Abstract: Meandering stream is a terminal type of river evolution.The point bar in meandering stream is an important sedimentary unit.Up to now,the meandering stream in intermontane region and its influences seriously on the recognization about stream environments and stream sediments have been known a little.A lot of seasonal intermontane meandering streams were developed in the Hero Hill in the southwestern of Qaidam Basin,a lot of point bar sediments were developed in some places of these streams.These point bar sediments have the shapes like arc and charater picture of "u" and/or "Ω" ,and their largest length and width may amount to one hundred meters and their largest height may be three to four meters and even more.According to their sediments,all the point bars may be divided into five types of whole sand point bar,sand-dominant point bar,gravel-sand mixed point bar,gravel-dominant point bar and whole gravel point bar.The first is much like the point bar developed in the common mean-dering stream.The sedimentary structures are considerably like the common point bars forming more washing surfaces and parallel beddings.The other notable feature is that the point bars in Hero Hill often have aeolian sands and/or talus.Otherwise,the development of point bars is sometimes dominanted by vertical accretion and secondly by lateral accretion.In a word,the point bar of intermontane meandering stream is sometimes similar with the point bar of ordinary meandering in sedimentology, and sometimes it also has quite differences with the latter.

Key words: point bar, meandering stream, intermontane, sedimentology, Qaidam Basin

摘要： 曲流河是一种常见的河流演化的终极型式,曲流河边滩沉积是曲流河的一种重要沉积单元.到目前为止,人们对山间曲流河边滩沉积的认识还很不够,严重地妨碍了人们对河流环境和河流沉积的全面认识.柴达木盆地西南角的英雄岭发育了一系列的季节性山间曲流河.在这些曲流河的某些河段发育了一些边滩沉积,这些边滩沉积形态上总体呈弧形、"u"形或"Ω"形,长宽最大可达近100m,高3～4m.有的以砾石为主,有的以砂为主,可以有少量泥质沉积.根据沉积物性质不同可以将其分为五种类型.沉积构造与一般曲流河边滩沉积相似,但发育有更多的冲刷面和平行层理.其发育演化过程中常伴有风成砂或坡积物发育,有时以垂向加积为主、侧向加积为辅.总之,山间曲流河边滩的沉积学特征有时与一般曲流河边滩相似,有时又与一般曲流河大相径庭.

关键词: 边滩, 曲流河, 山间, 沉积学, 柴达木盆地