CAJ | 학술논문

广泛分布于宜昌至枝江-松滋一带的宜昌砾石层，对江汉平原乃至长江中游的地层划分、地貌演化、古环境变迁以及长江的形成与演化等研究具有重要意义。本研究在课题组前期研究的基础上，以本区内最具代表性的6个剖面为研究对象，对0．125～0．063mm粒级粉细砂质沉积物的重矿物特征进行了分析，结果显示宜昌代表性剖面砾石层细颗粒粉砂质沉积物的重矿物组合基本一致：锆石-绿帘石-白钛石-赤褐铁矿-钛铁矿-磁铁矿。源-汇分析表明，重矿物组成所指示的源区原岩类型除了三峡地区的还有长江三峡以西的金沙江、岷江、嘉陵江及乌江流域；经与长江及江汉平原西缘各河流的重矿物组合比较发现，宜昌砾石层的稳定重矿物组合特征与现代长江河漫滩和低矮阶地沉积物的重矿物组合一致。综合分析认为宜昌砾石层是于早更新世长江贯通三峡时形成的冲积扇，结合前人对宜昌砾石层形成时代的研究，推断三峡贯通的时间应该在1．0 Ma BP左右。
엄범분포우의창지지강-송자일대적의창력석층，대강한평원내지장강중유적지층화분、지모연화、고배경변천이급장강적형성여연화등연구구유중요의의。본연구재과제조전기연구적기출상，이본구내최구대표성적6개부면위연구대상，대0．125～0．063mm립급분세사질침적물적중광물특정진행료분석，결과현시의창대표성부면력석층세과립분사질침적물적중광물조합기본일치：고석-록렴석-백태석-적갈철광-태철광-자철광。원-회분석표명，중광물조성소지시적원구원암류형제료삼협지구적환유장강삼협이서적금사강、민강、가릉강급오강류역；경여장강급강한평원서연각하류적중광물조합비교발현，의창력석층적은정중광물조합특정여현대장강하만탄화저왜계지침적물적중광물조합일치。종합분석인위의창력석층시우조경신세장강관통삼협시형성적충적선，결합전인대의창력석층형성시대적연구，추단삼협관통적시간응해재1．0 Ma BP좌우。
The Yichang gravel layers distribute largely at the Yichang,Zhijiang and Songzi area,which have important significance for the research of stratigraphic division,geomorphic evolution,ancient environmental changes of the Jianghan Plain and the middle Yangtze River,even formation and evolution of the Yangtze River.Based on previous research of our studying team,a total of six profiles were chosen in this paper.Here,heavy mineral characteristics of very fine sand fraction (63-125μm)was selected from bulk samples were analyzed.The results revealed that heavy mineral assemblages of the fine-grained sediments from the gravel layers are almost the same which meant zircon,epidote,leucoxene,hematite-limonite,ilmenite and magnetite.Relation of the source to sink shows source rock types reflected by heavy mineral assemblages distributed primarily in the Jinshajiang,Minjiang and Wujiang drainage basin,besides Western Three Gorges.Meantime heavy mineral assemblages of the sediments are similar to those of the modern Yangtze and the low-terrace sediments,which is showed by comparison the heavy mineral assemblage with the modern Yangtze and the main rivers in the Jianghan Plain. Based on the comprehensive analysis above,together with the early research on formation age of the Yichang gravel layers,we conclude that the Yichang gravel layers were the alluvial fan formed when the Yangtze River cut through the Three Gorges in the Early Pleistocene,approximately 1 .0Ma BP.