黔中三叠纪地层研究新进展

Sedimentary characteristics and environments of the strata near the Ordovician Silurian boundary in Liangshan,Nanzheng

通过对黔中地区区域地质调查，在二叠系—三叠系过渡层中发现了一系列的韵律层，并通过岩性岩相、矿物学、地球化学和地层古生物学研究，认为过渡层中韵律层是远源火山碎屑重力流沉积产物，并据古生物、沉积学、地层学研究将过渡层归属于三叠系。原安顺组下部“大汪段”之上、下发现大量牙形刺化石，根据岩性及古生物特征，将“大汪段”归入大冶组。黔中—黔南中三叠统陆源碎屑体系的物源来自江南古陆；菊石、双壳类化石层是浊流作用形成的事件沉积层。

The Upper Ordovician contains rich stenohaline organic fossils of marine facies in Liangshan,Nanzheng County of Shaanxi Province,dominated by nekton.Benthos are comparatively rare.The graptolite Diplograptus bohemicus, small sized and thin shelled brachiopods and Dalmanitina ,being good at swimming,are contained,There is hummocky cross bedding in the fine sandstone,indicating a deepwater continental shelf sedimentary environment.The Lower Silurian rocks contain large members of pelagic graptolites and Glyptograptus lungmaensis. No benthos were found.The base of the Silurian is interbedded with radiolarian silicolites.The strata are stable transversely,indicating a transitional sedimentary environment between deepwarter continental shelf and continental slope.