【摘要】 寒武纪早期的苏峪口组是贺兰山地区地质历史重要转换时期的地质单位,长期被认为是近岸海滩沉积。通过3年来对苏峪口组的研究,新识别了苏峪口组沉积环境为一个水下冲积扇,在岩性、岩相、生物群等方面都有新的发现和新的认识。水下冲积扇以冲刷面为底,砾石成分比较复杂,具砾砂混杂、不等粒结构,内部发育递变层理,具重力流的沉积特征。全区辉绿岩脉锆石年龄集中在5.3～5.4Ma,是开裂盆地早期出现的标志年龄,说明开裂盆地的出现是造成苏峪口组早中期水下冲积扇发育的主要原因。更多还原

【Abstract】 As one of the significant geological units in the Helan Mountain area,the Suyukou Formation has long been considered to be of the coastal beach facies.In this study,lithology,facies,biota and other new findings show that it was deposited in the alluvial fan facies.An erosion surface is located in the base of the alluvial fan,which is characterized by complex gravel,heterogranular texture,graded bedding,and turbidity current.Zircon dating of diabase yielded ages of 530~540 Ma,suggesting an early cracking basin,which probably resulted in the formation of the alluvial fan in the Suyukou Formation.更多还原