Early Cretaceous Thrust and Nappe Tectonics in North Qilian Shan, Northern Tibetan Plateau: Evidence from Field Mapping, Geochronology, and Deep Structural Analysis

Abstract

The North Qilian Shan fold and thrust belt, located at the northern Tibetan Plateau and southern margin of the Hexi Corridor, is a key tectonic unit to decode the formation and expansion of the plateau. Previous studies emphasize the Cenozoic deformation due to the far‐field response to the Indo‐Asian collision, but the Mesozoic deformations are poorly constrained in this area. We conducted detailed field mapping, structural analysis, geochronology, and structural interpretation of deep seismic reflectional profiling and magnetotelluric (MT) sounding, to address the superposed results of the Mesozoic and Cenozoic deformation. The results recognized the North Qilian thrust and nappe system (NQTS), the root and the frontal belt are the North Qilian Thrust (NQT), and the Yumu Shan Klippe (YK), respectively. The middle belt is located between the NQT and the YK. Monzonitic granite zircon U‐Pb dating from the middle belt yields an age of ca. 415 Ma, which is similar to south NQT. The thrusting displacement is estimated at ca. 48 km by structural interpretation of deep profiles. The timing is constrained in the early stage of the Early Cretaceous by the formation of simultaneous growth strata. We suggest that the NQTS has resulted from the far‐field effect of the Lhasa‐Qiangtang collision, and the Yumu Shan is uplifted by the superposed Cenozoic deformation.

The Late Mesozoic Intracontinental contraction–Extension Transition in the Beishan Fold‐Thrust Belt, Central Asia: Constraints From Structural Analysis and Apatite (U–Th)/He Thermochronology

“…(2022), Han et al. (2023), and this study. (a) Late Middle Jurassic–Early Cretaceous thrusting, nappe emplacement, crustal shortening, and foreland‐like basin development in the Beishan fold‐thrust belt to the NE Tibetan region.…”

“…The structural and kinematic evolution of the late Mesozoic Beishan fold‐thrust belt, which was minimally overprinted in the Cenozoic, has important implication for understanding the pre‐Cenozoic uplift and deformation history of the NE Tibetan Plateau. For example, Cenozoic deformation strongly overprinted the earlier tectonic history of the Qilian Shan (Jolivet et al., 2001; B. Li et al., 2019, 2021; Yin et al., 2008; Zuza et al., 2016, 2018), but there is evidence for Early Cretaceous contractional deformation (X. H. Chen et al., 2019a, 2019b; Han et al., 2023; Y. Wang et al., 2022; Wu et al., 2011) that temporally and spatially correlates with the development of the Beishan fold‐thrust belt (Figures 14 and 15a). The uplifted Beishan Range and Qilian Shan provided the main sources of Lower Cretaceous proximal deposits in the Yumen Basin (Cheng et al., 2019) (Figure 15a).…”

“…Li et al, 2019B. Li et al, , 2021Yin et al, 2008;Zuza et al, 2016Zuza et al, , 2018, but there is evidence for Early Cretaceous contractional deformation (X. H. Chen et al, 2019aChen et al, , 2019bHan et al, 2023;Y. Wang et al, 2022;Wu et al, 2011) that temporally and spatially correlates with the development of the Beishan fold-thrust belt (Figures 14 and 15a).…”

Crustal‐Scale Duplex Development During Accretion of the Jiuxi Foreland Basin, North Qilian Shan

“…Our structural analysis also indicates that there was a compressional event prior to the Late Cenozoic North Qilian uplift, which led to the initial tilting and duplication of Devonian to Jurassic units in our research area. Previous studies have identified three compressional events that could explain this deformation: a Late Triassic to Early Jurassic event and an Early Cretaceous event (Cheng et al, 2019;Han et al, 2023;Jolivet et al, 2001;Tong et al, 2020;, or a possible Eocene-Oligocene early event that defined the early extent of the Tibetan Plateau (Clark, 2012;Wu et al, 2021;Zuza et al, 2019Zuza et al, , 2020. The unconformity between Oligocene and Devonian to Jurassic units supports that this event took place prior to the Oligocene; omission of Jurassic units in Yaoquan and Dahuanggou areas may favor a Late Triassic to Early Jurassic age for this event.…”

“…Wang et al, 2018). Later, during the Early Cretaceous, recent studies on sedimentology, thermochronology, and seismic reflection data suggest another compressional event characterized by NW-striking thrusting and folding (Han et al, 2023;, quickly followed by N-S extension (S. Chen et al, 2014;Cheng et al, 2019;Jolivet et al, 2001;Pan et al, 2013;Vincent & Allen, 1999;Yin et al, 2008;Zuza et al, 2016). These Cretaceous events are interpreted as a result of collision of the Lhasa/Qiangtang terrane and subsequent orogenic collapse.…”