Neogene Expansion of the Qilian Shan, North Tibet: Implications for the Dynamic Evolution of the Tibetan Plateau

Abstract

The Qilian Shan, at the northeastern frontier of the Tibetan Plateau, is a key area for studying the expansion mechanism of the Tibetan Plateau. Although previous thermochronology and paleomagnetic studies indicate Neogene northward expansion of the northern Qilian Shan, there is a distinct temporal gap in knowledge relative to the tectonic history of the southern Qilian Shan. This has hindered a complete understanding of the Cenozoic deformation pattern of the entire Qilian Shan. To study the growth history of the southern Qilian Shan, apatite fission track (AFT) data have been acquired from Zongwulong Shan and the Huaitoutala section. AFT thermal history modeling from the former shows a rapid cooling episode occurred at~18-11 Ma, which is interpreted as marking the onset of intensive exhumation in the southern Qilian Shan. Within the Huaitoutala section, detrital grain up-section shows progressively decreasing peak AFT ages followed by an age increase from midsection, implying that a sediment-recycling event occurred at approximately 7 ± 2 Ma. Together with a shift in paleocurrent directions, this change marks the onset of Late Miocene deformation of the northern Qaidam Basin. Combined with previous studies on the deformation time of the Qilian Shan, our findings suggest that both the northern and southern Qilian Shan region grew outward synchronously in opposite directions during the Neogene. This resulted in the formation of a flower structure, which had an important impact on the deformation pattern of north Tibet. The synchronous outward expansion may have been triggered by the removal of mantle beneath north Tibet.

Miocene Range Growth Along the Altyn Tagh Fault: Insights From Apatite Fission Track and (U‐Th)/He Thermochronometry in the Western Danghenan Shan, China

“…However, recent published magnetostratigraphy and mammalian biostratigraphy refine the onset of basin fill in the Qaidam Basin to ~25.5 Ma and reveal that the detritus shed from the southern Qilian Shan occurred at ~12 Ma, suggesting that the deformation in the southern Qilian Shan is significantly later than previously estimated (W. Wang, Zheng, Zhang, et al, ). It is consistent with thermochronological data along the mountain ranges in the southern margin of the Qilian Shan, which has undergone a phase of accelerated exhumation since the early‐middle Miocene (Pang et al, ; Zhuang et al, ). It is also supported by provenance analyses for the Qaidam Basin, which indicate that early Cenozoic sediments in the northern Qaidam Basin were shed from the Kunlun Shan rather than the southern Qilian Shan, and provenance change occurred during early‐middle Miocene (Bush et al, ; W. Wang, Zheng, Zhang, et al, ).…”

“…Our new thermochronological data combined with published data in the western Danghenan Shan indicate a period of accelerated deformation since the middle Miocene in the southwestern portion of the Qilian Shan. The accelerated deformation in the middle Miocene is observed not only in the southwestern portion of the Qilian Shan but also throughout the rest of the Qilian Shan: (1) Thermochronological data indicate that the northern margin of the Qilian Shan has undergone accelerated exhumation since ~10 Ma (George et al, ; B. Li et al, ; Zheng et al, , ; Zhuang et al, ); (2) a shift in provenance in the Hexi Corridor from the Bei Shan to the north to the northern Qilian Shan to the south, and facies change in the Hexi Corridor suggest that the deformation that created the high topography of the northern Qilian Shan began at the middle Miocene (Bovet et al, ; Wang, Zhang, Pang, et al, ); (3) rapid exhumation of the central Qilian Shan is reported to have occurred since the middle Miocene (Duvall et al, ; D. Yuan et al, , ; Yu et al, ; Zheng et al, ); (4) accelerated exhumation and depositional rates, sediment coarsening, development of growth strata, and climate change attributed to mountain building in the middle Miocene are widespread across the eastern portion of the Qilian Shan east of the Qinghai Lake, such as the Linxia, Xunhua, Guide, and Gonghe basins (see a review in Lease, ); and (5) new thermochronological data and magnetostratigraphy in the southern margin of the Qilian Shan and northern Qaidam Basin suggest that the region has experienced rapid exhumation since the middle Miocene (Fang et al, ; Pang et al, ; W. Wang, Zheng, Zhang, et al, ; Zhuang et al, ; Figure a).…”

“…Yuan et al (); 33—W. Yuan et al (); 34—Fang et al (); 35—Pang et al (); 36—W. Wang, Zheng, Zhang, et al (); 37—Jolivet et al, ; 38—Yin et al (); 39—D.…”

Cenozoic Exhumation of the Qilian Shan in the Northeastern Tibetan Plateau: Evidence From Low‐Temperature Thermochronology

“…Topographic map of the northeastern margin of the Tibetan plateau showing major faults and their Cenozoic activity ages based on published sedimentary (magnetostratigraphy) and thermochronologic studies (see main text for details). The ages were derived from reference: 1: Zheng et al (2006); 2: Lin et al (2011); 3: Wang et al (2011); 4: Wang et al (2013); 5: Lei et al (2018); 6: Yan et al (2006); 7: Liu, Wang, et al (2016); 8: Yu, Pang, et al (2019); 9: Fang et al (2013); 10: Zheng et al (2010); 11: Wang, Zhang, Pang, et al (2016); 12: Wang, Zhang, Yu, et al (2016); 13: Pang et al (2019); 14: Yin, Dang, Zhang, et al (2008); 15: Zhuang et al (2018); 16: Yu, Zheng, et al (2019); and 17: Wang et al (2003). Inset figure outlines the location of the study area within the northeastern margin of the Tibetan plateau.…”

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

“…(2018), Li et al. (2019), Pang, Yu, Zheng, Wang, Ma, et al (2019), Pang, Yu, Zheng, Wang, Zhang, et al (2019), and Yu, Zheng, et al (2019), Yu, Pang, et al (2019). AFT = apatite fission track.…”