南极长城站区松散沉积物的粒度特征及环境意义

Grain Size Analysis and Environmental Significance of Sediments Around the Great Wall Station of China in Antarctica

南极长城站区地表松散沉积物按成因分为冰碛、冰缘沉积、冲积、湖积和海岸沉积。对其部分沉积的３．５２ｍｍ以下粒度分析表明，其粒度特征有明显的差别，能很好地反映其形成过程和环境特征。按冰缘沉积、冰碛、冲积和海岸沉积的次序，其粒度组成中砂粒级的含量增加，粉砂和粘土的含量减少；分选性由分选差变为分选较差和分选好；平均粒径分别落在极细砂、细砂、中砂和粗砂粒级；偏度由极正偏变为近对称。粒度参数散点图中各种沉积物的分布有明显的区别。粒度频率曲线的差别能很好地反映沉积物各自的形成过程特点。而冲积和海岸沉积服从正态概率分布，其累积图表现为直线形；冰缘沉积和冰碛服从罗辛概率分布。

Great Wall Station of China is located at the Fildes Peninsula (62°13′S, 58°58′W) of King George Island, South shetland Islands, Antarctica. Sediments around the station can be divided into glacial deposit, periglacial deposit, alluvial deposit, lacustrine deposit and coastal deposit by the origin. Analyses of their fine parts (<3 52 mm) show obviously difference amoung grain size composition, frequency curve, cumulative curve and scatter diagram of the glacial and perigiacial deposits, alluvium and littoral deposit. In the order of periglacial deposit -glacial deposit-alluvial deposit and coastal deposit, sand increases; silt and clay decreases; sorting changes from poor to good; mean grain size is in the scale of very fine, fine, medium and coarse sand respectively; skewness changes from very positive to near symmetric. Scatter diagram of grain size parameters show different distribution of various sediments. Difference among the frequency curves reflects the processing characters of the sediments. The alluvial deposit and coastal deposit follow normal distribution, they are straight lines in normal cumulative diagram. The periglacial and glacial deposits follow Rosin′s distribution, they are straight lines in Rosin′s cumulative diagram.