| Formation and evolution of river terraces can be affected by the crustal deformation, especially in active tectonic area; the tectonic movement can be sensitively responsed by river terraces. Deformed fluvial river terraces, distributed on both sides of the river as linear or flat landscapes, can served as perfect markers of local tectonic deformation. River terraces can record the accumulative displacement by active folds or active faults, and in combining chronology study, the deform rates in the region will be constrained.Much more researchs focused on the tectonic evolution, uplift rates and the formation age and development patterns of river terraces in the Qilian Shan, whereas few studies are executed on the tectonic geomorphology in interior Qilian Shan, expecially in the middle and western Qilian Shan. The uplift of Yumu Shan is in pace with the Qilian Shan, and is growing both laterally and vertically. The tectonic evolution, however, is not very clear by now. Aboundant geomorphic markers distributed in the front and the interior of the Qilian Shan mountain belt provide useful material in studying the tectonic deformation. Dahe river terraces, locating in the middle portion of the Qilan Shan, has be intensely warped and displaced due to the local tectonic movement, and would greatly facilitate the research on local tectonic deformation. Accordingly, we carry out detailed field work and OSL dating on Dahe River terraces, and some detailed information are found as follow:Five stepped river terraces are developped along the Dahe River. OSL dating shows the formation age of T4 is 80～100 ka B.P., T3 is～20 ka B.P., and T2 is～12 ka B.P. Dahe river terraces has been warped by tectonic movement after it's formation, and the fold developed through limb rotation and hinge migration. Based on the uplift height at the core and the duration time of the anticline, the uplift rates of the Panjiawan anticline core are derived as:0.19～0.25 mm/a between～100 ka B.P. and～20 ka B.P.,1.75 mm/a between～20 ka B.P. and～12 ka B.P., and 2.75 mm/a in Holocene. The fold deformation is related to the under fault process, so the core of the fold is gradually propagated northward. The fold propagation rate is determined as:26～32mm/a since～100 ka B.P.,-67.6 mm/a since～20 ka B.P., and～100 mm/a since 12 ka B.P. If we consider the rate of 26～100 mm/a as the fold propagation rate in the study area, it will indicate that the beginning of the Yumu Shan uplift is 1-2 Ma later than the Qilian Shan. By caculated the deformed river terrace transaction length minus its project length, the regional surface shorten rate is obtained:(0.09-0.12) mm/a since 100 ka B.P. Through calculating the excess area in ramp depth by the topography of deformed river terraces, the regional crust shortening rate is derived:0.5～1.2 mm/a since～100 ka B.P.,1.5-3.1 mm/a since～20 ka B.P. and 1.7～3.4 mm/a since～20 ka B.P.These data suggest that crust shortening mainly absorbed by the bedding thicking and the surface overall uplift induced by thrust of sub-surface blind fault. The tectonic activity of deep crust accompanies with the sliding of bedding material, the material compaction and solution, or material lateral transfer, all of which can leading to a weak surface deformation. The thrust of faults is the mainly pattern of Crust shortening.There is a main detachment in the crust of the Qilian Shan, and all of the sub-thrust faults are thrust orogeny above the detachment. The North Frontal Thrust of the Qilian Shan (the Yumu Shan) is the main frontal thrust of the detachment. The sub-thrust above the detachment led to the Dahe rive terraces strongly deformed since the late Pleistocene. As the depth of detachment from the mountain to the piedmont decreasing until it exposing on surface, the pressure of overlying rock mass decreases, so the fold wavelength decreases from the river upstream to the front of the Yumu Shan.GIS analysis indictes the slope in anticline area is larger than that in the syncline area. The slope change and the tectonic deformation have a good correspondence, which can distinctly reflect the topographic differences deduced by tectonic deformation.
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