闽江口地区不同砂质沉积的粒度端元特征及其环境指示

Grain Size End-members Characteristics and Environmental Indication of Different Sandy Sediments in the Minjiang Estuary Area

海岸风沙的物质来源及其搬运、风化等作用受控于砂质海岸的地表过程,它们的粒度特征是解释区域环境演化的重要部分。基于闽江口地区河流砂、海滩砂、老红砂和海岸沙丘这4类砂质沉积,通过端元分析得出粒度端元特征,结合粒度频数分布曲线、粒度概率累积曲线、粒度参数和粒度组分特征分析和探讨了各端元指示的环境及与传统指标的关系,其结果如下:(1)4类砂质沉积98个样品共解译出5个端元,各端元的含量与粒度组分密切相关,在各类样品中的含量存在明显不同,代表了5类不同沉积动力强弱和稳定状况的沉积环境。(2)在粒度参数散点图中,海岸沙丘和海滩砂样品投影区域相对聚集、难以区分,而在EMA1-EMA2和EMA2-EMA3图中投影区域相对离散,较为敏感地区别了河流砂、海滩砂、海岸沙丘和老红砂的样品,并暗示了它们之间的关联,说明端元分析在区别海岸沙丘、海滩砂、河流砂和老红砂上具有优势,这为基于老红砂和海岸沙丘粒度特征重建区域环境提供了新的思路和方法。

The provenance,transport and weathering of coastal sand are controlled by the surface process of sandy coast.Their grain size characteristics are an important part of explaining regional environmental significance.The characteristics of grain size end-members are obtained by end-members analysis based on four types of sandy sediments including river sand,beach sand,“old red sand”and coastal sand dunes.The environment of each end-member indication indexes are discussed by grain size frequency distribution curve,the probability cumulative curves,grain size parameters,grain size component and end-member characteristics.The results showed that:(1)Five end-members are obtained by the parameterized end-members analysis of four types of sandy sediments including 98 samples,which can be divided into five kinds of sedimentary environments with different sedimentary dynamics and stable conditions.Their components in various samples are obviously different.(2)In the scatter diagram of grain size parameters,the projection area of coastal sand dunes and beach sand samples is relatively aggregated,which is difficult to distinguish.While the projected areas are relatively discrete in the scatter diagram of EMA1-EMA2 and EMA2-EMA3,the more sensitive areas are distinguished from samples of river sand,beach sand,coastal sand dunes and“old red sand”.This suggests that coastal dunes are moved by beach sand,which is formed by strong weathering of coastal dunes and shows that the end element analysis has advantages in distinguishing coastal sand dunes,beach sand,river sand and“old red sand”.These results provide new ideas and methods for reconstructing regional environment based on the grain size characteristics of“old red sand”and coastal sand dunes.