Coherence of Bangui Magnetic Anomaly with Topographic and Gravity Contrasts across Central African Republic

No

Reviewer’s Comments

Author’s actions

1

Extensive editing of English language and style required – Can be improved.

The attached PDF file with reviewer’s comments is used for updates. All the corrections are traced and corrected in the main text. The replies are added: see below starting from the row "Comments from the attached PDF file".The manuscript is proofread throughout by the authors and additionally by the colleague, a native speaker from the Great Britain. All the occasional typesetting misprints and minor grammar mistakes are now corrected where required (spelling, punctuation, syntax, simple misprints).

2

Is the research design appropriate? – Can be improved.

The research design is updated with added new paragraphs with detailed description of the advantages of the GMT and approaches to the data analysis by such modules as ‘grdfft’ and '’grdhisteq' modules used for plotting the histogram equalization and coherency. Scripts are moved to the Appendix with remained links to the codes in the Methodology section. In this way, the section is 'cleaned up' from the codes but the description of the major steps is maintained.

3

Are the methods adequately described? – Can be improved.

The Materials and Methods section is updated with many new insertions made in the text. The structure of both these sections is updated and partially modified. Also, added references to all the Equations to reference them correctly in the Materials and Methods section.

4

Are the results clearly presented? – Can be improved.

The Results section is updated. More explanations of the findings and comments on the presented maps are added in the Results section. Figure 10 is updated with added explanations in the figure caption. Added more comments on the correlation between the geophysical and topographic variables and discussed the distribution of the magnetic field with regard to the gravity variation based on the analysis of maps.

5

Comments and Suggestions for Authors

Dear Authors,

Summary: I read the manuscript carefully, which concerns “Coherence of Bangui magnetic anomaly with topographic and gravity contrasts across Central African Republic”

 In order to identify the geological structure of the Earth's crust, the authors investigated interactions between geophysical processes and geodynamics of the lithosphere. The Bangui magnetic anomaly, a significant characteristic of the Central African Republic's (CAR) lithospheric structure originating from the intricate tectonic development, is studied using the following methodology. The authors outline a scripting cartographic method based on Generic Map Ping Tools (GMT) that takes advantage of structural regularities in the geophysical, geologic, and topographic datasets on CAR and leverages them as input data throughout the matching process. This method should be adaptable enough to handle multi-source datasets of different formats and origins and to quickly plot many maps in the same projection and spatial extent for comparison.

The manuscript has some problems regarding writing style, Materials, results, and discussion. In particular, to be a valuable contribution to the geophysical literature, the paper still needs major revisions; the article needs some language polishing, editing, and consistency.

All my comments and more details included in the attached files

Best regards

Many thanks for the review of the manuscript. The paper is revised according to the comments from all the three reviewers. The updates are marked up yellow in the main text for track changes. The Results section is updated with added more comments on the correlation between the geological structure of CAR and variations in the geophysical and topographic data. Figure 10 is replotted and updated with requested changes. The Methodology section is partially restructured with scripts moved to the Appendices and added explanation of the workflow instead. The Discussion section is updated with more comments added regarding the meaning, importance, and relevance of the use of advanced scripting cartographic tools of GMT for geophysical mapping. Moreover, the reasons for the matching in geological data with gravity and Bangui magnetic fields in CAR are discussed. In particular, we added a paragraph on the relevance of structures and hypsometry associated with the Bangui magnetic anomaly and the extent of the major geological units and tectonic structures such as Central African Orogenic Belt which illustrates the links between the geological and topographic data. All other comments are considered and replied point-by-point in this document below and as replies to other reviewers. The proofreading is performed with language polishing and correcting where required.

6. Comments from the attached PDF file

7

Line 2: “The noun phrase geologic structure seems to be missing a determiner before it. Consider adding an article.”

Corrected, now: "lithosphere play a crucial role in the geologic structure of the Earth's crust."

8

L.3: “It seems that there is an article usage problem here.”

Corrected: “lithospheric structure of the Central African Republic (CAR) resulted from the complex tectonic evolution”.

9

L.11: “It appears that the singular verb was does not agree with the plural compound subject topography, gravity and geoid data. Consider changing the verb to the plural form.”

Corrected: "The consistency and equalization of topography, gravity and geoid data were based using GMT modules".

10

L.30: “This sentence is hard to read, please, check”

Rephrased as follows: “The anomaly received the name after the capital of the country Bangui which is located at 4°20 N on the right bank of the Oubangui River [2,3]. The Oubangui River is a major tributary of the Congo River playing important role of the economy of CAR as an important transport artery [4].”

11

L.52: “The noun phrase opening seems to be missing a determiner before it. Consider adding an article.”

Corrected, now: "the magmatism is affected by the continental rifting and related activity of a mantle plume during the opening of the Atlantic in Mesozoic".

