the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 31 Jul 2026
The First Aminostratigraphies for the Quaternary of the Swiss Plateau
Abstract. Here we develop an amino acid chronology to help establish a dated sequence for the important Early Pleistocene Höhere and Tiefere Deckenschotter morphostratigraphic units, as well as other Middle and Late Pleistocene deposits from across the Swiss Plateau. The intra-crystalline protein decomposition (IcPD) in a variety of calcium carbonate biominerals (including novel and rarely-analysed taxa) was used to develop the first aminostratigraphy for this region of central Europe. Age discrimination is possible between the Quaternary sites from the Swiss Plateau in six different biominerals: Bithynia opercula, shell fragments from Fruticola, Arianta and Cepaea, slug plates and worm granules. This chronology is compared with new and existing dating information derived from lithostratigraphy, palaeomagnetic data, biostratigraphic data (pollen, small mammals) and numerical dating methods (such as OSL/IRSL, U/Th, cosmogenic nuclides), as well as new biostratigraphic data derived from a study of Early to Late Pleistocene molluscan faunas from the Swiss Plateau. These new aminostratigraphies provide a relative chronology and give crucial new age information for a number of key sites from across the Swiss Plateau, which helps to fill major gaps in the Quaternary chronology for Switzerland.
Status: final response (author comments only)
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RC1: 'Comment on egusphere-2026-4013', Anonymous Referee #1, 02 Sep 2026
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AC2: 'Reply on RC1', Kirsty Penkman, 09 Oct 2026
We thank RC1 for their insightful comments, and respond to their suggestions for improving the manuscript below.
1. HDS opercula, the challenges of being close to equilibrium, and the interpretation of the Irchel Plateau: The general rare occurrence of opercula in the investigated archives, and especially in the Deckenschotter records gave us a very interesting conundrum. This was the reason why we had to try other biominerals to enable differentiation of the HDS and the TDS. We agree with the reviewer that when nearing equilibrium, the increased peptide bond hydrolysis in these older samples means that more and more of the THAA fraction is actually composed of FAA when behaving as a closed system. This results in the 2 measurements providing less independent time-information, but the crosscheck is still useful as divergent samples become evident. We have added a sentence to the manuscript to clarify this point.
There are two interpretations of the age of the Irchel Plateau, where the cosmogenic radionuclide data conflicts with the biostratigraphy. This is discussed in more detail in Thew et al (2024; https://doi.org/10.1016/j.quascirev.2024.108550), where the AAG from slug plates supports the interpretation that the Irchel Ebni Silts are older than the Hasli Formation, and that the youngest cosmogenic dates are not supported. We have added text to the manuscript to clarify.
2. Impact of temperature: The reviewer makes an important point that temperature and burial histories are important, and significant differences in integrated thermal histories (due to burial depth or climate) will result in differences in D/L value in material. The impact of 1-2 degrees on the rates of the reactions is hard to quantify, as 1-2 degrees at a lower temperature will have less of an effect than 1-2 degrees at higher temperatures, due to the exponential impact of temperature. This is also an accumulative effect with time (e.g. Nelson et al., 2026), so younger samples may not be impacted (within analytical uncertainty), while the effects will increase for older samples. However, over this relatively small geographical area, based on the relationship between IcPD and temperature in other regions, we have had to assume that the integrated temperature histories are relatively similar, and now clarify this in the manuscript. The impact of burial depth is interesting: work undertaken in the Pannonian Plain (Nelson et al., 2024) and the Upper Rhine Graben (Nelson et al., 2025) (regions that have a steeper than average geothermal gradient for continental crust (40-50℃/km)) has shown that for samples buried at depths > 80 m where burial temperatures are ≳14-15℃ and opercula are older than ~450 ka, significant differences in D/Ls were observed for equivalent age opercula recovered from different burial depths, and therefore the geothermal effect needs to be accounted for in those cases. However all the samples in this study were buried < 80 m at the time of excavation (although we don’t know how much material could have been removed through erosion). In the Swiss Plateau, where the geothermal gradient (25-40℃/km) is not as steep as other regions already examined, such differences are likely to be small, and are unlikely to impact the relative order presented here. However we have clarified these two aspects in the manuscript, and added current temperatures for each of the sites in the SI so that the readers can incorporate these into their assessment of the data.
