the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 30 Jun 2026
A Phanerozoic-style icehouse climate in the middle Ediacaran
Abstract. Geological evidence points to icehouse conditions during the Ediacaran Period (635 to 538.8 Ma) both before and during the emergence of animals in the fossil record. However, the temporal and spatial distributions of Ediacaran ice sheets are not well constrained due to uncertainties in palaeogeography, chronostratigraphy, and the depositional settings of candidate glaciogenic deposits. Here, we systematically evaluate the evidence for the depositional ages of candidate Ediacaran glaciogenic deposits and establish the likelihood that each deposit was formed by ice-driven processes using observation-driven weighting criteria. Our analysis supports the existence of discrete mid- and late Ediacaran icehouse intervals (MEIH and LEIH respectively), each followed by greenhouse conditions. Focussing on the older MEIH, we integrate our quality-controlled geological dataset with climate and ice sheet model simulations to characterise glacial conditions during this interval (~593 to 579 Ma), which encompasses the ‘Gaskiers glaciation’. Our results indicate that the MEIH was a Phanerozoic-style icehouse, with latitudinally-constrained and fluctuating ice sheets, marking a break from the preceding Cryogenian snowball Earth motif, and occurring before the first known appearance of animals in the fossil record. By mapping robustly identified glaciogenic deposits onto contrasting middle Ediacaran palaeogeographic reconstructions, we show how these deposits can be used to constrain hypotheses of Ediacaran continental configuration.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-3617', Anonymous Referee #1, 27 Aug 2026
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RC2: 'Comment on egusphere-2026-3617', Anonymous Referee #2, 31 Aug 2026
Hearing et al. review Ediacaran glacial deposits and compile their latitudes in two paleogeographic models. They then construct climate and ice sheet models for the mid-Ediacaran glaciations. To my knowledge these are the first attempts to model the Ediacaran ice extent using real climate models and data. I think the review and modeling is useful for the community, to recognize that there is no strong evidence for low-latitude Ediacaran glaciation, nor any need for exotic geophysical phenomena, like inertial interchange true polar wander, to explain the data. I really appreciate how the authors discuss and depict the uncertainties in this model. This is the second time I have reviewed a version of this manuscript and it is much improved.
The paper is well written and I have few additional comments for improvement. My only suggestion is that Figure 5 could be improved a bit to have a bigger impact and be used more by others. Get rid of the dashed lines and the different shades—these are confusing and distracting. I don’t know why the authors use the dashes for the LEIH—just use the same paleogeographic reconstructions and finish this plot and maybe put a question mark for extent. Putting dashes down to the equator makes readers think that there is evidence that it could be global in extent. It is also unclear why they put the dashes from 635-580 Ma. There is no evidence for ice during this period, so they should delete this as it will perpetuate in the literature otherwise. It is also unclear why they make the Cryogenian solid, high latitude ice. There is no low-latitude ice from 661-640 Ma (see Tasistro-Hart et al., 2025, PNAS; Tasistro-Hart et al., 2026, Geology). Cleaning up this diagram will make the paper have a much bigger impact—people will actually use this and cite this. If you keep it confusing with weird dashed intervals, no one will use this and cite this because they would have to explain the weird dashed intervals.
Citation: https://doi.org/10.5194/egusphere-2026-3617-RC2 -
EC1: 'Comment on egusphere-2026-3617', Gerilyn (Lynn) Soreghan, 03 Sep 2026
Hearing et al. evaluate ages and depositional origins of Ediacaran glaciogenic (and candidate glaciogenic) deposits and combine these data with climate- and ice-sheet modeling to explore Ediacaran glacial history, ultimately inferring the existence of two icehouse intervals that behaved in a manner akin to the Phanerozoic icehouses (in contrast to snowball states).
I found the manuscript to be well and clearly written, and appreciated the clear and logical explanations of the age- and depositional “grading” systems, as well as the modeling, and assessment of paleogeographic constraints. Two reviewers also evaluated the manuscript.
Reviewers have provided detailed and constructive comments. Overall, I expect to be encouraging the authors to submit a revised version that addresses the comments and suggestions in the two very constructive reviews.
Citation: https://doi.org/10.5194/egusphere-2026-3617-EC1
Data sets
Supplementary Data T. W. Wong Hearing et al. https://zenodo.org/records/17158910
Model code and software
Supplementary Code T. W. Wong Hearing and A. Pohl https://github.com/twwh01/MEIH/
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This manuscript combines a systematic evaluation of glaciogenic deposits for the Ediacaran with climate and ice-sheet model simulations to explore the glaciation history during this time period. The authors find evidence for two discrete icehouse intervals in the middle and late Ediacaran (MEIH and LEIH, respectively). Based on the combined evidence, they suggest that the MEIH was a "Phanerozoic-style" icehouse and provide some constraints on uncertain paleogeographic reconstructions at the time, which I find a particularly interesting thought and contribution, albeit challenging because of other uncertainties.
Overall, this is a very good and important paper which I would like to see published after revision. My major concerns relate to the discussion of uncertainties in terms of paleogeographic reconstructions and model parameters, see my detailed comments below. I hope these remarks will prove useful to the authors during revision of the manuscript!
Specific comments:
l. 94: For clarity, it would be good to specify here whether this is just reproduced or updated (updated according to the main text). It would also be helpful to describe the changes relative to the version published earlier somewhere.
l. 194-204: When first reading this paragraph, I had wondered whether it would be useful to show the different reconstructions somewhere, in particular the topography of the PALEOMAP reconstruction because of its importance for ice-sheet formation, and realised only later that they are shown in the Supplementary Information. It would be good to refer to the respective figure in the SI in this subsection.
l. 225: Please specify the present-day value used to scale the Ediacaran solar luminosity (it appears to be higher than the generally accepted value of about 1361 W/m2).
l. 308, subsection 3.2: I am missing a bit more discussion here, in particular concerning Fig. 3 and the plausible glaciogenic deposits deep in the tropics.
l. 315-317: This is a bit confusing because the reader might interpret the "lower latitudes" in comparison to the ones in the PALEOMAP reconstruction rather than lower latitudes absolutely. I would suggest to rephrase the sentence to avoid the confusion.
l. 336-337: This is a bit confusing. This selection does obviously not include the MEIH deposits, right? This should be explained better!
l. 346-348: This is too vague. You should be able to explore the mechanism based on model diagnostics.
l. 351-353: Could be moved to the Methods section. Also, could you comment on whether the ice sheet is approaching equilibrium at this point?
l. 386: "[S]ome uncertainty" seems rather euphemistic, please delete "some".
l. 400-402: Well, yes... and no... You should keep in mind that topography is usually rather uncertain as well and that high topography at low latitudes could lead to glaciation in terms of glaciers on tropical mountains.
l. 404-406: This cannot be the only reason since the radiative forcing from the change in CO2 is more than twice the radiative forcing from the change in the solar constant, if my back-of-the-envelope calculation is correct.
l. 408: One thing your equilibrium simulations also do not take into account is that orbital forcing is continuously varying in reality. This should be discussed somewhere.
l. 441: I agree. Ice-sheet models are particularly sensitive to the choice of certain model parameters, something which is not discussed in the manuscript!