Middle Eocene Rhodoliths from Tropical and Mid-Latitude Regions

Round 1

Reviewer 1 Report

The ms by Aguirre and colleagues is an interesting comparative study of the middle Eocene Rhodoliths from tropical and mid-latitude settings. The paper is well written and clearly presented and the results are significant in paleontological, ecological, and paleoenvironmental studies.

I have a few small corrections/suggestions:

line 95 complete the sentence

show Sierra del Zacatin in the map of Fig 1

the section 3. Study areas. Location and geological settings should be moved before the 2. Materials and Methods

Yours sincerely

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Major comments:

 

Lines 96 ff.: My most important request for this contribution is that you add stratigraphic logs for each studied section. For these logs the stratigraphic correlation of the sections should also be given, otherwise it is not clear, if the different samples are more or less contemporaneous. Ideally, a sequence stratigraphic interpretation should be given for each stratigraphic log in order to evaluate the influence of sea-level changes on rhodolith occurrence. If possible, at least a qualitative assessment of rhodolith abundance should be given for the beds of each section. The exact sampled beds have to be indicated on the logs.

 

Lines 299 ff.: Are there any independent indicators for the nutrient regime of your specific studied sections, e.g. geochemical data? A paleographic world map of the middle Eocene with rhodolith occurrences indicated would probably be helpful in stressing your point further.

 

Lines 306-307: This section needs to be more specific: Please provide images of accompanying fauna and their distribution along the sections in stratigraphic logs. There you can also indicate the specific beds with their sedimentary features.

 

Lines 332-333: Please discuss the Amazon reef complex in this context. Are rhodoliths present there? What is the relationship with nutrients?

 

Lines 392-393: Please indicate if there is any concrete evidence for upwelling influence in your specific studied sections in the Dominican Republic and Colombia.

 

Minor corrections:

 

Line 21: Correct to “decrease”.

 

Lines 22-23: “from two tropical localities”

 

Line 26: “and were redeposited into deeper”

 

Line 27 and other: I prefer the grammatically correctly derived “planktic” over “planktonic”. In other instances, you also use “benthic”, so the derivation of these terms should be consistent.

 

Line 34: “diverse” instead of “diversified”.

 

Line 44: Delete “particles”.

 

Line 51: “The oldest records of calcified coralline algae are Early Cretaceous fragments…”, use early and late when referring to age and lower, upper when referring to rocks.

 

Line 52-53: “Coralline algae became important carbonate components during the latest Early Cretaceous, and rhodoliths became increasingly common during the Late Cretaceous.”

 

Line 60: “coralline algae”.

 

Line 64-65: “The Eocene was a transient period between global greenhouse and icehouse conditions.”

 

Line 65: “rose”

 

Line 68: “drastic cooling at the”

 

Line 73: Delete semicolon, change “by” to “of”.

 

Line 90: “southern Spain”

 

Line 90: “precluding the extraction of”

 

Line 95: Stored where?

 

Line 124: “southernmost extension”

 

Line 144: “studied rhodoliths”

 

Line 148: “planktic”

 

Line 218: Change “anecdotal” to “rare”.

 

Line 261: “studied rhodoliths”

 

Line 267: “Late Cretaceous”

 

Line 269: “underwent a general temperature decline.”

 

Line 304: “shown”.

 

Line 377: “benthic foraminifers”

 

 

Figures and Tables:

 

Table 1: Thin sections per area is not really meaningful, if this is not normalized to the number of studied beds or similar.

 

Fig.1: Water is colored in blue in C and D, also color the Mediterranean Sea blue in A for consistency. Should also be consistent in the other maps.

 

Fig. 5: Some scale bars are difficult to read, consider adding contours to the bars and numbers. Add that these are linear polarized light thin section images (as I assume they are).

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Dear editor and authors of the manuscript:

The manuscript deals to the paleoenvironmental interpretation of middle Eocene rhodoliths of four representative areas with different paleolatitudinal contexts. It is well structured, and, in my opinion, a very interesting contribution of a temporal interval with global climatic changes. Nevertheless, a carefully reading of the manuscript highlight some important points that, in my opinion, need clarification and reestructuration.

