Last Glacial loess in Europe: luminescence database and chronology of deposition

Bosq, Mathieu; Kreutzer, Sebastian; Bertran, Pascal; Lanos, Philippe; Dufresne, Philippe; Schmidt, Christoph

doi:https://doi.org/10.5194/essd-2023-105

Preprints

https://doi.org/10.5194/essd-2023-105

Preprints

31 May 2023

| 31 May 2023

Status: a revised version of this preprint was accepted for the journal ESSD and is expected to appear here in due course.

Last Glacial loess in Europe: luminescence database and chronology of deposition

Mathieu Bosq, Sebastian Kreutzer, Pascal Bertran, Philippe Lanos, Philippe Dufresne, and Christoph Schmidt

Abstract. During the last glacial period, the climate shift to cold conditions associated with changes in atmospheric circulation and vegetation cover resulted in the development of large aeolian systems in Europe. On a regional scale, many factors may have influenced dust dynamics, such as the latitudinal difference between the various aeolian systems and the variability of the sources of wind-transported particles. Therefore, the assumption that the timing of aeolian deposition is strictly synchronous in Europe does not seem to be the most plausible hypothesis and needs to be evaluated. To test this assumption, the chronology of loess deposition in different European regions was investigated by studying 93 luminescence-dated loess-palaeosol sequences with their data recalculated and compiled in a single CSV file: the ChronoLoess database. Our study shows that the two major aeolian systems, the Northern European Loess Belt (NELB) on the one hand and the systems associated with the rivers draining the Alpine Ice Sheet on the other hand, developed asynchronously. The significant deposition started at about 32 ka for the NELB vs 40 ka for the perialpine loess and peaked about two millennia later for the former (21.8 ka vs 23.9 ka, respectively). This shift resulted mainly from the time lag between the maxima of the Alpine and Fennoscandian ice sheets, which acted as the primary sources of fine-grained particles through glacial abrasion. The major geomorphic changes that resulted from the development and decay of the Fennoscandian and British-Irish ice sheets also played an important role. Particularly, ice sheet coalescence during the LGM diverted meltwater fluxes through the Manche River and provided vast amounts of glacial particles available for deflation in the western NELB. The period during which the maximum Mass Accumulation Rate was reached for each loess-palaeosol sequence is relatively homogeneous in the NELB and ranges from 30 ka to 19 ka, whereas it is more scattered in the perialpine systems (>60 ka to 14 ka). This probably resulted from a combination of factors, including the asynchrony of maximum valley glacier advances and local geomorphic factors.

Received: 22 Mar 2023 – Discussion started: 31 May 2023

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Mathieu Bosq et al.

Status: closed

RC1:
'Comment on essd-2023-105', Anonymous Referee #1, 09 Jun 2023

Review of „Last Glacial loess in Europe: luminescence database and chronology of deposition” by Bosq et al.
In the last decade or two, a large amount of new absolute chronological data from European loess sediments has been published, mainly for the last glacial. Most of these are luminescence ages, a smaller part radiocarbon dates. Although some reviews of mass accumulation rates calculated from previously published age data have been published in recent years, the authors have recognised the need to create a single database, which can further be developed in a uniform way. ChronoLoess is a great initiative and the authors have obviously invested a lot of time and effort in the creation of this database of over 1400 entries. They have also partially revamped the previously accepted methodology of extracting useful information from the published absolute ages and in this very exciting manuscript they also present and discuss the spatial and temporal variations of loess accumulation focussing on the North European Loess Belt (NELB) and the Perialpine Loess (PL).
The language of the manuscript is excellent, the structure is logical and the arguments are easy to follow. The methodology is well summarized and seems scientifically correct, with only two comments from my side concerning the 1) calculation of Rb concentrations from the K contents and the 2) treatment of obvious age inversions in chronologies of some of the sites (e.g. Bialy Kosciol). Regarding the first issue: the major problem here is that the equation published by Mejdahl (1987) systemtically overestimates Rb from K and the correlation between these two elements are rather weak in reality (see Fig 3 and discussion in Buylaert et al., 2018, Radiation Measurements 120, 181-187). Please comment on this and the second question on age inversion.
The main conclusions of the authors are correct and I can agree with most of them, although there are some comments that I would suggest for reflection or improvement. One critical issue is how to determine in a statistically exact way when the time-activity curve crosses the uniform random distribution (URD), as the authors have used this as a basis for inferring the initiation of significant dust accumulation and have correlated this with certain Heinrich events (HE). In my opinion, this has considerable uncertainties on the order of 1000-3000 years that need to be taken into account, however, I believe that the dust accumulation peaks are well defined (NELB: 21.8 ka, PL: 23.9 ka) and may indeed be causally related to HE2.
I have further suggestions, especially for certain interpretations, such as the potential causes of the time lag in the aforementioned peak accumulation (NELB vs. PL). This may indeed depend on several factors, as the authors rightly state, but these factors need to be reconsidered/refined. However, these are rather pedantic points and do not affect the main conclusions. I believe that if the authors improve these points in a small revision and the other peer reviews end up favourably, this paper can be published in ESSD.

