Luminescence age and palaeoenvironmental implications of a late Pleistocene ground wedge on the northeastern Tibetan Plateau

• Published in: Permafrost and Periglacial Processes
• Main Authors: Porter, SC, Singhvi, A, An, ZS, Lai, ZP
• Format: Article in Journal/Newspaper
• Language: English
• Published: JOHN WILEY & SONS LTD 2001
• Subjects: ice-wedge cast; Pleistocene permafrost; palaeoenvironment; Tibet; Physical Geography; Geology; WESTERN CHINA; QAIDAM BASIN; LAKE; PERMAFROST; EVOLUTION; QINGHAI; LOESS; Geography; Physical; Arctic; Bajada; Basin Lake; permafrost; Permafrost and Periglacial Processes
• Online Access: http://ir.ieecas.cn/handle/361006/11926; https://doi.org/10.1002/ppp.386

A periglacial ground wedge in bajada gravel near the northern base of the Qinghai Nan Shan underlies loess of late- and postglacial age. The composition and structure of the wedge fill are consistent with an ice-wedge origin, implying former permafrost and relatively moist conditions at this locality. A luminescence date of 15,100 +/- 1600 years from the wedge fill marks the end of ice-wedge activity, which is inferred to have been during the last glaciation. The present mean annual air temperature (MAAT) (-0.7 degreesC) is too high to produce frost cracking and ice-wedge formation, but snowline depression of ca. 700-800 m in the adjacent mountains is consistent with a reduction in MAAT of at least 3.8 degreesC during the last glacial maximum. Such a temperature depression would reduce MAAT to values equivalent to Arctic regions now experiencing active ice-wedge growth. The absence of loess of full-glacial age and the presence of a weakly developed palaeosol atop the bajada gravel imply a stable, cold land surface. Qinghai Lake, although reduced in size at that time, likely raised local humidity to levels that favoured ice-wedge growth in this low-altitude sector (ca. 3000-3400 m) of the Tibetan Plateau. Copyright (C) 2001 John Wiley & Sons, Ltd.