川西地区震旦纪地层新发现

NEW DISCOVERY OF THE SINIAN STRATA IN WESTERN SICHUAN

川西绵竹清平地区震旦纪地层齐全,出露有震旦系陡山沱组和灯影组,灯影组包含灯一段至灯四段的全部地层。陡山沱组为一套滨岸至浅水陆棚相砂泥岩夹浊流相白云岩。灯一段和灯二段为大套典型的局限台地相凝块白云岩、藻纹层白云岩和叠层石白云岩,富含葡萄状、花边状构造,残余厚度500~600m;灯三段为一套灰黑色页岩夹黑色硅质岩,夹少量薄层白云岩,残余厚度12~88m;灯四段主要为一套浅灰色、灰白色厚层凝块白云岩、藻纹层白云岩,夹少量砂质白云岩,含黑色和白色硅质条带,残余厚度115~869 m,沉积相为典型的局限台地相。

It is found that the Sinian strata in Qingping area of Mianzhu,western Sichuan is complete,including the Doushantuo and Dengying formations.The Dengying Formation includes four members from the Dengying 1 to Dengying 4.Doushantuo Formation is a sequence deposited in the shore-to-shallow shelf facies,consisting of sandstone,mudstone mixed with dolostone.The Dengying 1 and Dengying 2 members are characterized by the clotted dolostone,algal dolostone and stromatolitic dolostone deposited in a large set of typical restricted platform facies,which are rich in grape-like and lace-like structures with a thickness of 500-600 m.The Dengying 3 Member is a set of the gray-black shale mixed with black siliceous rocks and thin-bedded dolostone,with a thickness of 12-88 m.The Dengying 4 Member is mainly a set of grayish light gray,grayish white thick-layered clotted dolostone and algal dolostone,with a small amount of sandy dolostone and black and white siliceous bands,with a thickness of 115-869 m,suggesting a typical limited platform facies.