摘要
临夏北塬黄土剖面样品的粒度分析表明,平均位在5.80～7.71φ令之间,分选系数为2.35～3.23,分选很差,偏态值为0.432～0.747,峰态值为0.7～1.3.参数散点图反映出随颗粒平均粒径减小,分选变差,偏态、峰态值减小,参数点趋于集中.颗粒分布有三个粒度组份,界线、含量、集中度分别为:组份Ⅰ:3～5.5φ,26～58%,59°～76.8°;组份Ⅱ:4.35～9φ,17.5～48%,16.5°～30.6°;组份Ⅲ:>6.8φ(或7.5φ),16～43%,3.6°～18.6°.不同的组份对应于不同的搬运、沉积过程.组份比在反映环境变化上有一定意义.最后,从岩性变化、粒度分布讨论了本区的气候旋迥.
The grain-size analyses of samples at Beiyuan loess section in Linxiashow that the mean values(ME)are between 5.80～7.71φ,standarddeviation (δ_1)2.35～3.23,sorting degree very bad,skewness values 0.432～0.747,kurtosis values 0.7～1.3.The plots of Parameters show withgrain-size reducing,sorting degree is worse,skewness values andkurtosis values become less,the spots in the plots tend to be gathered.There are three grain classes in the loess,the boundary,content andconcentrating degrees Class 1∶3～5.5φ,26～58%,59°～76.8°;ClassⅡ:4.35～9φ,17.5～48%,16.5°～30.6°;ClassⅢ:>6.8φ(or 7.5φ),16～,43%,3.6°～18.6°Difference in classes relates to different transmissionand sedimentation processes.The ratio of the class contents can showenvironmental change.In the last,the palaeoclimate in this area isdiscussed from the sedimental and grain-size characteristics.
出处
《兰州大学学报（自然科学版）》
CAS
CSCD
北大核心
1990年第1期93-102,共10页
Journal of Lanzhou University(Natural Sciences)
关键词
黄土
粒度
组份
古气候学
甘肃
grain size
characteristics
class
palaeoclimate
loess
Linxia
Gansu
China
