Discovery of a large area of ice-wedge networks in Ordos: Implications for the southern boundary of permafrost in the north of China as well as for the environment in the latest 20 kaBP

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 of China is bounded by approximately 38-40degreesN (eastern part) and 37-39degreesN (western part) lines of latitude based on our interpretation of periglacial phenomena and their implication to the environment during the late Pleistocene, and this southern boundary is plotted for the first time. Also, we reconstruct the migration of the southern latitudinal permafrost boundary and the environment after LGM. It is proposed that two cold stages occurred in the LGM at 26 kaBP and 23-13 kaBP, when the annual mean temperature was 8-12degreesC lower than at present.