12

L.60: “Your sentence may be unclear or hard to follow. Consider rephrasing”

Rephrased as follows: “As a result, the crude oil deposits are formed in the structured reservoirs of the fault blocks in the rift basins of CAR [18].”

13

L.70: “It appears that you are missing a comma after the introductory phrase In this paper. Consider adding a comma.”

Corrected: “In this paper, we present a scripting cartographic approach based on the Generic Mapping Tools (GMT) that exploits <...>”

14

L.75: “The adverbial separately appears to be misplaced in this sentence. Determine the appropriate placement for the adverb.”

Rephrased as follows: “Afterwards, we detect and separately analyse the repeated structures in the topographic grids.”

15

L.82: “Correct seems to be the wrong part of speech for this context. replace with "correctly"”

Corrected, now: “We propose using GMT modules that correctly match and visualise the repeated structures placed on the images and identified for the maps of gravity, geoid, topography, geology and magnetic anomalies over CAR.”

16

L.139: “Please, check the spelling”

Corrected: “The southern region of CAR lithology continues the northern border of the Congo Craton and is presented by the Lower Cretaceous (Kl) and Precambrian (pCm) successions”.

17

L.152-153: “This sentence appears to be written in the passive voice. Consider writing in the active voice. check the verb too”

Corrected, now rephrased as follows: “The alluvium and colluvium from the Pleistocene (Qp) valleys with modern sediments of Holocene (Qe) form a basin of the modern Aouk river and its tributaries which create a natural border between CAR and Chad”.

18

L.166: “It appears that you typed the twice in a row. Consider deleting one of them”

Corrected, now: “dominated savannah [49] and dense ombrophile forest in the southern regions of the country [50]”.

19

L. 169: “It seems that preposition use may be incorrect here.”

Rephrased as follows: “The distribution of crops and related agriculture activities correspond to the different types of soil within various regions of the country which is in turn largely controlled by the regional setting of the geologic basement”.

20

L.175: “I suggest, you can add the scripts as supplementary materials and focus more on the benefits of processing and interpretation methods”

Corrected: all the scripts are moved to the Appendix in the end of the paper. In this way, they do not interrupt the flow of the text in Methodology but remain present for reference.

21

L.308: “The verb was does not seem to agree with the subject. Consider changing the verb form.”

Rephrased as follows: “The remaining cartographic elements were added using the sequence of modules GMT such as 'psbasemap', 'pscoast' <...>.”

22

L.345: “It seems that the verb was does not agree with the subject. Consider changing the verb form.”

The noun is corrected and now the sentence is rephrased as follows: “The analysis of the coherency used for plotting the graph was performed using the GMT”.

23

L.436: “The singular verb corresponds does not appear to agree with the plural subject grids.”

The phrase is corrected: “The analysis of the topographic grid reveals a local depression in the equalised raster grid which corresponds to the geoid and gravity data”.

24

L.450: “It seems that preposition use may be incorrect here.”

Rephrased and corrected as follows: “Since the Bangui magnetic anomaly continues within the Central African Orogenic Belt which is a subject of the cumulative effects of the multiple tectonic events <...>”

25

L.463: “There is a misspelling here, replace with "lithospheric"”

Corrected as follows: “the contrasts of the geoid are influenced by the distribution of the deep-mantle anomalies in the lithospheric heterogeneities”

26

L.488: “You have written the same word with and without a hyphen i, please, choose one writing style and fix all over the manuscript”

Corrected the spelling of northwest. Corrected in the sentence "major structural elements in the Bossangoa and Bossembele areas in the northwest <...> " Also checked throughout and corrected in the phrase: “also found in the Tamkoro-Bossangoa Massif in the northwest intruded into a strike-slip shear zone”

27

L.489: “Check the verb "include"”

Rephrased as follows: “reflect the tectonic evolution of the basement of the North Equatorial fold belt which includes the shear zones, lineations and fold axes”

28

L.516: “Did you applied any of the edge detection methods of satellite gravity and magnetic data?, please. if you don't, you can try and it will help to map the main structures and its main direction.”

Since edge detection methods require extra tools such as image segmentation and data extraction in remote sensing analysis, this part of task outsteps the defined research goals and intended methods. Future research as a continuation of this study may consider these methods of data processing.

29

L.536: “Check the misspelling”

Corrected the link to Figure 9: “(Figures 8 and 9 with an enlarged view)”.

30

L.580: “To show the validity of the used approach, you have to check the main structure trends from the gravity and magnetic methods and compare to the main structure trends from the geological map.”

The main structure trends were checked using the analysis of the gravity and magnetic maps as well as geoid data undulations which were compared to identify and describe the main structure trends with respect to the lithologic structure visualised on the geological maps in Figures 2 and 3. Further, the topographic data were analysed in the histogram equalization of the grids with detailed plot showed in Figure 4.

Yes

Can be improved

Must be improved

Not applicable

Does the introduction provide sufficient background and include all relevant references?

(x)

( )

( )

( )

Are all the cited references relevant to the research?

