贵州瓮安磷矿上震旦统陡山沱组地层和沉积环境

瓮安磷矿当时位于川黔滇台地东南边缘，是我国晚震旦世陡山沱期主要的磷矿之一。该区陡山沱组含磷地层中发现大量低等蓝藻和真菌、红藻、大型球状绿藻、疑源类及可能的后生动物化石，引起国内外地质学家和古生物学家的关注，尤其是最近报道从该地层中发现具细胞结构的海绵和动物胚胎化石，震动了各国古生物学界。瓮安磷矿的陡山沱组不整合于南沱组或板溪群之上，为灯影组浅灰白色白云岩层整合覆盖，以中部的古喀斯特侵蚀面为界而分为下、上两个岩性段，构成下段的白云岩—磷块岩—白云岩序列和上段的磷块岩—白云质生屑磷块岩—磷质白云岩序列。化石产于陡山沱组上段。

Stratigraphy and Sedimentary Environment of the Upper Sinian Doushantuo Formation in Weng'an Phosphorite Deposit,Guizhou Province

The Upper Sinian Doushantuo Formation in Weng'an Phosphorite Deposit,Guizhou Province,which conformably underlies the Upper Sinian Dengying Formation and disconformably overlies the Lower Sinian Nantuo Tilites or Presinian Qingshuijiang Formation of Banxi Group,is subdivided into two parts separated by a sedimentary break.The lower part is characterized by dolostones—phosphorites (Ore bed A)—dolostones.The upper part (Ore bed B) containing abundant large,morphologically complex acritarchs,metaphyte and metazoans is dominated by intraclastic phosphorites,algal phosphorites,hardground phosphorites and phosphorous dolostones.The sedimentary successions of the Doushantuo Formation change obviously in Weng'an Phosphorite Deposit area,the Ore bed A,for example,occurs only in Datang,and changes into dolostones and siliceous rocks in Yuhua and Mofang,respectively.The Doushantuo Formation in Weng'an Phosphorite Deposit was deposited on the southeastern margin of Sichuan Guizhou Yunnan Platform,the local terrain controlling the distribution of sedimentary facies.