Rare Earth Element Concentrations as a Novel Proxy for Lateral Continuity: An Initial Case Study in the Cretaceous Lance Formation of Wyoming

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is a very well-crafted paper that surely deserves prompt publication on Minerals. 
I have no real criticisms to advance on it, though I would love to see some more comparisons with other bonebeds from the Lance Fm if such data are available. I see that chemical data on the Rose Quarry have been published, though I cannot access the relevant paper (McLain et al., Palaios, 2021) right now; why not including data from the Rose Quarry in e.g. the box and whisker plots in Fig. 12 as well as in other similar figures? More comparisons between the Neufeld + five main quarries and other vertebrate accumulations from the same formation may further strengthen the case for the two studied assemblages being consistent with each other and distinct from other nearby bonebeds in terms of bone chemistry.
In addition, I suggest including a schematic map showing the location of Wyoming in the USA in Figure 2 -- readers from outside North America may find it useful. 
Best regards, 

Author Response

Comment 1: This is a very well-crafted paper that surely deserves prompt publication on Minerals. 

Response 1: We thank the reviewer for their kind remarks on our manuscript.

Comment 2: I have no real criticisms to advance on it, though I would love to see some more comparisons with other bonebeds from the Lance Fm if such data are available.

Response 2: To address a few of the reviewer’s concerns, we are unaware of any other such geochemical analyses of other fossil bonebeds within the Lance Formation beyond the study by McLain et al. (2021) of the Rose Quarry, which we frequently compare against. Though this is unfortunate, we are hopeful that this study will inspire similar future studies of additional fossil localities in the Lance Fm. and beyond. 

Comment 3: I see that chemical data on the Rose Quarry have been published, though I cannot access the relevant paper (McLain et al., Palaios, 2021) right now; why not including data from the Rose Quarry in e.g. the box and whisker plots in Fig. 12 as well as in other similar figures? More comparisons between the Neufeld + five main quarries and other vertebrate accumulations from the same formation may further strengthen the case for the two studied assemblages being consistent with each other and distinct from other nearby bonebeds in terms of bone chemistry.

Response 3: Given that the Rose Quarry offers the only other site we could currently compare to, we have incorporated the reviewer’s advice to include more comparisons to that quarry, including making an additional visual comparison to the Rose Quarry in our Figure 9. We thank the reviewer for this suggestion, as we feel this addition greatly helps portray contrasts between the Rose Quarry and the Neufeld and “Main Quarries” that further support our conclusion that the latter two bonebeds are equivalent. 

Comment 4: In addition, I suggest including a schematic map showing the location of Wyoming in the USA in Figure 2 -- readers from outside North America may find it useful. 

Response 4: We also incorporated the reviewer’s recommendation to include a broader map of the United States into Figure 2A, so that readers from outside the region can get a better grasp of our sampling location. 

Reviewer 2 Report

Comments and Suggestions for Authors

 

The work is well-constructed and very well-written. The images and tables are well-designed.

However, the major weakness of this work is that we have to believe the authors that the technique produced satisfactory results based on a publication that does not yet exist. The authors are still preparing a more complete manuscript on the stratigraphic relationships between the two points analyzed. This prevents the experiment from being replicable.

The USA has several other locations where the authors could test the proposed methodology. However, since it was used in nearby areas, the authors should have discussed other possible causes for the results that could affect the findings beyond the conclusion presented. Based on this, I would avoid statements like those in lines 718-721, as this work can be framed more as a case study due to the lack of further testing in other locations.

Author Response

Comment 1: The work is well-constructed and very well-written. The images and tables are well-designed.

Response 1: We greatly appreciate the reviewer’s comments and critiques as they are all valid concerns. 

Comment 2: However, the major weakness of this work is that we have to believe the authors that the technique produced satisfactory results based on a publication that does not yet exist. The authors are still preparing a more complete manuscript on the stratigraphic relationships between the two points analyzed. This prevents the experiment from being replicable.

Response 2: We agree with the reviewer that the order in which our geochemical and our coauthors’ stratigraphic manuscripts are being published is not the ideal situation, but we can confirm that our coauthor’s stratigraphic findings will be sent for review soon. Our coauthors have shared their stratigraphic findings with us throughout this project, and we can also affirm that our geochemical conclusions have independently matched their stratigraphic conclusions (as noted in our manuscript). 

Comment 3: The USA has several other locations where the authors could test the proposed methodology. 

Response 3: We also agree that our applied methodology could be used to assess potential cases of lateral continuity at many other locations across the US and abroad, and in the future we hope to conduct similar comparative geochemical analyses of other sites and fossil bonebeds, which would serve as very useful and informative additional tests of our hypothesis in this manuscript. 

Comment 4: However, since it was used in nearby areas, the authors should have discussed other possible causes for the results that could affect the findings beyond the conclusion presented.