(x)

( )

( )

( )

Is the research design appropriate?

( )

(x)

( )

( )

Are the methods adequately described?

( )

(x)

( )

( )

Are the results clearly presented?

( )

(x)

( )

( )

Are the conclusions supported by the results?

(x)

( )

( )

( )

No

Reviewer’s Comments

Author’s actions

1

Does the introduction provide sufficient background and include all relevant references? – Can be improved.

The Introduction section is restructured, divided into the two subsections with updated references. The first subsection 1.1. Background present study goal and main hypothesis, the objectives and major approaches to solve issues of matching the topographic, geological and geophysical datasets, existing in similar literature. The 2^nd subsection 1.2. Study Area discusses regional features and presents geological characteristics of CAR as the target area.

2

Are all the cited references relevant to the research? – Must be improved.

Added several citations on datasets and software: the earlier reference for GMT. (Wessel & Smith, 1991) https://doi.org/10.1029/90EO00319; cited ETOPO1 dataset; deleted citations of software from figure captions and added instead to the Acknowledgements, as suggested below in comment 7.

3

Is the research design appropriate? –Must be improved.

The research designed is updated with partially restructured Methodology section: scripts are moved to the appendices and more description of the Methods and Data is added. Selected phrases and paragraphs related to Methodology are moved from the Discussion section which is also rewritten and restructured.

4

Are the results clearly presented? – Must be improved.

The Results are updated with all new inserted texts and paragraphs coloured in the text. Also, added the paragraph on the actuality and novelty of this undertaken study as follows: "This study presented previously unpublished analysis of the coherence between the geophysical and geomagnetic data over CAR implemented by the GMT scripts. Limited information on the Bangui magnetic anomaly and scarce data on its relationship with regional geologic setting, lithospheric structure and the gravity motivated this research and underlined the actuality of the presented results. With this regard, mapping the magnetic and gravity anomalies over CAR analysed in the context of its regional geologic and tectonic development contributes both to the theoretical investigation on geotectonic and geological setting in central Africa and to the practical increase of geospatial information aimed at mineral exploration in CAR. "

5

Are the conclusions supported by the results? – Must be improved.

The Conclusion section is updated and restructured. The last paragraph is added, others rephrased with many sentences updated and modified. All the new insertions are coloured yellow for track changes.

6

General considerations:

1- Although it is quite nice to have the complete processing chain available, the scripts themselves should not be a part of the main text. For the sake of transparency and completeness, they can be included in the supplementary material.

Also, the scripts should be formatted as stand-alone scripts. Instead of starting them with “exec bash”, a proper #! line should be used.

#!/bin/bash
#

SCRIPT WITHOUT exec bash

exit

Corrected: the scripts are now moved to the Appendix. The amendments in the scripts are done as suggested. Now the Methodology section is more readable and ‘cleaned our’ from the codes.

The structure of scripts is updated with #!/bin/bash.

7

2- It is not necessary to specify the software used on every caption. A single line at the end of the manuscript acknowledging the different softwares used and their corresponding references is enough. For example: “The GMT (Wessel & Smith, 1998) and QGIS (reference) software packages were used extensively in the preparation of this paper.”

Corrected as suggested: the mentions of the software are deleted from the figure captions and added to the Acknowledgements, as recommended: “The GMT [95] and QGIS [96] software packages were used extensively in the preparation of this paper.”

8

3 – cartography sources shouldn’t be the authors themselves.

All the maps are made by the authors. Corrected reference in all the figure captions as follows: “Map source: authors”. Dataset sources are also mentioned in all figure captions.

9

Specific issues with the manuscript (line number is followed by comment or suggestion)

1. L27 Zair → Zaire

2. L29 The anomaly received the name after the capital of the country located at 4°20 N on → The Bangui anomaly is named after the capital of the Central Africa Republic (CAR), located at LAT and LONG, on the right…

3. L35 What is an intensively magmatic rock?

4. L39 the comparisons of the magnetic contrasts, geologic setting and geophysical data in the Earth’s critical zones provide new… → the comparison between magnetic contrasts, geologic setting and geophysical data in the Earth’s critical zones provides new...

5. L41 It furthermore enables to perform a better interpretation the effects from the tectonic activity in the past on the geophysical processes in present [10] – This phrase is so confusing. Do you mean “It furthermore allows a better interpretation of the effects of past tectonic activity on the present geophysical processes”?

6. L51 related activity of a mantle plume – Which mantle plume? The opening of the South Atlantic Ocean during the Cretaceous is probably no directly related to what happened in the middle of a craton. Please revise this geological background.

7. L57 In the previous sentences you were describing a rifting process. Now you are talking about a subduction.

8. L70-89 Please describe only the steps taken, not the specific program or modules used.

9. L94 West Zaire Precambrian Belt

10. L95 The first one is the 250 km-long Bandas belt, composed…

11. L97 the 150 km-long Bogoin…

12. L97 deposites → deposits

13. L107 West Zaire Precambrian Belt (also through-out the entire text)

14. L158 north-eastern – Also, why are diamond deposits relevant to satellite-derived magnetic anomalies?

15. L160-L174 How is this relevant?

16. L180-185 Does this add anything new? Researchers routinely use these tools. GMT was created exactly for this reason and it is already on version 6.

