摘要
结合孢粉分析,对兴凯湖一根长269cm的沉积岩芯研究表明:沉积物粒度分布特征可以较好地反映区域气候变化,即粗粉砂和砂增多对应于降水减少的低湖面时期,细粉砂增多对应于降水增加的高湖面时期,而粘土增加则对应于气候干燥的静水沉积环境。约27740-25540cal aBP时期,沉积物颗粒较粗,湖区处于低湖面的冷干气候;而随后25540-23650 cal aBP时期,中粉砂增加,粘土较少,分选性较好,湖区处于冷湿气候环境23650-19940cal aBP阶段,湖面封冻期长,沉积物粘土较多,湖区气候冷干,对应于末次盛冰期。19940-14510cal aBP阶段,细粉砂增加,比前期降水增多,温度也有所升高。14510-10800cal aBP时期,本地区进入晚冰期,沉积物粒径波动频繁,依次出现较高含量的细粉砂-粗粉砂-粘土阶段,反映了暖湿到干燥的气候变化,对应于北欧的B(o|¨)lling/Older Dryas/Aller(o|¨)d/Younger Dryas气候波动期。10800-1050cal aBP,总体上沉积物粒径变化不大,中粗粉砂含量基本保持低值,细粉砂逐渐增加,粘土逐渐减少,显示深水稳定沉积环境,降水逐渐增多,处于全新世暖湿期;其中8330-7000cal aBP阶段,粗颗粒迅速增加较多,对应于8.2 cal kaBP冷事件。约1050cal aBP以来,沉积物中值粒径大幅度增加,湖面水位下降幅度较大,气候变凉干,也反映了人类活动增强造成水土流失加剧。
Lake Xingkai, a boundary lake between China and Russia, is the largest freshwater lake in Northeast Asia. The paleoclimate variation since 27.7kaBP was reconstructed based on a 269cm-long sediment core in Lake Xingkai. The chronology was measured by ^210Pb and ^137Cs activities and AMS ^14C dating. Grain size distribution of the lake sediment was inferred to be a proxy for past precipitation, compared to pollen analysis. The high percentage of coarse silt and high Md values reflect a low lake level, and increase in fine silt indicating plentiful precipitation and the high clay content correspond to cold dry climate. The results show that： It was in cold-dry between 27740 and 25540 cal aBP, when lake level was low, as indicated by high Md values and coarse silt contents of the lake sediments. During 25540 and 23650 cal aBP, the sediments was characterized by low clay content, marking a significant increase in effective precipitation in cold wet climate. The Last Glacial Maximum between 23650 and 19940 cal aBP was marked by high content of clay because of the frozen lake surface, corresponding to especially cold-dry. From 19940 to 14510 cal aBP, precipitation increased when fine silt content increased. The fluctuating characteristics of the sediments grain size indicated that precipitation increased first and decreased finally during 14510 and 10800 cal aBP, corresponding to Btilling/Older Dryas/Allcroed/Younger Dryas periods. From 10800 to 1050 cal aBP, lake level rose evidently suggested by higher content of fine silt when the precipitation was relatively abundant in Holocene, in which 90 -78m section shows that the sand and coarse silt content increased sharply, indicating that the lake level experienced a rapidly decline because of cold-dry climate around the 8.2 kaBP. Since 1105 cal aBP, the portion of sand and coarse silt increased markedly, reflecting low lake level under a cool-dry climate, companied with remarkable increase in soil erosion and terrestrial material into lake possibly related with local human activities.
出处
《湖泊科学》
EI
CAS
CSCD
北大核心
2010年第1期110-118,共9页
Journal of Lake Sciences
基金
国家自然科学基金项目(40872117)资助
关键词
东北地区
兴凯湖
沉积物粒度
古气候
湖泊沉积物
Northeastern China Region
Lake Xingkai
grain size
paleoclimate
lacustrine sediments
