库车坳陷古近系原型沉积盆地层序地层格架及沉积演化

Sequence stratigraphic framework and sedimentary evolution of Paleogene prototype sedimentary basin in Kuqa Depression

基于库车坳陷大北—克深地区古近系原型沉积盆地地层沉积相精细研究结果,将古近系库姆格列木群划分为5个岩性段,苏维依组划分为3个岩性段。研究认为库姆格列木群砂砾岩段为扇三角洲沉积,膏泥岩段为局限泻湖沉积,白云岩段为局限泻湖—潮坪沉积,膏盐岩段为半局限泻湖—强蒸发膏盐湖沉积,泥岩段为滨浅湖沉积;按照层序地层学基本原理和五级层序划分方案对库车坳陷中东部古近系原型沉积盆地进行研究并建立了层序发育演化实体模型,研究认为该原型沉积盆地可以划分为两个二级超层序和3个三级层序,古近纪海侵是从大北—克深地区的河流下切谷开始的,3个三级层序均为海侵体系域和高位体系域旋回组合层序,海侵—高位体系域之间的转换界面发育最大或次级海泛面。

Based on the research results of stratigraphic sedimentary facies of Paleogene prototype sedimentary basin in Dabei-Keshen area of Kuqa Depression,the Paleogene Kumglimu Group is divided into five lithologic member,Suweiyi Formation is divided into three lithologic member.It is considered that the sand-conglomerate member of the Kumglimu Group is fan delta deposit,the gypsum-mudstone member is limited lagoon deposit,the dolomite member is limited lagoon-tidal flat deposit,the gypsum salt member is a semi confined lagoon-strong evaporite gypsum salt lake deposit,and the mudstone member is shore-shallow lake deposit.According to sequence stratigraphy and five-level sequence division scheme,the Paleogene prototype sedimentary basin in the central and eastern part of Kuqa Depression is studied,and the entity model of sequence development and evolution is established.It is considered that the prototype sedimentary basin can be divided into two second-level supersequence and three third-level sequence.The Paleogene transgression started from the lower cut valley of rivers in the Dabei-Keshen area.The three third-order sequences are composed of transgressive system tract and highstand system tract cycles,the transition interface between transgressive and highstand system tracts develops the maximum or secondary marine(or lake)-flooding surface.