Citation: https://doi.org/10.5194/essd-2023-105-RC1
- CC1: 'Reply on some questions raised by RC1', Sebastian Kreutzer, 09 Jun 2023
  
  Thank you for the very positive and encouraging comments.
  I may step in and reply to the two comments that concern the age inversion and the Rb concentration calculated from the K concentration after (Mejdahl, 1987).
  I will start with the dose rate question: We had pragmatically selected the Mejdahl (1987) calculation of the Rb concentration (if not determined by the study authors in the first place), because this was the option available in DRAC (Durcan et al., 2015) and it appeared more meaningful to include Rb than leaving it out. This follows Mejdahl (1987), who concluded that in case of an absent of a measured Rb concentration, the dose rate is larger if Rb is omitted compared to situations where only a rough estimate is used.
  Buylaert et al. (2018), who investigated the dependency of the equivalent dose on the potassium concentration on single grains, showed, as Huntley and Hancock (2001) and Mejdahl (1987), that the true Rb concentration is likely to vary tremendously between samples when measured. Undeniable, the data in Buylaert et al. (2018)provides evidence for their samples that the method by Mejdahl (1987) would systematically overestimate the true Rb concentration compared to their measurement of single grains. This might be true for some multi-grain values in the Chronoloess database, while it might not match other situations.
  Therefore we suggest adding a few lines to the revised paper to address the concerns but stick to the Mejdahl (1987) approach. Suppose better data (e.g., a combination of Mejdahl (1987), Huntley and Hancock (2001)and Buylaert et al. (2018)) becomes available. In that case, this can be implemented in an updated version of DRAC and hence used in the Chronoloess database (Durcan et al., 2015).
  To address the equally justified concerns of age inversion, we believe this should not generally matter for our analysis but reflects results typical for loess dating studies. The age inversion might be true or just an extreme value. Regardless, the weight for the overall interpretation of the European loess deposit is negligible.
  I hope this makes the response makes somewhat sense and elaborates our decisions.
  Kind regards,
  Sebastian Kreutzer
  
  Citation: https://doi.org/10.5194/essd-2023-105-CC1
- CC2: 'Reply on RC1', Pascal Bertran, 12 Jun 2023
  
  Thank you for the interesting and supportive comments. Below we list our responses along with changes we propose to make in our manuscript and upload this new version after the closure of the open discussion (Copernicus does not support uploading new manuscript version during the discussion process).
  Line 141: ‘the number of events…’: We suggest modifying to ‘the number of events (here, the number of dated dust accumulation events) that have occurred per unit of time.’
  Line 219: We changed by ‘a reliable picture of past dust deposition’
  Line 249: We changed by ‘Southern England’, ‘Southern Poland’ to be consistent with the other regions…
  Line 274: OK. We added the reference Ujvari et al. (2008).
  Line 290 and following: Thank you for this comment. We suggest the following rephrasing: 'In the former area, dust accumulation increased from about 32 ka, i.e. during GS-5.2 (Rasmussen et al., 2014) and rose steeply after 30 ka, i.e. during GS-5.1 (Fig. 3B). In contrast, deposition in the perialpine area started earlier and increased as early as 42 ka (GS-11), with a further rise after 40 ka (GS-9) (Fig. 3C). Although the chronological limits of Heinrich Events (HEs) remain relatively imprecise, GS-5.1 and GS-9 correlate with HE-3 and HE-4 respectively in marine records (Sanchez Goñi and Harrison, 2010).'
  Line 326 and following: The factors listed according to Kocurek and Lancaster (1999) are those conventionally evoked when working on aeolian deposits in the geological record, although not all of them are necessarily relevant here. We suggest a minor modification of the phrase: “In agreement with Kocurek and Lancaster (1999), several factors may have influenced this time lag, such as (i) the amount of fine particles released by their respective sedimentary sources; (ii) the wind transport capacity; (iii) the local availability of sediments (role of vegetation and soil moisture). Among the various potential factors, fluctuations in the number of particles available for deflation due to changes in ice sheet pattern appear to be a pivotal point that explains the chronological disparities between aeolian systems.”
  Line 330. OK. We will change to ‘During late MIS 3’.
  
