摘要
广西南部小董板城一带广泛出露硅质岩地层,这些硅质岩形成于盆地相,由于缺乏足够的化石证据,其地质时代曾被不同的地质工作者定为晚泥盆世、石炭纪或早二叠世。1990年,笔者等为了确定这些地层年代,重新研究了这一地区的硅质岩地层,结果发现了比较丰富的牙形刺化石,如:Palmatolepis tenupunctata, Pa.minuta, Pa.subperlobata, Pa. glabra pectinata, Pa.glabra distorta, Pa. perlobata, Pa. gracilis sigmodalis, Palmatodella delicatula,Falcodus variabilis, Polygnathus sp., Pseudopolygnathus triangulus triangulus,Scaliognathus anchoralis, Siphonodella sp. 等。根据这些牙形刺,作者认为上述硅质岩地层时代属于晚泥盆世法门期至早石炭世杜内期。上二叠统底部砾岩在这一地区的不同地点不仅直接不整合在晚泥盆世地层之上,而且不整合在早石炭世地层之上。
The siliceous rocks which are developed in the basin facies are widely distributed in Xiaodong area in the south Guangxi.Because of undiscovered fossils,their ages have been defined to the Late Devonian,the Carboniferous or the Early Permian in age by some geol-ogists.In order to define the age of the siliceous rock strata, the writers restudied the siliceous rocks in this area and found abundant conodonts such as Palmatolepis tenupunctata, Pa. minuta. Pa. subperlobata, Pa. glabra pectinate, Pa. glabra distorta, Pa. perlobata, pa. gracilis sigmodalis, Palmatodella delicatula, Falcodus variabilis, Polygnathus sp., Pseudopolygnathus triangulus triangulus, Scaliognathus anchoralis,Siphonodella sp. and so on. Based on these conodonts,the authors belive that th age of the siliceous rocks can be recognized as from Late Devonian (Faminnian) to Early Carboniferous (Toumaisian). The Upper Permian basal conglomerata strata cover unconformably not only on the Upper Devonian strata but also on the Lower Carboniferous strata in this area.
