内蒙高原腾格淖尔中全新世湖泊干旱环境的粒度和元素记录

THE GRAIN SIZE AND ELEMENT RECORD OF THE DRY MID-HOLOCENE LAKE IN THE TENGGER NUUR,INNER MONGOLIA PLATEAU,CHINA

对内蒙古高原腾格淖尔湖泊约400cm剖面沉积物的粒度、碳酸盐和TOC含量以及元素地球化学特征进行分析,利用Mg/Ca、CEC、Rb/Sr、CIA、古气候指数C等的古气候古环境指示意义,结合3个AMS 14 C年代结果,利用该区域湖泊"碳库效应"研究的基础进行年代校正,分析了腾格淖尔大约9 000cal.aBP以来古环境演变过程。研究发现腾格淖尔全新世早—中期(约9 000～4 500cal.aBP)气候暖干,有效湿度小,而湖泊为高湖面,最高湖面在约8 000～6 200cal.aBP期间;湖泊的高水位主要是继承了早全新世夏季风增强形成的扩张湖泊;3 000～4 500cal.aBP以来气候冷干,有效湿度稍有增加,湖面在降水持续减少情况下逐渐收缩干涸。

A 400-cm long core from Tengger Nuur of the Inner Monglia Plateau was collected and grain size,carbonate-content,TOC-content,metal elements and ratios analyzed in the environmental lab of Lanzhou University.3 14C AMS samples were determined by the NFS Arizona AMS Laboratory of Arizona University in the USA.Carbon reservoir effect was considered for calibration of the dating data using the about 1000 year data from researching results in the past.Environmental proxies of Mg/Ca、CEC、Rb/Sr、CIA and palaeoclimatic index C were used for construction of palaeoenvironmental change model since ~9 000 cal aBP.A warm and dry palaeocliamtic environment was prevailed during the mid-Holocene（~9 000~4 500cal.aBP） with high lake level and low effective humidity.The lake remained high in the Early Holocene as summer monsoon strengthened with high rainfall and temperature.The lake approached its highest level about ~8 000~6 200 cal.aBP.After 3 000~4 500 cal.aBP,palaeoclimate turned dry and cold,and the increase in effective humidity was in favor of vegetation in this area.However,with decreasing rainfall,the lake shrank gradually until it dried up.