巍峨的贺兰山挺拔于腾格里沙漠和宁夏黄河灌区平原之间,呈北北东向延伸,构成东部黄河灌区平原的天然屏障.习惯上,把它分为三段:三关以南称南段;三关至大武,称中段;大武以北称北段(图1).贺兰山自早寒武世中期(沧浪铺期)沦入海底后,一直属于华北—东北南部陆棚浅海沉积区的一部分.昔日认为此地缺失晚寒武世沉积的观念,现已被越来越多的新资料证明 Towering between the Tengger Desert and the plain of the Yellow River Irrigation District in Ningxia, the towering Mt. Helan stretches north-eastward and forms the natural barrier of the Yellow River Irrigation Plain in the east. It has been customary to divide it into three sections: south of San Guan, ; From the third to the big wu, called the middle section; north of the big wu called the north section (Figure 1) .Helan Mountain since the early Middle Cambrian (Canglang pavement) into the sea, has belonged to the north China - northeastern continental shelf shallow marine sediments Partially, the notion that late-Cambrian sediments were missing here has been confirmed by more and more new data