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Associate Research Fellow Wang Weitao made significant progress in the study of the northeastern Tibetan Plateau

2017/10/18 15:26:12

India-Asia collision in the early Cenozoic and subsequent convergence of them have not only uplifted the Tibetan Plateau to create the “roof of the world”, but also resulted in a series of large-scale orogenic belts and sedimentary basins within Asia, which have a great influence on the tectonic framework, environmental evolution and climate change in western China. The Qilian Shan orogenic belt, located in the northeastern margin of the Tibetan Plateau, is bounded by the Qaidam Basin to the south and Hexi Corridor Basin to the north. It is the frontier and youngest component of the Tibetan Plateau that extends to the northeast (Figure 1). Sedimentary rocks in the Qilian Shan and its adjacent Cenozoic basins provide abundant recordings of tectonic deformation and climate change, which is one of the core factors that constrain the dynamic mechanism of the uplift and expansion of the Tibetan Plateau. It is also an important part for studies of the tectonic deformation, ecological environment evolution and natural disaster mitigation in mainland China.

Wang Weitao, an Associate Research Fellow of the Division of Neotectonics and Goemorpholog of Institute of Geology, CEA, and his collaborators focused on the Qilian Shan, the Qaidam Basin in the south and the Hexi Corridor Basin in the north, and studied the uplift of the mountains and the sedimentary evolution of those basins. Magnetic stratigraphy, biostratigraphy, and low-temperature thermochronological methods have indicated that the Qaidam Basin and the Hexi Corridor Basin began to deposit from the Late Oligocene (~25 Ma) and continued to the Late Pliocene or Quaternary. The detrital apatite fission track, zircon U-Pb age spectrum and paleocurrent direction analysis of the Qaidam Basin and the Hexi Corridor basin show that before 16-12 Ma, sediments in the two basins derived from the KunlunShan in the southern Qaidam Basin and Beishan in the north of the Hexi Corridor Basin. Since then the sediment source of the Qaidam Basin and the Hexi Corridor Basin changed significantly. The sediments within the two basins were mainly derived from the Qilian Shan, implying that the Qilian Shan began to rise rapidly under the control of the thrusting fault zones in the south and north during 16-12Ma.

Since late Miocene, the sedimentary rates of the Qaidam Basin and Hexi Corridor basin increased significantly. The sedimentary environment of the basin also changed from lake to braided river facies or alluvial fans (characterized by the emergence of thick layer “molasse”). Sediments in the basin near Qilian Shan were re-transported and deposited into areas far from Qilian Shan. The color of Cenozoic strata in the Hexi Corridor Basin also shifted rapidly from purple and orange to khaki at ~16Ma, indicating that the erosion rate in the source area increased and the weathering time was shortened.The above results reveal that the Qilian Shan experienced strong deformation and rapid uplift in the late Miocene, thus destroying the widely distributed basin systems which developed in the late Oligocene to early Miocene, and forming a unique basin-range tectonic and geomorphic pattern in the northeastern Tibetan Plateau.

The study of the formation process of Qilian Shan in the Cenozoic shows that the tectonic deformation and the uplift of mountains in the northeastern Tibetan Plateau obviously lagged behind the collision of the Indo-Asianplates at ~50 Ma, implying that the quasi synchronization rapid rise of the northeastern Tibetan Plateau in late Miocene in the range of thousands of kilometers may be closely related to the thickening and demolition of the lithospheric mantle in the northern Tibetan Plateau (Figure 3). This study can help understandings, in the field of Earth Science, of the tectonic deformation in western China and its impact on regional climate change.

Figure 1. Geomorphology and geological map of the Qilians Shan and adjacent regions in the northeastern Tibetan Plateau

Figure 2. Deformation and uplift of the Qilian Mountains in the Cenozoic

Figure 3. Sketch showing tectonic deformation of the northeastern Tibetan Plateau in Cenozoic

The above research results have been published in the following international journals:

Nature Communications (Wang, W., Zheng, W., Zhang, P., Li, Q., Eric, K., Yuan, D., Zheng, D., Liu, C., Wang, Z., Zhang, H., Pang, J., 2017. Expansion of the Tibetan Plateau during the Neogene. Nature Communications, 8, 15887).

Lithosphere (Zheng, D., Wang, W., Wan, J., Yuan, D., Liu, C., Zheng, W., Zhang, H., Pang, J., Zhang, P., 2017. Progressive northward growth of the northern Qilian Shan-Hexi Corridor (northeastern Tibet) during the Cenozoic. Lithosphere, 9: 408-416.)

Journal of Geophysical Research: Solid Earth (Wang, W., Zhang, P., Pang, J., Carmala,G., Zhang, H., Liu, C., Zheng, D., Zheng, W., Yu, J., 2016.The Cenozoic growth of the Qilian Shan in the northeastern Tibetan Plateau: A sedimentary archive from the Jiuxi Basin. JGR-Solid earth, 121: 2235-2257).

Scientific Reports (Wang, W., P. Zhang, J. Yu, Y. Wang, D. Zheng, W. Zheng, H. Zhang and J. Pang. 2016. Constrains on mountain building in northeast Tibet: Detrital zircon records from synorogenic deposits in the Yumen Basin. Scientific Reports, 6: 27604.)

Scientific Reports (Wang, W., Zhang, P., Zheng, W., Zheng, D., Liu, C., Xu, H., Zhang, H., Yu, J., Pang, J., 2016. Uplift-driven sediment redness decrease at ~16.5?Ma in the Yumen Basin along the northeastern Tibetan Plateau. Scientific Reports, 6: 29568.)


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