How Did the Late Paleozoic to Early Mesozoic Tectonism Constrain the Carboniferous Stratigraphic Evolution in the Eastern Qaidam Basin, NW China?

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper discusses tectonic events during the late Carboniferous to early Permian, late Permian to early Triassic, and middle Triassic to late Triassic, using low-temperature thermochronology and seismic data. While the paper is well-written, it has some shortcomings, particularly in the thermochronology section. It appears that the authors focused more on seismic data and gave less importance to thermochronology. Here are some examples:

 

 

 

1. The authors used zeta-calibration, but they did not provide information about its values or the dosimeter used. Additionally, while they used age populations for geological interpretation, they did not present individual data information such as a grain-by-grain age table, despite the availability of RadialPlotter and age distribution.

 

2. According to Table 1 and Figure 5, the maximum number of grains analyzed was 26, and the minimum was 12. For this kind of interpretation, one would expect more grains (around 50) per sample. However, low-temperature thermochronology faces a considerable challenge when dealing with zircon. There can be various reasons why enough zircon ages were not obtained, such as metamictization, lost grains during the etching process, or lack of grains for such analyses. Despite the small amount of grains analyzed, the authors were able to make a good correlation with the already published geological evolution.

 

3. For ZHe, the authors did not provide information about the methodology (despite indicating the paper for that), but also individual ages (grain-by-grain) the amount of 4He, 238U, 235U, 232Th, size of the grains, raw ages, Ft factor, corrected age, or any other necessary information.

 

 

 

For both ZFT and ZHe, it would be easy to present the requested information in a table.

 

Overall, I recommend the publication of this paper.

 

 

 

Reviewer #1

Author Response

Dear Sir or Madam,

We appreciate the time and effort you expended on our manuscript. Your comments are very helpful for us to improve our manuscript.

According to the suggestions from you, we did a major revision on the original manuscript. Abstract, Method, Results, Discussions, and Conclusion Parts the earlier manuscript have nearly been re-written. Changes in detail corresponding to comments are outlined as follows:

 

Comments:

The paper discusses tectonic events during the late Carboniferous to early Permian, late Permian to early Triassic, and middle Triassic to late Triassic, using low-temperature thermochronology and seismic data. While the paper is well-written, it has some shortcomings, particularly in the thermochronology section. It appears that the authors focused more on seismic data and gave less importance to thermochronology. Here are some examples:

 

1. The authors used zeta-calibration, but they did not provide information about its values or the dosimeter used. Additionally, while they used age populations for geological interpretation, they did not present individual data information such as a grain-by-grain age table, despite the availability of RadialPlotter and age distribution.

Reply: Thank you very much for your constructive suggestions. Indeed, the study of low-temperature thermochronology in this basin has been much weak. The reasons may mainly be focused on, as you mentioned in the following comments, a large number of zircons were primarily recrystallized and may contain varying geochemistry, which has reached an agreement with the previous researchers, e.g., Li et al., 2015; Liu et al., 2020. The main work of this paper presented the seismic interpretation and basin modeling in the eastern Qaidam Basin, and how the Carboniferous strata respond to the controlling of tectonism, based on our collected thermochronological ages. In such scenarios, we reorganized the outline of this paper and emphasized that the ages originated from ZFT and ZHe were set as the constraints in our modeling (please find in section 3.2). So we do apologize for not providing detailed information about age populations and grain-by-grain ages as the request of concentrating on our main thoughts.

2. According to Table 1 and Figure 5, the maximum number of grains analyzed was 26, and the minimum was 12. For this kind of interpretation, one would expect more grains (around 50) per sample. However, low-temperature thermochronology faces a considerable challenge when dealing with zircon. There can be various reasons why enough zircon ages were not obtained, such as metamictization, lost grains during the etching process, or lack of grains for such analyses. Despite the small amount of grains analyzed, the authors were able to make a good correlation with the already published geological evolution.

