Constraining Late Quaternary Crustal Shortening in the Eastern Qilian Shan From Deformed River Terraces

Abstract

The Qilian Shan, located in the northeastern Tibet, is under strong tectonic activity and earthquake motion due to the propagation of the plateau. At the mountain front of the eastern Qilian Shan, the Tongziba River, in the southern Zhangye Basin, flows northward and successively cuts the Minle-Damaying Fault and the Yonggu Anticline, two parallel structures within the Frontal Thrust system of the Qilian Shan. Here we present a detailed record of seven strath terraces of this river that documents the history of active deformation of the two structures. Based on the estimated crustal shortening distance from the deformed terraces and the terrace formation age constrained by AMS 14 C and optically stimulated luminescence (OSL) dating, a horizontal slip rate of 1.4 ± 0.5 mm/year of the Minle-Damaying Fault is constrained since 16.7 ± 1.8 kyr, and a shortening rate of 1.3 ± 0.4 mm/year across the Yonggu Anticline has been estimated in a similar time frame, respectively. In total, the shortening rate across the mountain front is estimated to be 2.7 ± 0.6 mm/year. GPS data show a similar modern shortening rate in this area, which indicates the rate of crustal shortening may be comparable in the modern and 10 4-year scales. Our study supports a higher crustal shortening rate along the mountain front of the eastern Qilian Shan than that of the western Qilian Shan since the Late Quaternary.

Slip Rate of the Danghe Nan Shan Thrust Fault from 10Be Exposure Dating of Folded River Terraces: Implications for the Strain Distribution in Northern Tibet

“…This value is identical within error to the GPS-based shortening rate of 5.2 ± 0.3 mm/ year along the 350-km-long profile line extending from the Hexi Corridor to the western Qaidam Basin (Figure 1) and agrees with the shortening rate of 5.5 ± 1.5 mm/year obtained by Zhang et al (2004) using older GPS data. Farther east along a N30°E-trending profile across the central Qilian Shan, a slightly higher GPS-based shortening rate of 7.9 ± 1.9 mm/year has been reported by Zhong et al (2020). The similarity between the millennial shortening rate and the GPS-derived rates suggests that most of the contractional strain in northern Tibet is taken up by fold-and-thrust systems along the major mountain ranges.…”

“…Note that Figure 6 shows the rotated topographic profiles with a horizontal reference level, but this minor rotation is ignored when deriving the vertical and horizontal distances, as well as fault dip angles for the following analysis (cf. Hu et al, 2015;Zhong et al, 2020).…”

“…The geometry of the ∼500-m-wide asymmetric anticline is similar to folded river terraces that occur at a larger scale along the mountain front of the Qilian Shan, and suggests the presence of a listric fault, with a steeper segment near the surface and a shallower segment at greater depth (cf. Hu et al, 2015;Liu et al, 2019;Zhong et al, 2020).…”

Effects of Erosion and Deposition on Constraining Vertical Slip Rates of Thrust Faults: A Case Study of the Minle–Damaying Fault in the North Qilian Shan, NE Tibetan Plateau

“…The vertical slip rate of a fault is a significant metric to quantify the intensity of tectonic activity (Tapponnier et al, 1990;Hetzel et al, 2002;Ai et al, 2017;Liu et al, 2017), reconstruct the behavior of the fault over time (Zheng W. J. et al, 2013;Xiong et al, 2017;Hetzel et al, 2019), evaluate the seismic risk (Ren et al, 2019;Lei et al, 2020), and understand the regional active deformation (Yang et al, 2018;Liu et al, 2019;Ren et al, 2019;Zhong et al, 2020). The estimation of vertical slip rates mostly depends on two factors: the magnitude of the offset and the age of offset landmarks (Burbank and Anderson, 2011).…”

Test on the Reliability of the Subsurface Fault Geometry Estimated by Deformed River Terraces Along the Bailang River, North Front of the Qilian Shan (North West China)

“…In the profit from the development of kinematic models for fault-related folds (Suppe, 1983;Suppe and Medwedeff, 1990;Erslev, 1991;Hardy and Poblet, 1994;Wickham, 1995;Allmendinger, 1998;Mitra, 2003;Cardozo, 2008;Hardy and Allmendinger, 2011;Poblet and Lisle, 2011;Brandes and Tanner, 2014), scholars try to estimate the active fold geometry using deformation patterns of geomorphic markers (Thompson et al, 2002;Gold et al, 2006;Scharer et al, 2006;Wilson et al, 2009;Burgess et al, 2012). Based on kinematic models for fault-related folds geometry and geomorphic deformation, the geometry of the related fault can also be estimated (Hu et al, 2015(Hu et al, , 2017(Hu et al, , 2019bLiu et al, 2019;Wang et al, 2020;Zhong et al, 2020), which provides a more convenient way to investigate the subsurface fault geometry. Due to the uncertainty derived from the selection of the fold model and from the assumption of the fault dip close to the surface (e.g., Hu et al, 2015), the reliability of the estimated fault geometry is still questionable.…”