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At the eastern Qilian Shan mountain front in the NE Tibetan Plateau, the Minle‐Damaying Fault (MDF), the southernmost fault of the North Frontal Thrust (NFT) system, has previously been proposed as an inactive structure during the Holocene. Here we present a detailed record of six strath terraces of the Xie River that document the history of active deformation of the MDF. One optically stimulated luminescence dating sample constrains abandonment of the highest terrace T6 at 12.7 ± 1.4 ka. The formation ages of the lower terraces (T4–T1) are dated by AMS 14C dating. The cumulative vertical offsets of the MDF recorded by these terraces are determined as 12.2 ± 0.4 m (T6), 8.0 ± 0.4 m (T5), 6.4 ± 0.4 m (T4), 4.6 ± 0.1 m (T3), and 3.2 ± 0.2 m (T1c) by an unmanned aerial vehicle system, respectively. A long‐term vertical slip rate of the MDF of 0.9 ± 0.2 mm/yr is then estimated from the above data of terrace age and vertical offset by a linear regression. Assuming that the fault dip of 35 ± 5° measured at the surface is representative for the depth‐averaged fault dip, horizontal shortening rates of 0.83–1.91 mm/yr are inferred for the MDF. Our new data show that the proximal fault (the MDF) of the NFT system at the eastern Qilian Shan mountain front has remained active when the deformation propagated basinward, a different scenario from that observed at both the western and central Qilian Shan mountain front.

The deep structure of active reverse faults is generally difficult to constrain from surface observations and may conceal shortening within the hinterland. Here we investigate the geometry of active, crustal-scale reverse faulting from deformation of an unusually extensive set of river terraces preserved along the Beida River through the northwestern Qilian Shan. Two generations of fill terraces (T1 and T2) are well preserved from the foreland basin to at least 45 km within the hinterland. Optically stimulated luminescence and 10 Be dating methods indicate that T1 was abandoned at 24 ± 3 kyr B.P.; T2 was abandoned at 144 ± 30 kyr B.P. The T2 terrace profile reveals a long wavelength fold (~30 km) with a largest vertical deformation of~120 m relative to T1. Both kinematic and elastic modeling of the deformed terraces indicate that folding is a result of movement along a steep reverse fault (~50 o ), which merges into ã 10°décollement at 15-17 km depth. Estimated slip at depth is 1.8 times higher than fault slip at the surface, indicating a substantial proportion of shortening is absorbed by folding of the range interior. The shortening rate since abandonment of T2 is 1.4 ± 0.4 mm/yr, which is consistent with previous research and makes up 23 ± 10% of the geodetic shortening rate across Qilian Shan orogen. Our results support that crustal-scale reverse-faulting accommodates shortening and northward propagation of the North Qilian mountain front and that the total shortening rate is distributed between multiple faults within the Qilian Shan and Hexi Corridor.