the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 23 Feb 2026
AstroComb(v.1.0): Non-linear, Multi-channel, Probabilistic Cyclostratigraphic Analysis
Abstract. We present a new algorithm for constructing floating astronomical timescales with explicit uncertainty estimates from sedimentary sequences. The method integrates probabilistic spectral analysis with inverse geochronological modeling, applied to ultra-high-resolution, multiproxy datasets such as core scanning X-Ray Fluorescence (XRF) elemental records. Our framework does not smooth data or impose layer-to-layer dependency, allowing sedimentation rates to vary abruptly at short stratigraphic length scales. By detecting and statistically constraining Milankovitch cycles preserved in stratigraphic signals, the algorithm seeks a floating age-depth model that can be anchored to astronomical tie points, where available. The resulting timescales enable precise, uncertainty-bounded timing of biostratigraphic zones, geochemical events, and depositional cycles. This approach advances astrochronology by combining cycle detection with formal stratigraphic modelling, while preserving fine-scale depositional variability, offering a reproducible and statistically rigorous framework for dating deep-time records.
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Status: open (until 20 Apr 2026)
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RC1: 'Comment on egusphere-2025-6145', Valentin Zuchuat, 24 Feb 2026
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EC1: 'Reply on RC1', Thomas Poulet, 05 Mar 2026
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Dear Dr Zuchuat,
Thank you very much for your thoughtful review. Your comments regarding the use of sans‑serif fonts in the journal templates and the suggestion to include an AI‑tool disclaimer are duly noted. I will forward these recommendations to the journal office for their consideration.Best regards,
Thomas Poulet.
Citation: https://doi.org/10.5194/egusphere-2025-6145-EC1
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EC1: 'Reply on RC1', Thomas Poulet, 05 Mar 2026
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Review of manuscript “AstroComb(v.1.0): Non-linear, Multi-channel, Probabilistic Cyclostratigraphic Analysis” by Fernandes et al.
Dear editor, dear authors,
I would like to thank you for giving me the opportunity to review the manuscript titled “AstroComb(v.1.0): Non-linear, Multi-channel, Probabilistic Cyclostratigraphic Analysis” by Fernandes et al. The manuscript introduces AstroComb, a probabilistic, multi‑channel cyclostratigraphic algorithm that estimates locally varying (possibly discontinuous) sedimentation rates by fitting Milankovitch targets in the frequency domain. The method is demonstrated on high‑resolution CS‑XRF records from the late Cambrian Alum Shale (Fågeltofta‑2 core) and on synthetic data with very high red noise. Both code and data are openly available, which I command the authors for!
The new workflow presents some strong innovative features, notably including the omission of smoothing, that allows for abrupt sedimentation-rate fluctuations to be considered, accompanied by an uncertainty estimate. As a sedimentologist and basin stratigrapher, this attribute is extremely powerful.
The manuscript requires some updates, though, in order to be accepted for publication in EGUSphere.
My first comment is not directed at the authors, but at the journal editors. Please invite the journal to update their templates with new sans-serif fonts. Indeed, with-serif fonts (e.g. times new roman), which are the ones used in EGUSphere templates right now, are much more difficult to read than sand-serif fonts (e.g. arial), especially for people with vision impairment or reading difficulties. I would also suggest to add a “Use of AI-tool” disclaimer at the end of the manuscript.
The manuscript requires major revisions to be accepted for publication. I would suggest the authors to address all the following comments, as well as the detailed comments on the commented-pdf attached to this letter.
I recommend the authors to acknowledge autogenic processes and signal shredding explicitly (rivers/deltas, compensational stacking; see commented pdf for references examples). It is also necessary to clarify how AstroComb distinguishes or remains agnostic to these signals vs. orbital forcing. The authors could consider adding a short paragraph in Introduction and returning to it in Discussion. An easy way to start with this is to take some of the text from the “limitations” chapter.
I also suggest the authors to avoid the term “geological noise” for non-Milankovitch periods. The preserved signal might not be “noise”, but rather the true expression of the mix of autogenic processes, Milankovitch cycles, and other non-linear effects such as bundling of several cycles. It is also important to justify why AstroComb does not include such periods (lines 311-314).
Other software are briefly mentioned (l. 31-33). Also this paper remains quite diplomatic about how much better AstoComb is in comparison to these other software, the reader of this manuscript could do with a figure that displays how the different software deal with the same input dataset.
The manuscript also only use single elements or several single elements together. A lot of published research (see references in the attached commented pdf) study change in Earth System conditions through the use of elemental-concentration ratios as well as enrichment factors. It could be useful to show how AstoComb responds to elemental-concentration ratios and enrichment factors.
Finally, it would be beneficial for the manuscript to compare the results from the conformable Alum Shale Formation to other sedimentary-cores XRF scans much more impacted by event beds, hiatus, or vacuity. This would allow the authors to highlight how AstroComb deals with these extreme changes in sediment supply. If this is not possible, please add a short demonstration in addition to your synthetic example, or at least discuss applicability in greater detail. Doing so would allow you to confirm, precise, or disagree with published sedimentation rates of other sedimentary units.
I would like the authors to add in the method chapter a paragraph on their XRF data collection workflow: add model, tube type, kV/mA, measurement time, temperature, calibration/normalisation, etc. The authors could also cite the paper that generated these data in the first place.
I would suggest to move beyond “visual examples” and describe the results in great details. For instance, the figures displaying the age-model: how does this relate to the sedimentation rates? Where do abrupt changes occur (e.g. line 326); how large are these abrupt changes; over what thickness/time do they occur; what geological interpretations are plausible? Why are some intervals “less Milankovitch” than others in your “information content” curve, tie all of this to core observations and geochemical data.
I would also recommend the authors to have all the figures 3-4-5-6-7 plotted as a one-pager figure together. This will allow for a much easier comparison between the single-element run and the multiple single-element run. Additionally, to tie this comment back to the previous one, please quantify the difference between the to runs, rather than having these results as visual examples. And add the elemental curves used for each runs to these figures.
Doing so will allow the authors to expand the discussion to the interpretation of the succession they have studied in great detail.
I would invite the authors to highlight and indicate more features on their figures: for example, where are the sedimentation rates changing “abruptly”, whare are the “spurious features” that “could be interpreted as true sedimentation rate” (l. 289-290), etc.
I would suggest adding element-curves to Fig. 3-6-10 next to the information content curve, which x-axis need to have a unit or an explanation as to why it doesn’t have one. Add proposed sedimentation rate curves on all probability plots, just like you have done on Fig. 10. The authors are also invited to quantify the difference between the two runs.
The authors are also invited to combine Fig. 8-9-10 in a one-page figure as well. Please rotate the Fig. 9 to have the depth as a vertical axis, just like all the other figures. Please quantify the impact of “However, the test also shows how artifacts are introduced by the noise, the variability of the true model, and the non-linearity of the problem” (caption of Fig. 10), which are concept that should be discussed in greater detail by the authors, especially with regards to the results of the studied core Fågeltofta‑2.
Please check the journal reference formatting, as there seem to be many unnecessary parentheses when multiple references are cited in the text.
Please chose and stick to “ky”, “kyr”, or “kyrs” for consistency. Similarly, always call the core Fågeltofta‑2, rather than a mix of Fågeltofta‑2 or Fågeltofta (e.g. caption of Fig. 2, or l. 304, 326)
Please use the official chronostratigraphic series name Furongian as opposed to late/upper Cambrian.
If the authors have any questions on my comments, please feel free to contact me directly.
Dr Valentin Zuchuat