  Citation: https://doi.org/10.5194/essd-2023-105-CC2
RC2:
'Comment on essd-2023-105', Anonymous Referee #2, 05 Aug 2023
The study “Last Glacial loess in Europe: luminescence database and chronology of deposition” by Bosq et al., aims to create a unique database of European loess osl dated chronologies and accumulation rates during MIS 1-MIS 3 period. The data appears robust, and the methods used are sound and appropriately applied.
In my opinion this is a comprehensive study which will be a significant contribution to the loess, geochronological and palaeoclimatological community. The manuscript itself is well-structured, language is appropriate, the methods ant data are well presented and the conclusions are sound. The figures are also well designed and complement the data accurately. I would like to highlight that the authors did an excellent job with the manuscript and I very much enjoyed reading it.
I recommend publication, however, I would only like for the authors to take into account a few of my questions.

Have you considered the dating resolution as a parameter when calculating MARs? In my experience, dating resolution can have a significant impact on the accurate calculation of MAR distribution over the investigated time period. Maybe you should mention that.

Have you thought on maybe applying an additional age-depth modelling method and compare the results? I acknowledge that this would be a large amount of additional work, but often different modelling software produces different results. It would be interesting to see the discrepancies. This is just a thought, not a critique point.

Have you thought of expanding the investigation beyond MIS 3? I do know that these chronologies are very scares, but there are some studies from the Carpathian Basin where LPS were dated beyond MIS 5.

I think it would have been interesting to compare these results with MARs from LPS outside of Europe (e.g. Chinese Loess Plateau). We might get a better insight into the atmospheric dust activity on an intercontinental scale. However, I do recognize that this might be beyond the scope of this paper. Please take this just as an idea and/or a suggestion.
Citation: https://doi.org/10.5194/essd-2023-105-RC2
- AC1:
  'Reply on RC2', Mathieu Bosq, 09 Aug 2023
  
  Please find our responses (in blue) in the attached document
  
  Citation: https://doi.org/10.5194/essd-2023-105-AC1
  - RC3: 'Reply on AC1', Zoran Peric, 09 Aug 2023
    
    I thank the authors for their responces.
    All my questions have been appropriately and satisfactory answered which is why I recommend publication with no further changes.
    