17. L186-422 explain briefly what steps were taken. The complete scripts and detailed explanations should be sent to supplemental data.

18. L423-428 A rambling phrase that needs to be rewritten and re-checked. Consider splitting it up.

19. L431 The results demonstrated → the results show

20. L435-442 If this paper simply confirms previous results, where does it innovate?

21. L453 lower gravity anomalies do not always correspond to a thinner lithosphere

22. L462 How are deep mantle anomalies distributed in lithospheric heterogeneities?

23. L463 Subducted slabs?

24. L466 – the African cratons have been relatively stable since Rodinia. Tectonic plate movements are irrelevant for the studied area.

25. L474-480 You start by describing the sedimentary cover, only to conclude that the magnetic anomaly “distribution” is due to upper mantle sources. What is “distribution of the magnetic anomaly”? How can you infer about short wavelength anomalies from satellite-derived measurements, sensitive only to longer wavelengths?

26. L482 Surface topography is NOT related to deep mantle convection.

27. L531 On Figure 10, you show that there is coherence between major features in the gravimetric data and their derivatives. Isn’t this expected? – On figure 10, each panel should have a letter and a more detailed explanation in the caption.

28. L536 fig09 → Figure 9

29. L554-602 This whole section is praising GMT as if it was a new tool. It isn’t. It is 30 years old. And you should also cite the first paper related to GMT. (Wessel & Smith, 1991) https://doi.org/10.1029/90EO00319 In any case, the discussion is not really a discussion. If you want to keep it, change its name to Methods, for example.

30. L604-642 The conclusions are also very confusing. Is this manuscript about cartography? About geophysics? About the differences between QGIS and GMT?

Corrected in all these cases:

1. L27 corrected here and in several more placed – checked throughout the manuscript)

2. L29 Rephrased as suggested.

3. L35 Corrected: 'intensely' referred to the 'highly' metamorphosed rocks. Rephrased as follows: “highly metamorphosed Precambrian rocks and has a Precambrian basement with large masses of the magmatic rocks”.

4. L39 the comparisons of the magnetic contrasts, geologic setting and geophysical data in the Earth’s critical zones provide new… → the comparison between magnetic contrasts, geologic setting and geophysical data in the Earth’s critical zones provides new… - Rephrased as suggested.

5. L41 It furthermore enables to perform a better interpretation the effects from the tectonic activity in the past on the geophysical processes in present [10] – This phrase is so confusing. Do you mean “It furthermore allows a better interpretation of the effects of past tectonic activity on the present geophysical processes”? – Yes, exactly, this phrase is replaced, misspelling is corrected.

6. L51 Rephrased as follows with provided citation: "The magmatism in Central Africa is a consequence of the continental rifting, opening of the Equatorial Atlantic and the Mesozoic-Cenozoic magmatic activity [14]."

7. L57 Rephrased as follows with provided citation: "The Central African Fold Belt is formed as a result of the extension of the Congo Craton and associated collisions of the related crustal blocks in Cameroon and CAR [15]."

8. L70-89 Corrected for the two last paragraphs in section 1. Introduction. Technical details (modules, software) are deleted.

9. L94 Corrected ‘Zaire’ everywhere.

10. L95 – Yes, that is correct: the Bandas belt is described in previous study. It is one of the two two Archaean greenstone belts. (DOI: 10.1016/0301-9268(81)90011-5)

11. L97 that is correct: the Bogoin is the 2^nd from the two Archaean greenstone belts (Bandas and Bogoin). DOI: 10.1139/e85-072

12. L97 deposites → deposits corrected.

13. L107 West Zaire Precambrian Belt (also through-out the entire text) – Yes, checked and corrected throughout.

14. L158 Corrected to the “north-eastern”. It is a continued description of the geological setting in the study area which is rich in mineral resources.

15. L160-L174 The description of the mineral resources is shortened. It was an example of the alluvial deposits.

16. L180-185 Rephrased and shortened in the following phrase: “The programming approaches used for mapping present an advanced alternative to the traditional cartography [61–63]. <...>.”

17. L186-422 Corrected: all the scripts are moved to Appendix in the end of the paper. The Methodology is now shortened with a brief explanation of the research steps.

18. L423-428 Rephrased as follows: In this section, we present the results of this study which we briefly summarize as follows: 1) maps of the geologic structure and units in the region of CAR which enabled to analyse the correlation between the geological and geophysical setting; 2) maps of the gravity and geoid variations for estimation of the contrasts; 3) coherence between the vertical gravity anomalies and gradient; 4) visualisation of the extent of the magnetic anomalies for analysis of the correspondence with the lithosphere structure of CAR based on the datasets on geologic provinces and units.

