河西走廊末次冰期芒硝和砂楔与古气候重建

芒硝和砂楔是冷干气候环境的典型标志。河西走廊砂楔主要形成在晚更新世冲洪积砾石层中 ,楔体内充填的风成砂14 C年龄证明其是末次冰期的产物 ,古砂楔所对应的年均气温为- 5 6℃左右。芒硝主要分布在内陆河终端的盐湖中 ,花海芒硝矿粘土夹层中的陆生树枝残条普通14 C和AMS14 C年龄分别为 (116 0 0± 2 80 )aB .P .和 (11181± 54)aB .P .,证明芒硝层为末次盛冰期 (LGM )和新仙女木期 (YD)异常冷干气候的产物。计算表明 ,该区LGM年均气温较现在低 11～ 15℃ ,YD年均气温比现代低约 6～ 8℃。这一降温幅度与中国北方根据孢粉、砂楔、冰芯等所推测的气温下降值大体一致 ,亦与最近有关北半球高、中纬度冰期降温幅度的研究相符合

THE SAND WEDGE AND MIRABILITE OF THE LAST ICE AGE AND PALEOCLIMATIC RECONSTRUCTION IN HEXI CORRIDOR,GANSU,WEST CHINA

Mirabilite and sand wedge are the markers of cold\|dry climatic environment.The sand wedges in Hexi Corridor occur in the alluvial gravel (Q Pl 3)of bajada and high terraces.The 14 C dating of eolian sands in sand wedges proves they formed during the Last Ice Age,with the mean annual air temperature about -5 6℃.The mirabilite sedimentary layers developed from saline lakes which appear in the terminal end of continental rivers.The common 14 C and AMS 14 C dating ages of terrestrial dendritic remains in Huahai clay\|mirabilite interlayers are (11600±280)aB.P. and (11181±54)aB.P. respectively,proving that the mirabilite formed at the cold episode of the Last Glacial Maximum (LGM) and Younger Dryes (YD)in Huahai Lake.It is pointed out that the mean annual air temperature in LGM is 11～15℃ lower than present,and that in YD is 6～8℃lower.That decreasing temperature values are generally in concordance with those inferred by the research on sporollen,sand wedge and ice core in the northern China,and also correspond to the study of decreasing temperature during Ice Age in the middle and high latitude regions on the northern Hemisphere recently.