Reply: We agree with this comment that the single-grain for zircon ages was toughly obtained. Based on this, we conducted as many low-temperature thermochronology studies as possible in the eastern Qaidam Basin. Therefore, in this study, we collected previous thermochronological ages and interpreted these with our seismic data and basin modelling results in the Discussion part (please find in section 5.3).

3. For ZHe, the authors did not provide information about the methodology (despite indicating the paper for that), but also individual ages (grain-by-grain) the amount of 4He, 238U, 235U, 232Th, size of the grains, raw ages, Ft factor, corrected age, or any other necessary information. For both ZFT and ZHe, it would be easy to present the requested information in a table.

Reply: Thanks for your suggestion. As mentioned above, the major work is to present the seismic interpretation and basin modeling results in the eastern Qaidam Basin and decipher how did the Carboniferous strata respond to the controlling of tectonism, based on the collected thermochronological ages. We do apologize again for not presenting the requested information in a table in the Method section. However, we collected as many thermochronological samples (AHe & ZHe) as possible this summer, and these are now being tested. So we will present the new data and deliver new explanations in another paper later next year.

 

 

Thanks again for your concern! Please do not hesitate to contact me if you have any questions.

Yours sincerely,

Chang Zhong and other authors

December, 2023

 

Liu, K.; Li, Z.; Shi, X.; Wei, X.; Ren, Z.; Yang, X.; Peng, B. Late Hercynian-Indosinian denudation and uplift history in the eastern Qaidam Basin: constraints from multiple thermometric indicators and sedimentary evidence. Chinese Journal of Geophysics 2020. 63(4): 1403-1421 (in Chinese with English abstract).

Li, Z.; Gao, J.; Zhen, C.; Liu, C.; Ma, Y.; Zhao, W. Present-day heat flow and tectonic-thermal evolution since the late Paleozoic time of the Qaidam Basin. Chinese J. Geophys 2015. 58, 3687-3705 (in Chinese with English abstract).

Reviewer 2 Report

Comments and Suggestions for Authors

Comments on ‘How did the late Paleozoic to early Mesozoic tectonism constrain the Carboniferous strata in the eastern Qaidam Basin, NW China: evidence from low-temperature thermochronology and seismic data’ by Chang Zhong et al. submitted to Geosciences.

 

In this study, the authors undertook an examination of the eastern Qaidam Basin (EQB), commencing with analysis of outcrops depicting unconformities. In order to achieve a holistic understanding, they employed low-temperature thermochronology techniques, including fission track and (U-Th)/He analyses, alongside basin modeling. This integrative approach incorporated data from drillings and 2D seismic reflection, facilitating the development of both simulative and kinetic models. This research aimed to elucidate two primary facets of significance: (1) unraveling the dynamics of the basin in response to the Paleo-Tethys and arc-continental collision within the EQB context; (2) evaluating the implications for oil and gas exploration services.

 

In general, I found that the acquired dataset is not sufficient to support the main conclusions derived. More specifically, for a detrital analysis, theoretically they need 100-120 grains (e.g., Vermeesch, 2004), and at least 60 grains will be needed. In this study none of the detrital ZFT samples meets this threshold (all <30), this is not acceptable. Further, it seems that the helium data are complete missing in the text, where is the original ZHe data? Having said that, the interpretations are largely based on seismic profiles, in this regard I do not think the tectonic model presented in Figure 11 is too much meaningful due to the clear signals of over-interpretations. In contrast, a simplified structural model like Figure 10 looks convincing, the authors could indeed narrow down and concentrate their discussions. Lastly, some contents look very confusing, such as lines 421-424.

 

The organization and scientific writing of the manuscript would also need large improvements.

 

Sincerely

The journal reviewer

2023.12.03

Comments on the Quality of English Language

Extensive editing of English language required.

Author Response

Dear Sir or Madam,

We appreciate the time and effort you expended on our manuscript. Your comments are very helpful for us to improve our manuscript.

