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1. Late Mesozoic−Cenozoic cooling history of the northeastern Tibetan Plateau and its foreland derived from low-temperature thermochronology

   https://doi.org/10.1130/B35879.1  

   Wu, Chen ; Zuza, Andrew V. ; Li, Jie ; Haproff, Peter J. ; Yin, An ; Chen, Xuanhua ; Ding, Lin ; Li, Bing ( March 2021 , GSA Bulletin)

   null (Ed.)

   The growth history and formation mechanisms of the Cenozoic Tibetan Plateau are the subject of an intense debate with important implications for understanding the kinematics and dynamics of large-scale intracontinental deformation. Better constraints on the uplift and deformation history across the northern plateau are necessary to address how the Tibetan Plateau was constructed. To this end, we present updated field observations coupled with low-temperature thermochronology from the Qaidam basin in the south to the Qilian Shan foreland in the north. Our results show that the region experienced a late Mesozoic cooling event that is interpreted as a result of tectonic deformation prior to the India-Asia collision. Our results also reveal the onset of renewed cooling in the Eocene in the Qilian Shan region along the northern margin of the Tibetan Plateau, which we interpret to indicate the timing of initial thrusting and plateau formation along the plateau margin. The interpreted Eocene thrusting in the Qilian Shan predates Cenozoic thrust belts to the south (e.g., the Eastern Kunlun Range), which supports out-of-sequence rather than northward-migrating thrust belt development. The early Cenozoic deformation exploited the south-dipping early Paleozoic Qilian suture zone as indicated by our field mapping and the existing geophysical data. In the Miocene, strike-slip faulting was initiated along segments of the older Paleozoic suture zones in northern Tibet, which led to the development of the Kunlun and Haiyuan left-slip transpressional systems. Late Miocene deformation and uplift of the Hexi corridor and Longshou Shan directly north of the Qilian Shan thrust belt represent the most recent phase of outward plateau growth. 

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2. Diachronous Growth of the Northern Tibetan Plateau Derived From Flexural Modeling

   https://doi.org/10.1029/2020GL092346  

   Wang, Lin ; Cheng, Feng ; Zuza, Andrew V. ; Jolivet, Marc ; Liu, Yiduo ; Guo, Zhaojie ; Li, Xiangzhong ; Zhang, Changhao ( April 2021 , Geophysical Research Letters)

   The early Cenozoic topography of the northern Tibetan plateau remains enigmatic because of the paucity of independent paleoelevation constraints. Long‐held views of northward propagating deformation imply a low Paleogene elevation, but this prediction is speculative. We apply flexural modeling to reconstructed Paleogene isopach data obtained from the Qaidam basin, which requires a larger topographic load in the Qilian Shan and a smaller load in the Eastern Kunlun Shan. Incorporating knowledge of proto‐Paratethys marine incursions in the Paleogene Qaidam basin, we infer a topographically low (0.4–1.0 km) Eastern Kunlun Shan and a higher (0.4–1.5 km) Qilian Shan during the Paleogene. This implied paleo‐relief contrasts with previous predictions and suggests more recently, Neogene surface uplift in the Eastern Kunlun Shan has been more significant than in Qilian Shan, highlighting diachronous growth of the northern Tibetan plateau. The low‐moderate paleoelevation implies a warmer and more humid climate in Northern Tibet during the Paleogene.

    

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3. Superposition of Cretaceous and Cenozoic deformation in northern Tibet: A far-field response to the tectonic evolution of the Tethyan orogenic system

   https://doi.org/10.1130/B35944.1  

   Wang, Ye ; Chen, Xuanhua ; Zhang, Yaoyao ; Yin, Zheng ; Zuza, Andrew V. ; Yin, An ; Wang, Yongchao ; Ding, Weicui ; Xu, Shenglin ; Zhang, Yiping ; et al ( June 2021 , GSA Bulletin)

