Origin of a bouldery diamicton, Kunlun pass, Qinghai-Xizang plateau, People's Republic of China: Gelifluction deposit or rock glacier?

On the west side of the military road to Tibet in the Kunlun Shan, a major body of diamicton is moving slowly downslope from the ridge crest at 4800m in a northerly and easterly direction. The material is derived from Middle Pleistocene till deposits and the underlying Pliocene alluvial gravels. Mor...

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Bibliographic Details
Main Authors: Harris, SA, Cui, ZJ, Cheng, GD
Other Authors: Harris, SA (reprint author), Univ Calgary, Dept Geog, 2500 Univ Dr NW, Calgary, AB T2N 1N4, Canada., Univ Calgary, Dept Geog, Calgary, AB T2N 1N4, Canada., Peking Univ, Dept Geog, Beijing 100871, Peoples R China., Acad Sinica, Lanzhou Inst Glaciol & Geocryol, Lanzhou 73000, Gansu Province, Peoples R China., Univ Calgary, Dept Geog, 2500 Univ Dr NW, Calgary, AB T2N 1N4, Canada.
Format: Journal/Newspaper
Language:English
Published: earth surface processes and landforms 1998
Subjects:
Ice
Online Access:https://hdl.handle.net/20.500.11897/215718
https://doi.org/10.1002/(SICI)1096-9837(199810)23:10<943::AID-ESP913>3.0.CO;2-7
Description
Summary:On the west side of the military road to Tibet in the Kunlun Shan, a major body of diamicton is moving slowly downslope from the ridge crest at 4800m in a northerly and easterly direction. The material is derived from Middle Pleistocene till deposits and the underlying Pliocene alluvial gravels. More than 10 per cent of the material is composed of boulders longer than 2m, 45 per cent has long axes between 0.5 and 2 m, while the matrix is a poorly sorted sandy loam. The mean annual air temperature is -7 degrees C to -5 degrees C and the mean annual precipitation it under 300 mm a(-1). The diamicton lacks a vegetation cover, in contrast to meadow tundra on the surrounding slopes. The diamicton mantles the north slope of the ridge, but splits into at least 16 separate tongues which are moving down fluvially graded valleys. The average slope of the landform is about 19 degrees, while the mean slope of the fronts of the tongues is 21 degrees. With one exception, the slope of the fronts does not exceed 25 degrees, unlike true rock glaciers. The diamicton is up to 40m thick in valley 4, The active layer was 12 to 30 cm deep in July at 4780m, increasing to 1.5 to 2m at about 4650m. Ice contents in the permafrost may reach 57 per cent but 30 per cent is more usual. The larger boulders act as braking blocks on the upper slopes of the landform and are frozen into the permafrost. The lower parts of the landform move at under 3 cma(-1) whereas the fine-grained material in the active layer moves past the braking blocks on the upper slopes at up to 30 cm a(-1). There is no direct evidence for flowage of the icy diamicton forming the deposit. It is therefore best referred to as a gelifluction slope deposit, and is the longest and most spectacular of such deposits described so far in the world. (C) 1998 John Wiley & Sons, Ltd. Geography, Physical Geosciences, Multidisciplinary SCI(E) 8 ARTICLE 10 943-952 23