According to the suggestions from you, we did a major revision on the original manuscript. Abstract, Method, Results, Discussions, and Conclusion Parts the earlier manuscript have nearly been re-written. Changes in detail corresponding to comments are outlined as follows:

 

Comments:

In this study, the authors undertook an examination of the eastern Qaidam Basin (EQB), commencing with analysis of outcrops depicting unconformities. In order to achieve a holistic understanding, they employed low-temperature thermochronology techniques, including fission track and (U-Th)/He analyses, alongside basin modeling. This integrative approach incorporated data from drillings and 2D seismic reflection, facilitating the development of both simulative and kinetic models. This research aimed to elucidate two primary facets of significance: (1) unraveling the dynamics of the basin in response to the Paleo-Tethys and arc-continental collision within the EQB context; (2) evaluating the implications for oil and gas exploration services.

 

1. In general, I found that the acquired dataset is not sufficient to support the main conclusions derived. More specifically, for a detrital analysis, theoretically they need 100-120 grains (e.g., Vermeesch, 2004), and at least 60 grains will be needed.

Reply: Thank you very much for your constructive suggestions. Indeed, the study of low-temperature thermochronology in this basin has been much weak. The reasons may mainly be focused on, a large number of zircons that were primarily recrystallized and may contain varying geochemistry, which has been reached an agreement with the previous researchers, e.g., Li et al., 2015; Liu et al., 2020. The main work of this paper presented the seismic interpretation and basin modeling in the eastern Qaidam Basin, and how the Carboniferous strata respond to the controlling of tectonism, based on our collected thermochronological ages. In such scenarios, we reorganized the outline of this paper and emphasized that the ages originated from ZFT and ZHe were set as the constraints in our modeling (please find in section 3.2). So we rewrite the Conclusions part regarding the deformation characteristics and modelling results.

2. In this study none of the detrital ZFT samples meets this threshold (all <30), this is not acceptable.

Reply: We agree with this comment that the least grains for ZFT ages were not enough. On the one hand, we do apologize for not presenting as many grains as possible in this paper, since we mostly pay attention to how tectonism controlled the evolution of the Carboniferous strata. We mainly utilize the seismic data and basin modelling method constrained by collected ZFT and ZHe ages. Indeed, we conducted the study of deformation characteristics and burial thermal history of the Carboniferous strata. The time of these geologic processes has been constrained by the previous thermochronological ages (Liu et al., 2020).

3. Further, it seems that the helium data are complete missing in the text, where is the original ZHe data?

Reply: Thanks for your suggestions. As mentioned above, the major work is to present the seismic interpretation and basin modeling results in the eastern Qaidam Basin, and decipher how did the Carboniferous strata respond to the controlling of tectonism. We do apologize again for not presenting the requested data information in a table in the Method and Result sections. However, we collected as many thermochronological samples (AHe & ZHe) as possible this summer, and these are now being tested. So we will present the new data and deliver new explanations in another paper later next year.

4. Having said that, the interpretations are largely based on seismic profiles, in this regard I do not think the tectonic model presented in Figure 11 is too much meaningful due to the clear signals of over-interpretations. In contrast, a simplified structural model like Figure 10 looks convincing, the authors could indeed narrow down and concentrate their discussions.

Reply: Thanks for your suggestions. To concentrate on the discussions, we reconstructed the structural evolution of the eastern Qaidam Basin from the Carboniferous to Triassic time, based on the subsidence/burial and uplift/exhumation history, and deformation characteristics of the Carboniferous strata. Additionally, we narrowed down our Discussion part, as we presented the possible dynamic mechanism that controlled the tempo-spatial evolution of the Carboniferous strata.

5. Lastly, some contents look very confusing, such as lines 421-424.

Reply: Thanks for your suggestion. We decided to delete this sentence because of its redundancy.

6. The organization and scientific writing of the manuscript would also need large improvements.

Reply: Thanks for this constructive suggestion. We reorganized the outline of our paper and improved our scientific writing in Title, Abstract, Method, Results, Discussions, and Conclusions Parts.

