鄂尔多斯高原中部5．8-4．5Cal kaBP气候旋回的地层记录  

Climate Change Recorded in a Lacustrine Stratum in the Ordos Plateau during the Period of 5.8～4.5 Cal kaB.P.

作　　者：曹广超[1] 马海州[2] 王晨华[3] 

机构地区：[1]中国科学院研究生院,北京100039 [2]中国科学院青海盐湖研究所,青海西宁810008 [3]兰州大学资源环境学院,甘肃兰州730000

出　　处：《干旱区研究》2008年第2期254-258,共5页Arid Zone Research

基　　金：国家自然科学基金面上项目(40471138);“西部环境”创新群体项目(40421001);高校博士点基金项目(20050730030);国家重点基础研究发展规划项目(G200048701)

摘　　要：通过对鄂尔多斯高原现代风成砂与PJHZ剖面沉积物粒度特征的对比分析，确定了剖面中4个层位（290～210，190～160，153．5～123．5，50～40cm）基本属于风成砂沉积。结合粒度参数、碳酸钙含量、总有机碳含量及年代序列，认为此区域在5．8～4．5Cal kaBP存在以下沉积旋回：～5749Cal aBP，沉积风成砂，反映该时期风砂活动强烈，气候干燥，冬季风强盛；5749Cal aBP前后，沉积物为灰绿色湖相层，表明这一时期存在短暂的湖面扩展，沙漠退缩；5749～5370Cal aBP，沉积风成砂，反映了湖泊的退缩和沙漠的扩展；5370～4895Cal aBP，湖相沉积物，反映了流域降水量的增多；4895～4580Cal aBP沉积风成砂后，4580Cal aBP前后又出现了短暂的湖相沉积，之后又是风砂沉积。With a view of deriving desertifieation （aeolian action） information from the Mu Us Desert, a sensitive region to climate change, in this paper the volumetric particle size distribution of five modern desert sand samples and 30 profile samples, collected from the Ordos Plateau and the front of low terrace of the Pojianghaizi Lake, is studied. The results show that the grain size characteristics of the samples at depths of 290～ 210 em, 190 ～160 em, 153.5 ～123.5 em and 50 ～40 em at the Pojianghaizi profile are significantly similar to that of modern desert sand, which reveals that the sediment at these depths is the paleo-desert sand （aeolian sand）. Moreover, it is observed that there are 3 layers of laeustrain sediment embedded in the Pojianghaizi profile. The analyzed results of the radiocarbon dating, grain size, TOC and CaCO3 reveal that there was a sediment sequence ranging from 5.8 Cal kaB. P. to 4.5 Cal kaB. P. ： before 5 749 Cal aB. P. , the overlaying aeolian sand layer reveals that an intensive aeolian action occurred under dry-cold climate due to the strong winter monsoon, and it is followed by a thin layer of lacustrine sediment, which reveals that a short episode of desert retreating and lake enlargement occurred ; an aeolian sedimentation occurred during the period from 5 749 to 5 370 Cal aB. P. , which reveals that the desert expanded again; the period from 5 370 to 4 895 Cal aB. P. was characterized by a lacustrine sedimentation with a main composition of clay and silt, indicating the catchment of the Pojianghaizi Lake experienced a significant increase of precipitation; after the aeolian sedimentation with a thickness of 50 em during the period from 4 895 and 4 580 Cal aB. P. , a short period of laeustrain sedimentation occurred.

关 键 词：粒度 湖相沉积 风砂沉积 鄂尔多斯高原 

分 类 号：P532[天文地球—古生物学与地层学]