   Abstract Although the Cenozoic Indo-Asian collision is largely responsible for the formation of the Tibetan plateau, the role of pre-Cenozoic structures in controlling the timing and development of Cenozoic deformation remains poorly understood. In this study we address this problem by conducting an integrated investigation in the northern foreland of the Tibetan plateau, north of the Qilian Shan-Nan Shan thrust belt, NW China. The work involves field mapping, U-Pb detrital-zircon dating of Cretaceous strata in the northern foreland of the Tibetan plateau, examination of growth-strata relationships, and construction and restoration of balanced cross sections. Our field mapping reveals multiple phases of deformation in the area since the Early Cretaceous, which was expressed by northwest-trending folding and northwest-striking thrusting that occurred in the early stages of the Early Cretaceous. The compressional event was followed immediately by extension and kinematically linked right-slip faulting in the later stage of the Early Cretaceous. The area underwent gentle northwest-trending folding since the late Miocene. We estimate the magnitude of the Early Cretaceous crustal shortening to be ~35%, which we interpret to have resulted from a far-field response to the collision between the Lhasa and the Qiangtang terranes in the south. We suggest that the subsequent extension in the Early Cretaceous was induced by orogenic collapse. U-Pb dating of detrital zircons, sourced from Lower Cretaceous sedimentary clasts from the north and the south, implies that the current foreland region of the Tibetan plateau was a topographic depression between two highland regions in the Early Cretaceous. Our work also shows that the Miocene strata in the foreland region of the northern Tibetan plateau was dominantly sourced from the north, which implies that the rise of the Qilian Shan did not impact the sediment dispersal in the current foreland region of the Tibetan plateau where this study was conducted. 

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

   https://doi.org/10.1029/2018TC005214  

   Cheng, Feng ; Garzione, Carmala N. ; Jolivet, Marc ; Guo, Zhaojie ; Zhang, Daowei ; Zhang, Changhao ; Zhang, Qiquan ( February 2019 , Tectonics)

   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.

    

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5. Growth of the southern Tian Shan-Pamir and its impact on central Asian climate

   https://doi.org/10.1130/B36471.1  

   Richter, Fabiana ; Pearson, Jozi ; Vilkas, Marius ; Heermance, Richard V. ; Garzione, Carmala N. ; Cecil, M. Robinson ; Jepson, Gilby ; Moe, Annelisa ; Xu, Jianhong ; Liu, Langtao ; et al ( October 2022 , GSA Bulletin)

   Uplift and amalgamation of the high-elevation (>3000 m) Tian Shan and Pamir ranges in Central Asia restricts westerly atmospheric flow and thereby limits moisture delivery to the leeward Taklimakan Desert in the Tarim Basin (<1500 m), the second largest modern sand dune desert on Earth. Although some research suggests that the hyper-arid conditions observed today in the Tarim Basin developed by ca. 25 Ma, stratigraphic evidence suggests the first erg system did not appear until 12.2 Ma. To address this controversy and to understand the tectonic influences on climate in Central Asia, we studied a continuous, 3800-m-thick stratigraphic section deposited from 15.1 to 0.9 Ma now exposed within the western Kepintagh fold-and-thrust belt in the southern Tian Shan foreland. We present new detrital zircon data (n = 839), new carbonate oxygen (δ18Oc) and carbon (δ13Cc) stable isotope compositions (n = 368), structural modeling, and stratigraphic observations, and combine these data with recently published magnetostratigraphy and regional studies to reconstruct the history of deposition, deformation, and climate change in the northwestern Tarim Basin. We find that basins along the southern (this study) and northern (i.e., Ili Basin) margins of the Tian Shan were likely receiving similar westerly precipitation by 15 Ma (δ18Oc = ∼−8‰) and had similar lacustrine-playa environments at ca. 13.5 Ma, despite differences in sedimentary provenance. At ca. 12 Ma, an erg desert formed adjacent to the southern Tian Shan in the northwestern Tarim Basin, coincident with a mid- to late Miocene phase of deformation and exhumation within both the Pamir and southern Tian Shan. Desertification at ca. 12 Ma was marked by a negative δ18Oc excursion from −7.8 ± 0.4‰ to −8.7 ± 0.7‰ in the southern Tian Shan foreland (this study), coeval with a negative δ18Oc excursion (∼−11 to −13‰) in the Tajik Basin, west of the Pamir. These data suggest that only after ca. 12 Ma did the Pamir-Tian Shan create a high-elevation barrier that effectively blocked westerly moisture, forming a rain shadow in the northwestern Tarim Basin. After 7 Ma, the southern Tian Shan foreland migrated southward as this region experienced widespread deformation. In our study area, rapid shortening and deformation above two frontal foreland faults initiated between 6.0 and 3.5 Ma resulted in positive δ13Cc excursions to values close to 0‰, which is interpreted to reflect exhumation in the Tian Shan and recycling of Paleozoic carbonates. Shortening led to isolation of the study site as a piggy-back basin by 3.5 Ma, when the sediment provenance was limited to the exhumed Paleozoic basement rocks of the Kepintagh fold belt. The abrupt sedimentologic and isotopic changes observed in the southern Tian Shan foreland appear to be decoupled from late Cenozoic global climate change and can be explained entirely by local tectonics. This study highlights how tectonics may overprint the more regional and global climate signals in active tectonic settings. 

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