THE FRAMEWORK OF SEQUENCE STRATIGRAPHY IN THE SHIWU FAULT DEPRESSION OF THE SONGLIAO BASIN

The Shiwu Fault Depression is the one with faults in the west and overlap in the east in the Songliao Basin.Based on synthetic study of core,drilling and logging data,three super sequences and six third-order sequences were identified and several types of sedimentary facies were recognized in the depre-ssion.Among these sedimentary facies,alluvial fan and fan delta were deposited in the step slope in the west of the depression,braided river delta and turbidity fans in the ramp of the southeast,and half-deep and deep lake in the middle sag.It was indicated that the Shiwu Fault Depression underwent three times of lake transgression.The evolution of the sequences can be summarized as early formation stage,continuously developing stage and well developed stage.