Therefore, I consider manuscript under the status “moderate review”, since some changes need to be made before publication.

 

Please, contact me if you need a clarification or further explanation.

 

Introduction

* The introduction offers a very detailed approach of the topic with profuse literature review.

 

* Line 45, rock record?, I suggest: geological record, or sedimentary record, more appropriated.

 

Materials and methods

 

* Line 94, 95: Please, end the sentence. “All the analyzed sections are stored at”.

 

* Include also where are stored the studied fossils.

 

Study areas

 

*Very important issue:

Figures 2 and 3:

I consider Figure 1 (and the next figure 2) overmuch simple. It is only the geographical location, and this is a geological and paleontological manuscript.

Both figures needs the name of the roads, rivers, etc. Caribbean sea can be in blue, for example.

Instead these simple images, I suggest to include the google earth image of each study zone, and in these image mark the road, outcrop, etc.

 

* Geological map:

This is a paleo paper, and no geological map is included. I consider necessary incorporate a synthetic geological map of each sampling zone. The authors can redraw from previous geological maps.

 

* Field images of outcrops/stratigraphical sections

I think the paper will be improve with field images of the outcrops. I suggest to incorporate new figures related to the outcrop images.

 

* In the study areas description, a stratigraphic section is described, but there is no column in any figure of the paper. I suggest including representative section of each study area.

 

Results

 

* Table 1 shows among other parameters relative abundances (%) but in materials and methods any consideration is made related to how the authors calculated these percentages.

*Additionally, in my opinion, the number of thin sections of site is not a representative parameter. Which kind of information offer the number of thin sections made (n)?. Please, clarify. The number of individuals identified depends on the density (fossils per gram or area) not to the number of sections made. I cannot understand the information related to number of sections.

 

* Line 158:

In figure 4A “foraminifera rich marls” but no data about the species, percentage is showed in the text. The genera or the species of this levels can be interesting information to the paleoenvironmental interpretation.

 

* The paper needs and appendix with all the taxa cited.

 

*Figure 4. I consider, in my opinion, necessary to include more images of the rodholiths in the field (there is only one figure) and this is a “paleontological paper” related to Rodholits.

 

* Figure 4F. Which genera o species of benthic forams is showed?, may be this is interesting information to the paleoenvironmental interpretation.

 

* Very important: No field image of Dominican Republic rodholits; please include photos.

I suggest to include a new figure with more detailed outcrop images, where is possible to recognise the rodholits facies in each study section.

 

Discussion

5.1. Paleoenvironmental interpretation

 

* Line 226.

“However, the sediment engulfing the rhodoliths is rich in planktonic foraminifers characteristics of deep environments”

This is a very simplistic reasoning.  The authors use this argumentation to suggest reworking. But no data related to this level about the species or percentages of planktonic forams is included in the text. Just an only sieve of an unique sample can offer this very interesting information to the paleoenvironmental reconstruction. 

“The micropaleontological content suggests that these rhodoliths are displaced from their original place of growth”

*And here, which is the meaning of deep environments?, outer shelf?, bathyal?,

 

*Line 233. Which genera of species of LBF?,

 

*Line 240. No field images of rodholits is presented in the manuscript (Dominican Republic)

 

*253-254. Very interesting sedimentary information, but, as in several parts of the paper, no field images (figures) or stratigraphical section of the text description

 

5.2. Taxonomic composition

 

*Figure 5. Again no thin section image of Dominican Republic rodholits.

In my opinion, this is a paleontological paper, and for this reason it is not enough the fossils images in the manuscript, Almost 55 thin section and only 8 images in figure 5.

 

5.3.

*From line 317 to 365

To my mind this part of the discussion seems a review of the topic, not a discussion chapter where the results are analyzed in general context and compared to similar contexts. Seems a very interesting review but not directly related to the data presented in the paper. I suggest to separate this section from the discussion and put in separate section as a review of the topic. 

 

Suplementary material

* I consider table 2 a very interesting review of the topic, I suggest to include this table in the text.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

This manuscript has now been improved significantly, especially in the way the data are presentend. I do not have any further suggestions or comments, except that the authors should do some minor spell checking for the final version.