萨拉乌苏河流域MGS2层段粒度与CaCO_3记录的千年尺度气候变化

Millennium-scale Climate Variations from the Record of Grain-size and CaCO_3 During the Pleniglacial in the Salawusu River Valley,China

测定、分析毛乌素沙漠东南缘萨拉乌苏河流域米浪沟湾剖面MGS2层段的粒度与CaCO3,发现该层段不同沉积相粒度Mz和σ呈现峰谷变化,CaCO3含量在沙丘砂及其上覆的河流相和湖沼相中依次变化于0-2.94%(平均值0.39%)、0.14%-2.68%(1.43%)和0.39%-15.57%(8.82%),并与Mz呈显著相关,构成与沉积旋回波动韵律相同的5.5个峰谷交替的粒度与CaCO3旋回。研究表明,毛乌素沙漠冬季风盛行时期沙丘砂强烈堆积,CaCO3发生迁移;夏季风盛行时期河流相和湖沼相发育,粉砂和粘土含量增加,CaCO3相对聚集。这些旋回代表东亚冬夏季风千年尺度交替变化的气候旋回。

The MGS2 segment of the Milangguowan stratigraphical section in the Salawusu River Valley, south- east of China＇ s Mu Us Desert, records 5.5 sedimentary cycles consisting of dune sands alternating with fluvial or lacustrine facieses. Based on the grain-size and CaCO3 analysis, it was found that Mz and o appear peaks and valleys in different sedimentary facieses. CaCO3 contents range from 0 to 2.94% （average 0.39%） in the dune sands, 0.14% to 2.68% （average 1.43%） in the fluvial facieses and 0.39% to 15.57% （average 8.82%） in the lacustrine, and appear 5.5 grain-size and CaCO3 cycles similar to the sedimentary facieses changes. And the CaCO3 contents have a significant correlation with Mz. The result show that the dune sands accumulate and Ca- CO3 moved greatly during the periods with a strong cold-dry winter monsoon. Whereas, the fluvial or lacus- trine facieses developed, silt and clay increased and CaCO3 gathered largely when the warm-humid summer monsoon strengthened. The observed climate fluctuations on millennium-scale during the Pleniglacial to the al- ternations attributed the strength of the East Asian winter and summer monsoons.