辫状河道是一种平原河流地貌,其主要成因为分叉型河床导致,河床因心滩、沙洲造成河床分叉,宽窄相同,形似发辫,所以称为辫状河道。 辫状河道多发育在山区或河流上游河段以及冲积扇上。多河道、多次分叉和汇聚构成辫状。河道宽而浅,弯曲度小,其宽/深比值>40,弯度指数<15,河道砂坝(心滩)发育。河流坡降大,河道不固定,迁移迅速,故又称为“游荡性河道”。 由于河流经常改道,河道砂坝位置不固定,故天然堤和河漫滩不发育。由于坡降大,沉积物搬运量大,并以底负载搬运型式为主。
储集砂体的分布和发育程度主要受辫状河道和水下辫状水道微相的控制。
The distributing of the reservoirs is mainly controlled by the sedimentary microfacies of braided channel and underwater braided channel.
辫状三角洲体系的平原相基本上由辫状河道沉积组成,三角洲前缘及前三角洲相带则以快速堆积、滑塌及浊流沉积为主。
Braid delta systems mainly consist of braid river deposits in delta plain facies, rapid accumulation deposits, slump deposits and turbidites in delta front and prodelta facies.
下段为辫状河沉积,发育良好的砂体、富含有机质,它是本区重要的找矿目标层,产底河道型砂岩铀矿化。
The Lower Member of braided system is the most important target bed enriched in organic matter where basal-channel-type uranium mineralization occurs.
应用推荐