THE SAND WEDGE AND MIRABILITE OFTHE LAST ICE AGE AND THEIR PALEOCLIMATICSIGNIFICANCE IN HEXI CORRIDOR

Sand wedge is formed under the conditions of coldclimate, and is an important basis for reconstructingpaleoenvironment (LI et al., 1990; WANG, 1991 ). Ithas been reported constantly over the last 20 years inthe Qinghai-Xizang (Tibet) Plateau (GUO, 1979; CUl,1983; XU et al., 1984; LIANG et al.,, 1984; PAN etal., 199 ) and North China (YANG et al., 1983; DONGet al., 1985) and Northeast China (GUO et al.,1981 ). We also found fossil sand wedge groups formedin the end of the Late P…

The sand wedge and mirabilite of the last ice age and their paleoclimatic significance in Hexi Corridor

The sand wedges in Hexi Corridor occur in the alluvial gravel stratum of bajada and high terraces. The ¹⁴C ages of eolian sand in sand wedges prove that they formed during the Last Ice Age, with the mean annual air temperature about − 5.6°C. The common ¹⁴C and AMS ¹⁴C dating ages of terrestrial branch relicts in Huahai clay-mirabilite interlayer are (11 600 ± 280) a B. P. and (1118 ± 54) a B. P. respectively, proving that the mirabilite formed at the cold episode of the Last Glacial Maximum(LGM) and Younger Dryers(YD) in Huahai Lake. It is pointed out that the mean annual air temperature in Hexi Corridor during LGM was about −3°C – −7°C, 11°C – 15°C lower than that of present, and that during YD was about 0°C – 2°C, 6°C – 8°C lower than at present. This decreasing temperature values are generally coincident with those inferred by pollen, sand wedge and ice core in the northern China, and also with the research on temperature-falling amplitude of middle and high latitude on the Northern Hemisphere recently. Foundation item : Under the auspices of National Natural Science Foundation of China(NO. 49731010)and Chinese National Key Project for Basic Research (G1999043501). Biography: HU Gang(1976 – ), male, a native of Binzhou, Shandong Province, master. His research interests include paleolake, paleoenvironment and regional geography.