Meso-Cenozoic Tectonic and Geomorphic Evolution of the Eastern Tianshan: Insights from the Barkol Mountains and Hami Basin

This study explores the formation, preservation, and uplift of relict low-relief surfaces in the Barkol Mountains, coupled with sedimentological and geochemical insights from the Hami Basin. By integrating digital geomorphic analysis, structural mapping, thermochronology, and sedimentary data, the research reconstructs the tectonic and geomorphic evolution of this region.

Using Shuttle Radar Topography Mission (SRTM) data (3-arc-second resolution), relict low-relief surfaces in the Barkol Mountains were identified based on slope thresholds (<14°) and hydrological analysis in ArcGIS. Cross-sectional profiles and slope-aspect analyses highlight tectonic influences, including fault-induced tilting and segmentation, with boundary faults playing a significant role in surface deformation.

Apatite fission track (AFT) analyses from granitic samples reveal prolonged slow cooling during the Late Cretaceous (124.6–63.5 Ma), indicating minimal exhumation and surface preservation. Younger AFT ages (50–55 Ma) near the southern boundary fault suggest Paleogene fault reactivation and accelerated cooling. Single-grain AFT ages from modern river sands on the southern slope are dispersed, with peaks at 135.7 ± 9 Ma, 86.4 ± 5.3 Ma, and 50.4 ± 4.7 Ma, corresponding to bedrock ages. Apatite (U-Th)/He (AHe) data corroborate these findings, with younger ages (~30 Ma) in faulted regions, reflecting enhanced exhumation due to tectonic activity. These results underscore the structural control of exhumation processes, contrasting slow hinterland cooling with rapid fault-zone cooling.

In the Hami Basin, sedimentological and geochemical analyses of Cretaceous and Cenozoic deposits link sediment provenance to tectonic uplift. Detrital AFT ages from basin sediments show peaks at ~170 Ma and ~100 Ma, aligning with erosion events in the Bogda and Harlik-Barkol Mountains. Geochemical analysis reveals that apatite ages from mafic rocks cluster in the Middle Jurassic, while those from granitic rocks concentrate in the Early Cretaceous, corresponding to sources in the Bogda and Harlik-Barkol Mountains, respectively. This pattern likely reflects the sequential uplift and exhumation of the Bogda and Harlik-Barkol Mountains.

In conclusion, the Barkol Mountains exhibit relict surfaces formed during slow Late Cretaceous cooling, disrupted by Paleogene fault reactivation and accelerated exhumation. Additionally, the Hami Basin archives sedimentary records of tectonic-driven erosion, offering insights into the interplay between tectonics, geomorphology, and basin evolution in the Eastern Tianshan.