Response 4: We also agree with the reviewer that our conclusion of lateral equivalency, though well-supported, is not a certain fact, and we have therefore considered alternative causes for the geochemical similarity between the Neufeld and HR Bonebed “Main Quarries” both in the manuscript and through our process of making revisions. We believe our detailed comparisons (in the Discussion) to the nearby Rose Quarry, an attritional bonebed also within the Lance Formation (and the only other bonebed within this Formation for which trace element analyses have also been conducted; McLain et al., 2021), maximize our ability to identify both potential themes in chemical alteration to bones within the Lance Fm. in general (such as the common observation of Eu and Ho enrichment relative to neighboring REEs; see lines 572-589 of our revised manuscript and Ullmann et al. [2025] page 9 for further discussion) and potential contrasts among bonebeds preserved in close proximity to one another within this Formation. As highlighted through our Discussion, we identified a number of geochemical contrasts between the Rose Quarry and the other two bonebed localities which could not arise merely by Neufeld and the “Main Quarries” sharing a mass-death style of accumulation, as these contrasts are in chemical signatures primarily imparted after burial (Trueman et al., 2004). Thus, contrasts between the Rose Quarry and the two main sites of emphasis in our study, the Neufeld Quarry and HR Bonebed “Main Quarries”, strongly support our conclusion that the latter two bonebeds are equivalent. We have therefore attempted to highlight these contrasts further through adding a visual comparison to the Rose Quarry into our Figure 9, as a new panel C in this figure. Significant chemical contrasts alike those now shown visually in Figure 9 strongly imply chemical heterogeneity among Lance Fm. paleoenvironments, which makes the possibility that the Neufeld and “Main Quarries” randomly acquired similar trace element signatures highly unlikely.

Comment 5: Based on this, I would avoid statements like those in lines 718-721, as this work can be framed more as a case study due to the lack of further testing in other locations.

Response 5: We have also rephrased lines 718-721 of our original manuscript to address reviewer’s concern about the strength of the language in these sentences in our Conclusions section. Our study was indeed a case study, as the reviewer notes, which we acknowledged in our title: this method has not previously been to examine uncertain cases of lateral continuity of fossil vertebrate assemblages, but in the future we hope to continue testing other locations to further verify the validity of this approach. 

Reviewer 3 Report

Comments and Suggestions for Authors

I am pleased to read this paper; this work makes a valuable contribution to the field.  The material is commendable and important to the field. The material is laudable and represents a significant contribution to the field, and the descriptions are excellent. This paper is well-structured and illustrated.

This method of analysing trace elements from fossils should be applied to the material stored in the museum from old excavations, but without the stratigraphical locations. The problem with this method is that it is more expensive than the sedimentological facies analysis. And if we apply the statistical approach, then we have to sample more than 7 bones to have a correct view of the all material.

In conclusion, I have no issues with the submitted manuscript and can recommend its publication as it is.

Author Response

Comment 1: I am pleased to read this paper; this work makes a valuable contribution to the field.  The material is commendable and important to the field. The material is laudable and represents a significant contribution to the field, and the descriptions are excellent. This paper is well-structured and illustrated.

Response 1: We greatly appreciate the reviewer’s laudatory remarks regarding our manuscript. 

Comment 2: This method of analysing trace elements from fossils should be applied to the material stored in the museum from old excavations, but without the stratigraphical locations. 

Response 2: Similar studies have been conducted in the past to identify the horizon an out-of-place fossil bone eroded out from, but few to date have attempted to look through collections and identify where such specimens originated if no complimentary stratigraphic data exist. We hope that future work may aim to explore that line of questioning through further testing at other localities and in other geologic formations, as this was an initial case study exploring the potential of trace elements for this type of test.

Comment 3: The problem with this method is that it is more expensive than the sedimentological facies analysis.

Response 3: As the reviewer noted, we agree that traditional facies analyses are much cheaper than the methodology applied within this manuscript, and by no means are we attempting to replace such techniques; rather, we explored a potential alternative and complementary method that could be used to answer the same type of research question completely independent of traditional facies analyses. 

Comment 4: And if we apply the statistical approach, then we have to sample more than 7 bones to have a correct view of the all material.

Response 4: Finally, we agree that it would be beneficial to examine larger sample sizes from both quarries if that were possible, as that could indeed enable statistical testing of equivalency, but due to the destructive sampling required for this type of analysis, a higher sample size was not feasible; we examined the maximum number of specimens for which the collection manager approved destructive sampling. That being said, we would definitely be interested in future studies to potentially incorporate statistical testing into this new approach, if large enough sample sizes can be obtained. 

Comment 5: In conclusion, I have no issues with the submitted manuscript and can recommend its publication as it is.

Response 5: We thank the reviewer for their kind remarks. 

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors I read the authors' arguments and believe they took my concerns and suggestions
into consideration. I only ask that they continue to publish new applications
of the proposed method in other locations of stratigraphic interest. And most
importantly, that the most complete stratigraphic work on the location be published
as soon as possible.