Dear Johannes,

Thanks for your attention and comment.

As proposed, the NE Pamir evolved from a Permian-Triassic back-arc setting to a collisional orogeny during the latest Triassic to the earliest Jurassic. Recent identification of the Triassic back-arc belt extending from northern Afghanistan to the NE West Kunlun Mountains in China (Rembe et al., 2022) suggests a more complex pre-Cenozoic evolution of the Paleo-Tethys in the Pamir segment than previously understood. However, the precise timing of the closure of this back-arc system remains unclear.

No direct geochronological constraints have been reported for this significant contractional event in the back-arc system. Regional low-temperature thermochronological records indicate uplift and cooling events in the Triassic and Late Jurassic (Yang et al., 2017). The closure of the Paleo-Tethys and the subsequent collisional orogeny likely happened in the latest Triassic, as evidenced by Triassic thrusts and stratal deformation observed in the western Tarim Basin (Wu et al., 2021). Notably, the Permian- Triassic volcanic rock only outcropped in the north segment (Qiemugan-Gaizi River) of the West Kunlun, whereas the south segment (Kyzyltau-Aertashi) was dominated by the carbonate sequence of platform sedimentation. The Triassic thrust belt and paleo-uplifts developed only in the south segment (Kyzyltau-Aertashi; Wu et al., 2021). Additionally, Permian-Triassic detrital zircons are absent from the Early-Middle Jurassic Kyzyltau basin in the West Kunlun Mountains (Fig. 6), implying sediment communication occurred only from the Late Jurassic to Early Cretaceous (Fig. 10). These lines of information support the hypothesis that partial closure of the Paleo-Tethys and back-arc seaway in the Pamir occurred during the latest Triassic.

We propose that the evolution of the Paleo-Tethys Ocean and the back-arc basin behaved differently between the NW Pamir segment (Qiemugan-Gaizi River) and the E North Pamir segment (Kyzyltau-Keliyang)  (Fig. 1c). It is likely that the Triassic back-arc basin did not extend into the E North Pamir segment, and the closure of the Paleo-Tethys varied between its northern and southern segments, influenced by the Late Paleozoic embayment in the Pamir region (Li et al., 2020).

Overall, the Mesozoic and Cenozoic evolution of the North Pamir region is more complex than current tectonic models suggest and requires further study.

Additionally, we are pleased to revised the stratigraphic column in Fig. 9 to present the thick Triassic volcanic sequence in the NW Pamir.

Thanks for your valuable suggestion.

Best Regards,

Hongxiang Wu

Rembe, J., Sobel, E. R., Kley, J., Terbishalieva, B., Musiol, A., Chen, J., and Zhou, R.: Geochronology, Geochemistry, and Geodynamic Implications of Permo-Triassic Back-Arc Basin Successions in the North Pamir, Central Asia, Lithosphere, 2022, 10.2113/2022/7514691, 2022.

Yang, Y.-T., Guo, Z.-X., and Luo, Y.-J.: Middle-Late Jurassic tectonostratigraphic evolution of Central Asia, implications for the collision of the Karakoram-Lhasa Block with Asia, Earth-Science Reviews, 166, 83-110, https://doi.org/10.1016/j.earscirev.2017.01.005, 2017.

Wu, H., Cheng, X., Chen, H., Chen, C., Dilek, Y., Shi, J., Zeng, C., Li, C., Zhang, W., Zhang, Y., Lin, X., and Zhang, F.: Tectonic Switch From Triassic Contraction to Jurassic-Cretaceous Extension in the Western Tarim Basin, Northwest China: New Insights Into the Evolution of the Paleo-Tethyan Orogenic Belt, Frontiers in Earth Science, 9, 10.3389/feart.2021.636383, 2021.

Li, Y.-P., Robinson, A. C., Gadoev, M., and Oimuhammadzoda, I.: Was the Pamir salient built along a Late Paleozoic embayment on the southern Asian margin?, Earth and Planetary Science Letters, 550, 116554, https://doi.org/10.1016/j.epsl.2020.116554, 2020.

Thank you very much for your time and valuable suggestions. We will address your queries individually below. Additionally, our co-authors, two American academics, Yildrim and Andrew, have contributed to revising and refining the language.

About major comments:

1. We agree with your suggestion and have revised our title to: ' Switching Extensional and Contractional Tectonics in the West Kunlun Mountains During Jurassic.’

2. We have removed the discussion regarding the interpretation of Jurassic molasse deposits; please refer to line 191. We suggest retaining the first sentence in this paragraph, as the first-order geodynamic mechanisms in the mid-Mesozoic are the most important focus of this paper.

3. Based on a detailed classification and statistical analysis of zircon characteristics in Table S2, we identified a strong correlation among the morphology, internal structure, and age of zircons from the basalt. Type 1 zircons, typically euhedral to sub-euhedral with clear oscillatory zoning, have older ages ranging from 405 Ma to 911 Ma. In contrast, type 2 zircons, which exhibit subrounded external shapes, show uniform Jurassic ages between 168 Ma and 193 Ma. Please refer to discussion in line 335-340.

We have assigned the younger ages (type 2) to represent the crystallization age of this basaltic rock sample, while the older ages (type 1) are interpreted as inherited from the country rocks. Notably, the older ages in the basalt sample are consistent with the detrital zircon ages found in the study region.

