Early Cenozoic exhumation in the Qilian Shan, northeastern margin of the Tibetan Plateau: Insights from detrital apatite fission track thermochronology

Abstract

The Qilian Shan is a reactivated fold‐thrust belt at the northeastern margin of the Tibetan Plateau (TP). The initiated timing of the Qilian Shan's tectonic response to Indian‐Asian plate convergence has significant implications for our understanding of the growth of the TP, yet remains a controversial topic. We conducted apatite fission track analyses of the Cenozoic synorogenic sediments in the Subei Basin on the northwestern flank of the Qilian Shan to investigate the time of initial Qilian Shan deformation during the Cenozoic. An integration of new and existing detrital apatite fission track ages indicates that terranes in the Qilian Shan experienced a prominent tectonic exhumation event at ~60–50 Ma. This result suggests that tectonism initiated on the northeastern margin of the TP nearly simultaneously with the India‐Asia collision.

Early Cenozoic activated deformation in the Qilian Shan, northeastern Tibetan Plateau: Insights from detrital apatite fission‐track analysis

“…The ca. 60–50 Ma static peak of detrital AFT ages was also discovered in the Neogene HTTL section in the northeastern Qaidam Basin (He et al., 2018), in the Cenozoic sediments of the Jiuquan Basin north of the Qilian Shan (He et al., 2017) and the Subei Basin northwest of the Qilian Shan (He et al., 2020), suggesting that late Paleocene‐early Eocene rock exhumation occurred extensively in the Qilian Shan. This interpretation is in accordance with the early Eocene rapid cooling of bedrock in the Qilian Shan revealed by in situ AFT and 40 Ar/ 39 Ar ages (Li, Zuza, et al, 2020; Qi et al., 2016; Zhuang et al., 2018).…”

“…Whether this Miocene event represents the first phase of deformation in the Cenozoic is ambiguous and controversial. Evidence of regional rock exhumation, the proximal accumulation of coarse clasts and the development of synsedimentary deformation in adjacent basins suggests that Cenozoic deformation has occurred in the Qilian Shan since the Eocene (Bush et al., 2016; Cheng et al., 2019; Dai et al., 2005; He et al., 2017, 2018, 2020; Ji et al., 2017; Qi et al., 2016; Yin et al., 2008; Zhuang et al., 2011, 2018). These two views are supported by different end‐member models of the deformation evolution of the TP.…”

Geomorphic expression of the Lenglong Ling area, eastern Qilian Shan, and its coupling relationship with the deep structures

“…Previous studies pointed out that the achievements on evolution of the Qilian Shan could be the keys to extend our understanding on the geodynamic process of the Tibetan Plateau (Bovet et al, 2009;Cheng et al, 2019;Duvall & Clark, 2010;Zuza et al, 2017;Zuza et al, 2018). Some studies have focused on both long and short-term landscape evolution of the Qilian Shan, from which, the results on the onset of mountain building (Dai et al, 2006;He et al, 2020;Lease, 2014;Lease, Burbank, Gehrels, Wang, & Yuan, 2007;Li et al, 2020), the extension model of the orogeny (Lease et al, 2007;Lease, Burbank, Zhang, Liu, & Yuan, 2012;Pang et al, 2019;Zheng et al, 2013;Zheng et al, 2017), and the erosion pattern under the influence of tectonics and climate (Hetzel et al, 2004;Hu, Fang, Zhao, & Darryl, 2015;Palumbo, Hetzel, Tao, & Li, 2010;Palumbo, Hetzel, Tao, & Li, 2011;Zheng, Clark, Zhang, Zheng, & Farley, 2010), have been achieved. In addition, the regional deep structures have been finely explored by means of the high-resolution deep seismic-reflection data (Gao et al, 2013;Guo et al, 2016;Huang, Xu, Gao, Guo, & Li, 2020;Wang et al, 2014) and the magnetotelluric imaging (Liang, Gao, Xue, & Han, 2020;Zhan et al, 2008;Zhao et al, 2005).…”

Intensified Late Miocene Deformation in the Northern Qaidam Basin, Northern Tibetan Plateau, Constrained by Apatite Fission-Track Thermochronology

“…Tibetan Plateau is an ideal region for studying the uplift of plateau and deformation of continents (Molnar et al, 1993;Yin and Harrison, 2000;Tapponnier et al, 2001;Royden et al, 2008;Wang et al, 2008;Fang et al, 2020). The North Qaidam-Qilian Shan fold-thrust belt (NQQB) comprises the northern Tibetan Plateau (Figure 1), intensely deformed during the Cenozoic as a result of the remote response to Indian-Asian plate collision (Fang et al, 2005(Fang et al, , 2007Yin et al, 2008;Zheng et al, 2010;Zhuang et al, 2011Zhuang et al, , 2018He et al, 2020He et al, , 2021. The evolution of Cenozoic deformation in the NQQB is thus crucial for understanding the growth of the Tibetan Plateau and the re-activation of ancient orogenic belts.…”

“…However, the starting time and the spatial-temporal migration of deformation in the NQQB in Cenozoic is still controversial. Many sedimentology and thermochronology records indicate the deformation in this region commenced at the middle-late Miocene (Zheng et al, 2010(Zheng et al, , 2017Wang et al, 2017Wang et al, , 2020An et al, 2018;Pang et al, 2019a;Yu et al, 2019a), while evidence for the Eocene deformation is well accepted (Yin et al, 2008;Zhuang et al, 2011Zhuang et al, , 2018Jian et al, 2018;Lin et al, 2019;Cheng et al, 2019;He et al, 2020He et al, , 2021. The development of deformation in the NQQB is proposed to from the south to north (Zhuang et al, 2011;Qi et al, 2016), from the center to the south and north synchronous (Zheng et al, 2017;Pang et al, 2019a), or out-of-sequence deformation (Li et al, 2020;He et al, 2021).…”