松辽盆地北部上白垩统青山口—姚家组沉积相及层序地层界面特征

青山口组和姚家组形成于盆地演化的坳陷期，此时松辽湖盆北部发育富有特色的大型湖泊三角洲沉积，沿湖盆纵向长轴主要出现三角洲—湖相泥岩充填模式，发育三角洲和湖泊两种沉积相类型。从盆地边缘到盆地中心，沉积相由浅水三角洲逐渐变为湖泊沉积。其中青山口组主要发育滨湖、浅湖、半深湖—深湖沉积亚相；姚家组主要发育三角洲平原、三角洲前缘和前三角洲沉积亚相。岩心观察资料显示，研究区泉头组顶部至姚家组顶部共识别出6个沉积层序，相应有7个沉积层序界面，其中一个同时为超层序界面。层序界面附近主要见古土壤、冲刷面、钙质结核、削截等现象，层序界面之上覆盖鲕粒灰岩、生物屑灰岩，并见虫孔构造、黄铁矿等。

Characteristics of Sedimentary Facies and Sequence Boundary in Upper Cretaceous Qingshankou-Yaojia Formation of Northern Songliao Basin

Qingshankou and Yaojia Formation developed delta and lacustrine facies along the long axis of the basin during the period of depression. Qingshankou Formation consists of littoral lake, shallow lake and semi-deep lake facies. Yaojia Formation consists of delta plain, delta front and prodelta facies. Base on analyses of drilling cores, from the top of Quantou Formation to the top of Yaojia Formation can be divided into 6 sequences, and corresponding to 7 sequence boundaries. One of the sequence boundaries is supersequence boundary. Sequence boundary is characterized by paleosol, erosional surface, calcareous nodules, and truncation. Generally, oolitic limestone, bioclastic limestone, worm boring and pyrite develop above the sequence boundary.