THE DEEP FAULT DEPRESSIONS AND THEIR GENESIS ON THE EAST OF DAQING PLACANTICLINE IN SONGLIAO BASIN

The extensional fault-depressions occurring broadly on the east of Daqing placanticline are the advantageous areas for natural gas exploration in the deep-layer of northern Songliao Basin. The fault-depressions are characterized by half-graben basins. From Late Jurassic to Early Cretaceous, the depression-controlling faults experienced the developing processes from independence, interaction to the unification. The deep fault-depressions in northern Songliao Basin went through three developing stages, i.e. the initial faulting stage in Huoshiling Period, the strong downfaulting stage in Shahezi Period, and the fault-depression depauperization stage in Yingcheng Period. The fault-depressions also underwent several compressive tectonic activities. The extensional structures provide excellent traps for oi1 and gas accumulations in the Songliao Basin.