR protocol that involved red light stimulation (620 nm, SAR RLSL) at an elevated temperature (230°C). The obtained results by the protocols using red light (SAR TM-OSL and SAR RLSL) are compared with the ones determined using the SAR BLSL protocol. Using TM-OSL in the SAR protocol leads to more precise dating results. The shape of the TM-OSL curve for the fast OSL component in quartz allows to identify in the TM-OSL a contribution from a signal of another origin. It prevents age underestimation by excluding from calculations the share of OSL components, which can be less stable.

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