Mineralogy of Fossil Wood from the Miocene Goderdzi Formation, Republic of Georgia

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

This manuscript presents a novel and interesting study of the fossil woods of the upper Miocene-lower Pliocene Goderedzi Formation in Georgia. The manuscript mainly focuses on the mineralisation types in woody trunks, including mineral polymorphs such as Opal-A, Opal-CT, and microcrystalline Quartz/Chalcedony, in varying proportions. In my opinion, the authors do a great job describing them, using the petrographic microscope, SEM, X-ray diffraction analyses, and density determinations as their main tools. I recommend publishing this MS after incorporating the revisions I mentioned in this report.

However, my main concern about the manuscript is that it reads more like a guide or report on identifying different types of fossil woods than a research paper for a magazine, and this is because it lacks a proper discussion section. The discussion section is barely 15 lines and lacks comparisons or interpretations. Therefore, the authors need to compare their results with other coeval or non-coeval studies of fossil woods and with previous works on the floras of the Goderedzi Formation.

Following my previous suggestion, the article also needs more references, particularly when writing the new discussion section.

Additionally, the MS is missing a conclusions section, which should be written once the new discussion section is completed.

Finally, the English is well written and idiomatic, but I have spotted many mistakes, such as misspelt words and missing letters within words. I have listed most of them below in “Minor issues”, but I truly recommend that the authors check the text thoroughly because there can be more mistakes.

 

Minor Issues:

Line 10: Change “Upper Miocene-Lower Pliocene” to “upper Miocene-lower Pliocene”, with lower case as they are not formal subdivisions in the current IUGS stratigraphic chart. Please revise this issue in the entire MS.

Line 23: I think this sentence (“Georgia Republic is a small independent nation located west of the Black Sea ”) is unnecessary since it is basic geography knowledge.

Lines 27-28: “fossiliferous formations”. Avoid using the word “formation” here, as it can be confusing with the geological unit you mentioned before, “Goderdzi Volcanic Formation”. Rephrase or use a more suitable word.

Line 37: Change “Late Miocene” to “late Miocene”. See the comment in line 10.

Figure 1: The world map is too large just to show Georgia as a very small red stain in the centre of the image and thus takes up unnecessary space of the MS to convey basic geography knowledge. Better combine it with the geological map from Figure 2 and explain each map in the figure caption.

Line 43: I would change “sequence” to “succession” here. The word sequence has commonly genetic connotations, as in Seq. Stratigraphy is a misuse of the word.

Line 47: Change “Middle Eocene” to “middle Eocene”. See line 10.

Figure 2: The authors must revise the table and write the initial letter of any unofficial stratigraphic time subdivisions in lowercase (see my comment in line 10). They can check what is official and unofficial in the updated stratigraphic chart on the IUGS website: https://stratigraphy.org/chart/

Change “Approximate faults” to “Inferred faults” in the legend of symbols of Figure 2.

Line 53-54: Change “sequence” to “succession” twice in the sentence. See my previous comment on this issue. The same thing happens in Lines 58 and 64. Please, correct it.

Line 71: “Goderdzi Formatin” is misspelt. Please correct it.

Line 98: Change “crystal inity” to “crystallinity”.

Line 122: I would say “isotropy” rather than “isotropic” here.

Figure 6: The fossil log is not clearly seen in the figure. Please highlight its contour with a dotted-dashed line, or add a clearer figure so it is visible.

Line 189: “there is no “average composition.”” I think this sentence is unnecessary.

Line 192: What is “black carbon”? Coal, Anthracite, Lignite, Bituminous coal? Be clearer; saying “black carbon” here is incorrect.

Lines 196-197: “The fires associated with volcanic eruptions of in Hawaii, USA are a modern analog.” The authors should be more specific about what eruptions they are referring to and provide a reference. Change “analog” to “analogue”. Delete “of” before “in Hawaii”.

Figure 10: The authors should add arrows in Figures 10 A and 10 B to indicate fused cell walls as they mention in the Figure caption.

Line 218: Change “characteristic” to “mineral component”.

Line 266: “7. Examples” should be changed to a more specific title.

Line 267: Add “The” at the beginning of the sentence.

Line 268: “CT. A.” ?

Line 282: Delete “the” before “opal-CT”.

Line 290: Change “arrow” to “arrows”.

Lines 300-301: “Mineralzed” is misspelt.

Line 301: Delete “a” before “sparse”.

Line 311: “opal-(C)”, this is misspelt. Correct this sentence; it does not sound right.

Line 316: Add “an” before “arrow”.

Line 317: Change “the” to “a” before “density”.

Line 320: What are “rot pockets”? Do you mean “rotten pockets” in the wood? If so, correct, and if not, explain or delete. See the same issue in Line 336 and check it elsewhere in the text.

Line 354: Add “a” before “particularly”.

Line 355: Delete “havebeenreplaced” and add “been replaced”.

Line 356: Add a space in “lumencontain”: “lumen contain”.

Line 376: Delete “to” before “veins”. Rephrase the sentence in lines 375-377 so that it sounds idiomatically correct.

Lines 385-389: I do not understand. The authors say that the crystallisation of pyrite is a later stage, and then two lines below, they say exactly the opposite. Please rephrase and be clear.

Figure 25: Add arrows to pinpoint where the Zeolites are in the images and what other minerals we are seeing. Add also a brief explanation in the caption.

Line 414: Add “the” before “Goderedzi”.

Line 449: Misspelling. Change “he” to “the”.

