黔北道真巴渔剖面五峰组—龙马溪组页岩地质特征

Geological characteristics of shale in Wufeng-Longmaxi Formation of Bayu outcrop in Daozhen,northern Guizhou

黔北地区道真巴渔剖面上奥陶统五峰组—下志留统龙马溪组一段地层出露较好,地层界限清晰完整。受全球海平面变化的控制,该剖面五峰组—龙马溪组一段自下而上发育含黏土硅质页岩、硅质页岩、含黏土硅质页岩、黏土质页岩和粉砂质页岩,与盆缘彭水地区和盆内焦石坝具有相似的纵向叠置特征。巴渔剖面五峰组—龙马溪组一段优质页岩岩性主要是含黏土硅质页岩、硅质页岩,具有与盆缘彭水地区和盆内焦石坝地区较为一致的有机质富集规律,TOC(总有机碳含量)与石英矿物含量呈正相关关系,与黏土矿物含量呈负相关关系。巴渔剖面五峰组—龙马溪组一段优质页岩总厚度26.1 m,低于盆缘彭水地区和盆内焦石坝地区,反映道真地区在上奥陶统五峰组—下志留统龙马溪组沉积时期沉积水体深度相对较浅。

The upper Ordovician Wufeng Formation and the first member of the lower Silurian Longmaxi Formation are well exposed in Bayu outcrop Daozhen,northern Guizhou,with clear and complete stratigraphic boundaries.Under the control of global sea level changes,the Wufeng Formation and the first member of the Longmaxi Formation develop clay-bearing siliceous shale,siliceous shale,clay-bearing siliceous shale,argillaceous shale and silty shale from bottom to top,which display similar longitudinal superimposition characteristics to the Pengshui area on the edge of the Sichuan Basin and Jiaoshiba area in the basin.Lithology of the organic-rich shale in Wufeng Formation and the first member of the Longmaxi Formation in Bayu outcrop of Daozhen is dominated by clay-bearing siliceous shale and siliceous shale,which have the same organic matter enrichment features as that in the Pengshui and Jiaoshiba area.Specifically,TOC is positively correlated with the content of quartz,and negatively correlated with the content of clay minerals.The total thickness of organic-rich shale in the Wufeng Formation and the first member of the Longmaxi Formation at this profile is 26.1 m,which is lower than that in the Pengshui and the Jiaoshiba area,reflecting a relatively shallow-water depositional environment in the Daozhen area.