腾格里沙漠西南缘土门剖面微量元素记录的MIS3高分辨率季风环境变化

对位于腾格里沙漠西南边缘的土门剖面中时代为MIS3的TMS3层段进行序列分析与¹⁴C和释光测年，并在此基础上对沉积层进行系统的微量元素地球化学分析。结果表明：TMS3是由沙丘砂与其他5类沉积相（黄土状亚砂土、砂黄土、湖沼相、水成黄土和古土壤）构成的相互叠覆的沉积，形成14.5个“沉积旋回”。TMS3微量元素Mn、P、Sr、Rb、V、Zn、Cr、Ni、Cu和Nb在沙丘砂中含量低，在其他5类沉积相中含量高；Rb/Sr比值则呈现相反的变化趋势。在剖面上，随着沙丘砂与这5类沉积相的交替，元素含量、Rb/Sr比值表现出明显的峰（高值）谷（低值）波动，并形成基本上与沉积旋回数量一致的“元素旋回”——ECY1—ECY14.5。该层段14.5个元素旋回揭示了相同数量的腾格里沙漠东亚冬夏季风演变的“旋回”——MCY1—14.5，包括14次冬季风事件和15次夏季风事件，每个季风旋回的持续时间平均约2.48 ka；TMS3元素记录的15次夏季风事件与GRIP冰芯和葫芦洞石笋MIS3-δ¹⁸O曲线的间冰阶具有相同的发生次数，也与邻近的古浪黄土MIS3中的间冰阶可以进行很好的对比。土门剖面TMS3的地球化学迁聚行为和沉积相，在一定意义上诠释了MIS3北半球冷暖波动——腾格里沙漠东亚冬夏季风环境变化的响应过程。

High-resolution monsoonal environment change in MIS3 based on trace elements in the Tumen Section on the southweest edge of Tegger Desert

The TMS3 segment in the Tumen section， equivalent to the MIS3， is located at the southwest margin of the Tengger Desert. Based on the sedimentary sequences analysis and ¹⁴C and OSL dating ages， geochemical trace elements were analyzed. The study shows that TMS3 segment consists of interbedding stratigraphic sequences of dune sands with loess-like subsoil， sandy loess， lacustrine facies， alluvial loess， or paleosols， forming 14.5 sedimentary cycles. The contents of trace elements Mn， P， Sr， Rb， V， Zn， Cr， Ni， Cu， Nb are low in dune sands， but high in other 5 sedimentary facies in the TMS3， and the ratios of Rb/Sr display reversed tendency， which show obvious element contents and Rb/Sr ratios alternation with low values and high peaks between dune sands and other 5 sedimentary facies， indicating 14.5 elemental cycles ECY1-ECY14.5， which are consistent with sedimentary cycles. It suggests that 14.5 element cycles in the TMS3 represent 14.5 monsoonal cycles （MCY1—14.5） in the alternation of East Asian winter and summer monsoons during the MIS3， including 14 times of winter monsoons and 15 times of summer monsoons， and average time duration of each monsoon cycle is 2.48ka. 15 summer monsoon events recorded by trace elements in the TMS3 correspond well to the stadials revealed in the ice core of the GRIP and by δ¹⁸O in Huludong Cave， as well as those found in the adjacent area in the loess in Gulang during the MIS3. The geochemical migration and accumulation and sedimentary facies in the TMS3， to some extent， illustrate East Asian winter and summer monsoon environment changes in the Tengger Desert in response to the cold-warm climate fluctuations in the Northern Hemisphere during the MIS3.