This paper, “Relict Landscape Evolution and Fault Reactivation in the Eastern Tianshan: Insights from the Harlik Mountains,” investigates the geological evolution of the Harlik Mountains in the easternmost Tianshan range, highlighting relict landscape growth and fault reactivation processes. It integrates topographic analysis, structural geology, and low-temperature thermochronology, particularly apatite fission-track (AFT) dating, to provide insight into the timing and processes that influenced this low-relief landscape development. The study establishes two major tectonic phases: cooling in the mid to late Early Cretaceous and subsequent fault reactivation during the Late Cretaceous to early Paleogene. The tectonic events substantially impacted the development of low-relief surfaces and fault movement in the Harlik Mountains.

This study substantially improves the understanding of tectonic and geomorphic evolution in the eastern Tianshan region. The combined effort of geomorphological and thermochronological addresses clarifies the origins of fault reactivation and landscape development. However, the study's dependence on a limited dataset, lack of discussion regarding climate variables, and limited utilization of real-time data urge improvement. It is a significant resource for researchers studying tectonic processes in active mountain ranges, especially in Central Asia. This assessment highlights both the strengths and weaknesses of the study paper. It recognizes the significance of the study while also proposing avenues for future research to build upon its conclusions.

The key limitations of this study that I observed when reviewing this paper and that can be addressed in the revision are as follows.

Major

1. The study can be helpful for understanding how the Harlik range has changed over time due to tectonics and geomorphology, but it only analyses certain important components, perhaps missing critical locations where geomorphic processes vary. While a larger sampling area would have improved the analysis, this study may use geomorphic indicators to find useful information in regions where ground data wasn't available. This approach, though constrained, offers a comprehensive understanding of the region’s tectonic and landscape dynamics within the available data framework. The author may utilize diverse ways to perform geomorphic analysis. Geomorphic metrics, such as the Stream Length-Gradient Index (SL), Mountain Front Sinuosity (Smf), and Basin Asymmetry Factor (Af), are valuable to assess tectonic activity. These indices can reveal anomalies in landscape patterns that may indicate regions of uplift or subsidence. Topographic analysis can utilize features such as river knickpoints, channel steepness (χ-analysis), or incision rates obtained from DEMs to deduce tectonic processes. In the lack of extensive field data, such indicators may provide significant insights into present or past tectonic activity.
2. This study acknowledges the influence of climate on erosion rates but fails to comprehensively assess its contribution to long-term landscape growth. A comprehensive analysis of this theme would enhance understanding of the influence of climatic variables on long-term geomorphic evolution in connection to tectonics. In regions with limited data, evaluating the impact of climate-induced erosion and sediment transport on geomorphic processes might improve our understanding of the evolution of landscapes. This method can be employed to examine the interaction between regional climate and tectonic uplift in shaping topography, particularly in elevated, low-relief regions influenced by glaciation, landslides, or fluvial systems.  Although this is not mandatory for this kind of study, it may be analyzed for connecting the relationship of climate and tectonics if authors find it useful to explain their hypothesis.
3. This study concentrates on historical fault reactivation but excludes contemporary or real-time fault observation datasets. Current geodetic or seismic data could have provided an improved understanding of current fault movement and the implications for the region's tectonic evolution.

Minor:

1. The abstract component could possibly be improved. This would enable a broader audience to comprehend the scientific narrative more effectively.
2. In numerous instances within the discussion section, the geomorphological, tectonic, and thermochronological narratives have not been adequately associated. If possible, please provide insights on how the combined role of topographic metrics, thermochronological datasets, and tectonics can support your hypothesis. 
3. Please rewrite the conclusion section if possible, incorporating examples of the future scope of this work and the limitations of this study.

Kindly refer to the annotated PDF file for detailed remarks that will assist the author in revising the article properly.

This paper uses an interdisciplinary approach to investigate the timing and processes behind the formation of relict low-relief landscapes in the Harlik Mountains in the Eastern Tianshan. Geomorphology and Structural analysis of the area were used to identify several low-relief surfaces and analyse their relation to the faults. AFT dating on new samples reveals the Mesozoic-Cenozoic uplift history of this region and provides new temporal data on the formation of these low-relief relict surfaces as well as the reactivation of faults. Two major evolutionary phases are identified: (i) Exhumation and related cooling in the Early Cretaceous and (ii) Reactivation of faults in the Late Cretaceous and the onset of the formation of the relict low-relief surfaces. The discussion brings up interesting points about the role of climate and aridification in the Cretaceous on the development of these relict surfaces and puts the study into the more regional tectonic picture.

The study adds some novel data to this region and the spatiotemporal development of low-relief surfaces in the wider region. I’m sure it will be of great use to the scientific community interested in Central Asian tectonics but also more widely in the development of low-relief relict surfaces in mountain belts. The paper is overall well-structured and fits the scope of the journal. I think some editing and restructuring of some parts would benefit the paper and would make the key messages clearer. Below are some general comments as well as further comments on the figures and line-specific comments to help with this:

General comments:

1. The abstract could be more concise and focused to better highlight the core contributions of the paper. I’d recommend restructuring it slightly, perhaps by moving the sentence “…
2. The figure captions could be more detailed and descriptive. Especially for some of the figures that contain a lot of information. These figures (for example 2 and 3) are full of useful information but require time to fully grasp, adding clearer figure captions highlighting the key points would help guide the reader and ensure they are more easily understood.
3. Section 3 would benefit from clearer separation between Methods, Results and Discussion to improve readability and structure. These sections on geomorphology and structural geology are a bit short and often mix methodology, and results with some discussion. I think these sections are important to the argument to investigate the spatial relations of the faults and low-relief relict surfaces but may need more elaboration. Currently, the paper feels primarily like an AFT–thermal modeling study, with remote sensing and geomorphology used to identify surfaces and some fieldwork to identify faults. To highlight the interdisciplinary nature of the study, the geomorphology and structural geology aspects could be developed further, particularly in providing further field-based evidence to strengthen the argument for fault reactivation. I think this would complement the overall conclusion of the paper well by showing some more evidence for these faults being reactivated (or references to relevant papers showing clear evidence for the reactivation of these particular faults). For the geomorphology part, you may look into a variety of further methods to quantify the landscape such as geomorphic indices (Surface-Roughness, Hypsometric Integral, Elevation-Relief Ratio for example) that can help deduce the tectonic history. This would help present a more complete picture and complement the other parts of the study.
4. Perhaps a more of a minor point but I think it would be helpful if the introduction, discussion and conclusion flow more seamlessly together by stating clearly the research questions in the introduction and coming back to these later. For example, comparing how the new data from the paper adds to existing theories or contests these. I think this would help the readability of the paper and make the reader aware of what they can expect to be discussed from the start.

Figure comments:

• Figure 2 – In (a), specifying fault types (as in 2c) would improve clarity. In (b), if these are SWATH profiles, adding a legend for line colours (as in Figure 3) and specifying corridor width would help make more clear what is being shown. The legend is also hard to read—enlarging the AFT age scale and repositioning one legend (e.g., to the right) would make it more readable. In (c), fault zones are difficult to distinguish—consider using colour (e.g., red for normal faults) and make strike-slip symbols larger.
• Figure 3 – Since this figure is key to illustrating low-relief surfaces, making their boundaries clearer would help. A supplementary figure showing just the topography with faults could aid verification, and a slope map in the supplement might further support surface identification. The small images in the bottom left of (a) are too small to be useful. Consider moving them to a separate figure or the supplementary material, with both uninterpreted and interpreted versions side by side.
• Figure 4 – I think as a whole this figure shows a lot of interesting information that is important to your argument but it’s also a very busy figure that is hard to read. I’m not sure if the thin section images add much beyond what the outcrop photos already show, —consider removing them – or explain more thoroughly in the figure caption what makes them important. The other images are important but too small to interpret effectively. Either enlarge them or keep the 3×3 layout and provide high-resolution versions in the supplement (with both interpreted and uninterpreted versions). Similarly, the stereonets are too small and should include details like the number of measurements (and ideally for open science purposes it would be great if a table with the raw data used to generate these is provided for reproducibility)
• Figure 5 – I like this figure, it is clear and well-structured. Consider adding more detail in the caption about the distribution of ages.
• Figure 6 – Another well-designed figure. Try to keep the age scale consistent across the right-hand panels, that makes it easier to see that fault-affected ages are younger.
• Figure 8 – A strong summary of the thermochronology findings. However, the tectonic drivers appear somewhat unclear and potentially speculative—consider refining this aspect for clarity.

Line-Specific comments:

• l.34-36 – I think this is a very interesting question. Since it’s introduced here, consider revisiting it in the discussion and conclusion. Does the data and model presented in this paper support any of the existing theories?
• l.100 – What is the significance of the Urumqi-Korla line? Clarifying the nature or basis of this line, along with relevant references, would be helpful.
• l.106 – What is the nature of the Palaeozoic strata in the Harlik Mountains? Is it the volcaniclastic rocks mentioned earlier? Just looking at the map in Fig.2 it appears the southern part of the Harlik Mountains has more of the igeneous intrusions, is there perhaps lithology influence on the formation of low-relief relict surfaces?
• l.238 – More details on the paleostress analysis would be useful—how was it computed? If faults were reactivated, I would expect different generations of kinematic markers or other field-based evidence. Is this observable in outcrop or thin section? I appreciate this may be beyond the paper’s scope, but are there any constraints on the ages of the faults, or is there material present that could be dated (fault-hosted calcite)? It would be interesting to compare such data with thermochronology results.
• l.245 – How were these faults delineated—field mapping, geomorphological constraints, or both? You mention that fault scarps are prominent, but this is hard for the reader to verify. A large unannotated topographic map (maybe in the supplementary material) could help show both the fault scarps and low-relief surfaces.
• l.259 – The ductile kinematic indicators on this fault are interesting, I assume these are Palaeozoic? Is this part of a more regional shear zone? What brittle features were used for palaeostress (strain) interpretation? Are you certain the left lateral kinematic indicators on this fault correspond to the same phase as the right-lateral ones on the other faults? Some additional evidence might help clarify this.
• l.396 – Can you elaborate on the relationship between the extensional environment and gentle topography? Wouldn’t extension lead to footwall uplift and development of topography – which would then be associated with cooling in the AFT data? Or was this phase just very gentle extension?
• l.410-418 – This argument may be difficult to follow for readers unfamiliar with the regional tectonics of this area. I think it is an important point and puts the study into the regional context, maybe consider expanding it and possibly adding a diagram or schematic illustrating the spatial and temporal aspects of these tectonic events.
• l.452 – Is there (field)evidence that faults showing later activity were reactivated? Are there any age constraints? I.e. Is it certain these are Palaeozoic faults being reactivated, or could these be solely Mesozoic structures?
• l.457-468 – This is an interesting argument, especially given the role of climate in relict low-relief landscape formation. However, I think this paragraph needs some rewording to make the argument clearer. Are you suggesting that wetter Jurassic conditions led to more significant erosion, with later aridification during the Mid-Cretaceous preserving the landscapes? A slight restructuring and elaboration on this might improve clarity.