 

Thanks again for your concern! Please do not hesitate to contact me if you have any questions.

Yours sincerely,

Chang Zhong and other authors

December, 2023

 

Liu, K.; Li, Z.; Shi, X.; Wei, X.; Ren, Z.; Yang, X.; Peng, B. Late Hercynian-Indosinian denudation and uplift history in the eastern Qaidam Basin: constraints from multiple thermometric indicators and sedimentary evidence. Chinese Journal of Geophysics 2020. 63(4): 1403-1421 (in Chinese with English abstract).

Li, Z.; Gao, J.; Zhen, C.; Liu, C.; Ma, Y.; Zhao, W. Present-day heat flow and tectonic-thermal evolution since the late Paleozoic time of the Qaidam Basin. Chinese J. Geophys 2015. 58, 3687-3705 (in Chinese with English abstract).

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Comments on ‘How did the late Paleozoic to early Mesozoic tectonism constrain the Carboniferous stratigraphic evolution in the eastern Qaidam Basin, NW China’ by Chang Zhong et al. submitted to Geosciences.

 

Based on current step, there still remain several issues to be addressed in terms of the presentation of this work, which are listed below.

 

- The motivation of this study could benefit from further improvement, the current logic is not strong enough to put forwards why the topic of this study deserves further investigations and how this work is going to address at least some of the existing controversies.

 

- The authors stated that they have conducted field geological surveys (e.g., Line 16), however, I was missing the parts that could be related with field investigations. Is there any new field mapping? Could the authors provide any new structural data based on the field? Currently they are completely missing in the content.

 

- Please carefully check the English, for example, have a look at Lines 72-73, this is not a complete sentence.

 

- Quite a few terms or expressions looks not so professional, for instance, ‘in the paleogeographic position of the back-arc’ looks very confusing and would result in possible misunderstanding.

 

- I suppose Figure 6 is a success based on seismic profile analysis and basin modeling. However, I still stand that the tectonic models proposed in Figure 7 is currently far-fetched. Maybe it is correct but the discussion should call for more comprehensive analysis.

 

- I also found that the authors may have made some mistakes when interpreting thermochronological data. Cooling derived from low-T ages does not equal to surface uplift, I suggest the authors to have a deeper look into the related literatures and think twice before trying to connect low-T ages to regional tectonic events.

 

Sincerely

The journal reviewer

2024.01.04

Comments on the Quality of English Language

please carefully edit the language.

Author Response

Dear the journal reviewer,

 

We really appreciate the time and effort you expended on our manuscript. Your comments and suggestions are very helpful for us to improve our manuscript.

According to the suggestions from you, we did a major revision on the original manuscript. Abstract, Introduction, Method, Results, Discussions, and Conclusion Parts the earlier manuscript have nearly been re-written. Changes in detail corresponding to comments are outlined as follows:

 

Comments:

Based on current step, there still remain several issues to be addressed in terms of the presentation of this work, which are listed below.

 

1. The motivation of this study could benefit from further improvement, the current logic is not strong enough to put forwards why the topic of this study deserves further investigations and how this work is going to address at least some of the existing controversies.

Reply: Thank you very much for this constructive suggestion. We do apologize for any inconvenience due to the earlier generic and unappealing Introduction part. Here we revised the logic of this paragraph, and emphasized the significance of petroleum exploration and basic geological research on the hot topic of how did the tectonism controlled the tempo-spatial evolution of the Carboniferous strata.

2. The authors stated that they have conducted field geological surveys (e.g., Line 16), however, I was missing the parts that could be related with field investigations. Is there any new field mapping? Could the authors provide any new structural data based on the field? Currently they are completely missing in the content.

