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

Abstract

The ongoing convergence between India and Asia causes widespread deformation of the Tibetan Plateau (e.g., Styron et al., 2010;Tapponnier and Molnar, 1977;Taylor et al., 2003). In the northern part of the plateau (i.e., north of the Kunlun strike-slip fault), deformation is mainly partitioned into thrust and strikeslip faulting (e.g., Meyer et al., 1998;Zheng et al., 2013a). In contrast to the more easily accessible plateau margins (i.e., the Altyn Tagh fault and the Qilian Shan), where various studies have determined fault slip rates (e.g.,

Post‐20 ka Earthquake Scarps Along NE‐Tibet's Qilian Shan Frontal Thrust: Multi‐Millennial Return, ∼Characteristic Co‐Seismic Slip, and Geological Rupture Control

“…Given the thrust dip-angles (Figures 8a, 10a, 12a and 14a), such throw rates imply horizontal shortening rates on the order of ∼1.4 ± 0.3 mm/a, broadly comparable to previous large-scale, long-term inferences (e.g., Meyer et al, 1998;Tapponnier et al, 1990). The post-LGM shortening rate we discuss here is a fraction of the rate deduced from present-day GPS measurements (∼7 mm/a between the Qaidam basin and Hexi corridor, e.g., Zheng, Zhang, He, et al, 2013;Xu et al, 2021). It is also smaller than the minimum Cenozoic rate (3.3 ± 0.6 mm/a) derived from balanced geological cross-sections across the northern Qilian range (e.g., Zuza et al, 2016).…”

“…This is because the Gulang fault branches off the Lenglongling and Haiyuan Faults (e.g., Lasserre et al, 1999Lasserre et al, , 2002, while the latter includes parallel segments (e.g., Deng et al, 1986;Gaudemer et al, 1995;Li et al, 2017;Liu-Zeng et al, 2015;Matrau et al, 2019), and active strands of the former west of Menyuan are still poorly documented. Nevertheless, the fact that the large, parallel thrusts that underlie the Qilian Shan, Daxue Shan, Shulenan Shan, Danghenan Shan, and Tergun Daba Shan, contribute to transfer strike-slip rates from the Altyn Tagh to the Haiyuan Faults is beyond doubt (e.g., Daout et al, 2016;Gaudemer et al, 1995;Hetzel et al, 2004;Liu et al, 2021;Métivier et al, 1998;Meyer et al, 1998;Tapponnier et al, 1990;Xiong et al, 2017;Xu et al, 2010;Xu et al, 2021;Zheng, Zhang, He, et al, 2013) (Figure 22). Fits with events 2, 3, 4, and 6 are acceptable, two of (event 2 and event 3) which are also consistent with paleoseismic data (yellow rectangles with dashed contours).…”

“…As one of the youngest Mountain ranges of China, it provides an ideal laboratory to study the growth mechanisms of the Plateau (e.g., Hetzel et al., 2004; Métivier et al., 1998; Meyer et al., 1998; Palumbo et al., 2009; Tapponnier et al., 1990, 2001). It is generally acknowledged that the Qilian Shan now accommodates up to ∼20% of the overall India‐Eurasia convergence (e.g., Liu et al., 2019; Meyer et al., 1998; Yuan et al., 2013; Zhang et al., 2004; Zuza et al., 2016), with a total shortening rate between the northern Qaidam basin and the Hexi Corridor on the order of ∼5–7 mm/a (Figure 1), essentially across five parallel mountain ranges and their associated bounding thrusts (e.g., Hetzel et al., 2004; Meyer et al., 1998; Xu et al., 2021; Zhang et al., 2004) (Figures 1 and 2). As it hosts a series of parallel thrust faults which control both mountain growth and intermountain basin deposition, the broader Qilian Shan Thrust Belt (QSTB) has been interpreted to overly a shallow ∼5° SW‐dipping décollement into which the steeper crustal‐scale ramps root (e.g., Métivier et al., 1998; Meyer et al., 1998; Tapponnier et al., 1990).…”

Tectonic Deformation of the Western Qilian Shan in Response to the North–South Crustal Shortening and Sinistral Strike-Slip of the Altyn Tagh Fault Inferred From Geomorphologic Data

“…The Qilian Shan is regarded to be a continental stepover between the Altyn Tagh and Haiyuan faults (Zhang et al, 2007). The GPS observations and geological investigations reveal that the Qilian Shan accommodates the sinistral slip rate component of ~8 mm/a of the Altyn Tagh fault and the strain is partitioned into the compressional deformation and sinistral strike-slip of the faults in the Qilian Shan (e.g., Zhang et al, 2007;Zheng et al, 2013b;Liu J. et al, 2020;Xu et al, 2021). Moreover, the GPS data also show NNE shortening at a rate of 5.5 ± 1.5 mm/a between the Qaidam Basin and Hexi Corridor, which is mainly absorbed by NWW-trending mountain ranges and fault zones in the western Qilian Shan (Zhang et al, 2004).…”

“…To the west, a shortening rate of 2.1 ± 0.6 mm/a has been estimated for the northern frontal thrust system of the Daxue Shan (Meyer et al, 1998), which is aligned on the Tuolai Nan Shan and Shulenan Shan, jointly constituting the boundary between the central Qilian Shan and southern Qilian Shan (Hu et al, 2021). By applying 10 Be exposure dating to samples from deformed river terraces, Xu et al (2021) obtained a mean uplift rate of 0.6 ± 0.2 mm/a and a shortening rate of 0.8 ± 0.2 mm/a for the Danghe Nan Shan frontal thrust fault (Figure 10). The southern Zongwulong Shan thrust, the southern margin of the southern Qilian Shan, has a Holocene shortening rate of 0.5 ± 0.1 mm/a (Shao et al, 2019).…”