对巴丹吉林沙漠东南缘查格勒布鲁剖面该层段的CGS3a层段(Chagelebulu Section 3a)139个样品的主元素SiO_2、Al_2O_3、TOFE(Fe_2O_3+FeO)进行分析,划分出与地层旋回对应的5.5个化学元素旋回。研究认为:沙丘砂和黄土中SiO_2呈现的峰和Al_2O_3、TOFE、(TOFE+Al_2O_3)/SiO_2和CIA呈现的谷是类似于现代干冷的冬季风在过去多次作用的结果,而嗣后的湖相SiO_2呈现的谷和Al_2O_3、TOFE、(TOFE+Al_2O_3)/SiO_2和CIA的呈现的峰是类似于现代暖湿的夏季风在过去多次作用的结果。即35 000~25 000 a B. P.该沙漠经历了5次冬季风和6次夏季风交替的气候波动,这些气候事件与GRIP冰芯氧同位素记录的D/O(Dansgaard/Oeschger)事件相对应,Heinrich事件也在其中有很好体现。CGS3a层段所记录的千年尺度的气候波动可能是受到了北大西洋气候突变的影响。
英文摘要:
The CGS3a segment of the Chagelebulu section in the southeastern of Badain Jaran Desert, records five and a half sedimentary cycles consisting of alternations between dune sands or loess and overlying fluviolacustrine during 35 000-25 000 a B.P. Based on the analysis of primary chemical elements (139 samples) SiO_2, Al_2O_3, TOFE(Fe_2O_3+FeO), we found that:1) The variation of the primary chemical element content shows five and a half chemical element cycles, which are approximately consistent with the sedimentary cycles. 2) Among SiO_2, Al_2O_3, TOFE, (TOFE+Al_2O_3)/SiO_2 and CIA, SiO_2 has the highest content in the CGS3a (range: 44.98% -90.02%, average: 65.96%), followed by Al_2O_3 (range: 5.17%-15.37%, average: 11.87%), and then TOFE (range: 1.40%-6.90%, average: 4.19%), (TOFE+Al_2O_3)/SiO_2(range: 0.07-0.47, average:0.27) and CIA(range: 39.66-68.26, average: 58.97). 3) The contents of SiO_2, Al_2O_3, and TOFE significantly differ among the different sedimentary facies. The average SiO_2 content is higher in the dune sands than in the fluviolacustrine and loess, whereas the average Al_2O_3, TOFE, (TOFE+Al_2O_3)/SiO_2 and CIA contents are higher in the fluviolacustrine and loess than in the dune sands. This study suggests that the peaks of SiO_2 contents and the valleys of Al_2O_3, TOFE, (TOFE+Al_2O_3)/SiO_2, and CIA contents in the dune sands and loess represent the dominant periods of East Asian winter monsoon, the valleys of SiO_2 contents and the peaks of Al_2O_3, TOFE, (TOFE+Al_2O_3)/ SiO_2, and CIA contents in the fluviolacustrine reflect the dominant periods of East Asian summer monsoon. Therefore, we suggest that the CGS3a segment experienced at least five cold-dry climates and six warm-humid climates during 35 000-25 000 a B.P. Of these, the warm climate fluctuations (23LS, 25LS, 27LS, 29LS, 31LS, 33LS) correspond well to the Dansgaard-Oeschger events (D/O3-D/O8, ie, 25 000 a B.P., 26 000 a B.P., 29 000 a B.P., 31 000 a B.P., 32 000 a B.P., 35 000 a B.P.) recorded in the Greenland Ice Core Project (GRIP). Moreover, the cold period (28D, 30 600 a B.P. 2 900 a B.P.) correlates well with the Heinrich Event H3 (approximately between 29 000 a B.P. and 31 000 a B.P.). The abrupt changes of East Asian monsoon recorded in the CGS3a segment correspond well to Dansgaard-Oeschger climate fluctuations and Heinrich events, whicha indicate that the East Asian monsoon was probably affected by the climate changes in the North Atlantic. This study offers significant geological evidence to support the East Asian monsoonal millennial scale climatic fluctuations, which is the regional response to the millennial scale climate changes from the North Hemisphere in China's deserts during 35 000-25 000 a B.P.