塔里木盆地柯坪地区中下奥陶统碳酸盐岩露头层序地层学研究

Study on Outcrop Sequence Stratigraphy of the Lower-Middle Ordovician Strata in Keping Tarim Basin

在前人岩石地层、生物地层、年代地层研究基础上 ,作者运用层序地层学理论结合沉积微相分析 ,对柯坪地区中下奥陶统露头碳酸盐岩进行了层序地层解剖。研究区共识别出二种界面类型 (暴露层序不整合界面和淹没层序不整合界面 )、三种准层序组构特征 (潮坪、浅滩和滩下陆棚 )和两种主要类型的体系域构成 (海侵体系域和高位体系域 ) ,在此基础上把该套碳酸盐岩划分为 7个三级层序 ,其中Sq1～ 2对应于蓬莱坝组地层、Sq3～ 6对应于鹰山组地层和Sq7对应于大湾沟组地层。Sq1～ 2三级层序由潮坪旋回的藻纹层白云岩、细粉晶白云岩和灰岩组成 ;Sq3～ 4三级层序由潮坪旋回的藻纹层灰岩和颗粒灰岩组成 ;Sq5～ 6三级层序由潮下浅滩相旋回的颗粒灰岩组成 ;

Based on pioneer studies of lithostratigraphy, biostratigraphy and chronostratigraphy, authors analysed sequence stratigraphy and sedimentary microfacies of the Lower Middle Ordovician. Two sorts of sequence surfaces are discerned exposing sequence unconformities and drowing sequence unconformities. Three kinds of parasequence moulds are summaried as the tidal flat parasequences, the shoal parasequences and the shelf parasequences. Two main types of system tracts are formed by stacking patterns of parasequences transgressive systems tract and highstand systems tract. Based on these studies, Lower Middle Ordovician strata can be divided into 7 three grade sequences. Among these, The Sq1 2 three grade sequences are comparable with Penglaiba formation, the Sq3 6 three grade sequences are comparable with Yingshan formation and the Sq7 three grade sequence are comparable with Dwangou formation. The Sq1 2 three grade sequences are composed of penecontemporeous dolostones and carbonates tidal flat cycles , and the Sq3 6 three grade sequences are composed of tidal flat cycles and shoal cycles and the Sq7three grade sequences are composed of shelf facies carbonates.