贺兰山寒武纪早期苏峪口组水下冲积扇的发现及意义  

The discovery of alluvial fan in the Early Cambrian Suyukou Formation of the Helan Mountain and its geological implications

作　　者：蔡雄飞[1] 何文键 杨捷[1] 曾佐勋[1] 顾延生[1] 刘伟[1] 

机构地区：[1]中国地质大学地球科学学院,生物地质与环境地质教育部重点实验室,湖北武汉430074 [2]核工业地质局二九二大队,广东河源517000

出　　处：《岩石矿物学杂志》2013年第2期197-206,共10页Acta Petrologica et Mineralogica

基　　金：中国地质调查局地调项目(1212011120552)

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。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.

关 键 词：水下冲积扇 沉积环境 构造背景 苏峪口组 贺兰山 

分 类 号：P512.2[天文地球—地质学] P588.21