西藏安多县东巧晚侏罗世生物礁的发现

LATE JURASSIC REEFS IN DONGQIAO AREA OF ANDO, XIZANG (TIBET)

首次发现西藏安多县东巧地区晚侏罗世生物礁 ,造礁生物以层孔虫和六射珊瑚为主 ,其中 ,层孔虫可分为枝状、筒状和块状三种类型 ,它们多以原地生长状态保存。礁岩石学特征研究表明 ,礁岩可分为筒状 -枝状层孔虫障积岩、枝状层孔虫障积岩、筒状层孔虫障积岩、筒状 -块状层孔虫障积 -骨架岩和筒状层孔虫 -六射珊瑚障积 -骨架岩。礁体类型可分为筒状 -枝状层孔虫障积岩隆礁、枝状层孔虫障积岩隆礁、筒状层孔虫障积岩隆礁、筒状 -块状层孔虫障积 -骨架岩隆礁和筒状层孔虫 -六射珊瑚障积 -骨架岩隆礁 ,礁体的演化均经历了奠基阶段。

Late Jurassic reefs are firstly discovered in Dongqiao area of Tibet, the reef building organisms are mainly composed of hexacorals and stromatoporoids which comprise dendritic, cylindric and massive forms. They were mostly preserved in place. Five types of microfacies can be distinguished according to the study on petrology of reefs, i.e. cylindric dendritic stromatoporoids bafflestone, dendritic stromatoporoids bafflestone, cylindric stromatoporoids bafflestone, cylindric massive stromatoporoids baffle framestone and cylindric stromatoporoids hexacorals baffle framestone. They formed five types of buildup, namely, cylindric dendritic stromatoporoids baffling buildup, dendritic stromatoporoids baffling buildup, cylindric stromatoporoids baffling buildup, cylindric massive stromatoporoids baffle frame buildup and cylindric stromatoporoids hexacorals baffle frame buildup. They all went through three stages:colonization, development and declination, which reflects the control of sedimentary environment and water energy on reef development.