PERIGLACIAL-AEOLIAN POLYGONAL SURFACE STRUCTURES
IN THE TIBETAN PLATEAU
A.A. Galanin1, I.V. Klimova1, I.I. Khristoforov1, Q. Wu2, Zh. Ze2
1Melnikov Institute of Permafrost, Siberian Branch of the Russian Academy of Sciences, Yakutsk, Russia
2Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China
Keywords: Polygonal surface pattern, dune, sand wedge, ice wedge, desert pavement, ventifact, periglacial-aeolian features, frost cracks, high-altitude permafrost, Tibetan Plateau
Abstract
The surface pattern of permafrost area in the Tibetan Plateau, with 15-20 m polygons, resembles the patterned ground of the Arctic periglacial loess plains in northeastern Eurasia and North America. However, unlike the Arctic plains, it consists of semi-stabilized modern sand dunes, up to 2.5-3.0 m high, and U-shaped epigenetic ice wedge casts inherited from an ancient polygonal network on the surface of a 10-12-m terrace of the Yangtze River. The polygonal dunes and the U-shaped sand wedges were studied in the Yangtze headwaters in the vicinity of the high-altitude research station Bei-Lu-Xe. The polygons have desert pavement floors with ventifacts, composed of Late Pleistocene alluvial gravel and debris. The dunes and wedges consist of well sorted quartz-carbonate sand with an average grains size of 2.0-2.2 mm. Ground Penetrating Radar surveys in the area revealed the permafrost table at depths varying from 2 m to 4 m below the dunes. The polygonal dunes may have formed by biogenic-aeolian deposition over an ancient system of ice wedges.
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