松辽盆地南部白垩纪-古近纪挤压构造的发现与盆地性质探讨

Discovery of the Cretaceous-Paleogene compressional structure and basin properties of the southern Songliao Basin

松辽盆地位于欧亚板块东部,毗邻太平洋板块,是叠置于华北板块和西伯利亚板块之间的晚古生代碰撞造山带之上规模最大的中-新生代陆相含油气盆地,具有断、坳双重结构。自白垩纪以来,松辽盆地南部主要经历两期挤压作用:NW-SE向挤压作用发生在下白垩统营城组碎屑岩段-上白垩统泉头组沉积时期,挤压作用持续了18Myr;近E-W向挤压作用发生在四方台组-古近系沉积时期,挤压作用至少持续了39.1Myr。两期挤压作用都表现出东强西弱的特点,第二期挤压作用的变形强度远大于第一期,并且在明水组沉积晚期变形强度最大,这期挤压作用奠定了松辽盆地现今的构造格局。下白垩统营城组上部碎屑岩段-上白垩统泉头组和四方台组-古近系的沉积作用分别记录了第一期、第二期挤压作用形成的反转构造和断层相关褶皱的变形过程。上述构造在不同时期隆升速率与沉积速率之间的关系,控制了盆地的沉积范围、沉积地层的厚度和接触关系在空间上的变化。松辽盆地在上述两个构造演化阶段都处于活动大陆边缘的陆内区域,盆地性质都应属于陆内挤压坳陷盆地。

The Songliao Basin is located in the eastern part of the Eurasian Plate and adjacent to the Pacific Plate.It is the largest Mesozoic-Cenozoic continental petroliferous basin which superimposed on the Late Paleozoic orogenic belt between the North China Plate and the Siberian Plate.Since the Cretaceous,the southern Songliao Basin has experienced two phases of compression:the NWSE trending compression occurred during the sedimentary period of the Lower Cretaceous Yingcheng Formation-Upper Cretaceous Quantou Formation,and the compression continued for 18 Myr;the near E-W trending compression occurred during the sedimentary period of the Sifangtai Formation to the Paleogene,and the compression continued for at least 39.1 Myr.Both phases of compression show the characteristics of strong east and weak west.The deformation intensity of the second stage of compression is much greater than that of the first stage,and it is the largest in the late sedimentary stage of the Mingshui Formation.The second stage of compression has established the current structural pattern of the Songliao Basin.The sedimentary processes of the upper clastic rocks of the Lower Cretaceous Yingcheng Formation-the Upper Cretaceous Quantou Formation and the Sifangtai Formation-Paleogene recorded the deformation processes of the inversion structures and fault-related folds which formed by the first and second phases of compression,respectively.Relationship between the uplift rate and the deposition rate of the above-mentioned structures in different periods controlled the spatial variation of the basin’s sedimentary range,stratum thickness and stratigraphic contact relations.The Songliao Basin is located in the intracontinental area of active continental margin during the above two structural evolution stages,and the properties of the basin should belong to the intracontinental compression-depression basins.