【摘要】 利用实地考察、浅钻孔、探槽及卫星影像等方法,对鄱阳湖信江决口三角洲进行了系统研究。该决口三角洲是洪水冲破信江西岸天然堤流入附近的河漫湖泊形成的,其平面形态为鸟足状,总体延伸方向与主河道近垂直。在横切剖面上整个决口三角洲沉积体呈透镜状覆盖在早期的湿地或河漫湖泊沉积之上。鄱阳湖信江决口三角洲可分为3个亚相:决口三角洲平原、决口三角洲前缘和决口前三角洲。决口三角洲平原主要发育决口河道、决口天然堤、废弃决口河道和湿地,其中决口河道又可以进一步划分为决口水道、边滩、汊口滩;决口三角洲前缘主要发育河口坝、支流间湾。河漫湖泊规模小、深度浅、波浪能量弱,对河口坝和决口河道砂体的改造较弱,不易形成连片分布的席状砂;决口前三角洲不发育。决口三角洲沉积受河流作用和河漫湖泊作用的共同控制,其演化可以划分为主河道天然堤生长阶段、决口初期阶段、进积分汊阶段及分汊—废弃阶段4个阶段。更多还原

【Abstract】 Based on field investigation,shallow boreholes,exploration trench and google earth,the crevasse delta of Xinjiang River in Poyang Lake area,Jiangxi Province is studied in detail. The crevasse delta is formed when flood breaches the natural levee on west bank of the Xinjiang River and flows into the flood lake nearby. The delta is bird-foot shape in the plane,and is distributed overall perpendicular to the main channel trend of the Xinjiang River. In the transverse profile,the depositional body of the crevasse delta is lenticular in the lateral,and overlies the previous deposits of wetlands or flood lake. The crevasse delta can be divided into three subfacies,i.e. crevasse delta plain,crevasse delta front and crevasseprodelta. On the delta plain,there are crevasse channels,natural levees,abandoned crevasse channels, and wetlands. Crevasse channels can be further divided into waterways,point bars and branch mouth bars. On the delta front,mouth bars and inter-distributary bays are developed. Sheet sand is not developed,because the flood lake is small in scale and wave energy is not high enough to create longshore current to modify mouth bar and crevasse channel sand bodies. The depositional characteristics of the crevasse delta are controlled jointly by fluvial and flood lake process. The evolution model of the crevasse delta can be divided into four stages: Main channel natural levee growth stage,early crevasse stage,prorogation and channel branching stage,channel branching and abandoning stage.更多还原