Accommodation of India–Asia convergence via strike-slip faulting and block rotation in the Qilian Shan fold–thrust belt, northern margin of the Tibetan Plateau

Abstract

Existing models of intracontinental deformation have focused on plate-like rigid-body motion versus viscous-flow-like distributed deformation. To elucidate how plate convergence is accommodated by intracontinental strike-slip faulting and block rotation within a fold-thrust belt, we examine the Cenozoic structural framework of the central Qilian Shan of northeastern Tibet, where the northwest-striking, right-slip Elashan and Riyueshan faults terminate at the west-northwest-striking, left-slip Haiyuan and Kunlun fault. Field- and satellite-based observations of discrete right-slip fault segments, releasing bends, horsetail termination splays, and off-fault normal faulting suggest the right-slip faults accommodate block rotation and distributed west-east crustal stretching between the Haiyuan and Kunlun faults. Luminescence dating of offset terrace risers along the Riyueshan fault yields a Quaternary slip rate of ∼1.1 mm/yr, which is similar to previous estimates. By integrating our results with regional deformation constraints, we propose that the pattern of Cenozoic deformation in northeastern Tibet is compatible with west-east crustal stretching/lateral displacement, non-rigid off-fault deformation, and broad clockwise rotation and bookshelf faulting, that together accommodate northeast-southwest India-Asia convergence. In this model, the faults represent strain localization that approximate continuum deformation during regional clockwise lithospheric flow against the rigid Eurasian continent.Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

Strain Transformation Adjacent to the West Qinling Orogen: Implications for the Growth of the Northeastern Tibetan Plateau

“…In addition, strain rates significantly decrease to the east of 105°-106°E (similar with the GPS velocity field, background in Figures 3A,B), which may identify the significant deformation regions accommodating the outward expansion of the northeastern Tibetan Plateau (at least in the upper crust) resulting from India-Eurasia convergence being blocked by the rigid Ordos block. The rotation rates in Figure 3C (background color) show the clockwise rotation of the West Qinling orogen and the Lanzhou (Longxi) sub-blocks and the anticlockwise rotation of the sub-blocks adjacent to the Haiyuan and Kunlun faults, which are required by the book-shelf kinematic model (i.e., Zuza and Yin, 2016;Cheng et al, 2021).…”

“…Slip rates of the West Qinling fault are far smaller than other NWW-directed sinistral active faults within the region, such as the Kunlun fault, which exhibits slip of 2.0 ± 0.4 mm/yr along its eastern segment to ∼16 mm/yr along its western segment (Kirby et al, 2007;Harkins & Kirby, 2008;Harkins et al, 2010;Loveless & Meade, 2011), and the Haiyuan fault with 1-3 mm/yr along the western segment to 8-10 mm/yr along the eastern segment (Hao and Zhuang, 2020;Li Y. et al, 2018;Loveless & Meade, 2011;Yao et al, 2019;Yuan et al, 2013). The slow slip of the West Qinling fault can be related to limited convergence transfer and that a majority of the strain has likely been absorbed and partitioned by crustal shortening, block rotation, and east-west stretching along the West Qinling orogen (Chen & Lin, 2019;Cheng et al, 2021;Zheng et al, 2016).…”

“…In one aspect, some studies suggest that the crustal materials in the northeastern Tibetan Plateau are escaping eastward along the Qinling Mountains and/or beneath the Ordos block (Li S. et al, 2018;Royden et al, 2008;Royden, 1997;Yu & Chen, 2016). Meanwhile, others highlight that the deformation is mainly limited within the plateau and is accommodated by crustal shortening, block rotation, fault movements, and mountain building (Cheng et al, 2015(Cheng et al, , 2021Hao et al, 2021;Kirby et al, 2007;Li Y. et al, 2018;Zheng et al, 2016;Zuza and Yin, 2016).…”

Nonrigid Bookshelf Kinematics of Northeastern Tibet: Constrains from Fault Slip Rates around the Qinghai Lake and Chaka-Gonghe Basins

“…Obtaining the slip rates of the major strike-slip faults can be used as an indirect method to constrain the rate of rotation. Displaced alluvial landforms show right-lateral slip of the ELSF and RYSF, and the rates were constrained to bẽ 1.2 mm/yr since the late Pleistocene [25,36]. However, the geological slip rates are inconsistent with the predicted rates of~2-5 mm/yr from block modeling [33,35,37].…”

“…Lateral crustal extrusion, deduced from the high slip rates (10-30 mm/yr) on the major left-lateral faults including the Altyn Tagh fault (ATF), Haiyuan fault (HYF), and East Kunlun fault (EKLF), states that northeastern Tibet moves eastward as a rigid block with no internal deformation and rotation [8][9][10][11][12][13][14]. The left-lateral simple shear model suggests that the kinematics of northeastern Tibet can be explained by a combination of rotation and shortening within the blocks with little crust materials moving eastward [15][16][17][18][19][20][21][22][23][24][25]. England and Molnar [21] suggest that the crustal blocks within the large left-lateral faults are a manifestation of north-striking right-lateral simple shear zone and may rotate clockwise at 1-2 deg/Myr.…”