北祁连东段早石炭世前黑山期岩相古地理主要特征

Characteristics of lithofacies and paleogeography of the Early Carboniferous Qianheishan age in eastern part of Northern Qilian Mt.

本区地处北祁连加里东褶皱带东部,早石炭世前黑山期区内为海湾性质的陆表海域。前黑山中期,秦岭海水第一次侵入本区,形成海湾并逐步扩大、超覆,形成了以障壁海岸环境为主的由碎屑岩、页岩以及灰岩组成的海陆交互相的沉积岩系。相区由三角洲平原相和滨海平原相组成。前黑山组中段含有石膏层,在中国的早石炭世沉积中很具特色。基底断裂活动造成了本区沉积基底块断式差异沉降作用,因此,本区各地段的岩相古地理特征均差异很大。

The Qianheishan Formation is equal to Tournaisian.During the middle Qian- heishan time,the marine water for the first fime invaded the eastern part of Northern Qilian Mt.forming a gulf and then the invasion became progressively. A sedimentary rock system of alternative marine-continental facies was formed in a barrier coast environment.This rock system consists mainly of clastic rocks,shale and limestones.The facies realm was made up of delta and seashore.The middle part of the Early Caboniferous Qianheishan Formation contains gypsum,a typical sedimentary fea- ture in the Early Carboniferous of China.Owing to the basement fault resulting in the subsidence of the sedimentary basement with a block difference,there are great differ- ences in the lithofacies and paleogeographic features among all sectors of this area.