松辽盆地嫩江组层序构型及其沉积演化

松辽盆地上白垩统嫩江组是第二个湖泛期形成的一套退积-进积型地层，根据发育的构造不整合、沉积不整合、湖泛面及水退面等11个层序界面的发育特征，将嫩江组划分为1个二级层序、2个三级层序和10个四级层序，在四级层序格架内恢复了沉积充填演化史。嫩江组一段沉积时期是盆地第二次湖侵期，随着湖盆水域不断扩大，在地层顶部形成SB07最大湖泛面，由此形成了嫩江组一段以低角度退积型三角洲沉积为特征的退积型层序，同时在三角洲前缘发育大型的浊积水道及浊积扇。嫩江组二段到五段沉积时期，由于盆地东部抬升，形成了一系列由东向西高角度进积型三角洲为沉积特征的进积型层序，同时由于三角洲前缘斜坡发生滑塌, 在其前部湖相区形成一系列呈南北向排列的滑塌浊积扇体。退积型与进积型层序控制的沉积体系区别是物源方向发生了90°转变，而进积型层序结构及沉积特征也表明嫩江组二段底部油页岩是在湖盆萎缩过程中逐渐形成的，不是在最大湖泛期由于海水侵入形成的。

Sequence Configuration and Sedimentary Evolution of Nenjiang Formation in the Songliao Basin

In the Upper Cretaceous, Nenjiang Formation have been formed a progradation-retrogradation type stratigraphy in the second lacustrine flooding Period, according to the tectonic unconformity, sedimentary unconformity, lake flooding surface and regressive surface and so on, which totals eleven sequence boundaries, the Nenjiang Formation was divided into one second order sequence, two third-order sequences and ten fouth-order sequences, restored the sedimentary filling evolution histories in the fourth-order sequence stratigraphic framework. During the first member of the Nenjiang Formation deposition, the SB07 the maximum flooding surface was formed on the top of strata, which resulted in the retrogradation sequence has the characteristic of low-angle retrogradation delta sediment with the lake level constantly rise, meanwhile the large scale turbidite channels and turbidite fans are observed in the delta front. By uplifting the basin during the second-order and fifth-order member of Nenjiang Formation deposition, developed a series east to west into the area of high-angel delta is characterized by the deposition of retrograding sequences, because of the slumping in the delta front slopes, the forepart of lacustrine zone discovered a series of slump turbidite fan bodies. Retrograding sequences usually incurred the direction 90o change of the deposition material source, its the mainly difference compare with progradation sequence, whereas the structure of progradation sequence and sedimentary characteristics indicated that the oil shale (at the bottom of the Nenjing second member) is  formed  in the process of shrinking lake, not in maximum lake flooding through to the sea invasion.