Loess in the Tian Shan and its implications for the development of the Gurbantunggut Desert and drying of northern Xinjiang |
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Authors: | Xiaomin Fang Zhentao Shi Shengli Yang Maodu Yan Jijun Li Ping’an Jiang |
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Institution: | (1) National Laboratory of Western China’s Environmental Systems of Ministry of Education of China & Department of Geography, Lanzhou University, 730000 Lanzhou, China;(2) State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, 710054 Xi’an, China;(3) Institute of Cold and Arid Region & Environment and Engineering of Chinese Academy of Sciences, 730000 Lanzhou, China;(4) Department of Geological Sciences, University of Michigan, 48103 Ann Arbor, MI, USA;(5) School of Agriculture, Xinjiang Agriculture University, 830000 Urumqi, China |
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Abstract: | Eolian loess is widely distributed on the various geomorphic surfaces between 700–2400 m a.s.l. on the northern slope of the
Tian Shan. It is formed in a synchronous manner with dust transported from the Gurbantunggut Desert in the Junggar Basin.
The thickest section of loess was found in the Shawan and Shihezi regions. Paleomagnetic and climatic proxy analyses of over
71 m of a loess-paleosol sequence on the highest terrace of the Qingshui He (River) in the Shawan show that the paleomagnetic
Bruhues/Matuyama (B/M) boundary lies at the bottom of paleosol S8, at a depth of 69.5 m, and the bottom of the sequence was
estimated to be ∼0.8 Ma. This implies that the extremely dry climatic conditions in the Junggar Basin and the initial Gurbantunggut
Desert were present at least by 0.8 Ma. High-resolution grain size series demonstrate that this area and desert expansion
experienced two dramatic periods of desert expansions that occurred at ∼0.65 Ma and 0.5 Ma, respectively; and the subsequent
continuous enhancement led to the environment presently observed. This tremendous environmental effect, caused by large-scale
expansion of the desert and arid region of inner Asia, might be an important driving force for the global temperature drop
that occurred in the mid-Pleistocene. |
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Keywords: | Tian Shan loess Gurbantunggut Desert aridification global change |
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