19. L431 The results demonstrated → the results show – Corrected.

20. L435-442 Previous results are only used for reference and comparison with earlier studies (as often recommended in the journals). This study reports our own maps and discusses the results. Rephrased as follows in the phrase: “This proves the distribution of the ring-shaped formation around the region of magnetic anomaly that has an outer ring diameter <...>.”

21. L453 the sentence is extended and rephrased as follows: "The reasons of the gravity anomalies are caused by the rugged surface, nonlinear and complex composition of the Earth's inner structure. Other factors include thinner lithospheric thickness and Moho depths associated with the isostatic surface topography which affects its gravitational field. Furthermore, the values of gravity are affected by the rotation of the Earth which results that values near the equator are higher compared to those on poles."

22. L462 Rephrased as follows: "the contrasts of the geoid are influenced by the lithospheric heterogeneities <...>".

23. L463 Corrected and rephrased: “Further, the contrasts of the geoid are influenced by the lithospheric heterogeneities [81] which pose constraints in the density material that are reflected in the surface variations of geoid”

24. L466 – Corrected and rephrased as follows: "lower lithospheric depth and crustal density which correspond to the heterogeneities in the mantle density"

25. L474-480 Rephrased as follows: "which implies that these heterogeneities are related to the Earth lithosphere and geologic features increasing or depreciating local magnetic field depending on the subsurface structure and composition of the Earth's crust. Furthermore, the variations in vertical gravity intensity observed in Figure 7 point at the difference in lithospheric mass anomalies caused by deeper density contrasts"

26. L482 Corrected as follows: “the surface topography is related to the geologic-tectonic processes”

27. L531 Figure 10 is corrected: added small captions (letters) on each panel and added more detailed explanation in the common figure caption of the whole figure.

28. L536 Corrected for fig09 → Figure 9

29. L554-602 The Discussion section is updated. The specifics of the GMT with essential description of the software is moved to the Methodology section where it is relevant. The discussion includes more comments on the magnetic anomaly in CAR, its origin and relations to the geological structure revealed from the presented maps. The citation is added with the first paper related to GMT. (Wessel & Smith, 1991), as suggested. As suggested, this section is restructured and moved to the Methods and a subsection related to the description of the GMT.

30. L604-642 The Conclusion section is improved and restructured with many new paragraphs and selected sentences inserted; some phrases rewritten and partially reworded and structure of the section modified for a better clearance and logic of the text flow with more accent placed on the applied cartographic methods used for mapping the geophysical data and magnetic anomaly in CAR, as well as its correspondence to the geological setting.

10

Final considerations:

A scientific paper should answer a very specific question or, at least, give new insights on a subject. The whole text should lead the reader from the question to the answer. This manuscript doesn’t do this. What problem are you addressing? What was your hypothesis? What did you do to test it? This is really important: what did you do to invalidate your hypothesis? We don’t gain knowledge by getting every piece of data that fits our model. We need to find ways to break our model. What are your answers? How do this paper add to current knowledge of the studied region?

These questions are introduced in the novel subsection 1.1. Background where the study goals, questions, the addressed problem and the hypothesis are discussed. Also, this section summarizes how this study adds to current knowledge of CAR and African studies in general. Then, section 1.2. Study Area continues the Introduction where the description of the CAR is presented. The paragraph regarding the actuality and the novelty of this study is included in the Conclusion section: “This study presented previously unpublished analysis of the coherence between the geophysical and geomagnetic data over CAR implemented by the GMT scripts. Limited information on the Bangui magnetic anomaly and scarce data on its relationship with regional geologic setting, lithospheric structure and the gravity motivated this research and underlined the actuality of the presented results. With this regard, mapping the magnetic and gravity anomalies over CAR <...>”.

Yes

Can be improved

Must be improved

Not applicable

Does the introduction provide sufficient background and include all relevant references?

( )

(x)

( )

( )

Are all the cited references relevant to the research?

( )

( )

(x)

( )

Is the research design appropriate?

( )

( )

(x)

( )

Are the methods adequately described?

(x)

( )

( )

( )

Are the results clearly presented?

( )

( )

(x)

( )

Are the conclusions supported by the results?

( )

( )

(x)

( )

1

Is the research design appropriate? – Can be improved.

The manuscript is updated and proofread carefully with all changes coloured yellow. The research design is updated with new insertions coloured yellow for track changes in the Materials and Methods section. The GMT scripts are inserted into the Appendix while the description of the techniques remained. Also, added some more comments to all the subsections (3.1. Histogram equalization; 3.2. Geoid; 3.3. IGPP Earth Free-Air Anomaly; 3.4. Coherency of geophysical grids). The technical explanations on the selected GMT functionality and its advantages for geophysical mapping is added. All changes are highlighted.

2

Are the results clearly presented? – Can be improved.

