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Discovery of Sand Wedge/Ice Wedge Cast of Last Glaciation in Wuhai Basin and Its Paleoclimatic Significance(PDF)


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Discovery of Sand Wedge/Ice Wedge Cast of Last Glaciation in Wuhai Basin and Its Paleoclimatic Significance
LI Da-wei LI De-wen SHEN Xiao-ming SUN Chang-bin KANG Yan-rui ZHANG Ya-jiao
Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China
periglacial phenomenon sand wedge ice wedge cast paleoclimate last glaciation OSL dating grain size analysis Wuhai Basin
The periglacial phenomena like sand wedge/ice wedge cast have been discovered with the paleoclimatic and paleoenvironmental significances in the northern China. But most of them are dated to the late stage of last glaciation. The periglacial phenomenon discovered firstly in Wuhai Basin was reported. Characteristics of morphology, grain size analysis of filler and OSL dating were applied to identify the origin and age, including that the early primary sand wedge encompasses a set of structures almost parallel with the wall around it, and the late ice wedge cast (including its formation, melt and fill) is superposed on the sand wedge. The ice wedge cuts through and damages the structure of the primary sand wedge, and the wedge is characterized with bend and irregular boundary as a whole. OSL dating results show that the primary sand wedge is formed during the early last glaciation ((62.69±6.81)-(66.45±7.08)ka B.P., MIS4), and may go down to MIS3b; the filler of ice wedge cast is formed during the Middle Holocene ((5.95±0.61)-(6.62±0.73)ka B.P.). Because the filling of ice wedge cast is later than the formation of ice wedge, it is probably that the formation of ice wedge is during the late last glaciation. Based on the formation process of sand wedge/ice wedge cast and their environmental requirement, it is estimated that the annual mean temperature has dropped 12.1 ℃-13.6 ℃ from the formation of sand and ice wedges to present, and the annual precipitation is of no significant difference from the formation of sand wedge (the early stage of last glaciation) to present. The discovery of sand wedge/ice wedge cast in Wuhai Basin could provide a basis for studying the distribution of permafrost and the paleoclimate during the last glaciation (especially the early stage) in the northern China.




Last Update: 2016-06-02