• 责任者：Teng Xiaohua (Key Laboratory of Western China’s Environmental Systems ; Ministry of Education ; Research School of Arid Environment and Climate Change ; Lanzhou University ; Lanzhou 730000 ; China) ; Han Wenxia
• 刊名：Quaternary Sciences
• 出版年：2013
• 卷期：33(5)
• 关键词：第四纪 ; Quaternary ; 干旱 ; drought ; 柴达木盆地 ; Qaidam Basin
• 页码：p.866-875
• 图表：5 illus., 70 refs.
• 分类号：1400
• issnNo：ISSN1001-7410
• isbnNo：CN11-2708/P

     As the largest temperate arid region,the vast Asian arid inland has attracted wide interests due to its great impacts on global climatic change.However,its evolution history and its relation with the westerlies,Tibet uplifts and global change are still unknown.Although many related studies have been carried out,most of the studies are mainly based on the eolian records from the surrounding areas,and only few records are directly from this arid region. The Qaidam basin,located in the eastern part of this vast arid region,develops continuous and well-exposed Cenozoic sediments,providing a unique opportunity to study aridity of the Asian inland.We obtained a 938.5m long lake sediment core（SG-1）（38°24＇35.3＂N,92°30＇32.6＂E;2700m a.s.l.）with an average recovery rate of 95% from the saline playa in the depocenter of the Chahansilatu sub-basin between the Eboliang anticline and the Jianshan anticline in the western Qaidam basin.A combined detailed paleomagnetic dating, OSL and U series dating of the core determined its age at about 2.77Ma to 0.10Ma. The core is mainly comprised of evaporate-bearing fine mudstone-siltstone sequence.In the lower 390.0~938.5m part of the core,the sediments consist mainly of alternation of dark-gray or bluish-gray generally laminated mudstone and siltstone and gray calcareous mudstone and marl/limestone.In the upper 0~390m part of the core,the lithology is characterized by cycles of thick gray-white salt and grayish black massive-laminated mudstone-siltstone mostly containing gypsum crystals or thin gypsum layers.This study mainly carries out a more detailed analysis of carbon and oxygen isotopes for the upper 0~350m part of the core with 0.1~1.0Ma.Samples with high carbonate contents （ 〉30wt% ） were systematically collected at an average interval of ca.3m and 135 samples were selected.We collected 12 rock samples（including limestone and marble）from exposed strata since Precambrian in the surrounding Kunlun,Qilian and Altun major river basins to determine the carbon and oxygen isotopes in lakes debris and further to learn whether the lake debris can effect the isotopes of the lacustrine carbonate.All samples were first oven-dried at 40℃ and ground into fine powder.After standard routine of treatment,the carbon isotope and oxygen isotope results were analyzed using a MAT -252 Mass Spectrometer,with a precision of better than 0.1‰ . The analyses of stable isotopes of carbonates from the SG-1 core suggest that the carbonates in this core are authigenic and the oxygen isotope mainly reflects the regional aridity.The carbonate isotope records indicate that there exists an evident long-term persistent aridification of Asian inland since ca.1.0Ma,followed by an accelerated drying since ca.0.6Ma.The Qaidam paleo-lake changed from brackish lake to salt lake and finally playa accordingly. From 1.0Ma to 0.6Ma,the carbon and oxygen isotope values change from -1.4‰ to 3.7‰ and -2.9‰ to 3.9‰,respectively,indicating a minor drying trend.We speculate that both the northern hemisphere glaciation and the uplift of the Tibetan Plateau in the mid-Pleistocene（Kunhuang Movement）occurred at about 1.0Ma might have collectively prompted the drying of the Asian inland during this time. Since 0.6Ma,both the carbon and oxygen isotope values show sharp synchronous increasing trends（changed from -0.6‰ to 7.3‰ and -1.7‰ to 11.9‰,respectively）,which are discordant with the marine oxygen isotope records.We suggest that the rapid uplift of the Tibetan Plateau（Kunhuang Movement C）might have contributed to the aridification of the Asian inland through changing or enhancing the westerly jet and blocking the moisture input from the westerlies and monsoons.