Author Response

Thanks for your careful review of our manuscript, and your constructive suggestions. My replies are shown below.

However, my main concern about the manuscript is that it reads more like a guide or report on identifying different types of fossil woods than a research paper for a magazine, and this is because it lacks a proper discussion section. The discussion section is barely 15 lines and lacks comparisons or interpretations. Therefore, the authors need to compare their results with other coeval or non-coeval studies of fossil woods and with previous works on the floras of the Goderedzi Formation.

Following my previous suggestion, the article also needs more references, particularly when writing the new discussion section.

Additionally, the MS is missing a conclusions section, which should be written once the new discussion section is completed.

Reply:  Thanks for the suggestion. We have added  Discussion and Conclusion sections, and added references to other studies.

Finally, the English is well written and idiomatic, but I have spotted many mistakes, such as misspelt words and missing letters within words. I have listed most of them below in “Minor issues”, but I truly recommend that the authors check the text thoroughly because there can be more mistakes.

Reply: Thanks for your careful proofreading. We have made all of the suggested edits, and we will make a thorough check prior to submitting the revised manuscript. Also, my experience has always been that MDPI editors are flawless in their pursuit of perfection for final drafts.

In closing, I would like to again thank you for your dedication and expertise in writing your peer review. Our manuscript is better because of your contributions.

Reviewer 2 Report

Comments and Suggestions for Authors

This is a very useful, well illustrated, and informative account of silica permineralzation of wood from Georgia. I should be published with minor additions to set it within a context of other literature and theories on the topic.

1. Preservation of Goderzi fossil wood, both standing and prone in lahars (l.167) is comparable with Eocene wood from the Clarno Formation in Hancock Canyon, Oregon, and from the Yellowstone fossil forests of Wyoming. Studies of these other examples may be worth adding for comparison and are easily found on Google Scholar.
2. Reference to older silica-permineralized wood may be relevant here (l.264), as comparable studies have been done of Petrified Forest National Monument in Arizona.
3. The cubes of pyrite are probably hydrothermal rather than biogenic, and some duicusion of the redox or biological significance of the mineral should be added (l.389).
4. Zeolites are also interesting and their conditions of formation should be discussed: high temperature hydrothermal or low temperature weathering (l.403)?

l.13 found in “habitats”? odd word for here: would not be missed if deleted

l.42 the usual spelling is volcaniclastic

l.356 separate cell and lumen

Fig. 3 Please blacken the normal polarity intervals, to follow usual presentation. Also why is Goderzi Formation show extending up into Pliocene when all dates are Miocene. If there is Pliocene magnetostratigraphy in the Goderzi Formation that should be discussed and cited. It would be good to put stratigraphic interval of collected wood on this graphic.

Author Response

Thanks for your constructive comments. We greatly appreciate your efforts to improve this manuscript, and we are happy to accommodate your suggestions. Specific replies are shown below.

1. Preservation of Goderzi fossil wood, both standing and prone in lahars (l.167) is comparable with Eocene wood from the Clarno Formation in Hancock Canyon, Oregon, and from the Yellowstone fossil forests of Wyoming. Studies of these other examples may be worth adding for comparison and are easily found on Google Scholar.

Reply: Thanks, we have added mention of the Clarno and Yellowstone fossils forests, and cited references.

2. Reference to older silica-permineralized wood may be relevant here (l.264), as comparable studies have been done of Petrified Forest National Monument in Arizona.

Reply: I am reluctant to make references to other silicified wood localities because there are a multitude of occurrences, many with geologic settings that are very different from Goderdzi Formation. Also, Mesozoic and older petrified wood localities (e.g., The Arizona Petrified Forest and Chemnitz, Germany) are likely to have been subject to more extensive diagenetic alterations compared to Neogene occurrences.

3. The cubes of pyrite are probably hydrothermal rather than biogenic, and some duicusion of the redox or biological significance of the mineral should be added (l.389).

Reply: Thanks, we have added a clearer description for the pyrite, which indeed has a probable hydrothermal origin.

4. Zeolites are also interesting and their conditions of formation should be discussed: high temperature hydrothermal or low temperature weathering (l.403)?

Reply: Thanks, the section on zeolites has been expanded

Fig. 3 Please blacken the normal polarity intervals, to follow usual presentation. Also why is Goderzi Formation show extending up into Pliocene when all dates are Miocene. If there is Pliocene magnetostratigraphy in the Goderzi Formation that should be discussed and cited. It would be good to put stratigraphic interval of collected wood on this graphic.

Reply: Figure 3 has been modified, using black normal  polarity format. The Goderdzi Formation shows Miocene radiometric ages, in addition to the magnetostratigraphy. However, there is undated upper strata, suggesting that the formation may continue into the lower Pliocene. Geographic locations (e.g., GPS values)  are known for individual collecting sites, but stratigraphic positions are less certain. For that reason, we have not marked stratigraphic range on Figure 3.

Thanks for your expert help.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have made a significant improvement to their MS by adding a conclusion section and addressing most of the minor comments I suggested in my previous revision. However, they did not make any changes in the Discussion section, which is too short and incomplete (actually the conclusions are longer than the Discussion). I recommend that they compare their results with other fossils woods exemples elsewhere, preferably from the Cenozoic (as there are many examples in the literature). That way, they will also avoid the problem of shelf citations, adding new references to other studies and enhancing the scope of their study.

 

Author Response

Thanks for taking a second look at our manuscript. We have followed your advice to greatly expand the discussion section to include a comparison with other localities, supplemented by many additional references.