3. Quantitative comparisons between biominerals: This is the ultimate aim, but the pilot nature of the dataset means that we have not yet attempted to make the quantitative comparison; as stated in the conclusions, given the high variability seen in some of the biominerals, we do not feel we have a good enough assessment of the natural variability within a biomineral & horizon to make these inferences. By setting out the potential of these materials in this region, it is hoped that this stimulates further work that would enable these quantitative comparisons to be made in the future.
4. Ser data: Both [Ser]/[Ala] and D/L Ser were available in the supplementary files associated with the paper, accessed via a link in the manuscript webpage that directed to https://zenodo.org/records/21293656.
Citation: https://doi.org/10.5194/egusphere-2026-4013-AC2
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AC2: 'Reply on RC1', Kirsty Penkman, 09 Oct 2026
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RC2: 'Comment on egusphere-2026-4013', JoseEugenio Ortiz, 06 Sep 2026
This manuscript addresses a long-standing challenge in Alpine and European Quaternary geology: establishing robust relative chronologies for fragmentary and highly dynamic glacial/interglacial deposit sequences on the Swiss Plateau. By systematically applying intra-crystalline protein decomposition (IcPD) across six distinct carbonate biominerals—including rarely analyzed or novel taxa like calcitic slug plates, earthworm granules, and aragonitic Fruticola shells—the authors construct the first comprehensive regional aminostratigraphic framework for Switzerland.
The study provides important new constraints on key morphostratigraphic units, particularly the Höhere Deckenschotter (HDS) and Tiefere Deckenschotter (TDS), while offering independent geochronological tests for Middle and Late Pleistocene archives. The data quality and analytical approach are strong, and the manuscript is overall well-written and logically structured.
The authors provide a thorough background on the four classic Swiss morphostratigraphic terrace units (HDS, TDS, HT, NT). The site descriptions for all sites are detailed and well-referenced.
Regarding the methodological innovation, expanding IcPD analysis beyond traditional indicators (Bithynia opercula) to include terrestrial gastropods (Arianta, Cepaea, Fruticola), slug plates, and earthworm granules greatly expands the utility of aminostratigraphy across varied sedimentary facies.
It is of wide regional significance, as it fills major geochronological gaps in the Swiss Quaternary archive, offering independent age evidence that refines those obtained by other methods (e.g., within the HDS at the Irchel Plateau and Albishorn-Bürglen).
Nevertheless, I have the following recommendations for the authors which can help to increase the high quality of the work done:
1.-In the Methods section it is said that [Ser]/[Ala] and D/L Ser ratios were used, but they were not presented in the Results section and nothing in commented.
2.-I find important to include the plots of Asx and Val in Figures 3 to 9, and not only Glx and Ala as the results of these amino acids are discussed in the text.
3.- It would be important to include a table (or Figure) showing the D/L value ranges for each amino acid and taxon characteristic of each period (at least, Early Pleistocene, Middle Pleistocene, Late Pleistocene, Holocene) as hte key of this study is to provide the aminostratigraphies for the Swiss Plateau.
4.- Zell 2019 vs. Niederweningen Comparison: Arianta and slug plate data from Zell 2019 exhibit slightly higher/equal IcPD values compared to Niederweningen, despite Zell representing an early Eemian/MIS 5 phase. I would recommend to discuss briefly whether subtle microclimatic or thermal history variations across the Swiss Plateau could account for these minor offsets, or other reasons.
Minor suggestions:
Line 146. The year of Preusser et al.´s work is incomplete.
Line 154-155. Delete “for the upper part of the HF” as it is repeated.
Line 155. Change “final part” for “end”.
Lines 916 and 917. A comma is missing in the cites.
Congratulations for this very interesting study.
