Abstract: On the basis of granulometric analysis of samples from colluvial wedge sediments caused by normal fault,the sedimentary environment is discussed.The total of 21 grain samples come from two sections distributed along the northern Xizhoushan Fault.Of the colluvial wedge sediments deposited at the foot of fault scarp,50～70 percents are gravel particles and they are widely distributed.Frequency curves are multi-ridge-shaped.Granular parameters are also calculated,which show a heterogenetic accumulation of colluvial wedge sediments with the main component of gravel particles.Comparison of granulometric analysis of the colluvial wedge samples with that on its upper side suggests that their granulometric quality is closely inter-related.

Key words: colluvial wedge, grain size, sedimentary environment, Xizhoushan

摘要： 通过对崩积楔沉积物进行粒度特征分析,研究崩积楔形成时的沉积条件和环境特征。沿系舟山北麓断裂,具体分析了水峪剖面、湖村剖面上各期崩积楔共21个样品的粒度及粒度参数。在崩积楔体中,砾、砂、黏土等各个粒级均有较大范围的分布,其中砾级总体概率含量达50%～70%。粒度分布为多峰态,分选差,偏度为极正偏,尖峰度>1,说明崩积楔是以砾级为主体的非均一性混杂堆积。崩积楔样品与作为物源的断层下盘样品的粒度分析对比表明,作为一种近源堆积,崩积楔的粒度特征与其下盘沉积物在粒度分布上有一定的继承性。

关键词: 崩积楔, 粒度, 沉积环境, 系舟山