中国北方四剖面CaCO_3含量变化及其反映的古降水量

THE VARIATION OF CaCO_3 CONTENT IN FOUR PROFILES FROM THE NORTH OF CHINA AND THE RECONSTRUCTED PALEO-PRECIPITATIONS

中国北方自西向东的4个剖面,各地层CaCO3的含量呈现逐渐减少的规律。科尔沁剖面和延长剖面、西宁盘子山剖面CaCO3含量曲线表现出的特征为:在每一个古土壤单元的下部一定深度内CaCO3曲线都表现为一个明显的峰;新疆塔勒德剖面的各古土壤的CaCO3含量表现为表层比中、下部要高。利用CaCO3淀积深度恢复出来的部分区域的古降水量显示,末次间冰期期间盘子山剖面的古降水量大为352mm,延长剖面和科尔沁剖面的古降水量大约为500～550mm;末次冰期的间冰阶阶段科尔沁剖面的古降水量大致为320～360mm;延长剖面古降水量大约为443mm;全新世以来盘子山剖面的古降水量大约为306mm,延长剖面和科尔沁剖面的古降水量大约为320～380mm。这些数据可为半定量恢复地质历史时期古环境状况提供依据。

CaCO_(3) content decreases gradually in each stratum of the four profiles from arid and half arid area from west to east in the north of China.The content curves of CaCO_(3) in Keerqin,Yanchang and Panzishan profiles show that a peak of CaCO_(3) content appears in some depth of each stratum of paleosol,and the top and bottom CaCO_(3) content is higher than that in the middle of the paleosol of each profile,while CaCO_(3) content in Talede,Xinjiang is higher in the middle and at the bottom.Besides the climate factor (precipitation affects deposition and transport of CaCO_(3) ),there are some factors of geographical location and material source.Moreover,CaCO_3 content of loess chemical material and deposition depth manifest loess material transport and enrichment,thus through CaCO_(3) content,paleo-precipitation during paleosol development can be resumed in some areas,to let us know weathering soil effect and climate and environment evolvement.