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

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 localit...

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Bibliographic Details
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
Description
Summary: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.

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