    Citation: https://doi.org/10.5194/essd-2023-105-RC3

Status: closed

RC1:
'Comment on essd-2023-105', Anonymous Referee #1, 09 Jun 2023

Review of „Last Glacial loess in Europe: luminescence database and chronology of deposition” by Bosq et al.
In the last decade or two, a large amount of new absolute chronological data from European loess sediments has been published, mainly for the last glacial. Most of these are luminescence ages, a smaller part radiocarbon dates. Although some reviews of mass accumulation rates calculated from previously published age data have been published in recent years, the authors have recognised the need to create a single database, which can further be developed in a uniform way. ChronoLoess is a great initiative and the authors have obviously invested a lot of time and effort in the creation of this database of over 1400 entries. They have also partially revamped the previously accepted methodology of extracting useful information from the published absolute ages and in this very exciting manuscript they also present and discuss the spatial and temporal variations of loess accumulation focussing on the North European Loess Belt (NELB) and the Perialpine Loess (PL).
The language of the manuscript is excellent, the structure is logical and the arguments are easy to follow. The methodology is well summarized and seems scientifically correct, with only two comments from my side concerning the 1) calculation of Rb concentrations from the K contents and the 2) treatment of obvious age inversions in chronologies of some of the sites (e.g. Bialy Kosciol). Regarding the first issue: the major problem here is that the equation published by Mejdahl (1987) systemtically overestimates Rb from K and the correlation between these two elements are rather weak in reality (see Fig 3 and discussion in Buylaert et al., 2018, Radiation Measurements 120, 181-187). Please comment on this and the second question on age inversion.
The main conclusions of the authors are correct and I can agree with most of them, although there are some comments that I would suggest for reflection or improvement. One critical issue is how to determine in a statistically exact way when the time-activity curve crosses the uniform random distribution (URD), as the authors have used this as a basis for inferring the initiation of significant dust accumulation and have correlated this with certain Heinrich events (HE). In my opinion, this has considerable uncertainties on the order of 1000-3000 years that need to be taken into account, however, I believe that the dust accumulation peaks are well defined (NELB: 21.8 ka, PL: 23.9 ka) and may indeed be causally related to HE2.
I have further suggestions, especially for certain interpretations, such as the potential causes of the time lag in the aforementioned peak accumulation (NELB vs. PL). This may indeed depend on several factors, as the authors rightly state, but these factors need to be reconsidered/refined. However, these are rather pedantic points and do not affect the main conclusions. I believe that if the authors improve these points in a small revision and the other peer reviews end up favourably, this paper can be published in ESSD.

Citation: https://doi.org/10.5194/essd-2023-105-RC1
- CC1: 'Reply on some questions raised by RC1', Sebastian Kreutzer, 09 Jun 2023
  
  Thank you for the very positive and encouraging comments.
  I may step in and reply to the two comments that concern the age inversion and the Rb concentration calculated from the K concentration after (Mejdahl, 1987).
  I will start with the dose rate question: We had pragmatically selected the Mejdahl (1987) calculation of the Rb concentration (if not determined by the study authors in the first place), because this was the option available in DRAC (Durcan et al., 2015) and it appeared more meaningful to include Rb than leaving it out. This follows Mejdahl (1987), who concluded that in case of an absent of a measured Rb concentration, the dose rate is larger if Rb is omitted compared to situations where only a rough estimate is used.
  Buylaert et al. (2018), who investigated the dependency of the equivalent dose on the potassium concentration on single grains, showed, as Huntley and Hancock (2001) and Mejdahl (1987), that the true Rb concentration is likely to vary tremendously between samples when measured. Undeniable, the data in Buylaert et al. (2018)provides evidence for their samples that the method by Mejdahl (1987) would systematically overestimate the true Rb concentration compared to their measurement of single grains. This might be true for some multi-grain values in the Chronoloess database, while it might not match other situations.
  Therefore we suggest adding a few lines to the revised paper to address the concerns but stick to the Mejdahl (1987) approach. Suppose better data (e.g., a combination of Mejdahl (1987), Huntley and Hancock (2001)and Buylaert et al. (2018)) becomes available. In that case, this can be implemented in an updated version of DRAC and hence used in the Chronoloess database (Durcan et al., 2015).
  To address the equally justified concerns of age inversion, we believe this should not generally matter for our analysis but reflects results typical for loess dating studies. The age inversion might be true or just an extreme value. Regardless, the weight for the overall interpretation of the European loess deposit is negligible.
  I hope this makes the response makes somewhat sense and elaborates our decisions.
  Kind regards,
  Sebastian Kreutzer
  
  Citation: https://doi.org/10.5194/essd-2023-105-CC1
- CC2: 'Reply on RC1', Pascal Bertran, 12 Jun 2023
  