The results section is improved and updated. Figure 10 is replotted with added labels for each graph on the facetted plot. The Results section is improved with added mote discussions on the geophysical and geologic maps obtained in this study. Some phrases are reworded and updated. The test is proofread. Selected paragraphs are extended with added more details, added more phrases and some new sentences.

3

Are the conclusions supported by the results? – Can be improved.

The Conclusions section is updated with inserted last new paragraph and modified phrases and selected words. Some previous parts of the text are restructured, partially modified and shortened; some statements are extended and elaborated more; some sentence are moved to Introduction where they fit better. In this way, the Conclusion section is restructured and improved.

4

Comments and Suggestions for Authors

Article dealing with a scripting cartographic approach based on Generic Mapping Tools (GMT) that exploits the structural regularities in the geophysical, geologic and topographic datasets on CAR, namely gravity, topography and magnetic fields and uses them as input information during the matching procedure.

Very interesting results.

Some suggestions are given in the pdf. The section conclusions can be improved.

Many thanks for the review and support of our paper. The improvements are done with all the updated sections (also considering two other reviews). The Conclusions section is updated with some paragraphs restructured, selected sentences rewritten and reformulated. The summary is articulated in a more concise way. The addressed research problem is explained and highlighted more with added discussion on the tested hypothesis. The advantages of the use of scripts for applied geophysical mapping are discussed.  The pdf file is considered for updates and used for changes.

5

Moderate English changes required

The manuscript is proofread throughout by the British native speaker colleague, a citizen of the U.K. We have corrected all occasional typesetting misprints and minor grammar mistakes (spelling, punctuation) where necessary. Grammar errors are corrected and misprints are checked everywhere in the text.

Yes

Can be improved

Must be improved

Not applicable

Does the introduction provide sufficient background and include all relevant references?

(x)

( )

( )

( )

Are all the cited references relevant to the research?

(x)

( )

( )

( )

Is the research design appropriate?

( )

(x)

( )

( )

Are the methods adequately described?

(x)

( )

( )

( )

Are the results clearly presented?

( )

(x)

( )

( )

Are the conclusions supported by the results?

( )

(x)

( )

( )

No

Reviewer’s Comments

Author’s actions

1

I have just finished reviewing the manuscript entitled “Coherence of Bangui magnetic anomaly with topographic and gravity contrasts across Central African Republic”. This paper presents an analysis of the magnetic anomaly field and the coherence of geophysical data derived from a collection of maps. Raster grids on free-air altimetric gravity, magnetic EMAG2 maps, a geoid EGM2008 model, and topographic SRTM/ETOPO1 relief are some of the data sources used in this study. The analysis of crustal thicknesses and the average density of the Earth in the CAR, as well as the magnitude of the magnetic fields with notable deviations caused by the magnetic flux density in the Bangui area related to the distribution of mineral resources in the CAR, are all improved by the integration of data from multiple sources.

I congratulate the authors on their excellent approach. The writing style is excellent.

Additionally, the authors accurately corrected the reviewers' comments, which improved the quality of the paper.

Best regards

Thank you very much for the re-review and providing final comments regarding the manuscript. We highly appreciate your support and endorsement of the paper.

With kind regards, - Authors.

Yes

Can be improved

Must be improved

Not applicable

Does the introduction provide sufficient background and include all relevant references?

(x)

( )

( )

( )

Are all the cited references relevant to the research?

(x)

( )

( )

( )

Is the research design appropriate?

(x)

( )

( )

( )

Are the methods adequately described?

(x)

( )

( )

( )

Are the results clearly presented?

(x)

( )

( )

( )

Are the conclusions supported by the results?

(x)

( )

( )

( )

No

Reviewer’s Comments

Author’s actions

1

Does the introduction provide sufficient background and include all relevant references? – Can be improved.

The Introduction is now partially rewritten and updated again, according to your new comments.

2

Are all the cited references relevant to the research? – Can be improved.

Some more references are added in the list of References.

3

Is the research design appropriate? – Must be improved.

The modifications and updates are introduced in the paper throughout according to your recent comments.

4

Are the results clearly presented? – Must be improved.

Updates are made in the Results section and also in the Discussion and Conclusion sections where the new results are commented and discussed in more details.

5

Are the conclusions supported by the results? – Must be improved.

Added new paragraphs, e.g., “To the best of our knowledge, there is no similar study in the existing literature that integrates the data on geophysical and geologic setting on CAR. As discussed in previous sections, the existing scarce studies on the geophysical setting of CAR mostly employed the GIS for mapping the geology and magnetic data. Therefore, current study presented a previously unpublished data, maps and results of spatial analysis based on the integrated geophysical data over the magnetic anomaly in Bangui area, CAR. To understand the effects of gravity anomalies and geological fields on the distribution of the magnetic magnetic anomaly in Bangui area, we present a series of the previously unpublished maps supported by spatial analysis. The association between the decrease in magnetic values based on the EMAG2 and WDMAM with gravity, geologic and topographic data are revealed and discussed”

6

The authors have done a good job on the introduction, with an adequate geological setting description.

