【摘要】 通过对柴达木察尔汗盐湖贝壳堤剖面沉积物粒度、碳酸盐和磁化率的对比,结合沉积物粒度频率曲线与多种粒度参数分析,详细讨论了研究剖面形成过程中物质搬运和沉积作用以及所反映的环境变化。结果表明沉积物粒度特征指示了湖泊水位的相对变化。在距今约38.2kaBP(14-C年代,未校正。下同)左右,沉积记录指示古湖泊的范围和水位已达到剖面位置,之后湖泊继续扩张、水位波动上升;在距今约35.5kaBP,粒径有一突然变细又变粗的过程,可能为一次较快速的湖面波动;在距今约35.5~33.3kaBP之间,沉积物颗粒较粗,碳酸盐含量和磁化率值低,揭示湖泊水位较低。距今约33.3~27.1kaBP之间,沉积物颗粒较细,碳酸盐含量较前一阶段高,表明此阶段湖泊水位相对较深,但粒度、碳酸盐和磁化率等指标也记录了三次较明显的湖泊快速但短暂的退缩过程;在距今约29.7~28.3kaBP,沉积物颗粒最细,指示了此时期可能为湖泊水位最高期。从距今约27.1kaBP开始,沉积积物颗粒明显变粗,揭示湖泊进入到退缩期,距今约18.1kaBP,粒度指标的变化和上层的盐壳指示湖泊进入快速盐化阶段,之后湖泊退出剖面所在的位置,此后研究区湖泊水位再也没有达到这个高度。更多还原

【Abstract】 Based on the grain size analysis, carbonate, magnetic susceptibility measurements on the shell bar section at Qarhan Lake in Qaidam Basin, the translation and sedimentation processes of the materials have been discussed and the lake level change history is reconstructed. The results suggest that from 38.2 to 35.5 ka C-14 BP be the period of lake formation, the grain size recorded a quick lake level rise event at 35.5ka BP; from 35.5-33.3ka BP the grain-size indicates that the lake level was low; from 33.3 to 27.1 ka BP, the fine grain-size, higher carbonate content and low magnetic susceptibility demonstrate a high lake level period. During this time, there are three times (28.3-27.1 ka BP,30.3-29.7 ka BP and 32.1-32.3 ka BP) during them lake level decreased. The lake level reached it maximum between 29.7 and 28.3ka BP with a finest grain-size. Between 27.1 and 18.1ka BP, the lake level started to decrease, and from 18.1ka BP, the lake retreated abruptly with a very strong increase of the evaporation, resulted in the salt formation. After that the lake shrank further and never reached this level again.更多还原