腾格里沙漠西北缘湖泊沉积记录的区域风沙特征

Eolian Activity and Environment Evolution History Recorded by the Qingtu Lake,NW Tengger Desert

对位于腾格里沙漠西北缘的青土湖QTL01剖面进行了沉积物粒度分析,并利用粒级—标准偏差模型,提取出了对沉积环境变化敏感的粒度组分,60～550μm粒级含量指示了区域风沙活动的强弱,而<60μm颗粒含量指示了入湖径流量的变化。结合14C测年结果,探讨了10～2.5CalkaBP青土湖地区风沙活动和环境演化特征:10～7.8CalkaBP,<60μm组分含量逐渐增加,指示湖区入湖径流逐渐增多,同时60～550μm组分含量逐渐减少表明湖区风沙活动逐渐减弱,总体上表明了早全新世该区域环境逐渐转湿;7.8～7.5CalkaBP,60～550μm组分含量几乎占该阶段沉积物的95%以上,表明风沙活动极为强烈,区域非常干旱;7.5～5CalkaBP,沉积物中<60μm、60～550μm的组分含量相对稳定,且<60μm组分含量达到了10～2.5CalkaBP期间最高值,表明了区域风沙活动较弱,气候环境湿润稳定;5～2.5CalkaBP,<60μm组分含量逐渐降低,而60～550μm组分逐渐升高,表明了区域风沙活动逐渐加强,入湖径流逐渐减小,指示了区域干旱化的趋势。

Lacustrine sediment samples from QTL01 section of Qingtu lake in NW Tengger Desert, pretreated by removing the organic matter and carbonate, are measured by Malvern 2000. Standard deviations are calculated for samples from the depth of 214 - 560cm of QTL01 section, and grain size components sensitive to environment are obtained. The result from our study suggests that the content of 60 -550 m component is sensitive to local eolian activity and the content variation of 〈 60 m component indicates the changes of river discharges drained into the lake. Based on the grain size analysis and ^14C dating, we reconstructed the variations of eolian activity and environment of the studied area during 10 -2.5 Cal kaBP： From 10 to 7.8Cal kaBP, gradually decreasing eolian activity indicated the area was becoming humid during the early Holocene ; From 7.8 to 7.5 Cal kaBP, very intense eolian activity suggested a regional dry event; From 7.5 to 5 Cal kaBP, weak eolian activity indicated a very humid environment; From 5 to 2. 5 Cal kaBP, the gradually weaker eolian activity showed a trend toward aridity in the study area.