The Hell Creek Formation, Montana: A Stratigraphic Review and Revision Based on a Sequence Stratigraphic Approach
Round 1
Reviewer 1 Report
This study is very interesting because it represents a complete stratigraphic review of the Hell Creek Formation (Montana, US). Furthermore, it offers new perspectives with the introduction of a sequence stratigraphic approach.
In my opinion it deserves to be published but not in its present form.
I understand it is a revision but the main problem is that the text is not fluent, even though I am not an native English speaker, but I imagine that not all the readers will be. For this reason, I strongly suggest to the author to revise taking care of this important aspect. My impression is that many parts can be pare down and periods/paragraph make shorter, because there is a high risk that the reader could get bored after a while. Also, I apologize for my English and my mistakes.
To further improve text revision, I have provided additional small comments in a separated file, with the indication of line number and/or figure (from the latest version formatted pdf). Some comments are just suggestions that I believe will produce benefit for the entire work, also in terms of discussion and main results.
Comments for author File: 
Comments.pdf
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
Thank you for giving me an opportunity to review your paper “The Hell Creek Formation, Montana: A stratigraphic review and revision, with implementation of depositional sequences”. This manuscript is overall well-written to present valuable information of the formation, and good to be a review paper. I appreciate author’s great effort. However, this paper is too long and descriptive. I think that it would be better to be shortened and integrated, particularly overlapping and minor parts in ‘Stratigraphy and Age’ and ‘Results’. I am interested in the study area but not familiar with it yet, thus my review approach was as reader/audience.
- In Introduction, please provide better the geographical overview of the Hell Creek Formation.
- I suggest an adjustment of the paper structure, due to too long Introduction section. For example,
- Introduction
- Geological Background? Geological Overview?
2.1. General sedimentological setting?
2.2. Stratigraphy and Age? Previous studies for Stratigraphy?
… - Materials and Methods
- Results
… - Discussion
… - Conclusions
- In Geologic setting, please provide tectonic history related to the formation of the Hell Creek.
- I think that the 'Stratigraphy and Age' section is too long (too much information and subdivided) and descriptive. It would be better to revise the contents more integrated.
- '3 Terrestrial Sequence Stratigraphy' section describes many of general ‘textbook’ concepts, part of which are unnecessary to be included in a research paper.
- The results can be compared to global sea-level change or published local eustasy curve? the global or local curves can be included in stratigraphy overview figures?
- Please remove ‘Figure 3’ from 3.1 Lithofacies and generalized section title.
- Please remove ‘?’ from 3.1.5 Battle Formation (Kba) title, or explain about it better in text.
- I suggest some change for the titles ‘3.2 Study localities and measured sections’ and ‘4.2 Time duration of depositional cycles’,
- Make texts clearer in images (ex. Figures 4, 10, 12, 22)
- In figures, add arrows to indicate key findings (ex. Figures 9, 29).
- In captions of Figures 21, 30, 34, please distinguish descriptions of A and B.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Reviewer 3 Report
The manuscript by Fowler, "A terrestrial sequence stratigraphic interpretation of the Hell Creek Formation of northern Montana" is a very well written, interesting and comprehensive account of the sedimentology of the Upper Cretaceous Hell Creek Fm and the basal Fort Union Fm of the Fort Peck Lake area, Montana, USA. The data and interpretations are based on several outcrop successions from Montana. The figures are very well prepared and informative. Nice work perfectly suited for the journal. However, there are a few issues that need to be adressed and revised before publication. I recommend a minor-moderate revision.
The main problem I find is the omission of the K-Pg boundary and any discussion of the event (apart from one or two very general sentences). This is missing in the introduction, previous works, in the descriptions of the successions hosting the K-Pg boundary, in the discussion and in the conclusions.
Although the paper is aimed as a broad stratigraphic framework of the Hell Creek Formation, one can not avoid to at least make a brief sedimentological description of the boundary clay with the rusty layer, spherules etc. If missing from the studied sections, this should be pointed out to the reader and briefly compared to the typical boundary clay successions elsewhere in the US and Canada, and an outline of the nature of the boundary in the studied successions should be included.
The same applies to the paleontology section. It would be good to state that numerous dinosaur fossils and fossils of other groups, are found below the boundary but not a single dinosaur bone above. That is possibly obvious for the author but not necessarily the case for all readers. The significant difference in fossil content between the successions below vs. above the boundary was definitely what amazed me as a participant on field work in the Hell Creek area.
The last paragraph concerning the 3 metre gap is to my knowledge outdated and not correct. The author has not referenced, for example, Lyson et al. 2011 -Dinosaur extinction: closing the ‘3 m gap’. Please include reference to this work that addresses this issue and also consider the references within.
References: There is a major under-referencing of works by Lyson and by Bercovici and also to more recent works by Fastovsky. Perhaps others that I did not note. These scientists have made major contributions to the field that are directly relevant to this study. No matter whether the author agrees or not with their overall conclusions. Please fix.
In summary; this is a great paper that would be very useful for students and scientists in the field and I am looking forward to see it published after the moderate revision.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
This paper is now ready to be published. The author considered most of my suggestions and incorporated those in the revised paper. I also mostly accept when the author denied it because he provided pretty good reasons (even though I do not completely agree with some of them).
I know I complained a bit about the fluency of the text, since I felt it not very fluid. I might not the right person to judge about English but I just complained mostly on the length of some parts. That’s all. This is my feeling as an “international reader”, concepts could have been more direct and concise. In general, the author improved it.
I understand that the author is a paleontologist, a “user of stratigraphy” but, considering the title of the paper, I imagined that he was going to facus more on stratigraphy than paleontology. I see his point and I agree. I could suggest him, for future studies, a sort of collaboration with stratigraphers. These outcrops are amazing and have a great potential also from a stratigraphic point of view.
Best luck
