The characteristics of major elemental oxides and paleoclimate changes recorded by the major elements of the last deglaciation segment of the Tumen section on the southern edge of the Tengger Desert
腾格里沙漠南缘土门剖面末次冰消期层段由3层沙丘砂、2层湖相沉积、2层古土壤和5层黄土构成。主元素氧化物中,SiO_2含量在沙丘砂层呈现峰态,而在黄土、湖相沉积及古土壤呈现谷态;Al_2O_3、TFe(Fe_2O_3 + FeO)、CaO、MgO、 Na_2O、K_2O和TiO_2则在沙丘砂层呈现为谷,在黄土、湖相沉积及古土壤中呈现为峰,SiO_2分别与Al_2O_3等氧化物在垂直方向上呈镜像对称。结合研究区地形,对元素氧化物特征分析后,认为可用硅铝比高低变化指示本区东亚冬夏季风变化。划分出了9个冷暖波动事件,按时间先后依次为:C5(14930~14847 a BP)、W4(14847~13810 a BP)、C4(13810~13620 a BP)、W3(13620~13340 a BP)、C3(13340~13010 a BP)、W2(13010~12650 a BP)、C2(12650~12050 a BP)、W1(12050~11860 a BP)和C1(11860~11600 a BP)。本研究层段与格陵兰GRIP冰芯及南京葫芦洞石笋记录的末次冰消期冷暖变化有较高的相似性,可能本区末次冰消期季风气候变化受北半球高纬驱动。
英文摘要:
The last deglaciation segment of the Tumen section on the southern edge of the Tengger Desert is composed of three layers of dune sand,two layers of lacustrine facies,two layers of paleosoil, and five layers of sand loess. Among those major elemental oxides,SiO_2 shows crest in the layers of dune sands,but shows trough in the layers of lacustrine facies, paleosoil and sand loess. In contrast, Al_2O_3, TFe (Fe_2O_3 + FeO), CaO,MgO,Na_2O, K_2O, TiO_2 show trough in the layers of dune sands,but show crest in the layers of lacustrine facies, paleosoil and loess. SiO_2 takes an opposite mirror symmetrical change in the vertical direction with Al_2O_3,etc. We think that changes in silica-alumina ratio could indicate the fluctuation of Asian monsoon climate after analyzing changes in elemental oxides in combination with the particular terrain. Nine cold and warm incidents could be distinguished in terms of silica-alumina ratios. They are C5 (14930~14847 a BP),W4(14847~13810 a BP), C4 (13810~13620 a BP), W3 (13620~13340 a BP),C3 (13340~13010 a BP),W2 (13010~12650 a BP),C2 (12650~12050 a BP),W1 (12050~11860 a BP), and C1 (11860~11600 a BP) in turn. As for the last deglaciation climate fluctuation which was recorded by the last deglaciatioon segment of the Tumen section. The data collected from the Greenland GRSP ice core and Nanjing Hulu cave stalagmites are highly similar. Asian monsoon climate changes during the last deglaciation in this region may be caused by changes in thermohaline circulation in the Northern Hemisphere.