长江镇江段第四纪沉积物重矿物特征及其指示意义

Characteristics of heavy minerals in the Quaternary sediments of Zhenjiang section,Yangtze River and their indicative significance

选取长江下游世业洲的第四纪钻孔资料,研究了重矿物的垂向分布特征,以此探讨长江镇江段第四纪以来的沉积类型以及物源演变。结果显示,该区自中更新世开始接受沉积,依次形成河床相、边滩相、漫滩相、河口三角洲相。重矿物自下而上分为2个组合段,分别对应更新世和全新世。更新世地层以角闪石、蓝晶石、石榴石等作为特征矿物,且不稳定矿物含量高于稳定矿物,表明沉积物以近源居多;全新世特征矿物为辉石和钛铁矿,稳定矿物含量高于不稳定矿物,重矿物种类与现代长江中上游类似,表明此阶段沉积物以远源物质为主。

Based on the drilling core data in Shiyezhou of the lower Yangtze River,the vertical distribution of the heavy minerals has been studied in order to discuss the provenance evolution and sedimentary type in Zhenjiang section of the Yangtze River since the Quaternary. The result reveals that this area began to deposit since the mid-Pleistocene,forming river bed,point bar,flood plain and estuarine delta facies successively. Two zones of heavy minerals were identified,with the upper zone related to Holocene and the lower zone related to Pleistocene. The Pleistocene strata mainly contain heavy minerals of hornblende,kyanite and garnet,and have more unstable minerals than stable minerals,suggesting that proximal materials are in domination. In contrast,the Holocene strata contain dominant heavy minerals of arepyroxene and ilmenite,and the content of stable minerals is greater than unstable minerals; the types of heavy minerals are similar to those of the upper and middle Yangtze River,indicative of their dominant distal source materials.