贺兰山寒武系研究新进展

New advances in the study of the Cambrian in Helan Mountain

贺兰山寒武系早期苏屿口组为砂、砾混杂和不等粒结构的水下冲积扇沉积;五道塘组为下古生界碳酸盐台地沉积,其下部为含泥中、细粒砂屑和生物碎屑,中、上部为含不同形态的核形石碳酸盐岩组成;陶思沟组为发育水下流动波痕和水上暴露泥裂构造碳酸盐岩与细碎屑岩系的混合沉积;胡鲁斯台组和阿不切亥组为陆表海与"风暴海"沉积。根据该区与华北地台的对比,首次提出贺兰山寒武纪早期的苏屿口组古地理面貌应是西低东高,而非传统认为的西高东低;寒武纪早期的五道塘组、陶思沟组古地理面貌则为西高东低。

The early Cambrian Suyukou Formation of the Helan Mountain is formed of the alluvial fan deposit including mixed sands and gravels with unequigranular texture, the Wudaotang Formation is com- posed of lower Paleozoic carbonatite plateau deposit, the lower part of which is formed of middle-fine grained sand cuttings and bioclasts, and the middle and upper part are formed of carbonatite of oncolites with different forms, the Taosi Formation is composed of mixed sedimentation including carbonate rocks and fine-grained clastic rocks with developed underwater flowing rippling and exposured mud cracking structures. The Hulusitai Formation and Abuqiehai Formation are epeiric sea and ＂storm ocean＂ sedimen- tation. By contrasting the Helan Mountain with the North China platform, it is concluded that the palaeogeography feature of the early Cambrian Suyukou Formation was shown as lower in the west and higher in the east, but not higher in the west and lower in the east as traditionally considered, where as the Wudaotang Formation and Taosigou Formation were shown as higher in the west and lower in the east.