Initial Deformation of the Northern Tibetan Plateau: Insights From Deposition of the Lulehe Formation in the Qaidam Basin

Abstract

The Paleogene Lulehe Formation marks the onset of deposition in the Qaidam basin and preserves evidence of the initial topographic growth of northern Tibet. However, limited outcrops impede understanding of the sedimentary features of the Lulehe Formation as well as the tectonic relationship between the basin and surrounding topography. To fill this gap, we investigated core samples along the basin margin and conducted flexural modeling to estimate the topographic load of the Qilian Shan and Eastern Kunlun Shan during the deposition of the Lulehe Formation. Core samples reveal that the Lulehe Formation mainly consists of distal fluvial to marginal lacustrine deposits and proximal fluvial deposits along the southern margin of the basin while characterized by proximal alluvial fan deposits along the northern margin of the basin. Together with evidence for faulting shown on the seismic profiles, we infer that simultaneous deformation within the Qilian Shan and Altyn Tagh Shan during the Paleogene resulted in accumulation of coarse detrital deposits in the northwestern and northeastern Qaidam basin. The simultaneous deformation within the Altyn Tagh Shan and Qilian Shan since the Paleogene supports the idea that deformation in these two regions is kinematically linked. One-and two-load beam flexural modeling indicates that the topographic load generated by both the Eastern Kunlun Shan and the Qilian Shan is responsible for the subsidence of the Qaidam basin during deposition of the Lulehe Formation. Our results highlight the initial relative high topography in the northern Tibetan plateau during the early Cenozoic.

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

“…Compared with the widespread middle Miocene deformation across the entire Qilian Shan, the early Cenozoic deformation is just reported south of the Qaidam Basin (e.g., Clark et al, ; Jolivet et al, , ; D. Liu, Li, et al, ; Mock et al, ; F. Wang, Shi, et al, ; Y. Wang et al, ; Yin et al, ), the northern Qaidam Basin (e.g., F. Cheng et al, ; He et al, ; Jolivet et al, ; Lu et al, ; Yin et al, ; Zhuang et al, ), and parts of the Qilian Shan, such as the Xining‐Lanzhou Basin (Dupont‐Nivet et al, ; Dai et al, ; J. Zhang et al, ; Wang, Zhang, Liu, et al, ), western Qinling (Clark et al, ; Duvall et al, ), and the central‐northern Qilian Shan (e.g., Qi et al, ; He et al, ; Figure b). The Paleocene‐Eocene and widespread middle Miocene deformation suggest that the crustal shortening has extended into the northern Tibetan Plateau to reactive preexisting weaknesses shortly after the India‐Eurasia collision, followed by a phase of extensive crustal shortening across the Qilian Shan since the middle Miocene.…”

“…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, ). While Lu et al () suggest that Bush et al () may misidentify the underlying Cretaceous Quanyagou formation as the lower part of the Lulehe formation such that produce improper conclusions, they concluded that the Lulehe formation is characterized by proximal alluvial fan deposits that originated from the northern Qaidam Basin and the southern Qilian Shan based on evidence of sedimentology, facies analysis, and seismic reflection profiles (e.g., F. Cheng et al, ; Lu et al, ; Yin et al, ). Cheng et al () suggest that if both the traditional (~50 Ma) and younger (~25.5 Ma) age models are correct, the Qaidam Basin may experience diachronous basin‐fill process and the lithostratigraphic units throughout the basin are time transgressive.…”

“…Compared with the widespread middle Miocene deformation across the entire Qilian Shan, the early Cenozoic deformation is just reported south of the Qaidam Basin (e.g., Clark et al, 2010;Jolivet et al, 1999Jolivet et al, , 2001Mock et al, 1999;F. Wang, Shi, et al, 2017;Yin et al, 2002), the northern Qaidam Basin (e.g., F. Cheng et al, 2019;He et al, 2018;Jolivet et al, 2001;Lu et al, 2018;Yin et al, 2008;Zhuang et al, 2011), and parts of the Qilian Shan, such as the Xining-Lanzhou Basin (Dupont-Nivet et al, 2004;Dai et al, 2006;J. Zhang et al, 2015;, western Qinling Duvall et al, 2011), and the central-northern Qilian Shan (e.g., Qi et al, 2016;He et al, 2017; Figure 9b).…”

Anisotropic Tomography Beneath Northeast Tibet: Evidence for Regional Crustal Flow

“…At 30 km depth (Figure 4), the low‐V zones beneath EKQB‐WQFZ seem to be limited by the Kunlun fault to the south. The Qilian block is kinematically linked with the Altyn Tagh Shan in the west for simultaneous deformation since the Paleogene (Cheng et al, 2019). Considering the seismic velocity results near the Kunlun fault (Sun et al, 2019) and the seismic anisotropy near the north Qinling fault (Hu et al, 2020), we deem that the EKQB‐WQFZ may act as a conjugate tectonic corridor to guide the middle to lower crustal flow possibly from the central Tibetan Plateau (see the thick orange arrows in Figure 7).…”

Provenance Analysis of the Paleogene Strata in the Northern Qaidam Basin, China: Evidences from Sediment Distribution, Heavy Mineral Assemblages and Detrital Zircon U‒Pb Geochronology

“…[20]). (c) Detailed geological map of the study area in the northern Qaidam Basin (modified from Cheng et al 2019a [21]).…”