Many thanks for the re-review and endorsement of our manuscript. We highly appreciate your support.

7

Further along, the methods section hasn't changed much. The scripts are now in the appendix, but the text is still very poor.

The text in Methods is updated with added corrections and improvements.

8

As for the conclusions, I finished reading the manuscript and could not find the scientific problem addressed or even an answer. What is the purpose of this paper?

The scientific problem is discussed more precisely as follows: “In this paper, we address the problem of the unified cartographic matching framework that supports a large family of data formats technically implemented in the Generic Mapping Tools (GMT) and QGIS. Our goal is to present a scripting cartographic approach that exploits the structural regularities in the geophysical, geologic and topographic datasets on the Central African Republic (CAR) and uses them as input information during matching procedure. With this regard, this study aims at presenting a cartographic interpretation of the Bangui Magnetic Anomaly and analysis of its consistence using the available data on geophysical and geological setting of the CAR. Technically, we optimised the operational workflow of the cartographic work due to the use of scripts.”.

9

L8 – setting in CAR region

setting in the CAR region

Corrected to “setting in the CAR region”

10

L8 - bypartition

by partition

Corrected: “by partition”

11

L10 - comparedwith

compared with

Corrected: “compared with”

12

L20 - analyses

analysis

Corrected: “analysis”

13

L34 - Earth point? The rest of the phrase is also very confusing.

It was a misprint “Each point” → the sentence is rephrased as follows: “A particular geophysical or geologic feature is associated with a coordinate position in a cartographic domain identifying its location, and variables representing its appearance either by the points for discrete objects or by the fields for continuum processes.”

14

L46 – shape files - .shp in the ArcGIS

ArcGIS shape files

Corrected: “ArcGIS shape files”

15

L63/64 - that utilises the codes written by the GMT syntax for

that uses Bash scripts and GMT commands for

Corrected: “that uses Bash scripts and GMT commands for”

16

L69/L77/L82/please check the rest of the text - of the CAR

Corrected in phrases: "the relief in various regions of the CAR"; "magnetic anomalies over the CAR"; "geophysical anomalies over the CAR"; "geological data over the CAR"; "The tectonic structure of the CAR"; "mineral exploration in the CAR"; "southern region of the CAR", etc. Coloured yellow for track changes.

17

L70 - were incorporated independently and processed 

were independently incorporated and processed 

Corrected: “were independently incorporated and processed”

18

L75 – What is data that is correctly matched?

Rephrased as follows: “the data covering the study area of CAR and visualised them for analysis”

19

L77 – for such an algorithm is for image pairwise comparison in map pairs where

for such an algorithm is to do pairwise comparison of maps where

Corrected: "The main application for such an algorithm is to do pairwise comparison of maps where"

20

L83 - We demonstrate that our

Corrected: “We demonstrate that our”

21

L85 - that a correlation exist

that a correlation exists

Corrected: “that a correlation exists”

22

L90 – We showed

We show

Corrected: “We show”

23

L99 - playing important role of the 

and plays an important role in the

Corrected: “and plays an important role in the”

24

L101 - This phrase needs rewritting. You should not start with “Revealed”

Rewritten as follows: “The anomaly has a crustal origin and is strongly related to the tectonic evolution and Precambrian history of the Saharan metacraton and Congo Craton, as also revealed by the satellite magnetometer data and reported in previous studies”

25

L105 - of the magmatic

of magmatic

Corrected: “of magmatic”

26

L106 - related to lithosphere bending.

related to the bending of the lithosphere.

Corrected: “related to the bending of the lithosphere”

27

L135 - In turn, data on magnetisation reveal the properties 

In turn, magnetisation data reveals the properties 

Corrected: “In turn, magnetisation data reveals the properties”

28

L157 - They indicated

They indicate

Corrected: “They indicate”

29

L161 - They are composed by the gneisses

They are composed by gneisses

Corrected: “They are composed by gneisses”

30

L169 - the remained

the remaining

Corrected: “the remaining”

31

L171 - consisted of the

consisted of

Corrected: “consisted of”

32

L205 - form a basin

form the basin

Corrected: “form the basin”

33

L231 - presented below

presented in appendix A

Corrected: “presented in appendix A”

34

L245 - Why the insistence that GMT isn’t conventional software? It is a fundamental tool for geoscientists.

Rewritten as follows: “Such technical approach presents a significant benefit of GMT over the traditional GIS software”

35

L271 - describing gdalinfo and makecpt is completely irrelevant. It is the same as to say that you checked the properties of a shape file. If you feel this is necessary, please do it a comment on the script

The detailed description is deleted and the surrounding text is partially reformulated as follows: “Afterwards, the extent of the data range was evaluated for the image by the 'gdalinfo' and the visualization was adjusted by 'makecpt'”.