Reply: Thank you for your reminding! We do apologize for the misunderstanding caused by the choice of words. In this paper, the main purpose we want to emphasize is the unconformities, which were detected by the field work, wells/boreholes, and seismic interpretation. And our main work was the statistics of unconformities underlying the Mesozoic and/or Cenozoic strata in the eastern Qaidam Basin (EQB). In such scenarios, we revised our languages in the Abstract and Method part. Regarding the new work of field investigation, we do apologize for not providing a new structural map, as it has been in the process of editing since last summer. And we will publish this as soon as possible after the double-checking from both outcrops and 2D/3D seismic data.

3. Please carefully check the English, for example, have a look at Lines 72-73, this is not a complete sentence.

Reply: Thanks for your suggestion. We carefully revised this sentence.

4. Quite a few terms or expressions looks not so professional, for instance, ‘in the paleogeographic position of the back-arc’ looks very confusing and would result in possible misunderstanding.

Reply: Thanks for this suggestion. We revised and stated that the sediments formed and the basin developed in the passive continental margin and back-arc tectonic setting, respectively.

5. I suppose Figure 6 is a success based on seismic profile analysis and basin modeling. However, I still stand that the tectonic models proposed in Figure 7 is currently far-fetched. Maybe it is correct but the discussion should call for more comprehensive analysis.

Reply: Thanks for your suggestion. We decided to delete Figure 7 because the discussion part won’t be closely related to the innovative view on the coupling relationships of the basin and orogenic systems.

6. I also found that the authors may have made some mistakes when interpreting thermochronological data. Cooling derived from low-T ages does not equal to surface uplift, I suggest the authors to have a deeper look into the related literatures and think twice before trying to connect low-T ages to regional tectonic events.

Reply: Thanks for this constructive suggestion. We do agree with your statement that the cooling ages do not equal to surface uplift. As a result of the higher closure temperature of ZFT systems, the topographic influence on the ZFT samples become much less pronounced. In such scenarios, we do apologize for misusing the word of ‘uplift’ regarding to the analysis of ZFT ages. We revised the language in the Discussion section, and we believe it would be better to link low-T ages to the 'unroofing' process during the mid-Permian to the late Triassic period in the EQB (Sun et al., 2021). So we finally decided to use the word of ‘exhumation’ and/or ‘denudation’ carefully in this part.

7. please carefully edit the language.

Reply: Thanks for this constructive suggestion. We improved our English scientific writing in Abstract, Introduction, Method, Results, Discussions, and Conclusions Parts.

 

Thanks again for your concern! Thank you very much for your help and support. Please do not hesitate to contact me if you have any questions.

 

Yours sincerely,

 

Chang Zhong and other authors

 

6, Jan, 2024

 

 

Sun, J.; Dong, Y.; Ma, L.; Chen, S.; Jiang, W. Devonian to Triassic Tectonic Evolution and Basin Transition in the East Kunlun–Qaidam Area, Northern Tibetan Plateau: Constraints from Stratigraphy and Detrital Zircon U–Pb Geochronology. GSA Bul-letin 2021, 134, 1967–1993.

Round 3

Reviewer 2 Report

Comments and Suggestions for Authors

Comments on the R2 version by Zhong et al.

The contents have been improved a bit, but I would revised around the title of the ms, which looks a little bit awkward, for examples, New insights into xxx, evidence from xxx.

There are still some grammatical problem and awful sentences regarding the English writing, the authors are urged to have a careful proofreading before re-submission.

Sincerely

The journal reviewer

2024.01.15

 

Comments on the Quality of English Language

See my comments above

Author Response

Dear Sir or Madam,

We appreciate the time and effort you expended on our manuscript. Your comments are really helpful for us to improve our manuscript.

According to the suggestions from you, we did a minor revision on the original manuscript. We re-wrote our title 'How did the late Paleozoic to early Mesozoic tectonism constrain the Carboniferous stratigraphic evolution in the eastern Qaidam Basin, NW China'. And we improved our English scientific writing in Abstract, Introduction, Method, Results Parts.

Thanks again for your concern! Please do not hesitate to contact me if you have any questions.

Yours sincerely,

Chang Zhong and other authors

16, Jan, 2024