松辽盆地北部西斜坡青山口组三段四级层序格架内沉积微相分布

摘要

The third member of Qingshankou Formation in the west clinoform of the Songliao Basin was divided into 3 4th-order sequences (Cg2,Cg1,Cg0),each of the 4th-order sequence can be divided into lake expanding system tract and lake shrinking system tract,upwardly,the area of Eg2 is the largest,the area of Sg2 was little smaller,which pinch-out line was located in the western part of the west clinoform;The pinch-out line of Eg1 was located in the middle of the west clinoform,and the area of Sg1 was little smaller than Eg1;The pinch-out line of Eg0 was located in the east of the west clinoform region and pinch-out line of Sg0 further migrated toward east. In the profile section,sand-rich delta front and shore-shallow lacustrine sandy beach-bars mostly developed nearby the 3rd or 4th-order sequence boundary,while the main sedimentary microfacies was the mud-rich shore-shallow lacustrine mixed beach which developed nearby the maximum flooding surfaces of the 4th-order sequence. In the plane,the characteristics of microfacies distribution of different 4th sequences sys-tem tracts has certain inheritance,and has the obvious difference.%松辽盆地西部斜坡青山口组三段划分3个四级层序（Cg2、Cg1、Cg0），每个四级层序均可划分为四级湖泊扩张体系域和四级湖泊收缩体系域，自下而上，Eg2地层分布范围最大，Sg2地层分布范围略小，地层尖灭线位于西斜坡的西部；Eg1地层尖灭线位于西斜坡的中部，Sg1地层分布范围比Eg1略小；Eg0地层尖灭线位于西斜坡的东部，Sg0地层尖灭线进一步东移。剖面上，富砂的三角洲前缘和滨浅湖砂质滩坝在三级和各四级层序界面附近最为发育，而四级层序最大湖泛面附近以富泥的滨浅湖混合滩微相为主。平面上，不同四级层序体系域的沉积微相分布既有一定继承性，又有明显的差异性。