松辽盆地晚中生代裂谷作用与伸展构造样式

松辽盆地中西部的裂谷作用自下白垩统沙河子组沉积期持续到营城组沉积期,东部从下白垩统沙河子组沉积期持续到登娄库组沉积期.在不同构造层次形成了变形特征有别的构造,中浅层伸展构造的基本要素是断陷盆地边界主断裂,基本结构单元是半地堑和半地垒,横向上呈多米诺型垒-堑构造.主断裂中东倾者倾角缓但向东有增大的趋势;西倾者数量有限但倾角较陡.断陷包括水平拉张量大而裂谷期沉降量小的半地堑和水平拉张量小但裂谷期最大沉降的半地堑.这些断陷盆地在北北东方向呈串珠状,自西而东成带.在中-下地壳发生韧性变形,形成一向东倾拆离带,深度范围15～30km. 裂谷的扩展有3种方式,即边界断裂的斜向后退扩展,断陷带的走向式扩展,断陷群的横向扩展.

LATE MESOZOIC RIFTING AND EXTEN- SIONAL STRUCTURAL PATTERN IN SONGLIAO BASIN. XJPG,

Rifting from sedimentary period Shahezi formation (K1) to sedimentary period Yingcheng formation(K1 ) in the central and western part of Songliao basin and from that of Shahezi formation(K1) to Denglouku formation (K1) in the eastern part formed various structures of different deformation features . The key element of tensional structure at moderate to shallow burial is the major fault at the margin of fault-depression basin, and the essential component half-graben and half-horst, these structures appear as Domino-type horst-graben on side view. The major faults dipping east are gentle but tend to steepen eastwards, while the dipping west is steep but limited. Fault-depression included two types of half-grabens, one with big horizontal pull-apart distance and small subsidence, the other with just the opposite. These fault-depression basins of beaded type in NNE direction band from east to west. Tough deformation in the mid-lower crust formed a detachment zone dipping east with depth of 15~30 km. There existed three ways for rifting propagation: oblique back-propagation of boundary fault, strike propagation of fault-depression zone and lateral propagation of fault-depression group.