西宁地区黄土堆积的粒径分组  

Simulation of grain size distribution of Xining loess accumulation

作　　者：赵锦慧[1] 鹿化煜[2] 梅凡民[2] 张小曳[2] 李杨[2] 汶玲娟[2] 

机构地区：[1]湖北大学资源环境学院,湖北武汉430062 [2]中国科学院地球环境研究所黄土与第四纪地质国家重点实验室,陕西西安710075

出　　处：《干旱区地理》2008年第1期31-37,共7页Arid Land Geography

基　　金：国家自然科学基金(40325007和40121303);国家重点基础发展研究规划项目(G2000048703);中科院知识创新重要方向性项目(KZCX2-SW-118);湖北省科技厅自然科学基金(2005ABA064);湖北大学科研启动费(ky2004026)共同资助

摘　　要：采用对数正态分布的统计方法对青藏高原东北缘西宁盘子山黄土剖面的粒度数据进行拟合，结果表明盘子山剖面的粒度分布呈现出5个对数正态分布粒度方式的组合，各地层单元的粒径大体可分为5组，粒度分别介于平均粒径为0．4、9、20．40、63μm的范围，各粒径区域占整体粒径分布的比例比较相近；并且粘粒、极细粉砂组分的分选程度较差。盘子山剖面的粒度分布方式与黄土高原地区的分布有一定差异，〈4μm的组分在古土壤中占到11％～16％，在黄土中占到8％。无论在黄土堆积阶段，还是在古土壤发育阶段，盘子山地区相对于延长地区，20、40、63μm粒径组的比例都大，西宁盘子山地区黄土剖面的粗颗粒含量比较多。由于气候总体干旱、成土作用相对较弱，风化对黄土粒度组成的改变程度不会太明显，再加上青藏高原因冰川反复消融作用和磨蚀作用共同影响所产生的砂尘为黄土提供了可观的粗物质补给，因此盘子山剖面的黄土物源区呈现多样化特点。In the paper, the grain size data of loess profile at the Panzishan Mountain of Xining City in the northeast edge of the Qinghai-Tibet Plateau are fitted with the logarithm normal distribution function. The results show that the grain size distribution of the Panzishan profile has five grain size pattern combinations to logarithm normal distribution. The grain sizes of the layers of the profile can be classified approximately into five groups, and the grain sizes are in the scope of the average grain diameter of 0.4μm, 9μm, 20 μm, 40 μm and 63 μm, respectively. The scope ratios of the different grain sizes in the whole grain size distribution are rather close; and the clay, extremely fine silt groups have the bad sorting degrees. The grain size distribution mode of the Panzishan profile is different to a certain extent from that of the Loess Plateau. The group of the grain size less than 4 trm accounts for 11% - 16% in paleo-soil, and 8% in loess. In the loess accumulating stage or in the ancient soil developing stage, the proportions of the grain size groups of 20 trm, 40 trm, 63 trm in the Panzishan profile are all larger than those in the profiles at Yanchang Area of the Loess Plateau, which indicates that the loess profile at the Panzishan Mountain of the Xining City has higher content of coarse grains compared to the profile at the Loess Plateau. Because of the overall drought climate, relatively weak pedogenesis effect in Xining Area, the effect of weathering to change thg loess grain size composition is not obvious; in addition, the sand and dust produced by repeated ablation and abrasion of glaciers on the Qinghai-Tibet Plateau are the considerable coarse material supplies for lo- ess; therefore the loess of the Panzishan profile has the diversified source material areas.

关 键 词：青藏高原东北部 拟合 粒径分布 黄土 

分 类 号：P931.6[天文地球—自然地理学]