José E. Ortiz
Citation: https://doi.org/10.5194/egusphere-2026-4013-RC2 -
AC1: 'Reply on RC2', Kirsty Penkman, 09 Oct 2026
We thank R2 for their helpful review, and our responses to their recommendations are below:
1: Ser data presentation: both [Ser]/[Ala] and D/L Ser were available in the supplementary files associated with the paper, accessed via a link in the manuscript webpage that directed to https://zenodo.org/records/21293656.
2: Plots of Asx & Val: We agree these plots are important, and they were available in the supplementary files associated with the paper, accessed via a link in the manuscript webpage that directed to https://zenodo.org/records/21293656
3: D/L value ranges for each AA, taxon & period: This is an interesting idea; the concept of aminozones is extremely valuable and has provided considerable insight in many AA geochronology studies. However, we argue that in this case, defining aminozones (i.e. D/L value ranges) is not appropriate at this early stage. The nature of the slowing of the protein diagenesis during the cold stages in the region studied here means that there is very little degradation between the end of one warm stage and the beginning of the next. This, compounded with the natural variability in the biological data, means that the data may approximate to a continuum. Therefore the authors feel that defining a rigid boundary at this time is not appropriate, especially given the small number of samples analysed per horizon in this preliminary study, meaning these boundaries would likely change with analysis of further samples. In this paper we prefer to present the whole dataset, with the correlations named/colour coded based on the independent evidence of age. New analyses can be directly compared to this study by any reader in order to determine the most likely correlation, as the absolute values are provided for each of the amino acids. We hope that by using this approach, the amino acid data will not be over-interpreted, which has previously had unforeseen and unfortunate consequences; McCarroll (2002, Journal of Quaternary Science; https://doi.org/10.1002/jqs.690) discusses some of these issues. As all the data are presented in the SI, it is possible for readers to use this to define their own aminozones if required. We have modified the text to articulate this approach more clearly.
4: Zell vs Niederweningen: The Zell 2019 samples come from early Eemian layers, whereas the Niederweningen samples come from early/mid Eemian to middle Eemian. So Zell 2019 would have a tendency to be similar or slightly more degraded than the Niederweningen sample, given a similar temperature history, which is what is observed in the Arianta and slug plate data. The MAT of these two sites is similar (Zell 9.29℃, Niederweningen 9.8℃), although with slightly higher mean summer temperatures at Niederweningen (18.37℃ vs Zell 17.58℃). Given the preliminary nature of this dataset for these biominerals, we do not feel it is appropriate to refine the interpretation further, but assessment of the natural variability within a horizon will help with this question, as mentioned in the manuscript text.
All the minor suggestions have been changed in the manuscript as requested.
Citation: https://doi.org/10.5194/egusphere-2026-4013-AC1
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AC1: 'Reply on RC2', Kirsty Penkman, 09 Oct 2026
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Cited
3 citations as recorded by crossref.
- An aminostratigraphy of the northern Upper Rhine Graben, Germany E. Nelson et al. https://doi.org/10.1002/jqs.70004
- Quaternary aminostratigraphies for the eastern North European Plain. E. Nelson et al. https://doi.org/10.12688/openreseurope.21815.2
- Quaternary aminostratigraphies for the eastern North European Plain. E. Nelson et al. https://doi.org/10.12688/openreseurope.21815.1
I enjoyed reading this manuscript. The scale of the work is considerable: 31 horizons across 21 sites, drawing on new fieldwork, museum collections and sediments archived decades ago. Much of this material could not readily be collected again, so the dataset has value in its own right, independently of the chronology built on it here.
The most useful contribution, to my mind, is the work on the new biominerals. The opercula are the only material for which a framework had previously been established, and they are absent from many of the sites studied here. The first IcPD data for Fruticola, and the first substantial datasets for Arianta, Cepaea, slug plates and worm granules, extend the method to terrestrial settings where Bithynia is not present. This should be of use well beyond the Swiss Plateau. I do have four questions that arose while reading.
My thanks to the authors for the interesting study, which I was glad to have the chance to read. I look forward to their replies to the questions above.