36

L278 - the same for pscoast and pstext. Would you say you clicked on the add text icon on ArcGIS?

Ok, agree: this sentence is deleted.

37

L284-293 - Same considerations

The subsection 3.3. IGPP Earth Free-Air Anomaly is corrected with these details deleted.

38

L313 - thegravity

the gravity

Corrected: “the gravity”

39

L371 - I would say that surface topography, at the scale of this study, is more affected by erosion than other causes

Ok, many thanks for the help in formulating it. Rephrased and reformulated as suggested: “Surface topography is strongly related to the geologic-tectonic processes, and at the scale of this study, it is more affected by erosion than other causes. Additionally, it is also associated with seismic anomalies in the dense mantle”.

40

L384 - It also showed

It also shows

Corrected: “It also shows”

41

L403 – Please create a figure where you overlay geology and potential field data.

The geologic maps are presented in Figures 2 and 3. Since we do not have other data available, this would be beyond the scope of the manuscript. Further mapping showing field exploration and mineral resources can be a continuation of this study in the future similar works on the CAR.

42

L483-522 - For me, it is still unclear what this paper adds to current knowledge on the region. It seems that the main purpose is to simply compare potential field datasets. There is no underlying question to answer. Why is this study done here? What problem does it try to solve? Saying that GMT is great for geosciences is the same as saying that mountains are high and valleys are low. This is not a selling point for a scientific paper.

The paper demonstrates the coherency between the geophysical data, hypsometry and the Bangui magnetic anomaly fields. For example, we demonstrated that the correlation is visible between the lowest magnetic data in the region from 3°N to 7°N (a white square in Figure 10) and the elongated negative depression in the free-air gravity at 4°N over the basement of West Zaire Precambrian Belt which has a south-west-north-east extension over the territory of CAR. Such correspondence is related to the variations in crustal thicknesses in this region of CAR caused by the tectonic processes. Also, the contribution is described better in the Conclusion section as follows: "we examined the relationship between these datasets over CAR by the advanced cartographic approach. To this end, we presented a GMT console-based method of the cartographic data processing, which was integrated into the geological-geophysical analysis of the Bangui magnetic anomaly and surrounding regions. We tested our proposed techniques in the context of the regional setting of CAR where extreme magnetic anomaly is presented in the Bangui area. Overall, seven datasets are processed, visualised, evaluated and analysed including the geoid EGM2008, IGPP, GEBCO, ETOPO1, EMAG2, WDMAM and the geologic datasets obtained from the USGS."

43

A conclusion should answer a question. So far, I don’t even see the question in this manuscript.

The Introduction is restructured with added new subsection

The hypothesis is introduced and relevant research questions are defined as follows: “The effects of the geophysical and geological factors on each other have not been well observed in a more structural way in the existing literature. As a response to this need, a conceptual framework for this study was developed based on a set of hypotheses derived from the literature review and considering the local context of CAR. We proposed a hypothesis as follows: the magnetic anomaly Bangui is strongly associated with the regional geophysical and geologic setting in CAR. As such, we focus on the following questions in this study: (Q1): Is magnetic anomaly Bangui positively associated with gravity values and free-air anomaly? (Q2): Is magnetic anomaly Bangui associated with the distribution of the geologic setting in the region ?”

In the Conclusion section, the hypothesis is confirmed and research question are answered as follows: “Based on the conceptual GMT-based cartographic framework developed for the study we confirm the hypothesis derived from the obtained new maps on CAR. Considering the local geological and geophysical context of CAR, we answer to the defined research questions as follows: (Q1): The magnetic anomaly Bangui is positively associated with gravity values and free-air anomaly. (Q2): The magnetic anomaly Bangui is associated with the distribution of the geologic setting in the region of CAR.”

Also, an extended paragraph is added in the

44

Figure 1: omit map source: authors. It is only required to cite to data sources or, if the figure was adapted from other works, the other authors. If nothing is said, it is assumed that the figure is made by this paper’s authors. You do need to cite the source for the cities positions, as GEBCO is only for altimetry.

Corrected in Figure 1 and all other figures (1 to 10). Deleted “Map source: authors.” from all figure captions in Figures 1 to 10. Also, the reference for GEBCO is deleted in Figure 1.

45

Figure 2: If the data source is USGS, why is there a logo for OSGeo on the image? Where is the reference?

The OSGeo is used as a background in this figure (it shows a topographic map with cities). Added a reference for OSGeo in caption of Figure 2.

Yes

Can be improved

Must be improved

Not applicable

Does the introduction provide sufficient background and include all relevant references?

( )

(x)

( )

( )

Are all the cited references relevant to the research?

( )

(x)

( )

( )

Is the research design appropriate?

( )

( )

(x)

( )

Are the methods adequately described?

(x)

( )

( )

( )

Are the results clearly presented?

( )

( )

(x)

( )

Are the conclusions supported by the results?

( )

( )

(x)

( )