4. The provenance of the Jurassic sedimentary rocks is locally sourced from the North West Kunlun Mountains, which are primarily composed of Early Paleozoic sedimentary rocks (lines 616-635). Younger detrital zircons, dating of the Carboniferous and Triassic ages, in the South West Kunlun Mountains, were transported into the Tarim Basin beginning in the Late Jurassic and Early Cretaceous (Fig. 10). As a result, a significant gap between the youngest zircon age and the actual depositional age can be observed.

Additionally, the Early Jurassic basalts are scattered throughout this region, making them insufficient to serve as a major source. Zircon is also difficult to crystallize in these mafic magmas due to their silicon unsaturation. To better understand the Jurassic depositional age of this sedimentary package, we present several lines of evidence as follows: (1) the age spectrum of the sandstone from Kandilik is remarkably similar to that of the Early Jurassic strata (Fig. 6); (2) the structural compatibility of this new stratigraphic scheme was we demonstrated (line 487-499); (3) The clastic member in Kandilik is primarily composed of gray-black carbonaceous slate and siltstone, similar to the Jurassic coal-bearing sequences.

5. In this revised version, we have significantly shortened the discussion about the tectonic setting in the section 6.1 and 6.2. Please refer to line 548-574.

6.  We briefly discussed the comparable geological history between the Pamir-West Kunlun and the Tibetan Plateau and added a summary of this in the conclusion section.

About minor comments:

1. We have added a field geological section to show the regional strata and deformation in Figure 2c.

2. We have added several field photos of conglomerate clast lithologies from Oytag, Gaizi and Tamu regions in Figure 2.

3. We have explained the meaning of the different colored circles in the caption of Figure 4.

4. The subscale numbers in Figure 5b represent the zircon test sites shown in Figure 5a that were not used to calculate the weighted mean age. We have deleted these subscale numbers in this revised version.

5. We have highlighted the chemical differences among magmatic rocks in the discussion section 6.3 (lines 685-690). In particular, we emphasize the back-arc MORB affinity of the basalts in Tanshuihai and the OIB-affinity (within-plate) of the basalts in West Kunlun, which is comparable to the tectonic setting of the active margin of the western Pacific (line 713-718).

6. We have corrected this mistake.

7. We have corrected this mistake.

8. We have shortened both the section 6.1 and 6.2 in this revised manuscript, and have added a summary of basin evolution for the section 6.2 (line 640-645).

Thank you very much for your consideration and suggestion. We will address your questions and make the following revision.

1.  We have mentioned the South Qiangtang and North Qiangtang terranes in this paragraph.

2. Due to the exposure conditions and harsh terrain, we were unfortunately unable to capture clear photographs showing the contact between the basalt and surrounding strata. These basalts were found in the upper layer of volcanic breccia, and detailed profiles were measured by geologists as early as the 1990s (Ma et al., 1991). To provide readers with a clearer understanding of the strata formation and rocks we collected, we have added a field outcrop profile of the area in Fig. 2c.

3. In this revised version, we have conducted a detail classification and statistical analysis of zircon characteristics in Table S2. Based on the morphology, internal structure (CL), and age of zircons from the basalt, we have divided the 36 zircons we tested into two groups. The type 1 zircons, typically euhedral to sub-euhedral with clear oscillatory zoning, have older ages ranging from 405 Ma to 911 Ma. In contrast, the type 2 zircons, exhibiting subrounded external shapes with no clear oscillatory zoning, show uniform Jurassic ages between 168 Ma and 193 Ma.

The older ages in the basalt sample are consistent with the detrital zircon ages found in the country rocks in the study region (Fig. 6). Accordingly, we have assigned the older ages (type 1) as inherited from the country rocks, while he younger ages (type 2) to represent the crystallization age of this basaltic rock sample.

The low Th/U ratios, occurred only within the zircon group of type 2, which has a “polished” shape with nebulous or patchy-zoned centers. This may result from moderate resorption either during the evolution of the magma chamber when the magma is oversaturated with respect to zircon or a certain degree of metamorphism (Corfu et al., 2003). Despite this, most zircons still display high Th/U ratios, indicating a clear magmatic origin. Therefore, we believe the Jurassic age represents the crystallization age of the volcanic rocks. Please refer to discussion in line 335-340.

4. To better understand the Jurassic depositional age of this sedimentary package, we present several lines of evidence as follows: (1) the age spectrum of the sandstone from Kandilik is remarkably similar to that of the Early Jurassic strata (Fig. 6); (2) the structural compatibility of this new stratigraphic scheme was we demonstrated (line 487-499); (3) The clastic member in Kandilik is primarily composed of gray-black carbonaceous slate and siltstone, similar to the Jurassic coal-bearing sequences.

5. We have added more information about this event in the South Qiangtang and Bangong-Nujiang suture zone. We also cited these important papers in our revised manuscript (line 233 and 626). In the final discussion section, we further discussed the relationship between the basin inversion in South Qiangtang and the evolution of the Meso-Tethys.

6. Jurassic strata are entirely absent in the West Kunlun Mountains. Only in some region, such as east of Tashkurghan, the Lower Cretaceous reddish sandstones unconformably overlie Paleozoic strata and Triassic granitoids.

References:

Ma, S., Wang, Y., and Fang, X.: Basic characteristics of Proterozoic Eonothem as a table cover on northern slope, Xinjiang Geology, 9, 59-71, 1991 (in Chinese with English abstract).

Corfu, F., Hanchar, J. M., Hoskin, P. W. O., and Kinny, P.: Atlas of Zircon Textures, Reviews in Mineralogy and Geochemistry, 53, 469-500, 10.2113/0530469, 2003.