A progressively elevated temperature (PET) IRSL SAR procedure &ndash; first experiments and results

Kadereit, Annette; Sontag-González, Mariana; Kreutzer, Sebastian; Colombo, Marco; Schmidt, Christoph; Hanson, Paul R.

doi:10.5194/egusphere-2025-5978

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https://doi.org/10.5194/egusphere-2025-5978

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16 Dec 2025

| 16 Dec 2025

Status: this preprint is open for discussion and under review for Geochronology (GChron).

A progressively elevated temperature (PET) IRSL SAR procedure – first experiments and results

Annette Kadereit, Mariana Sontag-González, Sebastian Kreutzer, Marco Colombo, Christoph Schmidt, and Paul R. Hanson

Abstract. Infrared stimulated luminescence (IRSL) dating is a common technique for dating feldspar-bearing sediment deposits. The technique is preferentially applied as a single aliquot regenerative (SAR) protocol derivative: Post-infrared infrared (pIR_1stIR_2nd) and multiple elevated temperature (MET) SAR protocols. Both of these techniques aim to reduce problems with unstable luminescence traps common to feldspars, known as anomalous fading. Elimination of the unstable IRSL signal component, which may lead to age underestimation, is achieved by sequential sampling of the IRSL signal at either two (pIR_1stIR_2nd) or a few (MET) discrete temperatures, usually in the range 50 °C to 290 °C. We propose a modified approach, the progressively elevated temperature (PET) IRSL SAR, which continuously records the luminescence signal while progressively elevating the sample temperature. The benefits of this approach include the generation of quasi-continuous data chains, beginning with the recorded PET-IRSL signal curves, over De-value curves relevant for palaeodose assessment, a-value curves used for dose-rate refinement, and g-value curves serving to assess the signal loss resulting from fading. In addition to anomalous fading problems, feldspars do not bleach as quickly and thoroughly as quartz, potentially resulting in age overestimation. The illustrative PET data curves may be useful in illustrating a sample´s bleaching and fading history. Thus, they may allow users to both reduce problems with anomalous fading and identify aliquots that are least impacted by incomplete bleaching.

Received: 01 Dec 2025 – Discussion started: 16 Dec 2025

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Annette Kadereit, Mariana Sontag-González, Sebastian Kreutzer, Marco Colombo, Christoph Schmidt, and Paul R. Hanson

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RC1:
'Comment on egusphere-2025-5978', Jakob Wallinga, 26 Jan 2026 reply
Review of the manuscript ‘A progressively elevated temperature (PET) IRSL SAR procedure – first experiments and results’ by Kadereit et al.
Submitted to GChron, reviewed by Jakob Wallinga.

I would like to compliment the authors with their original, complete and well documented manuscript, which details the development and a number of tests of a new approach to obtain equivalent doses on single aliquots of feldspar. Their progressively elevated temperature (PET) approach builds on the established single-aliquot regenerative dose (SAR) method using the post-IR IRSL signal. However it deviates in that IR and post-IR signals are obtained during a combined Continuous Wave stimulation while the sample temperature is raised. The approach has not been attempted for feldspar before, and has several potential advantages over widely used two-step (IR-pIRIR) and multiple step (MET) approaches for identifying anomalous fading and bleaching trends as a function of measurement temperature. Thereby the PET approach has the potential to develop into the method of choice for feldspar IR/pIRIR measurements. I warmly recommend publishing of this highly interesting manuscript, which I expect to become widely used and cited by the luminescence community.

In my mind the manuscript could be further improved by considering a few issues in more detail:
The clarity of the introduction may be improved by adding a clear aim and research questions in the final paragraph. The authors do much more than ‘introduce a ……procedure’.

For developing and testing a new approach, it is always helpful to work on a set of very well-defined samples with high-quality independent age control. Unfortunately, the samples used lack such age control. Why did the authors perform the research with these samples?

For background subtraction, the authors propose to use the dark counts measured at 60oC after the PET stimulation. They show that the instrument background is identical with and without IR stimulation for an empty aliquot and independent of temperature (Fig. S6.5). However, this approach for background calculation is very different from the widely-used late background subtraction. Moreover, the signal obtained during the recuperation measurement seems to be much higher than this background, especially for the higher temperatures (e.g. Fig. 3). Could the background-subtraction approach be the reason for elevated De estimates in the higher temperature range as observed in Fig. 7 (and discussed elsewhere)? I would like to encourage the authors to consider and discuss the validity of the background subtraction in more detail.

For some samples, dose-recovery tests yielded doses well below the expected dose for low-temperature IR in combination with a high preheat (e.g. Fig. 6ab, supplement 6). Similar behaviour has previously been reported by Kars et al. (2014 - https://doi.org/10.1016/j.quageo.2014.04.001) who attributed this to trapping sensitivity change. I encourage the authors to discuss their findings (also for De estimation and possibly bleaching experiments) in this perspective.

Minor (technical) suggestions:
Fig. 2: The step ‘give regenerative dose’ is shown at the end of each cycle (step 8). I suggest the dose (either natural or regenerative) should appear at the top of the cycle rather than at the end of the previous cycle.

Fig. 3: The shape of the recycling PET-IRSL curve (R6) is different from the first measurement (R3). Is this typical? Could you discuss the reasons and implications?

I would suggest to remove all doses in seconds from the text and figures (or at least put dose in Gy on the main (left-hand) y-axis). The unit of dose is Gy, and the conversion to irradiation time can be made using the source calibration values provided in the manuscript.

For the dose recovery tests, doses remaining after bleaching (remnant dose) seem not to be subtracted. Why not? Similar for a-value determination; this is mentioned in line 755 but not put into practice.

When discussing the shape of the curve (section 7.1.1) in relation to differences in dose for different sections (e.g. due to bleaching or fading), I would suggest referring to the section where De is discussed.

Section 7.1.3: ‘upward trending g-values’ – reading from left to right this would be ‘downward trending’.

Section 7.1.4: Identifying seven different curve shapes (1, 2a-f) based on the available data seems a bit much, and thereby speculative. With regard to 2b - the ‘initial downward bent’ – I would suggest calling it ‘upward’ (reading from left to right, similar to g-value). Moreover, how do you distinguish this ‘hook’ from the unstable component discussed in the fading section?

Writing and presentation:
The manuscript is very complete, which is a good thing. However it could be more concise in places, e.g. by reducing overlap between main text and figure captions.

Some parts of the manuscript could also be moved to the supplement (e.g. when discussing the individual samples, and the separate aliquots shown in fig. 17bc; 18bc)

Some very long sentences make reading a bit of a struggle in places. Please shorten and/or split these.

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Citation: https://doi.org/10.5194/egusphere-2025-5978-RC1

Annette Kadereit, Mariana Sontag-González, Sebastian Kreutzer, Marco Colombo, Christoph Schmidt, and Paul R. Hanson

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https://doi.org/10.5194/egusphere-2025-5978-supplement

Annette Kadereit, Mariana Sontag-González, Sebastian Kreutzer, Marco Colombo, Christoph Schmidt, and Paul R. Hanson

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Short summary

Infrared-stimulated luminescence (IRSL) dating of feldspar is an essential tool for dating sediments. Two major challenges of the IRSL signal are its “anomalous” instability potentially leading to age underestimation and its slow bleaching by sunlight which may cause age overestimation. Here we propose a progressively elevated temperature (PET) IRSL single aliquot regenerative (SAR) procedure to isolate a potentially stable IRSL signal from a set of best bleached subsamples.


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