  Thank you for the interesting and supportive comments. Below we list our responses along with changes we propose to make in our manuscript and upload this new version after the closure of the open discussion (Copernicus does not support uploading new manuscript version during the discussion process).
  Line 141: ‘the number of events…’: We suggest modifying to ‘the number of events (here, the number of dated dust accumulation events) that have occurred per unit of time.’
  Line 219: We changed by ‘a reliable picture of past dust deposition’
  Line 249: We changed by ‘Southern England’, ‘Southern Poland’ to be consistent with the other regions…
  Line 274: OK. We added the reference Ujvari et al. (2008).
  Line 290 and following: Thank you for this comment. We suggest the following rephrasing: 'In the former area, dust accumulation increased from about 32 ka, i.e. during GS-5.2 (Rasmussen et al., 2014) and rose steeply after 30 ka, i.e. during GS-5.1 (Fig. 3B). In contrast, deposition in the perialpine area started earlier and increased as early as 42 ka (GS-11), with a further rise after 40 ka (GS-9) (Fig. 3C). Although the chronological limits of Heinrich Events (HEs) remain relatively imprecise, GS-5.1 and GS-9 correlate with HE-3 and HE-4 respectively in marine records (Sanchez Goñi and Harrison, 2010).'
  Line 326 and following: The factors listed according to Kocurek and Lancaster (1999) are those conventionally evoked when working on aeolian deposits in the geological record, although not all of them are necessarily relevant here. We suggest a minor modification of the phrase: “In agreement with Kocurek and Lancaster (1999), several factors may have influenced this time lag, such as (i) the amount of fine particles released by their respective sedimentary sources; (ii) the wind transport capacity; (iii) the local availability of sediments (role of vegetation and soil moisture). Among the various potential factors, fluctuations in the number of particles available for deflation due to changes in ice sheet pattern appear to be a pivotal point that explains the chronological disparities between aeolian systems.”
  Line 330. OK. We will change to ‘During late MIS 3’.
  
  Citation: https://doi.org/10.5194/essd-2023-105-CC2
RC2:
'Comment on essd-2023-105', Anonymous Referee #2, 05 Aug 2023
The study “Last Glacial loess in Europe: luminescence database and chronology of deposition” by Bosq et al., aims to create a unique database of European loess osl dated chronologies and accumulation rates during MIS 1-MIS 3 period. The data appears robust, and the methods used are sound and appropriately applied.
In my opinion this is a comprehensive study which will be a significant contribution to the loess, geochronological and palaeoclimatological community. The manuscript itself is well-structured, language is appropriate, the methods ant data are well presented and the conclusions are sound. The figures are also well designed and complement the data accurately. I would like to highlight that the authors did an excellent job with the manuscript and I very much enjoyed reading it.
I recommend publication, however, I would only like for the authors to take into account a few of my questions.

Have you considered the dating resolution as a parameter when calculating MARs? In my experience, dating resolution can have a significant impact on the accurate calculation of MAR distribution over the investigated time period. Maybe you should mention that.

Have you thought on maybe applying an additional age-depth modelling method and compare the results? I acknowledge that this would be a large amount of additional work, but often different modelling software produces different results. It would be interesting to see the discrepancies. This is just a thought, not a critique point.

Have you thought of expanding the investigation beyond MIS 3? I do know that these chronologies are very scares, but there are some studies from the Carpathian Basin where LPS were dated beyond MIS 5.

I think it would have been interesting to compare these results with MARs from LPS outside of Europe (e.g. Chinese Loess Plateau). We might get a better insight into the atmospheric dust activity on an intercontinental scale. However, I do recognize that this might be beyond the scope of this paper. Please take this just as an idea and/or a suggestion.
Citation: https://doi.org/10.5194/essd-2023-105-RC2
- AC1:
  'Reply on RC2', Mathieu Bosq, 09 Aug 2023
  
  Please find our responses (in blue) in the attached document
  
  Citation: https://doi.org/10.5194/essd-2023-105-AC1
  - RC3: 'Reply on AC1', Zoran Peric, 09 Aug 2023
    
    I thank the authors for their responces.
    All my questions have been appropriately and satisfactory answered which is why I recommend publication with no further changes.
    
    Citation: https://doi.org/10.5194/essd-2023-105-RC3

Mathieu Bosq et al.

Supplement

https://doi.org/10.5194/essd-2023-105-supplement

Data sets

ChronoLoess Database (v1.0.0) M. Bosq, S. Kreutzer, P. Bertran, P. Lanos, P. Dufresne, and C. Schmidt https://doi.org/10.5281/zenodo.7728616

Mathieu Bosq et al.

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Short summary

During the last glacial period, cold conditions associated with changes in atmospheric circulation resulted in the deposition of widespread loess. It seems that the phases of loess accumulation were not strictly synchronous. To test this hypothesis, the chronology of loess deposition in different regions of Europe was studied by recalculating 1423 luminescence ages in a database. Our study discusses the link between the main loess sedimentation phases and the maximal advance of glaciers.


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