萨拉乌苏河流域DGS1层段主量元素记录的全新世气候变化

选取毛乌素沙漠东南部边缘萨拉乌苏河流域具有代表性的滴哨沟湾剖面全新统DGS1层段，通过测定样品的主量元素SiO2、Al2O3、TOFE（全铁）、CaO、MgO、K2O、Na2O、TiO2的含量并分析其特征，结合年代测定结果，探讨该地全新世气候演变．结果表明，主量元素表现出2个不同时期的不同波动方式：1CS-9P期间（0-3760 a BP），Al2O3、TOFE、CaO、MgO、K2O、Na2O、TiO2基本表现为在湖沼相中含量大于次生黄土，次生黄土中含量大于沙丘砂；从10LS到21LS（3760-11000 a BP）CaO、MgO在湖沼相中出现峰值，尤其是在15LS（7340-8170 a BP）及其上下达到顶峰，其它主量元素表现为低值．通过分析认为，DGS1层段实际上是全新世以来多次东亚冬夏季风的交互演替过程下的堆积－风化产物，是气候地层的真实记录．依据CIA值与和SiO2/(Al2O3+TOFE)比值，将DGS1层段主量元素信号记录的全新世气候可分为4个阶段全新世早期气候好转、全新世鼎盛期、大暖期向寒冷期转变的波动期、降温不稳定和沙漠化频繁变化时期．

Holocene Climate Changes Recorded by the Major Elements in the DGS1 Segment of the Salawusu River Valley

The typical segment DGS1 in the Dishaogouwan section from the Salawusu River Valley of the southeast depression of the Mu Us Desert is selected to study climate changes during the Holocene. The analyse of the concentrations and characterizations of major elements-- SiO2、Al2O3、TOFE、CaO、MgO、K2O、Na2O、TiO2, along with the age determination show that the fluctuations of major elements exhibit differences in two different periods: from 1CS to 9P, the contents of Al2O3,TOFE , CaO, MgO, K2O, Na2O, TiO2 are more than those in the secondary loess, and they are less in the dune sands than those in the secondary loess; from 10LS to the bottom of the DGS1 segment, the contents of CaO and MgO show peaks in the lacustrine facies, especially, the high peak appears in the15LS, and other major elements display low values. Those studies suggest that the DGS1 segment is actually the weathering accumulation under the alternations of Asian winter and summer monsoons since the Holocene, which is the stratigraphical climate record. Besides, according to the CIA values and SiO2/(Al2O3 + TOFE) ratios, the Holocene climate recored by the major elements in the DGS1 can be divided into four periods:the ewarming period of the Early Holocene;Holocene heyday;the fluctuation period from the Megathermal to cold;and the cooling instability and desertification period.