末次间冰期我国半干旱盆地Rb、Sr的迁移聚集规律与环境演变——以萨拉乌苏河流域米浪沟湾剖面研究结果为例

萨拉乌苏河流域米浪沟湾剖面末次间冰期层系记录了8.5个有风成的古沙丘砂与河湖相和/或古土壤构成的沉积旋回。该层系Rb、Sr元素含量分布具有明显的规律，主要表现为古沙丘砂中的Rb、Sr含量相对迁移，而在上覆河湖相和/或古土壤中相对聚集，构成末次间冰期的Rb、Sr含量迁移与聚集的8.5个元素旋回。研究表明，由Rb、Sr含量变化构成的这些旋回主要是由干冷暖湿气候波动所致。该地末次间冰期层系由上至下可划分为5个层段，即MS1~MS5。Rb、Sr含量在MS1、MS3、MS5和MS2、MS4分别呈现明显的峰态和不同程度的低谷，揭示出前者与后者分别是受到暖湿和干冷气候影响的阶段。据此，可以将 MS1、MS2、MS3、MS4和MS5依次在气候性质和阶段上可与GRIP冰芯和Sulu 海MIS5a、5b、5c、5d、5e诸亚段进行对比。研究亦表明，河湖相和古土壤Rb/Sr曲线却都不尽是峰态，黄土高原Rb/Sr值的气候意义并不完全适宜说明半干旱盆地或洼地的古环境变化。

Moving and Accumulating Law of Rb, Sr with Environment Evolving in Semiarid Basin of China during the Last Interglacial --Reflected by Study Result on Milanggouwan Stratigraphic Section in the Salawusu River Valley

The Last Interglacial Period strata in the Milanggouwan section in the Salawusu River valley on the Ordos Plateau,China,have 8.5 sedimentary cycles composed alternately of eolian dune sands,fluvio-lacustrine facies and/or paleosols.The distributing regularity of Rb,Sr element content was that they transplanted relatively in the eolian dune sands and accumulating relatively in the fluvio-lacustrine facies and/or paleosols,composing 8.5 cycles of Rb,Sr elements moving and accumulating in the Last Interglacial Period in the study region.The study showed that these cycles were chiefly resulted from dry-cold and warm-humid climate fluctuations.The stratigraphical sequences during the last interglacial period can be further divided into 5 phases from top to bottom,among which the Rb,Sr content showed peaks in MS1,MS3,MS5 influenced by warm-humid climate,and showed low values in MS2,MS4 influenced by dry-cold climate.Hereby,viewed from climate feature and variation phases,MS1,MS2,MS3,MS4 and MS5 might successively correspond to the sub-stages,MIS5a,MIS5b,MIS5c,MIS5d and MIS5e in GRIP Ice Core and Sulu Sea.The study also showed that the Rb/Sr curves are not all peaks in fluvio-lacustrine facies and paleosols,so the climate significance of Rb/Sr value on the Loess Plateau can not completely explain the changes of ancient environment evolving in semiarid basin or depression in our country.