The delineation of the southern boundary of the latitudinal permafrost in the north of China in the period of late Pleistocene, i.e. the last glaciation maximum (LGM), has been hampered for two reasons. Firstly, previ...The delineation of the southern boundary of the latitudinal permafrost in the north of China in the period of late Pleistocene, i.e. the last glaciation maximum (LGM), has been hampered for two reasons. Firstly, previous studies were limited to the eastern part of the north of China, and,secondly, the ages of the permafrost had not been determined systematically. In this paper, we suggest that the southern boundary of the high latitudinal permafrost in the north ofChina is bounded by approximately 38—40N (eastern part) and 37—39N (western part) lines of latitude based on ourinterpretation of periglacial phenomena and their implica-tion to the environment during the late Pleistocene, and this southern boundary is plotted for the first time. Also, we re-construct the migration of the southern latitudinal perma-frost boundary and the environment after LGM. It is pro-posed that two cold stages occurred in the LGM at 26 kaBP and 23—13 kaBP, when the annual mean temperature was 8—12℃ lower than at present.展开更多
Wedge-like structures filled with silty sand penetrate Quaternary fluvial and aeolian sediments and, in places, Tertiary bedrock on the Ordos Plateau, North China. The wedges reflect thermal contraction cracking of ei...Wedge-like structures filled with silty sand penetrate Quaternary fluvial and aeolian sediments and, in places, Tertiary bedrock on the Ordos Plateau, North China. The wedges reflect thermal contraction cracking of either permafrost or seasonal frost during the Late Pleistocene and early Holocene. Wedges of about 1 m in depth form polygonal nets of 2-3 m in diameter(type B). They contrast with wedges of 3-4 m in depth that form polygons of 10-15 m in diameter(type A).This review focuses upon the highly variable size of the inferred polygon nets and discusses the problem of differentiating between seasonally and perennially frozen ground, or between seasonal frost and permafrost.展开更多
文摘The delineation of the southern boundary of the latitudinal permafrost in the north of China in the period of late Pleistocene, i.e. the last glaciation maximum (LGM), has been hampered for two reasons. Firstly, previous studies were limited to the eastern part of the north of China, and,secondly, the ages of the permafrost had not been determined systematically. In this paper, we suggest that the southern boundary of the high latitudinal permafrost in the north ofChina is bounded by approximately 38—40N (eastern part) and 37—39N (western part) lines of latitude based on ourinterpretation of periglacial phenomena and their implica-tion to the environment during the late Pleistocene, and this southern boundary is plotted for the first time. Also, we re-construct the migration of the southern latitudinal perma-frost boundary and the environment after LGM. It is pro-posed that two cold stages occurred in the LGM at 26 kaBP and 23—13 kaBP, when the annual mean temperature was 8—12℃ lower than at present.
基金part of a project investigating the nature and extent of paleo-permafrost in West China led by Professor Huijun Jin with the State Key Laboratory of Frozen Soils Engineering (SKLFSE), Northwest Institute of Eco-Environment and Resources (NIEER), Chinese Academy of Sciences (CAS), Lanzhou, under the auspices of National Natural Science Foundation of China (NSFC) (Grant No.41811530093)Russian Federation Bureau of Research (RFBR Grant No.18-5553054) on Formation, modern state of Pleistocene cryogenic deposits in Eastern Asia, and forecast of their dynamics in relation to the ongoing climatic variations+1 种基金Key Programs of the International Cooperation Department of the Chinese Academy of Sciences (CAS) on "Changing permafrost in China, Russia and Mongolia and its impacts on key engineered infrastructures"CAS Strategic Pilot Science and Technology Project (Grant No.XDA05120302) "Permafrost in China during the Holocene Megathermal Period and Last Glaciation Maximum"。
文摘Wedge-like structures filled with silty sand penetrate Quaternary fluvial and aeolian sediments and, in places, Tertiary bedrock on the Ordos Plateau, North China. The wedges reflect thermal contraction cracking of either permafrost or seasonal frost during the Late Pleistocene and early Holocene. Wedges of about 1 m in depth form polygonal nets of 2-3 m in diameter(type B). They contrast with wedges of 3-4 m in depth that form polygons of 10-15 m in diameter(type A).This review focuses upon the highly variable size of the inferred polygon nets and discusses the problem of differentiating between seasonally and perennially frozen ground, or between seasonal frost and permafrost.
