摘要
对昌黎海岸沙丘砂进行薄片统计,重砂矿物分析,电镜扫描,粒度分析及与海滩砂的对比研究发现,沙丘砂在物质组成、颗粒形态、石英砂表面结构特征和粒度特征方面均继承了海滩砂特征,不过,海滩砂中也有沙丘砂的某些特征,反映了两者沉积的混合。这是由于向岸风和离岸风共同作用的结果。
The coastal dunes form a zone 2-3km wide and more the 40 km long along the coast of Changli, Hebei. The dune sand deposits and the beach sand deposits on Changli coast are mainly composed of quartz and feldspars with subordinate amounts of rock fragments. But the beach sands have more shells and organism skeletons than the dune sands. The content of heavy minerals in the dune sands and beach sands is low. Heavy minerals are mainly amphi-boles, garnet, tourmaline and sphene. These minerals are accounted to be more than 86% of the heavy mineral fractions.Quartz grains in the study area were found to be mainly subrounded and subangular, and no difference between the properties of the dune sands and the Beach sands was noted. The quartz grains from dune sands are dish-shaped concave, upturned plate and subaqueous V-shaped depressions on the their surface.Dune sands are composed of fine and medium sand fractions, medium sand fraction accounts about 43% of the average grain-size distribution; beach sand deposits have a similar grain distribution. Mean grain size of dune sands is in a range from 1.6φ to 2.31φ, and they are well sorted with diameter from 0.24φ to 0-37φ. Beach sands are less sorted than adjacent dune sands, with standard deviation from 0.29φ to 0.46φ. Skewness and kurtosis of the dune sands are similar to those of the beach sands. Apart from diagram of skewness vers sorting, scatter plot diagrams differentiating the sedimentary behaviours of the dune sands and the beach sands are not effective. The similar case is found elsewhere. The areas where beach sands and dune sands are most difficult to dis inguish are those where the onshore wind and the offshore wind are varible frequently.
出处
《地质科学》
CAS
CSCD
北大核心
1993年第1期52-60,T002,共10页
Chinese Journal of Geology(Scientia Geologica Sinica)
关键词
沙丘砂
海滩砂
物质组成
风沙
海岸
Changli coast, Dune sands Beach sands, Textural characteristics
